SEC Form 424B4 filed by Aptevo Therapeutics Inc.

Filed Pursuant to Rule 424(b)(5)

Registration No. 333-284969

PROSPECTUS SUPPLEMENT

(to the Prospectus dated February 14, 2025)

APTEVO THERAPEUTICS INC.

1,764,710 Shares of Common Stock

We are offering directly to investors 1,764,710 shares of our common stock, $0.001 par value per share (“common stock”), in a registered direct offering pursuant to this prospectus supplement and the accompanying prospectus and a securities purchase agreement with such investors. In a concurrent private placement, we are selling to such investors common warrants to purchase up to 3,529,420 shares of our common stock (the “Common Warrants”). Each share of common stock is being offered together with two Common Warrants, each to purchase one share of common stock. The combined purchase price is $1.19 per share and accompanying Common Warrants. The Common Warrants and the shares of our common stock issuable upon the exercise of the Common Warrants are being offered pursuant to the exemption provided in Section 4(a)(2) under the Securities Act of 1933, as amended (“Securities Act”), and/or Regulation D promulgated thereunder, and they are not being offered pursuant to this prospectus supplement and the accompanying prospectus.

The shares of common stock and the Common Warrants will be separately issued. The Common Warrants will not be exercisable prior to our stockholders approving the terms of the Common Warrants at a meeting of stockholders (the “Stockholder Approval”) as may be required by the applicable rules and regulations of the Nasdaq Capital Market (or any successor entity) to permit the exercise of the Common Warrants. The Common Warrants will expire five years from the date of Stockholder Approval and have an initial exercise price of $1.19. In the event that we are unable to obtain the required Stockholder Approval, the Common Warrants will not be exercisable and therefore have no value.

Our common stock is listed on the Nasdaq Capital Market under the symbol “APVO.” On April 3, 2025, the last reported sale price of our common stock on the Nasdaq Capital Market was $1.99 per share. The Common Warrants being issued in the concurrent private placement are not listed on any securities exchange, and we do not expect to list the Common Warrants on any securities exchange. There is no established public trading market for the Common Warrants, and we do not expect a market to develop. Without an active trading market, the liquidity of the Common Warrants will be limited.

We have engaged Roth Capital Partners, LLC to act as exclusive placement agent in connection with this offering. The placement agent is not purchasing or selling any securities offered by this prospectus supplement and the accompanying base prospectus. See “Plan of Distribution” beginning on page S-18 of this prospectus supplement for more information regarding these arrangements.

As of April 3, 2025, the aggregate market value of the voting common equity held by non-affiliates, computed by reference to the price at which the common equity was last sold on February 3, 2025, was $6.3 million, based on 1,458,504 shares of outstanding common stock as of such date, of which 1,458,341 shares were held by non-affiliates. Pursuant to General Instruction I.B.6 of Form S-3, in no event will we sell securities in a public primary offering with a value exceeding more than one-third of our public float in any 12-month period so long as our public float remains below $75.0 million. During the 12 calendar months prior to and including the date of this prospectus, we have sold $2.1 million of securities pursuant to General Instruction I.B.6 of Form S-3.

Investing in our securities involves a high degree of risk. Before making an investment decision, you should carefully review and consider all of the information set forth in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein, including the risks and uncertainties described under “Risk Factors” beginning on page S-9 of this prospectus supplement and the risk factors incorporated by reference into this prospectus supplement and the accompanying prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Delivery of the shares of common stock and Common Warrants to the investors is expected to be made on or about April 4, 2025, subject to customary closing conditions.

Roth Capital Partners

The date of this prospectus supplement is April 3, 2025.

Table of Contents

ABOUT THIS PROSPECTUS SUPPLEMENT

This prospectus supplement and the accompanying base prospectus are part of a registration statement that we filed with the Securities and Exchange Commission (the “SEC”) utilizing a “shelf” registration process. Each time we conduct an offering to sell securities under the accompanying base prospectus we will provide a prospectus supplement that will contain specific information about the terms of that offering, including the price, the amount of securities being offered and the plan of distribution. The shelf registration statement was initially filed with the SEC on February 14, 2025 and was declared effective by the SEC on February 26, 2025. This prospectus supplement describes the specific details regarding this offering and may add, update or change information contained in the accompanying base prospectus. The accompanying base prospectus provides general information about us and our securities, some of which, such as the section entitled “Plan of Distribution,” may not apply to this offering. This prospectus supplement and the accompanying base prospectus are an offer to sell only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. We are not making offers to sell or solicitations to buy our common stock in any jurisdiction in which an offer or solicitation is not authorized or in which the person making that offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make an offer or solicitation.

If information in this prospectus supplement is inconsistent with the accompanying base prospectus or the information incorporated by reference with an earlier date, you should rely on this prospectus supplement. This prospectus supplement, together with the base prospectus, the documents incorporated by reference into this prospectus supplement and the accompanying base prospectus and any free writing prospectus we have authorized for use in connection with this offering include all material information relating to this offering. We have not, and the placement agent has not, authorized anyone to provide you with different or additional information and you must not rely on any unauthorized information or representations. You should assume that the information appearing in this prospectus supplement, the accompanying base prospectus, the documents incorporated by reference in this prospectus supplement and the accompanying base prospectus and any free writing prospectus we have authorized for use in connection with this offering is accurate only as of the respective dates of those documents. Our business, financial condition, results of operations and prospects may have changed since those dates. You should carefully read this prospectus supplement, the accompanying base prospectus and the information and documents incorporated herein by reference herein and therein, as well as any free writing prospectus we have authorized for use in connection with this offering, before making an investment decision. See “Incorporation of Certain Documents by Reference” and “Where You Can Find More Information” in this prospectus supplement and in the accompanying base prospectus.

This prospectus supplement and the accompanying base prospectus contain summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the full text of the actual documents, some of which have been filed or will be filed and incorporated by reference herein. See “Where You Can Find More Information” in this prospectus supplement. We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference into this prospectus supplement or the accompanying base prospectus were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

All references in this prospectus supplement and the accompanying base prospectus to our consolidated financial statements include, unless the context indicates otherwise, the related notes.

This prospectus supplement and the accompanying base prospectus contain and incorporate by reference certain market data and industry statistics and forecasts that are based on management’s own estimates, independent industry publications, government publications, reports by market research firms and other publicly available information. Although we believe these sources are reliable, estimates as they relate to projections involve numerous assumptions, are subject to risks and uncertainties, and are subject to change based on various factors, including those discussed under “Risk Factors” in this prospectus supplement and the accompanying base prospectus and under similar

headings in the documents incorporated by reference herein and therein. Accordingly, investors should not place undue reliance on this information.

For investors outside the United States: We have not, and the placement agent has not, done anything that would permit this offering or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than in the United States. Persons outside the United States who come into possession of this prospectus supplement and the accompanying base prospectus must inform themselves about, and observe any restrictions relating to, the offering of the securities and the distribution of this prospectus supplement and the accompanying base prospectus outside the United States.

This prospectus supplement, the accompanying base prospectus, and the information incorporated by reference into this prospectus contain references to our trademarks and to trademarks belonging to other entities. Solely for convenience, trademarks and trade names referred to in this prospectus supplement, the accompanying base prospectus, and the information incorporated by reference into this prospectus supplement and the accompanying base prospectus, including logos, artwork, and other visual displays, may appear without the ® or TM symbols, but such references are not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights or the rights of the applicable licensor to these trademarks and trade names. We do not intend our use or display of other companies’ trade names or trademarks to imply a relationship with, or endorsement or sponsorship of us by, any other company.

Unless the context indicates or requires otherwise, all references in this prospectus supplement to “Aptevo,” the “Company,” “we,” “us” and “our” refer to Aptevo Therapeutics Inc., a Delaware corporation, and its wholly owned consolidated subsidiaries.

PROSPECTUS SUPPLEMENT SUMMARY

This prospectus supplement summary highlights information contained elsewhere in this prospectus supplement, the accompanying base prospectus and the documents incorporated by reference herein and therein. This summary does not contain all of the information that you should consider before deciding to invest in our securities. You should read this entire prospectus supplement and the accompanying base prospectus carefully, including the section entitled “Risk Factors” in this prospectus supplement and our consolidated financial statements and the related notes and the other information incorporated by reference into this prospectus supplement and the accompanying base prospectus, before making an investment decision.

Business Overview

We are a clinical-stage, research and development biotechnology company focused on developing novel immunotherapy candidates for the treatment of different forms of cancer. We have developed two versatile and enabling platform technologies for rational design of precision immune modulatory drugs and have two clinical candidates and three preclinical candidates currently in development. Clinical candidate mipletamig is a CD3xCD123 T cell engager currently being clinically evaluated in the RAINIER trail, part one of a Phase 1b/2 program initiated in August 2024 for the treatment of frontline acute myelogenous leukemia (AML) in combination with standard of care venetoclax + azacitidine. Clinical candidate ALG.APV-527 targets 4-1BB (co-stimulatory receptor) and 5T4 (tumor antigen). The compound is designed to reactivate antigen-primed T cells to specifically kill tumor cells and is currently being evaluated for the treatment of multiple solid tumor types.

Preclinical candidates, APVO603 and APVO711, were also developed using our ADAPTIR® modular protein technology platform. Our preclinical candidate APVO442 was developed using our ADAPTIR-FLEX® modular protein technology platform. We wholly own both platforms which enable us to efficiently design and create new molecules, supporting our pipeline growth.

Our ADAPTIR and ADAPTIR-FLEX platforms are designed to generate monospecific, bispecific, and multi-specific antibody candidates capable of enhancing the human immune system against cancer cells. ADAPTIR and ADAPTIR-FLEX are both modular platforms, which gives us the flexibility to potentially generate immunotherapeutic candidates with a variety of mechanisms of action. This flexibility in design allows us to generate novel therapeutic candidates that may provide effective strategies against difficult to treat, as well as advanced forms of cancer. We have successfully designed and constructed numerous investigational-stage product candidates based on our ADAPTIR platform. The ADAPTIR platform technology is designed to generate monospecific and bispecific immunotherapeutic proteins that specifically bind to one or more targets, for example, bispecific therapeutic molecules, which may have structural and functional advantages over monoclonal antibodies. We have also developed a preclinical candidate based on the ADAPTIR-FLEX platform which is advancing in our pipeline. The structural differences of ADAPTIR and ADAPTIR FLEX molecules over monoclonal antibodies allow for the development of immunotherapies that are designed to engage immune effector cells and disease targets to produce signaling responses that modulate the immune system to kill tumor cells. We believe we are skilled at candidate generation, validation, and subsequent preclinical and clinical development.

Our Strategy

We seek to grow our business by, among other things:

Advancing our lead clinical blood cancer candidate, mipletamig, through clinical development to evaluate its therapeutic potential alone and in combination with other therapies. Based on the positive results from our Phase 1 dose escalation and dose expansion studies, we are conducting a dose optimization Phase 1b/2 trial, RAINIER, in frontline AML patients who are receiving a combination of mipletamig and the standard of care (venetoclax + azacitidine) for patients who are unfit for intensive chemotherapy to assess safety and efficacy of mipletamig and to determine a recommended Phase 2 dose. Positive initial results from the frontline RAINIER trial show continued favorable efficacy and safety outcomes similar to those observed in the completed dose expansion phase of the trial. These results showed a 100% complete remission rate in the first cohort, including one patient who experienced complete remission with no minimal residual disease (MDR-negative). All patients achieved remission within thirty (30) days of the start of treatment. Cohort 2 of the frontline RAINIER trial is currently enrolling. As of the date of this

prospectus, 9 of 10 frontline patients across two trials achieved complete remission and complete remission with blood markers that have not yet recovered when receiving the triplet combination of mipletamig + venetoclax + azacitidine (ven/aza).

Advancing our lead solid tumor candidate, ALG.APV-527, developed in partnership with Alligator Bioscience AB (Alligator), in the clinic. Aptevo and Alligator continue to investigate ALG.APV-527 for the treatment of multiple solid tumor types with 5T4-tumor expressing antigens. Preliminary results from the first five (5) cohorts that included nineteen (19) patients showed that 58% of patients achieved a best response of stable disease. Positive safety (no liver toxicity, a common and potentially serious side effect associated with similar treatments), tolerability, and clinical activity. ALG.APV-527 targets the 4-1BB co-stimulatory receptor (on T lymphocytes and NK cells) and 5T4 (solid tumor antigen) and is designed to promote anti-tumor immunity. We believe this compound has the potential to be clinically important because 4-1BB can stimulate the immune cells (tumor-specific T cells and NK cells) involved in tumor control, making 4-1BB a particularly compelling target for cancer immunotherapy.

Continued development and advancement of our preclinical candidates, APVO603 (targeting 4-1BB (CD137) and OX40 (CD134), both members of the TNF-receptor family), APVO442 (targeting Prostate Specific Membrane Antigen (PSMA), a tumor antigen that is highly expressed on prostate cancer cells and CD3), and APVO711 (an anti-PD-L1 x anti-CD40 compound). We continue to advance APVO711, APVO603 and APVO442 through preclinical and IND-enabling studies. In January 2023, we filed a provisional patent with the U.S. Patent and Trademark Office (USPTO) pertaining to APVO711. In January 2024, the provisional patent was amended to include new preclinical data and a patent application under the Patent Cooperation Treaty (“PCT") pertaining to APVO711, which has the potential to treat a range of solid malignancies such as head and neck cancer. APVO711 is a dual mechanism bispecific antibody candidate that is designed to provide synergistic stimulation of CD40 on antigen presenting cells while simultaneously blocking the PD-1/PD-L1 inhibitory pathway to potentially promote a robust anti-tumor response. Preclinical studies are planned to further evaluate the mechanism of action and efficacy of APVO711.

Development of novel bispecific and multi-specific proteins for the treatment of cancer using our ADAPTIR and ADAPTIR-FLEX platforms. We have expertise in molecular and cellular biology, immunology, oncology, pharmacology, translational sciences, antibody engineering and the development of protein therapeutics. This includes target validation, preclinical proof of concept, cell line development, protein purification, bioassay and process development and analytical characterization. We focus on product development using our ADAPTIR and ADAPTIR-FLEX platforms. We plan to generate additional monospecific, bispecific, and multi-specific protein immunotherapies for development, potentially with other collaborative partners, to exploit the potential of the ADAPTIR and ADAPTIR-FLEX platforms. We will select novel candidates that have the potential to demonstrate proof of concept early in development. We expect to continue to expand the ADAPTIR and ADAPTIR-FLEX product pipelines to address areas of unmet medical need. Bispecific therapeutics are increasingly recognized as potent anti-cancer agents. Sixteen new bispecific agents have been approved for use by the FDA in the last three years and there is a total of 125 bispecific drug candidates currently in development. We believe our candidates in development and our future molecules derived from our ADAPTIR and ADAPTIR-FLEX platforms will be highly competitive in the market as they are rationally designed for safety and tolerability as well as efficacy.

Establishing collaborative partnerships to broaden our pipeline and provide funding for research and development. We intend to pursue collaborations with other biotechnology and pharmaceutical companies, academia, and non-governmental organizations to advance our product portfolio.

Product Candidates and Platform Technology

Product Portfolio

Our current product candidate pipeline is summarized in the table below:

Platform Technologies

Smaller Reporting Company

Additionally, we are a “smaller reporting company” as defined in Rule 10(f)(1) of Regulation S-K. To the extent we qualify as a smaller reporting company, we may continue to take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not smaller reporting companies, including, among other things, providing only two years of audited financial. We will remain a smaller reporting company until the last day of the fiscal year in which (1) the market value of our shares of common stock held by non-affiliates exceeds $250 million as of the prior June 30, or (2) our annual revenues exceeded $100 million during such completed fiscal year and the market value of our shares of common stock held by non-affiliates exceeds $700 million as of the prior June 30.

Corporate Information

On August 6, 2015, Emergent BioSolutions Inc. (“Emergent”), announced a plan to separate into two independent publicly traded companies. To accomplish this separation, Emergent created Aptevo Therapeutics Inc. (“Aptevo”), to be the parent company for the development-based biotechnology business focused on novel oncology and hematology therapeutics. Aptevo was incorporated in Delaware in February 2016 as a wholly owned subsidiary of Emergent. To effect the separation, Emergent made a pro rata distribution of Aptevo’s Common Stock to Emergent’s stockholders on August 1, 2016.

Our common stock currently trades on the Nasdaq under the symbol “APVO.” Our primary executive offices are located at 2401 4th Avenue, Suite 1050, Seattle, Washington and our telephone number is (206) 838-0500. Our website address is www.aptevotherapeutics.com. The information contained in, or that can be accessed through, our website is not a part of or incorporated by reference in this prospectus supplement or the accompanying base prospectus, and you should not consider it part of this prospectus supplement or the accompanying base prospectus. We have included our website address in this prospectus supplement solely as an inactive textual reference.

Risks Associated with our Business

Our business is subject to numerous risks, as described under the heading “Risk Factors,” any related free writing prospectus and the documents incorporated by reference herein and therein.

The Offering

The following is a brief summary of some of the terms of the offering and is qualified in its entirety by reference to the more detailed information appearing elsewhere in this prospectus supplement and the accompanying base prospectus. For a more complete description of the terms of our common stock, see “Description of Capital Stock” in the accompanying base prospectus.

The number of shares of our common stock expected to be outstanding immediately after this offering is based on 1,458,504 shares of common stock outstanding as of April 3, 2025, and excludes, as of that date, the following:

CAUTIONARY NOTE REGARDING FORWARD-LOOKING INFORMATION

This prospectus supplement, and any documents we incorporate by reference, contain certain forward-looking statements that involve substantial risks and uncertainties. All statements contained in this prospectus and any documents we incorporate by reference, other than statements of historical facts, are forward-looking statements including statements regarding our strategy, future operations, future financial position, future revenue, projected costs, prospects, plans, objectives of management and expected market growth. These statements involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements.

The words “anticipate”, “believe”, “estimate”, “expect”, “intend”, “may”, “plan”, “predict”, “project”, “target”, “potential”, “will”, “would”, “could”, “should”, “continue” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. These forward-looking statements include, among other things, statements about:

These forward-looking statements are only predictions, and we may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, so you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. We have based these forward-looking statements largely on our current expectations and projections about future events and trends that we believe may affect our business, financial condition and operating results. We have included important factors in the cautionary statements included in this

prospectus that could cause actual future results or events to differ materially from the forward-looking statements that we make. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures or investments we may make.

You should read this prospectus supplement and accompanying base prospectus with the understanding that our actual future results may be materially different from what we expect. We do not assume any obligation to update any forward-looking statements whether as a result of new information, future events or otherwise, except as required by applicable law.

RISK FACTORS

An investment in our securities involves a high degree of risk. Before deciding whether to purchase our securities, including the shares of common stock offered by this prospectus supplement and accompanying base prospectus, you should carefully consider the risks and uncertainties described under “Risk Factors” in our Annual Report on Form 10-K for the fiscal year ended December 31, 2024, any subsequent Quarterly Report on Form 10-Q and our other filings with the SEC, all of which are incorporated by reference herein. If any of these risks actually occur, our business, financial condition and results of operations could be materially and adversely affected and we may not be able to achieve our goals, the value of our securities could decline, and you could lose some or all of your investment. Additional risks not presently known to us or that we currently believe are immaterial may also significantly impair our business operations. If any of these risks occur, our business, results of operations or financial condition and prospects could be harmed. In that event, the market price of our common stock and the value of the warrants could decline, and you could lose all or part of your investment.

Risks Related to This Offering

We have broad discretion in the use of the net proceeds from this offering and may not use them effectively.

Our management will have broad discretion in the application of the net proceeds, including for any of the purposes described in the section of this prospectus supplement entitled “Use of Proceeds.” You will be relying on the judgment of our management with regard to the use of these net proceeds, and you will not have the opportunity, as part of your investment decision, to assess whether the net proceeds are being used appropriately. The failure by our management to apply these funds effectively could result in financial losses that could have a material adverse effect on our business, cause the price of our securities to decline and delay the development of our product candidates. Pending the application of these funds, we may invest the net proceeds from this offering in a manner that does not produce income or that loses value.

You will experience immediate and substantial dilution in the net tangible book value per share of the common stock you purchase. You may also experience future dilution as a result of future equity offerings.

The price per share, together with the number of shares of our common stock we issued and ultimately will issue in this offering, may result in an immediate decrease in the market price of our common stock. Our historical net tangible book value as of January 31, 2025 was $0.5 million, or approximately $0.37 per share of our common stock. After giving effect to the 1,764,710 shares of our common stock issued in this offering at an offering price of $1.19 per share, and the exercise of the Warrants sold in this offering, our as adjusted net tangible book value as of January 31, 2025 would have been $2.4 million, or approximately $0.75 per share of our common stock. This represents an immediate increase in the net tangible book value of $0.38 per share of our common stock to our existing stockholders and an immediate dilution in net tangible book value of approximately $0.44 per share of our common stock to new investors, representing the difference between the offering price and our as adjusted net tangible book value as of January 31, 2025, after giving effect to this offering, and the offering price per share and accompanying Common Warrants.

In addition, in order to raise additional capital, we may in the future offer additional shares of our common stock or other securities convertible into or exchangeable for our common stock at prices that may not be the same as the price per share in this offering. In the event that the outstanding options or warrants are exercised or settled, or that we make additional issuances of common stock or other convertible or exchangeable securities, you could experience additional dilution. We cannot assure you that we will be able to sell shares or other securities in any other offering at a price per share that is equal to or greater than the price per share paid by investors in this offering, and investors purchasing shares or other securities in the future could have rights superior to existing stockholders, including investors who purchase shares of common stock in this offering. The price per share at which we sell additional shares of our common stock or securities convertible into common stock in future transactions, may be higher or lower than the price per share in this offering. As a result, purchasers of the shares we sell, as well as our existing stockholders, will experience significant dilution if we sell at prices significantly below the price at which they invested.

A large number of shares of common stock issued in the concurrent private placement offering may be sold in the market following this offering, which may depress the market price of our common stock.

A large number of shares of common stock issued in this offering may be sold in the public market following this offering, which may depress the market price of our common stock. If there are more shares of common stock offered for sale than buyers are willing to purchase, then the market price of our common stock may decline to a market price at which buyers are willing to purchase the offered shares of common stock and sellers remain willing to sell the shares of common stock. The common stock issued in the offering will be freely tradable without restriction or further registration under the Securities Act.

There is no public market for the Common Warrants issued in the concurrent private placement offering.

There is no established public trading market for the Common Warrants, and we do not expect a market to develop. In addition, we do not intend to apply to list the Common Warrants on any national securities exchange or other nationally recognized trading system. Without an active market, the liquidity of the Common Warrants will be limited.

The Common Warrants issued in the concurrent private placement are not exercisable until Stockholder Approval and may not have any value.

Under Nasdaq listing rules, the Common Warrants and shares of common stock issuable upon exercise of the Common Warrants issued in the concurrent private placement are considered restricted securities and are not exercisable without Stockholder Approval for the issuance of shares of common stock issuable upon exercise of such Common Warrants. While we intend to use reasonable best efforts to seek Stockholder Approval for issuances of shares of common stock issuable upon exercise of the Common Warrants as applicable, there is no guarantee that the Stockholder Approval will ever be obtained. The Common Warrants will be exercisable commencing on the date Stockholder Approval is obtained, at an initial exercise price per share of $1.19. In the event that the price of a share of our common stock does not exceed the exercise price of the Common Warrants during the period when the Common Warrants are exercisable, the Common Warrants may not have any value. If we are unable to obtain the Stockholder Approval, the Common Warrants will not be exercisable and therefore would have no value.

In addition, we may incur substantial cost, and management may devote substantial time and attention, in attempting to obtain Stockholder Approval of the issuance of shares of common stock upon exercise of the Common Warrants issued in the concurrent private placement.

We have in the past and may in the future be subject to short selling strategies that may drive down the market price of our common stock.

Short sellers have in the past and may attempt in the future to drive down the market price of our common stock. Short selling is the practice of selling securities that the seller does not own but may have borrowed with the intention of buying identical securities back at a later date. The short seller hopes to profit from a decline in the value of the securities between the time the securities are borrowed and the time they are replaced. As it is in the short seller’s best interests for the price of the stock to decline, many short sellers (sometime known as “disclosed shorts”) publish, or arrange for the publication of, negative opinions regarding the relevant issuer and its business prospects to create negative market momentum. Although traditionally these disclosed shorts were limited in their ability to access mainstream business media or to otherwise create negative market rumors, the rise of the Internet and technological advancements regarding document creation, videotaping and publication by weblog (“blogging”) have allowed many disclosed shorts to publicly attack a company’s credibility, strategy and veracity by means of so-called “research reports” that mimic the type of investment analysis performed by large Wall Street firms and independent research analysts. These short attacks have, in the past, led to selling of shares in the market. Further, these short seller publications are not regulated by any governmental, self-regulatory organization or other official authority in the U.S. and they are not subject to certification requirements imposed by the SEC. Accordingly, the opinions they express may be based on distortions, omissions or fabrications. Companies that are subject to unfavorable allegations, even if untrue, may have to expend a significant amount of resources to investigate such allegations and/or defend themselves, including shareholder suits against the company that may be prompted by such allegations. We may in the future be the subject of shareholder suits that we believe were prompted by allegations made by short sellers.

The securities purchase agreement that we are entering into in connection with this offering does not contain a prohibition against short sales. While the SEC and Financial Institutions Regulatory Authority (“FINRA”) rules prohibit some forms of short selling and other activities that may result in stock price manipulation, such activity may

nonetheless occur without detection or enforcement. Significant short selling or other types of market manipulation could cause our stock trading price to decline, to become more volatile, or both.

The Warrants are speculative in nature.

The Common Warrants offered hereby do not confer any rights of share of common stock ownership on their holders, such as voting rights or the right to receive dividends, but rather merely represent the right to acquire shares of common stock at a fixed price. Specifically, only following receipt of the Stockholder Approval, the Common Warrants will be exercisable upon issuance, holders of the Common Warrants may acquire the shares of common stock issuable upon exercise of such warrants at an exercise price of $1.19 per share of common stock. If we are unable to obtain Stockholder Approval, the Common Warrants will not be exercisable and therefore would have no value. Moreover, following this offering, the market value of the Common Warrants is uncertain and there can be no assurance that the market value of the Common Warrants will equal or exceed their respective offering prices. There can be no assurance that the market price of the shares of common stock will ever equal or exceed the exercise price of the Common Warrants, and consequently, whether it will ever be profitable for holders of Common Warrants to exercise the Common Warrants.

Holders of the Common Warrants offered pursuant to a concurrent private placement will have no rights as common stockholders with respect to the shares of our common stock underlying the Common Warrants until such holders exercise their Common Warrants and acquire our common stock, except as otherwise provided in the Common Warrants.

Until holders of the Common Warrants acquire shares of our common stock upon exercise thereof, such holders will have no rights with respect to the shares of our common stock underlying such Common Warrants, except to the extent that holders of such Common Warrants will have certain rights to participate in distributions or dividends paid on our common stock as set forth in the Common Warrants. Upon exercise of the Common Warrants, the holders will be entitled to exercise the rights of a common stockholder only as to matters for which the record date occurs after the exercise date.

Purchasers who purchase our securities in this offering pursuant to a securities purchase agreement may have rights not available to purchasers that purchase our securities without the benefit of a securities purchase agreement.

In addition to rights and remedies available to all purchasers in this offering under federal securities and state law, the purchasers that enter into a securities purchase agreement will also be able to bring claims of breach of contract against us. The ability to pursue a claim for breach of contract provides those investors with the means to enforce the covenants uniquely available to them under the securities purchase agreement including, but not limited to: (i) timely delivery of securities; (ii) agreement to not enter into any financings for 15 days from closing; and (iii) indemnification for breach of contract.

Resales of our common stock in the public market during this offering by our stockholders may cause the market price of our common stock to fall.

Sales of a substantial number of shares of our common stock could occur at any time. The issuance of new shares of our common stock could result in resales of our common stock by our current stockholders concerned about the potential ownership dilution of their holdings. In turn, these resales could have the effect of depressing the market price for our common stock.

This offering may cause the trading price of our common stock to decrease.

The price per share, together with the number of shares of common stock we issued and ultimately will issue in this offering, may result in an immediate decrease in the market price of our common stock. This decrease in the trading price may continue after the completion of this offering.

Our common stock may be at risk for delisting from the Nasdaq Capital Market in the future if we do not maintain compliance with Nasdaq’s continued listing requirements. Delisting could adversely affect the liquidity of our common stock, and the market price of our common stock could decrease.

Our common stock is currently listed on the Nasdaq Capital Market LLC (Nasdaq) and on April 3, 2025, the last reported sale price of our common stock on Nasdaq was $1.99 per share. Nasdaq has minimum requirements that a company must meet in order to remain listed on Nasdaq, including corporate governance standards and a requirement that we maintain a minimum closing bid price of $1.00 per share, among other requirements. This offering could cause the bid price of our common stock to drop below $1.00 per share, for 30 consecutive business days, the minimum closing bid price required by the continued listing requirements of Nasdaq Listing Rule 5550(a)(2) (the “Bid Price Requirement”). If we fail to meet the Bid Price Requirement, we are not eligible for a 180 day cure period from Nasdaq to regain compliance with such requirement because we have conducted a reverse stock split in the past year and thus we would be immediately delisted.

In an effort to maintain our ability to comply with the Bid Price Requirement, we plan to call a special meeting of our stockholders following the completion of this offering in order to, among other things, effect a reverse stock split. If this reverse stock split is approved, we would, if necessary, seek to effectuate a reverse stock split prior to failing to meet the Bid Price Requirement.

In the future, if we fail to maintain the minimum listing requirements of Nasdaq and a final determination is made by Nasdaq that our common stock must be delisted, the liquidity of our common stock would be adversely affected, and the market price of our common stock could decrease. In addition, if delisted, we would no longer be subject to Nasdaq rules, including rules requiring us to have a certain number of independent directors and to meet other corporate governance standards. Our failure to be listed on Nasdaq or another established securities market would have a material adverse effect on the value of your investment in us.

If our common stock is not listed on Nasdaq or another national exchange, the trading price of our common stock is below $5.00 per share and we have net tangible assets of $6,000,000 or less, the open-market trading of our common stock will be subject to the "penny stock" rules promulgated under the Securities Exchange Act of 1934, as amended. If our shares become subject to the "penny stock" rules, broker-dealers may find it difficult to effectuate customer transactions and trading activity in our securities may be adversely affected.

USE OF PROCEEDS

We estimate that the net proceeds from the offering will be approximately $1.9 million, after deducting the placement agent fees and estimated offering expenses payable by us. This estimate excludes the proceeds, if any, from the cash exercise of the Common Warrants issued in the concurrent private placement.

We currently intend to use the net proceeds from this offering for working capital to fund our clinical programs and general corporate purposes, including the further development of our product candidates. This expected use of proceeds from this offering represents our intentions based upon our current plans and prevailing business conditions, which could change in the future as our plans and prevailing business conditions evolve. The amounts and timing of our use of proceeds will vary depending on a number of factors, including the amount of cash generated or used by our operations. As a result, we will retain broad discretion in the allocation of the net proceeds of this offering.

DILUTION

If you purchase shares of our common stock, your interest will be diluted immediately to the extent of the difference between the offering price per share you will pay in this offering and the concurrent private placement and the as adjusted net tangible book value per share of our common stock after this offering. Net tangible book value per share represents our total tangible assets less total liabilities, divided by the number of shares of our common stock outstanding.

As of January 31, 2025, our net tangible book value was $0.5 million, or $0.37 per share of common stock.

After giving effect to the sale of 1,764,710 shares of our common stock offered in this offering at the offering price of $1.19 per share and accompany Common Warrants (excluding shares of common stock issuable upon exercise of the Warrants), and after deducting the underwriting discount and estimated offering expenses payable by us, our as adjusted net tangible book value as of January 31, 2025 would have been approximately $2.4 million, or approximately $0.75 per share. This represents an immediate increase in net tangible book value of approximately $0.38 per share to our existing stockholders and immediate dilution in net tangible book value of approximately $0.44 per share to investors participating in this offering. The dilution figures excludes the proceeds, if any, from the exercise of any Common Warrants issued in the concurrent private placement.

The following table illustrates this calculation on a per share basis:

The above discussion is based on 1,458,445 shares of our common stock outstanding as of January 31, 2025, and excludes, as of that date, the following:

PRIVATE PLACEMENT OF COMMON WARRANTS

The following is a summary of the material terms and provisions of the Common Warrants. This summary is subject to and qualified in its entirety by the form of Common Warrant, which has been provided to the purchasers in this offering and which will be filed with the SEC as an exhibit to a Current Report on Form 8-K in connection with this offering and incorporated by reference into the registration statement of which this prospectus supplement forms a part.

Concurrently with the closing of the sale of shares of common stock in this offering, we also expect to issue and sell to the investors Common Warrants to purchase an aggregate of up to 3,529,420 shares of our common stock. The Common Warrants will not be exercisable prior to the Stockholder Approval and will expire five years from the date of the Stockholder Approval, subject to certain limitations described herein, and have an exercise price of $1.19 per share.

Subject to limited exceptions, a holder of Common Warrants will not have the right to exercise any portion of its Warrants if the holder, together with its affiliates, would beneficially own in excess of 4.99% or 9.99% (at the election of the holder) of the number of shares of our common stock outstanding immediately after giving effect to such exercise.

In the event of a Fundamental Transaction (as defined in the Common Warrant), as described in the form of Common Warrant, and generally including any reorganization, recapitalization or reclassification of our common stock, the sale, transfer or other disposition of all or substantially all of our properties or assets, our consolidation or merger with or into another person, the acquisition of more than 50% of our outstanding common stock, or any person or group becoming the beneficial owner of 50% of the voting power represented by our outstanding common stock, the holders of the Common Warrants will be entitled to receive upon exercise of the Common Warrants the kind and amount of securities, cash or other property that the holders would have received had they exercised the Common Warrants immediately prior to such fundamental transaction, other than one in which a successor entity that is a publicly traded corporation (whose stock is quoted or listed for trading on a national securities exchange, including, but not limited to, the New York Stock Exchange, the NYSE American, the Nasdaq Global Select Market, the Nasdaq Global Market or the Nasdaq Capital Market) assumes the Common Warrant such that the Common Warrant shall be exercisable for the publicly traded common stock of such successor entity. Additionally, as more fully described in the Common Warrants, at the option of the holders of the Common Warrants the holder can receive consideration in the same type and form of an amount equal to the Black Scholes value (as defined in the Common Warrant) of such unexercised common warrants on the date of consummation of such transaction.

We have agreed that pursuant to the securities purchase agreement from the date of issuance of the Common Warrants to the (3) month anniversary of the closing date of this offering, upon any issuance by us or any of our subsidiaries of common stock or common stock equivalents for cash consideration, indebtedness or a combination of units thereof (a “Subsequent Financing”), each purchaser will have the right to participate in up to an amount of the Subsequent Financing equal to 50% of the Subsequent Financing on the same terms, conditions and price provided for in the Subsequent Financing.

Such securities will be issued and sold without registration under the Securities Act, or state securities laws, in reliance on the exemptions provided by Section 4(a)(2) of the Act and Regulation D promulgated thereunder and in reliance on similar exemptions under applicable state laws. Accordingly, the investor may exercise those Common Warrants and sell the underlying shares only pursuant to an effective registration statement under the Securities Act covering the resale of those shares, an exemption under Rule 144 under the Securities Act, or another applicable exemption under the Securities Act. We have agreed to file a registration statement with the SEC registering the resale of the shares of common stock underlying the Warrants as soon as practicable (and in any event within 30 calendar days of the date of the securities purchase agreement).

The Common Warrants will not be exercisable without Stockholder Approval. We have agreed to hold a special meeting of the stockholders, within sixty (60) days following the closing of this offering, in order to seek such Stockholder Approval as may be required by the applicable rules and regulations of the Nasdaq Capital Market (or any successor entity) from our stockholders in order to permit the exercise of the common warrants. We cannot assure

you that we will be able to obtain Stockholder Approval. In the event that we are unable to obtain the Stockholder Approval, the Common Warrants will not be exercisable and therefore have no value. We have agreed to use reasonable best efforts to hold a special meeting of stockholders in order to obtain Stockholder Approval. If we do not obtain Stockholder Approval with respect to the terms of the Common Warrants at the first special meeting of the stockholders, we have agreed to call a meeting every sixty (60) days thereafter to seek such Stockholder Approval until the date on which Stockholder Approval is obtained or the Common Warrants are no longer outstanding.

In connection with the issuance of the Common Warrants, we have agreed to amend certain existing warrants that were previously issued on December 12, 2024 to purchase 1,647,088 shares of common stock and have exercise price of $9.53 per share (the “Existing Warrants”), such that the Existing Warrants will have a reduced exercise price equal to $1.19 per share and include the same voluntary exercise price adjustments as the Common Warrants. The amended warrants will be exercisable upon the same Stockholder Approval as for the Common Warrants and will expire five years from the date of the Stockholder Approval.

DESCRIPTION OF SECURITIES OFFERED

We are offering 1,764,710 shares of our common stock in a registered direct offering and Common Warrants to purchase up to 3,529,420 shares of our common stock in a private placement.

Common Stock

The material terms and provisions of our common stock are described under the caption “Description of Capital Stock” in the base prospectus and are incorporated herein by reference.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Broadridge, which can be contacted at 51 Mercedes Way, Edgewood, NY 11717, [email protected], or +1 (720) 378-5591.

Listing on the Nasdaq Capital Market

Our common stock is listed on the Nasdaq Capital Market under the symbol “APVO.”

PLAN OF DISTRIBUTION

We have engaged Roth Capital Partners, LLC to act as our placement agent pursuant to a placement agency agreement in connection with this offering, dated as of April 3, 2025. The placement agent is not purchasing or selling any of the securities we are offering by this prospectus supplement.

Placement Agent Fees and Expenses

The following table shows the offering price per share and two Common Warrants, and total placement agent fees we will pay in connection with the sale of the securities in this offering.

We have entered into securities purchase agreements, each dated April 3, 2025, directly with several investors who have agreed to purchase the securities in this offering. The securities purchase agreements provide that the obligations of the investors are subject to certain conditions precedent.

We currently anticipate that the closing of this offering will take place on or about April 4, 2025, subject to customary closing conditions.

We have agreed to pay the placement agent a placement agent fee in cash equal to 7.0% of the gross proceeds from the sale of the securities in this offering.

In addition, we have agreed to reimburse the placement agent at the closing for its expenses in connection with this offering in the amount not to exceed $100,000.

We have agreed not to issue, enter into any agreement to issue or announce the issuance or proposed issuance of, any shares of common stock or any securities convertible into or exercisable or exchangeable for shares of common stock or file any registration statement or prospectus, or any amendment or supplement thereto until 15 days after the closing of this offering, subject to certain exceptions. In addition, we have agreed not to effect or enter into an agreement to effect any issuance of common stock or any securities convertible into or exercisable or exchangeable for shares of common stock involving a Variable Rate Transaction (as defined in the securities purchase agreement) until 15 days year after the closing of this offering, subject to certain exceptions.

We have agreed to indemnify the placement agent and certain other persons against certain liabilities relating to or arising out of the placement agent’s activities under the placement agent agreement. We have also agreed to contribute to payments the placement agent may be required to make in respect of such liabilities.

The placement agent may be deemed to be an underwriter within the meaning of Section 2(a)(11) of the Securities Act, and any fees received by it and any profit realized on the resale of the shares sold by it while acting as principal might be deemed to be underwriting discounts or commissions under the Securities Act. As an underwriter, the placement agent would be required to comply with the requirements of the Securities Act and the Exchange Act, including, without limitation, Rule 415(a)(4) under the Securities Act and Rule 10b-5 and Regulation M under the Exchange Act. These rules and regulations may limit the timing of purchases and sales of shares of common stock by the placement agent acting as principal. Under these rules and regulations, the placement agent:

● must not engage in any stabilization activity in connection with our securities; and

● must not bid for or purchase any of our securities or attempt to induce any person to purchase any of our securities, other than as permitted under the Exchange Act, until it has completed its participation in the distribution.

A copy of the form of the securities purchase agreement we entered into with the investors will be included as an exhibit to our Current Report on Form 8-K that will be filed with the Securities and Exchange Commission in connection with this offering.

LEGAL MATTERS

The validity of the securities offered hereby will be passed upon for us by Paul Hastings LLP, Washington, DC. The placement agent is being represented by Ellenoff Grossman & Schole LLP, New York, NY.

EXPERTS

Our consolidated financial statements as of December 31, 2024 and 2023, and for the years then ended, incorporated in this prospectus by reference and included in our Annual Report on Form 10-K for the year ended December 31, 2024, have been audited by Moss Adams LLP, an independent registered public accounting firm, as stated in their report (which report expresses an unqualified opinion and includes an explanatory paragraph related to a going concern uncertainty), which is incorporated herein by reference. Such consolidated financial statements are incorporated by reference in reliance upon the report of such firm given their authority as experts in accounting and auditing.

INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

The SEC permits us to “incorporate by reference” the information and reports we file with it. This means that we can disclose important information to you by referring to another document. The information that we incorporate by reference is considered to be part of this prospectus supplement, and later information that we file with the SEC automatically updates and supersedes this information. We incorporate by reference the documents listed below, except to the extent information in those documents is different from the information contained in this prospectus supplement, and all future documents filed with the SEC under Sections 13(a), 13(c), 14, or 15(d) of the Exchange Act until we terminate the offering of these securities:

To the extent that any statement in this prospectus supplement is inconsistent with any statement that is incorporated by reference and that was made on or before the date of this prospectus supplement, the statement in this prospectus supplement shall supersede such incorporated statement. The incorporated statement shall not be deemed, except as modified or superseded, to constitute a part of this prospectus supplement or the registration statement. Statements contained in this prospectus supplement as to the contents of any contract or other document are not necessarily complete and, in each instance, we refer you to the copy of each contract or document filed as an exhibit to our various filings made with the SEC.

We will furnish without charge to you, on written or oral request, a copy of any or all of the documents incorporated by reference, including exhibits to these documents. You should direct any requests for documents to:

Aptevo Therapeutics Inc.

2401 4th Avenue, Suite 1050

Seattle, WA 98121

Attn: General Counsel

(206) 838-0500

This prospectus supplement is part of a registration statement we filed with the SEC. That registration statement and the exhibits filed along with the registration statement contain more information about us and the shares in this offering. Because information about documents referred to in this prospectus supplement is not always complete, you should read the full documents which are filed as exhibits to the registration statement. You may read and copy the full registration statement and its exhibits at the SEC’s website.

WHERE YOU CAN FIND MORE INFORMATION

This prospectus supplement is part of a registration statement we filed with the SEC. This prospectus supplement does not contain all of the information set forth in the registration statement and the exhibits to the registration statement. For further information with respect to us and the securities we are offering under this prospectus supplement, we refer you to the registration statement and the exhibits and schedules filed as a part of the registration statement. You should rely only on the information contained in this prospectus supplement or incorporated by reference into this prospectus supplement. We have not authorized anyone else to provide you with different information. We are not making an offer of these securities in any jurisdiction where the offer is not permitted. You should assume that the information contained in this prospectus supplement, or any document incorporated by reference in this prospectus supplement, is accurate only as of the date of those respective documents, regardless of the time of delivery of this prospectus supplement or any sale of our securities.

We are subject to the informational requirements of the Exchange Act and in accordance therewith we file annual, quarterly, and other reports, proxy statements and other information with the Commission under the Exchange Act. Such reports, proxy statements and other information, including the Registration Statement, and exhibits and schedules thereto, are available to the public through the Commission’s website at www.sec.gov.

We make available free of charge on or through our website our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended, as soon as reasonably practicable after we electronically file such material with or otherwise furnish it to the Commission. The registration statement and the documents referred to under “Incorporation of Certain Information by Reference” are also available on our website, https://aptevotherapeutics.gcs-web.com/financial-reports/sec-filings.

We have not incorporated by reference into this prospectus supplement the information on our website, and you should not consider it to be a part of this prospectus supplement.

PROSPECTUS

$100,000,000

Common Stock

Preferred Stock

Debt Securities

Warrants

Subscription Rights

We may, from time to time, offer and sell up to $100,000,000 of any combination of our Common Stock, preferred stock, debt securities, warrants or subscription rights described in this prospectus, either individually or in combination with other securities, at prices and on terms described in one or more supplements to this prospectus. We may also offer Common Stock or preferred stock upon conversion of debt securities, Common Stock upon conversion of preferred stock, Common Stock, preferred stock or debt securities upon the exercise of warrants or Common Stock, preferred stock, debt securities or warrants upon the exercise of subscription rights. We may also authorize one or more free writing prospectuses to be provided to you in connection with these offerings.

This prospectus describes some of the general terms that may apply to an offering of our securities. We will provide the specific terms of these offerings and securities in one or more supplements to this prospectus. We may also authorize one or more free writing prospectuses to be provided to you in connection with these offerings. The prospectus supplement and any related free writing prospectus may also add, update or change information contained or incorporated by reference in this prospectus. You should carefully read this prospectus, the applicable prospectus supplement and any related free writing prospectus, as well as the documents incorporated by reference herein and therein, before buying any of the securities being offered. This prospectus may not be used to offer and sell securities unless accompanied by a prospectus supplement.

Securities may be sold by us to or through underwriters or dealers, directly to purchasers or through agents designated from time to time. For additional information on the methods of sale, you should refer to the section entitled “Plan of Distribution” in this prospectus and in the applicable prospectus supplement. If any underwriters are involved in the sale of any securities with respect to which this prospectus is being delivered, the names of such underwriters and any applicable discounts or commissions and over-allotment options will be set forth in a prospectus supplement. The price to the public of such securities and the net proceeds we expect to receive from such sale will also be set forth in a prospectus supplement.

Our Common Stock is listed on the Nasdaq Capital Market under the symbol “APVO.” On February 13, 2025, the last reported sale price of our Common Stock on the Nasdaq Capital Market was $3.64 per share. Pursuant to General Instruction I.B.6 of Form S-3, in no event will we sell our common stock in a public primary offering with a value exceeding more than one-third of our public float in any 12-month period so long as our public float remains below $75.0 million. We have not offered any securities pursuant to General Instruction I.B.6 of Form S-3 during the 12 calendar months prior to and including the date of this prospectus.

Investing in our securities involves a high degree of risk. You should review carefully the risks and uncertainties described under the heading “Risk Factors” on page 9 of this prospectus and under similar headings in the applicable prospectus supplement, any free writing prospectuses we have authorized for use in connection with a specific offering and in the documents incorporated by reference herein and therein.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is February 14, 2025.

TABLE OF CONTENTS

About this Prospectus

This prospectus is part of a registration statement on Form S-3 that we filed with the Securities and Exchange Commission, or the SEC, using a “shelf” registration process. Under this shelf registration statement, we may sell from time to time in one or more offerings up to a total dollar amount of $100,000,000 of Common Stock, preferred stock, subscription rights, various series of debt securities and/or warrants to purchase any of such securities, either individually or in combination with other securities as described in this prospectus. We may also file a prospectus supplement or post-effective amendment to the registration statement of which this prospectus forms a part that may contain material information relating to these offerings. The prospectus supplement or post-effective amendment may also add, update or change information contained in this prospectus with respect to that offering. If there is any inconsistency between the information in this prospectus and the applicable prospectus supplement or post-effective amendment, you should rely on the prospectus supplement or post-effective amendment, as applicable. Before purchasing any securities, you should carefully read this prospectus, any post-effective amendment, and any applicable prospectus supplement, together with the additional information incorporated by reference into this prospectus and described under the heading “Where You Can Find More Information.” You may obtain the information incorporated by reference without charge by following the instructions under “Where You Can Find More Information.” You should carefully read this prospectus as well as additional information described under “Information Incorporated by Reference,” before deciding to invest in our securities.

You should rely only on the information contained in this prospectus. We have not authorized anyone to provide you with any information other than that contained in this prospectus. We take no responsibility for and can provide no assurance as to the reliability of, any other information that others may give you. This prospectus may only be used where it is legal to offer and sell our securities. The information in this prospectus is accurate only as of the date of this prospectus, regardless of the time of delivery of this prospectus or any sale of our securities. Our business, financial condition, results of operations and prospects may have changed since that date. We are not making an offer of these securities in any jurisdiction where the offer is not permitted.

For investors outside the United States: We have not done anything that would permit this offering or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than in the United States. Persons outside the United States must inform themselves about, and observe any restrictions relating to, the offering of securities and the distribution of this prospectus outside the United States.

For purposes of this prospectus, references to the terms “APVO,” “the Company,” “we,” “us” and “our” refer to Aptevo Therapeutics Inc., together with its subsidiaries, unless the context otherwise requires. This prospectus and the information incorporated herein by reference include trademarks, service marks and trade names owned by us or other companies. All trademarks, service marks and trade names included or incorporated by reference into this prospectus and the information incorporated herein by reference are the property of their respective owners.

We urge you to read carefully this prospectus, as supplemented and amended, before deciding whether to invest in any of the securities being offered.

The Securities We May Offer

We may offer shares of our common stock, preferred stock, subscription rights, various series of debt securities and/or warrants to purchase any of such securities, either individually or in combination with other securities, with a total value of up to $100,000,000 from time to time under this prospectus at prices and on terms to be determined at the time of any offering. This prospectus provides you with a general description of the securities we may offer. Each time we offer a type or series of securities under this prospectus, we will provide a prospectus supplement to this prospectus that will describe the specific amounts, prices and other important terms of the securities, including, to the extent applicable:

The prospectus supplement and any related free writing prospectus that we may authorize to be provided to you may also add, update or change information contained or incorporated by reference in this prospectus. However, no prospectus supplement or free writing prospectus will offer a security that is not registered and described in this prospectus at the time of the effectiveness of the registration statement of which this prospectus is a part.

This prospectus may not be used to consummate a sale of securities unless it is accompanied by a prospectus supplement.

We may sell the securities directly to investors or to or through agents, underwriters or dealers. We, and our agents, underwriters or dealers reserve the right to accept or reject all or part of any proposed purchase of securities. If we do offer securities to or through agents, underwriters or dealers, we will include in the applicable prospectus supplement:

Common Stock.

We may issue shares of our Common Stock from time to time. Each holder of our Common Stock is entitled to one vote for each share on all matters submitted to a vote of the stockholders, including the election of directors. Under our amended and restated certificate of incorporation, or certificate of incorporation, and amended and restated bylaws, or bylaws, our stockholders do not have cumulative voting rights. Because of this, the holders of a majority of the shares of Common Stock entitled to vote in any election of directors can elect all of the directors standing for election, if they should so choose. Subject to preferences that may be applicable to any then-outstanding preferred stock, holders of Common Stock are entitled to receive ratably those dividends, if any, as may be declared from time

to time by our board of directors out of legally available funds. In the event of our liquidation, dissolution or winding up, holders of Common Stock are entitled to share ratably in the net assets legally available for distribution to stockholders after the payment of all of our debts and other liabilities and the satisfaction of any liquidation preference granted to the holders of any then-outstanding shares of preferred stock. Holders of Common Stock have no preemptive, conversion or subscription rights and there are no redemption or sinking fund provisions applicable to the Common Stock. The rights, preferences and privileges of the holders of Common Stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of preferred stock that we may designate in the future.

Preferred Stock.

We may issue shares of our preferred stock from time to time, in one or more series. Our board of directors will determine the designations, voting powers, preferences and rights of the preferred stock, as well as the qualifications, limitations or restrictions thereof, including dividend rights, conversion rights, preemptive rights, terms of redemption or repurchase, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of any series. Convertible preferred stock will be convertible into our Common Stock or exchangeable for other securities. Conversion may be mandatory or at your option and would be at prescribed conversion rates.

If we sell any series of preferred stock under this prospectus, we will fix the designations, voting powers, preferences and rights of such series of preferred stock, as well as the qualifications, limitations or restrictions thereof, in the certificate of designation relating to that series. We will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of any certificate of designation that describes the terms of the series of preferred stock that we are offering before the issuance of the related series of preferred stock. We urge you to read the applicable prospectus supplement (and any free writing prospectus that we may authorize to be provided to you) related to the series of preferred stock being offered, as well as the complete certificate of designation that contains the terms of the applicable series of preferred stock.

Debt Securities.

We may issue debt securities from time to time, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. The senior debt securities will rank equally with any other unsecured and unsubordinated debt. The subordinated debt securities will be subordinate and junior in right of payment, to the extent and in the manner described in the instrument governing the debt, to all of our senior indebtedness. Convertible debt securities will be convertible into or exchangeable for our Common Stock or other securities. Conversion may be mandatory or at your option and would be at prescribed conversion rates.

Any debt securities issued under this prospectus will be issued under one or more documents called indentures, which are contracts between us and a national banking association or other eligible party, as trustee. In this prospectus, we have summarized certain general features of the debt securities. We urge you, however, to read the applicable prospectus supplement (and any free writing prospectus that we may authorize to be provided to you) related to the series of debt securities being offered, as well as the complete indentures that contain the terms of the debt securities. A form of indenture has been filed as an exhibit to the registration statement of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of the debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC.

Warrants.

We may issue warrants for the purchase of Common Stock, preferred stock and/or debt securities in one or more series. We may issue warrants independently or together with Common Stock, preferred stock and/or debt securities, and the warrants may be attached to or separate from these securities. In this prospectus, we have summarized certain general features of the warrants. We urge you, however, to read the applicable prospectus supplement (and any free writing prospectus that we may authorize to be provided to you) related to the series of warrants being offered, as well as any warrant agreements and warrant certificates that contain the terms of the warrants. We have filed forms of the warrant agreements and forms of warrant certificates containing the terms of the

warrants that may be offered as exhibits to the registration statement of which this prospectus is a part. We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of warrant and/or the warrant agreement and warrant certificate, as applicable, that contain the terms of the particular series of warrants we are offering, and any supplemental agreements, before the issuance of such warrants.

Any warrants issued under this prospectus may be evidenced by warrant certificates. Warrants also may be issued under an applicable warrant agreement that we enter into with a warrant agent. We will indicate the name and address of the warrant agent, if applicable, in the prospectus supplement relating to the particular series of warrants being offered.

Subscription Rights

We may issue subscription rights to purchase shares of Common Stock, shares of preferred stock, debt securities, warrants, or any combination thereof. These subscription rights may be issued independently or together with any other security offered by us, and they may or may not be transferable by the stockholder receiving the subscription rights in such offering. In connection with any offering of subscription rights, we may enter into a standby arrangement with one or more underwriters or other purchasers pursuant to which the underwriters or other purchasers may be required to purchase any securities remaining unsubscribed for after such offering.

Risk Factors

An investment in our securities involves a significant degree of risk. You should carefully consider the risk factors and all of the other information included in this prospectus and the documents we have incorporated by reference into this prospectus, including those in “Item 1A. Risk Factors” in our Annual Report on Form 10-K for the fiscal year ended December 31, 2024, incorporated herein by reference, before making an investment decision. Any of these risks and uncertainties could have a material adverse effect on our business, financial condition, cash flows and results of operations. If that occurs, the trading price of our Common Stock could decline materially, and you could lose all or part of your investment.

The risks included in this prospectus and the documents we have incorporated by reference into this prospectus are not the only risks we face. We may experience additional risks and uncertainties not currently known to us, or as a result of developments occurring in the future. Conditions that we currently deem to be immaterial may also materially and adversely affect our business, financial condition, cash flows and results of operations, and our ability to pay distributions to stockholders. Please also read carefully the section below entitled “Forward-Looking Statements.”

Forward-Looking Statements

This prospectus, the applicable prospectus supplement and any free writing prospectus, including the documents we incorporate by reference herein and therein, contain forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 and involve substantial risks and uncertainties. All statements other than statements of historical fact are forward-looking statements. These statements include, but are not limited to, statements regarding our intentions, beliefs, projections, outlook, analyses or current expectations concerning, among other things, our ongoing and planned preclinical development and clinical trials, the timing of and our ability to make regulatory filings and obtain and maintain regulatory approvals for our product candidates and any future product candidates, our intellectual property position, the degree of clinical utility of our product candidates, particularly in specific patient populations, our ability to develop and commercialize any product candidates, expectations regarding clinical trial data, statements regarding potential milestone payments, potential partnerships and collaborations, the advancement of our clinical and preclinical trials, our goals and milestones, our expectations regarding the size of the patient populations for our product candidates if approved for commercial use, our expectations regarding the effectiveness of our ADAPTIR and ADAPTIR-FLEX platforms, our ability to utilize any net operating losses, our results of operations, cash needs, spending of the proceeds from the offering described in this prospectus, financial condition, liquidity, prospects, growth and strategies, the industry in which we operate and the trends that may affect the industry or us. In some cases, you can identify forward-looking statements by terminology such as “believe,” “will,” “may,” “estimate,” “continue,” “anticipate,” “intend,” “should,” “plan,” “might,” “approximately,” “expect,” “predict,” “could,” “potentially” or the negative of these terms or other similar expressions, but the absence of these words does not mean that a statement is not forward looking.

These statements relate to future events or our future financial performance and involve known and unknown risks, uncertainties and other factors that could cause our actual results, levels of activity, performance or results of operations to differ materially from those expressed or implied by these forward-looking statements. These statements reflect our views with respect to future events as of the time they were made and are based on assumptions and subject to risks and uncertainties. You should read the matters described in “Risk Factors” in this prospectus, in our Annual Report on Form 10-K and in our Quarterly Report on Form 10-Q which are incorporated by reference into this prospectus and the other cautionary statements made in this prospectus as being applicable to all related forward-looking statements wherever they appear in this prospectus or the documents incorporated by reference into this prospectus. In addition to factors identified under the section titled “Risk Factors” in this prospectus, factors that may impact such forward-looking statements include:

These forward-looking statements are only predictions and we may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, so you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. We have based these forward-looking statements largely on our current expectations and projections about future events and trends that we believe may affect our business, financial condition and operating results. We have included important factors in the cautionary statements included in this prospectus that could cause actual future results or events to differ materially from the forward-looking statements that we make. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures or investments we may make.

You should read this prospectus with the understanding that our actual future results may be materially different from what we expect. We do not assume any obligation to update any forward-looking statements whether as a result of new information, future events or otherwise, except as required by applicable law.

Use of Proceeds

We currently intend to use the net proceeds from this offering for working capital to fund our clinical programs and general corporate purposes, including the further development of our product candidates. This expected use of proceeds from this offering represents our intentions based upon our current plans and prevailing business conditions, which could change in the future as our plans and prevailing business conditions evolve. The amounts and timing of our use of proceeds will vary depending on a number of factors, including the amount of cash generated or used by our operations. As a result, we will retain broad discretion in the allocation of the net proceeds of this offering.

As of the date of this prospectus, we cannot specify with certainty all of the particular uses for the net proceeds to us from the sale of the securities offered by us hereunder. We will set forth in the applicable prospectus supplement or free writing prospectus our intended use for the net proceeds received from the sale of any securities sold pursuant to the prospectus supplement or free writing prospectus.

Description of Capital Stock

As of the date of this prospectus, our certificate of incorporation, authorizes us to issue up to 500,000,000 shares of Common Stock, $0.001 par value per share, and 15,000,000 shares of preferred stock, $0.001 par value per share. Our Common Stock is registered under Section 12(b) of the Exchange Act and is listed on the Nasdaq under the trading symbol “APVO.” As of February 7, 2025, 1,458,445 shares of Common Stock were outstanding and no shares of preferred stock were outstanding.

The following summary describes the material terms of our capital stock. The summary is qualified in its entirety by reference to our certificate of incorporation and our bylaws.

Common Stock

Voting Rights.

Each holder of our Common Stock is entitled to one vote for each share on all matters submitted to a vote of the stockholders, including the election of directors. Under our amended and restated certificate of incorporation and amended and restated bylaws, our stockholders do not have cumulative voting rights. Because of this, the holders of a majority of the shares of Common Stock entitled to vote in any election of directors can elect all of the directors standing for election, if they should so choose.

Dividends.

Subject to preferences that may be applicable to any then-outstanding shares of preferred stock, holders of Common Stock are entitled to receive ratably those dividends, if any, as may be declared from time to time by our board of directors out of legally available funds.

Liquidation.

In the event of our liquidation, dissolution or winding up, holders of Common Stock will be entitled to share ratably in the net assets legally available for distribution to stockholders after the payment of all of our debts and other liabilities and the satisfaction of any liquidation preference granted to the holders of any then-outstanding shares of preferred stock.

Rights and Preferences.

Each share of Common Stock includes an associated right pursuant to and as set forth in the Rights Agreement that we entered into with Broadridge Corporate Issuer Solutions, Inc. on November 8, 2020 (the “rights agreement”). Each right initially represents the right to purchase from us one one-thousandth of a share of our Series A Junior Participating Preferred Stock, par value $0.001 per share. This right is not exercisable until the occurrence of certain events specified in such rights agreement. The value attributable to these rights, if any, is reflected in the value of our Common Stock. The rights agreement and the rights granted thereunder will expire upon the earliest to occur of (i) the date on which all of such rights are redeemed, (ii) the date on which such rights are exchanged, and (iii) the close of business on October 31, 2025.

Fully Paid and Nonassessable.

All of our outstanding shares of Common Stock are fully paid and nonassessable.

Preferred Stock

Under our certificate of incorporation, our board of directors is authorized by resolution to divide the preferred stock into one or more series and, with respect to each series, to determine the designations, powers, preferences, rights, qualifications, limitations and restrictions thereof, including the dividend rights, conversion or exchange rights, voting rights, redemption rights and terms, liquidation preferences, sinking fund provisions and the number of shares constituting the series. Our board of directors can, without stockholder approval but subject to the terms of our certificate of incorporation, issue preferred stock with voting and other rights that could adversely affect the voting power of the holders of our Common Stock and which could have certain anti-takeover effects. Before we may issue any series of preferred stock, our board of directors will be required to adopt resolutions creating and designating such series of preferred stock.

The following summary of terms of our preferred stock is not complete. You should refer to the provisions of our certificate of incorporation, our bylaws and the resolutions containing the terms of each series of preferred stock, which have been or will be filed with the SEC at or prior to the time of issuance of such series and described in the applicable prospectus supplement. The applicable prospectus supplement may also state that any of the terms set forth herein are inapplicable to such series of preferred stock, provided that the information set forth in such prospectus supplement does not constitute a material change to the information herein such that it alters the nature of the offering or the securities being offered.

We will fix the designations, voting powers, preferences and rights of each series of preferred stock that we issue under this prospectus, as well as the qualifications, limitations or restrictions thereof, in the certificate of designation relating to that series. We will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference herein from reports that we file with the SEC, the form of any certificate of designation that describes the terms of the series of preferred stock we are offering. We will describe in the applicable prospectus supplement the terms of the series of preferred stock being offered, including, to the extent applicable:

If we issue shares of preferred stock under this prospectus, the shares will be fully paid and non-assessable.

The issuance of preferred stock could adversely affect the voting power of holders of Common Stock and reduce the likelihood that common stockholders will receive dividend payments and payments upon liquidation. The issuance could have the effect of decreasing the market price of the Common Stock. The issuance of preferred stock also could have the effect of delaying, deterring or preventing a change in control of us.

Outstanding Options, Restricted Stock Units, and Warrants

Unless otherwise indicated, the number of shares of Common Stock to be outstanding after this offering is based on 1,458,445 shares of common stock outstanding as of February 7, 2025. The number of shares of Common Stock outstanding after this offering excludes:

Warrants

We have an aggregate of 1,671,141 common warrants outstanding from our registered direct and public offerings in August 2023, April 2024 and July 2024 and warrant inducement agreements in November 2023 and December 2024, for which we may receive up to an additional $16.4 million in gross proceeds if exercised.

The exercise price and the number of shares of Common Stock purchasable upon the exercise of the outstanding common warrants are subject to adjustment upon the occurrence of specific events, including stock dividends, stock splits, reclassifications and combinations of our Common Stock. If, at any time the outstanding common warrants are outstanding and a fundamental transaction, and generally including any reorganization, recapitalization or reclassification of our Common Stock, the sale, transfer or other disposition of all or substantially all of our properties or assets, our consolidation or merger with or into another person, the acquisition of more than 50% of our outstanding Common Stock, or any person or group becoming the beneficial owner of 50% of the voting power represented by our outstanding Common Stock, occurs the holders of the outstanding common warrants will be entitled to receive upon exercise of the outstanding common warrants the kind and amount of securities, cash or other property that the holders would have received had they exercised the outstanding common warrants immediately prior to such fundamental transaction, other than one in which a successor entity that is a publicly traded corporation (whose stock is quoted or listed for trading on a national securities exchange, including, but not limited to, the New York Stock Exchange, the NYSE American, the Nasdaq Global Select Market, the Nasdaq Global Market or the Nasdaq Capital Market) assumes the common warrant such that the warrant shall be exercisable for the publicly traded Common Stock of such successor entity. Additionally, as more fully described in the common warrants, at the option of the holders of the common warrants the holder can receive consideration in the same type and form of an amount equal to the Black Scholes value (as defined in the common warrant) of such unexercised common warrants on the date of consummation of such transaction. Except as otherwise provided in the outstanding common warrants or by virtue of the holder’s ownership of shares of our Common Stock, such holder of outstanding common warrants does not have the rights or privileges of a holder of our Common Stock, including any voting rights, until such holder exercises such holder’s outstanding common warrants. The outstanding common warrants provide that the holders of the outstanding common warrants have the right to participate in distributions or dividends paid on our shares of Common Stock.

Stockholder Registration Rights

Certain holders of shares of our Common Stock are entitled to certain rights with respect to registration of such shares under the Securities Act. These shares are referred to as registrable securities. The holders of these registrable securities possess registration rights.

The registration of shares of our Common Stock pursuant to the exercise of registration rights would enable the holders to trade these shares without restriction under the Securities Act when the applicable registration statement is declared effective. We will pay the registration expenses, other than underwriting discounts, selling commissions and stock transfer taxes.

Generally, in an underwritten offering, the managing underwriter, if any, has the right, subject to specified conditions, to limit the number of shares the holders may include.

Lincoln Park Registration Rights

On February 16, 2022, we entered into a Purchase Agreement ("2022 Purchase Agreement") and a Registration Rights Agreement with Lincoln Park (the "Registration Rights Agreement"). The 2022 Purchase Agreement and Registration Rights Agreement replaced the Purchase Agreement and Registration Rights Agreement with Lincoln Park that we entered into on December 20, 2018. Under the 2022 Purchase Agreement, Lincoln Park committed to purchase up to $35.0 million of our common stock over a 36-month period commencing after the satisfaction of certain conditions, which are within our control, as set forth in the 2022 Purchase Agreement. The purchase price per share will be based on prevailing market prices; provided, however, that the prevailing market price is not below $1.00. We agreed to and issued 61 shares of our common stock to Lincoln Park for no cash consideration as an initial fee for its commitment to purchase shares of our common stock under the 2022 Purchase Agreement. The Registration Rights Agreement is expected to expire on February 16, 2025.

Certain Anti-Takeover Provisions of Our Certificate of Incorporation, Our Bylaws, the Delaware General Corporation Law ("DGCL") and our Rights Plan

Delaware Law

We are subject to Section 203 of the DGCL, which prohibits a Delaware corporation from engaging in any business combination with any interested stockholder for a period of three years after the date that such stockholder became an interested stockholder, with the following exceptions:

In general, Section 203 defines a “business combination” to include the following:

In general, Section 203 defines an “interested stockholder” as an entity or person who, together with the person’s affiliates and associates, beneficially owns, or within three years prior to the time of determination of interested stockholder status did own, 15% or more of the outstanding voting stock of the corporation.

Staggered Board; Removal of Directors. Our amended and restated certificate of incorporation provides for our board of directors to be divided into three classes with staggered three-year terms. Only one class of directors is elected at each annual meeting of our stockholders, with the other classes continuing for the remainder of their respective three-year terms. Because our stockholders do not have cumulative voting rights, stockholders holding a majority of the shares of Common Stock outstanding are able to elect all of our directors. Our certificate of incorporation and our bylaws also provide that directors may be removed by the stockholders only for cause upon the vote of 75% of our outstanding Common Stock. Furthermore, the authorized number of directors may be changed only by resolution of the board of directors, and vacancies and newly created directorships on the board of directors may, except as otherwise required by law or determined by the board, only be filled by a majority vote of the directors then serving on the board, even though less than a quorum.

Stockholder Action by Written Consent. Our amended and restated certificate of incorporation and amended and restated bylaws also provide that all stockholder actions must be effected at a duly called meeting of stockholders and eliminates the right of stockholders to act by written consent without a meeting. Our amended and restated bylaws also provide that only our chairman of the board, chief executive officer or the board of directors pursuant to a resolution adopted by a majority of the total number of authorized directors may call a special meeting of stockholders.

Requirements for Advance Notification of Stockholder Nominations, Proposals and Amendments. Our amended and restated bylaws also provide that stockholders seeking to present proposals before a meeting of stockholders to nominate candidates for election as directors at a meeting of stockholders must provide timely advance notice in writing, and specify requirements as to the form and content of a stockholder’s notice. Our certificate of incorporation and bylaws provide that the stockholders cannot amend many of the provisions described above except by a vote of 75% or more of our outstanding Common Stock.

Shareholder Rights Plan. On November 8, 2020, our board of directors adopted a rights plan pursuant to our rights agreement between the Company and Broadridge Corporate Issuer Solutions, Inc., as Rights Agent (as amended, the "Rights Agreement"). The rights plan works by causing substantial dilution to any person or group that acquires beneficial ownership of ten percent (10%) or more of our Common Stock without the approval of our board of directors. As a result, the overall effect of the rights plan and the issuance of the rights pursuant to the rights plan may be to render more difficult or discourage a merger, tender or exchange offer or other business combination involving the Company that is not approved by our board of directors. The rights plan is not intended to interfere with any merger, tender or exchange offer or other business combination approved by our board of directors. The rights plan also does not prevent our board of directors from considering any offer that it considers to be in the best interest of our stockholders.

These provisions are intended to enhance the likelihood of continued stability in the composition of our board of directors and its policies and to discourage coercive takeover practices and inadequate takeover bids. These provisions are also designed to reduce our vulnerability to hostile takeovers and to discourage certain tactics that may be used in proxy fights. However, such provisions could have the effect of discouraging others from making tender offers for our shares and may have the effect of delaying changes in our control or management. As a consequence, these provisions may also inhibit fluctuations in the market price of our stock that could result from actual or rumored takeover attempts. We believe that the benefits of these provisions, including increased protection of our potential ability to negotiate with the proponent of an unfriendly or unsolicited proposal to acquire or restructure our company, outweigh the disadvantages of discouraging takeover proposals, because negotiation of takeover proposals could result in an improvement of their terms.

On November 1, 2024, Aptevo Therapeutics Inc. entered into Amendment No. 4 to the Rights Agreement (the "Amendment"). The Amendment extends the definition of “Final Expiration Date” (as defined in the Rights Agreement) and certain related language in the Rights Agreement to October 31, 2025. The Amendment also changes the definition of “Purchase Price” (as defined in the Rights Agreement) and certain related language in the Rights Agreement to $70 per one one-thousandth of a Preferred Share.

Transfer Agent and Registrar

The transfer agent and registrar for our Common Stock is Broadridge, which can be contacted at 51 Mercedes Way, Edgewood, NY 11717, [email protected], or +1 (720) 378-5591. The transfer agent for any series of preferred stock that we may offer under this prospectus will be named and described in the prospectus supplement for that series.

Listing on the Nasdaq Capital Market

Our Common Stock is listed on the Nasdaq Capital Market under the symbol “APVO.”

DESCRIPTION OF DEBT SECURITIES

We may issue debt securities from time to time, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. While the terms we have summarized below will apply generally to any debt securities that we may offer under this prospectus, we will describe the particular terms of any debt securities that we may offer in more detail in the applicable prospectus supplement. The terms of any debt securities offered under a prospectus supplement may differ from the terms described below. Unless the context requires otherwise, whenever we refer to the indenture, we also are referring to any supplemental indentures that specify the terms of a particular series of debt securities.

We will issue the debt securities under the indenture that we will enter into with the trustee named in the indenture. The indenture will be qualified under the Trust Indenture Act of 1939, as amended, or the Trust Indenture Act. We have filed the form of indenture as an exhibit to the registration statement of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of the debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC.

The following summary of material provisions of the debt securities and the indenture is subject to, and qualified in its entirety by reference to, all of the provisions of the indenture applicable to a particular series of debt securities. We urge you to read the applicable prospectus supplements and any related free writing prospectuses related to the debt securities that we may offer under this prospectus, as well as the complete indenture that contains the terms of the debt securities.

General

The indenture does not limit the amount of debt securities that we may issue. It provides that we may issue debt securities up to the principal amount that we may authorize and may be in any currency or currency unit that we may designate. Except for the limitations on consolidation, merger and sale of all or substantially all of our assets contained in the indenture, the terms of the indenture do not contain any covenants or other provisions designed to give holders of any debt securities protection against changes in our operations, financial condition or transactions involving us.

We may issue the debt securities issued under the indenture as “discount securities,” which means they may be sold at a discount below their stated principal amount. These debt securities, as well as other debt securities that are not issued at a discount, may be issued with “original issue discount,” or OID, for U.S. federal income tax purposes because of interest payment and other characteristics or terms of the debt securities. Material U.S. federal income tax considerations applicable to debt securities issued with OID will be described in more detail in any applicable prospectus supplement.

We will describe in the applicable prospectus supplement the terms of the series of debt securities being offered, including:

Conversion or Exchange Rights

We will set forth in the applicable prospectus supplement the terms on which a series of debt securities may be convertible into or exchangeable for our Common Stock or our other securities. We will include provisions as to settlement upon conversion or exchange and whether conversion or exchange is mandatory, at the option of the holder or at our option. We may include provisions pursuant to which the number of shares of our Common Stock or our other securities that the holders of the series of debt securities receive would be subject to adjustment.

Consolidation, Merger or Sale

Unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, the indenture will not contain any covenant that restricts our ability to merge or consolidate, or sell, convey, transfer or otherwise dispose of our assets as an entirety or substantially as an entirety. However, any successor to or acquirer of such assets (other than a subsidiary of ours) must assume all of our obligations under the indenture or the debt securities, as appropriate.

Events of Default under the Indenture

Unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, the following are events of default under the indenture with respect to any series of debt securities that we may issue:

If an event of default with respect to debt securities of any series occurs and is continuing, other than an event of default specified in the last bullet point above, the trustee or the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series, by notice to us in writing, and to the trustee if notice is given by such holders, may declare the unpaid principal of, premium, if any, and accrued interest, if any, due and payable immediately. If an event of default specified in the last bullet point above occurs with respect to us, the principal amount of and accrued interest, if any, of each issue of debt securities then outstanding shall be due and payable without any notice or other action on the part of the trustee or any holder.

The holders of a majority in principal amount of the outstanding debt securities of an affected series may waive any default or event of default with respect to the series and its consequences, except defaults or events of default regarding payment of principal, premium, if any, or interest, unless we have cured the default or event of default in accordance with the indenture. Any waiver shall cure the default or event of default.

Subject to the terms of the indenture, if an event of default under an indenture shall occur and be continuing, the trustee will be under no obligation to exercise any of its rights or powers under such indenture at the request or direction of any of the holders of the applicable series of debt securities, unless such holders have offered the trustee reasonable indemnity. The holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the

trustee, or exercising any trust or power conferred on the trustee, with respect to the debt securities of that series, provided that:

A holder of the debt securities of any series will have the right to institute a proceeding under the indenture or to appoint a receiver or trustee, or to seek other remedies only if:

These limitations do not apply to a suit instituted by a holder of debt securities if we default in the payment of the principal, premium, if any, or interest on, the debt securities.

We will periodically file statements with the trustee regarding our compliance with specified covenants in the indenture.

Modification of Indenture; Waiver

We and the trustee may change an indenture without the consent of any holders with respect to the specific matters set forth below:

In addition, under the indenture, the rights of holders of a series of debt securities may be changed by us and the trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding debt securities of each series that is affected. However, unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, we and the trustee may make the following changes only with the consent of each holder of any outstanding debt securities affected:

Discharge

Each indenture provides that we can elect to be discharged from our obligations with respect to one or more series of debt securities, except for specified obligations, including obligations to:

In order to exercise our rights to be discharged, we must deposit with the trustee money or government obligations sufficient to pay all the principal of, any premium, if any, and interest on, the debt securities of the series on the dates payments are due.

Form, Exchange and Transfer

We will issue the debt securities of each series only in fully registered form without coupons and, unless we provide otherwise in the applicable prospectus supplement, in denominations of $1,000 and any integral multiple thereof. The indenture provides that we may issue debt securities of a series in temporary or permanent global form and as book-entry securities that will be deposited with, or on behalf of, The Depository Trust Company, or DTC, or another depositary named by us and identified in the applicable prospectus supplement with respect to that series. To the extent the debt securities of a series are issued in global form and as book-entry, a description of terms relating to any book-entry securities will be set forth in the applicable prospectus supplement.

At the option of the holder, subject to the terms of the indenture and the limitations applicable to global securities described in the applicable prospectus supplement, the holder of the debt securities of any series can exchange the debt securities for other debt securities of the same series, in any authorized denomination and of like tenor and aggregate principal amount.

Subject to the terms of the indenture and the limitations applicable to global securities set forth in the applicable prospectus supplement, holders of the debt securities may present the debt securities for exchange or for registration of transfer, duly endorsed or with the form of transfer endorsed thereon duly executed if so required by us or the security registrar, at the office of the security registrar or at the office of any transfer agent designated by us for this purpose. Unless otherwise provided in the debt securities that the holder presents for transfer or exchange, we will impose no service charge for any registration of transfer or exchange, but we may require payment of any taxes or other governmental charges.

We will name in the applicable prospectus supplement the security registrar, and any transfer agent in addition to the security registrar, that we initially designate for any debt securities. We may at any time designate additional transfer agents or rescind the designation of any transfer agent or approve a change in the office through which any transfer agent acts, except that we will be required to maintain a transfer agent in each place of payment for the debt securities of each series.

If we elect to redeem the debt securities of any series, we will not be required to:

Information Concerning the Trustee

The trustee, other than during the occurrence and continuance of an event of default under an indenture, undertakes to perform only those duties as are specifically set forth in the applicable indenture. Upon an event of default under an indenture, the trustee must use the same degree of care as a prudent person would exercise or use in the conduct of his or her own affairs. Subject to this provision, the trustee is under no obligation to exercise any of the powers given it by the indenture at the request of any holder of debt securities unless it is offered reasonable security and indemnity against the costs, expenses and liabilities that it might incur.

We intend to name the indenture trustee for each series of indenture securities in the related prospectus supplement.

Payment and Paying Agents

Unless we otherwise indicate in the applicable prospectus supplement, we will make payment of the interest on any debt securities on any interest payment date to the person in whose name the debt securities, or one or more predecessor securities, are registered at the close of business on the regular record date for the interest.

We will pay principal of and any premium and interest on the debt securities of a particular series at the office of the paying agents designated by us, except that unless we otherwise indicate in the applicable prospectus supplement, we will make interest payments by check that we will mail to the holder or by wire transfer to certain holders. Unless we otherwise indicate in the applicable prospectus supplement, we will designate the corporate trust office of the trustee as our sole paying agent for payments with respect to debt securities of each series. We will name in the applicable prospectus supplement any other paying agents that we initially designate for the debt securities of a particular series. We will maintain a paying agent in each place of payment for the debt securities of a particular series.

All money we pay to a paying agent or the trustee for the payment of the principal of or any premium or interest on any debt securities that remains unclaimed at the end of two years after such principal, premium or interest has become due and payable will be repaid to us, and the holder of the debt security thereafter may look only to us for payment thereof.

Governing Law

The indenture and the debt securities will be governed by and construed in accordance with the internal laws of the State of New York, except to the extent that the Trust Indenture Act is applicable.

Description of Warrants

The following description, together with the additional information we may include in any applicable prospectus supplement and free writing prospectus, summarizes the material terms and provisions of the warrants that we may offer under this prospectus, which may consist of warrants to purchase Common Stock, preferred stock or debt securities and may be issued in one or more series. Warrants may be offered independently or in combination with Common Stock, preferred stock or debt securities offered by any prospectus supplement. While the terms we have summarized below will apply generally to any warrants that we may offer under this prospectus, we will describe the particular terms of any series of warrants in more detail in the applicable prospectus supplement. The following description of warrants will apply to the warrants offered by this prospectus unless we provide otherwise in the applicable prospectus supplement. The applicable prospectus supplement for a particular series of warrants may specify different or additional terms.

We have filed forms of the warrant agreements and forms of warrant certificates containing the terms of the warrants that may be offered as exhibits to the registration statement of which this prospectus is a part. We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of warrant and/or the warrant agreement and warrant certificate, as applicable, that contain the terms of the particular series of warrants we are offering, and any supplemental agreements, before the issuance of such warrants. The following summaries of material terms and provisions of the warrants are subject to, and qualified in their entirety by reference to, all the provisions of the form of warrant and/or the warrant agreement and warrant certificate, as applicable, and any supplemental agreements applicable to a particular series of warrants that we may offer under this prospectus. We urge you to read the applicable prospectus supplement related to the particular series of warrants that we may offer under this prospectus, as well as any related free writing prospectus, and the complete form of warrant and/or the warrant agreement and warrant certificate, as applicable, and any supplemental agreements, that contain the terms of the warrants.

General

We will describe in the applicable prospectus supplement the terms of the series of warrants being offered, including, to the extent applicable:

Before exercising their warrants, holders of warrants will not have any of the rights of holders of the securities purchasable upon such exercise, including:

Exercise of Warrants

Each warrant will entitle the holder to purchase the securities that we specify in the applicable prospectus supplement at the exercise price that we describe in the applicable prospectus supplement. Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants at any time up to the specified time on the expiration date that we set forth in the applicable prospectus supplement. After the close of business on the expiration date, unexercised warrants will become void.

Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants by delivering the warrant or warrant certificate representing the warrants to be exercised together with specified information, and paying the required amount to the warrant agent, if applicable, in immediately available funds, as provided in the applicable prospectus supplement. We will set forth on the reverse side of any warrant certificate and in the applicable prospectus supplement the information that the holder of the warrant will be required to deliver to any warrant agent in connection with the exercise of the warrant.

Upon receipt of payment and the warrant or warrant certificate, as applicable, properly completed and duly executed at the corporate trust office of the warrant agent, if any, or any other office, including ours, indicated in the prospectus supplement, we will, as soon as practicable, issue and deliver the securities purchasable upon such exercise. If fewer than all of the warrants (or the warrants represented by such warrant certificate) are exercised, a new warrant or a new warrant certificate, as applicable, will be issued for the remaining warrants.

Governing Law

Unless we provide otherwise in the applicable prospectus supplement, the warrants and warrant agreements, and any claim, controversy or dispute arising under or related to the warrants or warrant agreements, will be governed by and construed in accordance with the laws of the State of New York.

Enforceability of Rights by Holders of Warrants

Each warrant agent, if any, will act solely as our agent under the applicable warrant agreement and will not assume any obligation or relationship of agency or trust with any holder of any warrant. A single bank or trust company may act as warrant agent for more than one issue of warrants. A warrant agent will have no duty or responsibility in case of any default by us under the applicable warrant agreement or warrant, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a warrant may, without the consent of the related warrant agent or the holder of any other warrant, enforce by appropriate legal action its right to exercise, and receive the securities purchasable upon exercise of, its warrants.

Description of sUBSCRIPTION rIGHTS

We may issue subscription rights to purchase shares of Common Stock, preferred stock, warrants or debt securities, or any combination thereof. These subscription rights may be issued independently or together with any other security offered by us, and they may or may not be transferable by the stockholder receiving the subscription rights in such offering. In connection with any offering of subscription rights, we may enter into a standby arrangement with one or more underwriters or other purchasers pursuant to which the underwriters or other purchasers may be required to purchase any securities remaining unsubscribed for after such offering.

The applicable prospectus supplement will describe the specific terms of any offering of subscription rights for which this prospectus is being delivered, including the following:

The description in the applicable prospectus supplement of any subscription rights we offer will not necessarily be complete and will be qualified in its entirety by reference to the applicable subscription rights certificate or subscription rights agreement, which will be filed with the SEC if we offer subscription rights. For more information on how you can obtain copies of any subscription rights certificate or subscription rights agreement if we offer subscription rights, see “Where You Can Find More Information.” We urge you to read the applicable subscription rights certificate, the applicable subscription rights agreement and any accompanying prospectus supplement in their entirety.

Legal Ownership of Securities

We can issue securities in registered form or in the form of one or more global securities. We describe global securities in greater detail below. We refer to those persons who have securities registered in their own names on the books that we or any applicable trustee, depositary or warrant agent maintain for this purpose as the “holders” of those securities. These persons are the legal holders of the securities. We refer to those persons who, indirectly through others, own beneficial interests in securities that are not registered in their own names, as “indirect holders” of those securities. As we discuss below, indirect holders are not legal holders, and investors in securities issued in book-entry form or in street name will be indirect holders.

Book-Entry Holders

We may issue securities in book-entry form only, as we will specify in the applicable prospectus supplement. This means securities may be represented by one or more global securities registered in the name of a financial institution that holds them as depositary on behalf of other financial institutions that participate in the depositary’s

book-entry system. These participating institutions, which are referred to as participants, in turn, hold beneficial interests in the securities on behalf of themselves or their customers.

Only the person in whose name a security is registered is recognized as the holder of that security. Securities issued in global form will be registered in the name of the depositary or its participants. Consequently, for securities issued in global form, we will recognize only the depositary as the holder of the securities, and we will make all payments on the securities to the depositary. The depositary passes along the payments it receives to its participants, which in turn pass the payments along to their customers who are the beneficial owners. The depositary and its participants do so under agreements they have made with one another or with their customers; they are not obligated to do so under the terms of the securities.

As a result, investors in a global security will not own securities directly. Instead, they will own beneficial interests in a global security, through a bank, broker or other financial institution that participates in the depositary’s book-entry system or holds an interest through a participant. As long as the securities are issued in global form, investors will be indirect holders, and not legal holders, of the securities.

Street Name Holders

We may terminate a global security or issue securities in non-global form. In these cases, investors may choose to hold their securities in their own names or in “street name.” Securities held by an investor in street name would be registered in the name of a bank, broker or other financial institution that the investor chooses, and the investor would hold only a beneficial interest in those securities through an account he or she maintains at that institution.

For securities held in street name, we or any applicable trustee or depositary will recognize only the intermediary banks, brokers and other financial institutions in whose names the securities are registered as the holders of those securities, and we or any applicable trustee or depositary will make all payments on those securities to them. These institutions pass along the payments they receive to their customers who are the beneficial owners, but only because they agree to do so in their customer agreements or because they are legally required to do so. Investors who hold securities in street name will be indirect holders, not holders, of those securities.

Legal Holders

Our obligations, as well as the obligations of any applicable trustee and of any third parties employed by us or a trustee, run only to the legal holders of the securities. We do not have obligations to investors who hold beneficial interests in global securities, in street name or by any other indirect means. This will be the case whether an investor chooses to be an indirect holder of a security or has no choice because we are issuing the securities only in global form.

For example, once we make a payment or give a notice to the legal holder, we have no further responsibility for the payment or notice even if that legal holder is required, under agreements with its participants or customers or by law, to pass it along to the indirect holders but does not do so. Similarly, we may want to obtain the approval of the legal holders to amend an indenture, to relieve us of the consequences of a default or of our obligation to comply with a particular provision of the indenture or for other purposes. In such an event, we would seek approval only from the holders, and not the indirect holders, of the securities. Whether and how the legal holders contact the indirect holders is up to the legal holders.

Special Considerations for Indirect Holders

If you hold securities through a bank, broker or other financial institution, either in book-entry form because the securities are represented by one or more global securities or in street name, you should check with your own institution to find out:

Global Securities

A global security is a security that represents one or any other number of individual securities held by a depositary. Generally, all securities represented by the same global securities will have the same terms.

Each security issued in book-entry form will be represented by a global security that we issue to, deposit with and register in the name of a financial institution or its nominee that we select. The financial institution that we select for this purpose is called the depositary. Unless we specify otherwise in the applicable prospectus supplement, DTC will be the depositary for all securities issued in book-entry form.

A global security may not be transferred to or registered in the name of anyone other than the depositary, its nominee or a successor depositary, unless special termination situations arise. We describe those situations below under “Special Situations When a Global Security Will Be Terminated.” As a result of these arrangements, the depositary, or its nominee, will be the sole registered owner and legal holder of all securities represented by a global security, and investors will be permitted to own only beneficial interests in a global security. Beneficial interests must be held by means of an account with a broker, bank or other financial institution that in turn has an account with the depositary or with another institution that does. Thus, an investor whose security is represented by a global security will not be a legal holder of the security, but only an indirect holder of a beneficial interest in the global security.

If the prospectus supplement for a particular security indicates that the security will be issued in global form only, then the security will be represented by a global security at all times unless and until the global security is terminated. If termination occurs, we may issue the securities through another book-entry clearing system or decide that the securities may no longer be held through any book-entry clearing system.

Special Considerations for Global Securities

The rights of an indirect holder relating to a global security will be governed by the account rules of the investor’s financial institution and of the depositary, as well as general laws relating to securities transfers. We do not recognize an indirect holder as a holder of securities and instead deal only with the depositary that holds the global security.

If securities are issued only in the form of a global security, an investor should be aware of the following:

There may be more than one financial intermediary in the chain of ownership for an investor. We do not monitor and are not responsible for the actions of any of those intermediaries.

Special Situations When a Global Security Will Be Terminated

In a few special situations described below, the global security will terminate and interests in it will be exchanged for physical certificates representing those interests. After that exchange, the choice of whether to hold securities directly or in street name will be up to the investor. Investors must consult their own banks, brokers or other financial institutions to find out how to have their interests in securities transferred to their own name, so that they will be direct holders. We have described the rights of holders and street name investors above.

Unless we provide otherwise in the applicable prospectus supplement, the global security will terminate when the following special situations occur:

The prospectus supplement may also list additional situations for terminating a global security that would apply only to the particular series of securities covered by the applicable prospectus supplement. When a global security terminates, the depositary, and not we or any applicable trustee, is responsible for deciding the names of the institutions that will be the initial direct holders.

Plan of Distribution

We may sell our securities covered by this prospectus in any of three ways (or in any combination):

We may distribute the securities:

Each time we offer and sell securities covered by this prospectus, we will provide a prospectus supplement or supplements that will describe the method of distribution and set forth the terms of the offering, including:

Any public offering price and any discounts or concessions allowed or reallowed or paid to dealers may be changed from time to time. We may determine the price or other terms of the securities offered under this prospectus by use of an electronic auction. We will describe how any auction will determine the price or any other terms, how potential investors may participate in the auction and the nature of the obligations of the underwriter, dealer or agent in the applicable prospectus supplement.

Underwriters or dealers may offer and sell the offered securities from time to time in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale. If underwriters or dealers are used in the sale of any securities, the securities will be acquired by the underwriters or dealers for their own account and may be resold from time to time in one or more transactions described above. The securities may be either offered to the public through underwriting syndicates represented by managing underwriters, or directly by underwriters or dealers. Generally, the underwriters’ or dealers’ obligations to purchase the securities will be subject to certain conditions precedent. The underwriters or dealers will be obligated to purchase all of the securities if they purchase any of the securities, unless otherwise specified in the prospectus supplement. We may use underwriters with whom we have a material relationship. We will describe the nature of any such relationship in the prospectus supplement, naming the underwriter.

We may sell the securities through agents from time to time. The prospectus supplement will name any agent involved in the offer or sale of the securities and any commissions we pay to them. Generally, any agent will be acting on a best efforts basis for the period of its appointment. We may authorize underwriters, dealers or agents to solicit offers by certain purchasers to purchase the securities from us at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future.

The contracts will be subject only to those conditions set forth in the prospectus supplement, and the prospectus supplement will set forth any commissions we pay for solicitation of these contracts.

Agents, dealers and underwriters may be entitled to indemnification by us against certain civil liabilities, including liabilities under the Securities Act, or to contribution with respect to payments which the agents, dealers or underwriters may be required to make in respect thereof. Agents, dealers and underwriters may be customers of, engage in transactions with, or perform services for us in the ordinary course of business.

All securities we may offer, other than Common Stock, will be new issues of securities with no established trading market. Any underwriters may make a market in these securities, but will not be obligated to do so and may discontinue any market making at any time without notice. We cannot guarantee the liquidity of the trading markets for any securities.

Any underwriter may engage in overallotment, stabilizing transactions, short covering transactions and penalty bids in accordance with Regulation M under the Securities Exchange Act of 1934, as amended. Overallotment involves sales in excess of the offering size, which create a short position. This short sales position may involve either “covered” short sales or “naked” short sales. Covered short sales are short sales made in an amount not greater than the underwriters’ over-allotment option to purchase additional securities in this offering described above. The underwriters may close out any covered short position either by exercising their over-allotment option or by purchasing securities in the open market. To determine how they will close the covered short position, the underwriters will consider, among other things, the price of securities available for purchase in the open market, as compared to the price at which they may purchase securities through the over-allotment option. Naked short sales are short sales in excess of the over-allotment option. The underwriters must close out any naked short position by purchasing securities in the open market. A naked short position is more likely to be created if the underwriters are concerned that, in the open market after pricing, there may be downward pressure on the price of the securities that could adversely affect investors who purchase securities in this offering. Stabilizing transactions permit bids to purchase the underlying security for the purpose of fixing the price of the security so long as the stabilizing bids do not exceed a specified maximum. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a covering transaction to cover short positions.

Any underwriters who are qualified market makers on the Nasdaq Capital Market may engage in passive market making transactions in our Common Stock, preferred stock, warrants and debt securities, as applicable, on the Nasdaq Capital Market in accordance with Rule 103 of Regulation M, during the business day prior to the pricing of the offering, before the commencement of offers or sales of the securities. Passive market makers must comply with applicable volume and price limitations and must be identified as passive market makers. In general, a passive market maker must display its bid at a price not in excess of the highest independent bid for such security; if all independent bids are lowered below the passive market maker’s bid, however, the passive market maker’s bid must then be lowered when certain purchase limits are exceeded.

In compliance with guidelines of the Financial Industry Regulatory Authority, or FINRA, the maximum consideration or discount to be received by any FINRA member or independent broker dealer may not exceed 8% of the aggregate amount of the securities offered pursuant to this prospectus and any applicable prospectus supplement.

Similar to other purchase transactions, an underwriter’s purchase to cover the syndicate short sales or to stabilize the market price of our securities may have the effect of raising or maintaining the market price of our securities or preventing or mitigating a decline in the market price of our securities. As a result, the price of our securities may be higher than the price that might otherwise exist in the open market. The imposition of a penalty bid might also have an effect on the price of the securities if it discourages resales of the securities.

Neither we nor the underwriters make any representation or prediction as to the effect that the transactions described above may have on the price of the securities. If such transactions are commenced, they may be discontinued without notice at any time.

Legal Matters

The validity of the securities being offered by this prospectus will be passed upon by Paul Hastings LLP, Washington, DC.

Experts

Our consolidated financial statements as of December 31, 2024 and 2023, and for the years then ended, incorporated in this prospectus by reference and included in our Annual Report on Form 10-K for the year ended December 31, 2024, have been audited by Moss Adams LLP, an independent registered public accounting firm, as stated in their report (which report expresses an unqualified opinion and includes an explanatory paragraph related to a going concern uncertainty), which is incorporated herein by reference. Such consolidated financial statements are incorporated by reference in reliance upon the report of such firm given their authority as experts in accounting and auditing.

Where You Can Find More Information

This prospectus is part of a registration statement we filed with the SEC. This prospectus does not contain all of the information set forth in the registration statement and the exhibits to the registration statement. For further information with respect to us and the securities we are offering under this prospectus, we refer you to the registration statement and the exhibits and schedules filed as a part of the registration statement. Neither we nor any agent, underwriter or dealer has authorized any person to provide you with different information. We are not making an offer of these securities in any state where the offer is not permitted. You should not assume that the information in this prospectus is accurate as of any date other than the date on the front page of this prospectus, regardless of the time of delivery of this prospectus or any sale of the securities offered by this prospectus.

We are subject to the informational requirements of the Securities Exchange Act and are required to file annual, quarterly and current reports, proxy statements and other information with the SEC. Any information we file with the SEC, including the documents incorporated by reference into this prospectus, is also available on the SEC’s website at www.sec.gov. We also make these documents publicly available, free of charge, on our website at www.aptevotherapeutics.com as soon as reasonably practicable after filing such documents with the SEC. The information contained in, or that can be accessed through, our website is not part of this prospectus.

Incorporation of Certain Information by Reference

The SEC allows us to “incorporate by reference” the information we file with it, which means that we can disclose important information to you by referring you to those documents instead of having to repeat the information in this prospectus. The information incorporated by reference is considered to be part of this prospectus, and because we are a smaller reporting company, later information that we file with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below and any future filings (including those made after the initial filing of the registration statement of which this prospectus is a part and prior to the effectiveness of such registration statement) we will make with the SEC under Sections 13(a), 13(c), 14, or 15(d) of the Exchange Act until the termination of the offering of the shares covered by this prospectus (other than information furnished under Item 2.02 or Item 7.01 of Form 8-K):

As a smaller reporting company, we also are incorporating by reference any future information filed (rather than furnished) by us with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, after the date of the initial filing of the registration statement of which this prospectus is a part and before the effective date of the registration statement and after the date of this prospectus until the termination of the offering. Any statements contained in a previously filed document incorporated by reference into this prospectus is deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus, or in a subsequently filed document also incorporated by reference herein, modifies or supersedes that statement.

We will provide to each person, including any beneficial owner, to whom a prospectus is delivered, at no cost, upon written or oral request, a copy of any or all of the reports or documents that have been incorporated by reference in the prospectus contained in the registration statement but not delivered with the prospectus. You should direct requests for documents to:

Aptevo Therapeutics Inc.

2401 4th Avenue, Suite 1050

Seattle, WA 98121

Attn: General Counsel

(206) 838-0500

This prospectus is part of a registration statement we filed with the SEC. That registration statement and the exhibits filed along with the registration statement contain more information about us and the shares in this offering. Because information about documents referred to in this prospectus is not always complete, you should read the full documents which are filed as exhibits to the registration statement. You may read and copy the full registration statement and its exhibits at the SEC’s website.

APTEVO THERAPEUTICS INC.

1,764,710 Shares of Common Stock

PROSPECTUS SUPPLEMENT

April 3, 2025

Roth Capital Partners