SEC Form S-8 filed by Equillium Inc.

As filed with the Securities and Exchange Commission on September 9, 2025

Registration No. 333-   

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-8

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Equillium, Inc.

(Exact name of registrant as specified in its charter)

2018 Equity Incentive Plan

2018 Employee Stock Purchase Plan

(Full titles of the plans)

Bruce D. Steel

President and Chief Executive Officer

Equillium, Inc.

2223 Avenida de la Playa, Suite 105

La Jolla, California 92037

(Name and Address of agent for service)

(858) 240-1200

(Telephone number, including area code, of agent for service)

With a copy to:

Thomas A. Coll

Cooley LLP

10265 Science Center Drive

San Diego, California 92121

(858) 550-6000

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act:

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

REGISTRATION OF ADDITIONAL SECURITIES

PURSUANT TO GENERAL INSTRUCTION E

This Registration Statement is being filed for the purpose of increasing the number of securities of the same class as other securities for which a Registration Statement of the Registrant on Form S-8 relating to the same employee benefit plans is effective.

The Registrant previously registered shares of its Common Stock for issuance under the Equillium, Inc. 2018 Equity Incentive Plan and the Equillium, Inc. 2018 Employee Stock Purchase Plan under Registration Statements on Form S-8 filed with the Securities and Exchange Commission on October 16, 2018 (File No. 333-227859), March 27, 2019 (File No. 333-230536), as amended on May 24, 2019, March 26, 2020 (File No. 333-237407), March 24, 2021 (File No. 333-254656), March 23, 2022 (File No. 333-263790), January 6, 2023 (File No. 333-269154) and March 25, 2024 (File No. 333-278213) (collectively, the “Prior Registration Statements”). Pursuant to General Instruction E to Form S-8, this Registration Statement hereby incorporates by reference the contents of the Prior Registration Statements.

Item 8. Exhibits.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of La Jolla, State of California, on September 9, 2025.

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below hereby constitutes and appoints Bruce D. Steel and Christine Zedelmayer, and each of them, as his or her true and lawful attorneys-in-fact and agents, with full power of substitution, for him or her in any and all capacities, to sign any and all amendments to this Registration Statement on Form S-8 (including post-effective amendments), and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents full power and authority to do and perform each and every act and thing requisite and necessary to be done in connection therewith, as fully for all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents, or his substitute, may lawfully do or cause to be done by virtue hereof

Pursuant to the requirements of the Securities Act of 1933, this registration statement on Form S-8 has been signed by the following persons in the capacities and on the date indicated.