CytomX Therapeutics Announces First Patient Dosed with CX-801, a Dually-Masked Interferon-Alpha 2b PROBODY®, in a Phase 1 Study in Patients with Solid Tumors

SOUTH SAN FRANCISCO, Calif., Sept. 09, 2024 (GLOBE NEWSWIRE) -- CytomX Therapeutics, Inc. (NASDAQ:CTMX), a leader in the field of masked, conditionally activated biologic therapeutics, today announced that the first patient has been dosed with CX-801 monotherapy in a Phase 1 study (NCT06462794) in patients with solid tumors. CX-801 is a dually-masked interferon alpha-2b PROBODY® cytokine with potential broad applicability in both traditionally immune-oncology sensitive as well as insensitive (cold) tumors.

The CX-801 Phase 1 dose escalation study is designed to evaluate safety and signs of clinical activity for CX-801 as monotherapy and in combination with Merck's (known as MSD outside of the US and Canada) anti-PD-1 therapy KEYTRUDA® (pembrolizumab). In dose escalation, the Phase 1 study will enroll patients with select solid tumors including advanced melanoma, renal cell carcinoma, and head and neck squamous cell carcinoma to inform a potential decision to move into Phase 1b indication-specific dose expansion cohorts.

"Interferon-alpha-2b is a powerful immune-modulating cytokine that has demonstrated clinical activity in multiple cancer types such as metastatic melanoma, renal cancer and bladder cancer but its clinical benefit has been limited by significant toxicities when administered systemically. CX-801 utilizes CytomX's industry leading conditional activation platform to maintain potency and expand interferon's therapeutic index to potentially become a foundational component of immuno-oncology combination regimens," said Wayne Chu, M.D., chief medical officer of CytomX Therapeutics.

KEYTRUDA® is a registered trademark of Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA

About CytomX Therapeutics.

CytomX is a clinical-stage, oncology-focused biopharmaceutical company focused on developing novel conditionally activated biologics designed to be localized to the tumor microenvironment. By pioneering a novel pipeline of localized biologics, powered by its PROBODY^® therapeutic platform, CytomX's vision is to create safer, more effective therapies for the treatment of cancer. CytomX's robust and differentiated pipeline comprises therapeutic candidates across multiple treatment modalities including antibody-drug conjugates ("ADCs"), T-cell engagers, and immune modulators such as cytokines. CytomX's clinical-stage pipeline includes CX-904, CX-2051 and CX-801. CX-904 is a conditionally activated T-cell-engaging bispecific antibody targeting the epidermal growth factor receptor (EGFR) on tumor cells and the CD3 receptor on T cells. CX-904 is partnered with Amgen in a global co-development alliance. CX-2051 is a conditionally activated ADC directed toward epithelial cell adhesion molecule, EpCAM, with potential applicability across multiple EpCAM-expressing epithelial cancers. CX-2051 was discovered in collaboration with Immunogen, now part of AbbVie. CX-801 is an interferon alpha-2b PROBODY^® cytokine with broad potential applicability in traditionally immuno-oncology sensitive as well as insensitive (cold) tumors. CytomX has established strategic collaborations with multiple leaders in oncology, including Amgen, Astellas, Bristol Myers Squibb, Regeneron and Moderna. For more information about CytomX and how it is working to make conditionally activated treatments the new standard-of-care in the fight against cancer, visit www.cytomx.com and follow us on LinkedIn and X (formerly Twitter).

CytomX Therapeutics Forward-Looking Statements

This press release includes forward-looking statements. Such forward-looking statements involve known and unknown risks, uncertainties and other important factors that are difficult to predict, may be beyond our control, and may cause the actual results, performance, or achievements to be materially different from any future results, performance or achievements expressed or implied in such statements, including those related to the future potential of partnerships or collaboration agreements. Accordingly, you should not rely on any of these forward-looking statements, including those relating to the potential benefits, safety and efficacy or progress of CytomX's or any of its collaborative partners' product candidates, including CX-801, CX-904, and CX-2051, the potential benefits or applications of CytomX's PROBODY^® therapeutic platform, CytomX's or its collaborative partners' ability to develop and advance product candidates into and successfully complete clinical trials, including the ongoing and planned clinical trials of CX-801, and the timing of initial and ongoing data availability for CX-801, and other development milestones. Risks and uncertainties that contribute to the uncertain nature of the forward-looking statements include: the unproven nature of CytomX's novel PROBODY^® therapeutic technology; CytomX's clinical trial product candidates are in the initial stages of clinical development and its other product candidates are currently in preclinical development, and the process by which preclinical and clinical development could potentially lead to an approved product is long and subject to significant risks and uncertainties, including the possibility that the results of preclinical research and early clinical trials, including initial CX-904 results, may not be predictive of future results; the possibility that CytomX's clinical trials will not be successful; the possibility that current preclinical research may not result in additional product candidates; CytomX's dependence on the success of CX-904 CX-2051 and CX-801; CytomX's reliance on third parties for the manufacture of the Company's product candidates; possible regulatory developments in the United States and foreign countries; and the risk that we may incur higher costs than expected for research and development or unexpected costs and expenses. Additional applicable risks and uncertainties include those relating to our preclinical research and development, clinical development, and other risks identified under the heading "Risk Factors" included in CytomX's Quarterly Report on Form 10-Q filed with the SEC on August 8, 2024. The forward-looking statements contained in this press release are based on information currently available to CytomX and speak only as of the date on which they are made. CytomX does not undertake and specifically disclaims any obligation to update any forward-looking statements, whether as a result of any new information, future events, changed circumstances or otherwise.

PROBODY is a U.S. registered trademark of CytomX Therapeutics, Inc.

Company Contact:

Chris Ogden

Chief Financial Officer

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Investor Contact:

Precision AQ (formerly Stern Investor Relations)

Stephanie Ascher

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Media Contact:

Redhouse Communications

Teri Dahlman

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