CytomX Therapeutics Announces Clinical Collaboration with Merck to Evaluate CX-801 in Combination with KEYTRUDA® (pembrolizumab)

- CX-801 is a dually masked, conditionally activated IFNα2b cytokine designed using the CytomX Probody® Therapeutic Platform -

                  - Phase 1 first-in-human study expected to start in first half of 2024 -

- Clinical trial will evaluate CX-801 as monotherapy and in combination with KEYTRUDA in patients with advanced metastatic solid tumors including melanoma, renal cell carcinoma and head and neck squamous cell carcinoma -

SOUTH SAN FRANCISCO, Calif., May 07, 2024 (GLOBE NEWSWIRE) -- CytomX Therapeutics, Inc.  (Nasdaq: CTMX), a leader in the field of masked, conditionally activated biologics, today announced that it has entered into a clinical trial collaboration and supply agreement with Merck (known as MSD outside of the US and Canada) for CytomX’s first-in-human Phase 1 clinical trial assessing the clinical activity of CX-801, a dually-masked interferon-alpha2b cytokine in combination with Merck’s anti-PD-1 therapy KEYTRUDA® (pembrolizumab).

“Interferon-alpha-2b is a potent cytokine with demonstrated clinical activity against multiple cancer types, but its use has been limited by systemic toxicities. CX-801 is designed to overcome these limitations to unlock the full potential of interferon in activating the immune tumor microenvironment. With an improved therapeutic profile, our goal is to establish CX-801 as a cornerstone of immuno-oncology combination regimens, including in combination with checkpoint inhibitors such as Keytruda, for the treatment of a broad range of tumor types,” said Wayne Chu, M.D., chief medical officer of CytomX Therapeutics.

“CytomX is excited to be entering into this agreement with Merck to utilize Keytruda in combination with CX-801. The product design principles behind CX-801 integrate over a decade of continuous innovation and experience at CytomX in masking potent biologic therapies. The mechanistic combination of CX-801 and Keytruda is compelling and has potential to be a highly effective regimen to significantly improve the outcomes of patients with cancer,” said Sean McCarthy, D.Phil., chief executive officer and chairman of CytomX Therapeutics.

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

About CX-801
Interferon-alpha 2b is an immunotherapeutic cytokine that has demonstrated clinical activity and gained regulatory approval previously in multiple cancer types. IFNα2b provides a potentially superior approach to activating anti-tumor immune responses compared to other cytokines. CX-801 is a dually masked, conditionally activated IFNα2b cytokine that has the potential to become a cornerstone of combination therapy for a wide range of tumor types, including in traditionally immuno-oncology sensitive as well as insensitive (cold) tumors. Phase 1 initiation for CX-801 solid tumors including melanoma, renal, and head and neck squamous cell carcinoma anticipated in the first half of 2024. Further details on the design and preclinical optimization of CX-801 can be found here:

Link to 2023 SITC poster

About CytomX Therapeutics
CytomX is a clinical-stage, oncology-focused biopharmaceutical company focused on developing novel conditionally activated, masked 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 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-904, CX-2051, and CX-801,, 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-904, and the timing of the commencement of clinical trials or initial and ongoing data availability for CX-801 and CX-2051, 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 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-801, and CX-2051; our reliance on collaboration partners; 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 Annual Report on Form 10-K filed with the SEC on March 11, 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.

CytomX Investor Contact:
Chris Ogden
SVP, Finance and Accounting

CytomX Investor and Media Contact:
Stern Investor Relations
Stephanie Ascher

Media Contact:
Redhouse Communications
Teri Dahlman

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