CytomX Begins Phase 1 Dosing of CX-801 for Solid Tumors

SOUTH SAN FRANCISCO, Calif., Sept. 09, 2024 – CytomX Therapeutics, Inc. (Nasdaq: CTMX), a prominent name in masked, conditionally activated biologic therapeutics, has announced the administration of the initial dose of CX-801 monotherapy to a patient in a Phase 1 clinical trial (NCT06462794) for individuals with solid tumors. CX-801 represents a dually-masked interferon alpha-2b PROBODY® cytokine, which holds promise for diverse applications in both traditionally immune-reactive and non-reactive (cold) tumors.

The Phase 1 trial for CX-801 is structured to assess safety and initial clinical activity when used as a monotherapy and in conjunction with Merck’s anti-PD-1 therapy, KEYTRUDA® (pembrolizumab). The study will enroll patients with specific solid tumors such as advanced melanoma, renal cell carcinoma, and head and neck squamous cell carcinoma. The aim is to gather data that could lead to Phase 1b studies focusing on specific indications for dose expansion.

Dr. Wayne Chu, Chief Medical Officer at CytomX Therapeutics, remarked, "Interferon-alpha-2b is a potent immune-modulating cytokine that has shown clinical activity in various cancers like metastatic melanoma, renal cancer, and bladder cancer. However, its systemic administration has been limited by significant toxicities. CX-801 leverages CytomX’s leading conditional activation platform to retain its efficacy while potentially reducing its toxicities, aiming to become a key component in immuno-oncology combination treatments."

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

About CytomX Therapeutics:
CytomX Therapeutics is an oncology-focused, clinical-stage biopharmaceutical company dedicated to the development of novel conditionally activated biologics targeted to the tumor environment. Through its innovative PROBODY® therapeutic platform, CytomX aims to develop safer and more effective cancer treatments. Their diverse pipeline includes various therapeutic candidates such as antibody-drug conjugates (ADCs), T-cell engagers, and immune modulators like cytokines.

CytomX's clinical-stage pipeline features 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. This candidate is being co-developed globally with Amgen. Meanwhile, CX-2051 is a conditionally activated ADC aimed at the epithelial cell adhesion molecule, EpCAM, which could be applicable to multiple EpCAM-expressing epithelial cancers. This drug was developed in collaboration with Immunogen, now part of AbbVie. CX-801, a PROBODY® cytokine, is being studied for its broad applicability in both immune-sensitive and immune-insensitive tumors.

CytomX has formed strategic partnerships with several major oncology leaders, including Amgen, Astellas, Bristol Myers Squibb, Regeneron, and Moderna. These collaborations underscore CytomX’s commitment to making conditionally activated treatments a new standard in cancer care. 

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