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

On September 9, 2024 CytomX Therapeutics, Inc. (Nasdaq: CTMX), a leader in the field of masked, conditionally activated biologic therapeutics, reported that the first patient has been dosed with CX-801 monotherapy in a Phase 1 study (NCT06462794) in patients with solid tumors (Press release, CytomX Therapeutics, SEP 9, 2024, View Source [SID1234646428]). 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.

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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