On November 4, 2025 CytomX Therapeutics, Inc. (Nasdaq: CTMX), a leader in the field of masked, conditionally activated biologics, reported that initial translational data from the ongoing Phase 1 study of CX-801 in patients with advanced melanoma will be presented at the Society for Immunotherapy of Cancer (SITC) (Free SITC Whitepaper) 40th Anniversary Annual Meeting, being held in National Harbor, MD on November 7-9, 2025.
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"CX-801 was intentionally designed to unlock the powerful immune-modulating effects of interferon alpha-2b by leveraging our PROBODY therapeutic platform. We are excited to share initial Phase 1 biomarker data for CX-801 which suggest the molecule is working as designed by inducing tumor-localized activation of immune cell populations and interferon-stimulated genes in paired tumor biopsies, including PD-1 and PD-L1," said Marcia Belvin, Ph.D. SVP, chief scientific officer of CytomX Therapeutics.
"We are pleased with the Phase 1 progress for CX-801 to-date, including initial evidence that CX-801 is generally well tolerated and can modulate the immune tumor microenvironment in patients with metastatic melanoma refractory to prior immune checkpoint inhibitor therapy. These initial data support the rationale for the ongoing Phase 1 combination study of CX-801 combined with KEYTRUDA in melanoma, an area of significant unmet need. We look forward to providing Phase 1 clinical data of CX-801 combined with KEYTRUDA in 2026," said Dr. 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
Details for CytomX Therapeutics Presentations at SITC (Free SITC Whitepaper) 2025
CX-801 poster presentation:
Presentation Title: Pharmacodynamic Activity of CX-801, a Masked IFNα2b PROBODY Cytokine, in Patients with Advanced Melanoma
Abstract Number: 606
Session Date and Time: Saturday, November 8, 2025, 5:10 pm – 6:35 pm ET
Preclinical Masked T-cell Engager Targeting CDH3:
Presentation Title: CX-908, a PROBODY T Cell Engager Targeting CDH3 and CD3, Induces Tumor Regressions and Improves the Therapeutic Window in Preclinical Studies
Abstract Number: 961
Session Date and Time: Friday, November 7, 2025, 5:35 pm – 7:00 pm ET
(Press release, CytomX Therapeutics, NOV 4, 2025, View Source [SID1234659350])