CytomX Therapeutics Announces Positive Initial Phase 1a Dose Escalation Data for Monotherapy CX-904 (EGFRxCD3 PROBODY T-Cell Engager)

- CX-904 demonstrated a favorable safety profile with no cytokine release syndrome (CRS) of any grade observed in step-dosing cohorts and no grade >1 CRS observed overall -

- Encouraging initial signs of efficacy observed for CX-904 in advanced pancreatic cancer, including 2 of 6 patients (33%) with a confirmed partial response and all 6 patients (100%) with disease control -

- Preliminary pharmacokinetic and pharmacodynamic analyses are supportive of PROBODY T-Cell Engager platform mechanism of action -

- Dose escalation and optimization continue -

  - Management to hold conference call today at 5 p.m. EDT / 2 p.m. PDT -

SOUTH SAN FRANCISCO, Calif., May 08, 2024 (GLOBE NEWSWIRE) -- CytomX Therapeutics, Inc. (Nasdaq: CTMX), a leader in the field of masked, conditionally activated biologic therapeutics, today announced positive initial data from the ongoing CX-904 Phase 1a dose escalation clinical study, demonstrating a favorable safety profile and confirmed anti-cancer activity. CX-904 is an investigational, masked, conditionally activated PROBODY T-cell engager designed to target the epidermal growth factor receptor (EGFR) on cancer cells and the CD3 receptor on T cells within the tumor microenvironment.

“We are delighted to share these initial results today for CX-904, a highly innovative masked T-cell engager that embodies our vision at CytomX of transforming lives with safer, more effective therapies,” said Sean McCarthy, D.Phil., chief executive officer and chairman of CytomX. “These data build on more than a decade of innovation at CytomX, and, we believe, open broad new possibilities for T-cell engagers across many targets and cancer types. For EGFR specifically, a target that is present on normal epithelial tissues, we are very encouraged to see CX-904 working as designed by eliciting meaningful tumor reductions in a very difficult to treat tumor type and with a favorable overall safety profile. We look forward to continuing to explore the potential of this exciting agent in multiple EGFR positive cancers and to determining longer term strategy with our global development partner, Amgen.”

As of the April 16, 2024 data cutoff, the Phase 1 study had enrolled 35 patients with advanced metastatic solid tumor types that are generally known to express EGFR, including pancreatic, colorectal (CRC), non-small cell lung cancer (NSCLC), head and neck squamous cell carcinoma (HNSCC), gastric, and esophageal cancers. Patients enrolled in the study were heavily pre-treated and had a median of 4 prior lines of therapy. As of the data cutoff, 19 patients were enrolled into initial non-step dosing cohorts with target doses ranging from 0.007 mg to 6 mg, and 16 patients were subsequently enrolled into step-dosing cohorts with target doses ranging from 5 mg to 10 mg and with tocilizumab prophylaxis. Enrollment into a cohort with a target dose of 15 mg is ongoing.