Ambrx presents anti-PSMA ADC, ARX517, data in patients with prostate cancer

Ambrx Biopharma announced "encouraging" initial data from its ongoing Phase 1 trial APEX-01 investigating ARX517, Ambrx’s proprietary anti-PSMA ADC, in prostate cancer patients. APEX-01 is a Phase 1, first-in-human, open label dose escalation and dose expansion trial enrolling patients with advanced prostate cancer whose tumors have progressed on at least two prior FDA-approved treatments. APEX-01 is the only ongoing clinical trial in the United States targeting PSMA with an ADC. APEX-01 opened for enrollment July 2021 and this is the first data being reported in the study. In the Phase 1 dose-escalation portion of the study, ascending dose levels of ARX517 is administered as a single agent every 3 weeks. The primary endpoints are safety, tolerability and pharmacokinetics. The key secondary endpoint is objective decline of prostate-specific antigen from baseline and/or tumor shrinkage. PSA is a protein produced by the prostate gland and is commonly used as a biomarker to diagnose and follow prostate cancer. A = 50% reduction in PSA levels from baseline is considered clinically relevant and has been shown to correlate with improved overall survival in prostate cancer."The preliminary data from patients with prostate cancer are highly encouraging," said Dr. Michael Schweizer, MD, an Investigator on APEX-01 and Associate Professor Division of Medical Oncology, Fred Hutchinson Cancer Research Center. "Seeing a greater than 50% reduction in PSA levels in three of three patients at the 2.0 mg/kg dose level in this patient population is impressive, and ARX517 appears to be well tolerated so far. I am very optimistic for its future development. We look forward to more data from APEX-01, as the dose escalation continues in this difficult-to-treat patient population." ..