Compass Therapeutics to Present Phase 1 Data for CTX-471, A Novel CD137 Agonist Antibody, Demonstrating Anti-Tumor Activity in Patients Who Have Progressed on Approved PD-1 or PD-L1 Inhibitors at the American Society of Clinical Oncology (ASCO) Annual Mee

• CTX-471, a novel anti-CD137 agonist antibody, demonstrated anti-tumor activity in the Company’s Phase 1 Dose Escalation and Dose Expansion, first-in-human monotherapy study in patients with metastatic or locally advanced malignancies who had progressed on approved PD-1 or PD-L1 inhibitors.
• Five clinical responses were observed, all in patients who previously received checkpoint inhibitors. A durable partial response (PR) in a patient with small-cell lung cancer (SCLC) converted to a complete response, as confirmed by PET scan. Four additional PRs were also observed, 3 of 11 (27.3%) patients with melanoma (2 confirmed, one unconfirmed) and one of four (25%) patients with mesothelioma (PR confirmed).
• CTX-471 was well tolerated. The dose-limiting toxicity in the dose-escalation portion of the study was thrombocytopenia (decreased platelet count). These two episodes both resolved to normal. There was a low incidence of liver toxicity (6.3%), and the majority (80%) of adverse events were low grade (Grade 1 or Grade 2).

BOSTON, May 23, 2024 (GLOBE NEWSWIRE) -- Compass Therapeutics, Inc. (Nasdaq: CMPX), a clinical-stage, oncology-focused biopharmaceutical company developing proprietary antibody-based therapeutics to treat multiple human diseases, today announced an upcoming poster presentation of its novel anti-CD137 agonist antibody, CTX-471, in patients with progressive disease following PD-1/PD-L1 inhibitors in metastatic or locally advanced malignancies.

The Company’s Phase 1 open-label, first-in-human study evaluated CTX-471 as a monotherapy in patients with metastatic or locally advanced malignancies that have progressed while receiving an approved PD-1 or PD-L1 inhibitor. The monotherapy portion of this study had two parts: a Dose Escalation phase and a Dose Expansion phase. Monotherapy dose escalation ranged from 0.1–1.2mg/kg intravenous (IV) biweekly, while Dose Expansion explored two dose levels: 0.3 and 0.6 mg/kg. The primary objective was to evaluate the safety and tolerability of CTX-471, with secondary objectives including pharmacokinetics (PK), immunogenicity, and clinical activity.

“We continue to make great strides with our CTX-471 clinical program, and we are excited to report data from the monotherapy arm of our Phase 1 trial,” said Thomas Schuetz, M.D., Ph.D., Co-founder, President of R&D, and Vice Chairman of the board at Compass. “CTX-471 was well tolerated with a low level of liver toxicity, suggesting a differentiated safety profile compared with other CD137-targeted agents. Importantly, a patient with refractory small-cell lung cancer, who had a durable partial response for 3 years, converted to a PET-negative complete response. We observed four additional partial responses, 3 patients with melanoma and one patient with mesothelioma. The clinical responses observed to date demonstrate the potential of our novel anti-CD137 antibody in patients with advanced malignancies who have limited treatment options.”