Compass Therapeutics, Inc. 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. Data highlights from the poster presentation include: 19 patients were treated in the dose escalation and 60 patients were treated in the expansion portion of the monotherapy arm of the study (62% were male, median age of 66 years).

A complete response (CR) was confirmed by PET scan in 1 of 3 patients with small-cell lung cancer. This patient, treated in the third-line setting, had a durable Partial Response (PR) for approximately 3 years prior to converting to a CR. Four additional PRs were also observed: 3 of 11 (27.3%) patients with melanoma and 1 of 4 (25%) patients with mesothelioma.

CTX-471 monotherapy was observed to be generally well-tolerated, with the majority of adverse events (AEs) being Grade 1-2. CTX-471 is a fully human monoclonal antibody that binds and activates a novel epitope of the co-stimulatory receptor CD137, also known as 4-1BB, a member of the tumor necrosis factor receptor superfamily. The antibody is currently being evaluated in a Phase 1b clinical trial in patients with solid tumors that have progressed after at least three months on an approved PD-1 or PD-L1 inhibitor. Initial results reported from a monotherapy cohort of the study included partial responses in melanoma, small cell lung cancer, and mesothelioma, and CTX-471 has been observed to be generally well tolerated.

In preclinical studies, CTX-471 has demonstrated potent monotherapy activity against multiple syngeneic tumor models, including the generation of long-term functional immunological memory.