Pfizer Tests Novel CD47-PD-L1 Bispecific Antibody in Advanced Solid Tumors
A first-in-human Phase 1 trial evaluates PF-07257876, a dual-checkpoint bispecific antibody targeting both CD47 and PD-L1, in hard-to-treat cancers.
Summary
Pfizer completed a Phase 1 trial testing PF-07257876, a novel bispecific antibody that simultaneously blocks two immune evasion signals used by tumors — CD47 (the 'don't eat me' signal) and PD-L1 (a brake on T-cell activity). The study enrolled 29 participants with advanced non-small cell lung cancer, head and neck squamous cell carcinoma, or ovarian cancer who had no remaining standard treatment options. The trial followed a standard dose-escalation design to find the safest effective dose, then expanded at that dose to assess preliminary efficacy. This dual-targeting approach could amplify immune attack on tumors more effectively than single-checkpoint therapies alone. Full safety and efficacy data from the completed trial have not yet been published.
Detailed Summary
Cancer cells are remarkably skilled at hiding from the immune system, deploying molecular signals that tell immune cells to stand down. Two of the most important of these signals are CD47, which prevents macrophages from engulfing tumor cells, and PD-L1, which suppresses T-cell activity. Blocking either pathway individually has driven major advances in oncology — but tumors often find ways around a single blockade. PF-07257876 is designed to inhibit both simultaneously with a single bispecific antibody molecule, potentially delivering a more comprehensive immune attack.
Pfizer initiated this first-in-human Phase 1 open-label study in August 2021, enrolling 29 participants across multiple centers. Eligible patients had advanced or metastatic non-small cell lung cancer, head and neck squamous cell carcinoma, or ovarian cancer, with no remaining standard therapeutic options. The study proceeded in two parts: dose escalation to identify a recommended dose, followed by dose expansion in selected tumor types at that dose.
The primary objectives centered on safety and tolerability, with secondary goals including pharmacokinetic profiling, pharmacodynamic assessment, and early signals of clinical benefit. The trial was completed in October 2023, meaning full datasets are in analysis but not yet publicly reported in peer-reviewed literature.
The scientific rationale is compelling. CD47-PD-L1 bispecifics theoretically engage both innate immunity (macrophages) and adaptive immunity (T cells) against tumors. Early preclinical work suggested synergistic effects beyond what either target alone can achieve. If confirmed clinically, this could represent a meaningful step forward for patients with immunologically resistant tumors.
However, important caveats apply. This summary is based solely on the ClinicalTrials.gov registration and abstract; no efficacy or safety outcome data are available. With only 29 participants enrolled, the study was designed primarily for safety signal detection, not to demonstrate efficacy. Full publication of results is necessary before drawing clinical conclusions.
Key Findings
- PF-07257876 simultaneously blocks CD47 and PD-L1, targeting both innate and adaptive immune evasion in tumors.
- Phase 1 trial enrolled 29 patients with advanced NSCLC, head and neck, or ovarian cancers with no remaining options.
- Two-part design: dose escalation to find safe recommended dose, then expansion in selected tumor types.
- Trial is completed (Oct 2023) but safety and efficacy results have not yet been publicly reported.
- Dual-checkpoint bispecific strategy could overcome resistance seen with single-agent checkpoint inhibitors.
Methodology
This was a first-in-human, Phase 1, open-label, multicenter, dose-escalation and dose-expansion study sponsored by Pfizer. Part 1 identified the recommended dose via escalation; Part 2 expanded enrollment at that dose in selected tumor types. Twenty-nine participants were enrolled across three advanced cancer indications.
Study Limitations
This summary is based on the ClinicalTrials.gov registration abstract only, as the full study results have not been published in peer-reviewed literature. With only 29 participants, the trial was powered for safety assessment, not efficacy conclusions. No outcome data — including response rates, progression-free survival, or adverse event profiles — are currently available for evaluation.
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