A potent anti-CD47 antibody decoupling anti-tumor efficacy from hematotoxicity

Blocking the CD47-SIRPα checkpoint reactivates macrophage-driven elimination of malignant cells, although CD47 antagonists have progressed substantially in clinical trials, their implementation is hindered by on-target hematologic toxicity, particularly unintended binding to red blood cells (RBCs). The present study was therefore undertaken to develop a humanized anti-CD47 antibody that achieves robust antitumor activity with an enhanced safety margin.

A humanized anti-CD47 monoclonal antibody was engineered with a functionally silenced IgG4 Fc to reduce Fc effector function. Binding kinetics and species cross-reactivity were quantified by surface plasmon resonance and flow cytometry; functional blockade of CD47-SIRPα interaction was evaluated through hSIRPα competitive blocking and signaling pathway blocking analyses. The antitumor activity was investigated by primary macrophage phagocytosis assays and in vivo efficacy studies utilizing xenograft animal models encompassing hematologic and solid tumor cells. Translational safety was evaluated through ex vivo binding assays on peripheral blood mononuclear cells (PBMCs) and RBCs, hemagglutination assay, and toxicology studies in cynomolgus monkeys, which included maximum tolerated dose (MTD) determination and hematologic monitoring.

A novel humanized anti-CD47 antibody LD002 was engineered. It bound human CD47 with a high affinity (K_D 1.5 nM), thus it effectively suppressed CD47-SIRPα signaling and boosted macrophage-driven phagocytic activity to target tumor cells in vitro. LD002 elicited significant antitumor efficacy against lymphoma and small cell lung cancer xenograft models, achieving 79% tumor growth inhibition (TGI) and 100% complete clearance, respectively, at 3 mg/kg, with good tolerability. Although binding to PBMCs and RBCs was observed, LD002 did not exhibit any dose-dependent hemagglutination, distinguishing it from the benchmark antibody Hu5F9-G4. Moreover, in non-human primates, the single-dose maximum tolerance dose (MTD) reached 744 mg/kg, and repeat-dosing up to 150 mg/kg once weekly revealed no clinically meaningful adverse findings, underscoring a widened therapeutic window and manageable hematologic profile that supports its further clinical development.

LD002 addresses key translational bottlenecks in anti-CD47 therapy by decoupling target blockade from RBCs hemagglutination, thereby largely mitigating hematotoxicity while preserving robust antitumor efficacy. These preclinical data position LD002 as a differentiated, promising CD47 inhibitor with significant translational potential.