Pfizer's CD47 Inhibitor PF-07901801 (TTI-622) Receives IND Approval in China for Advanced Hematologic Malignancies

Recently, the CDE official website showed that Pfizer's PF-07901801 injection clinical trial application received approval from the pharmaceutical regulatory authority, intended for treating patients with advanced hematologic malignancies.

CD47, also known as integrin-associated protein, is a widely expressed transmembrane glycoprotein. Tumor cells can express CD47, which binds to the signal regulatory protein α (SIRPα) on the surface of macrophages, sending a "Do not eat me" signal to escape attacks from the body's immune system.

PF-07901801 (TTI-622) is an SIRPα Fc fusion protein that can enhance the phagocytosis of tumor cells and anti-tumor activity of macrophages by blocking the inhibitory signal transmitted by CD47 and generating a moderate pro-phagocytic signal via IgG4 Fc. In August 2021, Pfizer acquired this product as part of its $2.26 billion acquisition of Trillium Therapeutics.

The serious clinical side effects of the first-generation CD47 drugs are mainly hematological adverse reactions, including decreased red blood cell and platelet counts. To address the safety concerns of the first-generation CD47 drugs, Trillium adopted an antibody design strategy that reduces the binding ability of CD47 drugs to red blood cells, thereby avoiding damage to red blood cells.

Currently, multiple clinical studies on the use of PF-07901801 for the treatment of hematologic malignancies and solid tumors have progressed to Phase II. Results from a multicenter, Phase Ia/Ib dose-escalation (NCT03530683) study showed that in patients with refractory or relapsed (r/r) lymphoma, the objective response rate (ORR) was 33% (9/27) in those receiving TTI-622 monotherapy at doses ranging from 0.8 to 8.0 mg/kg. Additionally, the ORR in the 8.0 mg/kg TTI-622 dose group was 50% (3/6).

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