Centessa Pharmaceuticals has dosed the first subject in its registrational PRESent-2 (AP-0102) study of SerpinPC to treat haemophilia B without inhibitors.

The international, open-label Phase IIb study is designed to assess the safety and efficacy of activated protein C (APC) inhibitor SerpinPC in male subjects with severe haemophilia A (with or without inhibitors) or moderately severe to severe haemophilia B (without inhibitors).

It includes a randomised dose-justification phase (Part 1), and a dose-confirmatory phase (Part 2), both of which last 24 weeks.

A 24-week extension phase (Part 3) is also included, which will further enrol subjects who have completed either Part 1 or Part 2.

Dosages of SerpinPC will be administered subcutaneously every one, two or four weeks to up to 120 adult or adolescent subjects.

Rate of treated bleeds (expressed as an annualised bleeding rate (ABR)) in the observation period compared with the first 24 weeks treated with SerpinPC is the primary efficacy endpoint.

Centessa Pharmaceuticals’ Development chairman Antoine Yver said: “Based on encouraging clinical data from our ongoing Phase IIa study, we believe SerpinPC has the potential to be a first-in-class subcutaneously administered therapy with a differentiated safety profile for persons with haemophilia B, subject to regulatory review and approval.

“We are excited to be evaluating the potential of SerpinPC’s novel mechanism of action in the registrational PRESent-2 study.

“We expect to enroll and dose additional patients across our clinical trial sites and advance toward the interim analysis planned when 36 subjects reach 12 weeks on treatment in Part 1 of the study.”

Centessa is also planning to initiate its registrational PRESent-3 (AP-0103) study for subjects with haemophilia B with inhibitors and anticipates dosing patients this year.