A new trial will evaluate the efficacy, safety, tolerability, and pharmacokinetics of prophylactic SerpinPC in patients with severe hemophilia A or moderately severe to severe hemophilia B. The trial is part of the SerpinPC registration program and is not yet recruiting.

One hundred twenty male participants aged 12 to 65 years will be enrolled. The eligible participants must be included in a prophylaxis program and willing to cease prophylaxis before the first dose of SerpinPC or be undergoing an on-demand treatment regimen due to at least 6 documented acute bleeding episodes in 6 months before screening and willing to remain in the same program for the duration of the observational period.

The eligibility criteria also include the absence of bleeding 7 days before baseline, D-dimer 750 μg/L or less, adequate hematologic, hepatic, and renal function evidenced by relevant laboratory testing, as well as effective contraception use for the duration of the study.

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Patients with severe thrombophilia, previous factor VIII, or factor IX inhibitor who responded to immune tolerance induction, deep vein thrombosis, pulmonary embolism, myocardial infarction, stroke, uncontrolled hypertension, cancer, HIV infection with CD4 count of less than 200 cells/μL, alcohol or drug use, intolerance to subcutaneous injections, emicizumab treatment in the 24 weeks before baseline, gene hemophilia therapy, anticoagulant or antiplatelet drugs treatment, weight over 150 kg, or body mass index over 40 will be excluded from the study.

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This study consists of 3 parts: part 1 will be a dose-justification phase, part 2 will be a dose-confirmatory phase, and part 3 will be an extension phase for participants who complete part 1 or part 2.  

In part 1, participants will receive 1.2 mg/kg of SerpinPC administered as a subcutaneous injection for 24 weeks after a minimum of 12 weeks of observation. The 3 cohorts will receive the medication once per week, once per 2 weeks, and once per 4 weeks.

In part 2, participants will receive 1.2 mg/kg of SerpinPC once every 2 weeks for a total of 24 weeks. If the interim analysis indicates a greater benefit-risk profile with once per week or once per 4 weeks treatment regimens, the dosing plan will be altered.

In part 3, patients will proceed with SerpinPC treatment at the dosing regimen established in part 2 in a 24-week extension phase.

The study authors will monitor the annualized bleeding rate for treated bleeds up to week 24 as the primary outcome measure. Annualized bleeding rate for treated bleeds up to week 48 as well as treated spontaneous bleeds and treated spontaneous joint bleeds, total coagulation factor and/or bypass product consumption during parts 2 and 3, plasma concentrations of SerpinPC, number of participants with adverse events, and specific quality of life will be assessed as secondary outcome measures.

The study is set to start on June 30, 2023, with the estimated study completion date as June 5, 2026.


The efficacy and safety of serpinPC in participants with severe hemophilia A or moderately severe to severe hemophilia B (PRESent-2). ClinicalTrials.gov. March 29, 2023. Accessed April 4, 2023.