A Global, Open-label Study to Investigate the Efficacy and Safety of SerpinPC in Subjects With Hemophilia B With Inhibitors (PRESent-3)

Prior treatment

• History of or other evidence of recent alcohol or drug abuse as determined by the Investigator (in the 12 months before screening)
• Current or planned treatment with anticoagulant or antiplatelet drugs
• Patient with previous factor IX inhibitor who responded to immune tolerance induction and remains on prophylactic factor concentrate
• Previous deep vein thrombosis (excluding line-associated thrombosis), pulmonary embolism, myocardial infarction, or stroke
• Participation in another interventional clinical trial (except for AP-0105) during the 30 days before screening
• Ongoing, or planned treatment with gene therapy for HemB

Other illness

• Any major medical, psychological, or psychiatric condition that could cause the subject to be unsuitable for the study or could interfere with the interpretation of the study results
• Any other significant conditions or comorbidities that, in the opinion of the Investigator, would make the subject unsuitable for enrollment, or could interfere with participation in, or completion of the study
• History of intolerance to SC injections
• Uncontrolled hypertension (systolic blood pressure >160 mm Hg; diastolic blood pressure >100 mm Hg)
• Has active cancer and/or requires therapy for cancer, except for basal cell carcinoma

Lab values

• Known HIV infection with CD4 count (or T-cell count) of <200 cells/μL within 24 weeks before Screening and Pre-dosing visits. Patients with HIV infection who have CD4 > 200 and meet all other criteria are eligible

Other

• Known severe thrombophilia (defined as antithrombin deficiency and/or protein S deficiency and/or protein C deficiency)
• Is planning to donate/bank sperm during SerpinPC treatment AND within 30 days of last dose of SerpinPC
• Weight >150 kg OR body mass index >40 kg/m2

• Male subjects ≥12 and ≤65 years of age at the time of informed consent
• Adequate hematologic function, defined as a platelet count of ≥100,000/μL (≥100 × 109/L) and hemoglobin level of ≥10 g/dL (≥100 g/L or ≥ 6.206 mmol/L) at Screening and Pre-dosing visits
• Adequate hepatic function, defined as a total bilirubin level of ≤1.5 × upper level of normal (ULN, excluding Gilbert syndrome) and aspartate aminotransferase and/or alanine aminotransferase of ≤3 × ULN at Screening and Pre-dosing visits; no clinical signs or known laboratory or radiographic evidence consistent with cirrhosis of the liver
• Adequate renal function, defined as a serum creatinine level of ≤2.0 × ULN at Screening and Pre-dosing visits
• Able to use a diary to document bleeding events and medication usage (caregiver assistance allowed for adolescents)
• Sexually active subjects with a partner who could become pregnant should agree to use effective contraception for the duration of the study Effective contraceptive measures include condom with or without spermicide, a combination of male condom with either cap, diaphragm, or sponge with spermicide (double barrier methods), vasectomy, partner using stable contraceptive measures (combined [estrogen and progestogen-containing] hormonal contraception or progestogen-only hormonal contraception initiated 2 or more menstrual cycles prior to screening, intrauterine device [IUD], intrauterine hormone-releasing system [IUS], bilateral tubal ligation), and/or sexual abstinence
• Capable of providing written informed consent (adolescent assent and parental/guardian/legal representative consent when appropriate) for participation and having the opportunity to discuss the study with the Investigator or delegate
• Historically documented HemB (defined as factor IX ≤0.05 IU/mL [≤5%])
• Subjects who are currently in a prophylaxis program must be willing to stop prophylaxis (including episodic prophylaxis for sporting events) before the first dose of SerpinPC
• Historical or ongoing factor IX inhibitor requiring current treatment with bypass agents based on medical records or laboratory reports
• Documented ABR of ≥6 in the 12 months before screening (subjects not on prophylaxis regimen) or documented ABR of ≥2 for subjects on prophylaxis regimen
• At least 12 weeks of prospective documentation of bleeding episodes in the AP-0105 non-interventional study before SerpinPC dosing, or willing to complete a 12-week observational period (at minimum) in AP-0103
• No bleeding in the 7 days before Baseline (the prospective observation period can be extended if there is an ongoing active bleed)
• D-dimer of ≤750 μg/L; in cases where there is a resolving bleed, the exclusion threshold is ≤1750 mg/L at Screening and Pre-dosing visits