Efficacy and Safety of Human Protein C Concentrate in Japanese Patients With Severe Congenital Protein C Deficiency.

BACKGROUND: Severe congenital protein C deficiency (SCPCD) is a rare disorder associated with life-threatening thrombotic complications. Protein C concentrate is recommended for both acute and long-term management of SCPCD. However, no efficacy and safety data in Japanese patients have been reported. METHODS: In this extension phase of an open-label, phase 1/2 clinical trial (ClinicalTrials.gov: NCT04984889), Japanese patients with SCPCD could receive intravenous protein C concentrate for on-demand treatment, short-term prophylaxis, or long-term prophylaxis. Efficacy of on-demand treatment was assessed using a predefined efficacy evaluation scale. For prophylaxis, efficacy was assessed based on the occurrence of purpura fulminans and thromboembolic complications during prophylaxis treatment. Safety was evaluated by recording adverse events (AEs). RESULTS: All five patients who completed the pharmacokinetics phase of the study participated in this extension phase (mean [SD] age: 15.2 [8.9] years). At data cutoff, four patients had received eight on-demand treatments of protein C concentrate for purpura fulminans; all were rated as effective. Protein C concentrate was administered for short-term prophylaxis in one patient undergoing tooth extraction, with no thromboembolic complications observed. Six AEs were reported in three patients who received on-demand treatment; none were treatment-related. No AEs were observed during short-term prophylaxis. There were no deaths or AEs leading to treatment discontinuation. CONCLUSIONS: Protein C concentrate was effective for on-demand treatment and short-term prophylaxis, and had an acceptable safety profile in this study population. These results support the use of protein C concentrate in the clinical management of patients with SCPCD in Japan. TRIAL REGISTRATION: ClinicalTrials.gov registration number: NCT04984889.