On 16 November 2017, the US Food and Drug Administration (FDA) approved emicizumab-kxwh (HEMLIBRA, Genentech, Inc.) for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adult and paediatric patients with haemophilia A (congenital factor VIII deficiency) with factor VIII inhibitors.
Approval was based on data from two clinical trials—an adult and adolescent trial (HAVEN 1) and a paediatric trial (HAVEN 2). HAVEN 1 (NCT02622321) was a randomised, multicentre, open-label, phase III trial in 109 adult and adolescent males (aged 12 to 75 years and >40 kg) with haemophilia A with FVIII inhibitors who previously received either episodic (on-demand) or prophylactic treatment with bypassing agents. Patients on prior episodic treatment were randomised 2:1 to weekly emicizumab-kxwh prophylaxis (3 mg/kg once weekly for the first 4 weeks followed by 1.5 mg/kg once weekly, thereafter) or no prophylaxis. Patients randomised to no prophylaxis could switch to emicizumab-kxwh prophylaxis after 24 weeks. For patients receiving emicizumab-kxwh prophylaxis, the annualized bleeding rate (ABR) requiring treatment with coagulation factors was 2.9 (95% CI; 1.7, 5.0) compared with 23.3 (95% CI: 12.3, 43.9) for patients not receiving prophylaxis corresponding to an 87% ABR reduction (95% CI: 72.3%, 94.3%), p < 0.0001. In addition, improvements in patient-reported haemophilia-related symptoms and physical functioning in patients receiving emicizumab-kxwh prophylaxis were observed.
HAVEN 2 (NCT02795767) was a single-arm, multicentre, open-label, clinical trial in paediatric males (age < 12 years, or 12-17 years who weigh <40 kg) with haemophilia A with FVIII inhibitors. Patients received emicizumab-kxwh prophylaxis at the dose and schedule described above. In 23 patients evaluated at the interim analysis, ABR for treated bleeds was 0.2 (95% CI: 0.1, 0.6). ABR for all bleeds was 2.9 (95% CI: 1.8, 4.9).
The most common adverse reactions (occurring in ≥ 10% of patients taking emicizumab-kxwh) are injection site reactions, headache, and arthralgia. Cases of thrombotic microangiopathy and thrombotic events were reported when on average a cumulative amount of >100 U/kg/24 hours of activated prothrombin complex concentrate (aPCC) was administered for 24 hours or more to patients receiving emicizumab-kxwh prophylaxis. The prescribing information contains a boxed warning to monitor for thrombotic microangiopathy and thrombotic events when aPCC is administered. If symptoms occur, aPCC should be discontinued and emicizumab-kxwh should be suspended.
The recommended dose of emicizumab-kxwh is 3 mg/kg by subcutaneous injection once weekly for the first 4 weeks, followed by 1.5 mg/kg once weekly.
Full prescribing information is available here.
Emicizumab-kxwh was approved 3.3 months prior to the assigned regulatory action date. FDA granted Priority Review, Breakthrough Therapy designation, and Orphan Drug designation for this indication.
Healthcare professionals should report all serious adverse events suspected to be associated with the use of any medicine and device to FDA’s MedWatch Reporting System.