Long-Term Prophylaxis with Recombinant Human C1 Inhibitor in Patients with Hereditary Angioedema: Is Intramuscular Administration an Option?
Saturday, March 3, 2018
South Hall A2 (Convention Center)
Anna Valerieva, Borislava Krusheva, MD, Maria Staevska
RATIONALE: Recombinant C1-inhibitor (rhC1-INH) is registered for intravenous treatment (IV) of hereditary angioedema (HAE) attacks. Intravenous prophylactic treatment (PT) with C1-INH is an opportunity in patients with frequent and/or severe episodes. As off today intramuscular (IM) administration is not investigated in clinical trials, but is known for its ease of self-administration.

METHODS: Off-label IM PT with rhC1-INH in 2 HAE Type 1 patients (S1: 58-y-female, 85 kg; S2: 72-y-male, 90 kg) suffering 6-12 HAE attacks/month with difficult IV access, causing unnecessary treatment delays up to 3 hours. After all ethical implications were discussed, a regular IM PT with 4200 U (2 vials, each reconstituted in 10 mL WFI) twice/weekly was initiated. Patient diaries were analyzed, which included documentation for pain by the visual analogue scale (VAS).

RESULTS: Both patients showed good efficacy of the 232 IM PT administrations (Treatment period: S1: 22 weeks, S2: 36 weeks). One breakthrough attack occurred. Five prodromal symptoms were registered and rhC1-INH was administered IM, coping an attack onset. VAS (pain) for IM rhC1-INH (1.54, 0.58, respectively) was comparable to a comparable IM (1.3, 0.5), and less than IV (2.5, 2.0) injections. Mild bruises and transitory edema at the injection sites were observed (S1: 7/88; S2: 0/144 administrations). No serious adverse events were registered.

CONCLUSIONS: Prophylactic intramuscular administration of rhC1-INH could be an alternative to the intravenous administration. Intramuscular application of 10 mL solution of 2100 U of the drug seems to be safe and well tolerated. VAS (pain) for IM rhC1-INH is comparable to a comparable IM injection.