Subcutaneous plasma-derived C1-inhibitor (pdC1-INH) represents a therapeutic alternative for patients with hereditary angioedema (HAE) who require long-term prophylaxis and have difficult venous access, according to a recently published study in Frontiers in Allergy.

Intravenous pdC1-INH has been proven to reduce the frequency of acute HAE attacks by 50% and has been used as long-term prophylaxis for more than a decade. However, many patients still experience frequent attacks while receiving the treatment. Additionally, continuous intravenous treatment can represent a challenge for patients with difficult venous access.

“For patients experiencing frequent breakthrough attacks despite [long-term prophylaxis] or having poor venous access, an unmet need for prophylaxis is present,” the authors wrote. 

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Recently, a phase 3 clinical trial has shown that subcutaneous pdC1-INH administration could maintain C1-inhibitor activity above 40% of baseline, the level required to prevent acute HAE attacks. Furthermore, the same trial found that subcutaneous pdC1-INH decreased the attack frequency compared to placebo.

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The authors of the present study aimed to assess the efficacy of subcutaneous pdC1-INH using clinical records from 5 patients with HAE who either had poor venous access or did not experience a reduction in attacks with intravenous long-term prophylaxis. Of the 5 patients, 3 experienced a significant decrease in attack frequency with 2 doses per week. 

The dose weight ratio of the infusions ranged from 42.86 to 65.22 IU/kg, which is lower than the recommended dose of intravenous pdC1-INH. One patient did not show any significant difference in comparison with intravenous treatment, and another patient showed improvement only after increasing the administration to 3 times a week. No patient included in the study remained completely attack-free.

No severe adverse effects were reported during the study. However, 2 patients experienced mild adverse effects including erythema and pruritis at the injection site; the adverse effects resolved spontaneously in both cases.

“These results may be useful for physicians facing patients with difficult venous access in countries where pdC1-INH is not registered for subcutaneous administration or in the absence of availability of other new drugs for long-term prophylaxis such as lanadelumab and berotralstat,” the authors concluded.


Zanichelli A, Suffritti C, Popescu Janu V, Merlo A, Cogliati C. Real-life experience with subcutaneous plasma-derived C1-inhibitor for long-term prophylaxis in patients with hereditary angioedema: a case series. Front Allergy. 2022;3:818741. doi:10.3389/falgy.2022.818741