ATLANTA, GA—A post-hoc subgroup analysis of data from the COMPACT trial found that patients previously using intravenous (IV) C1 Inhibitor (INH) prophylaxis for hereditary angioedema (HAE) who switched to subcutaneous (SC) C1INH (40 or 60 IU/kg) for routine prevention experienced “an approximate 50% further reduction in HAE attack rate with use of C1-INH(SC), reported Timothy J. Craig, DO, FAAAAI, of Penn State University, in Hershey, PA, at the 2017 AAAAI Annual Meeting.

“These subgroup findings suggest that switching from C1INH(IV) routine prophylaxis to C1INH(SC) for routine prevention of HAE attacks can help patients achieve better control of HAE,” Dr. Craig and coauthors reported.

Additional study with more patients are needed to corroborate the findings, they noted.

The authors analyzed data for 21 patients who had switched from C1INH(IV) for routine HAE prophylaxis to C1INH(SC) for routine prevention as part of the COMPACT trial. The rate of HAE attacks for patients on C1INH(IV) was analyzed for 3 months prior to initiation of the trial and rate analysis for C1INH(SC) continued throughout the study.

HAE attack rate decreased after switching from C1INH(IV) prophylaxis to C1-INH(SC), from a median of 2.7 to 1.2 while using C1INH(SC) for routine prevention. Additionally, a 52.1% reduction in the rate of HAE attacks occurred when patients switched from using C1INH(IV) to C1INH(SC).

The study authors also reported that a larger reduction in HAE attack rates was seen in patients receiving 60 IU/kg of C1INH(SC) compared to those receiving the 40 IU/kg dose. 

The study involved a small number of patients and HAE attacks during the pre-study period were assessed unsystematically using patients’ medical records, the authors cautioned. Assessments of HAE attacks during the study period were systematic, investigator-reported evaluations based on patients’ daily electronic diary entries.