Preliminary results of the European multicentric phase III trial regarding sirolimus in slow-flow vascular malformations

Abstract

BACKGROUND. Slow-flow vascular malformations frequently harbor activating mutations in the PI3K/AKT/mTOR cascade. Phase II trials pinpointed sirolimus effectiveness as a drug therapy. Efficacy and safety of sirolimus thus need to be evaluated in large prospective phase III trials. METHODS. The Vascular Anomaly-Sirolimus-Europe (VASE) trial, initiated in 2016, is a large multicentric prospective phase III trial (EudraCT 2015-001703-32), which evaluates efficacy and safety of sirolimus for 2 years in pediatric and adult patients with symptomatic slow-flow vascular malformations. In this interim analysis, we studied all patients enrolled up to October 2021 who received sirolimus for 12 or more months or who prematurely stopped the treatment. RESULTS. Thirty-one pediatric and 101 adult patients were included in this analysis; 107 completed 12 or more months of sirolimus, including 61 who were treated for the whole 2-year period. Sirolimus resulted in a clinical improvement in 85% of patients. The efficacy appeared within the first month for the majority of them. Grade 3–4 adverse events were observed in 24 (18%) patients; all resolved after treatment interruption/arrest. Sirolimus increased feasibility of surgery or sclerotherapy in 20 (15%) patients initially deemed unsuitable for intervention. Among the 61 patients who completed the 2-year treatment, 33 (54%) reported a recurrence of symptoms after a median follow-up of 13 months after sirolimus arrest. While there was no difference in efficacy, clinical improvement was faster but subsided more rapidly in PIK3CA-mutated (n = 24) compared with TIE2-mutated (n = 19) patients. CONCLUSION. Sirolimus has a high efficacy and good tolerance in treatment of slow-flow vascular malformations in children and adults.