(HARBOR) Study to Evaluate Efficacy and Safety of BLU-263 Versus Placebo in Patients With Indolent Systemic Mastocytosis

This is a randomized, double-blind, placebo-controlled, Phase 2/3 study comparing the efficacy and safety of elenestinib (BLU-263) + symptom directed therapy (SDT) with placebo + SDT in participants with indolent systemic mastocytosis (ISM) whose symptoms are not adequately controlled by SDT. Parts 1 and 2 will enroll participants with ISM. Participants enrolled in Part 2 will roll over onto Part 3 to receive treatment with elenestinib in an open-label fashion following completion of the earlier Part. Part K will enroll participants with ISM who have previously received an approved selective KIT inhibitor. The study also includes pharmacokinetic (PK) groups that will enroll participants with ISM.

NCT Number	NCT04910685
Lead Sponsor	Blueprint Medicines Corporation
Conditions	Indolent Systemic Mastocytosis, Smoldering Systemic Mastocytosis
Enrollment	534 participants
Start Date	2021-11-30
Primary Completion	2032-09-30 (estimated)
Study Completion	2032-09-30 (estimated)
Updated on ClinicalTrials.gov	2026-08-04