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Evaluating BLU-263 for Indolent Systemic Mastocytosis

A Randomized, Double-Blind, Placebo-Controlled Phase 2/3 Study of BLU-263 in Indolent Systemic Mastocytosis

Phase2; Phase3 Interventional Blueprint Medicines Corporation · NCT04910685

This study is testing if a new medication called elenestinib can help people with indolent systemic mastocytosis who aren't getting enough relief from their current treatments.

Quick facts

PhasePhase2; Phase3
Study typeInterventional
Enrollment534 (estimated)
Ages18 Years and up
SexAll
SponsorBlueprint Medicines Corporation Industry-sponsored
Drugs / interventionsomalizumab, masitinib, prednisone, elenestinib
Locations64 sites (Birmingham, Alabama and 63 other locations)
Trial IDNCT04910685 on ClinicalTrials.gov

What this trial studies

This study is a randomized, double-blind, placebo-controlled trial assessing the efficacy and safety of elenestinib (BLU-263) in patients with indolent systemic mastocytosis (ISM) who have not achieved adequate symptom control with standard therapies. Participants will be enrolled in multiple parts, with those in Part 2 rolling over to receive open-label treatment in Part 3. The study also includes pharmacokinetic groups for further analysis of the drug's effects. The goal is to determine if elenestinib can provide better symptom management compared to placebo.

Who should consider this trial

Good fit: Ideal candidates are adults with a confirmed diagnosis of indolent systemic mastocytosis who have not adequately controlled their symptoms with existing therapies.

Not a fit: Patients who have not been diagnosed with indolent systemic mastocytosis or those whose symptoms are well-managed with current therapies may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could significantly improve symptom control for patients suffering from indolent systemic mastocytosis.

How similar studies have performed: Other studies have shown promise with similar approaches in treating systemic mastocytosis, but this specific treatment is being evaluated for the first time in this context.

Eligibility criteria

Show full inclusion / exclusion criteria 
Key Inclusion Criteria:

All Participants:

-Participant must have an Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0 to 2.

Part 1 and PK groups:

* Participant has confirmed diagnosis of ISM, confirmed by Central Pathology Review
* Participant must have failed to achieve adequate symptom control for 1 or more Baseline symptoms, as determined by the Investigator, with at least 2 of the following symptom-directed therapies administered: H1 blockers, H2 blockers, proton-pump inhibitors, leukotriene inhibitors, cromolyn sodium, corticosteroids, or omalizumab.
* Participants must have SDT for ISM symptom management stabilized for at least 14 days prior to starting screening procedures.
* For participants receiving corticosteroids, the dose must be ≤ 20 mg/day prednisone or equivalent, and the dose must be stable for ≥ 14 days.

Part K:

-Participant has confirmed diagnosis of ISM, confirmed by Central Pathology Review

Part S:

-Participant has confirmed diagnosis of SSM, confirmed by Central Pathology Review of BM biopsy and central review of B- and C-findings by WHO diagnostic criteria.

Part 2:

-Participant has confirmed diagnosis of ISM, confirmed by Central Pathology Review

Key Exclusion Criteria:

* Participant has been diagnosed with any of the following WHO systemic mastocytosis (SM) sub-classifications: cutaneous mastocytosis only, SM with an associated hematologic neoplasm of non-MC lineage (SM-AHN), aggressive SM, mast cell leukemia, or mast cell sarcoma.
* Participant has been diagnosed with another myeloproliferative disorder.
* Participant has organ damage attributable to SM.
* Participant has clinically significant, uncontrolled, cardiovascular disease
* Participant has a QT interval corrected using Fridericia's formula (QTcF) \> \> 470 milliseconds (msec) (for females) or \> 450 msec (for males).
* Participant has a history of a primary malignancy that has been diagnosed or required therapy within 3 years. The following prior malignancies are not exclusionary: completely resected basal cell and squamous cell skin cancer, curatively treated localized prostate cancer, and completely resected carcinoma in situ of any site.
* Time since any cytoreductive therapy including masitinib and midostaurin should be at least 5 half-lives or 14 days (whichever is longer), and for cladribine, interferon alpha, pegylated interferon, or antibody therapy \< 28 days or 5 half-lives of the drug (whichever is longer), before beginning the screening period.
* Participant has received radiotherapy or psoralen and ultraviolet A (PUVA) therapy \< 14 days before beginning the screening period.

Other protocol-defined criteria apply.

Where this trial is running

Birmingham, Alabama and 63 other locations

+14 more sites — see ClinicalTrials.gov for the full list.

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Indolent Systemic MastocytosisSmoldering Systemic MastocytosisISMSSM
Last reviewed 2026-06-09 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.