Treatment of Systemic Mastocytosis with KIT D816V Mutation in Aggressive Systemic Mastocytosis
Aggressive systemic mastocytosis (ASM) with a KIT D816V mutation is an advanced form of systemic mastocytosis defined by mast cell–driven organ dysfunction. The KIT D816V mutation acts as the primary oncogenic driver and is central to treatment selection in this population.
Clinical Scenario
ASM is characterised by one or more C-findings reflecting progressive organ damage. Patients in this setting frequently require cytoreductive therapy directed at mast cell proliferation to reverse organ dysfunction. The presence of the KIT D816V mutation identifies a molecularly targetable disease mechanism.
Treatment Approach
This scenario has a dedicated first-line regimen centred on an FDA-approved selective kinase inhibitor that directly targets the mutant KIT protein — the structured protocol specifies the complete approach, sequencing, and decision criteria.
Clinical Goals
The primary therapeutic targets are reversion of disease-related organ damage and a marked decrease in bone marrow mast cell burden, with the potential for molecular remission in the mutant KIT clone.
References
DOI: 10.1002/ajh.26962
- Patients with advanced SM frequently need MC cytoreductive therapy to reverse disease-related organ dysfunction.
- ASM is characterized by one or more C-findings (Table 5); of note, the definition of C-findings has undergone revision in the 2022 WHO classification.
- Avapritinib (BLU-285): received FDA approval for first-line treatment for adult patients with advanced SM, including those with ASM, SM-AMN and MCL in June 2021, based on data from EXPLORER (NCT02561988) and PATHFINDER (NCT03580655), two multicenter, single-arm, open-label clinical trials.
- Interim results from the PATHFINDER study, an ongoing registrational Phase 2 trial of avapritinib 200 mg daily in adult patients with advanced SM, were recently published.
- Recent data with potent tyrosine kinase inhibitors (TKI) that selectively target mutant-KIT have shown reversion of organ damage with marked decrease in BM MC burden, as well as the potential for KITD816V molecular remissions, suggesting the possibility of disease modifying therapeutic effect in patients with advanced SM.
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