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Avapritinib

Selective tyrosine kinase inhibitor (KIT D816V) · also known as Ayvakit, BLU-285

Selective KIT D816V inhibitor; the first agent in mast cell disease supported by a placebo-controlled randomised trial.

How it relates to mast cells
Mast cell disease
Types of studies cited
Randomised controlled trial
Approved in the US for
indolent systemic mastocytosis, advanced systemic mastocytosis, PDGFRA exon 18 gastrointestinal stromal tumour
Randomised trials in
indolent systemic mastocytosis

What this relationship means: Studied in patients with a different mast cell disease, usually systemic mastocytosis. Those disorders have diagnostic criteria and disease biology that differ from MCAS, so a result there does not establish an MCAS outcome.

Mechanism of action

Avapritinib is a tyrosine kinase inhibitor designed to bind the active conformation of KIT, and it retains potency against the D816V mutation that drives clonal mast cell proliferation in most systemic mastocytosis. That mutation renders earlier KIT inhibitors such as imatinib ineffective, which is the specific gap avapritinib was built to close.

The distinction that matters for this site: the randomised evidence is in indolent systemic mastocytosis — a clonal proliferative disease commonly defined by that mutation — not in mast cell activation syndrome. Clonal forms of mast-cell activation can exist without making an indolent-systemic-mastocytosis trial an MCAS trial; the diagnostic population and mutation-selected target still differ. The strength of the adjacent trial should not be read across to MCAS.

Sources

  1. AYVAKIT (avapritinib) US prescribing information Drug label · link checked 21 Aug 2026
  2. Avapritinib versus Placebo in Indolent Systemic Mastocytosis Peer-reviewed study 2023 PMID 38320129 NCT03731260 · link checked 20 Aug 2026
  3. New treatments for systemic mastocytosis in 2025 Review article 2025 PMID 40471046 · link checked 20 Aug 2026