KIT (c-Kit), also PDGFR and Lyn/Fyn kinases

Class

oral multi-target tyrosine kinase inhibitor

Pathway

mast cell/FcεRI-driven inflammation

KIT is a receptor tyrosine kinase expressed on mast cells, among other cell types, that responds to stem cell factor to promote mast cell survival, proliferation, and maturation. Mast cells are central effector cells in allergic and inflammatory disease: when their surface IgE receptor (FcεRI) is cross-linked by allergen, intracellular kinases including Lyn and Fyn (members of the Src family) initiate a signaling cascade that triggers degranulation, releasing histamine and other inflammatory mediators. A multi-target tyrosine kinase inhibitor that acts on KIT, PDGFR (a related receptor kinase involved in stromal and vascular signaling), and Lyn/Fyn addresses mast cell biology from two angles: reducing the population of mast cells available to react, and dampening the intracellular signal that drives degranulation once triggered. This combined action is relevant to diseases where mast cells are pathologically increased in number, abnormally activated, or both, including mastocytosis and various chronic allergic and inflammatory conditions. Modulating KIT and its related kinases offers a mechanistic route to controlling mast cell-driven disease that is distinct from simply blocking a single mediator such as histamine, because it addresses the upstream drivers of mast cell persistence and reactivity rather than one downstream product of their activation.