High affinity nerve growth factor receptor fusion protein (TRKA fusion)

TRKA fusion kinases are chimeric proteins resulting from chromosomal rearrangements where the 3' region of the NTRK1 gene, encoding the tyrosine kinase domain, is fused to the 5' sequence of a partner gene [UniProt P04629; PubMed 25711232]. This fusion leads to the constitutive, ligand-independent activation of the TRKA kinase, which drives aberrant oncogenic signaling through pathways such as MAPK, PI3K, and PLC-gamma [StatPearls, 2023]. These fusions are rare across the general cancer population but act as potent, defining oncogenic drivers in specific rare tumors like infantile fibrosarcoma and secretory breast carcinoma, as well as a small subset of common adult solid tumors [PubMed 30445318]. Because the kinase activity of the fusion protein is the primary driver of malignancy, TRKA fusions are highly actionable therapeutic targets. Selective TRK inhibitors, such as larotrectinib and entrectinib, have demonstrated high response rates and durable efficacy in patients harboring these fusions, regardless of the tumor's tissue of origin [FDA Label, 2019]. However, clinical management is often complicated by the eventual emergence of acquired resistance mutations in the kinase domain, such as solvent front or gatekeeper mutations, which necessitate the use of next-generation TRK inhibitors [PubMed 31125954]. Additionally, because physiological TRK signaling is vital for nervous system function, these drugs are associated with specific neurological side effects like dizziness and paresthesia.

Other names

NTRK1 fusionTropomyosin receptor kinase A fusionTRKA-rearranged proteinTRKA fusion kinaseMASC fusion

Small molecule inhibition of the tropomyosin receptor kinase (TRK) catalytic activity by competitively binding to the ATP-binding site of the kinase domain, thereby preventing autophosphorylation and downstream activation of oncogenic signaling pathways such as MAPK, PI3K, and PLC-gamma [StatPearls, 2023; FDA Label, 2018].