667P Updated efficacy and safety of larotrectinib in patients with TRK fusion salivary gland tumours

Abstract

Neurotrophic tyrosine receptor kinase (NTRK) gene fusions are oncogenic drivers of various tumour types, including salivary gland tumours (SGTs). Secretory carcinoma of the salivary gland, a rare subset of SGTs, is characterised by an ETV6-NTRK3 gene fusion found in ≥80% of cases. Larotrectinib is a highly selective, central nervous system-active, tropomyosin receptor kinase (TRK) inhibitor with an objective response rate (ORR) of 92% across 24 evaluable patients (pts) with a variety of SGTs, as of July 2020 (Le et al. Oncologist 2022 [in press]). We report updated efficacy and safety of larotrectinib in pts with TRK fusion SGTs with longer follow-up. Pts with TRK fusion SGTs were identified from two larotrectinib clinical trials (NCT02122913, NCT02576431). Pts received larotrectinib 100 mg twice a day (BID) except for one pt who received 150 mg BID in the phase 1 trial (NCT02122913). Response was assessed by independent review committee (per Response Evaluation Criteria in Solid Tumours v1.1). As of July 2021, 25 pts with TRK fusion SGTs were identified, including 24 with an additional year of follow-up. Median age was 59.0 years (range 28–80). All pts had ETV6-NTRK3 gene fusions. ORR was 84% (95% CI 64–95%): 8 complete responses, 13 partial responses, 2 stable disease and 2 progressive disease. Median time to response was 1.8 months. Median duration of response (DoR) was not reached; median follow-up was 39.6 months. Median progression-free survival (PFS) was 56.0 months (95% CI 30.8–not estimable) at a median follow-up of 41.3 months. Median overall survival (OS) was not reached at a median follow-up of 43.7 months. The 36-month DoR, PFS, and OS rates were 71%, 64%, and 82%. Duration of treatment ranged from 1.0 to 68.0 months. At data cut-off, 8 pts had progressed, with 5 pts continuing treatment post-progression for ≥4 weeks. Treatment-related adverse events (TRAEs) were mostly Grade 1–2. Grade 3–4 TRAEs were reported in 6 pts (24%). There were no treatment discontinuations due to TRAEs. Larotrectinib demonstrated rapid and durable efficacy with a favourable safety profile in pts with TRK fusion SGTs. These data highlight the importance of identifying NTRK gene fusions in pts with SGTs.