Larotrectinib long-term efficacy and safety in adult patients (pts) with tropomyosin receptor kinase (TRK) fusion Cancer

3141 Background: Neurotrophic tyrosine receptor kinase ( NTRK) gene fusions are oncogenic drivers in a broad array of tumor types. Larotrectinib is a first-in-class, highly selective, central nervous system (CNS)-active TRK inhibitor approved for tumor-agnostic use in pts with TRK fusion cancer based on a rapid, robust, and durable objective response rate (ORR) in both adult and pediatric pts with various non-primary CNS cancers. Here, we report data on an expanded cohort of adult pts with TRK fusion cancer treated with larotrectinib. Methods: Adults with non-primary CNS TRK fusion cancer treated in three larotrectinib clinical trials (NCT02576431, NCT02122913, and NCT02637687) were included. Larotrectinib was administered at 100 mg twice daily in most pts. Responses were assessed per Independent Review Committee (IRC) using RECIST v1.1. Data cut-off: July 2022. Results: As of July 2022, there were 194 adult pts enrolled, with 180 eligible for efficacy analyses by IRC; 22 pts had known brain metastases at baseline. There were 24 different tumor types; the most common were lung (n=30; 15%), soft tissue sarcoma (n=30; 15%), thyroid (n=28; 14%), salivary gland (n=25; 13%), and colon (n=23; 12%). Median age was 57 years (range 19–90). The gene fusions involved NTRK1 (n=90; 46%), NTRK2 (n=7; 4%), or NTRK3 (n=97; 50%). Pts had previously received a median of one systemic therapy (range 0–10). ORR was 57% (95% CI 50–65): 29 (16%) complete response (including one pathological complete response), 74 (41%) partial response, 39 (22%) stable disease, 23 (13%) progressive disease, and 15 (8%) not evaluable. ORR in 22 evaluable pts with baseline CNS metastases was 68% (95% CI 45–86). Median time to response was 1.8 months, and median duration of response was 43.3 months (95% CI 29.2–not estimable [NE]) at a median follow-up of 32.3 months. Median progression-free survival was 24.6 months (95% CI 11.3–34.5) at a median follow-up of 28.5 months. Median overall survival was 48.7 months (95% CI 38.5–NE) at a median follow-up of 33.8 months. At data cut-off, 39 of the 73 pts who had disease progression continued treatment post-progression for ≥4 weeks. Treatment-related adverse events (TRAEs) were predominantly Grade 1/2. Grade 3/4 TRAEs occurred in 27 (14%) pts. Treatment discontinuation due to TRAEs was reported in one pt (increased alanine aminotransferase and aspartate aminotransferase). Conclusions: In this expanded dataset with extended follow-up, larotrectinib continues to demonstrate rapid and durable responses, extended survival, and a favorable safety profile in adults with TRK fusion cancer, including those with CNS metastases. These results support the wider adoption of next-generation sequencing panels that include NTRK gene fusions when testing pts with solid tumors; this ensures that pts are offered the right medicine for their disease as soon as possible. Clinical trial information: NCT02576431 , NCT02122913 , NCT02637687 .