Pan-cancer efficacy of pralsetinib in patients with RET fusion–positive solid tumors from the phase 1/2 ARROW trial

Oncogenic RET fusions occur in diverse cancers. Pralsetinib is a potent, selective inhibitor of RET receptor tyrosine kinase. ARROW ( NCT03037385 , ongoing) was designed to evaluate pralsetinib efficacy and safety in patients with advanced RET-altered solid tumors. Twenty-nine patients with 12 different RET fusion-positive solid tumor types, excluding non-small-cell lung cancer and thyroid cancer, who had previously received or were not candidates for standard therapies, were enrolled. The most common RET fusion partners in 23 efficacy-evaluable patients were CCDC6 (26%), KIF5B (26%) and NCOA4 (13%). Overall response rate, the primary endpoint, was 57% (95% confidence interval, 35-77) among these patients. Responses were observed regardless of tumor type or RET fusion partner. Median duration of response, progression-free survival and overall survival were 12 months, 7 months and 14 months, respectively. The most common grade ≥3 treatment-related adverse events were neutropenia (31%) and anemia (14%). These data validate RET as a tissue-agnostic target with sensitivity to RET inhibition, indicating pralsetinib's potential as a well-tolerated treatment option with rapid, robust and durable anti-tumor activity in patients with diverse RET fusion-positive solid tumors.