Final Efficacy and Safety Data From the Phase I/II ARROW Study of Pralsetinib in Patients With Advanced RET Fusion-Positive Non-Small Cell Lung Cancer.

RET fusions appear in 1%-2% of non-small cell lung cancers (NSCLCs). The results from the ARROW study (ClinicalTrials.gov identifier: NCT03037385) supported US Food and Drug Administration approval of pralsetinib, an oral selective RET inhibitor, for metastatic RET-altered NSCLC and RET fusion-positive thyroid cancers. ARROW was a phase I/II open-label study of pralsetinib 400 mg once daily in RET fusion-positive NSCLCs. Coprimary end points were overall response rate (ORR) and safety. Key secondary end points included duration of response, progression-free survival, and overall survival (OS). At data lock (May 20, 2024), 281 patients initiated pralsetinib (median treatment duration, 15.0 months). ORR (measurable disease patients; n = 259) was 78% (95% CI, 69 to 86) for treatment-naïve patients and 63% (95% CI, 54 to 71) for prior platinum-based chemotherapy patients. Median OS was 44.3 months (95% CI, 30.9 to 53.1), 50.1 months (95% CI, 28.3 to not reached) in treatment-naïve patients, and 39.7 months (95% CI, 27.8 to 53.2) in prior platinum patients. Common grade ≥3 treatment-related adverse events were anemia (21%), hypertension (15%), and decreased neutrophils (13%). Three treatment-related deaths occurred (pneumonia, n = 2; interstitial lung disease and rhabdomyolysis, n = 1 each). Safety was consistent with previous ARROW reports; no hypersensitivity was reported in patients receiving prior immunotherapies. Pralsetinib produced robust, durable responses with manageable safety in treatment-naïve and previously treated patients with RET fusion-positive NSCLCs, confirming previous findings with longer follow-up.