Mazières, Julien

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.

9089 Background: RET fusions are targetable oncogenic drivers in 1–2% of non-small cell lung cancer (NSCLC). ARROW (NCT03037385) supported the US FDA approval of pralsetinib, a highly potent oral selective RET inhibitor for RET-altered NSCLC and thyroid cancer. Here, we present updated results for a larger population of patients with RET fusion–positive NSCLC enrolled in ARROW. Methods: ARROW is a phase 1/2 open-label study conducted at 84 sites in 13 countries. Phase 2 expansion cohorts included patients with RET fusion–positive NSCLC. Initially, all treatment-naïve patients were not candidates for platinum-based therapy, a requirement removed by protocol amendment in July 2019. Primary objectives are overall response rate (ORR; blinded independent central review [BICR] per RECIST v1.1), assessed for patients with baseline measurable disease, and safety. Results: Updated analyses were completed as of Nov 6, 2020 (data cut-off), for patients who initiated pralsetinib 400 mg QD by May 22, 2020 (enrollment cut-off). Efficacy results, including analyses for treatment-naïve patients enrolled after eligibility criteria were revised to allow candidates for platinum-based therapy, are shown in the Table. Conclusions: Pralsetinib showed rapid, potent, and durable clinical activity in patients with RET fusion-positive NSCLC (regardless of prior therapies), including poor prognosis patients not eligible for platinum-based therapy. Overall, pralsetinib was well-tolerated. These data highlight the need for RET testing early in the course of disease to identify candidates who may benefit from treatment with pralsetinib. Clinical trial information: NCT03037385. [Table: see text]