Early clinical experience with the pan-FGFR inhibitor rogaratinib in patients with non-small cell lung cancer selected based on FGFR mRNA expression levels.

e20661 Background: FGFR1 gene amplifications are observed in squamous (sq) non-small cell lung cancer (NSCLC) and may suggest tractable oncogenic dependency. However, their value in predicting clinical activity of FGFR inhibitors is unclear. We explored tumor FGFR1-3 mRNA expression levels to select patients (pts) for treatment with rogaratinib, an oral, potent, small-molecule inhibitor of FGFR1-4. The first-in-human study of rogaratinib included pts with all NSCLC histologies. Methods: Pts with refractory advanced NSCLC were screened for elevated FGFR1-3 mRNA levels by RNA in situ hybridization (RNAscope) and NanoString assay in fresh or archival tumor samples, and FGFR1-3 overexpression was defined by pre-specified cut-offs. Pts received rogaratinib 800 mg BID on a continuous 21-day cycle. Tumor response was assessed by Response Evaluation Criteria in Solid Tumors v1.1 after cycles 2, 5, and 8. Results: 260 NSCLC biopsies were screened for FGFR1-3 tumor mRNA expression; 244 (93.8%) were evaluable. FGFR1-3 mRNA overexpression was found in 47% of sq NSCLC, and only 14% of non-sq NSCLC, with FGFR3 being the most commonly overexpressed subtype. 40 FGFR mRNA-positive pts were enrolled and treated. Rogaratinib was well tolerated; hyperphosphatemia (75%), diarrhea (53%), and decreased appetite (35%) were the most frequent treatment-emergent adverse events. Events were mostly mild or moderate. 36 treated pts were evaluable for response. The overall response rate was 5.6% (2 partial responses, 1 lasting for > 16 months). Disease control rate was 64%. Disease stabilization was seen in pts with mRNA overexpression across all FGFR subtypes and also in pts who failed prior lines of therapy, including anti-PD-L1. Molecular studies are ongoing to identify additional predictors of response to improve pt selection. Conclusions: Rogaratinib has a favorable safety and tolerability profile and clinical activity in pts with refractory FGFR1-3 tumor mRNA-positive NSCLC. It has potential for further exploration in combination with other agents. A clinical trial is currently enrolling FGFR mRNA-overexpressing pts with advanced and pre-treated sq NSCLC. Clinical trial information: NCT03762122.