Efficacy and safety of erdafitinib in adults with breast cancer and prespecified fibroblast growth factor receptor alterations in the phase 2 open-label, single-arm RAGNAR trial.
Authors: Carranza Omar , Schuler Martin H. , Tabernero Josep , Loriot Yohann , Arnold Dirk , Folprecht Gunnar , Palmer Daniel , Zibetti Dal Molin Graziela , Gutierrez Martin , Prenen Hans , Lugowska Iwona A. , Cervantes Andres , Sweiti Hussein , Hammond Constance , Najmi Saltanat , Thomas Shibu , Triantos Spyros , Crow Lauren , Pant Shubham 
Published: June 2024

1088 Background: Erdafitinib is an oral selective pan-fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitor approved in the US for adult patients (pts) with locally advanced or metastatic urothelial carcinoma with susceptible FGFR3 genetic alterations, as determined by an FDA-approved companion diagnostic test, whose disease has progressed on or after ≥1 line of prior systemic therapy. The primary analysis results from the RAGNAR study demonstrated tumor agnostic efficacy in patients with advanced solid tumors with predefined FGFR alterations after failure of standard therapies (Pant 2023). Here, we report results on patients with breast cancer in the RAGNAR study. Methods: Patients with breast cancer and prespecified FGFR1-4 alterations (mutations or fusions) who had documented disease progression after exhausting standard therapies received oral erdafitinib 8 mg daily with optional up-titration until disease progression or intolerable toxicity. The primary end point was objective response rate by Independent Review Committee (IRC). Secondary endpoints include duration of response, disease control rate, progression-free survival, overall survival, and safety. Results: At data cutoff (median follow up, 30.3 months), 16 patients with breast cancer received erdafitinib. Median age was 54 y (range 37-74); all (100%) patients were female and had visceral metastases. Patients had a median of 5 prior lines of systemic therapies (range 2-12); one (6%) patient had responded to the last line of therapy. Ten (63%) patients had FGFR fusions, and 6 (38%) had FGFR mutations. Mutations of TP53 and PIK3CA were found in 6/16 patients. Objective response rate and disease control rate by IRC were 31% (95% CI 11-59) and 69% (95% CI 41-89); objective response rate and disease control rate by investigator were 38% (95% CI 15-65) and 69% (95% CI 41-89), respectively. Median time to onset of response was 1.4 months. Responses were observed in patients with both FGFR2 fusions and with FGFR2/3 mutations. Median duration of response, progression free survival, and overall survival were 6.9 months, 5.7 months, and 8.9 months, respectively. Common adverse events (AEs) included stomatitis (81%), diarrhea (69%), and hyperphosphatemia (69%), dry mouth (63%), and palmar-plantar erythrodysesthesia (44%). Six (38%) patients had serious AEs. No patients discontinued erdafitinib due to AEs. No treatment-related deaths were observed. Conclusions: Erdafitinib demonstrated clinically meaningful activity in heavily pretreated patients with breast cancer and prespecified FGFR alterations. Safety data were consistent with the erdafitinib safety profile. Clinical trial information: NCT04083976 .