Fierce-21: Phase II study of vofatmab (B-701), a selective inhibitor of FGFR3, as salvage therapy in metastatic urothelial carcinoma (mUC).

Abstract

409 Background: Patients (pts) with mUC who have failed platinum-based chemotherapy have a poor prognosis. About 20% of them usually respond to immune checkpoint inhibitors (ICI). Also, 20% of pts with mUC harbor FGFR3 mutations or fusions (M/F), and this feature may be associated with lower sensitivity to ICI. Vofatamab (B-701) is a fully human monoclonal antibody against FGFR3 that blocks activation of the wildtype and genetically activated receptor. FIERCE-21 is a Phase 1b/2 study designed to evaluate vofatamab monotherapy (VM) or in combination with docetaxel (VD). Methods: The study consists of a P 1b lead-in (P1b with VD), previously reported followed by P2 expansion cohort in FGFR3 M/F+ pts (identified with the FoundationONE CDx™ assay on archival samples). The study enrolled mUC pts with failure to ≥ 1 line prior chemotherapy (including prior taxane treatment) or ≤12 months of (neo)adjuvant chemotherapy, measurable disease and ECOG ≤ 1. Treatment consisted of vofatamab at 25 mg/kg alone (VM) and in combination with D (VD) at 75 mg/m 2 q3w. Efficacy was assessed by investigators (RECIST 1.1). Primary objectives were safety and activity (objective response-rate [ORR]). Results: 55 pts have received treatment. In the Ph 2 study, 21 pts received VM, 15 pts received VD. 35% of pts were included as 2 nd line therapy, 65% in 3 rd or later line of treatment. For pts receiving VD, safety was consistent with Ph 1B data. For pts receiving VM, median age was 67 yrs, ECOG 1 = 71.4%, Hgb < 10 gm/dL 13%, liver metastases 19%, ≥ 2 prior regimens 57%, (best response to prior therapy PD 31%). TEAEs occurring in ≥5% patients were asthenia (19%), diarrhea (9.5%), flushing 14%, chills (9.5%), hypotension (9.5%), decreased appetite (19%) and creatinine increased (9.5%). The majority of TEAS were grade 1 and 2. Only 1 patient on MF had a grade 3 TEAE and only 1 patient discontinued treatment due to an AE. The ORR have been seen in 7 pts to date including those receiving both VM and VD. Conclusions: Vofatamab both alone and combined with D in an every 3-week schedule are well tolerated with a low frequency of grade 3 TEAEs. Both VM and VD have demonstrated efficacy in terms of ORR, and mature results with PFS data will be presented. Clinical trial information: NCT02401542.