ASCO GU 2019: Fierce-21: Phase II Study of Vofatamab, a Selective Inhibitor of FGFR3, as Salvage Therapy in Metastatic Urothelial Carcinoma

San Francisco, CA ( Somatic activating mutations of FGFR3 were first described over a decade ago in patients with bladder and cervical cancer.1 According to 9 prior bladder cancer cohorts on CBIO portal, FGFR3 is altered anywhere from 7% to 20% of all cases (Figure 1). Gene fusions occur in up to 2% of patients and FGFR3 amplification occurs in up to 3% of cases. In non-muscle invasive bladder cancer, FGFR3 is thought to identify patients who have a lower risk of recurrence.2 In patients with Metastatic Urothelial Cancer (mUC), FGFR is a potential target of therapy and several FGFR inhibitors are now in early phase clinical trials.

At ASCO GU 2018, Dr. Loriot presented the results of erdafitinib, a pan-FGFR inhibitor for patients with mUC and found a confirmed objective response rate of 35% in those receiving erdafitinib continuously.3 Dr. Joerger also presented results of another oral pan-FGFR kinase inhibitor at ASCO GU 2018, rogaratinib. In his biomarker preselected cohort of patients with high FGFR1-3 mRNA expression, objective response rate was 30% (3/10). This abstract provides data on a selective FGFR3 inhibitor, Vofatamab (B-701), for patients with metastatic UC.
ASCO GU 2019 FGFR3 alterations

Figure 1: Incidence of FGFR3 alterations based on 9 urothelial carcinoma databases. 
ASCO GU 2019 FIERCE 21 Study Design
Generated by Jason Zhu from

This is a phase I/II clinical trial which treated patients with Vofatamab (V) or Vofatamab in combination with docetaxel (VD). Vofatamab is thought to prevent FGFR3 activation via prevention of ligand activation of the FGFR3 receptor as well as preventing mutant/fusion signaling. Patients were required to have a pathogenic FGFR3 mutation or fusion identified using the FoundationONE assay on archival samples. Patients must have had progressed on one or more prior lines of chemotherapy or had progression less than 12 months from neoadjuvant chemotherapy. Vofatamab was dosed at 25 mg/kg and docetaxel was given at 75 mg/m2.

ASCO GU 2019 FIERCE 21 Baseline Demographics and Treatment History of Patients

21 patients have received V and 21 patients have received VD. In terms of patient characteristics, the median age was 64 in the combination arm and 70 in the monotherapy arm. 52% of patients had visceral metastases in the VD arm and 43% in the D arm. These patients were heavily pre-treated, with most patients having had 2-3 prior lines of chemotherapy and about half of patients had prior immune checkpoint therapy.

In terms of efficacy, 5 out of 21 patients have had a partial response thus far in the VD arm compared with 1 out of 21 patients in the V arm. The median time to response was 3.5 months in VD and 4 months in V. In terms of safety, the most common treatment-emergent adverse events were decreased appetite, diarrhea, and pyrexia. The most common grade 3 or higher TRAEs was anemia, dyspnea, and fatigue.

ASCO GU 2019 FIERCE 21 Efficacy

In a heavily pre-treated population with metastatic UC, Vofatamab in combination with docetaxel is well tolerated and effective in a small population of patients. Combination therapy appears to have more objective responses than Vofatamab monotherapy. Follow up is immature at this time, but the results presented show that Vofatamab is an active therapy and additional combination are being explored.

Presented by: Andrea Necchi, MD, Medical Director, Istituto Nazionale dei Tumori, Milan, Italy

Written by: Jason Zhu, MD. Fellow, Division of Hematology and Oncology, Duke University, @TheRealJasonZhu at the 2019 American Society of Clinical Oncology Genitourinary Cancers Symposium, (ASCO GU) #GU19, February 14-16, 2019 - San Francisco, CA

  1. Cappellen D, De Oliveira C, Ricol D, et al. Frequent activating mutations of FGFR3 in human bladder and cervix carcinomas. Nature genetics 1999;23:18.
  2. van Rhijn BW, Lurkin I, Radvanyi F, Kirkels WJ, van der Kwast TH, Zwarthoff EC. The fibroblast growth factor receptor 3 (FGFR3) mutation is a strong indicator of superficial bladder cancer with low recurrence rate. Cancer research 2001;61:1265-8.
  3. Loriot Y, Necchi A, Park SH, et al. Erdafitinib (ERDA; JNJ-42756493), a pan-fibroblast growth factor receptor (FGFR) inhibitor, in patients (pts) with metastatic or unresectable urothelial carcinoma (mUC) and FGFR alterations (FGFRa): Phase 2 continuous versus intermittent dosing. American Society of Clinical Oncology; 2018.