Rainier Therapeutics, Inc. is developing vofatamab, or B-701, a highly specific human anti-FGFR3 antibody, for metastatic bladder cancer (urothelial cell carcinoma).


Vofatamab, or B-701, is a human IgG1 monoclonal antibody that is highly specific for the FGFR3 receptor and does not cross-react with the other fibroblast growth factor receptors (FGFRs). It is being used to inhibit signaling through this pathway in bladder cancers that express wild-type or mutated FGFR3 and has potential for application in other FGFR3 expressing cancers.

Two Phase 1 clinical, open-label, dose-escalating studies have been conducted with patients receiving repeat intravenous injections of vofatamab. These include a Phase 1 study in patients with relapsed/refractory t(4;14)-positive multiple myeloma and a Phase 1 study in patients with advanced solid tumors, including relapsed/refractory metastatic bladder cancer. In these studies, vofatamab was shown to be safe and generally well tolerated.

Rainier has initiated a Phase 2 clinical study investigating vofatamab for the treatment of locally advanced or metastatic bladder cancer also known as urothelial cell carcinoma (UCC). The study will assess efficacy and safety study of vofatamab in combination with docetaxel versus docetaxel alone in patients with Stage IV, locally advanced or metastatic UCC who have relapsed after, or are refractory to one or two prior lines of chemotherapy which have not included a taxane.

This study is divided into two phases: an open label lead-in phase, which will assess the safety and early signal of efficacy of vofatamab plus docetaxel, a monotherapy extension phase and a combination with docetaxel vs. docetaxel. Details of this study can be found on www.clinicaltrials.gov.

Separately, we are testing vofatamab in combination with an immune checkpoint inhibitor, pembrolizumab in patients with advanced/metastatic urothelial cell carcinoma. Planning is underway to study vofatamab in non-muscle invasive bladder cancer.