Rainier Therapeutics Announces Presentation of Patient Biopsy Data Demonstrating Vofatamab’s Ability to Increase Immune Cell Activation

– Vofatamab activates immune changes in immunologically cold tumors
and in combination increases patient response rates –

– Data from FIERCE-22 Trial in Patients with Metastatic Bladder
Cancer Presented at AACR Bladder Cancer Conference –

SAN LEANDRO, Calif.–(BUSINESS WIRE)–Rainier Therapeutics, Inc., a privately-held clinical stage drug
development company, today announced the presentation of data from its
FIERCE-22 trial where vofatamab, the company’s lead therapeutic
stimulates an increase in immune cell activation in patients with
metastatic bladder cancer. The data is being presented in an oral and
poster presentation at the 2019 American Association for Cancer Research
(AACR) Bladder Cancer: Transforming the Field Special Conference.

Researchers at John Hopkins School of Medicine and MD Anderson analyzed
RNA from 22 paired biopsy samples from metastatic bladder cancer
patients enrolled in Rainier’s Phase 1b / 2 FIERCE-22 trial. Patients
who had progressed following platinum-based chemotherapy but had not
received prior immune checkpoint inhibitor therapy were eligible to
enroll. Tumor biopsies were taken pre- and post-treatment with
vofatamab, and prior to the start of combination treatment with
pembrolizumab. Patient biopsies were taken to understand changes to gene
signatures induced with vofatamab and to correlate this with clinical
outcomes.

“The unique design of the trial allowed us to evaluate the effect of
FGFR3 inhibition on gene signatures,” said David McConkey, Ph.D., John
Hopkins School of Medicine. “Vofatamab, an FGFR3 specific antibody,
significantly upregulated genes associated with inflammation in both
wild-type and FGFR3 mutant tumors. This was associated with an
increased response rate to the combination with pembrolizumab in these
patients and was particularly marked in patients with luminal biology.”

“Tumors that are immunologically ‘cold’ tend to exist in luminal bladder
cancer and these patients have historically responded poorly to
checkpoint inhibitors. The enhanced response rate seen suggests this
combination may provide a valuable new treatment option,” said Graeme
Currie, Ph.D., Chief Operating Officer, Rainier Therapeutics. “We look
forward to presenting interim clinical data from FIERCE-22 at the
upcoming 2019 ASCO annual meeting.”

Key Findings:

• Compared to historical data with pembrolizumab, response rates with
  vofatamab treatment appear higher.
• Vofatamab responders had upregulation of genes associated with an
  inflammatory response in the tumor.
• Responses were enriched in the cohort with a luminal gene expression
  profile (also referred to as “immunologically cold”).

About Vofatamab

Vofatamab (formerly B-701) is an antibody specifically targeted against
the fibroblast growth factor receptor 3 (FGFR3), a known driver of
bladder and potentially other FGFR-driven cancers. Vofatamab is the most
advanced targeted antibody specific for FGFR3 known by Rainier
Therapeutics to be in clinical development. Vofatamab is currently being
evaluated in two clinical trials: FIERCE-22 and FIERCE-21.

FIERCE-22 is a Phase 2 trial evaluating vofatamab in combination with
pembrolizumab, an immune checkpoint inhibitor, to determine safety,
tolerability and efficacy in the treatment of patients with locally
advanced or metastatic bladder cancer, who have progressed following
platinum-based chemotherapy and who have not received prior immune
checkpoint inhibitor therapy. For additional information on FIERCE-22,
please visit www.clinicaltrials.gov
(NCT03123055).

About Rainier Therapeutics

Rainier Therapeutics, Inc. is a privately held, clinical stage
biotechnology company developing vofatamab, a targeted antibody, for the
potential treatment of metastatic bladder cancer. For more information,
please visit www.rainierrx.com.

Contacts

Julie Rathbun
Rathbun Communications
(206) 769-9291
[email protected]