Rainier Therapeutics Presents Data on Vofatamab in Patients with Advanced Urothelial Cell Carcinoma (Bladder Cancer) Previously Treated with Chemotherapy at ASCO GU 2019

– Preliminary data from FIERCE-21 Phase 2 trial highlighted in oral
presentation supports advancement to pivotal study –

– Single agent activity and long-term treatment duration demonstrated –

SAN LEANDRO, Calif.–(BUSINESS WIRE)–Rainier Therapeutics, Inc., a privately-held clinical stage drug
development company, today announced the presentation of preliminary
data from its Phase 2 trial of vofatamab, a
fibroblast-growth-factor-receptor 3 (FGFR3) targeted antibody, at the
2019 ASCO Genitourinary Cancers Symposium in San Francisco. The study,
FIERCE-21, is evaluating vofatamab in combination with docetaxel and
vofatamab as monotherapy in patients with locally advanced or metastatic
bladder cancer with FGFR3 mutation/fusions who have relapsed after, or
are refractory to, at least one prior line of chemotherapy.

“There are limited and, in some cases, no approved treatment options for
patients with advanced metastatic bladder cancer who have failed
chemotherapy and, if indicated, checkpoint inhibitors. FGFR3 inhibitors
have the potential to revolutionize the clinical management of
metastatic bladder cancer in biomarker-selected and potentially poor
checkpoint responding patients,” said Andrea Necchi, M.D., Urologic
Oncology, Department of Medical Oncology, Fondazione IRCCS Istituto
Nazionale dei Tumori, Milan, Italy. “Vofatamab has the potential to be a
differentiated FGFR3 inhibitor with a tolerability and activity profile
that may provide a much-needed therapeutic option to patients.”

“We are pleased with this preliminary data in the FIERCE-21 trial that
indicate vofatamab is providing clinical benefit in a group of patients
at a very advanced stage of disease. Vofatamab in combination with
docetaxel is showing a benefit to patients in the trial that has
surpassed historical results of single-agent docetaxel in other trials.
In addition, single agent activity was also observed with vofatamab in a
heavily pretreated patient group,” said Steve Abella, M.D., Chief
Medical Officer, Rainier Therapeutics. “We look forward to reporting
further data later this year and believe the data reported today
supports moving forward with the planning of a pivotal trial of
vofatamab in combination with docetaxel intended to improve treatment
outcomes for this patient population.”

Details from the oral abstract presentation: “FIERCE-21: Phase II
study of vofatamab (B-701), a selective inhibitor of FGFR3, as salvage
therapy in metastatic urothelial carcinoma (mUC)
” (abstract #409)
are as follows:

FIERCE-21 Study Design/Prior Treatments

  • A total of 42 patients with bladder cancer previously treated with one
    or more prior lines of chemotherapy and, if available, a checkpoint
    inhibitor, were enrolled in two groups of 21. One study group received
    a combination of docetaxel (75mg/m2) followed by an
    infusion of vofatamab (25mg/kg). The other group received vofatamab
    (25mg/kg) as monotherapy. Study treatment was administered on day one
    of each 21-day cycle.
  • In the combination group receiving vofatamab and docetaxel, 57 percent
    of patients had received a median of two or more prior lines of
    therapy (range 1-4) and 71 percent of patients in the vofatamab
    monotherapy group had received a median of three or more prior
    therapies (range 1-7). More than 50 percent of patients in both arms
    had received prior checkpoint therapy treatment.
  • The primary endpoints of the study are safety and efficacy as measured
    by objective response rate (ORR), progression free survival (PFS) and
    overall survival (OS).

Preliminary FIERCE-21 Results

  • Of 21 evaluable patients who received the combination therapy of
    vofatamab plus docetaxel:

    • A preliminary disease control rate (DCR) of 27 percent (at 180
      days) was reported.
    • Fifty-seven percent of these patients remain on study and 43
      percent remain on treatment at the time of the data analysis.
    • Patients continue to be followed for ORR, PFS and OS.
  • Of 21 evaluable patients in the vofatamab monotherapy cohort:

    • A median PFS of 4 months was reported in fourth line patients
    • A preliminary DCR of 21 percent (at 180 days) was reported.
    • Fifty-seven percent of these patients remain on study and 19
      percent remain on treatment at the time of the data analysis.
    • Patients continue to be followed for ORR and OS.
  • In both groups, treatment was generally well-tolerated, with the most
    common vofatamab-related adverse events being asthenia, diarrhea,
    decreased appetite and rash; all were Grade 1 or 2. There were few
    dose interruptions and discontinuations. No cases of severe skin/nail
    toxicity, hyperphosphatemia, or ocular events were reported.

The full poster can be viewed on the Rainier Therapeutics website at: http://www.rainierrx.com/posters/.

About Bladder Cancer

Bladder cancer is the fifth most common cancer in each of the United
States and Europe. Over the past 30 years, the only novel therapies
approved in the United States for bladder cancer patients have been
checkpoint inhibitors for patients who failed first line chemotherapies.
Several immune check point inhibitors targeting the programmed cell
death-1 or PD-1 or programmed cell death ligand-1, or PDL-1 pathway,
have been approved by the FDA for use in bladder cancer patients who
have failed platinum-based chemotherapy. Despite these developments,
objective response rates in clinical trials with checkpoint inhibitors
have been between 15% and 21%, when used as salvage therapy, with median
overall survival reported between 8-10 months and limited benefit in
progression-free survival, leaving patients with bladder cancer with a
high unmet need for effective and tolerable therapies.

In addition, studies have shown that bladder cancer tumors with genetic
alterations in FGFR3 have inappropriate FGFR3 signaling driven by these
genetic alterations or overexpression and are implicated in the
development of bladder cancer. Tolerable and effective therapies for
these patients in advanced and metastatic bladder cancer are needed.

About Vofatamab

Vofatamab 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 biologic specific for FGFR3 known by Rainier Therapeutics to be
in clinical development.

In addition to FIERCE-21, Rainier Therapeutics has an ongoing Phase 2
clinical trial, FIERCE-22. FIERCE-22 is 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-21, please visit www.clinicaltrials.gov
NCT02401542
and for more information on FIERCE-22, please visit www.clinicaltrials.gov
(NCT03123055)
.

Rainier Therapeutics also plans to study vofatamab in non-muscle
invasive bladder cancer (NMIBC) – the FIERCE-23 trial. This trial is
planned to start in 2019.

About Rainier Therapeutics

Rainier Therapeutics, Inc. is a privately-held, clinical stage
biotechnology company developing a targeted biologic for the potential
treatment of metastatic bladder cancer. The company’s antibody,
vofatamab (formerly B-701), is focused specifically on the fibroblast
growth factor receptor 3 (FGFR3), a known driver of bladder and other
cancers. For more information, please visit www.rainierrx.com.

Contacts

Robert Uhl
Westwicke Partners, LLC
Robert.uhl@westwicke.com
(858)
356-5932

Julie Rathbun
Rathbun Communications
(206) 769-9291
julie@rathbuncomm.com

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