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Five Prime Therapeutics Announces Collaboration with Roche to Develop Companion Diagnostics for Targeted Immuno-Oncology Investigational Drug Candidates


Five Prime Therapeutics, Inc. (NASDAQ:FPRX), a clinical-stage
biotechnology company focused on discovering and developing innovative
immuno-oncology protein therapeutics, today announced it has entered
into a collaboration with Roche to develop immunohistochemistry (IHC)
companion diagnostic assays for use with Five Prime's first-in-class
investigational drug candidates, bemarituzumab, an anti-FGFR2b antibody
(also known as FPA144), and FPA150, a B7-H4 antibody.

"We are pleased to collaborate with Roche, a world leader and innovator
of tissue-based diagnostic solutions, to identify patients with advanced
cancers who might be eligible for treatment with our targeted
immuno-oncology agents," said Aron Knickerbocker, chief executive
officer of Five Prime Therapeutics, Inc. "We believe targeted therapies,
such as bemarituzumab and FPA150, could provide clinical benefit to
patients. Roche's tissue-based assays will be important tools to help us
identify the patients who might benefit most from these treatments."

Five Prime and Roche are collaborating to develop, validate and
commercialize a tissue-based IHC companion diagnostic (CDx) assay to
help identify patients whose tumors overexpress FGFR2b and are eligible
for treatment with bemarituzumab. The CDx assay will be used in Five
Prime's global registrational study of bemarituzumab in combination with
5-fluorouracil (5-FU), leucovorin, and oxaliplatin, a regimen known as
mFOLFOX6, as front-line treatment in patients with advanced gastric or
gastroesophageal junction cancer whose tumors overexpress FGFR2b or have FGFR2
gene amplification (the FIGHT trial) that Five Prime expects to
start in the second half of 2018. Five Prime plans to use the Roche IHC
assay along with a circulating tumor DNA (ctDNA) test in the FIGHT trial
to identify the estimated 10 percent of patients with gastric and
gastroesophageal junction cancer who would be eligible for treatment
with bemarituzumab.

Five Prime and Roche will also collaborate to develop and validate a
tissue-based IHC diagnostic assay for use as a laboratory developed test
(LDT) to help identify patients whose tumors overexpress B7-H4. Five
Prime plans to use this IHC assay in the expansion portion of the
ongoing Phase 1 clinical trial of FPA150 to identify patients with
advanced or metastatic breast, ovarian, endometrial and bladder cancers
whose tumors overexpress B7-H4.

Financial terms of the agreement were not disclosed.

About Bemarituzumab

Bemarituzumab is a first-in-class, isoform-selective, humanized
monoclonal antibody in clinical development as a targeted immunotherapy
for tumors that overexpress FGFR2b, a splice variant of a receptor for
some members of the fibroblast growth factor (FGF) family, or amplify
the FGFR2 gene. Bemarituzumab has been engineered for enhanced
antibody-dependent cell-mediated cytotoxicity (ADCC) to increase direct
tumor cell killing by recruiting natural killer (NK) cells. Clinical
results to date suggest that the specificity of bemarituzumab avoids the
dose-limiting toxicities that have been seen with less selective
pan-FGFR tyrosine kinase inhibitors that act on multiple FGFRs,
including FGFR2.

Bemarituzumab is being evaluated in the FGF2b
Inhibition in Gastric
and Gastroesophageal Junction Cancer Treatment
(FIGHT) Phase 1/3 clinical trial, a global registrational study in
patients with advanced gastric or gastroesophageal junction cancer whose
tumors overexpress FGFR2b or have FGFR2 gene amplification. The
Phase 3 portion of the trial is expected to begin in the second half of
2018. In December 2017, Five Prime and Zai Lab announced a collaboration
for the development and commercialization of bemarituzumab in Greater
China. Zai Lab will manage the Phase 3 portion of the FIGHT trial in

About FPA150

FPA150 is a first-in-class, fully human, afucosylated monoclonal
antibody targeting B7-H4. B7-H4 expression is observed in multiple solid
tumors, including breast, bladder and gynecologic cancers, and has been
documented to correlate with poor prognosis. FPA150 is designed with a
dual mechanism of action: blocking the T cell checkpoint activity of
B7-H4 as well as delivering potent ADCC against tumor cells expressing
B7-H4. B7-H4 is being studied in a Phase 1 trial of monotherapy FPA150
with a dose-escalation phase in patients with solid tumors, followed by
dose expansion in pre-specified cohorts in tumor types based on B7-H4
expression levels. The initial targeted tumors are advanced or
metastatic breast, ovarian, endometrial and bladder cancers.

About Five Prime

Five Prime Therapeutics, Inc. discovers and develops innovative
therapeutics to improve the lives of patients with serious diseases.
Five Prime's comprehensive discovery platform, which encompasses
virtually every medically relevant extracellular protein, positions it
to explore pathways in cancer, inflammation and their intersection in
immuno-oncology, an area with significant therapeutic potential and the
focus of the company's R&D activities. Five Prime has entered into
strategic collaborations with leading global pharmaceutical companies
and has promising product candidates in clinical and late preclinical
development. For more information, please visit
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Cautionary Note on Forward-looking Statements

This press release contains forward-looking statements within the
meaning of the Private Securities Litigation Reform Act of 1995. Words
such as "may," "will," "expect," "plan," "anticipate," "estimate,"
"intend" and similar expressions (as well as other words or expressions
referencing future events, conditions or circumstances) are intended to
identify forward-looking statements. These forward-looking statements
are based on Five Prime's expectations and assumptions as of the date of
this press release. Each of these forward-looking statements involves
risks and uncertainties. Actual results may differ materially from these
forward-looking statements. Forward-looking statements contained in this
press release include statements regarding (i) the timing of initiation,
progress and scope of clinical trials for Five Prime's product
candidates; and (ii) the extent of gene amplification and protein
overexpression in certain patient populations. Many factors may cause
differences between current expectations and actual results including
unexpected safety, efficacy or other data observed during research,
preclinical or clinical studies, changes in expected or existing
competition, changes in the regulatory environment, and unexpected
litigation or other disputes. Other factors that may cause actual
results to differ from those expressed or implied in the forward-looking
statements in this press release are discussed in Five Prime's filings
with the U.S. Securities and Exchange Commission, including the "Risk
Factors" contained therein. Except as required by law, Five Prime
assumes no obligation to update any forward-looking statements contained
herein to reflect any change in expectations, even as new information
becomes available.

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