Five Prime Therapeutics Announces The Presentation of Preliminary FPA008 Phase 1 Trial Data in Rheumatoid Arthritis Patients at the 2015 ACR Annual Meeting

SOUTH SAN FRANCISCO, Calif., Oct. 7, 2015 (GLOBE NEWSWIRE) -- Five Prime Therapeutics, Inc. (Nasdaq:FPRX), a clinical-stage biotechnology company focused on discovering and developing novel protein therapeutics for cancer and inflammatory diseases, today announced that preliminary data from rheumatoid arthritis (RA) patients in part 3 of Five Prime's ongoing Phase 1 trial of FPA008 will be presented during the upcoming 2015 American College of Rheumatology (ACR)/Association of Rheumatology Health Professionals Annual Meeting, to be held November 7-11, 2015 in San Francisco. FPA008 is Five Prime's anti-CSF1R antibody that blocks the binding of CSF1 and IL34 ligands to CSF1R, resulting in inhibition of the activation and survival of inflammatory macrophages and osteoclasts.

Abstract #2749 entitled, "A Phase 1 Study of FPA008, an Anti-Colony Stimulating Factor 1 Receptor (anti-CSF1R) Antibody in Patients (pts) with Rheumatoid Arthritis (RA): Preliminary Results," is accessible on the meeting website and includes data as of May 13, 2015. The poster presentation will take place during the session, Rheumatoid Arthritis - Small Molecules, Biologics and Gene Therapy Poster III, scheduled from 9:00-11:00 am Pacific Time on Tuesday, November 10, 2015. The poster is expected to include study data up to October 2015, which will be detailed in a press release during the conference.

The Phase 1 clinical trial of FPA008 is being conducted in three parts. Parts 1 and 2 involved dose administration and escalation in healthy volunteers and data on safety, pharmacokinetics, and biomarkers from this portion of the study were presented during the 2014 ACR Annual Meeting. Part 3 of the trial consists of an open-label evaluation of 3 dose levels of FPA008 in combination with methotrexate in RA patients whose disease is not responding to methotrexate therapy. The primary endpoint of the trial is safety, with secondary endpoints including PK, pharmacodynamics (PD) and disease activity as measured by ACR scores and joint MRI.

About FPA008

FPA008, an antibody that inhibits colony stimulating factor-1 receptor (CSF1R), targets macrophages and monocytes, which are activated or elevated in multiple disease settings. In cancer, tumor-associated macrophages suppress the immune system's ability to kill cancer cells. In joint diseases, such as pigmented villonodular synovitis (PVNS) and rheumatoid arthritis (RA), synovial macrophages play a central role in the disease process.

In the immuno-oncology clinical collaboration with Bristol Myers-Squibb, Five Prime is evaluating FPA008 in combination with the PD-1 immune checkpoint antibody, nivolumab, in six tumor types. Five Prime is also developing FPA008 in PVNS, an orphan disease driven by the CSF1R pathway, and is completing the open-label part of a Phase 1 trial in RA patients.

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 a growing 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

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. 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.

CONTACT: Amy Kendall,
         Corporate Communications