Five Prime Therapeutics Initiates Patient Dosing in Phase 1/2 Clinical Trial Evaluating FPA008 in Pigmented Villonodular Synovitis

SOUTH SAN FRANCISCO, Calif., July 13, 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 the company has initiated patient dosing in its Phase 1/2 clinical trial of FPA008, a CSF1 receptor antibody, in pigmented villonodular synovitis (PVNS).

"PVNS is characterized by inflammatory tumor growth in and around a joint cavity. These tumors cause significant joint destruction, pain, and other problems for patients, and no approved systemic therapy currently exists," said Robert Maki, MD, PhD, Professor of Medicine, Pediatrics, and Orthopaedics at Mount Sinai Medical Center, New York, NY. "Nearly all cases of PVNS are driven by a specific DNA change in which CSF1 protein is produced at abnormally high levels and causes accumulation of inflammatory cells in the joints, so a well-tolerated treatment that blocks CSF1 receptor binding is ideally suited for this disease. Based on its profile to date, FPA008 appears to be a promising candidate for development in this indication."

During the Phase 1 dose escalation part of the trial, Five Prime will assess the safety and pharmacodynamics of multiple ascending doses of FPA008 to determine the dose for expansion. During the Phase 2 expansion phase, the company will evaluate response rate and duration, as well as measures of pain and joint function, in approximately 30 patients. Initial data from the Phase 1 dose escalation portion are expected by late 2015 or early 2016.

"The expansion of our FPA008 program highlights the broad potential of targeting the CSF1 receptor pathway in a variety of therapeutic areas, and in mid-2015 we expect to have clinical development underway in eight disease settings," said Julie Hambleton, MD, Chief Medical Officer of Five Prime. "In the new Phase 1/2 trial in PVNS, we are evaluating our antibody in an orphan disease for which patients have few options beyond surgery. Our immuno-oncology clinical collaboration with Bristol-Myers Squibb will explore FPA008 in combination with the PD-1 immune checkpoint antibody, nivolumab, in a Phase 1a/1b trial in non-small cell lung cancer, melanoma, head and neck cancer, pancreatic cancer, colorectal cancer and malignant glioma. Finally, our ongoing Phase 1 study is completing dosing in the open-label portion of the trial in rheumatoid arthritis patients."

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 major 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 www.fiveprime.com.

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 about (i) the timing of initiation, progress and scope of clinical trials for Five Prime's FPA008 product candidate; and (ii) the reporting of clinical results regarding Five Prime's FPA008 product candidate. Many factors may cause differences between current expectations and actual results, including unexpected safety or efficacy data observed during preclinical or clinical studies, clinical trial site activation or enrollment rates that are lower than expected, unexpected delays or challenges in discussions with regulatory authorities, changes in expected or existing competition and the failure of Five Prime's collaborator, BMS, to support or advance the development of FPA008 as currently expected. 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.

CONTACT: Amy Kendall, Corporate Communications 415-365-5776 amy.kendall@fiveprime.com

Source:Five Prime Therapeutics, Inc.