Five Prime Therapeutics Doses First Patient in Phase 1b Trial of FPA150

SOUTH SAN FRANCISCO, Calif.--(BUSINESS WIRE)-- Five Prime Therapeutics, Inc. (NASDAQ: FPRX), a clinical-stage biotechnology company focused on discovering and developing innovative immuno-oncology protein therapeutics, today announced that it initiated patient dosing in the Phase 1b dose expansion portion of the Phase 1a/1b clinical trial of FPA150 (FPA150-001; NCT03514121), a first-in-class immuno-oncology antibody that targets B7-H4.

“We are very pleased with the progress of our FPA150 clinical program that began with a dose escalation study in solid tumors and rapidly proceeded to an exploratory basket cohort of tumors that over-express B7-H4,” said Helen Collins, Senior Vice President and Chief Medical Officer. “We have now dosed the first patient in the Phase 1b dose expansion portion of the trial. FPA150 specifically targets B7-H4, which is in the same family of checkpoint inhibitors as PD-L1 and is over-expressed in breast and gynecological cancers that are not well served by immunotherapy. We are hopeful that a targeted immunotherapy like FPA150 will provide clinical benefit to these patients who have limited treatment options.”

The objective of the Phase 1b dose expansion is to evaluate the safety, tolerability, pharmacokinetics (PK) and potential preliminary clinical benefit of FPA150 monotherapy in patients with breast, ovarian and endometrial cancers that over-express B7-H4. A subgroup of patients in the Phase 1b portion will undergo pre- and on-treatment biopsies to assess the pharmacodynamic effects of FPA150 on the tumor and the tumor microenvironment, including changes in markers of tumor immune infiltrates and cytokine levels. Endpoints for the Phase 1b portion include objective response rate (ORR), duration of response and progression-free survival (PFS).

About FPA150

FPA150 is a novel, fully human, afucosylated monoclonal antibody targeting B7-H4. B7-H4 expression is observed in multiple solid tumors, including breast and gynecologic cancers. FPA150 is designed with a dual mechanism of action: blocking the T cell checkpoint activity of B7-H4 as well as delivering ADCC against tumor cells expressing B7-H4.

About Five Prime Therapeutics

Five Prime Therapeutics, Inc. discovers and develops innovative protein therapeutics to improve the lives of patients with serious diseases. Our product candidates have innovative mechanisms of action and address patient populations in need of better therapies. The company focuses on researching and developing immuno-oncology and targeted cancer therapies paired with companion diagnostics to identify patients who are most likely to benefit from treatment with our product candidates. Five Prime has entered into strategic collaborations with leading global pharmaceutical companies and has promising product candidates in clinical and preclinical development. For more information, please visit www.fiveprime.com or follow us on LinkedIn, Twitter and Facebook.

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.

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