Five Prime Presents on Novel B7-H4 Therapeutic Antibody at the 2018 AACR Annual Meeting

Five Prime Therapeutics, Inc. FPRX, a clinical-stage biotechnology company focused on discovering and developing innovative immuno-oncology protein therapeutics, announced that an oral presentation featuring FPA150, Five Prime's first-in-class B7-H4 antibody, was given today at the 2018 AACR Annual Meeting in Chicago. The presentation titled "FPA150: A Recombinant, Afucosylated, Fully Human IgG1 Monoclonal Antibody for the Treatment of Malignancies that Express High Levels of B7-H4" by Charles Kaplan is available at http://www.fiveprime.com/news-media/publications-presentations

FPA150 is a novel B7-H4 antibody that possesses both T cell immune checkpoint blockade and antibody-dependent cellular cytotoxicity (ADCC) activities. FPA150 demonstrates dose-dependent anti-tumor activity in vivo as a monotherapy and elicits complete tumor regressions in preclinical tumor models when given in combination with PD-1 blockade. Five Prime is currently studying FPA150 in a Phase 1 monotherapy trial in patients with solid tumors that overexpress B7-H4.

"Our monoclonal B7-H4 antibody, FPA150, appears to possess both T cell checkpoint blockade activity and enhanced ADCC," said Bryan Irving, Ph.D., Senior Vice President of Research, at Five Prime. "We are studying FPA150 in patients whose tumors overexpress B7-H4 and in which there is high unmet need for immuno-oncology treatments, such as in breast, ovarian and endometrial cancer. Based on the therapeutic properties of FPA150, we believe that this agent has the potential to be an effective therapeutic by improving anti-tumor immune responses in cancer patients."

B7-H4 is a member of the B7-family of T cell immune checkpoint ligands and shares significant homology with other family members, including PD-L1 and PD-L2. B7-H4 is expressed in several human tumors such as carcinomas of the bladder, breast, ovary and endometrium, and its expression tends to correlate with poor prognosis. B7-H4 is also a documented T cell immune checkpoint inhibitory ligand capable of directly suppressing T cell responses.

In Investigational New Drug (IND)-enabling pharmacokinetics (PK) and toxicity studies, FPA150 demonstrated a suitable PK profile and was generally well tolerated. A B7-H4 immunohistochemistry (IHC) assay is in development for clinical use as a companion diagnostic to help identify the patients who might benefit most from this treatment.

Five Prime is studying FPA150 in a Phase 1 monotherapy trial 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 FPA150

FPA150 is a novel, fully human, afucosylated monoclonal antibody targeting B7-H4. B7-H4 expression is observed in multiple solid tumors, including breast, bladder, ovarian and endometrial 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. FPA150 is currently being studied in a Phase 1 clinical trial in advanced or metastatic breast, ovarian, endometrial and bladder cancers.

About Five Prime Therapeutics

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 www.fiveprime.com or follow us on LinkedIn, Twitter and Facebook.

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