On April 3, 2017 Five Prime Therapeutics, Inc. (Nasdaq:FPRX), a clinical-stage biotechnology company focused on discovering and developing innovative immuno-oncology protein therapeutics, reported that a poster featuring preclinical data related to Five Prime’s CSF-1R antibody, cabiralizumab (FPA008), was presented today at the 2017 American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting in Washington, D.C (Press release, Five Prime Therapeutics, APR 3, 2017, View Source [SID1234518423]). The poster titled "Antibody-Based Inhibition of CSF-1R as a Component of Combination Immunotherapy in Preclinical Models" is available at View Source

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"These preclinical findings suggest that the surrogate antibody for FPA008 significantly reduces tumor growth in murine syngeneic tumor models when administered alone and when administered in combination with a PD-1 antibody," said Kevin Baker, Ph.D., Senior Vice President of Development Sciences at Five Prime. "These findings support previous preclinical data that served as the basis for our Phase 1a/1b clinical trial that we are running in collaboration with Bristol-Myers Squibb (BMS) to investigate the use of cabiralizumab in combination with nivolumab (anti-PD-1, OPDIVO) in six different tumor types."

The colony stimulating factor 1 receptor (CSF-1R) signaling pathway promotes tumor progression via the recruitment, differentiation, and survival of immuno-suppressive, M2 polarized, tumor-associated macrophages (TAMs). Five Prime has developed cabiralizumab (FPA008), an IgG4 antibody against CSF-1R that blocks the ability of both CSF-1 and IL-34 to bind and activate this receptor, thereby modulating the immune response to tumorigenesis.

Five Prime has identified alterations in the tumor microenvironment that occur upon CSF-1R inhibition, including significant reduction of immunosuppressive M2 TAMs and an increase in tumor PD-L1 expression. Notably, when dosing in combination, the blockade of CSF-1R and PD-1/PD-L1 results in a significant increase in CD8+ T cells within the tumor. The results show that, when added to PD-1/PD-L1 blockade, the surrogate antibody for FPA008 can significantly enhance anti-tumor efficacy.