LAUSR

e14604Background: There is great interest in investigating immune checkpoint inhibition in combination with novel agents, however, preclinical studies are limited by the lack of immune-competent human cancer cell line xenograft models. We developed a “hematopoietic” humanized mouse model to address this unmet need. HDAC inhibitors (HDACi) induce T-cell chemokine expression and enhance response to PD1 inhibitors in lung cancer models. We evaluated the combination of OKI-179, a novel Class I HDACi and nivolumab in our humanized mouse model. Methods: BRGS newborn pups were transplanted with CD34+ cells purified from umbilical cord blood. At 16 weeks, MDA-MB-231 cells were implanted in the flanks of the mice. When the average tumor size reached ~150-300 mm3, the mice were randomized into vehicle, nivolumab, OKI-179, or the combination treatment according to % chimerism. At the end of the treatment, mice were euthanized and tissues were collected for further analysis. Results: We observed a statistically signi...