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Blockade of the checkpoint inhibitor PD-1 has demonstrated remarkable success in the clinic for the treatment of a growing list of different cancers. However, several tumor types are resistant to anti-PD-1 monotherapy. This observation has spurred numerous combination studies to reveal what additional therapeutic interventions may complement anti-PD1 blockade. Recently it has been shown that immunogenic cell death (ICD), induced by radiation and/or chemotherapy, improves T cell responses against different tumor types. ICD is characterized by damage-associated molecular patterns (DAMPs) including surface expression of calreticulin, and release of ATP and HMGB1. Recognition of DAMPs triggers dendritic cell maturation and functions that are critical for tumor antigen-specific T cell activation. Thus therapies that evoke ICD may further augment anti-tumor immunity elicited by anti-PD-1. In mouse syngeneic tumor models, we observed combinatorial anti-tumor activity of anti-PD1 and the cyclin-dependent kinase inhibitor, dinaciclib. We hypothesized that dinaciclib potentiates the effects of anti-PD-1 by eliciting ICD. Indeed, tumor cells treated with dinaciclib express the hallmarks of ICD including HMGB1 and ATP release and surface expression of calreticulin. Dinaciclib treatment also increases tumor cell phagocytosis and induces dendritic cell maturation. Furthermore, mice immunized with dinaciclib-treated tumor cells are resistant to subsequent tumor challenge. Tumors from mice receiving anti-PD1 and dinaciclib have increased T cell infiltration and dendritic cell activation, indicating the overall quality of the immune response generated may be improved with the combo. Taken together, these findings suggest a potential mechanism for the observed synergy between dinaciclib and anti-PD1. Dinaciclib induces immunogenic cell death, converting the tumor cell into an endogenous vaccine and thereby boosting the effects of anti-PD-1. Citation Format: Dewan Mohammed Sakib Hossain, Fernando Ugarte, Anandi Sawant, Mingmei Cai, Venkataraman Sriram, Elaine Pinheiro, Svetlana Sadekova, Alissa Chackerian. Dinaciclib induces immunogenic cell death and enhances anti-PD-1 mediated tumor suppression. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 562.