Abstract 1876: INCB052793, a JAK1 selective inhibitor, is highly efficacious in PDX and xenograft models of acute myeloid leukemia (AML) expressing elevated endogenous pSTAT3/pSTAT5
Authors: Juvekar Ashish , Condon Sindy , Wen Xiaoming , Ruggeri Bruce , Scherle Peggy , Huber Reid , Li Yunlong , Yao Wenqing , Mei Song , Bhasin Deepak , Mancini Maria 
Published: August 2018

Abstract
Acute myeloid leukemia (AML) is characterized by infiltration of abnormally differentiated, clonal and highly proliferative cells of the hematopoietic system that acquire successive genomic alterations. AML is the most common acute leukemia in adults. Current therapies are of limited utility and involve a combination of cytarabine and anthracycline based regimens with allogeneic stem cell transplantation for eligible candidates, but there is an urgent need to improve therapies for AML. JAK/STAT pathway dysregulation plays a role in the pathogenesis of AML and the JAK2 V617F mutation is present in only a small percentage of these patients.
Studies were conducted to evaluate the in vitro and in vivo activities of INCB052793, a highly JAK1-selective inhibitor having 100-fold selectivity for JAK1 over JAK2 in cell lines, xenograft and PDX models of human AML having elevated endogenous pSTAT3 and or pSTAT5 activation. In vitro, INCB052793 effectively inhibited p-Stat3 and/or p-Stat5 phosphorylation MV411, Molm 16 and Molm 13 cell lines and caused marked reductions in p-Akt and c-Myc levels in MV411 and Molm16 cells. Given these observations, oral administration of INCB052793 was evaluated at doses of 3-30 mg/kg twice daily in MOLM-16 xenografts and FLT3-ITD AML xenograft models, MV-4-11 and Molm-13, in SCID mice. INCB052793 administration significantly inhibited tumor growth in MOLM-16 xenografts in a dose dependent manner and resulted in complete downregulation of p-Stat3 and p-Stat5 levels in MOLM-16 tumors. Similarly, INCB052793 administration was highly effective in inhibiting tumor growth in FLT3-ITD AML models, MV-4-11 and Molm-13. Administration of INCB052793 in a systemic PDX model of AML with elevated endogenous levels of p-Stat3 and p-Stat5 resulted in amelioration of disease severity and demonstrated a significant effect on median survival in leukemic SCID mice. All dosing regimens of INCB052793 in both xenograft and PDX models were well tolerated. Since azacitidine and cytarabine are standards of care for the treatment of AML, the efficacy of INCB052793 was benchmarked against optimal dosing regimens of these agents. In the AML xenograft models evaluated, INCB052793 was comparably or more efficacious in reducing tumor burden than azacitidine and cytarabine. The combination of INCB052793 with cytarabine showed superior efficacy in comparison to single agents in the MOLM-16 xenograft model, and combinatorial studies are in progress in additional AML models. These findings suggest the therapeutic potential of INCB052793 as a single agent and in combination with standard of care chemotherapeutic regimens for the management of AML.
Citation Format: Ashish Juvekar, Sindy Condon, Xiaoming Wen, Bruce Ruggeri, Peggy Scherle, Reid Huber, Yunlong Li, Wenqing Yao, Song Mei, Deepak Bhasin, Maria Mancini. INCB052793, a JAK1 selective inhibitor, is highly efficacious in PDX and xenograft models of acute myeloid leukemia (AML) expressing elevated endogenous pSTAT3/pSTAT5 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1876.