Abstract 1463: ATP-site inhibitor olverembatinib, HQP1351, enhanced the effect of allosteric inhibitor on the resistance conferred by the compound mutations of BCR-ABL
Authors: Wang Guangfeng , Lv Jing , Tang Chunyang , Min Ping , Rui Li , Zhang Fei , Wang Lvcheng , Ge Yangfeng , Lian Kejie , Liang Eric , Yang Dajun , Zhai Yifan 
Published: July 2021

Abstract
Treatment with tyrosine kinase inhibitors (TKIs) directed against the ATP-binding site of BCR-ABL promotes recovery of Ph+ leukemia. However, emergence of gatekeeper mutation T315I and compound mutants confer resistance to these TKIs. The allosteric inhibitor, asciminib, effectively inhibits BCR-ABL kinase through binding to the myristoyl-binding site. Combining asciminib with ponatinib can overcome only a subset of the resistance caused by BCR-ABL compound mutants. Olverembatinib (HQP1351) is a new generation TKI targeting BCR-ABL and currently in development for r/r CML. The purpose of this study is to evaluate whether a novel combination of olverembatinib and asciminib, targeting both ATP pocket and allosteric region of BCR-ABL protein, can promote the inhibitory effect on the kinase harboring compound mutations. A series of cell lines expressing BCR-ABL single or compound mutations were constructed based on BaF3 murine pro-B cell line. Effect of olverembatinib as a single agent or in combination with asciminib were analyzed using antiproliferation assay, Western blot and FACS assays in vitro. In vivo efficacy was evaluated using the syngeneic mouse model derived from BaF3 cells with T315I or compound mutations. The cell based antiproliferation studies demonstrated superior activity of olverembatinib toward BCR-ABL single or compound mutations with IC50 values ranging between 6-300 nM. In particular, olverembatinib was more effective than ponatinib, asciminib and other TKIs against those compound mutations. Moreover, the combination of olverembatinib with asciminib was highly effective against BCR-ABL compound mutations, especially those containing T315I. In vivo studies further revealed that co-administration of olverembatinib with asciminib resulted in significant prolongation of survival compared to single agents. Importantly, the anti-tumor effect was more potent than that of ponatinib plus asciminib in models harboring compound mutations. In terms of mechanism, the combined treatment synergistically downregulated phosphorylation of BCR-ABL and the downstream proteins CRKL and STAT5, and augmented cleavage of Caspase-3 and PARP-1, thus triggered apoptosis and subsequently enhanced the antitumor effects. Our results demonstrated that the combination of ATP binding site inhibitor olverembatinib and allosteric inhibitor have synergistic anti-tumor effect on tumor cells harboring single or compound mutations in BCR-ABL. This novel strategy may help to overcome the secondary compound mutations post the treatment with TKIs.
Citation Format: Guangfeng Wang, Jing Lv, Chunyang Tang, Ping Min, Li Rui, Fei Zhang, Lvcheng Wang, Yangfeng Ge, Kejie Lian, Eric Liang, Dajun Yang, Yifan Zhai. ATP-site inhibitor olverembatinib, HQP1351, enhanced the effect of allosteric inhibitor on the resistance conferred by the compound mutations of BCR-ABL [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1463.