Abstract 1400: AS-1763: a highly potent, noncovalent and next generation BTK inhibitor for the treatment of patients with B-cell malignancies having C481S mutation in BTK

Abstract

Abstract Introduction: Bruton's tyrosine kinase (BTK) has been recently recognized as a validated drug target for the treatment of B-cell malignances. The emergence of clinical resistance to the first-generation covalent BTK inhibitors is, however, becoming a serious concern. Patients are reported to develop resistance during the treatment due to substitution of cysteine residue at position 481 with serine (C481S mutation) in BTK, which prevents the covalent binding of the first-generation irreversible BTK inhibitors, resulting in the loss of inhibitory activities. Therefore, there is a high unmet medical need for new therapeutic approaches to overcome the BTK C481S-mediated resistance. Material and methods: Compounds were tested in biochemical assays using recombinant human wildtype (WT) and C481S mutant BTKs. Cellular activity of AS-1763 was evaluated in human diffuse large B cell lymphoma (DLBCL) cell lines, OCI-Ly10 and its BTK[C481S] knock-in cells. The in vivo antitumor activity of AS-1763 was assessed in two tumor xenograft mouse models bearing WT or BTK [C481S] knock-in OCI-Ly10 cells. Results: We have discovered AS-1763 as an orally available, highly potent, selective and reversible BTK inhibitor. AS-1763 showed potent inhibitory activities for WT BTK (an activated form, BTK[A]) and the C481S mutant with sub-nanomolar IC50s (IC50 = 0.85 and 0.99 nM for BTK[A] and BTK[C481S], respectively). In cellular assays, AS-1763 exhibited strong antiproliferative activities for WT and BTK [C481S] knock-in OCI-Ly10 cells. AS-1763 demonstrated significant tumor growth inhibition and tumor regression in WT as well as BTK[C481S] knock-in OCI-Ly10 xenograft model. Conclusions: The preclinical data support the clinical development of AS-1763 in patients with B-cell malignancies both having WT and C481S mutation in BTK. The first-in-human Phase 1 clinical trial of AS-1763 in healthy volunteers (EudraCT 2020-005599-37) is currently ongoing, and the Phase 1b study in patients is expected to begin in 2022. Citation Format: Wataru Kawahata, Tokiko Asami, Takao Kiyoi, Takayuki Irie, Shigeki Kashimoto, Hatsuo Furuichi, Masaaki Sawa. AS-1763: a highly potent, noncovalent and next generation BTK inhibitor for the treatment of patients with B-cell malignancies having C481S mutation in BTK [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1400.