Abstract 1621: L105, a next generation of Bcl-2 inhibitor, overcomes Bcl-2 mutation and exhibits superior antitumor activity
Authors: Liu Xingguo , Lou Yang , Wu Yizhe , Su Mingbo , Gao Anhui , Huang Jinglai , Zhong Li , Zhou Xinglu 
Published: April 2023

Abstract
Background: The Bcl-2 inhibitor venetoclax is approved for the treatment of chronic lymphocytic leukemia (CLL), small lymphocytic lymphoma (SLL) and acute myeloid leukemia (AML). However, disease progression occurs when Ventoclax long-term treatment as a single agent driven by the recurrent Bcl-2 mutations, such as G101V, D103Y, D103E, et al. Here, we described the discovery of a next generation Bcl-2 inhibitor L105 with high potency against Bcl-2, Bcl-2(G101V) and Bcl-2(D103Y) for treatment of Bcl-2 dependent and venetoclax resistant hematological cancers.
Methods: Biochemical inhibition assays were conducted by TR-FRET based assay. Proliferation inhibition assays on a panel of hematologic tumor cells were carried out by MTS assay. Caspase-3 activation in RS4;11 was determined by western blot. Preclinical pharmacokinetics studies were assayed in mice and dogs and parameters were determined by LC-MS. In vivo pharmacodynamic studies were performed in RS4;11 and OCI-LY10 derived xenograft SCID mouse models. In vitro human platelet toxicity was measured by CellTiter-Glo assay. Cytochrome P450 inhibition was measured in fluorometric assay.
Results: In biochemical assays, the IC50 of L105 against Bcl-2 WT, Bcl-2 G101V, Bcl-2 D103Y, Bcl-2 D103E with IC50 of 0.42, 0.83, 0.97 and 5.78 nM respectively,while those of venetoclax were 1.89, 704.27, 470.19 and 243.30 nM respectively. In cellular assays, the IC50 of L105 in RS4;11, RS4;11 overexpressing Bcl-2 G101V, OCI-LY10, MV4-11, Mino, Toledo, Maver-1, SU-DHL-6 and REC-1 were 0.30-243.36 nM, while those of venetoclax were 2.91-3360.79 nM. L105 showed &gt;2000 folds Bcl-2 selectivity over Bcl-xL. Furthermore, in vitro platelet viability assay showed L105 induced hypotoxicity at similar level of venetoclax. In pharmacodynamics studies, 5mpk L105 induced more rapid and robust antitumor effect in RS4;11 xenograft than venetoclax at 10 mpk did, and 15mpk L105 showed significant longer and stronger tumor suppression response than venetoclax at 25 mpk did. In the preclinical pharmacokinetic (PK) studies, L105 showed excellent PK properties in ICR mice and beagle dogs, in terms of long T1/2 and high dose-normalized AUC. L105 also exhibited a less drug-drug interaction potential, as no evidence on CYPs inhibition (IC50 &gt;20 μM), while venetoclax potently inhibited CYP2C9 with IC50 at 1.12 μM. In 14-days oral gavage toxicity study in mice, no compound related deaths occurred at 15, 50 and 300 mpk, and only leukopenia was observed at similar level of venetoclax.
Conclusions: L105 showed great potency on wild type and acquisition resistance mutations of Bcl-2, excellent oral bioavailability, and superior preclinical anti-tumor activities and safety profiles. It may provide new thoughts on treatment for a wide range of Bcl-2-dependent and Venetoclax-resistant hematological cancers.
Citation Format: Xingguo Liu, Yang Lou, Yizhe Wu, Mingbo Su, Anhui Gao, Jinglai Huang, Li Zhong, Xinglu Zhou. L105, a next generation of Bcl-2 inhibitor, overcomes Bcl-2 mutation and exhibits superior antitumor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1621.