06 March 2025, Shanghai—Abbisko Therapeutics Co., Ltd. (“Abbisko” hereafter) today announced that the Center for Drug Evaluation (CDE) of the China National Medical Products Administration (NMPA) has cleared the IND application for ABSK131, a highly-selective small molecule inhibitor of PRMT5*MTA. Earlier in December 2024, ABSK131 received IND clearance from the U.S. FDA.

A phase 1 clinical study in patients with advanced solid tumors will be conducted under the title “A Phase 1, First-in-Human, Multicenter, Open-Label Study of ABSK131 to Assess Safety, Tolerability, Pharmacokinetics, and Preliminary Efficacy in Patients with Advanced/Metastatic Solid Tumors”. The study population will primarily consist of patients with MTAP gene deficiency.

Approximately 15% of solid tumors lack expression of methylthioadenosine phosphorylase (MTAP), a tumor suppressor gene [1]. Solid tumors with high rates of MTAP deficiency include non-small cell lung cancer (NSCLC) (15.7%), pancreatic cancer (21.7%), esophageal cancer (28.4%), mesothelioma (32.2%), and gastrointestinal cancer (10.4% of gastric and 1% of colorectal cancer)[2], of which mesotheliomas and pancreatic cancers have no approved targeted therapies.

MTAP encodes a key rate-limiting enzyme in the metabolism of polyamines and purines and plays a major role in the purine/methionine salvage pathway[3]. MTAP deficiency causes accumulation of its substrate methylthioadenosine (MTA) that inhibits protein arginine methyltransferase 5 (PRMT5) [4]. PRMT5 is an enzyme that catalyzes the symmetrical transfer of two methyl groups from S-adenosyl methionine (SAM) to arginine residues on proteins, influencing various physiological processes, including transcription, RNA splicing, ribosome biogenesis, and cell cycle regulation [5-6]. PRMT5 has been found to exhibit synthetic lethality in MTAP-deficient tumors [7-9]. Recent studies have demonstrated that selectively targeting PRMT5*MTA shows promise as a therapeutic strategy for MTAP-deficient cancers.

About ABSK131

ABSK131 is a novel, small molecule MTA-cooperative PRMT5 inhibitor in development by Abbisko Therapeutics. In preclinical studies, ABSK131 demonstrated excellent selectivity for MTAP-deleted cancer cells, as well as favorable drug metabolism and pharmacokinetic properties for oral dosing.

References:

1. Kalev P, Hyer ML, Gross S, et al. MAT2A Inhibition Blocks the Growth of MTAP-Deleted Cancer Cells by Reducing PRMT5-Dependent mRNA Splicing and Inducing DNA Damage. Cancer Cell. 2021;39(2):209-224.e11. doi:10.1016/j.ccell.2020.12.010

2. Bertino JR, Waud WR, Parker WB, Lubin M. Targeting tumors that lack  methylthioadenosine phosphorylase (MTAP) activity: current strategies. Cancer Biol Ther. 2011;11(7):627-632. doi:10.4161/cbt.11.7.14948.

3. de Menezes WP, Silva VAO, Gomes INF, Rosa MN, Spina MLC, Carloni AC, et al. Loss of 5′-methylthioadenosine phosphorylase (MTAP) is frequent in high-grade gliomas; nevertheless, it is not associated with higher tumor aggressiveness. Cells. 2020;9(2):492.

4. Bray C, Balcells C, McNeish IA, Keun HC. The potential and challenges of targeting MTAP-negative cancers beyond synthetic lethality. Front Oncol. 2023;13:1264785. Published 2023 Sep 19. doi:10.3389/fonc.2023.1264785.

5. Blanc RS, Richard S. Arginine Methylation: The Coming of Age. Mol Cell. 2017;65(1):8-24.

6. Kim H, Ronai ZA. PRMT5 function and targeting in cancer. Cell Stress. 2020;4(8):199-215.

7. Kryukov GV, Wilson FH, Ruth JR, Paulk J, Tsherniak A, Marlow SE, et al. MTAP deletion confers enhanced dependency on the PRMT5 arginine methyltransferase in cancer cells. Science. 2016;351(6278):1214-8.

8. Marjon K, Cameron MJ, Quang P, Clasquin MF, Mandley E, Kunii K, et al. MTAP Deletions in Cancer Create Vulnerability to Targeting of the MAT2A/PRMT5/RIOK1 Axis. Cell Rep. 2016;15(3):574-87.

9. Mavrakis KJ, McDonald ER, 3rd, Schlabach MR, Billy E, Hoffman GR, deWeck A, et al. Disordered methionine metabolism in MTAP/CDKN2A-deleted cancers leads to dependence on PRMT5. Science. 2016;351(6278):1208-13.