Abstract 6241: LP-184, an acylfulvene class small molecule therapeutic, is synthetically lethal in DNA damage repair deficient cancers

Abstract

Abstract As many as one third of solid tumors (ovarian, breast, pancreatic, prostate cancers) harbor deficiency in some DNA Damage Repair (DDR) pathways. Such cancers become dependent on alternative DDR pathways to maintain genome integrity, making them selectively vulnerable to DDR inhibitors. The concept of synthetic lethality has been successfully applied to develop strategies to treat subsets of such tumors. Clinically, PARP inhibitors (PARPi) have been successful particularly in Homologous Recombination Deficiency (HRD) cancers. Other agents have also been designed to target these DDR deficiencies in cancer cells and have potential to be clinically beneficial. LP-184 is a next generation acylfulvene prodrug metabolized to an active compound by prostaglandin reductase 1 (PTGR1) that is often elevated in multiple tumors. LP-184-induced DNA lesions are likely repaired by the Nucleotide Excision Repair (NER) and Homologous Repair (HR) pathways. Reduced activities of multiple DDR-related pathways in solid tumor models correlated with increased sensitivities to LP-184 as indicated by Gene Set Enrichment Analysis. Chinese Hamster Ovary cells with NER mutations (ERCC1/2/6) were at least 4 fold more sensitive to LP-184 relative to otherwise isogenic parental cells. ERCC2 or BRCA2 depletion enhanced LP-184 sensitivity 5-8X in a metastatic prostate cancer cell line. LP-184 showed ~120 fold higher potency (IC50 77 nM) compared to Olaparib in HRD prostate cancer organoid model LuCaP 96 (BRCA2/CHEK2 inactivating mutations). Across 14 patient-derived pancreatic, lung and prostate tumor models harboring HR mutations (BRCA1/2, CHEK1/2, ATM/ATR, PALB2, PARP1/2, RAD51, FANCA/B), LP-184 showed ex vivo IC50s in the range of 30-300 nM, whereas Olaparib IC50s ranged from 1700-6900 nM. LP-184 treatment resulted in complete tumor regression (107-141% TGI) in 10/10 HR deficient triple negative breast cancer PDX models of which 7/10 were resistant Olaparib/Niraparib and to Doxorubicin/Cyclophosphamide. LP-184 treatment resulted in complete and durable tumor regression in HRD (BRCA1/ATR mutant) pancreatic cancer PDX models (112-140% TGI). In the ovarian cancer cell line OVCAR3 having HRD/NERD phenotype, LP-184 IC50 was 13 nM, Olaparib IC50 was 145 nM and their combination Bliss Synergy Score was 16 indicating synergy. LP-184 is synthetic lethal resulting from its abilities to cause unresolvable DNA damage if tumor cells express high PTGR1 and are deficient in NER/HR genes. Unlike PARPi, LP-184 has striking activity in both NERD as well as HRD cancers. These strong data have prompted the development of a soon to be launched clinical trial to translate the broad preclinical anticancer activity of LP-184 in solid tumors with HR/NER pathway defects, such as pancreatic, prostate, ovarian and breast cancers. Citation Format: Aditya Kulkarni, Jianli Zhou, Neha Biyani, Kishor Bhatia, Panna Sharma. LP-184, an acylfulvene class small molecule therapeutic, is synthetically lethal in DNA damage repair deficient cancers. [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 6241.