Abstract 550: p53 rescue of tumor suppressor function with ADGN-531 causes tumor regression both as single agent and in combination with PARPi and KRASG12Cinhibitors
Authors: Divita Gilles , Grunenberger Audrey , Czuba Elodie , Boularache Khadidja , Guidetti Melanie , Josserand Veronique , Desai Neil 
Published: April 2023

The p53 tumor suppressor mutations resulting in loss of function control tumor proliferation in 50% of human cancers. TP53 missense and nonsense mutations are present in about 50% and 7-12% of the p53 driven cancer, respectively. To date there is no effective treatment for rescuing p53 function in cancers harboring p53 nonsense mutations. We have developed a new potent strategy combining mRNA with a tumor selective nanocarrier, to rescue of p53 tumor suppressor functions as potential therapeutic approach in cancers. ADGN-531 contains proprietary p53-mRNA complexed with proprietary short amphipathic peptides that form stable neutral nanoparticles. ADGN-531 was evaluated on 20 different cancer cell lines harboring different types of p53 mutations. In-vivo efficacy of IV-administered ADGN-531 nanoparticles (weekly, 0.5 & 1.0mg/kg) was evaluated on colorectal SW403 (p53 nonsense/KRASG12V), osteosarcoma SaOs2 (p53 null) and lung H358 (p53 null/KRASG12C) mouse xenografts. Sensitivity to Veliparib (PARPi) following ADGN-531 treatment was evaluated on PARPi resistant SUM-149PT and OVCAR-8 and PARPi sensitive MDA-MB436 cells. ADGN-531/AMG-510 synergy was evaluated on H358 and M-PACA cells and H358 mouse xenograft. ADGN-531 markedly delay the growth of a large panel of cancer cells harboring p53-missense or nonsense mutations, by rescuing p53 transcriptional activity and subsequent expression of its target proteins. ADGN-531 induces cell cycle arrest in G1 due to p21 upregulation and apoptosis following BAX and PUMA activation. ADGN-531 mediated p53 function rescue is directly correlated to the type of p53 mutation in the cancer cells. ADGN-531 induces 80% cell proliferation inhibition in p53 null/nonsense cells and 20 to 50% in p53 missense cells. IV-administration of ADGN-531 resulted in dose responsive tumor growth inhibition. ADGN-531 (1.0mg/kg) induces 40-60% tumor regression SaOs2, SW403 and H358 xenografted mouse model. We demonstrated a synergistic combination between ADGN-531/AMG-510 a KRASG12C inhibitor in human lung carcinoma. ADGN-531 (0.5mg/kg, weekly)/AMG-510 (10mg/kg, daily) induces about 80% tumor regression, higher than with either single agents. We demonstrated that ADGN-531 mediated p53 rescue markedly improves (200 fold) and restores the sensitivity of ovarian and breast cancer cells to Veliparib. ADGN-531 treatments are well tolerated, no sign of clinical toxicity or inflammatory response was detected after single or repeated administrations. ADGN-531 is effective in rescuing P53 functions both in vitro and in vivo. Our study provides a proof-of-concept that restoration of tumor suppressor function by ADGN-531 could be used as a single agent therapy or in combination together with other therapies for potent combinatorial cancer treatment.

Citation Format: Gilles Divita, Audrey Grunenberger, Elodie Czuba, Khadidja Boularache, Melanie Guidetti, Veronique Josserand, Neil Desai. p53 rescue of tumor suppressor function with ADGN-531 causes tumor regression both as single agent and in combination with PARPi and KRASG12Cinhibitors [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 550.