Targeting Acetyl-CoA carboxylase in pre-clinical breast cancer models

Abstract Background: Cancer cells and normal cells of the same lineage differ in their metabolism. We previously described large scale shifts in isoenzyme distribution between matching cancer and normal tissues and identified Acetyl-coA carboxylase (ACC1/ACACA) as a cancer dominant enzyme that is overexpressed in multiple cancer types. ACC1 catalyzes the initial rate-limiting step in de novo fatty acid synthesis, the conversion of acetyl-CoA to malonyl-CoA. Gene knock-out experiments demonstrated that this enzyme is essential for cancer growth. In this study, we evaluated the in vitro and in vivo efficacy of a small molecule ACC inhibitor, PF05175157 as a potential anticancer drug. This drug has been tested in clinical trials for diabetes, but development was discontinued due to grade 2 thrombocytopenia.Methods: We performed in vitro cytotoxicity assays in 15 breast cancer cell lines and in normal mammary epithelial HMEC cells, examined effect on apoptosis and cell cycle progression, and tested for synergy with alpelisib, docetaxel, doxorubicin, everolimus, iniparib, neratinib and TEPP46 (PKM2 and PKLR activator). We next assessed in vivo single agent activity in a triple negative patient derived (PDX) model (J000102184) in NSGTM mice and in MDAMB468 xenografts implanted into Rag2/IL2RG double knockout mice. We performed RNA sequencing and metabolomic profiling of cells treated with PF05175157 to study metabolic and transcriptomic effects of the drug. Results: PF05175157 induced time and dose dependent growth inhibition in all but 1 of the 15 cancer cell lines. The estimated EC50 after 72h exposure ranged from 0.95 to 76 μg/mL in T47D and BT549 cells, respectively (Cmax of 20 μg/mL can be achieved in human serum). There was no significant inhibitory effect on HMEC cells. In cancer cell lines, the % of apoptotic cells increased from 4% to 8% in BT474 and from 7.7% to 17.8% in MDMBA468 cells upon treatment with the compound, and there was a trend towards G2/M cell cycle arrest in both cell lines after 72 hours of exposure (10μg/mL). In drug combination experiments, PF05175157 added to iniparib, or to the PKM2 activator, TEPP46, decreased cell viability compared to single agent therapies in several cell lines. PF05175157 significantly delayed tumor growth compared to vehicle, when administered orally (20mg/kg gavage BID) in a TNBC PDX model (median tumor volume after 33 days: 334.1 mm3 in PF05175157-treated vs. 490.5 mm3 in methylcellulose-treated mice; p=3.39e-7) and intraperitoneally (20 mg/kg in DMSO) in an MDAMB468 xenograft model (median tumor volume after 40 days: 244.5 mm3 in PF05175157-treated vs. 303.3 mm3 in DMSO-treated mice; p<0.05). Transcriptomic and metabolic profiling of MDAMB468 and BT474 cells treated with 10 ug/ml PF05175157 for 6 and 24 hours revealed activation of immune signaling, epigenetic regulation and DNA damage repair pathways along with down-regulation of a broad range of metabolic pathways. Conclusions: The small molecule ACC inhibitor, PF05175157, has significant single agent in vitro and in vivo growth inhibitory effect on a range of breast cancer cell lines at concentrations that can be achieved in human serum. It showed synergy with iniparib and another metabolic inhibitor (TEPP46). Targeting de novo fatty acid synthesis by inhibiting ACC is a promising therapeutic strategy. Citation Format: Julia Foldi, Michal Marczyk, Vignesh Gunasekharan, Tao Qing, Raghav Sehgal, Naing Lin Shan, Viswanathan Muthusamy, Sheila Umlau, Yulia V. Surovtseva, Richard Kibbey, Lajos Pusztai. Targeting Acetyl-CoA carboxylase in pre-clinical breast cancer models [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-17-01.