Abstract 2591: Synthetic optimization of polyisoprenylated cysteinyl amide inhibitors to target cancers with hyperactive G-proteins
Authors: Tawfeeq Nada , Jin Yonghao , Lamango Nazarius S. 
Published: September 2020

Cancers driven by mutant and/or overexpressed hyperactive G-proteins are resistant to current therapies. Finding effective therapies targeting such cancers remains an area of active research. Attempts at directly targeting the essential G-protein polyisoprenylation posttranslational modifications (PTMs) have met significant efficacy and toxicity challenges. The polyisoprenylated cysteinyl amide inhibitors (PCAIs) are a novel class of compounds designed around the Ras PTMs that have been shown to be very effective against various cancer biology phenomena. The design strategy incorporated the farnesyl tail, substituted amide bioisostere of the endogenous ester and a linker with a terminal ionizable group on the α-amino of the polyisoprenylated cysteine. This study is aimed at improving the potency and bioavailability of the PCAIs through synthetic optimization to mitigate the hydrophobicity of the pharmacophore. We report on newly synthesized PCAIs that are significantly less hydrophobic, their effectiveness in 2D and 3D cancer culture and the molecular mechanisms driving their anticancer effects. The new PCAIs were designed to have shorter linkers by coupling 4-methylpiperazine-1-yl aliphatic acids with L-S-trans,trans-farnesyl cysteine methyl ester to give the intermediate, 4-methylpiperazine-1-yl acyl-L-S-trans,trans-farnesyl cysteine methyl ester. The methyl esters of the intermediates were hydrolyzed with base and the resulting carboxylic acids coupled with cycloalkyl amines to afford the final products. The new PCAIs displayed Clog P values from 3.01 to 6.35. They suppressed the viabilities of MDA-MB-231, MIA PaCa-2 and NCI-H1299 cells that harbor mutant Ras with 48 h EC50 values from 2.2 to 6.8, 2.3 to 6.5 and 5.0 to 14 µM, respectively. The PCAIs with the free α-amino on the cysteine displayed a significant loss in potency with EC50 values ranging from 22 to over 50 µM for the different cell lines. Control analogs lacking the polyisoprenyl moiety had no effect at inhibiting the viabilities of the cells even at 50 µM. Treatment of MDA-MB-231 and NCI-H1299 3D spheroids with the most potent PCAIs suppressed their viabilities at 5 µM and 20 µM, respectively. Moreover, it was observed that ERK1/2 phosphorylation increased by 6, 33, and 121 % following treatment of NCI-H1299 cells for 24 h with 1, 2, and 5 µM of NSL-BA-055, respectively. However, after 48 h of treatment, 1 and 2 µM of NSL-BA-055 showed significant increase by 147 and 266 %, respectively, while the 5 µM showed a 20 % decrease of phospho-ERK1/2 relative to controls. The data reveal that (1) the more polar PCAIs maintained potency, (2) the three appendages on the cysteine of the PCAIs all contribute to potency and (3) the Ras-signaling axis is involved in the anticancer effects.

Citation Format: Nada Tawfeeq, Yonghao Jin, Nazarius S. Lamango. Synthetic optimization of polyisoprenylated cysteinyl amide inhibitors to target cancers with hyperactive G-proteins [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2591.