1,3,4-Thiadiazolo (3,2-Α) Pyrimidine-6-Carbonitrile Scaffold as PARP1 Inhibitors.

Background 1,3,4-thiadiazolo pyrimidine is a lead molecule which is versatile for a wide variety of biological activities and in continuation of our interest in establishing some novel heterocyclic compounds for antitumor activity. Objective The objective of the study was to synthesize series of 5-amino-7-(substituted aldehyde)-2[(naphthalene-2-yloxy)methyl] - [1,3,4]thiadiazolo-[3,2-α]-pyrimidine-6- carbonitrile derivative and evaluated for their possible in vitro and in vivo anticancer activity. Methods Herein we report the synthetic scheme which was followed for the preparation of a series of title compounds B1- B9 is outlined in the scheme 1. The intermediate 5-[(naphthalen-2- yloxy)methyl]-1,3,4-thiadiazolo-2-amine was prepared by heating 2-naphthoxyacetic acid and thiosemicarbazide in presence of phosphoryl chloride at a temperature of 65 - 750C. The obtained compound reacted with malononitrile and appropriate amount of aromatic and heteroaromatic aldehydes in refluxing ethanol yielded 5-amino-7-(substituted aldehyde)-2[(naphthalene-2-yloxy)methyl] -[1,3,4]thiadiazolo-[3,2-α]-pyrimidine-6- carbonitrile derivatives (B1 - B9). The purity of synthesized compounds ensured by various spectral analysis. Results In in-silico molecular docking studies compounds B3 and B9 show binding affinity like known PARP1 inhibitor olaparib. The cellular evaluation indicates that the anticancer activity of compounds B1, B3, B9 is significant when compared to standard drug (olaparib) against MDA-MB-232 cell line and compounds B3, B6, B7 are most active against MCF-7 cell lines. The most active compound B3 was subjected to acute oral toxicity studies by OECD 423 guidelines and in-vivo anti-cancer studies were carried out using DMBA induced model. Conclusion The in-silico docking study of the newly synthesized compounds were performed, the results showed good binding mode in the active site of PARP1 enzyme. In-silico ADME properties of synthesized compounds were also studied and showed good drug like properties.