Development of Styryl-Modified 3,4-Dihydropyrimidin-2(1H)-ones as Potential Antitumor Agents.

Monastrol, a DHPM-based Eg5 inhibitor with well-known antiproliferative activity but limited therapeutic potential due to poor solubility and low bioavailability, was selected as the lead compound for the design of styryl-modified 3,4-dihydropyrimidin-2(1H)-ones with an improved pharmaceutical profile. Twelve derivatives (10-21) were synthesized via the Biginelli reaction and evaluated for cytotoxicity in HeLa and MCF-7 cells. Styryl derivatives 16 and 17 emerged as the most active. In HeLa cells, derivatives 17 (IC50 = 1.3 µM) and 16 (IC50 = 3.7 µM) were approximately 85-fold and 30-fold more potent than monastrol (IC50 = 111 µM), respectively. In MCF-7 cells, derivatives 16 and 17 displayed 18- to 20-fold higher potency than monastrol, respectively. Biological results also indicate that styryl derivatives 16 and 17 induce apoptosis in both HeLa and MCF-7 cells. In HeLa cells, activation of caspase-8, -9, and -3 suggests the involvement of both intrinsic and extrinsic pathways. In contrast, in MCF-7 cells, the increased expression of p53 and p21, together with PARP cleavage, suggests a p53-dependent apoptotic response. Derivatives 16 and 17 emerged as promising Eg5 inhibitors from docking studies, but their poor aqueous solubility (0.2-0.7 µM), despite high biological stability, highlights the need for formulation strategies to improve drug-like properties.