SU-5416, a VEGF-receptor tyrosine kinase inhibitor and Thalidomide demonstrate anti-angiogenic activity in different model systems. Two series of compounds, 1,3-dihydro-indole-2-one analogs based on SU-5416 and iso-indole-1,3-dione based on Thalidomide were evaluated for their anti-cancer activity.
SU5416, a potent ATP competitive, VEGF receptor tyrosine kinase inhibitor was used as a template for the design of the first series. A series of 1,3-dihydro-indole-2-one compounds were evaluated for anti-proliferative activities on cancer cells. The most potent analog was compound 145E with a tri-methoxy benzylidene substituted on position 3 of 6-methoxy-1,3-dihydro-indole-2-one. It caused a G2/M phase arrest in the cell cycle. It inhibited the polymerization of tubulin to polymeric microtubule and induced apoptosis following twenty-four hour incubation demonstrated by three different assays. Structurally, analog 145E resembles colchicine site agents. Additional SAR was conducted to evaluate the effect of the number of methoxy groups on the benzylidene ring; position of the methoxy groups; nature of substituents on position 6 of the core ring. Two structural features, namely the 6-OCH3 group in the indolinone ring and the trimethoxy group in the benzylidene ring, are essential for potent cytotoxicity and inhibition of tubulin polymerization.
The next series of compounds were derived from Thalidomide. In an search for potent thalidomide analogs, anti-angiogenic analog 5-hydroxy-(2,6-diisopropylphenyl)-1H-isoindole-1,3-dione 5HPP-33 was identified. In addition to its anti-angiogenic activity, 5HPP-33 demonstrated potent anti-proliferative activity (low micromolar range) in vitro against nine tumor cell lines. Flow cytometric analyses reveal that 5HPP-33 induced cell cycle arrest in G2/M phase in tumor cells. Cells treated with compound 5HPP-33 exhibit a breakdown of nucleus into micronuclei. 5HPP-33 enhances tubulin polymerization in vitro tubulin polymerization assay and the polymers thus formed are resistant to cold. It demonstrated inhibition of NFκΒ activation and stabilized the degradation of inhibitory protein IκΒ Following the mechanistic study of 5HPP-33, a series of structural analogs were evaluated for their cytotoxicity in tumor cells. The analogs included modifications on the rings A and C of 5HPP-33. Two structural features, namely the 5-substitution on ring A and 2, 6-diiso-propyl group in the ring C, are essential for potent cytotoxicity and induction of tubulin polymerization.