Antiangiogenic activity of N-substituted and tetrafluorinated thalidomide analogues.

Inhibition of angiogenesis is currently perceived as one of the promising strategies in the treatment of cancer. The antiangiogenic property of thalidomide has inspired a second wave of research on this teratogenic drug. Previous studies from our group and others demonstrated that metabolites of thalidomide are responsible for the drug's pharmacological actions. On the basis of the structures of these metabolites, we synthesized 118 thalidomide analogues. Preliminary screening selected 7 of these 118 analogues for more extensive testing in the current study. In the rat aortic ring assay, all 4 analogues in the N-substituted class and 2 of the 3 analogues in the tetrafluorinated class significantly inhibited microvessel outgrowth at 12.5-200 microM. Thalidomide failed to block angiogenesis at similar concentrations. Subsequently, the effects of these analogues on human umbilical vein endothelial cell proliferation and tube formation were determined. Those analogues showing antiangiogenicity in the rat aortic ring assay also demonstrated antiproliferative action in human umbilical vein endothelial cells. Cell proliferation was not affected by thalidomide. Interestingly, all 7 analogues as well as thalidomide suppressed tube formation. Two tetrafluorinated analogues consistently showed the highest potency and efficacy in all three assays. The in vivo toxicity of representative analogues from each class was also evaluated. Taken together, our results support the further development and evaluation of novel thalidomide analogues as antiangiogenic agents.

Comparative molecular field analysis and comparative molecular similarity indices analysis of thalidomide analogues as angiogenesis inhibitors.

Thalidomide, 2-(2,6-dioxo-3-piperidinyl)-1H-isoindole-1,3(2H)-dione, has been shown to inhibit angiogenesis, the formation of new blood vessels from existing vasculature. As a result, there is renewed interest in this drug as a potential therapy for solid tumors. Thalidomide forms a number of metabolites and has been shown to require metabolic activation for antiangiogenic activity. A series of 39 compounds, based upon the structure of some of these metabolites, was synthesized and tested for their ability to inhibit microvessel growth in the rat aortic ring assay. The results of this testing have been used as the basis for a three-dimensional quantitative structure-activity relationship (3D-QSAR) study, utilizing comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) procedures. The best resulting CoMFA and CoMSIA models have conventional r(2) values of 0.924 and 0.996, respectively. The cross-validated q(2) values are 0.666 and 0.635, respectively. These models offer insight into the structural requirements for activity of thalidomide analogues as angiogenesis inhibitors, since there is only speculative knowledge of the target. Additionally, it appears as though there is more than one active site or mechanism of action.

The aminobarbituric acid-hydantoin rearrangement.

A general synthesis protocol for the generation of tri- and tetrasubstituted 5-carbamoylhydantoins is described. Starting from barbituric acids and following bromination and reaction with primary amines, 5-aminobarbituric acids 3a-s and 8 were prepared. Compounds 3 and 8 were subjected to different conditions of a base-catalyzed rearrangement reaction to yield the 1,5,5-trisubstituted hydantoins 4a-s and the 1,3,5,5-tetrasubstituted hydantoin 5c, respectively. Alkylation of 4a-s afforded 1,3,5,5-tetrasubstituted hydantoins 5a-h. Mechanisms that explain the transformation of corresponding aminobarbituric acids to hydantoins 4a-s and 5c were discussed in terms of the formation of ring-opened intermediates. Aminobarbituric acids 3a-s unsubstituted at position 3 underwent a ring contraction via intermediate isocyanates which were trapped by the amino function. A different mechanism involving a carbamate intermediate was concluded for conversion of the 1,3,5,5-tetrasubstituted aminobarbituric acid 8.