BH3 mimetics: status of the field and new developments.

Targeting apoptosis is an attractive approach in cancer therapy. The BH3-only proteins of the BCL-2 family (having only the BCL-2 homology domain BH3) can trigger apoptosis by binding to the prosurvival members of this family and neutralizing their functional activity (sequestration of the proapoptotic Bcl-2 family members). The "BH3 mimetic" concept has prompted the development of small molecules capable of mimicking BH3-only proteins and thus inducing apoptosis. The prototype BH3 mimetic ABT-737 selectively targets the three prosurvival proteins BCL-XL, BCL-2, and BCL-W (but not MCL-1 or A1) and its oral derivative ABT-263 has proved promising in clinical trials. Some putative BH3 mimetics are also tested clinically while others are still being characterized. This article recapitulates the various known BH3 mimetics and presents the recent developments in the field. The latter include (i) the identification of molecular determinants responsible for the specific interactions between BH3 motifs and the binding grooves of prosurvival proteins and (ii) the characterization of new compounds and particularly BH3 mimetics that antagonize either selectively MCL-1 or BCL-2 or a broad range of prosurvival proteins. These data are critical advances toward the discovery of novel anticancer agents.