S55746 (S 055746,BCL201) is a novel, orally active BCL-2 specific inhibitor (Ki = 1.3 nM) with poor affinity for BCL-XL and no significant binding to MCL-1, BFL-1 (BCL2A1/A1). The selectivity of S55746 for BCL-2 versus BCL-XL ranges from ~70 to 400 folds.