These modifications result in a 20-fold improvement in the PK/pharmacodynamic relationship between oral exposure and in vitro efficacy in human tumor cell lines (FL5.12 Bcl-2 EC50 = 5.9 nM, FL5.12 Bcl-xL EC50 = 4.2 nM), leading to complete tumor regression in xenograft models (Park et al., 2008). The gene discussed is BCL2; the disease is neoplasm.