BCL2L1 and cancer: The first biologically relevant HBS-constrained peptide was reported by Wang et al. B-cell lymphoma-extra-large (Bcl-xL) is an antiapoptotic protein that regulates cell death by binding the α-helical BH3 domain of a family of proapoptotic proteins (including Bak, Bad, Bid, and Bax), with this PPI being severely impaired in a multitude of cancers.