It has been recently reported that resistance to MCL-1 treatment in a metastatic model of breast cancer could be mediated by BCL-xL [49]; in fact, we validated this observation performing DBP with the HRK peptide (Figure 2A), as we observed a synergistic combination when sequentially combining S63845 and A-133 (Figure 2B). The gene discussed is MCL1; the disease is breast cancer.