S44563

S44563 is a **potent small molecule** inhibitor targeting the anti-apoptotic proteins **Bcl-2** and **Bcl-XL**, with IC50 values of 131 nM and 140 nM, respectively. It induces mitochondrial-mediated apoptosis by activating caspase-9 and caspase-3 and facilitating cytochrome c release from mitochondria. S44563 demonstrates antitumor activity in preclinical xenograft models of melanoma, uveal melanoma, and small-cell lung cancer, either alone or in combination with chemotherapy (such as fotemustine or cisplatin) and radiotherapy, enhancing both chemosensitivity and radiosensitivity. It is developed exclusively for research purposes and has not been used in human clinical trials.