The chemoprotection of cells from apoptosis induced by toxins or ionizing radiation could be important for biodefense and in the treatment of acute injuries. We describe a series of small heterocycles, including fused benzothiazoles, benzimidazoles, and related compounds, that abrogate thymocyte apoptosis induced by dexamethasone and γ-irradiation. To optimize the protective activity of the previously reported pifithrin-α (PFT-α, 1), various derivatives and ...