Many diseases, such as diabetes, Alzheimer’s, Parkinson’s, hemophilia, and lysosomal storage diseases and cancer involve folding defects or impaired transport of proteins from the endoplasmic reticulum (ER). Cells activate the Unfolded Protein Response (UPR) to restore homeostatic protein processing by clearing out the stress of accumulated misfolded proteins (adaptive arm). However, with prolonged stress an apoptotic arm of the UPR leads to selective cell death. We herein report the successful development of a first-in-class, potent (762 nM EC50), not generally cytotoxic, chemical probe, ML291, that selectively activates the apoptotic but not the adaptive arm of the UPR, that demonstrates efficacy in inducing cell death through activation of the apoptotic arm in relevant cells, and moreover activate genes associated with the apoptotic arm of the UPR (by qRT-PCR). The progenitor of this probe was identified through a high-throughput screen of the NIH Molecular Libraries Small Molecule Repository (MLSMR) of >350,000 compounds through complementary cell-based reporter assays using stably transfected CHO-K1 cells that specifically identify activators of the PERK/eIF2a/CHOP (apoptotic), but not the IRE1/XBP1 (adaptive) UPR subpathways. The identification, validation, structure activity relationship (SAR) elucidation and development of this probe are described. The probe may serve as the basis for eventual proof-of-concept tool compound for activation of the apoptotic arm of UPR as a therapeutic modality in certain diseases.