Small molecule OPA1 inhibitors amplify cytochrome c release and reverse cancer cells resistance to Bcl-2 inhibitors.

The guanosine triphosphatase (GTPase) activity of the mitochondrial dynamin-related protein Optic Atrophy 1 (OPA1) regulates cristae remodeling, cytochrome c release, and apoptosis. Elevated OPA1 levels in multiple cancers correlate with reduced therapy sensitivity and poor survival, calling for specific OPA1 GTPase inhibitors. A high-throughput screening of ~10,000 compounds identified MYLS22, a heterocyclic N-pyrazole derivative as a reversible, noncompetitive OPA1 GTPase inhibitor. MYLS22 engaged with OPA1 in vitro and in cells where it induced cristae remodeling and mitochondrial fragmentation contingent on intactness of its predicted OPA1 binding site. MYLS22 enhanced proapoptotic cytochrome c release and sensitized breast adenocarcinoma cells to anti-Bcl-2 therapy, without toxicity on noncancer cells. By MYLS22 structure-activity relationship studies, we obtained Opa1 inhibitor 0 (Opitor-0) that inhibited OPA1, promoted cytochrome c release, and restored anti-Bcl-2 therapy sensitivity more efficiently than MYLS22. These chemical probes validate OPA1 as a therapeutic target to increase cancer cell apoptosis at the mitochondrial level.