Effective therapies are needed for amyotrophic lateral sclerosis (ALS), a debilitating and fatal motor neuron disease. Cell and animal models of ALS are beginning to reveal possible principles governing the biology of motor neuron-selective vulnerability that implicate mitochondria and the mitochondrial permeability pore (mPTP). Proteins associated with the mPTP are known to be enriched in motor neurons and the genetic deletion of a major regulator of the mPTP has robust effects in ALS transgenic mice, delaying disease onset and extending survival. Thus, the mPTP is a rational, mechanism-based target for the development of drugs designed to treat ALS. Trophos SA has discovered olesoxime (TRO-19622), a small-molecule with a cholesterol-like structure, which has remarkable neuroprotective properties for motor neurons in cell culture and in rodents. Olesoxime appears to act on mitochondria, possibly at the mPTP. Phase I clinical trials of olesoxime have been completed successfully. Olesoxime is well tolerated and achieves levels predicted to be clinically effective when administered orally. It has been granted orphan drug status for the treatment of ALS in the US and for the treatment of spinal muscular atrophy in the EU. Phase II/III clinical trials are in progress in Europe.