PPARD
PPARD peroxisome proliferator-activated receptor delta — the molecular target that 1 compounds in the wiki act on.
In one line: An "endurance" switch that tells muscles to burn fat and last longer.
PPARD (PPAR-delta) is a switch that shifts muscle toward burning fat for fuel and boosts endurance — essentially mimicking some effects of exercise. The compound cardarine (GW-501516) activates it, and in animals it dramatically increased running endurance.
The serious catch, and the reason it was abandoned: in animal studies it caused cancer in multiple organs at multiple doses. Impressive endurance effect, unacceptable safety signal.