Sabcomeline
Sabcomeline is a selective M1 receptor partial agonist that was under development for the treatment of Alzheimer's disease. It made it to phase III clinical trials before being discontinued due to poor results.
It is a non-selective agonist of all five muscarinic acetylcholine receptors with similar affinities. However, functional selectivity for the M1 receptor has been claimed in vitro and in vivo.