Pyrrolo(1,2-a)pyrazine-1,4-dione, hexahydro-8a-(2-propenyl)-, (8aR)-
NNZ-2591 (cyclo-L-glycyl-L-2-allylproline) is an investigational synthetic analog of cyclic glycine-proline (cGP), a breakdown product of human insulin-like growth factor 1 (IGF-1), that has been chemically modified to increase its half-life, stability, and oral bioavailability. It is currently under development by Neuren Pharmaceuticals for the symptomatic treatment of Angelman, Phelan-McDermid, and Pitt Hopkins Syndromes. It was granted Orphan Drug Designation by the FDA in October 2019 and was granted a patent by the European Patent Office in December 2019. Clinical trials are expected to begin in 2020.