Sumanirole (PNU-95,666) is a highly selectiveD2 receptorfull agonist, the first of its kind to be discovered. It was developed for the treatment of Parkinson's disease and restless leg syndrome. While it has never been approved for medical use  it is a highly valuable tool compound for basic research to identify neurobiological mechanisms that are based on a dopamine D2-linked (vs. D1, D3, D4, and D5-linked) mechanism of action. 
^Romero AG, et al. Synthesis of the selective D2 receptor agonist PNU-95666E from D-phenylalanine using a sequential oxidative cyclization strategy. Journal of Organic Chemistry. 1997; 62(19):6582.
^McCall RB, Lookingland KJ, Bédard PJ, Huff RM (September 2005). "Sumanirole, a highly dopamine D2-selective receptor agonist: in vitro and in vivo pharmacological characterization and efficacy in animal models of Parkinson's disease". The Journal of Pharmacology and Experimental Therapeutics314 (3): 1248–56. doi:10.1124/jpet.105.084202. PMID15980060.
^Barone P, Lamb J, Ellis A, Clarke Z (March 2007). "Sumanirole versus placebo or ropinirole for the adjunctive treatment of patients with advanced Parkinson's disease". Movement Disorders : Official Journal of the Movement Disorder Society22 (4): 483–9. doi:10.1002/mds.21191. PMID17115380.
^Garcia-Borreguero D, Winkelman J, Adams A, Ellis A, Morris M, Lamb J, Layton G, Versavel M (March 2007). "Efficacy and tolerability of sumanirole in restless legs syndrome: a phase II, randomized, double-blind, placebo-controlled, dose-response study". Sleep Medicine8 (2): 119–27. doi:10.1016/j.sleep.2006.05.018. PMID17239657.