Dihydrexidine
Dihydrexidine (DAR-0100) is a moderately selective full agonist at the dopamine D and D receptors. It has approximately 10-fold selectivity for D and D over the D receptor. Although dihydrexidine has some affinity for the D receptor, it has functionally selective (highly biased) D signaling, thereby explaining why it lacks D agonist behavioral qualities. Dihydrexidine has shown impressive antiparkinson effects in the MPTP-primate model, and has been investigated for the treatment of Parkinson's disease. In an early clinical trial the drug was given intravenously and led to profound hypotension so development was halted. The drug was  resurrected when it was shown that smaller subcutaneous doses were safe. This led to a pilot study in schizophrenia and current clinical trials to assess its efficacy in improving the cognitive and working memory deficits in schizophrenia and schizotypal disorder. There have been several reviews of relevance to the compound.