BAY 63-9044

BAY 63-9044 is an investigational **small molecule** drug developed as a **full agonist of the 5-HT1A receptor** (serotonin 1A receptor), with additional *functional dopamine agonist properties*.[1][3] It was explored primarily for the treatment of **Parkinson's disease**, aiming to provide neuroprotection and delay progression of motor symptoms by activation of serotonergic and potentially dopaminergic pathways.[3] In preclinical models, BAY 63-9044 demonstrated neuroprotective effects and delayed onset of parkinsonian motor abnormalities.[3] A first-in-human clinical study showed it was safe and well-tolerated up to a maximum tolerated dose of 2.5 mg, with dose-limiting side effects at higher doses.[1][3]