This randomized, placebo- controlled, 5- week Phase II trial evaluated the safety and tolerability of SIB- 1508Y, a selective α 4β 2 nicotinic acetylcholine receptor agonist, in 77 individuals with early Parkinson disease. Lightheadedness was a common dosage- related adverse effect at higher dosages, leading to frequent dosage reduction, drug discontinuation, and eventual trial redesign. A maximally tolerated dosage of 10 mg daily was identified. No antiparkinsonian or cognitive- enhancing effects were demonstrated in this trial. This randomized, placebo-controlled, 5-week Phase II trial evaluated the safety and tolerability of SIB-1508Y, a selective α 4β 2 nicotinic acetylcholine receptor agonist, in 77 individuals with early Parkinson disease. Lightheadedness was a common dosage-related adverse effect at higher dosages, leading to frequent dosage reduction, drug discontinuation, and eventual trial redesign. A maximally tolerated dosage of 10 mg daily was identified. No antiparkinsonian or cognitive- enhancing effects were demonstrated in this trial.