GDNF and Parkinson disease: However, in this double-blind trial of 41 randomized patients with moderate stage Parkinson’s disease, 40 weeks of fixed-dose GDNF intraputamenal infusions (120 μg GDNF in 600 μl artificial CSF to each putamen), administered every 4 weeks, did not produce a significantly larger percentage improvement than placebo in OFF state UPDRS motor score, the primary study outcome.