A double-blind study, in which a range of 25–4,000 micrograms of GDNF was delivered via a catheter into the right ventricle of PD patients did not yield improvements on the Unified Parkinson’s Disease Rating Scale (UPDRS); in addition, several side effects were initially observed, but were subsequently resolved following the discontinuation of treatment [123]. The gene discussed is GDNF; the disease is Parkinson disease.