Treatment of Parkinson's disease

1. A method of treating a subject having Parkinson's disease or at risk of Parkinson's disease comprising administering to the subject a regimen of Prasinezumab, wherein the treating comprises

(a) reducing Parkinson's disease progression as demonstrated by delaying time to progression of at least a 5-point progression in MDS-UPDRS Part III, or

(b) slowing decline in motor function comprising at least one of the following:

i. slowing decline the patient's MDS-UPDRS Part III motor examination score;

ii. slowing decline in one or more of speech, facial expression, rigidity, finger tapping, hand movements, pronation-supination movements of hands, toe tapping, leg agility, arising from chair, gait, freezing of gait, postural stability, posture, tremor of hands, rest tremor amplitude, constancy of rest tremor, or Hoehn and Yahr Stage;

iii. improving bradykinesia,

and wherein the regimen of Prasinezumab comprises 1000-5000 mg of Prasinezumab at intervals of 3 to 5 weeks.

2. The method of claim 1 , wherein the subject has been diagnosed as a mild motor-predominant subtype, a diffuse-malignant subtype or an intermediate subtype of Parkinson's.

3. The method of claim 2 , wherein the subject has been diagnosed as a diffuse-malignant subtype of Parkinson's.

4. The method of claim 1 , wherein the slowing decline of the patient's motor examination score comprises an improvement of at least 4%, 17%, 18%, 24%, 25%, 33%, 35%, 39%, 45%, 52%, 63%, 64%, 68%, 71%, 74%, 76%, or 109% compared to a placebo after one year of treatment.

5. The method of claim 1 , wherein the Prasinezumab is administered intravenously.

6. The method of claim 1 , further comprising administering to the subject a monoamine oxidase (“MAO”) inhibitor.

7. The method of claim 6 , wherein the MAO inhibitor is a MAO-B inhibitor.

8. The method of claim 1 , wherein the subject is treatment naïve, was diagnosed as having PD in the last two years, or was previously treated with a MAO-B inhibitor.

9. The method of claim 1 , wherein the subject has a weight greater than 65 kg and is administered a dose of 4500 mg Prasinezumab once every 4 weeks.

10. The method of claim 1 , wherein the subject has a weight less than 65 kg and is administered a dose of 3500 mg Prasinezumab once every 4 weeks.

11. The method of claim 1 , wherein the subject is administered a dose of 1500 mg antibody every 4 weeks.

12. The method of claim 1 , wherein the subject receives Prasinezumab once every 4 weeks for at least 52 weeks.

13. The method of claim 1 , wherein the subject is male.