Safety and Efficacy of CERE-120 in Subjects With Parkinson's Disease

Approximately sixty patients with Parkinson's disease will participate in this study. The
first part of the study (Phase 1) is now complete. Six people with Parkinson's disease
received CERE-120 in Phase 1 without complications.

The second part of the study (Phase 2) will provide more information about the safety of
CERE-120 and also evaluate if it is beneficial in the treatment of Parkinson's disease. In
Phase 2, approximately 52 people with Parkinson's disease will be enrolled. Half of the
subjects will receive CERE-120 and the other half will undergo a "placebo" surgery where no
medication will be injected. Treatment assignment will be random (like the flip of a coin).
Participants in both phases of the study will be followed for three years after surgery.

In this study, CERE-120 will be injected by a neurosurgeon directly in the substantia nigra
(where dopamine producing cells are located) and in the putamen (where the dopamine cells
project).

CERE-120 has been carefully studied in laboratory animals without any toxicity despite very
high doses. In addition, in animals with symptoms similar to Parkinson's disease, CERE-120
was shown to protect brain cells and restore their function.

CERE-120 has been previously studied in 50 people with Parkinson's enrolled in two clinical
studies. These patients have been followed for over 2 years (some for almost 5 years) and so
far CERE-120 has been well tolerated. Whereas CERE-120 was not better than placebo on the
primary efficacy measure in a completed study, several measures of improvement suggested a
modest benefit. In order to build upon these findings and increase the chances for a
stronger clinical benefit, a dose increase and modifications in the delivery targets have
been implemented in the current study.