HUMAN TESTS BEGIN ON PARKINSON'S DRUG.

Byline: Deborah Adamson Daily News Staff Writer

Amgen Inc. on Monday announced that it has begun its first human clinical trials for a drug that treats Parkinson's disease.

The product is the fifth new drug to start human clinical trials introduced this year by the Thousand Oaks-based biotechnology firm.

Thus far, Amgen only has two products in the market: Epogen, which treats anemia related to kidney disease; and Neupogen, an immune system stimulant. To ensure future growth, the company is developing a host of other drugs.

``You can't rest on your laurels in this business,'' said John Wong, senior biotechnology analyst at Van Kasper & Co., an investment banking firm in Brentwood. ``They need other breakthrough products.''

Called Glial Cell Line-Derived Neurotrophic Factor, or GDNF, the drug has been shown to reverse Parkinson's disease symptoms in preclinical trials.

In the first human clinical trial, where the drug will be tested on about 100 patients for 12 to 15 months, the product's safety will be assessed. The second trial will test the effectiveness of the drug and who benefits most from it. The third trial tests a much larger group of patients to confirm results.

It usually takes from five to 10 years for new products to reach the market, which includes getting regulatory approval, said Amgen spokesman David Kaye.

He said that there are 1 million people suffering from Parkinson's disease.

The illness is caused by the inactivity of neurons in the brain that contain dopamine. These neurons, which regulate body movement and coordination, eventually dysfunction and die. Parkinson's patients suffer from rigidity, tremors and difficulty in initiating movement.

GDNF protects these neurons from toxic damage and restores activity to damaged neurons. The drug is administered directly into the brain.

Amgen's four other new drugs that started human clinical trials this year are Leptin, which fights obesity; KGF, which treats the inflammation of the mucus membrane from chemotherapy and radiation; TNFBP, which treats rheumatoid arthritis; and a drug that cleanses the blood of cancer cells.