UPDATE 1-Baxter Alzheimer's drug effective at 9 months-study

(Adds details of study, background, additional quotes from researchers)

By Susan Kelly

CHICAGO, July 30 (Reuters) - Alzheimer's disease patients treated with Baxter International Inc's (BAX.N) Gammagard for nine months maintained cognitive function and in some cases improved it, according to an interim analysis of data from a small study.

"If successful, it should actually alter the long-term course of the illness, and the effects should persist for a very long time," Dr. Norman Relkin, lead researcher for the study and a neuroscientist at New York-Presbyterian Hospital/Weill Cornell Medical Center, said in an interview on Wednesday.

Gammagard, an intravenous therapy of antibodies derived from human plasma that has been sold for other uses for 15 years, is intended to attack the disease in two ways.

The antibodies target beta amyloid proteins thought to disrupt brain function in Alzheimer's patients. Gammagard also contains anti-inflammatory properties that may activate microglia cells to help dissolve amyloid deposits, or plaques.

The 9-month data from the 24-patient phase 2 study were presented at the Alzheimer's Association conference in Chicago.

Six-month data from the study were released in April and deemed successful enough that the 8 patients who initially received a placebo were switched to Gammagard.

Patients treated with Gammagard for nine months showed significantly better cognitive and overall clinical outcomes than those who initially received a placebo, as measured by two commonly used disease assessment tests, the study found.