Baxter, a Drug Maker, Says Its New Alzheimer's Treatment Has Failed In yet another setback for the treatment of Alzheimer's disease, Baxter International said Tuesday that a promising new therapy had failed to halt the mental decline caused by the disease in a late-stage clinical trial. Prospects that the drug might have some effect brightened last year when researchers reported that four patients who had received the maximum dose had gone three years without any decline in several measures of cognition and daily functioning, which they termed highly unusual. But as is often the case, anecdotal evidence failed to hold up when the treatment was subject to a large, randomized trial against a placebo. Baxter said on Tuesday that the immunoglobulin therapy did not significantly arrest the decline in either cognition or daily functioning when compared with a placebo. The trial involved 390 patients with mild to moderate disease who were treated for 18 months. The company said it would discontinue other trials testing the drug as a treatment for Alzheimer's. "We are currently re-evaluating our approach," Ludwig Hantson, president of Baxter's bioscience business, said in a conference call with analysts Tuesday. Still, Dr. Hantson said the company was not giving up entirely. He said there were some hints that the higher of two doses tested might have had some impact in patients with moderate disease, as opposed to mild disease, and also in patients with a gene variant called ApoE4 that raises the risk of Alzheimer's. Dr. Hantson said the company wanted to evaluate data it did not yet have, looking at biomarkers of disease, like brain atrophy measured by M.R.I. scans and the levels of telltale amyloid proteins in the blood and spinal fluid. Depending on the results of the analyses, the company might decide to undertake new trials in certain subsets of patients, he said. Baxter's shares were down 3 percent at the start of trading Tuesday. Baxter's announcement follows the Phase 3 failures of two other Alzheimer's drugs last year, bapineuzumab developed by Pfizer and Johnson & Johnson and solanezumab from Eli Lilly & Company. Lilly is continuing to test its drug, which it said might help patients with mild disease as opposed to moderate disease, the opposite of what Baxter says about its treatment. The drugs that failed last year both aimed at beta amyloid, a protein with toxic effects found in the brain of people with Alzheimer's disease. It is not known how Baxter's treatment works, if it works at all. Immunoglobulin, also known as intravenous immune globulin, or IVIG, is made from human plasma collected from healthy volunteers. It contains a variety of antibodies. Since immune globulin is already on the market for other diseases, Baxter sells its product as Gammagard, and some doctors are already using it off-label to treat Alzheimer's. Baxter executives said they thought such off-label use was limited because of the high cost of the treatment, which is thousands of dollars a month. The treatment requires intravenous infusions every two weeks. Even if Baxter's drug had worked in the clinical trial, there were doubts about whether it could have been a practical treatment because of the challenges involved in collecting enough human plasma. It is estimated that immune globulin is now used by tens of thousands of people with rare immunological and neurological diseases. By contrast there are several million people with Alzheimer's in the United States, and the number is expected to grow as the population ages.