Sir

One potential route for therapy for Alzheimer's disease involves the immunization of patients against the amyloid-β peptide, the major proteinaceous component that characterizes plaques in the brains of patients with this disease. Resulting from earlier research on mice, published in Nature1,2,3, Elan Pharmaceuticals recently began clinical trials of a vaccine, AN-1792, based on this approach. In January, four patients in this trial developed inflammation of the central nervous system, and Elan suspended the trial pending further investigation4. By March, the number of patients in this trial who had symptoms resembling encephalitis and meningitis was reported to have increased to 15, and Elan has permanently withdrawn the AN-1792 vaccine from human trials5.

It is not clear precisely what caused the inflammation in these patients, as Elan has released few details of their medical condition. Elan is under no obligation to report the results of the AN-1792 trials, and may well not wish to lose its perceived scientific or commercial advantage.

Nonetheless, detailed information of the conditions developed by these patients is of profound interest to the scientific community as well as society at large. We therefore urge Elan to publish details from their study as quickly as possible, so that any foreseeable side-effects can be avoided in future trials.