Human trials of Elan's vaccine therapy against Alzheimer's disease remain suspended, pending investigations related to safety concerns. Administration of the drug was temporarily halted last month after four French patients receiving the vaccine became ill.
Elan and American Home Products are partners in the trials, which are under way in the US and four European countries. The trials followed very promising preliminary results from the vaccine, AN-1792, which reverses the build-up in brain tissues of a substance called plaque. The plaque build-up is a feature always seen in patients with Alzheimer's, a progressive brain disease that leads to memory loss, dementia and death.
At the time administration of AN-1792 was suspended, about 360 patients with mild to moderate Alzheimer's disease had received multiple doses of the vaccine, including 97 in France. Dosage was stopped when four French patients developed clinical signs typical of inflammation of the central nervous system. All four had received AN-1792, but the companies reported no clinical signs in the other trial locations.
A successful treatment would be of huge financial benefit to the two companies, as there are no treatments on the market able to remove the plaques associated with Alzheimer's. An estimated 22 million people are expected to develop the disease worldwide by 2025.
The companies stressed that while dosage had stopped, the study was "still ongoing". The phase 2A trials were meant to assess how the patients' immune systems responded to immunisation against plaque, and this data could still be collected. Initial safety trials had already been passed.
The inflammation seen was similar to that caused by viral infection, but the exact cause of the symptoms had yet to be determined. The companies were still investigating the cause of the inflammation, according to a company statement issued this week. These results would then have to be cleared by the independent drug safety board controlling each of the trials and reviewed by the regulatory authorities in the US and Europe before dosage could resume.
The phase 2A trials, if successful, would open up further trials involving more patients.
