IV Ig Stalls Alzheimer Disease in 4 Patients
IV immunoglobulin (specifically Baxter’s Gammagard) may halt the progression of Alzheimer’s disease, according to a very small extension study of the twice-weekly drug. Phase 2 results, presented at the ongoing AAIC in Vancouver, indicated that 4 patients who received the standard dosage (0.4 mg/kg) every 2 weeks for the full 3 years of the extension study demonstrated no decline in accepted clinical measures of cognition, daily or global functioning, behavior, or quality of life. That’s a remarkable finding, even with the limited subject number, in a disease that is known to progress inexorably. Unless the diagnosis of AD was made in error in these 4 patients, or there was some confounding variable in their assessment (like the influence of unblinded treatment), it seems that these results should be valid and potentially reproducible on a larger scale.
Also according to the AAIC press release: Among the 16 of 24 patients who elected to participate in the phase 2 extension study of IV Ig, 11 patients who received the treatment for 3 years (with 7 of these patients presumably receiving a dosage below 0.4 mg/kg) “had favorable outcomes in terms of their thinking abilities, behavior and daily function.” Among the 5 participants who initially received placebo treatment, switching to IV Ig in the extension phase was associated with a less rapid decline in AD-related symptoms. The drug, however, was not without its safety issues, according to coverage by MedPage Today. At least one patient experienced a stroke, possibly as a result of increased blood viscosity associated with IV Ig therapy.
Notably there are at least 2 phase 3 studies evaluating Baxter’s Gammagard in mild-moderate AD, one of which is actively recruiting subjects. Results of an ongoing 18-month trial (N = 390) are expected in February of next year. One thing that would be very interesting, if not crucial, to know is whether the stabilization of clinical AD with IV Ig (if it is confirmed) is associated with the removal of brain amyloid. Unfortunately it is not stipulated in the phase 3 trial description that subjects are undergoing PET imaging for amyloid.
Gammagard is FDA approved for a number of immune-mediated or immunodeficiency diseases, and it is used off label for several neurologic conditions, including inflammatory neuropathies. Consequently the uptake of IV Ig by neurologists for the treatment of AD, if it is determined to be reliably effective, will be relatively swift. Lead investigator of the phase 2 study, Norman Relkin, cautioned against the current use of IV Ig for AD, given that supplies of the blood-derived product are limited, and that the lives of some patients with FDA-approved indications are dependent on available treatment. “[W]e don’t want to bankrupt the available
supplies,” he advised MedPage Today.
AAIC = Alzheimer’s Association International Conference; IV Ig = intravenous immunoglobulin.