Data from an extended Phase II study presented Tuesday at the Alzheimer's Association International Conference (AAIC) demonstrated that patients with Alzheimer's disease who took Baxter's intravenous immunoglobulin (IVIG) therapy Gammagard experienced stabilization of their symptoms for three years. Study leader Norman Relkin stated that "this is the first study to report long-term stabilization of Alzheimer's symptoms with IVIG," adding that "while the small number of participants may limit the reliability of our findings, we are very enthusiastic about the results."
Relkin presented the three-year data on the 16 patients with mild-to-moderate Alzheimer's disease who took part in the study, which originally enrolled 24 patients. Of the 16, five had been given placebo in the original trial, while 11 had been treated with various doses of IVIG. Results from the extended study showed that four patients who received the single standardized dose of 0.4g/kg of IVIG every two weeks for the full 36 months achieved the best outcome, with no decline on several standard measures of cognition, memory, daily functioning and mood.
The 11 participants who received IVIG for the full 36 months had favorable outcomes in terms of their thinking abilities, behavior and daily function, researchers said. Moreover, results demonstrated that the five who were initially treated with placebo and then switched to IVIG showed signs of cognitive decline while on placebo, but declined less rapidly while receiving a uniform dose of IVIG.
Relkin indicated that a Phase III trial is currently underway and "in less than one year, we'll have more definitive data on the efficacy of 18 months of IVIG treatment." Data from late-stage studies of Johnson & Johnson and Pfizer's bapineuzumab and Eli Lilly's solanezumab are expected within the next few months. Compared with bapineuzumab and solanezumab, which Relkin describes as "industrial-strength vacuum cleaners" used to remove beta amyloid from the brain, he says IVIG's natural antibodies are more like "gentle, whisk brooms…It may be that a gentler approach is a more realistic approach in the long run."
However, Harvard Medical School neurology professor Rudy Tanzi noted that it is important to be cautious about the results because of the small sample size and because patients and investigators knew the patients were getting the drug, which could have influenced the findings. "We have to wait for a proper phase III [trial] before we reach a conclusion," Tanzi added. Moreover, P. Murali Doraiswamy, an Alzheimer's researcher at Duke University who has served as an advisor to Baxter warned that "the findings are highly promising but nevertheless a double-edged sword due to the limited supply" of Gammagard, adding that "the growing off-label demand for Alzheimer's could threaten supply for immunodeficient patients."
Commenting on the news, RBC Capital Markets analyst Glenn Novarro speculated that an unequivocally positive result in the upcoming Gammagard study could generate a potential market worth $7.2 billion by 2017 in the U.S. alone.