The Gammaglobulin Alzheimer’s Partnership (GAP) study was conducted by Baxter in collaboration with the Alzheimer’s Disease Cooperative Study (ADCS), a clinical trial consortium supported by the United States National Institute on Aging in the National Institutes of Health.
Topline analyses from the randomized, double-blind, placebo-controlled, multi-center trial found that after 18 months of treatment, patients with mild to moderate Alzheimer's disease taking Baxter's IG treatment at either the 400 mg/kg or the 200 mg/kg dose did not demonstrate a statistically significant difference in the rate of cognitive decline as compared to placebo (mean 7.4 in the 400 mg/kg group, 8.9 in the 200 mg/kg group, and 8.4 in the placebo group). Results also did not indicate a statistically significant change in functional ability as compared to placebo (mean -11.4 in the 400 mg/kg group, -12.4 in the 200 mg/kg group, and -11.4 in the placebo group).
While the study was not powered to show statistical significance among the sub-groups, in the pre-specified sub-group analysis, the 400mg/kg treatment arm showed a positive, numerical difference in change from baseline versus placebo in cognition as measured by the Alzheimer’s Disease Assessment Scale – Cognitive Subscale (ADAS-Cog) and Modified Mini-Mental State (3MS) Examination among both moderate patients and carriers of the ApoE4 genetic marker. These differences ranged between 16 percent and 29 percent. [A data table is available at: www.baxter.com/gap/baxter_gap_study_data_table.pdf].
''The study missed its primary endpoints, however we remain interested by the pre-specified sub-group analyses, particularly among patients with moderate disease and those who carry a genetic risk factor for Alzheimer’s disease, two patient groups that are in great need of advances in care. A detailed analysis of the results from the GAP study continues, and we look forward to a greater understanding of the full data set,'' said Ludwig Hantson, Ph.D., president of Baxter’s BioScience business. ''We are grateful for the participation of the patients and physicians in the study and for the dedicated support of the patients’ caregivers.''
IG was well tolerated in the study and no new safety signals were identified associated with treatment in this patient population, ages 50-89. The most common adverse reactions (observed in at least 5 percent of patients) during treatment with IG were rash and decreases in hemoglobin. There were no differences in the rate of thromboembolic events in the treated groups versus placebo groups. There were 17 serious adverse reactions considered to be treatment-related in the study (12 in the IG cohorts and five in the placebo cohort).
Based on these results, Baxter will reconsider its current approach for its Alzheimer’s program and will determine next steps after full data analyses. The current Baxter studies of IG in mild to moderate Alzheimer’s disease will be discontinued. Additional analyses from the study, including imaging, will be made available later this year as part of a full presentation of the GAP study at the Alzheimer’s Association International Conference, July 13-18, 2013 in Boston.
The Alzheimer’s Disease Assessment Scale – Cognitive Subscale (ADAS-Cog) was used to assess cognition, including decline in abilities such as memory and language (higher scores indicating greater impairment). The Alzheimer’s Disease Cooperative Study – Activities of Daily Living (ADCS-ADL) was used to assess functional abilities using a 23-item score (lower scores indicating greater impairment) in activities such as eating, walking, grooming, and dressing. The 3MS is a widely used test for dementia based on the Mini-Mental State Examination (MMSE), but incorporates four added test items, more graded scoring, and some other modifications that are designed to address a broader range of cognitive functions and cover a wider range of difficulty levels (lower scores indicating greater impairment).
''No approved or investigational medication for Alzheimer’s disease has succeeded in a clinical trial of this size and duration. Unfortunately, observations of IG seen in earlier phases of studies of Alzheimer’s patients did not translate into a positive outcome in the GAP study,'' said Norman Relkin, M.D., Ph.D., a neurologist from the Weill Cornell Medical College and GAP Study Leader. ''Analysis of the full study results is still ongoing. I am optimistic that the knowledge we gain from this study will advance efforts to develop effective treatments for Alzheimer’s disease.''
The GAP study was the largest placebo-controlled study of immunoglobulin, and was designed to assess the safety and effectiveness of Baxter’s IG as a potential treatment for signs and symptoms associated with Alzheimer’s disease. The clinical trial treated 390 patients with mild to moderate Alzheimer’s disease across 45 centers in the U.S. and Canada. Patients were randomized to treatment with Baxter’s IG treatment at either 400 mg/kg or 200 mg/kg dosing every two weeks for 18 months, or placebo. All patients were required to maintain their treatment regimen of approved medications for Alzheimer’s disease symptom management.