While many rightfully worry about major health issues such as heart disease, cancer and drug resistant infections, the biggest looming crisis could well be Alzheimer’s disease (AD). As baby boomers get older, more and more will suffer from this disease. Yet, other than palliative treatments such as Pfizer’s Aricept (generic name: donepezil) and Allergan’s Namenda (memantine), which only stave off AD for a relatively brief time, there are no drugs available to halt or reverse this crippling disease.

The dearth of AD drugs isn’t due to a lack of trying. Numerous companies have sought new treatments but greater than 99% of drugs that have entered clinical trials have failed. However, there still are two promising compounds in late-stage development: Lilly’s solanezumab and Biogen’s aducanumab. Solanezumab is an injectable antibody designed to bind to and promote the clearance of the beta-amyloid protein which forms plaques around neurons of people with AD. To date, clinical trials with solanezumab have been disappointing, but Lilly believes that its ongoing late-stage trial will show the benefit of this drug in enhancing cognition in mild AD patients.

While many rightfully worry about major health issues such as heart disease, cancer and drug resistant infections, the biggest looming crisis could well be Alzheimer’s disease (AD). As baby boomers get older, more and more will suffer from this disease. Yet, other than palliative treatments such as Pfizer’s Aricept (generic name: donepezil) and Allergan’s Namenda (memantine), which only stave off AD for a relatively brief time, there are no drugs available to halt or reverse this crippling disease.

The dearth of AD drugs isn’t due to a lack of trying. Numerous companies have sought new treatments but greater than 99% of drugs that have entered clinical trials have failed. However, there still are two promising compounds in late-stage development: Lilly’s solanezumab and Biogen’s aducanumab. Solanezumab is an injectable antibody designed to bind to and promote the clearance of the beta-amyloid protein which forms plaques around neurons of people with AD. To date, clinical trials with solanezumab have been disappointing, but Lilly believes that its ongoing late-stage trial will show the benefit of this drug in enhancing cognition in mild AD patients.

Early-stage clinical studies of Biogen’s aducanumab, also an amyloid-targeting antibody given by injection, showed promising reduction of beta-amyloid in the brain in a dose-dependent fashion. Biogen is rapidly moving its drug into late-stage trials. However, both antibodies pose the risk of vasogenic edema (amyloid-related imaging abnormalities or ARIA-E), which could limit their ultimate use and/or effectiveness.

Trying to compete with these large players is Alzheon, a small biotech company in Framingham, Mass. At first pass, it looks like Alzheon has little chance in making a difference for AD patients. It is developing ALK-801, a prodrug of an old compound, tramiprosate (homotaurine). Tramiprosate was taken into late-stage clinical trials by its originators, Neurochem/Bellus Health. Unfortunately, tramiprosate did not meet the primary outcome goals in phase 3 and the compound was dropped almost a decade ago.

So why is anyone bothering with this failed drug? According to Alzheon CEO Martin Tolar, tramiprosate did offer hints of efficacy, particularly in patients who were APOE4-positive. Since that time, there has been a number of advances in the field that now make this inhibitor of beta-amyloid aggregation very intriguing as an AD treatment:

1. Development and approval of amyloid PET imaging–this has shown that clinical diagnosis of AD in mild to moderate AD patients is not accurate in up to 30% of patients (who do not have brain amyloid pathology on amyloid PET imaging).
2. The rate of negative amyloid scans in mild to moderate AD is highest in APOE4/4 non-carriers (40%) and lowest in APOE4/4 homozygotes (5%). Thus, inclusion of APOE4 non-carriers in the earlier pre-PET imaging trials of amyloid-targeting drugs like tramiprosate resulted in trials very unlikely to succeed.
3. With amyloid-targeted agents, it is critical that intervention occurs at the early to mild stage of the disease to demonstrate slowing of disease progression. Intervention later than this is probably too late.

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