New Drugs Target Alzheimer’s Disease

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Rapidly Growing Immunotherapy Pipeline Offers Hope of Disease-Altering Therapies

Targeting Alzheimer's Disease

Few conditions are more devastating than Alzheimer's Disease (AD). This neurodegenerative condition affects 10% of individuals over the age of 65, and carries a high personal and financial toll for patients and their families. In the US, the average lifetime cost for individual patient care is $174,000, while countrywide costs, both direct and indirect, are estimated at $100 billion per year.

Despite many years of research, treatments are limited. Current therapies are dominated by two drug classes: the cholinesterase inhibitors (e.g. Aricept®) and, more recently, an NMDA receptor antagonist (e.g. Ebixa®). While these drugs offer benefits to some patients, there is an urgent need for improved treatments and, in particular, for therapies that modify the course of the disease.

Recent years have seen new drug classes enter the pipeline. However, one area in particular is attracting significant interest; the development of immunotherapeutic drugs. This area is seeing the greatest growth in the AD field, giving hope that new disease-modifying treatments might soon be available.

Immunotherapeutic drugs broadly divide into two groups: vaccines, that elicit an active immune response (generating antibodies that target the disease), and therapeutic antibodies, that bypass the immune system and directly target the disease (so-called passive immune therapy). Today, the majority of candidate immunotherapies target amyloid beta (Abeta), which is believed to play a key role in the pathogenesis of AD. A new report by Biopharm Reports reveals rapidly expanding developments in this field, with 35 candidate drugs in the pipeline (17 vaccines and 18 antibodies).

The first immunotherapy candidate drug for AD was AN1792, a vaccine developed by Elan, which entered Phase I in 1999. A Phase II study soon followed, however this was terminated when ~6% of patients developed meningoencephalitis and leukoencephalopathy.

Since the clinical trials of AN1792 almost a decade ago, efforts have been made to understand why this vaccine produced adverse reactions in some patients. Given that AN1792 targeted a molecule, namely Abeta, thought to be involved in the development of AD, it was important for drug developers to explore the underlying reasons for the adverse effects, to allow corrective steps to be taken before other attempts were made to target this molecule. These efforts have also thrown further light on the challenges of developing vaccines, as well as antibodies, to target Abeta. This field has also seen significant innovation in recent years and collectively these advances are now addressing areas thought to be critical to the development of immunotherapeutic drugs to target AD. These include the need to avoid the inflammatory T-Cell response (linked to the adverse reactions to AN1792) and, instead, to elicit the anti-inflammatory B-Cell response; the mechanistic targeting of Abeta; the need to elicit an adequate immune response; transport across the blood brain barrier; improved drug discovery and better early testing and other areas. Collectively, these advances are driving the innovation now being seen in this field.

How soon will clinical data be available? Currently, therapeutic antibodies are more advanced in the pipeline, than vaccines. Three antibodies (Janssen’s Bapineuzumab, Baxter’s Gammagard and Lilly’s Solanezumab) are at Phase III, with data on the outcome of these studies expected in 2011-2012. On the vaccine front, three candidates are now at Phase II. These developments offer hope for new disease-altering AD therapies in the near future.

For further details of this report, contact Biopharm Reports

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John Bates
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