The company has agreed to pay up to $300m (€228) to Swiss Biotech company AC Immune to licence antibodies developed by their SupraAntigen Technology as potential Alzheimer's Disease treatments.
Genentech will also fund a collaborative research programme.
AC Immune has developed conformation specific antibodies that could remove existing 'amyloid plaques' in the brain, which are thought to cause many of the symptoms observed in Alzheimer's patients.
Alzheimer's disease (AD) is an incurable progressive brain disorder that causes dementia.
Although available treatments can slow the progress of the disease through increasing the production of neurotransmitters lost because of the disease, there is nothing available that can reverse the effects.
Several techniques are being investigated, including experimental gene therapy but have not been approved yet.
"We are thrilled that Genentech has taken such an interest in our Alzheimer's antibody programme," said Martin Velasco, chairman of AC Immune.
"We are hopeful that in collaboration with Genentech we may develop a potential treatment for Alzheimer's for the benefit of millions of patients worldwide."
The amyloid plaques are found between nerve cells in the brains of Alzheimer's sufferers.
They consist of amyloid protein fragments that are normally broken down by the body and removed.
However, in people who suffer from Alzheimer's, the fragments, mainly beta-amyloid build up into hard deposits that can kill surrounding nerve cells.
The SupraAntigenTM Technology has generated a lead anti-beta-amyloid antibody that has been highly active in animal disease models for AD.
The antibody changes the plaques from an insoluble to soluble form, enabling them to be removed by the body.
This was directly linked to improvement of memory.
Genentech will cover all development and clinical costs of the lead antibody and subsequent antibody candidates.
Dr Martin Mader, CFO of AC Immune said: "The terms of the deal will provide AC Immune with a solid financial basis beyond the next three years to develop other programmes at full speed."
Several other companies run Alzheimer's projects.
Samaritan Pharmaceuticals have filed a patent for caprospinol (SP 233), a drug that appears to reduce the toxic effects of beta-amyloid and help remove plaques.
US Pharmaceutical company Elan, have developed ACC-001 in collaboration with Wyeth, New Jersey.
The drug induces an immune response designed to clear beta amyloid and is currently in Phase I clinical trials.
A further study has shown that a drug previously approved for treatment of several immune disorders can also benefit patients with mild to moderate Alzheimer's.
Weill Medical College of Cornell University, New York, have demonstrated that Intravenous Immunoglobulin (IVIg), a purified mixture of human antibodies, can be used to remove amyloid plaques from the brain.
The antibiotics also appear to block the toxic effects of amyloid-beta.