RO7105705 is an experimental immunotherapy to treat Alzheimer’s disease being developed by Genentech in collaboration with AC Immune. The therapy is designed to target harmful forms of a protein called tau and stop its spread among brain cells.

How RO7105705 works

Alzheimer’s disease is a progressive neurological disorder and the most common form of dementia. It is characterized by changes in the brain that include the formation of plaques, which are clumps of a protein called beta-amyloid that accumulate outside of brain cells, and tangles, which are twisted strands of tau protein that builds up in brain cells.

Tau normally helps stabilize microtubules, which are structures in the brain cells involved in molecular transport. But in Alzheimer’s, tau proteins clump together rather than sticking to the microtubule.

Scientists do not fully understand how these plaques and tangles lead to Alzheimer’s disease, but think their formation damages brain cells and interferes with signaling between them.

Recent research indicates that the harmful tau protein tangles may spread from one part of the brain to another, suggesting that preventing the spread of tau tangles might slow the progression of Alzheimer’s.

RO7105705 is an antibody that recognizes abnormal forms of tau and is intended to block their spread from one cell to the other.

Antibodies occur naturally in the body and play a role in identifying foreign objects such as bacteria and targeting them for destruction by immune cells. Scientists are able to engineer antibodies to recognize specific targets of their choice for use in research or treatment of disease.

RO7105705 in clinical trials

A Phase 1 clinical trial (NCT02820896) tested the safety and tolerability of RO7105705, as well as its pharmacokinetics, or how it was processed in the body. 

The study, which was completed in 2017, recruited 74 participants, including healthy volunteers and patients with mild-to-moderate Alzheimer’s disease, at the New Orleans Center for Clinical Research in Knoxville, Tennessee.

Participants received a single or multiple doses of RO7105705, or a placebo, either intravenously (injected into a vein) or subcutaneously (injected under the skin). The study was randomized and double-blind.

The primary outcomes measured were adverse events and changes in suicidal thoughts. Researchers also looked for changes in cognitive function and clinical dementia scores in participants with Alzheimer’s. The levels of the RO7105705 antibody in the blood were measured.

The results of this trial have not been published, but Genentech began a Phase 2 clinical trial (NCT03289143) in 2017. The study will be conducted at 74 centers in the U.S., Australia, Canada, France, and Germany, and should be completed in 2022. It aims to enroll approximately 360 participants with mild or prodromal Alzheimer’s, a very early stage of the disease in which memory begins to decline.

RO7105705 or a placebo will be administered intravenously in three different doses in this double-blind study. Participants will be assessed for changes in dementia severity, cognitive function, and ability to perform activities of daily living. Participants’ brain tissue will be examined through positron emission tomography (PET) imaging.

Additional information

Although many treatments being tested for treating Alzheimer’s have targeted beta-amyloid, the protein involved in plaque formation, more attention is being focused on tau-based therapies.

Recently developed PET imaging techniques for tau protein in the brain may help scientists better understand its role in Alzheimer’s disease.

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