A study to state how safe RO7126209 is at different doses and how the body processes RO7126209

1. Why is the BP42155 clinical trial needed?

As people get older, the chances of having Alzheimer's disease go up. In fact, about 5% to 8% of people aged 60 and above have this condition.This disease is caused by a buildup of something called beta-amyloid plaques in the brain. Scientists are testing treatments that can help stop or reduce the buildup of beta-amyloid as a potential treatment for Alzheimer's disease.

2. How does the BP42155 clinical trial work?

This clinical trial is recruiting people with a health condition called Alzheimer’s Disease. People can take part if they are between 50 and 85 years of age (inclusive) who have been diagnosed with prodromal Alzheimer’s Disease, or mild to moderate Alzheimer’s Disease and fulfill all of the given inclusion criteria. The study will have four parts:

• Part 1 will test different doses of RO7126209 OR placebo for 28 weeks in a placebo-controlled study. Placebo-controlled studies are when people are put in groups that get given either a medicine or a placebo.
• Part 2 will further characterize doses previously tested in part 1, and may use a different dosing regimen or combination of doses (but the number of doses and the frequency of dosing will not be higher than what has been tested in part 1), participants will get RO7126209 OR placebo.
• Part 3 will be an open-label study (all participants will receive RO7126209) to see how different dosing schedules affect the treatment's outcomes.
• Part 4 will be an open-label study (all participants will receive RO7126209) offered to all participants who completed Part 1, 2 or 3, to assess the long-term safety, tolerability, and other effects of RO7126209 over a period of 101 weeks.

The clinical trial doctor will see participants regularly.These hospital visits will include checks to see how the participant responds to the treatment and any unwanted effects they may have. Total time of participation in the clinical trial will be 68 weeks for Parts 1 and 2, 64 weeks for Part 3 and 129 weeks if participating in Part 4. Participants can stop trial treatment and leave the clinical trial at any time.

3. What are the main endpoints of the BP42155 clinical trial?

The main clinical trial endpoints (the main results measured in the trial) are the changes in the amount of substance, called amyloid, in the brain before and after treatment. The unwanted effects of the drug, like how often they happened, how severe they were, and when they occurred, are also measured. Other important things measured in the study include how much of the drug was in the blood and brain fluid, and if the body made any special antibodies against the drug. These measurements are taken at different times during the study. Overall, the measurements are to see if the drug is safe and effective, and if it had any impact on the brain and body.

4. Who can take part in this clinical trial?

People can take part in this trial if they have been diagnosed with prodromal or mild to moderate Alzheimer’s Disease and aged between 50 and 85 years old. People may not be able to take part in this trial if they have any evidence of a condition other than Alzheimer’s Disease that may affect cognition. Some other things that might prevent someone from participating in this study are if they have serious problems in their brain, if they have had certain mental health conditions like schizophrenia or depression, if they have had cancer in the past or are currently being treated for it, if they have had certain blood or eye diseases, if they have heart problems like atrial fibrillation or high blood pressure that is not controlled or if they have had renal disease.

5. What treatment will participants be given in this clinical trial?

Part 1 and Part 2 of this clinical trial are a ‘placebo-controlled’ clinical trial, which means that one of the groups will be given a substance with no active ingredients (also known as a ‘placebo’); it looks like the drug being tested but does not contain any real medicine. Comparing results from the different groups helps the researchers know whether any changes seen result from the drug or occur by chance.

Part 1 and Part 2 are also a double-blinded trial, which means that neither the participant nor the clinical trial doctor can choose or know the group the participant is in, until the trial is over. This approach helps to prevent bias and expectations about what will happen. However, the participant’s clinical trial doctor can find out which group the participant is in, if their safety is at risk. This approach helps to prevent bias and expectations about what will happen.

Everyone who joins this clinical trial will now be entering Part 2 where dose levels of RO7126209 previously tested in Part 1 will be characterized further. They will be split into groups randomly and given either RO7126209 or non-active medicine (placebo). The first dose will be administered slowly over a period of 4 hours. If this is assessed to be safe, the next doses will be delivered over a period of 2 hours.

These groups may be further divided, where a different dose, dosing frequency and/or number of doses might be tested, but will never exceed what has been tested in the previous part 1.

Part 3 of this trial is unblinded and the patients will be split into two groups in a 1:2 ratio. The different groups will overall receive the same cumulative dose of RO7126209 but with different dosing frequencies. This is to determine the best dosing frequency of RO7126209.

Part 4 of this clinical trial is open-label, which means everyone involved, including the participant and the clinical trial doctor, will know the clinical trial treatment the participant has been given.

6. Are there any risks or benefits in taking part in this clinical trial?

The safety or effectiveness of the experimental treatment or use may not be fully known at the time of the trial. Most trials involve some risks to the participant. However, it may not be greater than the risks related to routine medical care or the natural progression of the health condition. People who would like to participate will be told about any risks and benefits of taking part in the clinical trial, as well as any additional procedures, tests, or assessments they will be asked to undergo. All of these will be described in an informed consent document (a document that provides people with the information they need to decide to volunteer for the clinical trial).

Risks associated with the clinical trial RO7126209

Participants may have side effects (an unwanted effect of a drug or medical treatment) from the RO7126209 used in this clinical trial. Side effects can be mild to severe, even life-threatening, and vary from person to person. Participants will be closely monitored during the clinical trial; safety assessments will be performed regularly.

Participants will be told about the known and possible unwanted effects of RO7126209 based on human and laboratory studies or knowledge of similar drugs. RO7126209 and placebo will be given with intravenous infusion (via a tube linked to a small needle in the participant's vein). Participants will be told about any known unwanted effects of intravenous infusion.

Potential benefits associated with the clinical trial

Participants' health may or may not improve from participation in the clinical trial. Still, the information collected may help other people with similar medical conditions in the future.