I feel like you should ask the people themselves what they want. These experimental drugs may save their lives and will help with future medicinal breakthroughs. Assisted suicide is another topic and imo should be allowed, but the two aren't mutually exclusive when it comes to legality.
Well what I mean is that if things go horribly wrong, the experimental patient should have the right to pull their own plug. It should be in place ahead of time considering the unknowns. Would you really want to do a treatment if it could leave you in a forced miserable existence for the next 40 years without any escape?
That situation is an extreme hypothetical and I'd probably take the experimental treatment along with painkillers/cannabis if there's any miserable side-effects. It depends on the person and their tolerance, I'd assume most people would prefer to live and be with their loved-ones. Humans are pretty resilient and they adapt. Nothing is stopping a person from committing suicide on their own if they aren't able to cope in the future.