It wouldn't be unheard of to be required to pay for your own treatment. If a study has a control arm that receives the current standard of care, and they don't have the funding to issue vouchers to cover the costs of meds, you might just have the initial evaluation, followups, and lab work covered. The meds you'll have to get yourself at your pharmacy of choice.

But since it's current standard of care, it would be similar to the same as what your primary care physician would prescribe, and insurance should cover it. You're not technically worse off than you'd be otherwise. And none of the money should ever go to people directly involved.