I wouldn't proceed. The problem is your partner did his work previously and your friend feels like he has a 100 million dollar worth of value. How is he going

I wouldn't proceed. The problem is your partner did his work previously and your friend feels like he has a 100 million dollar worth of value. How is he going to extract that 100 million? Through the company you will build for him. Any licease he assigns he will want 100m value for it. If things go well problems will start over how much each should get. If things don't he has an escape route ready. Worse if things go really well he can sell a licease to another company with bigger pockets. I would create my own company and buy access to his patient through a percent of ownership + a fixed amount per product/service sold for a period of time with the right to renew.