Ooo... got me there. I'm sure there are some but I can't name any notable MDs who've made an impact in biotech ... I just don't know my biotech history all that well.
Typically, for drugs at least, what happens is someone (med school/biotech research) discovers a "target" protein, then passes the protein to a medicinal/organic chemist to develop a molecule to block it, picks a "lead" molecule, hands it off to vets and biologists to animal test it, then hands it off to physicians to test it in humans (development). During this time, they can choose to "partner-out" if they want to (i.e. hand it off to a larger pharmaceutical company with better manufacturing capacity, clinical testing network, FDA know-how, commerical marketing capacity) for different payment schedules that compensates for the amount of risk that is eliminated as the molecule moves through the trials. This is mainly a business decision.
So when you say "impact" there are a lot of people involved, which typically starts with the PhD's as starters, MDs in the middle, and MBAs as closers. And depending on the company, the leadership will reflect which stage the company is in. A PhD will very likely be a CEO of a company in discovery, an MD in clinical development, and an MBA in commerical mode. So there will be many MDs in leadership positions, but they may or may not have an impact because we have yet to see whether or not their drugs will be successful. And typically, if the company is intent on building a pharmaceutical company out of a biotech company, they will replace leadership as the company matures. If the company decides to outsource their commercial capacity, or outsource their discovery capacity, the leadership will reflect what kind of skills they have in-house... but these aren't absolutes. Other times, they get bought out, and the MDs/PhDs move on to the next start-up.
CEOs are typically the public figure for the company. They lead the company strategically, but not on the day-to-day. They also go out on the road and raise money, which means that they need to know people and know business... which is why a lot of the successful biotechs (oxymoron) have business people leading them (Amgen is the classical biotech). MDs and PhDs typically are pushed to the side because they spend too much of their lives in training and therefore don't usually get the job, unless they themselves have left medicine for a while and been in the business for a long time.
But if you want to read up on various public biotech companies and the people behind them, check out the websites of these companies (go to About Us, Management, Board)... Management tends to be people in the industry, MDs, PhDs... while Board people will include investor/Wall Street, people from other businesses, MDs, PhDs, whatever. The bios talk about all their successes and so you can worship them as you please. Obviously, none of them will talk about their failures:
Amgen, Cephalon, Chiron, Genentech, Genzyme, Gilead, Human Genome Science, Medimmune, Millenium, Sepracor, Teva, Vertex,
I don't think I answered your question at all.