It can be tempting to omit some details about your company in an investor presentation. Especially in the healthcare industry with its complicated data from clinical trials it is definitely possible to hide something from a potential investor until very far into the due diligence process.
A due diligence process that can takes weeks, sometimes months. You enter an exclusivity period, stop talking to other investors, continue to burn money until... the investor finds out. You lose the investment, probably not because the company all of a sudden looks completely bad, but because of you burned your integrity, your trust with a potential new Board member. And by that time your company could have run out of finances and have no other investors to talk to anymore.
Do not make an investor presentation that emphasizes your weaknesses with all the visual power in the world, on the other hand, be honest.