Shares of MannKind (NASDAQ:56400P706) took more than a 5% haircut on Friday as briefing documents came out for its upcoming FDA advisory committee meeting on Tuesday. The documents are a mixed bag, which should make for a very interesting debate in Tuesday's meeting. The drug, an inhaled form of insulin called Afrezza, had efficacy that looked good for type 2 diabetes, but wasn't as convincing on type 1. There are also potential safety concerns, including an imbalance of lung cancer cases in the drug's cohort which could be associated with inhaled insulin as a drug class. A similar small imbalance, dogged a predecessor product, Pfizer's (NYSE:PFE) Exhubera.

There is a great deal of investor optimism around the sales potential of Afrezza, as an alternative to needles. Investors see Novo Nordisk's (NYSE:NVO) Novalog and Eli Lilly's (NYSE:LLY) Humalog's roughly $1.5 billion each in U.S. sales last year and think it can capture a significant portion, possibly as much as a quarter of that market. However, MannKind's high valuation and significant downside risk if Afrezza is rejected, makes this a stock even serious biotech investors with a Mount Everest-high risk tolerance should probably watch from sidelines. 

In this video, Motley Fool health-care analyst David Williamson looks at MannKind today, ahead of the advisory committee's meeting. The vote could greatly affect the outcome of an FDA decision. David discusses the potential for the drug on the market, and how MannKind would be affected by an FDA rejection.