A disgruntled employee just looking for a way to get back at the company that fired him, or a legitimate claim of scientific misconduct? That's the billion-dollar question that MannKind (Nasdaq: MNKD) investors face.

Yesterday, news reports said a former employee had filed a lawsuit claiming he was fired in retaliation for raising concerns about clinical trials run in Bulgaria and Russia testing the company's inhaled insulin, Afrezza. MannKind claims the employee was fired for an unrelated reason and it hired an independent investigator, which found no problems with the data coming out of the foreign clinical trial sites.

What's important, though, isn't whether the former employee will win his lawsuit. Rather, it's whether the Food and Drug Administration will come to the same conclusion as the independent investigator or the former employee. Because you know that now, the FDA will be looking closely.

The FDA cited problems with clinical trial sites as the reason for rejecting Johnson & Johnson's (NYSE: JNJ) antibiotic ceftobiprole. Pfizer (NYSE: PFE) got a warning letter from the agency for failing to adequately monitor its clinical trials testing its antipsychotic Geodon in children.

One question I haven't seen answered is whether the FDA has already reviewed this data. Afrezza was already turned down by the agency once, but the company didn't cite problems with clinical trials as being one of the reasons for the rejection.

Afrezza has been through multiple clinical trials with strong results. Even if the data needs to be thrown out, might the trial(s) still be enough to show the drug works? Biodel was in the opposite situation, asking the FDA to throw out data so its insulin product, Linjeta, would reach statistical significance; the FDA didn't go for it.

MannKind was already a risky stock before the recent news. The new news adds additional risk, but also makes the drugmaker cheaper. It remains to be seen whether the two cancel each other out. If you're going to buy, tread lightly, Fools.

Interested in keeping track of MannKind as its PDUFA date for Afrezza approaches? Click here to add it to My Watchlist, which will help you keep track of all our Foolish analysis on MannKind.

Pfizer is a Motley Fool Inside Value recommendation. Motley Fool Options has recommended a diagonal call position on Johnson & Johnson, which is a Motley Fool Income Investor pick. The Fool owns shares of Johnson & Johnson. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.