On this edition of Market Checkup, Motley Fool health-care analysts David Williamson and Michael Douglass take a look at two of the weeks biggest biotech losers, and why one of them could make an interesting buy today.

Shares of Exelixis (NASDAQ:EXEL) were hit hard -- down by over a third after announcing that an independent reviewer determined its prostate cancer trial for cabozantinib should continue. While it seems counterintuitive that the market would react badly to that, the expectation was that efficacy would be so high that the trial would be stopped early because of overwhelming success. While the sell-off was massive when that didn't happen, this drug has already been approved to treat thyroid cancer, and the trial in prostate cancer is continuing. David sees this as perhaps an interesting time for investors to get in.

Meanwhile, Insmed's (NASDAQ:INSM) prospects may not be as rosy. The company released phase 2 data for its non-TB mycobacterial lung infection drug Arikayce, and the data was mixed at best. David talks investors through the phase 2 data, discusses why he isn't confident that it will pass phase 3, and mentions that even though is has passed phase 3 in its trials for cystic fibrosis lung infections, there are questions around the strength of those results as well.

David Williamson and Michael Douglass have no position in any stocks mentioned. The Motley Fool recommends and owns shares of Exelixis. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.