There's never a shortage of losers in the stock market.

Let's take a closer look at five of this past week's biggest sinkers.

Company

Dec. 16 Weekly Loss My Watchlist
Endocyte (Nasdaq: ECYT) $3.06 (72%) Add
Sequans (NYSE: SQNS) $2.28 (42%) Add
InterMune (Nasdaq: ITMN) $11.09 (36%) Add
K12 (NYSE: LRN) $18.90 (34%) Add
First Solar (Nasdaq: FSLR) $31.91 (30%) Add

Source: Barron's.

Endocyte called in sick after a cancer-fighting drug candidate was shown not to increase survival in a subset of ovarian cancer patients during a phase 2 clinical trial. When you're an upstart biotech with one hot potential drug, a setback in the approval process can be devastating.

Sequans disconnected with investors after the French 4G chip maker dramatically hosed down its near-term outlook after its largest customer canceled 60% of a major order. It's amazing to think that Sequans went public at $10 earlier this year, and is now trading for a small handful of quarters.

InterMune tumbled when a German advisory group -- similar to our FDA -- came to the conclusion that the benefits of its once-promising drug candidate aren't worth the gastrointestinal and skin damage side effects.

K12 got expelled from portfolios after a scathing New York Times expose played up the virtual classroom specialist's shortcomings.

Finally, First Solar lost some of its power after the company issued bleak guidance for 2011 and 2012.

It was a rough week for these five stocks. If you want to shake yesterday's losers and ride tomorrow's winners, a new special report reveals The Motley Fool's top stock for 2012. It's free, but only for a limited time, so check it out now.

The Motley Fool owns shares of First Solar. Motley Fool newsletter services have recommended buying shares of K12 and First Solar. 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. The Motley Fool has a disclosure policy.

Longtime Fool contributor Rick Munarriz calls them as he sees them. He does not own shares in any of the stocks in this story. Rick is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early.