This episode of The Motley Fool's Market Checkup drills down on the hottest headlines and biggest market movers in the health-care sector. 

In this video, health-care analysts David Williamson and Max Macaluso discuss Ariad Pharmaceuticals' shocking 66% plunge. The drop came from safety issues regarding its only approved drug, Iclusig. Ariad plans on adjusting the dosing downward so patients can continue on their trials.

Currently, Iclusig is a secondary treatment for leukemia, but it is hoping to become a frontline drug for the disease as well as picking up seven additional indications. That is why the sell-off was so steep: Tolerability issues could hamper its sales in all of its indications and make it a drug of last resort in leukemia, where there are already a number of deep-pocketed competitors.

Watch and find out what today's news means for Ariad shareholders and its competitors.

David Williamson owns shares of Pfizer. Max Macaluso, Ph.D. and The Motley Fool have no position in any of the stocks mentioned. 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.