Shares of Achillion (NASDAQ:ACHN) plunged 25% after the FDA stuck a clinical hold on its key next-gen hepatitis C drug sovaprevir. There has been a history of clinical holds for interferon-free treatment components, but Achillion's problems are different from past struggles seen by competitors.

In this video, health-care analyst David Williamson discusses why today's sell-off may be overdone, but cautions investors to look at the bigger picture surrounding this fledgling small cap.

David Williamson owns shares of Johnson & Johnson. Follow David on Twitter @MotleyDavid.

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