Big biotechs have gone on a huge run lately. The strength of that run largely emanates from the strength of their pipelines. Blockbuster drugs either just hitting the market or not far from a commercial debut have caused earnings projections to skyrocket, making expensive stocks look cheap in out years.

However, safety issues are a sure fire way to deny these drugs their seemingly pre-ordained profits. And to that end, two of the bigger drugs -- Celgene's Revlimid and Biogen's Tecfidera -- were recently hit with negative safety headlines.

In this video, health care analyst David Williamson discusses whether investors in Celgene and Biogen should be concerned about these sudden safety issues.

Follow David on Twitter: @MotleyDavid.

David Williamson has no position in any stocks mentioned. Follow David on Twitter: @MotleyDavid.

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