What happened

Shares of biotech Epizyme (EPZM) have been a bit sickly this week, following the departure of one of its top executives. As of Thursday's market close, the stock was down nearly 13% from the start of the week.

So what

The outgoing executive is CFO Paolo Tombesi, whom Epizyme announced is stepping down from his post effective Friday, July 16. The company wrote without elaboration in a regulatory document filed on Monday that he is to "pursue other business opportunities."  

Cancer attacking an organism.

Image source: Getty Images.

Filling his spot as what the company terms its "principal financial officer" will be Matthew Ros, the chief strategy and business officer. Ros has served in this capacity for the company previously. He joined his current employer in 2016 and has also been chief operating officer at the biotech.

According to his LinkedIn page, prior to his time at Epizyme, Ros worked in high management positions at pharmaceutical industry heavyweights Sanofi and Bristol Myers Squibb, among others.

Now what

Epizyme did not address how Tombesi's departure might affect its operations. The company has one drug on the market, Tazverik, which was approved last year to treat certain instances of both epitheliod sarcoma, a relatively rare cancer of the soft tissue, and blood cancer follicular lymphoma.

While it's no blockbuster, it did earn almost $6.2 million in revenue for the company in its firs quarter, and the company has other cancer drugs in the pipeline. That potential, combined with the apparently smooth transition between top financial officers, makes the market's sell-off feel like an overreaction.