Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of cancer-drug developer Dendreon (Nasdaq: DNDN) were getting slammed today, losing 23% as investors reacted to the company's continued struggles to grow sales of its key prostate-cancer treatment.

So what: On the bright side, both revenue and profit for Dendreon's second quarter were moving in the right direction. Sales increased 66% from last year to $80 million, while the company's $116 million loss from last year narrowed to $96 million. That was short of what investors were hoping for, though, as Wall Street analysts had estimated $85 million in sales for the quarter.

In addition, Dendreon announced that it's closing a manufacturing facility in New Jersey and laying off 600 workers in an effort to slash $150 million in costs over the next year. The company's CEO called this a "new course for Dendreon," but it's no wonder investors see it as a big black eye. The restructuring is a sign of the company essentially admitting defeat on its high growth targets.

Now what: Of the factors limiting growth during the quarter, the company's concern over having sales reps jump ship seemed particularly significant. Motley Fool biotech expert Brian Orelli was skeptical of whether this really would have decreased sales. He wrote, "Are doctors so uninterested in Provenge that if the sales rep isn't in their office on a regular basis, they forget about prescribing it?"

Further, if Provenge and Dendreon more broadly were charging ahead and offering a good opportunity for sales reps, would we be seeing this turnover? I'd assume not. Investors should consider whether this turnover further underscores the troubles Provenge has had getting the kind of traction that was originally expected.

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