The need-to-know on BioMarin's gene therapy

Hemophilia, which results from a DNA defect, has long been one of the most attractive targets for gene therapy, which promises a one-time fix for inborn errors. But whether such a treatment can actually change patients' lives hinges on just how long it lasts.

That's the key question facing BioMarin, whose hemophilia A gene therapy has looked promising in early studies. As STAT's Adam Feuerstein points out, the company is soon to release data following patients for three years, and investors will be keenly watching how well the treatment holds up.

In prior studies, the gene therapy's efficacy seemed to wane over time, though not so much as to render it ineffective. If it plateaus at three years, as BioMarin expects, that's a good sign for its future as a product. But if the downward trend continues, BioMarin will have explaining to do.

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