thanks to sean hobson on flickr creative commons

In a surprise move, the Food and Drug Administration has set separate dates for advisory panels to review two different drugs for Duchenne muscular dystrophy, a rare genetic disorder that leaves young boys wheelchair bound. Most investors and patient advocates expected the agency to hold back-to-back meetings next month.

Instead, one advisory committee meeting will be held on Nov. 24 to review drisapersen from BioMarin Pharmaceutical, while eteplirsen from Sarepta Therapeutics will be scrutinized on Jan. 22, 2016.

Normally, such doings do not generate much notice, especially for rare disease drugs. But the Duchenne drugs have been the focus of intense interest over the past few years thanks to a combination of unusual circumstances.

Study data, for instance, have been controversial. A late-stage trial for the BioMarin drug flopped and the company then submitted a new analysis for regulatory approval. And Sarepta is relying on a trial that involves just 12 patients. Despite perceived shortcomings and ambiguity, both drug makers hope the FDA will grant accelerated approval, which means a faster regulatory review would take place.

Meanwhile, families of Duchenne patients have been extremely vocal in raising awareness, but have also pursued some unique advocacy strategies to press the FDA. One parent group convened its own collection of experts to write draft guidelines for Duchenne drug development, which the agency used as a template to develop its own set of guidelines.

So any action by the FDA prompts a new round of reading tea leaves.

We asked Janet Woodcock, who heads the FDA’s Center for Drug Evaluation and Research, why the panel meetings are scheduled separately, but she declined comment. She would only say that panel meetings are generally scheduled to reflect agency deadlines for approving or rejecting a drug. The BioMarin deadline is in December and the Sarepta deadline is in February.

Still, Duchenne parents and analysts are puzzled since the agency has previously held two-day panel meetings to review different drugs for the same medical purpose.

One analyst headlined his investor note this way: “FDA weirdness continues in DMD.”

“Holding two [meetings] two months apart appears to be an absurdly inefficient use of resources that will require many of the same players to make two separate trips to Maryland to review much of the same background information,” wrote Brian Skorney of R.W. Baird. “The only thing we think is really clear is that the FDA is as erratic and unpredictable as ever when it comes to DMD and the most rational decision isn’t necessarily the one that the FDA makes.”

For now, though, the FDA panel meetings are being viewed as a win for BioMarin and a setback for Sarepta. BioMarin stock is up about 6 percent so far today, and Sarepta is down about the same.

Here’s why: Meeting an unmet medical need is a huge factor. If the FDA panel recommends regulatory approval next month for the BioMarin drug, it would reduce the pressure on the FDA panel that meets in January to endorse the Sarepta drug. As Skorney pointed out, the BioMarin drug will “benefit from a psychology that says ‘If you don’t approve this, DMD boys have no option.’”

We should note that the underlying cause of the disease is a mutation in the gene for dystrophin, a key protein involved in muscle function. The drugs are designed to skip a so-called exon – or section – of the dystrophin gene to alter specific mutations and restore the ability to make a useful form of dystrophin.

And so, the next round of intrigue will take place in mid-November, when FDA medical staffers post their review of the BioMarin drug. Parents and investors will be picking through the documents for clues about how to interpret the prospects for both treatments.

Until then, the tale of the Duchenne drugs will remain enigmatic.