What

Shares of Akcea Therapeutics (NASDAQ:AKCA) are up 13% at 11:33 a.m. EDT today after the Food and Drug Administration's Metabolism and Endocrinology Products Advisory Committee voted 12-8 recommending the approval of Waylivra for a rare genetic disease called familial chylomicronemia syndrome (FCS). As typically happens for smaller biotechs, shares of Akcea were halted yesterday since the meeting was likely to cause volatility.

Ionis Pharmaceuticals (NASDAQ:IONS), Akcea's majority owner and the developer of Waylivra, is up 4.4% on the news as well.

So what

A 12-8 vote isn't exactly a ringing endorsement, but it was pretty clear from the FDA documents for the committee, which were publicly posted on Tuesday, that the agency reviewers were torn between the efficacy and safety of Waylivra, which also goes by the generic name volanesorsen. Patients with FCS have elevated levels of triglycerides (TG), which Waylivra clearly helps reduce, but the drug is also associated with thrombocytopenia, or low blood platelet levels.

Three blood vials lying on top of diagnostic test order form

Image source: Getty Images.

"Despite the magnitude of the effect observed on TG, the volanesorsen review team remains uncertain whether the benefits of volanesorsen outweighs its risks, considering safety concerns with this product," James Smith, the FDA's deputy director of the division of metabolism and endocrinology products, wrote in the briefing documents.

Those documents sent shares of Akcea and Ionis down on Tuesday. Nonetheless, both companies are trading higher today than they were when the week started, which seems reasonable given the committee's endorsement.

Now what

An approval is by no means a slam dunk at this point. The FDA gets to make the final decision and doesn't have to follow the committee's recommendation. Given the eight dissenting votes, it's clear the committee was as conflicted as the FDA reviewers.

Adding to the issues, Akcea has proposed changing the dosing of the drug and monitoring for thrombocytopenia compared to what was done in the clinical trial. The FDA may end up rejecting the drug, asking the company to test its proposal in a new clinical trial to see if it can reduce the incidence of the side effect.

Investors won't have to wait too long to find out whether Waylivra will be approved. The FDA plans to decide by Aug. 30.

Brian Orelli has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Ionis Pharmaceuticals. The Motley Fool has a disclosure policy.