Akcea Therapeutics (AKCA) and its controlling holder Ionis Pharmaceuticals (IONS) are moving lower after an FDA panel posted its briefing document ahead of Thursday’s meeting to discuss Akcea’s volanesorsen.

The document reads, “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. Although the reviews highlight several safety/tolerability issues, the primary focus for both the applicant and the reviewers has been the risk of thrombocytopenia and resulting potential for serious bleeding.” It adds, “After the NDA review was well-underway, the applicant unexpectedly submitted an amendment that proposed a new dosing and platelet monitoring strategy for labeling that had not been implemented in any of the clinical trials… Regarding platelet monitoring, the review team (including the hematology consultant) questions the feasibility and effectiveness of a monitoring scheme of this intensity for a lifelong therapy. At present, we have no evidence that the risk of severe thrombocytopenia diminishes with time.”

Shares of Akcea are down 12% in premarket trading, or $2.67, to $19.00 while Ionis is down 2.5% to $43.22.