GlaxoSmithKline’s (GSK) experimental drug Promacta (eltrombopag) failed to significantly lower bleeding in patients with the rare blood disorder it was designed to treat, the FDA said.

An unnamed agency reviewer said in a document posted to the FDA’s website that studies comparing Promacta to placebo showed some bleeding control but not enough to support the company’s claims for treating chronic idiopathic thrombocytopenia purpura, an autoimmune disease that reduces blood platelets crucial for blood clotting.

“Although a trend toward reduced incidence of bleeding is observed in the eltrombopag group compared to placebo, this trend is not statistically significant and does not provide robust evidence to support the proposed labeling claim,” the FDA said.

Click here to read the full FDA advisory committee briefing document.

The document was released ahead of an agency advisory panel meeting on Friday to discuss Promacta. While the FDA will ultimately make the final approval decision, it usually follows the advice of its advisory panels.