Shares in Cornerstone Therapeutics have taken a tumble after advisors to the US regulator voted unanimously against recommending lixivaptan for the treatment of hyponatraemia in patients with congestive heart failure.

Specifically, the Cardiovascular and Renal Drugs Advisory Committee of the US Food and Drug Administration recommended against the approval of lixivaptan for the treatment of symptomatic hypervolemic and euvolemic hyponatraemia associated with heart failure. The panel also voted 5-3 against the drug's use in syndrome of inappropriate antidiuretic hormone (SIADH).

The votes came as a disappointment given that earlier in the week, FDA staffers had backed approval. However the committee reviewers were not impressed and decided the drug's risks outweighed its modest benefit in raising sodium levels and suggested more trials are required. Lixivaptan  works by reducing the action of a hormone (vasopressin) that blocks fluid excretion.

Cornerstone chief executive Craig Collard said that "while we respect the views of the CRDAC, we view [the vote] as another step in the process of bringing lixivaptan to market for patients with hyponatremia using the established surrogate endpoint of serum sodium correction". He added that the firm will work with the FDA throughout the approval process "building upon meeting our primary endpoint in each pivotal Phase III trial".

Hyponatraemia, a metabolic condition that occurs when there is not enough salt in the blood, is the most common electrolyte disorder among hospitalised patients affecting up to six million people in the USA and is often diagnosed in patients with heart failure. Cornerstone says direct medical costs range between $1.6-$3.6 billion annually.

Lixivaptan was first developed by Wyeth which licensed it to Cardiokine. The latter then sold rights to the drug  to Biogen Idec which returned them in November 2010. Cornerstone acquired Cardiokine at the beginning of this year.

The FDA has assigned a Prescription Drug User Fee Act goal date of October 29, 2012, and although the agency is not bound by the committee's recommendations, investors fear the worst. Cornerstone's stock ended the day down 21.2% at $5.10.