Shares of Isis Pharmaceuticals Inc. fell the most in 4 1/2 years after U.S. regulators raised concerns about abnormal growths, some harmful, linked to the company’s drug for a rare genetic disease.
Isis, which is a partner with Paris-based Sanofi on the medicine, declined 22 percent to $10.27 at the close in New York, the biggest single-day drop since April 2008. The Carlsbad, California-based company had risen 82 percent in the year through Monday.
In clinical trials, the growths, or neoplasms, developed in 3.1 percent of patients treated with the drug Kynamro and 0.9 percent of patients who took a placebo, Food and Drug Administration staff said in a report released today before an Oct. 18 meeting of agency advisers. The interpretation of the data is limited by a small sample size and a short treatment time, the staff said. The injection, Isis’s lead product candidate, helps lower LDL, or bad, cholesterol in patients who have very high levels, FDA staff said Tuesday.
“This imbalance in neoplasms will need to be assessed further in on-going and future studies and post-marketing (if approved),” FDA staff wrote.
The malignancies are a “new concern” and the reason for weakness in the shares, Eric Schmidt, an analyst with Cowen & Co. said in an e-mail.
The FDA is scheduled to make a final decision on the drug by the end of January.
Nine of the 23 growths in patients treated with Kynamro were malignant, according to the report. One of the two growths in the patients treated with placebo were harmful. There were a total of 749 patients who took the drug and 221 on placebo.
Kynamro, also known chemically as mipomersen, targets a disease known as homozygous familial hypercholesterolemia that causes abnormalities in liver cells responsible for clearing LDL, or low density lipoprotein, particles from the blood. The disease can lead to heart attack or death at an early age, according to the National Institutes of Health.
The FDA staff also said it is concerned about the treatment’s effect on the liver and that the harm can be mitigated with a risk plan that targets patients.
A risk plan would “support appropriate use of mipomersen, allowing it to be approved for use in the targeted patient population, a patient population with life threatening illness and limited therapeutic options,” staff wrote.
FDA staff yesterday said a plan to manage the risk of a similar drug from Aegerion Pharmaceuticals Inc. supports its approval in adults with the genetic disease. The agency is scheduled to decide on the treatment, lomitapide, by the end of December.
Isis says its drug reduced LDL cholesterol by 25 percent in patients with homozygous familial hypercholesterolemia in two late-stage trials, compared with 3.3 percent for those on placebo. In four late-stage trials, 8 percent of patients treated with Kynamro experienced elevated levels of an enzyme that indicates liver damage.
People with homozygous familial hypercholesterolemia can have cholesterol levels two to four times higher than normal and don’t respond to standard cholesterol-lowering drugs such as Pfizer Inc.’s Lipitor. Isis and partner Paris-based Sanofi, France’s largest drugmaker, may draw $480 million in worldwide sales, Schmidt said. He has a neutral rating on Isis and owns Aegerion stock in a personal account.
Isis in a 2008 agreement with Sanofi will get 30 percent to 50 percent of Kynamro profits based on drug sales. Isis may generate $183 million in U.S. sales in 2016 from Kynamro, according to the average estimate of four analysts surveyed by Bloomberg.
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