NEW YORK -- Shares of Isis Pharmaceuticals Inc. skidded Tuesday as regulators raised questions about links between the company's experimental cholesterol drug Kynamro and cancer.
THE SPARK: Isis and its partner Genzyme will discuss Kynamro with a Food and Drug Administration advisory panel on Thursday. The endocrinology drug committee posted its prepared questions on the FDA's website Tuesday. The committee said Kynamro was linked to both benign and cancerous tumors: 3.1 percent of patients, or 23 people treated with the drug, developed tumors in clinical trials. That compared to two patients treated with a placebo during those studies, or 0.9 percent.
The panel said three patients treated with Kynamro, or mipomersen, died during clinical testing. Two died of heart attacks and one died of acute liver failure. The documents noted that that patient who died of liver failure had other health problems, but said "the potential for a contributing effect of mipomersen cannot be ruled out."
The panel's documents also noted that cancers were seen in preclinical studies on mice, including liver cancers and hemangiosarcomas, or cancers of blood vessel cells.
THE BIG PICTURE: Kynamro is designed to treat a rare genetic condition that causes very high levels of "bad" LDL cholesterol. Isis and Genzyme, a unit of the French drugmaker Sanofi, filed for European Union marketing approval of the drug in July 2011 and filed for U.S. approval in March 2012. The companies expect a decision from EU regulators before the end of 2012 and a ruling from the FDA in January.
The FDA is not required to follow the advice of its panels, but it often does so.
Isis, based in Carlsbad, Calif., gets its revenue comes from development partnership on Kynamro and other experimental drugs.
THE ANALYSIS: Jefferies & Co. analyst Eun Yang said the disclosure about tumors was "quite surprising." She said Kynamro probably won't be approved, and if it is, its market approval will probably be tightly limited because of the side effects and the large proportions of patients who dropped out of clinical studies of the drug.
Yang maintained an "Underperform" rating on Isis shares with a price target of $10.
SHARE ACTION: Isis Pharmaceuticals stock lost $2.47, or 18.8 percent, to $10.68 in afternoon trading. The stock more than doubled in value from mid-April to mid-September, but Isis shares have lost 14.7 percent of their value since Sept. 20 prior to Tuesday's decline.