An appeals court has ruled that Aetna Inc. can pursue litigation against Pfizer Inc. for its off-label marketing of a drug for a variety of ailments other than its approved use in treating epilepsy.

The ruling was one of several issued Wednesday by the 1st U.S. Circuit Court of Appeals in connection with New York-based Pfizer's alleged fraudulent marketing of Neurontin.

According to the ruling in In re: Neurontin marketing and sales practices litigation, Aetna Inc. v. Pfizer Inc.; Warner-Lambert Co. L.L.C., Neurontin was approved by the U.S. Food and Drug Administration in 1993 for use as an add-on therapy in treating epilepsy, and Hartford Conn.-based Aetna added the drug to its formulary soon after.

However, in late 1995 and early 1996, Parke-Davis began marketing Neurontin as an effective treatment for uses including bipolar disorder and neuropathic pain, although the FDA had not approved it for these off-label uses, according to the ruling. Parke-Davis was a subsidiary of Warner-Lambert Co. L.LC., which Pfizer acquired subsequently.

According to expert testimony, Pfizer's off-label marketing accounted for 99.4% of the Neurontin prescriptions written by psychiatrists for bipolar disorder and 70% of the Neurontin prescriptions for neuropathic pain, among others. Aetna, though, presented studies, showing the drug was no more effective than a placebo for treating either condition, as well as other conditions for which it had been marketed off-label.

In 2004, Warner-Lambert agreed to plead guilty and pay more than $430 million to resolve criminal charges and civil liabilities in connection with its promotion of Neurotoxin, according to the Department of Justice.

Aetna was among those that filed suit against Pfizer in federal court in Boston in 2005. A lower court dismissed Aetna's claims in 2011.

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In reinstating the case, a unanimous three-judge appeals court panel said, “Aetna presented evidence of causation and damages sufficient to survive summary judgment on its (Racketeer Influenced and Corrupt Organizations Act) claims and its Pennsylvania Insurance Fraud Statute claim.”

The appeals court held that while it agreed with the lower court that Aetna did have the burden of segregating the defendant's misrepresentations from damages caused by other sources, it disagreed with the District Court on the RICO claim and said this did not mean it was required to prove the doctor's prescriptions were caused by the defendants' alleged fraudulent misrepresentations.

In a related ruling Wednesday, the same three-judge panel affirmed jury verdicts against Pfizer of more than $140 million for Oakland, Calif.-based Kaiser Health Foundation Health Plan Inc. and related entities for off-label prescription use of Neurontin.

In addition, the panel reversed a lower court ruling dismissing a putative class action suit brought by plaintiffs including Haleyville, Ala.-based Harden Manufacturing Corp. in relation to Neurotoxin.

“Based on the record evidence, the Harden plaintiffs are not so differently situated from Kaiser that they should be precluded from proving their case to a jury,” the appeals court panel ruled.