B-M's ENKAID SHOULD BE APPROVED FOR SYMPTOMATIC VENTRICULAR ARRHYTHMIAS, BUT NOT MALIGNANT OR SUPRAVENTRICULAR ARRHYTHMIAS, FDA ADVISORY CMTE. SAYS
Bristol-Myers' Enkaid (encainide) should be approved for the treatment of symptomatic ventricular arrhythmias, FDA's Cardio-Renal Drugs Advisory Cmte. unanimously agreed at its July 25 meeting. The cmte. based its recommendation on the results of four clinical trials identified as establishing the efficacy of encainide by the cmte. reviewer Richard Gillis, PhD., Georgetown University Schools of Medicine and Dentistry. Gillis told the cmte. that Bristol-Myers' dose titration trial, placebo control trial, quinidine/encainide comparative trial, and reduced dose titration trial with a placebo control, which together totalled approximately 450 patients, supported efficacy of the compound for the treatment of symptomatic ventricular arrythmias. Commenting on the data, cmte. member Philip Reid, MD, Sinai Hospital, Baltimore, Maryland, said: "It seems to me the data are quite clearly presented in showing that Enkaid is effective in reducing significantly the incidence of simple ventricular arrhythmias as defined by most general definitions." He added: "It also has been shown to be effective in reducing the more complex ventricular arrhythmias such as ventricular tachycardia when compared to either placebo or to an active agent such as quinidine." In Bristol -- Myers' eight-center placebo controlled trial, 125 patients were randomized to receive either 10 mg encainide t.i.d., 25 mg encainide t.i.d., 50 mg encainide t.i.d., or placebo for two weeks. Bristol-Myers told the cmte. that on day 14 of treatment, 51% of the patients on 50 mg. encainide and 45% of the patients on 25 mg encainide responded to treatment, compared to 3% of patients on placebo. In the same study, on day one of treatment, patients receiving 25 mg encainide had a 56% reduction, while those receiving placebo had a 4% increase. By day 14, the PVC median reduction was 69% for patients on 25 mg encainide, 86% for patients on 50 mg encainide, while patients receiving placebo showed an 11% increase in PVCs. In addition, Bristol-Myers told the cmte. that on day 1 of treatment 67% of patients receiving 25 mg active drug and 69% receiving 50 mg active drug had a "total abolition of ventricular tachycardia" compared with 13% for placebo. Bristol-Myers is also seeking approval for Enkaid in the treatment of malignant arrhythmias and supraventricular arrhythmias, as well as symptomatic ventricular arrhythmias. The advisory cmte. agreed, however, that the data was insufficient to establish efficacy for any indication other than symptomatic ventricular arrhythmias. In support of a malignant arrhythmia indication, Bristol-Myers presented the results of an "emergency use" trial in which 463 patients were evaluated for efficacy. However, cmte. members expressed some confusion with the data. Peter Kowey, MD., Medical College of Pennsylvania, commented: "We're asked to evaluate a drug in which we only have 18 patients with malignant arrhythmia who have a Holter before and after the drug out of 463 patients and we're given the investigators opinion that the drug is effective in 44% of those 463 patients."The data are very hard to interpret." The cmte. agreed that the data "looks good" regarding the supraventricular arrhythmia indication, but that not enough patients had been studied to support the indication. Summarizing the cmte. consensus, Cmte. Chairman Jeffrey Borer, MD., New York Hospital-Cornell Medical Center, said: "I think the issue is just one of numbers. We're presented with data on 19 patients with a follow up and it seemed a somewhat small number on which to base an approval. But, everyone agrees that it looks awfully good." Reporting on the common side-effects seen with encainide, Bristol-Myers told the cmte. that "at very high doses approximately one quarter of the patients complained of blurred vision or dizziness." At more modest doses, the firm added, "this is not a terribly common phenomenon."
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