The FDA and its clinical advisors have concluded that clinical testing for QT prolongation should be required for all new drugs, even though it's clear that the measure is not a particularly good surrogate for the risk of developing life-threatening cardiac arrhythmia, potentially leading to difficult choices on whether to continue or abandon a drug.
Last week, the agency's Cardiovascular and Renal Drugs Advisory Committee endorsed FDA's suggestion that QT prolongation testing should be required for all new drugs. In its briefing documents for the panel, the agency noted that no class of pharmaceutical agents is exempt from the problem of cardiac arrhythmia, "which spans drug classes as diverse as antibiotics, anti-psychotics, and antihistamines."
But even though the committee was united in calling for QT testing, members made it clear that existing test methods do not yield clear results, there is no consensus about the best way to interpret QT data, and a great deal more fundamental research should be done to come up with better ways of testing for arrhythmia and interpreting the results.
The advisory committee discussed the broad issue of QT trials as it reviewed QT prolongation issues associated with Levitra vardenafil from partners Bayer AG (FSE:BAYG; BAY, Leverkusen, Germany) and GlaxoSmithKline plc (LSE:GSK; GSK, London, U.K.), and UroXatral from Sanofi-Synthelabo S.A. (Euronext:SNYNF; SNY, Paris, France). Levitra is an oral selective phosphodiesterase-5 (PDE-5) inhibitor to treat erectile dysfunction. UroXatral is SNYNF's once daily formulation of its alfuzosin uroselective alpha1-blocker to treat benign prostatic hyperplasia.
Levitra and UroXatral received FDA approvable letters in July 2002 and October 2001, respectively, which cited uncertainty about their effects on QT intervals as barriers to final approval. The sponsors conducted new studies to characterize QT effects.
The panel voted 8-1, with three abstentions, that the data demonstrate that Levitra is not
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