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Promising new drugs for pandemic influenza.

VAIL, COLO. -- Much needed help in treating pandemic 2009 H1N1 influenza may be on the way in the form of two promising investigational drugs that could become commercially available within the next several flu seasons.

Favipiravir and laninamivir are in phase III clinical trials abroad, where to date both appear to be performing very well, Dr. Adriana Weinberg said at the conference.

Favipiravir is an oral RNA polymerase inhibitor effective against both influenza A and B as well as other RNA viruses. It is in Phase III testing in Japan. Importantly, it has no cross-resistance with the neuraminidase inhibitors or adamantanes.

Laninamivir is a neuraminidase inhibitor administered only by inhalation. However, the drug has an extremely long half-life such that a single inhalation constitutes an entire course of treatment. Laninamivir is effective against oseltamivir-resistant isolates. It is in phase III trials in Australia, where it is establishing a very favorable safety profile, according to Dr. Weinberg, professor of medicine, pediatrics, and pathology of the University of Colorado, Denver, and medical director of the clinical virology laboratory at University of Colorado Hospital.

Current treatment options for pandemic H1N1 flu are quite limited, so these two new drugs are badly needed, she added.

More than 90% of H1N1 isolates from the 2009 pandemic were resistant to adamantanes.

So basically all that physicians had available early on were the oral neuraminidase inhibitor oseltamivir (Tamiflu) and the inhalation-only formulation of zanamivir (Relenza), another neuraminidase inhibitor.

These were supplemented during the pandemic by intravenous peramivir, a drug that was in Phase III trials but was decreed available for use in critically ill patients as a result of an Emergency Use Authorization. The Emergency Use Authorization was terminated in June 2010.

Peramivir has a resistance profile and efficacy similar to oseltamivir. Thus, its sole advantage is that it can be given intravenously.

The recommended dosing is 6 mg/kg in neonates, 8 mg/kg for infants aged 31-90 days, 10 mg/kg for 91- to 180-day-olds, 12 mg/kg for children aged 1.81 days through 5 years, 10 mg/kg for 6- to 17-year-olds, and 600 mg for patients aged 18 years and older. The infusion is given over 30-60 minutes.

Intravenous zanamivir became available on a compassionate use basis during the pandemic. Unlike peramivir, it is effective against oseltamivir-resistant isolates.

Ribavirin is commercially available for indications other than influenza.

However, it does have in vitro activity against influenza, and although it's not a very good anti-influenza drug by itself, it may have a future in combination therapy for severe pandemic H1N1 disease.

Disclosures: Dr. Weinberg disclosed serving as a consultant to MedImmune, Astellas, GlaxoSmithKline, and Merck.


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Title Annotation:CLINICAL ROUNDS
Author:Jancin, Bruce
Publication:OB GYN News
Date:Oct 1, 2010
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