Markowitz says the drug has modest potency, but is undergoing a trial in combination with interferon and ribavirin that may show better results.

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"This means that drug developers have had to modify toxins to retain their potency and make them safe for drug use, " said Dr Casewell.

BBC: Snake venom may be 'drug source'

Until April 2010 it was considered a "legal high", but given its potency and powerful side effects the drug was reclassified.

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One worry was that the mechanism behind the drug was--and is--murky, since free radicals alone can't account for its potency.

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