In the recent post on the approval of generic Combivir -- and the lack of availability of generic Epivir (lamivudine, 3TC), which was both anticipated and likely to be more useful -- I speculated there were several possible causes of this surprising turn of events.

But ultimately I concluded, "In sum, the real reason there's no generic 3TC remains a mystery."

Last week, however, I received a fascinating email from an industry representative, who has asked that I summarize the turn of events from their perspective:

• The Epivir patent in the U.S. expired in May 2010.
• A generic company was granted exclusive rights to market a generic in the U.S. for 6 months. (This is part of patent law.)
• The particular company that was granted exclusivity was not been able to manufacture a product that has met approvability standards by the FDA.
• During the period of exclusivity, furthermore, no other company can market a generic either -- again, patent law in action.

Mystery solved -- and thank you for the clarification.

But I hasten to add that this information was not widely known by HIV/ID specialists, and furthermore not easy to find. One of my colleagues has likened reading rulings on patent law for generics akin to learning English as a second language, a very apt analogy.

Paul Sax is Clinical Director of Infectious Diseases at Brigham and Women's Hospital. His blog HIV and ID Observations is part of Journal Watch, where he is Editor-in-Chief of Journal Watch AIDS Clinical Care.

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