Generic Lipitor Is All In The Crystal Forms

Lipitor's got generic competition... at least in Canada. Reuters Health is reporting that three companies-Apotex, Teva, and Watson Pharmaceutical- have been authorized to distribute their generic cholesterol-battling wares in the U.S.'s neighbor to the north, where brand-name Lipitor last year enjoyed annual sales just over $1 billion. Pfizer says it plans to launch its own generic. It's a story that will get many pharma-watchers thinking about November 2011. That's when Lipitor, the #1 drug in the world in terms of sales, loses its marketing exclusivity in the U.S., making it possible for still more generics to get a piece of that pie. What's interesting from a chemical standpoint is how Apotex told Reuters it was able to find a loophole in Pfizer's patents. The company says it developed its own crystal form of Lipitor, which they're selling under the name of Apo-Atorvastatin. The active ingredient in Lipitor is a molecule by the name of atorvastatin calcium. Here is a patent filed in 2001 from Teva for Atorvastatin hemi-calcium form VII. It has a decent discussion of the different crystal forms of atorvastatin known at the time and the pros and cons of their different properties. The crystal form strategy is nothing new, as C&EN's Ann Thayer wrote back in 2007.
Drug developers also want to identify and characterize as many [crystalline] forms of their proprietary compounds as possible. Beyond offering choices for optimal physical properties, each form may be patentable. Drug companies usually file patents on all the different forms during development. Thus, when initial patents on the compound itself expire, they can conceivably extend a product's life by moving to another form. In turn, generic drugmakers will target unprotected forms to avoid patent infringement. Nevertheless, high-profile lawsuits around GlaxoSmithKline's Zantac and Paxil and Bristol-Myers Squibb's cefadroxil have hinged on solid-form issues.
Read the entire article to learn more about the importance of different crystalline forms in drug development. Still want more? Here's a particularly acrimonious tale about different forms of aspirin.

Author: Carmen Drahl

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