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Drug metabolites can now be patented

HOUSTON Bristol-Myers Squibb Company unveiled both a scientific achievement and a patent strategy that, if used by other drug companies, could delay introduction of cheaper generic versions of hundreds of patented drugs. Typically, after patents expire and generic versions of a drug become available, most drugs lose up to 80% of sales during the first year they face generic competition, according to Barbara Ryan, a drug industry analyst with Deutsche Banc Alex Brown. US patents on drugs with sal

By | November 29, 2000

HOUSTON Bristol-Myers Squibb Company unveiled both a scientific achievement and a patent strategy that, if used by other drug companies, could delay introduction of cheaper generic versions of hundreds of patented drugs. Typically, after patents expire and generic versions of a drug become available, most drugs lose up to 80% of sales during the first year they face generic competition, according to Barbara Ryan, a drug industry analyst with Deutsche Banc Alex Brown. US patents on drugs with sales approaching $20 billion annually will expire over the next five years.

The Bristol-Myers Squibb (BMS) strategy was to identify the pharmacologically active metabolites produced by patients taking the widely used anti-anxiety medication BuSpar (buspirone HCl). The scientific achievement was to identify a metabolite, 6-hydroxybuspirone, which is produced by patients taking buspirone. Previously, no significant anti-anxiety activity was ever detected for 6-hydroxybuspirone. In consequence, dosing of buspirone was considered optimised when its metabolism by the patient was minimised. The invention claimed in the new patent is the discovery that 6-hydroxybuspirone does exhibit strong anti-anxiety activity and is largely responsible for the onset of therapeutic relief. This means buspirone dosing instructions should be changed to conditions favouring enzymatic production of 6-hydroxybuspirone.

Darlene Jody, vice president, Neurosciences, Infectious Disease and Dermatology Medical Affairs for BMS said, "We believe this knowledge can be translated into even greater relief for patients currently taking BuSpar and, equally important, used to treat many patients with anxiety disorder who have previously been unresponsive to the former method of administration of the medicine."

In some ways, the concept of patenting a patient's own metabolite is philosophically akin to the patenting of human genes.

The BMS patent (US 6,150,365), which describes the optimal use of buspirone to produce the 6-hydroxybuspirone metabolite, was issued one day before the expiration of the firm's patent on BuSpar. In compliance with federal regulations, BMS has listed its new patent in the US Food and Drug Administration's (FDA) Approved Drug Products with Therapeutic Equivalence Evaluations, commonly known as the Orange Book. Because of this, the FDA cannot approve any generic manufacturer's request for permission to produce a generic BuSpar equivalent until 45 days after the manufacturer notifies BMS. If BMS files a patent infringement action against the generic manufacturer within this period, then the FDA could be blocked from granting approval for the generic request for up to 30 months.

So for as much as 30 months, BMS can continue to be the sole marketer of the lucrative drug. Last year BuSpar had sales of around $750 million. In contrast, the nine firms planning to introduce generic BuSpar equivalents suffer financially. For example, Watson Pharmaceuticals, which had planned to rapidly introduce a generic version of BuSpar later this year, anticipates loss of revenues for the fourth quarter 2000 of $18-20 million and for the next fiscal year of $38-40 million.

What's next? "We are currently evaluating the situation and the possible actions available to us," commented Allen Chao, Watson's Chief Executive Officer. "We are concerned that BMS's actions have caused a delay in the introduction of a lower cost generic alternative to BuSpar.

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