Teva has seen several claims in patents protecting its innovator multiple sclerosis (MS) drug Copaxone (glatiramer acetate) knocked down by a US appeals court. The ruling means that Teva could face generic competition for the US$4-billion-a-year drug 16 months earlier than previously expected.

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Teva owned nine patents that protected Copaxone and methods of making it, which were challenged by Mylan and Sandoz. Copaxone is a polymer (sometimes called copolymer-1) that is made up of the amino acids alanine, glutamic acid, lysine and tyrosine in a specific ratio. Because a sample of Copaxone typically consists of a mixture of individual polymer molecules that have differing molecular masses, there are several ways to describe the resulting distribution of molecular mass values.

It was this that the challenge was based on; that is, the description of the molecular mass of Copaxone in some of the claims was ambiguous. For some claims, Teva had described molecular mass based on how many molecules in a sample have molecular masses that fall within a set range, such as “copolymer-1 having over 75% of its mole fraction within the molecular weight range from about 2 kDa to about 20 kDa”. And the court said this language was not ambiguous.

But for other claims, Teva had used the wording “copolymer-1 having a molecular weight of about 5 to 9 kDa”. The court said this wording was ambiguous because the average molecular mass could be calculated in several ways, such as the arithmetic mean, the molecular mass of the most abundant molecule in the sample or the mass average molecular mass, and these measurements can each have different values for a typical polymer.

Although Copaxone still has patent protection based on the non-ambiguous claims until 2014, the longest-lasting patent that was due to expire in 2015 (US 5800808) has been lost, meaning that generic competition could begin in 2014. However, the US Food and Drug Administration has not yet approved generic versions of glatiramer acetate. In addition, Teva is hoping to receive regulatory approval for its alternative form of Copaxone (a higher dose with fewer injections), which is anticipated to have patent protection until 2030.

The requirement of a detailed description of the molecular mass of Copaxone in order for the claims to be valid in the current case was consistent with the outcome of a recent case in the United Kingdom. In that case, Teva's claims to Copaxone described the number of molecules in a sample that had molecular masses within a set range, and these claims were found to be non-ambiguous.