An ambiguous term that refers to an indeterminate one of several possibilities may be held to be indefinite rather than simply broad when the claim scope changes dramatically depending on how it is construed. This is especially true for mathematical ranges where the different interpretations lead to fundamentally distinct and disjointed claim scope.
Background / Facts: The patents here relate to the drug Copaxone used in treating multiple sclerosis. The specification details different ways to describe the resulting distribution of molecular weight values in the polymers that make up the claimed invention. In particular, there are several statistical measures of average molecular weight, including the peak average molecular weight (Mp), number average molecular weight (Mn), and weight average molecular weight (Mw). The claims, however, simply define a numerical range for the unqualified term “molecular weight,” without specifying which measure it refers to, Mp, Mw, Mn, or some other measure.
Issue(s): Whether the unqualified term “molecular weight” renders the asserted claims indefinite because it can refer to different measures, including Mp, Mw, and Mn, with significant variations in claim scope depending on which measure is construed.
Holding(s): Yes. “It is undisputed that [the] claims contain an ambiguity because their plain language does not indicate which average molecular weight measure is intended. [The patentee’s] attempt to resolve this ambiguity hinges in part on the prosecution history. But two of its prosecution statements directly contradict each other and render the ambiguity insoluble.” As it turns out, the same indefiniteness rejection was raised in two related applications and the applicant argued that one skilled in the art would clearly recognize that the molecular weight at issue refers to a different one of the disclosed options. The patentee attempted to argue that one of those assertions was a harmless error, but the court was not convinced by the patentee’s contention that “a skilled artisan would discount this statement … because it contains an evident scientific error.” This combined with no clear expert consensus or explicit statement in the specification led the court to conclude that the claims are indefinite.