Wednesday, December 14, 2016

AMGEN V. HOSPIRA: “AN ISOLATED . . . ISOFORM” IS LIMITED TO ONE, AND DEPENDENT CLAIM TO MULTIPLE ISOFORMS IS INVALID

In Amgen v. Hospira[1], a patent infringement lawsuit (U.S. Patent No. 5,856,298) over the biosimilar version of Amgen’s Epogen (epoetin alfa), the parties disputed the meaning of the term "an isolated ... isoform" in claim 1:
1. An isolated biologically active erythropoietin isoform having a single isoelectric point and having a specific number of sialic acids per molecule, said number selected from the group consisting of 1-14, and said isoform being the product of the expression of an exogenous DNA sequence in a non-human eucaryotic host cell.
8. A composition consisting essentially of two or three erythropoietin isoforms according to claim 1. 
Amgen proposed that "an isolated ... isoform" allows for mixtures of at least one isoform.  Hospira proposed that the language allows for mixtures of only one isoform. 

The District Court (Richard Andrews) first discussed the case law regarding the meaning of the term ‘a’ or ‘an’ in a claim: “That 'a' or 'an' can mean 'one or more' is best described as a rule, rather than merely as a presumption or even a convention. The exceptions to this rule are extremely limited: a patentee must 'evince[] a clear intent' to limit 'a' or 'an' to 'one'. . .  An exception to the general rule that 'a' or 'an' means more than one only arises where the language of the claims themselves, the specification, or the prosecution history necessitate a departure from the rule."

Despite stating that the exceptions to this rule (limiting ‘a’ or ‘an’ to only one) are extremely limited, the District Court found that the exception applied “because the plain language evinces a clear intent to claim only one isoform. The claim language reads ‘an isolated ... isoform.’ Plaintiff's reading would render the word ‘isolated’ superfluous. Plaintiff's reading would equate the phrase ‘an isolated .. . isoform’ with ‘an isoform.’”  The District Court further emphasized that Claim 1 was amended during prosecution to read "[a]n isolated ... isoform."  The purpose of the amendment was "to further clarify that an erythropoietin isoform represents a homogeneous preparation."

After finding that Claim 1 requires only one isoform, the District Court found Claim 8 to be invalid since it contradicts Claim 1 's limitation that the isoform is "isolated." Claim 8 requires a mixture "consisting essentially of two or three" isoforms.  Claim 8 thus improperly narrows Claim 1.

The District Court did not discuss the doctrine of claim differentiation, and how the multiple isoforms of Claim 8 would imply that Claim 1 is not limited to a single isoform. 

The Opinion can be found here:




[1] Amgen v. Hospira, No. 15-cv-839 (D. Del., filed Sept. 18, 2015).

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