Prior to this decision, Eli Lilly held two US patents that protected Gemzar: US 4,808,614, which claims the chemical compound and a method of using it for treating viral infections, and the later-issued US 5,464,826, which claims a method of using Gemzar to treat cancer. Sun asserted that the '826 patent was invalid because of obviousness-type double patenting over the earlier '614 patent. Obviousness-type double patenting occurs when the claims in a later patent are not patently distinct from claims in an earlier patent that is owned by the same company. The earlier '614 patent discloses the use of a series of compounds that included Gemzar for treating cancer — the patent specification stated that the compounds had “excellent oncolytic activity in standard cancer screens” — but did not claim a method of using the compounds to treat cancer.
Eli Lilly argued that, although the '614 patent disclosed the anticancer activity of Gemzar, it was the antiviral activity that gave the patent “utility” — that is, it allowed the invention to perform a beneficial function — which made the compound patentable. So, in their view, because the utility of the earlier '614 patent was related to antiviral activity, and the utility of the later '826 patent was anticancer activity, the two patents were distinct.
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