Merck Down to One Short Lived Valid Cubicin Patent

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By Tony Dutra

Nov. 12 —New Link Merck & Co.'s Cubist Pharmaceuticals has only one patent left covering its Cubicin antibiotic, paving the way for a generic version as early as next year, after a Nov. 12 ruling by the U.S. Court of Appeals for the Federal Circuit.

The court affirmed a district court's judgment that invalidated four longest lasting patents related to the drug, the last of which would have given Cubist coverage until 2020. However, only the oldest patent, which expires in June, was left intact.

Hospira Inc., which is planning a generic version, of the drug, challenged the patents.

Eli Lilly developed the drug initially. The four Cubist patents that were found invalid claimed follow-on developments in terms of purity and dosage. The appeals court held that each development was predictable based on earlier work with daptomycin, branded as Cubicin.

Hospira's failed challenge to the remaing patent focused on a mistaken impression of the inventors that was reflected in the original patent application. The appeals court held that the inventors nevertheless “possessed” the claimed invention because the patent claims didn't rely on the mistake.

Invention ‘Possession' Not So Strict

Cubicin is an antibiotic that prevents or treats skin infections caused by certain specific bacteria.

Cubist owns U.S. Patent No. RE39,071, which is a reissue of Lilly's U.S. Patent No. 5,912,226 on the formulation. The four later-filed patents cover either new dosage regimens (Nos. 6,468,967 and 6,852,689) or purified versions (Nos. 8,058,238 and 8,129,342) that Lilly didn't pursue.

Cubist had to defend its reason for seeking reissue: One of the formulation tables in the '071 patent showed that “researchers had previously been mistaken about the precise chemical structure of daptomycin.”

Hospira argued that fixing the formulation either improperly broadened the scope of the relevant patent claims, or else it showed that the written description requirement of 35 U.S.C. §112 was not met—that the inventors didn't “possess” the invention per Ariad Pharm. Inc. v. Eli Lilly & Co., 598 F.3d 1336, 2010 BL 62410, 94 U.S.P.Q.2d 1161 (Fed. Cir. 2010) (en banc) .

The court disagreed on the claim scope argument by distinguishing Bayer v. Dow Agrosciences LLC, 728 F.3d 1324, 108 U.S.P.Q.2d 1071 (Fed. Cir. 2013).

First, Cubist fixed the specification while the Bayer case involved a change in the claim language. Second, Cubist was seeking a claim construction aligned with the correct formulation, while Bayer, in its case, was proposing that the claim be construed in a way that “would be inconsistent with the ‘strong accepted scientific meaning' of the claim language.”

As to Hospira's argument that the inventors lacked possession of the invention, the court said, “It was enough that the specification disclosed relevant identifying characteristics that distinguished daptomycin from other compounds and thus showed that the inventors had possession of daptomycin, even though they may not have had an accurate picture of the entire chemical structure of that compound.”

On this point, the court distinguished In re Wallach, 378 F.3d 1330, 71 U.S.P.Q.2d 1939 (Fed. Cir. 2004). The inventors in Wallach were aware of a small portion of a nucleotide sequence and instead “claimed the entire nucleotide sequence of any DNA molecule that would code for the protein.”

In contrast, “the applicants claimed only what they had produced—the daptomycin molecule—which they identified in several ways,” the court said of this case. “The description of the molecule provided in the specification in this case was far greater than the very limited description of the DNA sequence in the Wallach case, and the claims in this case, unlike those at issue in Wallach, were limited to the compound itself.”

Why Did Lilly Leave Daptomycin for ‘Dead'?

The district court invalidated the asserted dosage and purity patent claims primarily because Lilly's work, combined with other known drug development procedures, rendered them obvious.

For all four patents, Cubist argued that there was a “long-felt need” that Lilly didn't satisfy, giving secondary evidence of the nonobviousness of their inventions. But Lilly had another antibiotic that was highly profitable.

Effectively, Lilly had no incentive to develop daptomycin, the Federal Circuit said. So Lilly's inattention said nothing about whether other procedures for determining the right dosage or purifying the formulation were obvious.

Cubist's main argument as to the dosage patents was that the objective of the later patents was “minimizing skeletal muscle toxicity,” while none of the old documents on the issue mentioned that goal. But the appeals court again deferred to the district court's judgment that that characteristic was inherent in what the prior experts in the field had researched.

Cubist also argued that prior predictions that its dosage-related inventions would be optimal didn't show that the developments were obvious. But the court said that the “extensive laboratory research” underlying those predictions was relevant to the obviousness analysis.

The purification patents failed in addition because they relied on two techniques that were well known in the industry.

Judge William C. Bryson wrote the court's opinion, which was joined by Judges Evan J. Wallach and Todd M. Hughes.

The case was on appeal from the U.S. District Court for the District of Delaware.

William F. Lee of Wilmer Cutler Pickering Hale and Dorr LLP, Boston, represented Cubist. James F. Hurst of Kirkland & Ellis LLP, Chicago, represented Hospira.

To contact the reporter on this story: Tony Dutra in Washington at adutra@bna.com

To contact the editor responsible for this story: Mike Wilczek in Washington at mwilczek@bna.com

Text is at http://www.bloomberglaw.com/public/document/CUBIST_PHARMACEUTICALS_INC_PlaintiffCrossAppellant_v_HOSPIRA_INC_/1.