Cancer Research Tech Ltd v Barr Labs Inc

Cancer Research Tech. Ltd. v. Barr Labs., Inc.
2010 U.S. App. LEXIS 23214


Plaintiff Appellant Cancer Research Technology Ltd. ("Cancer Research") owns the '291 patent, relating to a genus of tetrazine derivative compounds and methods for treating cancer.
The '291 patent identifies and characterizes 13 tetrazine derivative compounds, including temozolomide - the active ingredient in the cancer drug Temodar®. The patent also describes the compound mitozolomide as having "particular importance."
Following a period of more than eleven years of prosecution which included the filing of eleven continuing applications by the applicants, the ‘291 patent was finally issued to Cancer Research. Rejection of original claim 31 for lack of utility was responded to by applicants by filing a continuation application and abandoning the rejected application. Cancer Research overcame the utility requirement by arguing that animal data in the original specification sufficed to establish utility in humans.
While the patent was being prosecuted, one of the inventors co-authored several papers reporting animal and human clinical data for the tetrazine derivative compounds including data for mitozolmide, which showed the compound to have little activity against many cancers and even toxic side effects.
Defendants Appellees Barr Laboratories, Inc. and Barr Pharmaceuticals, Inc. ("Barr") filed an Abbreviated New Drug Application (ANDA) with the FDA in an effort to gain approval to market a generic version of Temodar®. In response to Barr's ANDA filing, Cancer Research brought suit against Barr for infringement of the '291 patent over infringement and validity of claim 13 (directed to temozolomide). Barr counterclaimed unenforceability for prosecution laches and inequitable conduct for trial.

Procedural Posture:

The Federal Circuit reversed the decision by the District Court for the District of Delaware holding U.S. Patent No. 5,260,291 unenforceable for prosecution laches and inequitable conduct.


The unreasonable and unexplained delay requirement of the prosecution laches defense includes a finding of prejudice, and an accused infringer must show evidence of intervening rights (either the accused infringer or others invested in, worked on, or used the claimed technology during the period of delay to establish such prejudice).
The District Court erred because it relied solely on its finding of materiality to infer intent with respect to its finding of inequitable conduct.

Critical Analysis:

Barr was entitled under the law to file an ANDA four years after the NDA approval in 2003, but did not do so until 2007. Barr’s ANDA was thus filed more than thirteen years after the issuance of Cancer Research's patent and more than seven years after CR's product was approved. There was no prejudice to Barr or anyone else because there was no evidence that anyone was deterred from entering the market for temozolomide due to the issuance of Cancer Research's patent in 1993 rather than several years earlier. The delay had only limited consequences to Barr and the public.
The majority noted that materiality and intent are separate requirements. Also, intent to deceive cannot be found based on materiality alone. “A court cannot simply infer that an applicant "should have known" the materiality of withheld information and thus intended to deceive the PTO because the applicant knew of the information and the information is material. A district court must find some other evidence that indicates that the applicant appreciated the information's materiality.”
Evidence that an inventor co-authored articles that contradict the disclosure of the '291 patent specification is not enough to establish that the inventor withheld those studies with the intent to deceive the PTO. The majority surmised that it was reasonable (and hence not deceptive) for the inventor to view publication of all the data as important to his career as a scientist without appreciating their potential importance to the patentability of the tetrazine derivatives patent claims.


"Delaying a patentee's monopoly period harms the public by delaying its free use of the patented invention."
The applicant first filed the patent application disclosing temozolomide in 1982. Stalling prosecution for its own business purposes for nearly a decade allowed Cancer Research to obtain a patent which does not expire until 2014 (almost thirty-two years after the first application was filed*).
  • However, the majority noted that "the facts of this case are not likely to be frequently repeated, as patent terms are now measured from effective filing date, . . . subject to only limited extensions provided by statute, not by delaying issuance by refilling."

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