Patent laws in many countries impose an onus on patent applicants to act in good faith in dealing with the patent office. For example, in Australia, a patent may be held to be invalid if it is shown that the patent was obtained by fraud, false suggestion, or misrepresentation. In the United States, applicants, inventors and their attorneys have a duty of candour, good faith, and honesty in dealings with the patent office and a patent may be held to be unenforceable if there was inequitable conduct on the part of any of those people in their dealings with the patent office.

In Australia, the full Federal Court revoked a patent directed to a specific form of Warner-Lambert's blockbuster cholesterol lowering drug, Lipitor (Ranbaxy Australia Pty Ltd v Warner-Lambert Co LLC (2008) 77 IPR 449). The court held that data included in the patent specification represented that Warner-Lambert had found that activity of the R form of the drug was about ten times that of the racemate (ie mixture of R and S forms of the drug). Warner-Lambert's attorneys made a similar representation in response to an Examiner's report on the application. However, it turns out that all of the data available to Warner-Lambert showed that the R form of the drug had an activity level that was only about two times greater than the racemate. The court found that the representation that the R form of the drug was ten times greater was material to the patent office's considerations in granting the patent and were false and misleading. The patent was therefore revoked.

The charge of inequitable conduct by patent applicants, inventors or their attorneys is also being increasingly used in the United States to render patents unenforceable. A recent decision of the Delaware District Court (Cancer Research Technology et al. v Barr Laboratories et al., D-Del, Civ. No. 07-457-SLR, January 26, 2010) provides an insight in to the extent of the duty of good faith that is owed to the United States Patent and Trademark Office (USPTO) by patent applicants.

Cancer Research Technology (CRT) was the assignee of a US patent covering the tetrazine compound temozolomide, which is marketed under the name Temodar® for the treatment of brain cancers. A patent application was filed in 1982 and the USPTO initially rejected the application for lack of utility on the grounds that the application did not include data showing the efficacy of the claimed compounds in humans. CRT did not file a substantive response but filed a series of continuation applications over the course of ten years to effectively keep the application alive. The USPTO rejected each continuation application on the same grounds until, finally, in 1993, CRT filed a response in which they argued (based on case law from 1986 and earlier case law cited therein) that they did not need to provide data showing efficacy in humans, and the animal test data already present in the application was sufficient. The application was allowed based on the response.

However, in the period during which the application was being kept alive at the USPTO, one of the inventors published numerous papers on tetrazine derivatives, including papers showing that some of the compounds covered by the claims were inactive. This information was not provided to the USPTO and the applicants continued to pursue broad claims that covered compounds that were known to be inactive. The court held that CRT's patent was unenforceable. In this case, the data showing inactivity was material to patentability and should have been disclosed to the USPTO. This is particularly relevant as the Examiner had rejected CRT's patent claims for lacking utility over their full scope and the material published in the papers appeared to support the Examiner's rejection.

These cases emphasise the importance of inventors and applicants to provide all relevant data to their patent attorneys for the purpose of preparing a patent specification and also whilst their patent applications are pending. Consideration should be given to disclosing to the relevant patent offices any new data, prior art or other matter that is material to the patentability of the invention or in conflict with earlier statements or data made in the specification.

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