K&P's Intellectual Property High Court Decision Report in October, 2013

Sawai Pharmaceutical Co., Ltd. v. Daiichi Sankyo Co., Ltd., Case No. 2012 (Gyo-Ke) 10419 (Decision rendered on October 16, 2013)

Boehringer obtained a patent relating to use of carvedilol in 2004, and the patent was assigned to Daiichi Sankyo. Sawai filed an invalidation trial against the patent before the JPO in 2007, and the JPO admitted Sawai's demand and rendered a decision of invalidation in 2009, followed by Daiichi Sankyo's 1st appeal against the JPO's decision to the IPHC along with a demand for a correction trial before the JPO in 2009. The IPHC remanded the case to the JPO, and the JPO admitted the correction but rendered a decision of invalidation again in 2010, followed by Daiichi Sankyo's 2nd appeal against the JPO's decision to the IPHC in 2010. The IPHC rendered a decision to cancel the JPO's decision in 2012, and the JPO dismissed Sawai's demand in 2012, followed by Sawai's appeal against the JPO's decision to the IPHC in 2012.

Claim 1 of the patent at issue claims as follows:

"A use of carvedilol having the following structure: (snip) for the manufacture of a medicament substantially decreasing mortality resulting from ischemic congestive heart failure in mammals on background therapy with a diuretic, an angiotensin converting enzyme inhibitor and/or digoxin similarly in class II to class IV symptoms, and being administered for 6 months or longer preceded with a challenge period of low-dose carvedilol, wherein carvedilol is used alone or in conjunction with one or more other therapeutic agents selected from the group consisting of an angiotensin converting enzyme inhibitor, a diuretic and a cardiac glycoside".

One of the main issues in this case was the extent of disclosure required in a prior art reference for a medical use invention. The IPHC answered to the issue as follows.

FFirst, having reviewed prior art reference (p.a.r.) 1 in detail, the IPHC found that p.a.r. 1 disclosed a use of carvedilol for the manufacture of a medicament improving hemodynamic parameter of a patient with ischemic congestive heart failure in classes II and III on background therapy with a diuretic, and being administered for 8 weeks preceded with a challenge period of low-dose carvedilol, where carvedilol was used in conjunction with a diuretic. Further, the IPHC found that those skilled in the art would understand that the administration term from several months to more than a year was required for achieving the purpose of improving the life prognosis of a patient with ischemic congestive heart failure, with reference to some p.a.r.s and a well known technique.

On the basis of the above findings, the IPHC decided that those skilled in the art could have easily conceived of the claimed administration term of carvedilol on the basis of p.a.r. 1 in view of the well known technique and the like, and denied the inventive step.

In this connection, during the court proceedings, Daiichi Sankyo asserted that p.a.r. 1 was not credible and did not disclose the completed medical use invention since p.a.r. 1 disclosed experimental data only on a very small number of patients, and conducted no experiment for comparison with the patients to whom a placebo was administered. However, the IPHC rejected the Daiichi Sankyo's assertion by pointing out that it was sufficient as a prior art reference for a medical use invention as long as those skilled in the art could make a reasonable inference that a chemical substance had the medical use as an active ingredient on the basis of the pharmacological test data disclosed therein, and that it was not required that the test data be randomized, large-scale clinical test data which were required for the approval of a drug.

Conclusively, the IPHC upheld Sawai's appeal, and cancelled the JPO's decision.

An appeal to the Supreme Court was filed against this decision, and thus the decision is not final and binding.

As seen from the above decision, the IPHC has clarified that it is sufficient as a prior art reference for a medical use invention as long as those skilled in the art can make a reasonable inference that a chemical substance has the medical use on the basis of any pharmacological test data disclosed therein, and that it is not required that the test data be ones which are required for the approval of a drug. This decision would serve as a useful reference for considering whether or not the extent of disclosure of a cited reference is sufficient as a prior art reference for a medical use invention.