“Maxacalcitol” Manufacturing Process Patent Case

“Maxacalcitol” Manufacturing Process Patent Case

Subject: equivalent infringement

This case is a groundbreaking infringement case with regard to the doctrine of equivalents (DOE) in Japan. Here, the originator of “Maxacalcitol” (plaintiff) filed a patent infringement suit against several generic manufacturers (defendants) and the decision was rendered in favor of the plaintiff by the Japanese IP High Court. The defendants were found to infringe the process patent owned by the plaintiff under (DOE).

In the pharmaceutical field, patent infringement under the DOE was established under the “ball spline bearing case” where the Supreme Court set forth five requirements to apply the DOE.[1] ¬†Although the Japanese IP High Court has rarely applied the DOE, this case is an exception, and the IP High Court has not only applied the DOE but has also further explained its requirements 1 (non-essential part) and 5 (special circumstance).

Summary of the case

The plaintiff owns a patent for a manufacturing process of vitamin-D-derivatives, including generic name: “Maxacalcitol” (hereinafter: “the present patent”). The defendants’ end product and process is the same as that of the patented manufacturing process except that the plaintiff uses a “cis”-isomer vitamin-D-derivative as the starting material and intermediate, whereas the defendants use its geometric isomer, i.e. a “trans”-isomer of vitamin-D-derivative. The difference of the “trans”-isomer compared to the “cis”-isomer does not have any influence on the manufacturing process according to the present patent. Further, in the last step, to receive the generic (i.e., the identical) molecule, the defendants removed the initial difference of the starting material. The last step, i.e., from the “trans”-isomer into the “cis”-isomer, is an additional step compared to the patented method. The plaintiff argued that the defendants’ manufacturing process infringes the present patent under the DOE.

The main issues were, whether the first and the fifth requirements of the five requirements of the DOE specified by the Supreme Court in the “ball spline bearing case” are satisfied.


The Court focused on requirements 1 and 5 and looked at the following issues:

  1. Requirement 1 (non-essential part): Does the essential part of the invention lie in obtaining an epoxide compound from a starting material having a vitamin-D-structure and then treating the same with a reducing agent as asserted by the plaintiff, or in whether the vitamin-D-structure of the starting material and the intermediate is a “cis”-isomer or a “trans”-isomer as asserted by the defendants?
  2. Requirement 5 (special circumstances): Does the fact that solely a “cis”-isomer vitamin-D-structure is claimed fall under a special circumstance?

Decision of the IP High Court, Grand Panel

(Decision of IP High Court; March 25, 2016)

Regarding the first requirement (non-essential part) of the DOE, the court found that “the essential part of a patent invention lies in a characteristic part constituting a unique technical concept that did not exist in prior art, among the description of patented claims“, and that “since the substantial value of the patented invention must be determined in accordance with the degree of contribution compared with prior art in the relevant technical field, the essential part of a patent invention must be evaluated based on the wording of the claims and the specification, in particular based on comparison with the prior art mentioned in the specification“. Based on that maxim, the IP High Court confirmed the decision of the Tokyo District Court and came to the conclusion that, whether the vitamin-D-structure of the starting material and the intermediate is a “cis”-isomer or a “trans”-isomer is not an essential part of the present invention, and, thus, that the first requirement of the DOE is satisfied.

With respect to the fifth requirement (special circumstances), the court stated that “if a patent owner was unable to easily enforce his/her patent right of a product at issue (such as through injunctive relief) by a mere substitution of a non-essential part of a patent invention, motivation for inventions of the society will be diminished, which is against the purpose of the patent law to contribute to the development of the industry by protecting and promoting innovations as well as social justice and the principle of equity. The doctrine of equivalents is to avoid such a situation, and even if a feature that is outside the scope of patent claims could have been easily conceived at the time of the filing, said fact alone does not constitute the reason to negate the doctrine of equivalents“.


The IP High Court came to the conclusion that the fact that the applicant did not specify a “trans”-isomer of vitamin-D-structure in the claims does not fall under the “special circumstances” of the fifth requirement of the DOE, because it is not objectively and apparently acknowledgeable that the applicant of the present patent at the time of filing had or had not recognized that a “trans”-isomer of vitamin-D-structure would substitute for the starting material. An infringement under the DOE was thus affirmed.

Our comments ¬† The decision in the “Maxacalcitol” case will likely bring clearer guidance for IP strategies when originators consider the possibility of patent infringement suits based on their process, formulation or crystal patent, etc., after the expiration of a substance patent.

[1] The “ball spline bearing case” decision specified the following requirements as the requirements for applying the doctrine of equivalents: 1) non-essential part; 2) replaceability; 3) ease of replacement; 4) ease of conception; 5) special circumstances, such as estoppel. (Decision of the Supreme Court (third petty bench) on case No. 1994(o)1083, February 24, 1998)