Many patent owners are interested in trying to draft a single patent application that will serve them in several countries. This is ambitious, since there are many differences between various countries’ patent systems, but perhaps not impossible. The patent drafter just needs to be aware of and try to balance all the different requirements in the single patent application. This series of articles endeavors to outline some important considerations when drafting a single patent application for several major countries and regions.

In our first article (available here), we reviewed the grace period provisions in the U.S., Korea, China, and the European Patent Office (“EPO”). Since waiting for clinical trial data before filing a patent application is not necessarily advisable, in this article, we will look at how much data should be included on filing.


Data are primarily required to support the requirements of sufficiency (Article 83 EPC) and inventive step (Article 56 EPC). In recent years, the EPO has applied the concept of “plausibility” when assessing both sufficiency and inventive step. The concept of plausibility has arisen from case law as a response to overly broad claims and to prevent speculative claiming. This is particularly relevant when the invention relates to a new therapeutic effect: is it plausible from the as-filed application that the therapeutic effect can be achieved?

As established in our earlier article, the absence of any grace period provisions at the EPO means that applications must normally be filed before any clinical trial data is available, since clinical trial protocols are publicly available. Filing with no data at all is highly likely to result in lack of sufficiency and lack of inventive step objections. So, how are applicants to know how much data to include on filing?

A simple rule of thumb is that the amount of data generally required is inversely proportional to the maturity and predictability of the technical field. It is also important to keep in mind the breadth of the desired claims, as broader claims will (usually) require more data to show an inventive step across their scope. In general, however, it is usually acceptable for applications to be filed with “proof of concept” style data to meet the (relatively low) sufficiency threshold and to establish that the technical effect is plausible. Additional data can then be filed during prosecution if there is a concern that the data are not adequate to show an inventive step across the scope of the claim.

It is important to note that, while supplementary data can normally be filed during prosecution to counteract inventive step objections, late-filed data cannot be submitted to address a lack of sufficiency objection or to demonstrate that a technical effect is plausible. If the alleged technical effect is not considered plausible from the information in the as-filed application, the EPO may refuse to consider supplementary data in support of an inventive step (as seen in Board of Appeal Decision T 0488/16).

While the EPO will accept all forms of data, it may be worthwhile considering how this should be presented when drafting an application. In particular, correcting printing and formatting errors is not necessarily trivial at the EPO. This can be a problem if key data are shown in, e.g. a photograph of an assay test plate, since reproducibility problems are common and fine detail is often lost. We therefore recommend that, if key results are to be presented in the figures, the same data are presented in another format in the body of the application.

United States

In the U.S., data are generally needed for chemical and pharmaceutical patents at the time of filing to satisfy requirements under 35 U.S.C. § 112 (a). 35 U.S.C. § 112 (a) recites:

The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention.

(Emphasis added)

The written description and enablement requirements of 35 U.S.C. § 112 (a) are separate. Ariad Pharmaceuticals v. Eli Lilly, 598 F.3d 1336 (Fed. Cir. 2010) (en banc). First, written description requires an inventor to describe the invention in sufficient detail so that one of ordinary skill in the art can reasonably conclude the inventor had possession of the claimed invention, although the doctrine of constructive reduction to practice is still alive. Under the doctrine of constructive reduction to practice, if later testing confirms the hypothesis in the application, a constructive reduction to practice has been achieved as of the filing date of the application. On the other hand, enablement requires an inventor to convey enough information for a person of ordinary skill in the art to make and use the claimed invention without undue experimentation. Again, a theory of constructive reduction to practice might also bolster an enablement case. See Allergan, Inc. v. Sandoz Inc., 796 F.3d 1293 (Fed. Cir. 2015), for an example of a constructive example supporting both written description and enablement of the challenged claims.

Like in the EPO, the amount of data possibly required in the U.S. depends on the breadth of the claims and the maturity and predictability of the technology. Generally, if the breadth of the claims is broader and/or the technology is more unpredictable, more data are required. Enzo Biochem, Inc. v. Gen-Probe Inc., 323 F.3d 956, 963 (Fed. Cir. 2002). Constructive reduction to practice, however, should not be forgotten.

If either requirement is not satisfied at the time of filing, the defect generally, absent ably-argued constructive reduction to practice, cannot be cured by post filed data. But for limited purposes, post filed data may be considered. For example, post filed data may be accepted to support a usefulness asserted in the application or to show a level of ordinary skill in the art at the time of filing (see In re Brana, 51 F.3d 1560, 1567 (Fed. Cir. 1995); In re Hogan, 559 F.2d 595, 602–09 (C.C.P.A. 1977)). The Brana doctrine is consistent with constructive reduction to practice.

Like in the EPO, post filed data are permitted in the U.S. when establishing non-obviousness of the invention. Data are often essential to a showing of unexpected results. And according to the Federal Circuit, a showing of unexpected results may need to be based on evidence, such as an inventor declaration, not an attorney argument or speculation (see In re Mayne, 104 F.3d 1339, 1343-44 (Fed. Cir. 1997)). Accordingly, an inventor may file an affidavit or declaration under 37 CFR § 1.132 presenting evidence in support of patentability.


In Korea, data are generally required for medical or pharmaceutical use patents to satisfy the written description requirement. According to section 42③1 of Korea Patent Law, descriptions in the patent application should be clear and detailed, so that a person of ordinary skill in the art can easily make and use the claimed invention. Also, according to section 42④1 of Korea Patent Law, claims should be supported by written description.

With respect to pharmaceutical use patents, applicant should describe pharmacological effects in the application at the time of filing to support the claimed use. In principal, the pharmacological effects should be supported by clinical study data. However, depending on the invention, animal or in vitro study results can be sufficient (see Korean manual of patent examination (August 10, 2020) at p. 9201).

In that regard, according to the Supreme Court of Korea, because the pharmaceutical field is unpredictable, a person of ordinary skill in the art would not be able to make and use a pharmaceutical invention without experimental data (see Supreme Court case, 2001 HOO 65 (November 30, 2001)). Thus, the Court held that, unless a pharmacological mechanism is clearly known, applicants should include experimental data that support pharmacological effects of the invention or detailed description of such effects enough to substitute the experimental data. Id. If applicant fails to provide such details at the time of filing, post filed data cannot cure the written description defect. Id.

One example of a “written description defect” is illustrated in Supreme Court case, 2000 HOO 3005 (November 30, 2001). In this pharmaceutical case, the application at issue generally includes the claimed compound’s usefulness and how to measure the pharmacological effects, but not experimental data to support the effects. The Supreme Court of Korea held that post filed data of IC50 of the claimed compound is not allowed because this data completes the previous incomplete invention.

Notably, in Korea, post filed data may be submitted to support non-obviousness of the invention, but that is not always the case. Specifically, post filed data may not be accepted to show unexpected effects, if the as-filed application does not include sufficient description of the effects that is qualitatively different or quantitatively significantly different. In a chemical patent case, the Korean Patent Court declined to consider post filed data because the specification did not include such effects (see Patent Court case, 2008 HU 1772 (May 22, 2009)).


Like the EPO, China requires sufficient data to support the requirements of written description and enablement (Article 26 of Chinese Patent Law) and inventive step (Article 22 of Chinese Patent Law). Specifically, Article 26 of Chinese Patent Law mandates that the application shall be “in a manner sufficiently clear and complete so as to enable a person skilled in the relevant field of technology to carry [the invention] out” and that “[t]he claims shall be supported by the [application].” (Emphasis added).

In addition, like in the EPO, the amount of data possibly required in China depends on the breadth of the claims and the maturity and predictability of the technology. In practice, the processor of China National IP Administration (CNIPA), i.e., the State IP Office in China, seems to be generally more restrictive on data support for the claims than the EPO.

Similar to the general practice with the EPO, the U.S., and Korea, post filed data cannot be used in support of written description and enablement. In other words, the post filed data in support of written description and enablement will be rejected as new matter in China. However, post filed data can be used to show unexpected effects in support of the inventive step only if the such effects are disclosed in the as-filed application. In this regard, China’s practice seems to be similar to that in Korea. In a recently published decision, the Supreme People’s Court of China rejected consideration of the post filed data on the unexpected effects in support of the inventive step because the as-filed application did not mention such effects (see Boehringer Ingelheim Pharma Gmbh v. CNIPA (April 15, 2020)).


While the precise data requirements vary across the U.S., China, Korea and the EPO, similar themes are apparent. In particular, while each of these patent offices will generally accept post filed data to support non-obviousness, such data cannot necessarily be filed to meet written description and enablement requirements. It is therefore important when drafting to ensure that the data adequately support the core inventive concept.

It is ideal that once adequate data are available, the drafting process can begin. In our next article in this min-series, we will look at ways of drafting the application to minimize future added subject-matter and patent profanity issues in the U.S., Korea, EPO and China.