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Novelty based on the purity of a chemical compound in Europe

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Introduction

In decision T 1085/13 dated 9 November 2018, the Board of Appeal decided that a claim defining a compound as having a certain purity lacks novelty over prior art disclosing the same compound, only if the prior art also, at least implicitly, discloses the claimed purity. This decision contradicted earlier key Board of Appeal decision T 990/96. This article aims to explore the current position of the EPO with respect to the novelty of chemical purity.

 Earlier key decisions

 In decision T 990/96 dated 12 February 1998, the Board of Appeal considered whether a claim to a pharmaceutical compound “whereby the proportion of erythro to threo isomer is 99.5:0.5 or higher” was novel over prior art documents disclosing said pharmaceutical compound but not disclosing the claimed isomeric purity, i.e. whether a purity of 99.5 % or higher rendered the claim novel over the prior art documents. The Board of Appeal reached the decision that a document disclosing a low molecular chemical compound and its method of manufacture made said compound available to the public within the meaning of Article 54 EPC[1] in all grades of purity[2]. The logic behind this decision was that, as a rule, conventional methods for purification of low molecular organic compounds are within the common general knowledge of the skilled person2, i.e. not new.

The Board of Appeal in T 990/96 did accept that exceptional situations may exist, which would justify a different conclusion, e.g. all prior attempts to achieve the claimed degree of purity by conventional methods have failed[3]. However, the Board of Appeal stated that the burden of proving the existence of an “exceptional situation” lay with the party alleging that such a situation exists3. The fact that the prior art fails to explicitly disclose the claimed purity does, in itself, not constitute proof that the claimed purity could not be achieved using conventional methods[4].

In decision T 728/98 dated 12 May 2000, the Board of Appeal followed the jurisprudence of decision T 990/96[5] in finding a claim that required a certain degree of chemical purity of a terfenadine derivative to lack novelty over the prior art. The Board of Appeal in T 728/98 considered that the existence of an “exceptional situation” as described in T 990/96 had not been sufficiently proven by the applicant. From decision T 728/98, it appeared that the burden of proof for proving the existence of an “exceptional situation” was a substantial one, corroboration from a number of sources of the inability to achieve the claimed purity being required[6].

Not all decisions concerning chemical purity followed the jurisprudence of T 990/96. In T 142/09 dated 11 March 2008, for example, the Board of Appeal found the reasoning of T 990/96 to not apply. Here, latex with a chlorine content of 0 to 500 ppm was claimed. The opponent of the patent argued that the chlorine present in the claimed latex was an impurity and that the claim effectively claimed a degree of chemical purity that could not be considered novel. Referring to decision T 990/96, the Board of Appeal in T 142/09 stated that the reasoning of T 990/96 is only applicable where the chemical purity is not an essential feature for the definition of the compound. In the patent in suit, the low level of chlorine ions enabled the production of latex films having desirable oxygen barrier and boil blushing properties. Therefore, the chlorine content could not be considered to be an arbitrary degree of purity but amounted to a purposive selection and an essential feature of the invention[7]. Accordingly, the reasoning of T 990/96 was not considered to apply to the purity claimed in T 142/09[8].

In summary, prior to decision T 1085/13, it was considered that an arbitrary degree of purity of a chemical compound could not render a claim novel, regardless of whether such a degree of purity was explicitly disclosed in the prior art, unless it could be proven that said degree of purity could not be achieved by conventional methods within the common general knowledge of the skilled person: the burden of proof being a substantial one. However, where a degree of chemical purity could be shown to be purposive, rather than an arbitrary selection, the reasoning of T 990/96 did not apply and the degree of chemical purity could render a claim novel over the prior art.

Decision T 1085/13

In decision T 1085/13, the Board of Appeal went against the jurisprudence of decision T 990/96 in determining that a claim defining a compound as having a certain purity lacks novelty over a prior art disclosure disclosing the same compound only if the prior art discloses the claimed purity, at least implicitly, e.g. the method for preparing the compound disclosed in the prior art would inevitably result in the claimed purity[9]. The claim does not lack novelty if the disclosure of the prior art needs to be supplemented, for example by suitable further purification methods, to allow the skilled person to arrive at the claimed purity9. Whether the further purification methods are within the common general knowledge of the skilled person is irrelevant to the question of novelty.

The Board of Appeal in T 1085/13 considered the rationale of T 990/96 to not be in line with Enlarged Board of Appeal decisions G 2/88 and G 2/10[10]. Both G 2/10 and G 2/88 required at least an implicit disclosure of all features of a claim in a prior art disclosure for said prior art disclosure to be novelty destroying for said claim. The skilled person, using his common general knowledge, would understand a feature as implicitly disclosed in a prior art disclosure only if it is the clear and unambiguous consequence, and hence the inevitable result, of what is explicitly disclosed: the common general knowledge of the skilled person can be used to assess how the skilled person would understand the prior art but not to supplement it[11].

However, simply because a claimed chemical purity can be considered novel over the prior art, does not necessarily mean that said claimed chemical purity will lead to allowable subject matter. The question of whether further purification methods are within the common general knowledge of the skilled person is relevant to the assessment of inventive step[12]. To prove inventive step, the applicant will need to demonstrate that the prior art disclosure does not contain any indication of purification techniques, which would prompt the skilled person, using their common general knowledge, to arrive at the claimed chemical purity[13].

Conclusion

This article explains changes to EPO practice concerning the novelty of chemical purity.

Prior to decision T 1085/13, the EPO considered a claim to a chemical compound reciting a specific degree of chemical purity to not be novel over a prior art disclosure of the chemical compound, regardless of whether the claimed degree of chemical purity was disclosed in the prior art disclosure. A degree of chemical purity could only be considered novel over a prior art disclosure if it could be shown to be an essential feature of the invention, or if substantial evidence could be provided that the degree of chemical purity could not be achieved by conventional methods within the common general knowledge of the skilled person.

Now, a claim to a chemical compound reciting a specific degree of chemical purity will be considered novel over any prior art disclosure that does not, at least implicitly, disclose the claimed degree of chemical purity. The question of whether the claimed degree of chemical purity could be achieved using conventional methods is only relevant to inventive step. If the claimed degree of chemical purity is purposive, or if the prior art fails to prompt the skilled person, using their common general knowledge, to arrive at the claimed degree of chemical purity, the claimed degree of chemical purity will be considered inventive.

[1] Article 54 EPC:

(1)An invention shall be considered to be new if it does not form part of the state of the art.

(2)The state of the art shall be held to comprise everything made available to the public by means of a written or oral description, by use, or in any other way, before the date of filing of the European patent application.

(3)Additionally, the content of European patent applications as filed, the dates of filing of which are prior to the date referred to in paragraph 2 and which were published on or after that date, shall be considered as comprised in the state of the art.

(4)Paragraphs 2 and 3 shall not exclude the patentability of any substance or composition, comprised in the state of the art, for use in a method referred to in Article 53(c), provided that its use for any such method is not comprised in the state of the art.

(5) Paragraphs 2 and 3 shall also not exclude the patentability of any substance or composition referred to in paragraph 4 for any specific use in a method referred to in Article 53(c), provided that such use is not comprised in the state of the art.

[2] No. 7 of the reasons for decision T 990/96

[3] No. 8 of the reasons for decision T 990/96

[4] No. 10 of the reasons for decision T 990/96

[5] No. 6.4 of the reasons for decision T 728/98

[6] No. 6.4.2 of the reasons for decision T 728/98

[7] No. 3.29 of the reasons for decision T 142/09

[8] No. 3.30 of the reasons for decision T 142/09

[9] No. 3.7 of the reasons for decision T 1085/13

[10] No. 3.6 in reasons for the decision T 1085/13

[11] No. 3.6.4 in reasons for the decision T 1085/13

[12] No. 3.8 in reasons for the decision T 1085/13

[13] No. 9.7 in reasons for the decision T 1085/13

This article is for informational purposes only and does not constitute legal advice. Please, therefore, get in touch with your usual Forresters Attorney if you need further advice.

If you have any questions about this topic please contact Beth Campbell bcampbell@forresters-ip.com or your usual Forresters contact.