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EPO Decision T 0043/18 Confirms That A Higher Level Of Purity May Be Novel

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Decision T43/18 confirms that the European Patent Office (EPO) may acknowledge the novelty of a purity level of a chemical compound (or a composition comprising a chemical compound) in view of prior art disclosing the same compound (or composition) having a lower purity level. The main patentability hurdle for claims having a purity level as the exclusive distinguishing feature in view of the prior art then shifts from novelty to inventive step.


Decision T43/18 consolidates recent decision T1085/13, which overruled the seminal decision T990/06 on claims directed to a chemical compound (or a composition comprising a chemical compound) and reciting a specific degree of purity, be it chemical purity, diastereoselective purity, or enantioselective purity.

In the overturned decision T990/96, the Board of Appeal had taken the view that a given purity level in a claim cannot be accepted as a new element distinguishing the claimed subject matter from the state of the art. In that decision, the Board stated that:

“It is common practice for a person skilled in the art of preparative organic chemistry to (further) purify a compound obtained in a particular chemical manufacturing process according to the prevailing needs and requirements. Since, as a rule, conventional methods for the purification of low molecular organic compounds are within his common general knowledge, a document disclosing a low molecular chemical compound and its manufacture makes normally available this compound to the public in the sense of Article 54 EPC in all desired grades of purity.”

(See T990/96, Headnote 1, and Reasons 7). The Board continued, “[i]f a party alleges that this general rule would not be applicable in a particular case, then the burden of proving the existence of such an exceptional situation, e.g. of a situation where all prior attempts to achieve a particular degree of purity by conventional purification processes have failed, lies with the party who alleges such a situation.” (See T990/96, Headnote 2, and Reasons 8).

Based on this approach, which was followed also by decisions T728/98 and T803/01, the burden of proof appeared to weigh heavy on the applicant’s shoulders, who had to provide evidence that conventional purification methods (such as recrystallization, distillation, chromatography, etc.) could not achieve the claimed purity level. In case T803/01, in the Board’s view, each and every purification method, provided it was "conventional" but regardless of the extent of purification sought, was presumed to be automatically available to the public, in a fully enabling way, and thus made any disclosure describing the compound an effective novelty-destroying disclosure.

In the first-instance proceedings which led to new decision T43/18, both the Proprietor and the Opposition Division (OD) submitted arguments essentially relying on decision T 990/96. In response to the Proprietor, who had argued that HPLC was not a feasible technology to produce commercially relevant amounts of product with the claimed purity degree, the OD had stated that:

“The decisive point to be demonstrated by the proprietor in order to benefit from the exceptional situation outlined in T 990/96 is to convincingly demonstrate that the claimed purity was not accessible at the effective date of the patent by conventional methods for purifying an API [Active Pharmaceutical Ingredient]. The relevant criterion in the opinion of the OD is not the feasibility of a production on an industrial scale satisfying all commercial and economic needs, but the [mere] suitability for the manufacture of sample quantities. Therefore, [the] exceptional situation referred to in T990/96 is not applicable to the claims on file, [and] a skilled person at the effective date of the patent would have been enabled to further purify the [product] disclosed in [the prior art]” (emphasis added).

Hence, the OD had decided that certain prior art documents disclosed the claimed compound in all degrees of purity, and were thus novelty destroying documents despite the lack of disclosure of the content of impurity.

In T43/18, however, the Board does not share the opinion of the OD and explicitly refers to decision T1085/13, i.e., the decision which overturned T990/96. The Board notes that in both cases, the subject matter is claimed in a similar manner, i.e., “a compound A having a purity of P% and containing less than [amount, for example in % or in ppm] of a specific impurity X” and further expresses its agreement with the rationale developed in T1085/13. In particular, the Board consolidates the view, already expressed by T1085/13, that T996/90 is not consistent with the case law of the Enlarged Board of Appeal (EBoA), specifically with respect to decision G2/10 (reasons, 4.7) stating that “the overriding principle for any amendment to be allowable under Article 123(2) EPC is that the subject matter of an amended claim must be at least implicitly disclosed to the skilled person, using common general knowledge, in the application as filed” and decision G1/03 (reasons, 4.6), stating that “the European Patent System must be consistent and the concept of disclosure must be the same for the purposes of Articles 54 [novelty], 87 [priority] and 123 [added subject matter] EPC."

It follows that in order to conclude that a purity claim lacks novelty, “there must be at least an implicit disclosure in the state of the art of the subject matter falling within the claimed scope.” “Such a claim, however, does not lack novelty if the disclosure of the prior art needs to be supplemented, for example by suitable (further) purification methods allowing the skilled person to arrive at the claimed subject matter.” “The question of whether such (further) purification methods for the prior-art compound are within the common general knowledge of those skilled in the art and, if applied, would result in the claimed purity, is not relevant to novelty, but is rather a matter to be considered in the assessment of inventive step.” Accordingly, common general knowledge can be used to appreciate how the skilled person understands a disclosure, but not to supplement it.

This consistency in the concept of disclosure as defined in the European Patent Convention is a laudable goal for ensuring legal certainty, and also appears timely in view of the changes made to the Guidelines of Examination of the EPO with respect to the criteria for assessing the novelty of “selection inventions” since a purity claim can be seen as a selection invention. (See Version of November 1, 2019, Part G-VI, 8 with track changes and corresponding Part G-VI, 8 of the Guidelines currently in force). The Guidelines state that “a selected sub-range has to be narrow compared to the known range” (first criterion), “[and] sufficiently far removed from any specific examples disclosed in the prior art and from the end-points of the known range” (second criterion). According to the (third, now removed) previous criterion for assessing the novelty of selection inventions, the sub-range further needed to stem from a (non-arbitrary) “purposive selection” and thereby be supported by a technical effect associated to such a selection. This third criterion was abandoned because it was considered to be a question of inventive step rather than novelty in the majority of the recent jurisprudence (T0261/15, T1233/05, T230/07). In other words, decision T43/18 appears to comfort a will of applying the same novelty criteria to selection inventions as to any other type of invention.

Referring back to the concept of disclosure unifying Articles 54 (novelty), 87 (priority) and 123 EPC (amendments), under the “gold standard” for assessing compliance with Art. 123(2) EPC (added subject matter), it is clearly not allowable to divide up a generic term into sub-constituents and form new amendments on these conceptual parts. Correspondingly, if a prior art broad range of degrees of purity were to be conceptually split up into subranges for assessing novelty under Art. 54 EPC, a selection invention corresponding to a selected subrange would have no chance to be novel, because the (purportedly) disclosed infinitesimal units resulting from the conceptual splitting of the prior art range would take away the novelty of any subrange selection invention. Interestingly enough, such a concept has however recently been somewhat undermined with respect to Art. 87 EPC (priority) by the breach-opening decision of the Enlarged Board of Appeal G1/15 on partial priorities, which allows dividing up a generic term or broad range into sub-constituents having different effective dates.

The burden of proof shifting from novelty to inventive step may appear to be patentee-friendly at first sight, but may still be quite heavy, because the applicant has still to prove that what is hidden (novel) is not obvious (and therefore inventive). Ideally, applicants should be as specific as possible with respect to the claimed purity degree, to the content of impurity(ies), and to the analytic methods used to determine them (e.g., “a compound at least 98.5% pure and containing less than 0.3% of impurity, as determined by HPLC analysis”). Moreover, applicants could for example lower the bar of the inventive step hurdle by including experimental data in the application at the filing date illustrating the failure of routine purification available at the filing date (or at the priority date, if any).

The main takeaway from new decision T43/18 is that purity should not be overlooked as a source of inventions, considering how it could lengthen the patent life of a pioneering invention directed to a chemical compound, in theory even many years after the filing date of the pioneering invention. Not only the pharmaceutical sector, often aiming at ever-increasing purities, is concerned, but also other industrial fields where so-called “impurities” may in contrast sometimes turn out to be essential in bringing a surprising technical effect, as supported, for example, by T142/06, in which the content of chlorine ion of the claimed latex was deemed to be an essential feature of the claimed latex, since only latexes having this low level of chlorine ions enabled the production of films having the desired oxygen barrier and boil blushing properties.