T 1608/13 - Clarity vs. Insufficiency

Key points

• The OD has revoked the patent for insufficient disclosure. Does this mean that in appeal, the patentee (appellant) has the burden of proof to show sufficiency of disclosure?
• The Board: " Referring to T 585/92 the respondent [opponent] argued that in appeal, after the Opposition Division had revoked the patent, the burden of proof was shifted to the appellant [patentee] to prove that the decision was wrong. However, the primary aim of appeal proceedings is to review the decision under appeal on the basis of the submissions and requests of the parties. This clearly encompasses the review of the Opposition Division's reasoning, in particular the assessment of the respondent's [opponent's] objections considered in the decision. If the reasoning as such is found to be wrong, there cannot be any shift of the burden of proof on the substance. " 
• The OD has conflated clarity and sufficiency, according to the Board. The parties did not dispute that there was a variability in the measurement of the sieving coefficient recited in claim 1.  
• " Clarity [] and sufficiency of disclosure [] are two distinct requirements of the EPC, as reaffirmed in recent case law []. In the present case, the technical problem which the invention aims to solve is how to improve the effectiveness of a blood treatment by providing a membrane [of product claim 1]. The Board does not see how [] a potential lack of clarity deriving from the claim definition of the sieving coefficient in the presence of whole blood could have a major impact on implementing a membrane which solves that specific problem. Hence, using the wording of T 608/07, with which the Board concurs, such a potential lack of clarity would not deprive the skilled person of the promise of the invention, and would not result in insufficiency of disclosure. As far as lack of clarity is concerned, it is not a ground for opposition." 

EPO T 1608/13 - link

The membrane according to the invention is characterised by parameters expressing its permeability for molecules of a certain molecular weight, in the presence of whole blood and water respectively.

3. In the impugned decision, the Opposition Division held that the invention as defined in claim 1 of the patent as granted was not sufficiently disclosed, mainly for two reasons (point 3 of the reasons): the patent did not provide sufficient information to enable the skilled person to determine the parameters defined in claim 1 and example 1, and the invention could not "be worked over the whole range claimed". The respondent endorsed the Opposition Division's view and provided supporting arguments.

3.1 Referring to T 585/92 the respondent argued that in appeal, after the Opposition Division had revoked the patent, the burden of proof was shifted to the appellant to prove that the decision was wrong. However, the primary aim of appeal proceedings is to review the decision under appeal on the basis of the submissions and requests of the parties. This clearly encompasses the review of the Opposition Division's reasoning, in particular the assessment of the respondent's objections considered in the decision. If the reasoning as such is found to be wrong, there cannot be any shift of the burden of proof on the substance. As regards the latter, it is established jurisprudence that a successful objection of lack of sufficiency presupposes that there are serious doubts substantiated by verifiable facts (T 967/09 and other cases cited in Case Law of the Boards of Appeal of the European Patent Office, 8th edition 2016, III.G.5.5.2.2). It is primarily the respondent's duty to provide such facts in support of its objections.

3.2 As far as determining the parameters is concerned, the respondent's arguments relate to the defined sieving coefficients, in the presence of whole blood and water respectively. The nominal cut-off has been explicitly defined in terms of a sieving coefficient of 0.1.

The description of the patent (paragraph [0027]) provides a definition of a sieving coefficient of a membrane, i.e. the ratio of the concentration of a specific molecule in the filtrate to the concentration in the feed. The higher the sieving coefficient, the higher the membrane's permeability to a given molecule. In view of the definition in the patent, the claimed membrane should be relatively permeable to small (or light) molecules with a molecular weight up to 45,000 Dalton in the presence of whole blood and almost impermeable to large (or heavy) molecules with a molecular weight exceeding 200,000 Dalton in the presence of water.

3.3 The Board notes that a patent document is directed to the skilled person, who interprets it in the light of the common general knowledge in the technical field concerned. Consequently, it is not necessary for all the details of the invention to be specifically described in order for a disclosure to be sufficient. In the present case, in the absence of a description in the patent of a specific measuring method for determining the sieving coefficient of a membrane for the separation of toxic mediators from blood by haemofiltration, the skilled person would first look for applicable standards in the field, if present. D7 is a European standard for haemodialysers, haemodiafilters, haemofilters, haemoconcentrators and their extracorporeal circuits. In point 5.4.2 the standard teaches how to measure the sieving coefficient, by using bovine or human plasma as test fluids under certain flow conditions, for haemodiafilters, haemofilters and haemoconcentrators. This is precisely the field of the invention. Hence, the skilled person would turn to D7 and apply its teaching. Whether other methods for carrying out the measurements are available, as argued by the respondent with reference to E4, is not decisive as long as there is no evidence that the results in the specific field of the invention would be contradictory depending on the chosen method. The respondent has not provided any such evidence.

The Board sees no contradiction between the definition of the sieving coefficient in the patent and the one provided in point 5.4.2.2 of D7. The latter definition, according to which the sieving coefficient is provided by twice the concentration of the molecule in the filtrate divided by the sum of the concentrations at the inlet and at the outlet, both at the blood side - or feed, within the meaning of the patent - of a device containing the membrane to be tested, simply takes into account the variations in concentration at the inlet and outlet of the blood side of the device.

The argument that D7 concerns the determination of sieving coefficients of complete filter modules and not hollow fibre membranes - and that for that reason its teaching is not applicable to the membrane according to claim 1 - is not convincing. It has to be noted that the claimed membrane is for the specific use in known blood purification procedures with known filter modules. Hence, the skilled person would provide the filter module with the membrane to be tested as is generally known in the art. The respondent has not provided any evidence that this would not be the case.

The respondent further argued that the molecules to be filtered, the specific way the membrane was arranged in the filter module, and the specific kind of plasma and flow conditions used in accordance with the teaching of D7 would all influence the measurements. Since the patent did not specify any of these variables, the measurements would not be reproducible. The Board notes that the blood purification procedure in which the claimed membrane is to be used is designed to filter out known blood proteins and to take place under known limited ranges of operation in terms of transmembrane pressure, cross-flow rate and temperature. Certainly, as derivable in particular from E3 and D17 referred to by the respondent, within those ranges of operation a certain variability of the sieving coefficient is to be expected. This variability, which is not the one that may be present between any two measurements, but the one resulting from a statistically relevant series of measurements in the known ranges of operation, can result, at most, in a lack of clarity of the subject-matter claimed as far as concerns the end points of the sieving coefficient range in the presence of whole blood and the molecules with the defined molecular weight.

Clarity (Article 84 EPC) and sufficiency of disclosure (Article 83 EPC) are two distinct requirements of the EPC, as reaffirmed in recent case law (T 2290/12, Reasons 3.1, citing T 608/07, Reasons 2.5.2). In the present case, the technical problem which the invention aims to solve is how to improve the effectiveness of a blood treatment by providing a membrane that permits a better separation of toxic mediators in the upper molecular weight range (up to 45,000 Dalton), while better retaining albumin, which has a molecular weight of 68,000 Dalton (paragraph [0013] of the patent). The Board does not see how - and the respondent has not explained why - a potential lack of clarity deriving from the claim definition of the sieving coefficient in the presence of whole blood could have a major impact on implementing a membrane which solves that specific problem. Hence, using the wording of T 608/07, with which the Board concurs, such a potential lack of clarity would not deprive the skilled person of the promise of the invention, and would not result in insufficiency of disclosure. As far as lack of clarity is concerned, it is not a ground for opposition.

3.4 As regards determination of the cut-off of 200,000 Dalton in the presence of water, similar considerations apply. The respondent's arguments focus on the uncertainty arising from the variety of possible test molecules that could be used to determine the cut-off. The appellant referred to D9, a review article concerning the determination of sieving curves for ultrafiltration membranes, which stated that the most commonly employed test molecules were exemplified by dextrans and certain derivatives, particularly because of their availability in widely differing molecular weight ranges (page 1306, second paragraph). The respondent provided no evidence quantifying the alleged influence of the specific test molecules in the determination of the cut-off. In the absence of such evidence there is no reason to believe that the resulting uncertainty could go beyond the domain of clarity and extend to insufficiency of disclosure.

3.5 In conclusion, as far as determination of the sieving coefficients is concerned, the Board concurs with the findings in T 339/97 (Reasons 3.1), in which a membrane with an exclusion limit for molecules between 30,000 and 40,000 Dalton was claimed. In the present case, too, the skilled person is in a position to readily determine the claimed sieving coefficient and cut-off, even if its determination is affected by some variability.

3.6 As regards the question whether the invention could "be worked over the whole range claimed", the respondent first argued that it was not proven that a membrane with the combination of sieving coefficients defined in claim 1 of the patent as granted could be manufactured. The appellant pointed to example 1 of the patent, which constituted an embodiment of the invention and provided clear and unambiguous instructions as to all manufacturing steps and parameters needed by the skilled person to manufacture a membrane according to claim 1. The Board notes that the respondent's arguments do not go beyond mere assertions, since no supporting evidence has been presented. For example, no test results have been provided to show that, following the steps described in example 1, the membrane obtained does not possess the features defined in claim 1. Since no serious doubts substantiated by verifiable facts have been raised by the respondent, the Board concludes that example 1 is a sufficient disclosure of at least one way of carrying out the invention, in compliance with Rule 42(1)(e) EPC. Whether other examples or figures of the patent disclose membranes outside the scope of claim 1 is irrelevant in that respect.

3.7 The respondent further argued that the manufacturing of a membrane depended on so many parameters that it was not feasible, without undue burden, to work out the invention over the whole scope defined in claim 1. The Board notes that for the disclosure to be sufficient the patent is not required to describe every possible membrane falling within the claimed subject-matter. Rather, a certain level of generalisation is the very purpose of the claims. More specifically, there is clearly no need for the patent to disclose methods for manufacturing all possible membranes with all possible combinations of sieving coefficients falling within the scope of claim 1. In the absence of specific evidence in support of the contrary, the Board is convinced that, on the basis of the manufacturing method of example 1, the skilled person would need only routine trial and error to slightly modify some of the parameters of the method and obtain other membranes according to claim 1.

3.8 In conclusion, since none of the respondent's arguments as to insufficiency of disclosure are convincing, the Board considers that the ground for opposition under Article 100(b) EPC does not prejudice the maintenance of the patent as granted. Hence, the impugned decision is to be set aside.

4. Under Article 111(1) EPC, following the examination as to the allowability of the appeal, the Board retains the discretion to remit the case to the department which was responsible for the decision appealed for further prosecution.

Since the impugned decision did not deal with the other grounds for opposition invoked by the respondent, the Board decides to remit the case to the Opposition Division for further prosecution, in order for the parties to have those grounds too possibly considered by two instances.