Parameters and (in)sufficiency of disclosure – T 2009/23

Inclusion of a parameter in an independent claim without a corresponding method of measurement described in the patent does not immediately lead to an issue of lack of clarity and/or lack of sufficiency under EPO practice.  Understandably so – there are different factors at play, such as the type of parameter in question, the significance ascribed to the parameter relative to what is claimed and/or whether the parameter can be reliably measured using one or more known methods, etc.  The common general knowledge of the skilled person is also relevant, of course.

However, the situation becomes rather problematic if an independent claim contains a parameter that is deemed critical to the carrying out of the invention, and the skilled person has no way of reliably measuring the parameter whatsoever.

This was the case in T 2009/23, where a process claim defined the resulting product in terms of a seemingly simple parameter (weight content of a particular class of compounds) that, as it turned out, could not be reliably measured.  Unsurprisingly, the Board of Appeal upheld the decision of the Opposition Division that the claimed invention was not sufficiently disclosed.

Inulin - background

Inulin is a naturally occurring polysaccharide produced by many types of plants.  It is most typically extracted from chicory and is used as a texturiser or stabiliser in food products.  It is also a prebiotic. 

Inulin is made up of fructose (F) units and often includes a terminal glucose (G) unit.  The units are linked in a specific fashion.

Inulin can thus be represented as:

GF(n); or

F(m);

wherein n and m are integers denoting the number of fructose units in the chain.

This is also the notation used in the patent in suit in T 2009/23 and throughout this post.

For example, a GF3 inulin compound could be represented as:

glucose – fructose – fructose – fructose

Depending on the plant source, the number of fructose units can be anything between 2 and 60.

The decision

This was an appeal from the decision of the Opposition Division to revoke EP 3331921 for lack of sufficiency of disclosure.

Claim 1 of auxiliary request IX before the Board defined a process for the preparation of an inulin product, wherein raw inulin (native chicory inulin) was subjected to enzymatic hydrolysis using an endo-inulinase to obtain the inulin product characterized by, inter alia, a specific content of GF(n≥10) inulin compounds.

Of particular relevance to the decision are inulin compounds having a ‘degree of polymerisation’ of 11 or more, i.e. those denoted as:

GF(n≥10) [see above re the claimed process] and F(m≥11)

Hydrolysis of inulin yields multiple fractions of compounds of varying chain length.  Thus, to prepare the claimed product, the skilled person should be able to control the process so as to obtain a particular content of GF(n≥10).  To control the process, the skilled person needs to have at their disposal an adequate method for analysing the hydrolysed inulin product, in particular, with respect to the content of GF(n≥10).

The specification of the patent in suit did not describe the method for determining the content of GF(n≥10) as such. 

The patent mentioned two methods: (i) high-temperature capillary gas chromatography (‘HGC’) with particular measurement conditions, as a “suitable known method of determining the amounts of the compounds GF2 , F3 , and F4” and (ii) High-Performance Anion-Exchange Chromatography (‘HPAEC’) as a “suitable known way of determining Fi”.

In principle, a mixture of compounds having a degree of polymerisation of 11 or more, i.e. GF(n≥10) and F(m≥11), could be subjected to a measurement under any of the two methods.  It was common ground between the parties that the skilled person would be aware of the two methods and their application.

In practice, however, the two methods would not separate GF(n) from F(m) compounds across the entire range of n and m values.

There was evidence on file indicating that the ‘HGC’ method was suitable for separate quantification of GF(n) from F(m) only up to degree of polymerisation of 9, i.e. for n=8 and m=9.  For inulin compounds of longer chains (degree of polymerisation from 10 to 12, i.e. encompassing GF(n≥10)), the integrated values for the peaks covering the longer chain compounds were not reliable due to a significant baseline shift.

Similarly, there was evidence on file that the ‘HPAEC’ method would separate fractions of inulin into single peaks but would not do so over the entire range of n and m values for GF(n) and F(m)  – it was only suitable for distinguishing between the fractions in the ‘lower’ region, i.e. for shorter chains.

The only example in the patent referred to the content of “GF(n≥10) and/or F(m≥11)” (rather than that of GF(n≥10)) in the hydrolysed product, as measured by the ‘HGC’ method.

In view of the evidence on file, the Board concluded that the content given in the example of the patent is that of “GF(n≥10) and F(m≥11)”.

The patentee argued that the content of F(m≥11) would be negligible compared to that of GF(n≥10).  This would mean that the content of “GF(n≥10) and F(m≥11)” is necessarily equal to that of GF(n≥10) as defined in the context of the claimed process.

There was no information on this point in the patent itself.  The patentee tried to rely on two documents – the first stating that “in native inulins the Fm fraction is to be considered as negligible", the second being an experimental report filed on appeal and showing the content of F2-9, GF2-8 and the combined content of F10 and GF9 as measured by the ‘HGC’ method in hydrolysed inulin.  There was no mention of the content of GF(n≥10) or F(m≥11) in the report.  The patentee argued that the data shows a trend in the way the endo-inulinase hydrolyses native inulin, which trend suggests that the formation of F(m≥11) would be negligible.

The Board was not convinced by this argumentation.  The first document relied upon by the patentee referred to the content of Fm in “native inulins” rather than those that have been subjected to hydrolysis or other processing.  The experimental report could not help either.  Firstly, it lacked the measurement of the content of GF(n≥10) and F(m≥11) products, so it could not directly demonstrate anything relating to those compounds.  Secondly, the particular experiments carried out after filing could not support what the skilled person would infer from the patent at the filing date (which is relevant to sufficiency of disclosure), but even if they did, they would not imply that no or only little formation of F(m≥11) took place.

The patentee essentially argued that the hydrolysis reaction mainly produces F3 and F4 compounds, while reduced formation of F5 and F6, and practically no F8 formation is observed.  The Board noted that the formation of those compounds is “already observed at an early stage” of hydrolysis, and that this could imply the formation of “additional” F(m≥11).

Although not explicitly mentioned in the decision, it seems that the hydrolysis reaction carried out in the experimental report was much shorter than in the patent (5 hours in the report vs. 20 hours in the patent).

Finally, the patentee’s argument that a commercially available endo-inulinase would only result in the generation of short Fm chains was dismissed as a mere allegation, not supported by evidence.

In summary, the Board stated that the sole methods available to the skilled person were those that measured the combined content of GF(n≥10) and F(m≥11), and that there was no evidence on file showing that the content of “GF(n≥10) and F(m≥11)” is necessarily equal to that of GF(n≥10) for hydrolysed inulins prepared according to the claimed process.

Therefore, no method for reliably measuring the content of GF(n≥10) was available to the skilled person at the filing date.

With this in mind, the Board concluded that “the skilled person would be left in the dark as to when to stop the hydrolysis reaction in order to adjust the amount of GF(n≥10) over the entire breadth of claim 1”.  The claimed invention was thus found to be insufficiently disclosed.

Lack of clarity?

The patentee also tried to argue that the issue of insufficiency is really a question of the accuracy of the measuring method, i.e. in fact a lack of clarity objection.  The relevant measuring method may result in differing values for GF(n≥10) (due to the presence of negligible amounts of F(m≥11), as argued by the patentee), but this would merely be an inadmissible matter of lack of clarity. 

The Board rejected the patentee’s argument.  Based on the earlier reasoning, the content of GF(n≥10) and, separately, F(m≥11) could not be reliably determined, so the argument that differing values of GF(n≥10) are obtained was not tenable. 

The patentee’s argument also relied on a specific line of EPO case law according to which “for concluding an insufficiency arising out of ambiguity, it is not enough to show that an ambiguity exists, e.g. at the edges of the claims, but it will normally be necessary to show that the ambiguity deprives the person skilled in the art of the promise of the invention”.  Those decisions relate to claims containing unclear parameters wherein specific values of those parameters are essential to solving the technical problem underlying a patent/patent application, and wherein no measurement conditions for the parameters are indicated. 

The Board found this to be irrelevant to the matter at hand, and instead endorsed the principles developed in T 1845/14, wherein it was held that “[i]n case of an unclear parameter defined in a claim whose values required in the claim are indicated in the specification to be essential to solving the problem underlying the patent at issue, the ability of the skilled person to solve that problem by reproducing what is claimed is not a suitable criterion for assessing sufficiency of disclosure when the problem or an effect derivable from it are not explicitly or implicitly part of the definition of the claimed subject-matter”. 

The Board also distinguished between (i) the absence of a reliable measuring method, as in the present case, and (ii) the absence of indication of measuring conditions of a reliable method.  The latter does not automatically lead to insufficiency of disclosure.  Perhaps the skilled person can rely on conventional measuring conditions when trying to obtain a particular parameter, bearing in mind that varying conditions could influence the measured parametric values.

The Board emphasised that the feature of the content GF(n≥10) is a clear, structural feature but, at the filing date of the patent in suit, there was no reliable method for determining when the amount of GF(n≥10) required by the claimed process was obtained.  This was the key factor in the present decision.

Conclusion

In T 2009/23, the skilled person could not prepare the desired hydrolysed inulin product across the entire claim breadth as they were not able to measure a parameter that was critical to the operation of the claimed process.  This led to a finding of insufficiency of disclosure under Article 83 EPC.

The key takeaway from the decision is that particular care should be taken when drafting patent applications wherein the invention is characterised in terms of parameters that may be difficult to measure.  However, a broader point is that critical lack of sufficiency issues are, more often than not, very difficult to remedy after filing a European patent application.  Post-filed data may be of little help in this regard.

In addition, it is worth noting that the independent product claim in the application as filed referred to the content of “GF(n≥10) and/or F(m≥11)”, while the original process claim did not include this limitation.

During prosecution, the product claim was amended to delete the reference to F(m≥11), seemingly with a view to establishing inventive step, while the process claim was amended to depend on the product claim.  The problematic parameter of the content of GF(n≥10) thus ended up in the granted claims, and the patentee was bound to the parameter for the entirety of the post-grant proceedings.  As an aside, the product claim did not survive the opposition and was dropped on appeal.

It is thus important to think ahead (i.e. have potential opposition/appeal proceedings in mind) when making claim amendments during prosecution.

If you have any questions about clarity or sufficiency of parameters under EPO practice, feel free to get in touch.

This article is for general information only and is not intended to constitute legal advice. If you would like tailored advice on a specific matter, please do not hesitate to contact me.