CABINET CHAILLOT

T 3109/19

European patent 2 429 486 was granted with independent claim 1 relating to:
"Process for preparing a crosslinked gel of at least one polysaccharide or one of its salts, comprising at least the steps that consist in:
a) providing an aqueous medium containing said polysaccharide,
b) forming a homogeneous gel from the medium from step a),
c) bringing the gel obtained in step b) into contact with an effective amount of at least one crosslinking agent;
d) crosslinking said mixture formed in step c); and
e) recovering said crosslinked hydrogel,
wherein
- at least said steps a) to d) are carried out within a hermetic cavity delimited at least partially by a deformable wall, said cavity being made within a deformable pouch, the mixture present in the cavity being exposed, in step d), to conditions conducive to crosslinking;
- the homogenization, considered in step b) is carried out by optionally successive, mechanical deformations of the outer face of the deformable wall or of the pouch."
An appeal was filed by the patent proprietor against the decision of the opposition division to revoke the patent.
The appellant filed a new main request and auxiliary requests 1-6.
Claim 1 of this main request corresponds to claim 1 of the patent as granted except for the definition of the following additional feature: "wherein the polysaccharide is hyaluronic acid or one of its salts."
The Board recalls that the problem solution approach implies that in case an inventive step can be recognized starting from a particular item of prior art which is convincingly identified as most promising starting point and thus represents the closest prior art, attempts to argue a lack of inventive step starting from less promising starting points are bound to fail. However, in case an inventive step is apparently convincingly denied starting from a promising particular item of prior art, the mere argument that the claimed subject-matter nevertheless involves an inventive step in view of an allegedly closer prior art, may not be persuasive, because in such case the allegedly closest prior art is likely to represent a starting point that is in fact not more promising.
In the present case two types of known processes for preparing injectable gels of crosslinked hyaluronic acid have been proposed as starting points in the prior art, namely
(a) the process for preparing a crosslinked hyaluronic acid gel described in examples 4-1/4-2 of document D1 in which a deformable pouch is used as defined in the claims, but in which the crosslinking agent is combined with the hyaluronic acid prior to gel formation
(b) the "conventional" process for preparing a crosslinked hyaluronic acid gel as described in documents D2-D5 in which the crosslinking agent is added after gel formation with the hyaluronic acid as defined in the claims, but in which the process is carried out in a conventional receptacle instead of a deformable pouch.
In view of the common objective of preparing injectable gels of crosslinked hyaluronic acid and the complementary nature of the differences of the two types of processes with the claimed process the Board considers it purposeful to assess the requirement of inventive step starting from each one of the two types of processes rather than to attempt to determine which of the two starting points is actually the more promising.
- Assessment starting from document D1: D1 describes the preparation of crosslinked hyaluronic acid gels suitable for injection in which physical cutting of the hyaluronic acid polymer chain during stirring and mixing steps is avoided. D1 discloses the preparation of such a gel in which hyaluronic acid is added to a crosslinking agent in a deformable pouch with subsequent mixing by kneading for 5 minutes. The process of claim 1 of the main request differs from this process of D1 in the formation of a hyaluronic acid gel prior to the addition of a crosslinking agent.
The patent indicates that the claimed process allows for providing gels with an improved injectability profile with respect to gels which are conventionally prepared in a rigid receptacle.
The problem to be solved starting from document D1 may therefore be seen in the provision of an alternative process allowing the preparation of injectable gels of crosslinked hyaluronic acid.
The skilled person would expect that the efficient initial blending of the components is favoured by starting the mixing before the actual gel formation and that the initial blending is less efficient if started after the gel formation, because the increased viscosity of a gel opposes such blending. This expectation finds confirmation in document D2, which indicates flake formation and local overcrosslinking from mixing a gel with a crosslinking agent. Accordingly, it would not be evident from document D1 itself that the modification of the process by performing initial gel formation prior to the addition of the crosslinking agent represents a suitable alternative.
Documents D2-D5 describe the preparation of injectable crosslinked hyaluronic acid gels involving initial gel formation and subsequent combination with a crosslinking agent in a conventional receptacle. Document D2 specifically indicates that the conventional preparation involving gel formation before addition of the crosslinking agent is associated with the risk of formation of "flakes" and local overcrosslinking and that this risk is effectively avoided by a process in which the crosslinking is carried out during gel formation. Moreover, documents D3-D5 do not mention any process involving crosslinking during the gel formation, let alone that such process could be exchanged with the conventional type of process involving gel formation prior to crosslinking.
The Board therefore concludes that the process of claim 1 of the main request would not be obvious to the skilled person starting from document D1 as closest prior art.
- Assessment starting from documents D2-D5
Documents D2-D5 describe the preparation of injectable crosslinked hyaluronic acid gels involving initial gel formation and subsequent combination with a crosslinking agent in a conventional receptacle.
The process of claim 1 of the main request differs from the conventional type of process as described in documents D2-D5 in the use of a deformable pouch for the gel formation and crosslinking instead of a conventional rigid receptacle.
The patent indicates that the claimed process allows for providing gels with an improved injectability profile with respect to gels which are conventionally prepared in a rigid receptacle.
The respondents' argument, that the differences in the injection profiles reported in the patent cannot be attributed to the mere use of a pouch as defined in the claims due to the further differences in homogenisation time and temperature profiles in the compared processes, is not considered convincing.
The problem to be solved starting from the conventional type of process as described in documents D2-D5 may therefore be seen in the provision of a process allowing the preparation of gels of crosslinked hyaluronic acid with an improved injection profile.
Documents D2, D4 and D5 do not make any reference to the use of a deformable pouch.
Document D1 describes the utility of a pouch for gently mixing hyaluronic acid and a crosslinking agent to produce a gel-like mixture. However, document D1 does thereby not suggest that the conventional type of process described in documents D2-D5 involving gel formation prior to crosslinking could be improved in terms of injectability of the crosslinked hyaluronic acid product by performing the process in a deformable pouch.
Documents D6-D11 describe the use of a deformable pouch as a convenient method for mixing a variety of components, but do not refer to any use of a deformable pouch for gel formation and crosslinking. These documents provide therefore no suggestion as to the utility of a deformable pouch for improving the conventional type of process of documents D2-D5 with regard to the injection profile of the resulting crosslinked gels.
The Board therefore concludes that the process of claim 1 of the main request would not be obvious to the skilled person starting from the conventional type of process as described in documents D2-D5 as closest prior art.
Accordingly, the Board concludes that the main request meets the requirement of inventive step.
The decision under appeal is set aside and the case is remitted to the opposition division with the order to maintain the patent on the basis of the main request.

https://www.epo.org/law-practice/case-law-appeals/recent/t193109eu1.html

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