T 1185/97 02-02-2000

Reasons for the Decision

1. The appeal is admissible.

2. Amendments and admissibility of the different requests

2.1. With respect to the version as maintained by the Opposition Division, claim 1 according to the fall-back version only differs in that the last words "or urethane resin" have been removed. Such deletion is admitted because the removed expression was neither present in the application as filed nor in claim 1 as granted.

Moreover, this version is not regarded as late-filed since claim 1 as amended above was filed by the respondent at the very beginning of the appeal proceedings and in response to appellant's objection made in the statement of grounds. Therefore, this request is considered by the Board.

2.2. The main and auxiliary requests were submitted by the respondent in the course of the oral proceedings, after the previous version (fall-back) had been discussed. According to the constant Case Law of the Boards of Appeal (see in particular T 153/85, OJ EPO 1988, 1, point 2.1 and T 840/93, OJ EPO 1996, 335), late-filed requests can only be considered at a very late stage if they are clearly allowable.

In the present case, the amendments made to claim 1 of these requests give cause for additional objections as to clarity and adequate support under Articles 84 and 123(2) EPC, although, corresponding passages can be found in the description:

In claim 1 of the main request, the added expression "whereby expansible parts (342) of the anti-migration members (42, 44) expanded from horizontal parts (341) and bended vertically" is to be found in column 6, lines 23 to 25 of the patent specification.

In claim 1 of the auxiliary request, the added expression "wherein the second connecting members (36, 38) consists of vertical parts (34, 341) and expansile parts (34, 342)" is based on claim 7 as granted, which in turn is identical to claim 7 as originally filed.

However, the above incorporated features refer to parts 341 of he anti-migration members which are said to be directed horizontally in one place of the description (claim 1 to the main request; description column 6, line 24; Figure 4) and vertically according to another (claim 1 of the auxiliary request; claim 7 as granted; claim 2 under appeal). When this contradiction was recognised by the respondent at the oral proceedings, it requested to be allowed to present even further amendments to the claims.

Moreover, the Board cannot recognise in how far the "expansible parts 342" according to the main request ("expansile" in the auxiliary request), are suitable to contribute to the expansion capabilities of the different cylindrical parts of the stent, since expansion is produced by the zig-zag configuration of the unit structures, of which parts 342 of the connection members are excluded. As was rightly explained in the application as originally filed (cf. page 11, lines 27 to 29), the diameter of the anti-migration members 44 depends on the length of horizontal parts 341 of the second connecting members 34. It results therefrom that parts 342 play no role in the diameter after expansion of the anti-migration members.

Despite numerous more or less appropriate corrections made in the patent description during the previous proceedings, the different structural parts of the stent and their respective functions are still neither clearly identified nor defined, so that the subject-matter of claim 1 as a whole is neither clear nor unambiguously based on the description. Since the amendments brought to claim 1 according to either the main or the auxiliary request are not prima facie allowable, the late-filed requests are not admitted at this late stage of the proceedings (see Case Law, 3rd edition 1998, page 506).

Consequently, the fall-back version of the claims has to be examined as to its merits.

3. Closest prior art and novelty

3.1. Document D3 represents the closest prior art document. Using the terminology of claim 1 as it stands (fall-back version), document D3 discloses (cf. Figure 1) an expandable stent comprising a cylindrical frame formed by a plurality of unit structures, each formed into a closed zig-zag configuration, including an endless series of straight and bends sections (Figure 1A). Connecting members (monofilament lines) are provided for connecting adjacent unit structures (page 100, right column and page 101, right column, 2nd paragraph). Further, anti-migration members in the form of frusto-conical skirts having the same zig-zag configuration as that of the unit structures (Figure 1C) and diameters larger than the diameter of the central frame, are connected to both ends thereof by additional connecting members (monofilament lines). As explained in the left column of page 101, the function of the skirts is, among others, to prevent stent dislodgement, which is facilitated by the overall expanded diameter of the stent (page 101, right column, 2nd paragraph).

3.2. With respect to the disclosure of document D3 the subject-matter of claim 1 differs by the two last features namely:

- a mesh is wrapped whole around the outside of said frame and the anti-migration members,

- said mesh is coated with silicon rubber.

3.3. Since no other document than D3 comes closer to the subject-matter of claim 1 in suit, it must be regarded as novel within the meaning of Article 54(1) EPC.

4. Inventive step

4.1. The above distinguishing features, which relate to a mesh wrapped around the stent and coated with silicon rubber represent the solution to a technical problem which is more restricted than that originally defined, namely to prevent cancer cells from penetrating into the stent (patent, column 2, lines 8 to 10 and column 4, lines 14 to 17, the latter passage having been deleted from the patent specification in the version of the decision under appeal).

4.2. The Korean document D1 (see English translation D1A originating from the patentee itself and annexed by the appellant to the statement of grounds of opposition) discloses an expandable esophageal stent made of stainless-steel wire formed in a zig-zag pattern (top of pages 1 and 2). The stent is said to be made by the same method as that of Gianturco (page 1, last paragraph) which is also referred to in document D3 (page 100, left column), then covered by a nylon mesh coated with silicon rubber, in order to prevent malignant obstruction due to tumour ingrowth (bottom of pages 6 and 7).

Faced with the above mentioned problem of avoiding tumour proliferation into the stent, the skilled person would immediately consider to use the solution proposed in document D1 which appears to be perfectly appropriate. In document D1 as in the contested patent (column 4, lines 2 to 3) the mesh is made of nylon (although not claimed) and coated with silicon. The same structure and the same materials will necessarily result in the same technical effects, the more since both stents are designed for the same application to the esophagus. Besides, the Board observes that the features now under consideration were originally considered as optional by the use of the introductory terms "It is preferable that" placed just before the features characterising the mesh (cf. column 4, lines 1 to 2). Although these terms were subsequently deleted from the description, they are still indicative of the cursory nature of said features.

The respondent's argument that document D1 does not suggest the provision of enlarged silicon coated anti-migration members at both ends of the central body is not convincing, since a proper assessment of document D1 does not require the consideration of the anti-migration members which were already known from the closest prior art document. On the other hand, a meaningful interpretation of document D1 requires that the mesh proposed therein must necessarily wrap the stent in its entirety, whatever its shape, in order to achieve full protection against obstruction by tumour ingrowth.

Considering now that the general problem of avoiding ingrowth and proliferation of undesirable tissue inside the stent lumen so as to maintain its efficiency, was already referred to in document D3 (page 102, left column), such indication is regarded by the Board as a link between documents D3 and D1, which suggests the combined consideration of their disclosure

4.3. For the foregoing reasons, the Board is satisfied that the subject-matter of claim 1 according to the fall-back version lacks an inventive step, contrary to the requirements of Article 56 EPC.