T 0527/17 (Muscle Derived Cells/PITTSBURGH) 01-02-2022

Reasons for the Decision

1. The appeal is admissible. It meets the requirements of Articles 106 to 108 and Rule 99(2) EPC.

2. The patent proprietor had expressed its disagreement with holding the oral proceedings by videoconference. The board nevertheless considered that the videoconference format was appropriate for the case. Therefore, oral proceedings were held by videoconference in accordance with Article 15a RPBA 2020 (see also G 1/21, Headnote).

3. Admittance of the claim requests filed at the oral proceedings before the board (Article 13(2) RPBA 2020)

In accordance with Article 13(2) RPBA 2020, any amendment to a party's appeal case made after notification of a summons to oral proceedings must, as a rule, not be taken into account unless there are exceptional circumstances which have been justified with cogent reasons by the party concerned.

3.1 The main request and the second auxiliary request, both filed at the oral proceedings before the board, result from the deletion of claims 7 to 9 (main request) and 6 to 9 (second auxiliary request) from auxiliary request 9A filed with the statement of grounds of appeal. The board holds that these amendments do not change the patent proprietor's case as put forward in its statement of grounds of appeal: they do not raise any new issue and stay within the legal and factual framework established at the outset of the appeal proceedings for the claims remaining on file. Therefore, Article 13(2) RPBA 2020 is not applicable to these requests.

3.2 By contrast, the insertion of the feature from the description "1-3 days" into claim 6 of the first auxiliary request raises new issues. For instance, it requires assessing whether the combination of features "1-3 days" and "autologous" was disclosed in the application as filed. Hence, the first auxiliary request changes the patent proprietor's case.

The patent proprietor contended that the first auxiliary request was a reaction to the board's preliminary opinion (point 12.5) that the method of claim 6 of auxiliary request 9A was not inventive because the feature "1-3 days" was missing from step (c).

This argument is not convincing. The objection relating to the absence of the feature "1-3 days" in step (c) of claim 6 was already in the decision under appeal (points 9.1.3, 9.2 and 10) and in the opponent's statement of grounds of appeal (point 4.1). It had been raised in relation to the issue of sufficiency. In its preliminary opinion (point 11, last paragraph), the board simply noted that because claim 6 was not directed to a therapeutic method but to a method of obtaining MDCs, the issue had to be discussed under inventive step rather than sufficiency. Hence, there were no exceptional reasons within the meaning of Article 13(2) RPBA 2020 justifying the filing of the first auxiliary request at oral proceedings.

3.3 Consequently, the board admitted the main request and the second auxiliary request but not the first auxiliary request.

Main request - claim 1

4. Amendments - Article 123(2) EPC

It was common ground between the parties that the main basis for claim 1 in the application as filed is claims 11 and 12, which have the following wording.

"11. A method of improving cardiac function in a mammalian subject in need thereof comprising;

(a) isolating skeletal muscle cells from the human subject,

(b) suspending human skeletal muscle cells in a first cell culture container for between 30 and 120 minutes;

(c) decanting the media from the first cell culture container to a second cell culture container;

(d) allowing the remaining cells in the media to attach to the walls of the second cell culture container;

(e) isolating the cells from the walls of the second cell culture container, wherein the isolated cells are MDCs; and

(f) administering the MDCs to the heart of the human subject;

thereby, improving cardiac function in a mammalian subject in need thereof."

"12. The method of claim 11, wherein the cardiac function improvement is improved left ventricular contractility."

In addition, the feature in step (c) of claim 1 that the cells are cultured in the second container for one to three days may be found on page 6, lines 12-13 and page 14, lines 24-28 of the application as filed.

4.1 The opponent raised two added subject-matter objections.

(a) The feature "pharmaceutical composition" in the preamble of claim 1 added subject-matter because improving left ventricular contractility had been disclosed in connection with the administration of MDCs but not a composition containing MDCs. The passage on page 16, lines 16-19 was not generally applicable because it related to Example 1 in which cells were obtained by a method other than the one in claim 11 as filed.

(b) The terms "adherent" and "non-adherent" cells had no basis in the application as filed. The application referred to "rapidly adhering" and "slowly adhering" cells, which had a different meaning. Moreover, the methods disclosed on page 6, lines 9-15 contained essential features that were missing from claim 1.

4.2 Regarding objection (a), the board agrees with the patent proprietor that the application as filed discloses in a general manner the administration of not only MDCs but also pharmaceutical compositions containing them. The repeated reference to MDCs or their compositions throughout the application already teaches that MDCs can be administered as a composition. But, in particular, the general statement on page 16, lines 16-19 that "[t]he described cells can be administered as a pharmaceutical or physiologically acceptable preparation or composition" makes it clear that the MDCs of the invention can be generally used in the form of a pharmaceutical composition.

The opponent argued that the passage on page 16, lines 16-19 was within the section "Muscle-Derived Cell-Based Treatments" starting on page 15, line 16, which related to Example 1 (page 15, line 24). As the method of isolation of MDCs in Example 1 was different to that of claim 11 as filed, the teaching of that section could not be combined with claim 11.

The board disagrees. The section "Muscle-Derived Cell-Based Treatments" refers in general terms to the MDCs and compositions comprising the MDCs of the invention. Although the section on page 15, line 24 refers to Example 1, it does so merely to indicate the markers that characterise the cells of the invention, which were studied in that example. It cannot be derived from this reference that the cells of the invention generally referred to in the section "Muscle-Derived Cell-Based Treatments" are confined to those illustrated in Example 1. Otherwise, it should also be understood that the teaching of the section is limited to e.g. mouse and rat cells, which are the MDCs studied in Example 1. This is clearly not the case since the section refers (page 16, line 4) to humans as a preferred source of cells.

4.3 Regarding objection (b), the board also agrees with the patent proprietor that the designation "adherent" and "non-adherent" cells has a proper, albeit non-literal, basis on page 6, lines 9-15 of the application as filed. This passage reads:

"the cells are cultured in a flask in culture medium for between about 30 and about 120 minutes. During this period of time, the 'rapidly adhering cells' stick to the walls of the flask or container, while the 'slowly adhering cells' or MDCs remain in suspension. The 'slowly adhering cells' are transferred to a second flask or container and cultured therein for a period of 1-3 days. During this second period of time the 'slowly adhering cells' or MDCs stick to the walls of the second flask or container."

According to this passage, in a first step, cells are cultured for 30 to 120 minutes. During this period, some cells stick to the wall of the flask container and others remain in suspension. This operation corresponds exactly to step (a) of claim 1 at issue. Whether the cells that stick to the wall are called "rapidly adhering" cells or "adherent" cells does not make the cells different, both terms refer to the same reality. This applies equally to the cells that remain in suspension with regard to the designation "slowly adhering" or "non-adherent" cells. The cell populations behind the terms used in claim 1 and in the application as filed are identical; employing different labels does not add subject-matter.

The opponent also argued that the passage on page 6, lines 9-15 disclosed a specific embodiment which contained features missing from claim 1, e.g. that before plating, the cells from the skeletal muscle explant were stored, minced and digested with enzymes. Hence, claim 1 constituted an unallowable generalisation of that embodiment.

This argument is not convincing. Claim 1 describes a method starting from human skeletal muscle cells already isolated from the human subject. The prior operations to which the opponent refers (e.g. storing, mincing and digesting) are customary steps for isolating cells from a muscle explant and not part of the method according to claim 1. Therefore, their absence in claim 1 does not add subject-matter.

4.4 Hence, claim 1 of the main request complies with Article 123(2) EPC.

5. Sufficiency of disclosure - Article 83 EPC

The opponent called into question that the MDC population obtained by the method of claim 1 was suitable for improving left ventricular contractility of the human heart. It argued that Example 1 of D9 showed that cells isolated after only two plating steps were not sufficiently myogenic for augmenting muscle tissue, a precondition for improving left ventricular contractility: at least five or six serial plating steps were necessary for this purpose.

The board agrees with the patent proprietor that the isolation method in Example 1 of D9 does not represent that of claim 1. It was carried out on rodent rather than human cells and, more importantly, it involved a different number and duration of plating steps. In contrast, Example 10 of the patent illustrates the invention as defined in claim 1. It showed (paragraphs [0125] and [0126]); paragraph [0127], last sentence; paragraph [0133], last sentence; and Table 4) that a human MDC population isolated in two subsequent plating steps of 30 to 120 minutes and two days was highly myogenic and potent in terms of muscle generation. When the cells were injected into the heart of an animal model (immunodepressed mice), they induced considerable improvement in left ventricular contractility after myocardial infarction (Table 5 and paragraph [0138]).

Thus, Example 10 of the patent proves that the cells isolated according to the method of claim 1 are suitable for the claimed purpose, and Example 1 of D9 does not raise serious doubts in this respect. The board therefore concludes that the invention is sufficiently disclosed for the skilled person to carry it out without undue burden and that claim 1 meets the requirements of Article 83 EPC.

6. Inventive step - Article 56 EPC

Claim 1 relates to the use of a pharmaceutical composition comprising an MDC population isolated from a human subject for improving the left ventricular contractility of that human subject.

The MDC population of claim 1 is isolated from cells extracted from a human skeletal muscle explant using two plating steps (see patent, page 12, line 54). In the first plating step, cells are allowed to attach to the culture container wall for 30 to 120 minutes. The attached cells, which are mostly fibroblasts, are discarded. The cells remaining in suspension are transferred to a second culture container. In this second plating step, cells are allowed to attach to the container wall during one to three days. The attached cells are the MDCs according to claim 1. They are highly myogenic and consist mostly of myoblasts showing long-term survival after administration into a soft tissue (patent, paragraphs [0014] and [0015]; paragraph [0127], last sentence; paragraph [0133], last sentence; and Tables 4 and 5). They are suitable for improving left ventricular contractility of the human heart (patent, Example 10).

6.1 The parties agreed that D9 is a suitable starting point for the assessment of inventive step in relation to claim 1.

Like the patent, D9 discloses (page 1, lines 8-20; page 6, lines 9-26 and page 24, lines 27-30) the isolation of human or animal MDCs showing long-term survival after transplantation into soft tissues. The MDCs can be used for treating conditions such as injury or weakness associated with myocardial infarction. Examples 1 and 7 of D9 are identical to those in the patent. Example 1 illustrates the isolation of mouse or rat MDCs using multiple plating steps. Most fibroblasts are separated in the first plating, which has a duration of one hour. The supernatant is then replated serially after 30-40% of the cells have adhered to each flask. The pool of cells isolated in the first four plating steps is designated as PP1-4 cells. They do not express the CD34 cell marker characteristic of MDCs (page 6, lines 11-15 and Table 2). MDCs according to the invention of D9, also called PP6 cells, are obtained in the fifth and sixth plating steps. When transplanted into a host animal, they survive more than ten times longer than the cells isolated in previous plating steps (page 31, lines 21-24). In Example 7, MDCs were injected into the ventricular wall of rats. The conclusion was that they could be used for treating conditions secondary to heart failure or myocardial infarction.

6.2 The parties agreed that the subject-matter of claim 1 differs from the teaching of D9 in at least two respects: the origin of the MDCs (human vs rodent) and the method for obtaining them (number and duration of plating steps). As the method of isolation determines the composition of the end cell population, ultimately the distinguishing feature between the subject-matter of claim 1 and D9 is the composition of their MDC populations.

It was a matter of dispute whether the therapeutic indication in claim 1 constitutes an additional difference.

The board notes that, as argued by the opponent, the title of Example 10 of the patent refers to "improving left ventricular function", while the effect shown in it is an improvement in left ventricular contractility. Thus, the example equates left ventricular contractility with left ventricular function.

The patent proprietor is right that D9 does not explicitly refer to improving left ventricular contractility. However, like the patent, D9 (Example 7; page 10, lines 26-31; and Figures 7A and 7B) is concerned with improving ventricular function after myocardial infarction. As noted by the opponent (letter of 20 July 2021, point 5.2, first paragraph, penultimate sentence), myocardial infarction mostly happens in the left ventricle, which has a greater workload. Thus, the therapeutic indications in D9 and claim 1, if not identical, substantially overlap. Therefore, in the following, the board will consider that the therapeutic indication of claim 1 does not constitute a difference over D9. In any case, this consideration has no bearing on the outcome of the assessment of inventive step (see point 6.6 below).

6.3 The effect brought about by the differences agreed by the parties is that the MDCs of claim 1 are suitable for improving the left ventricular contractility of the human subject from which they have been obtained.

6.4 The objective technical problem to be solved may thus be formulated as providing a product suitable for improving left ventricular contractility in a human subject needing it.

The pharmaceutical composition of claim 1 solves this problem (see point 5 above).

6.5 On the issue of obviousness, the parties cited documents D8 and D5.

D8 (abstract; page 1, lines 8-18 and 23-29; and examples) relates to the isolation and use of myogenic cells, focusing on their orthopedic and urologic applications. Example 9 (page 88, line 27 to page 89, line 8), which is directed to orthopedic treatments, discloses the isolation of myogenic cells using a method as in claim 1 at hand, except that the cells are not human. Cells from a rabbit muscle explant were plated for one hour to remove fibroblasts. The supernatant was then replated for three days to obtain an end cell population enriched in myoblasts. Contrary to the patent proprietor's contention, this end cell population had to be detached from the culture container wall and isolated for its subsequent use in therapy.

D5 (title) is a study on the retention of differentiation potentialities of myogenic cells in in vitro cultures. It discloses (page 478, paragraphs 2-4) the isolation of myoblasts from a rat muscle explant using the steps defined in claim 1 at issue: primary cells were plated for 40 minutes to remove fibroblasts and epithelial cells; the supernatant was then replated for three to four days to obtain an end cell population highly enriched in myoblasts.

6.6 Starting from D9, the board shares the patent proprietor's view that the skilled person would not have turned to the methods of D8 or D5 to improve left ventricular contractility in a human subject.

D9, D8 and D5 rely on the same general principle for isolating myogenic cells, namely that fibroblasts attach to the culture container wall much more rapidly than myoblasts. Thus, each plating step removes fibroblasts and enriches the end population in myoblasts. In the three documents, the primary cell culture was submitted to an initial plating step of no more than one hour in which fibroblasts were removed. D5 and Example 9 of D8 did not contain any additional purification step. At the end of the second plating, myoblasts were collected. In contrast, the method of Example 1 of D9 involved three additional plating steps in which remaining fibroblasts were separated. Thus, the MDC population collected at the end of the method of D9 (PP6 cells) was certainly more enriched in myogenic cells than that of D5 or Example 9 of D8. In fact, the method of D9 (Table 2) managed to completely exclude the cells that do not express the marker CD34, which is characteristic of MDCs. This was not the case when fewer plating steps (PP1-4 cells) were performed. Hence, the skilled person would have considered the end cell populations of D5 and Example 9 of D8 to be less myogenic than those of D9.

The skilled person wishing to translate the therapeutic effect on the myocardium shown in Example 7 of D9 from rodents to humans would therefore be prompted to use human myogenic cells isolated according to the method of D9 and disregard the methods of D5 or Example 9 of D8.

Hence, the board holds that the subject-matter of claim 1 is inventive.

Main request - claims 2 to 5

7. The subject-matter of claims 2 and 3 is essentially the same as that of claim 1 except that claims 2 and 3 are directed to the use of MDCs as such rather than to a pharmaceutical composition containing them. Claims 4 and 5 are dependent on claims 2 and 3.

The opponent did not raise any objection directed specifically against any of claims 2 to 5.

Regarding the issue of added subject-matter (Article 123(2) EPC), the objection relating to the features "adherent" and "non-adherent" cells, also present in claim 2 and 3, was dealt with in point 4.4 above.

Regarding the issues of sufficiency of disclosure and inventive step, for the reasons put forward in relation to claim 1 (see points 5 and 6), the subject-matter of claims 2 to 5 also meets the requirements of Articles 83 and 56 EPC.

Main request - claim 6

8. Inventive step - Article 56 EPC

Claim 6 is directed to a method of isolating human MDCs which comprises steps (a) to (d) defined in claim 1. However, in claim 6, the duration of step (c) is not limited to one to three days.

8.1 The parties agreed that D8, in particular the two-step method disclosed in Example 9, is a suitable starting point for the assessment of inventive step in relation to claim 6. The board sees no reason to differ.

8.2 The method of claim 6 differs from the one in Example 9 of D8 in that the MDCs are of human origin.

The patent proprietor argued that there were two additional differences. First, the method of D8 does not disclose a second plating step because it does not indicate that the end cell population was detached from the container wall at the end of the process. Second, the cells of claim 6 are autologous.

These arguments must fail. First, D8 (page 89, lines 6-8) discloses that the supernatant of the first plating step was replated for three days to obtain a myoblast population. Obviously, the myoblast population had adhered to the culture container wall during those three days and had to be detached and isolated for its use in the subsequent therapeutic treatment. Second, the feature "autologous" in the method of claim 6 is void since the method does not encompass any step in which the isolated MDCs are administered to a subject.

8.3 The only effect that can be associated to the fact that the MDCs of claim 6 are human rather than rodent is that they can be administered to a human.

As claim 6 does not specify the duration of step (c), its end MDC population is not necessarily suitable for improving left ventricular contractility. This was conceded by the patent proprietor when asked by the board at the oral proceedings. It is apparent that if step (c) is too short, the MDC population will not be sufficiently enriched in myogenic cells; if too long, MDCs would start differentiating and lose their myogenic character.

8.4 Thus, the objective technical problem to be solved by claim 6 is providing a method for isolating human MDCs.

8.5 The MDCs isolated in D8 (page 24, lines 17-20 and page 102, lines 17-19) were intended for therapeutic purposes in humans. Hence, isolating human MDCs by the method in Example 9 of D8 was an obvious solution to skilled person.

8.6 Therefore, the subject-matter of claim 6 is not inventive.

Second auxiliary request

9. The five claims of the second auxiliary request are identical to claims 1 to 5 of the main request. It has been shown above (points 4 to 7) that these claims meet the requirements of Articles 123(2), 83 and 56 EPC. Consequently, none of the grounds for opposition raised in these proceedings prejudice the maintenance of the patent on the basis of the second auxiliary request.

10. Remittal - Article 111 EPC

At the end of the oral proceedings before the board, the parties agreed that the case be remitted to the opposition division for adapting the description.