T 1146/02 (Vaccines containing a saponin and a sterol/SMITHKLINE BEECHAM) 08-03-2005

Reasons for the Decision

Article 123(2)(3) EPC

1. Claim 1 of the main request is a combination of claims 1, 2 and 4 as originally filed, respectively of claims 1 and 4, with the feature "and in that the QS21 is at least 90% pure". The latter feature finds basis on page 1, lines 28 to 29, of the application as filed (published WO application). Claims 3, 7, 8 and 10 to 12 are identically contained in the claims as originally filed. The same claims and claims 4 to 6 and 9 are identically contained in the claims as granted. Claim 2 is based on page 2, lines 7 to 9 of the application as filed. Claim 4 finds a basis on page 2, lines 19 to 20 of the application as filed. Claim 6 finds basis at page 2, lines 34 to 38 of the filed application. Claim 9 finds basis on page 1, lines 1 to 2 and page 5, lines 16 to 17 of the application as filed.

2. The respondent argues that introduction of the QS21 purity in claim 1 of the main request raises an issue under Article 123(3) EPC, since at 90% purity, the saponin:sterol ratio becomes 0,9:1 and the ratio 1:100 becomes 0,9:100, thereby broadening the protection conferred by the claim as granted.

3. The board cannot concur with this respondent's view. Claim 1 of the patent as granted refers to "an immunologically active saponin fraction derived from the bark of Quillaja Saponaria Molina" and is devoid of any explicit statement as to the ratio saponin:sterol. In the board's judgement therefore the protection conferred by claim 1 of the main request, exemplifying the saponin, i.e. QS21 and its purity entails to narrowing the protection conferred as compared to the granted claim.

4. The board is thus satisfied that claim 1 of the main request complies with the requirements of Article 123(2) and (3) EPC.

Clarity - "at least 90% pure"

5. Claim 1 of the main request is directed to vaccine compositions comprising an antigen, QS21 and a sterol wherein the ratio of QS21:sterol is from 1:1 to 1:100 (w/w) and the QS21 is at least 90% pure. It is the respondent's view that this feature is unclear.

6. In a first line of argument the respondent maintains that the requirement in claim 1 for the QS21 to be "at least 90% pure" renders it unclear in the absence of any indication whether "at least 90% pure" related to the starting purity of the QS21 used in the manufacture of the claimed composition or to the purity of the QS21 within the composition itself. Hence, he/she would not be able to distinguish between impurities that were present in the GS21 that was used to formulate the composition and the impurities in other components of the composition. Therefore, it is not possible for the skilled person to determine whether or not a given composition falls within the scope of claim 1.

7. In the context of Article 84 EPC, the meaning of a term or expression used in a feature of a claim depends in particular on the definition thereof generally accepted by those skilled in the relevant art, as established by Rule 35(12) EPC, last sentence, requiring in general terms that use should be made of the technical terms generally accepted in the field in question.

8. The patent in suit (see paragraph [0002]) defines QS21 as a fraction obtained by subjecting to HPLC an aqueous extract of the bark of the Quillaja Saponaria Molina tree according to document (D6), disclosing the isolation of QS21 from natural sources. QS21 (termed "QA-21" in document (D6)) is by definition the 21st fraction eluting from the HPLC column as a very minor component (see ibidem, Table 1). The skilled person relevant for elucidating the meaning of the feature "at least 90% pure" when relating to QS21 is thus a person working in the field of the purification of natural products.

9. Document (D6) in column 4, lines 36 to 42, defines the term "substantially" pure in the context of the saponin fractions, including the QS21 fraction, as meaning "substantially free from compounds naturally associated with the saponin in its natural state and exhibiting constant and reproducible chromatographic response, elution profiles, and biological activity". On lines 43 to 54 of the same column, document (D6) sets the experimental standards for substantially pure saponin fractions, including "QA-21", i.e., they should appear as only one major peak or band in defined experimental protocols. Further, it can be derived from the wording of claim 5 of the same document that QA-21 (QS21) is "substantially" pure if one predominant peak comprises 90% or more of the total area of the peaks around the retention time of 51.6 min corresponding to the 21st fraction eluting from the HPLC column.

10. The above definition of the purity of QS21 as a ratio between the area of the predominant peak and the total area of the peaks around it is in line with that adopted in Figure 2 of document (D12), showing different stages of purity of HPLC-purified QS21. It can be seen from this Figure that the secondary peaks relating to compounds naturally associated with the QS21, i.e., contaminant saponins, vanish as purity reaches 98% (see Figure 2D).

11. The board therefore concludes that the feature "at least 90% pure" in claim 1 and on page 2, line 20 of the patent in suit is clear to the skilled person and means that the starting product, i.e., QS21 should contain 10% or less naturally associated substances, i.e., the other saponin contaminants as detectable during the purification process as secondary peaks around the QS21 main peak.

12. Moreover, the respondent's argument that it is not possible for the skilled person to determine whether or not a given composition falls within the scope of claim 1 is not convincing. This is because the HPLC elution profiles as depicted in Figure 4B of document (D6) and Figure 2 of document (D12) can easily be obtained by the skilled person from formulated vaccine compositions falling within the definition of the subject-matter of claim 1. The saponin contaminants associated with QS21, known to be distinct from those found from sterol and antigen can easily be detected and quantified from this HPLC elution profile. In conclusion, the skilled person is in a position to experimentally verify whether or not a given composition falls within the scope of protection provided by claim 1.

13. In the respondent's view, the claims are also not clear in the absence of any explanation therein as to how the percentage purity of QS21 should be calculated. However, the skilled person would calculate this percentage as a ratio between the area of the predominant peak and the total area of the peaks around the retention time of 51.6 min corresponding to the 21st fraction eluting from the HPLC column (see points 9 to 11 supra).

14. Finally, since the wording "at least 90% pure" is clear, the respondent's line of argument that the introduction of the concept of purity in the claim renders the ratio saponin:sterol used in the claim unclear, must fail.

15. In view of the foregoing, the board concludes that no case of lack of clarity has been made out.

Sufficiency of disclosure

16. The opposition division decided that the claims of the main request as presently before the board did not satisfy the requirements of Article 83 EPC because claim 1 covered the oil-in-water emulsions referred to on page 2, line 49 of the patent in suit, but the disclosure of the patent was insufficient to allow a skilled person to make these oil-in-water emulsion-based adjuvant formulations.

17. However, in paragraph 5.8 of his letter dated 6 June 2003 the respondent submitted that "The opponent does not doubt that the techniques required for manufacturing oil-in-water emulsions were well known at the priority date. Nor does the opponent doubt that a skilled person could have formulated QS21 and cholesterol onto an oil-in-water emulsion had they been asked to do so". Therefore, the respondent's attack under Article 83 EPC is not directed against the manufacture of oil-in-water emulsions comprising QS21 and cholesterol in general. The board agrees as well that the skilled person, even in the absence of detailed instructions or examples in the patent, could have formulated QS21 and cholesterol as an oil-in-water emulsion in the light of e.g. documents (D14) to (D17), disclosing the preparation of oil-in-water emulsions in general.

18. The respondent rather argues that only oil-in-water emulsions which (a) include the adjuvant 3D-MPL and (b) have a particular partitioning of QS21 and cholesterol (QS21 in the aqueous phase and cholesterol in the oil phase) would exhibit the desired useful properties.

19. To support his case the respondent relied on document (D13), a later patent application filed by the patentee stating on page 4 that the observed similar efficacy of the QS21/cholesterol oil-in-water emulsions as compared to the liposomal compositions was "surprising". This implied, in the respondent's view that further inventive skill was required to formulate an adjuvant composition not in the form of liposomes, but in the form of an oil-in-water emulsion which (a) included the adjuvant 3D-MPL and (b) had the QS21 in the aqueous phase and cholesterol in the oil phase, namely the only non-liposome QS21/cholesterol adjuvant formulation having the desired useful properties.

20. The board firstly observes in passing that making a selective invention over an earlier broader patent does not necessarily mean that the earlier patent is insufficient. Secondly it is noted that 3D-MPL referred to in document (D13) is merely an optional further adjuvant/immunomodulator (see paragraph bridging pages 5 and 6 and claim 9 of document (D13)), which is not critical for achieving the useful stability and non-toxicity properties of the claimed QS21/sterol adjuvant. This is shown by Example 5 of document (D13) (see page 22, Table 7 and page 23, lines 10-15), according to which the oil-in-water adjuvant SB62'c (comprising cholesterol) turns out to be better than SB62' (devoid of cholesterol) in terms of useful properties, despite 3D-MPL is present in both SB62'c and SB62' (see Table 7: "MPL" in combination with page 13, line 19: "3D-MPL"). Therefore, the respondent's contention that 3D-MPL is a critical component for obtaining useful non-liposome QS21/cholesterol adjuvants is not convincing.

21. The respondent also maintains that a particular partitioning of QS21 and cholesterol (QS21 in the aqueous phase and cholesterol in the oil phase) was required in order that QS21/cholesterol adjuvants exhibit the desired useful properties. To buttress the above view, the respondent referred to paragraph [0028] of the patent in suit disclosing an attempt to produce a useful adjuvant composition by combining QS21 with a soluble derivative of cholesterol, which attempt was acknowledged to have failed.

22. In the experiment described in paragraph [0028] of the patent, the sterol has been modified so as to behave as a bilayer-forming phospholipid able to form a stable suspension of liposomes, bearing the sterol moiety. However, something went wrong and the composition did not exhibit the desired useful properties.

23. In the board's judgement, completely altering the chemical nature of a critical molecule, in this case the sterol referred to in claim 1 at issue, which is normally lipophilic (see page 5, line 3: "cholesterol is insoluble in aqueous solution") to make it water-soluble (up to 60 mg/ml) by attachment thereto of a long hydrophilic chain, is not the way the cautious skilled person would normally proceed. The (not completely unexpected) failure reported in paragraph [0028] of the patent cannot thus be considered as a proof that other forms of QS21/sterol adjuvants do not deliver the promised advantages. Paragraph [0010] of the patent in suit as well as documents (D10) (see "composition 8") and (D13), containing data showing the advantageous properties of compositions in the form of oil-in-water emulsions, rather suggests that the carrier (liposomes, microspheres (i.e., oil-in-water emulsions), etc) is not critical.

24. In conclusion, the claims satisfy the requirements of Article 83 EPC.

Novelty

25. The board has concluded in point 11 supra that the feature "at least 90% pure" has to be read in the context of contamination with other saponins contained in the natural extracts. Lack of novelty can therefore only occur if a prior art document discloses compositions comprising, inter alia, QS21 in the purity required by claim 1, the latter being a distinguishing (and measurable) feature (see point 12 supra).

26. Documents (D8) and (D18) disclose immuno stimulating complexes (Iscom's) which are stable particulate complexes of protein antigens incorporated into cage-like structures obtained by mixing a detergent, a lipid and a saponin. The compositions described in these documents are based on Quil-A (see document (D8), page 3, line 60 and document (D18), page 163, lines 10 to 16), cholesterol and an antigen. It is the respondent's view that these compositions fall under claim 1 because they exhibit a ratio QS21:sterol of 1:60 to 1:20.

27. However, according to document (D6), column 10, Table 1, QS21 ("QA-21") is a fraction (3.7%) of Quil-A ("Superfos"). Accordingly, compositions comprising "Quil-A" do not meet the requirement that the QS21 be at least 90% pure.

28. Accordingly, in the board's judgement documents (D8) and (D18) do not prejudice the novelty of claim 1 of the main request.

29. As for document (D3), a document relevant under Article 54(3) EPC, it discloses Iscom preparations based on certain fractions of Quil-A, including fraction QH-C, of which the purification is described in Example 1 thereof. The respondent argues that Figure 1 of document (D3) shows that the QH-C fraction is located in the most hydrophobic Quil-A fraction and therefore must contain QS21 in view of the fact that Figure 1 of document (D6) also shows that QS21 is located in the most hydrophobic fraction of Quil-A.

30. However, a comparison of the experimental conditions applied for deriving the data shown in the two figures reveals major differences, such as for example the use of HPLC (documents (D3)) vs. reverse phase HPLC (document (D6)). Furthermore, it is apparent from Figure 1 of document (D3) that the QH-C fraction constitutes a quite narrow selection of the hydrophobic end of the retention profile. Therefore, in the board's judgement, a comparison of the elution profiles of Figures 1 of documents (D3) and (D6) does not make sense and any inferences from their comparison cannot be technically relevant.

31. In conclusion, there is no evidence before the board that the QH-C fraction referred to document (D3) comprises QS21, let alone "at least 90% pure" QS21.

32. It is established case law of the Boards of Appeal that where lack of novelty is alleged, the burden of proof lies with the party claiming that the information in question was made available to the public before the relevant date.

33. Since the respondent has also not discharged its burden of proof to establish that fraction QH-C contains QS21 in the required purity, the board concludes that document (D3) is not prejudicial for the novelty of claim 1.

34. A similar situation as for document (D3) arises in relation to document (D19), which discloses liposomes based on Quillaja saponins obtained from three different sources (see document (D19), page 171, under the heading "Material Tested for Adjuvanticity") and which are confirmed to be chemically inhomogeneous and to contain a mixture of triterpene glycosides (see page 175, sentence bridging l-h and r-h columns).

35. It cannot be derived from document (D19) that QS21 is at all present in the disclosed liposomes, let alone in the concentration as required in claim 1 of the main request. Accordingly, the board considers that with respect to the novelty of claim 1 of the main request over document (D19), the respondent has not discharged its burden of proof to establish that fraction QH-C contains QS21. The board therefore concludes that document (D19) is not prejudicial for the novelty of claim 1.

36. In conclusion, the claims of the main request satisfy the requirements of Article 54 EPC.

Inventive step

37. The patent in suit is concerned with the use of the saponin QS21 as an adjuvant in vaccine compositions and claim 1 of the main request is directed to a vaccine composition comprising an antigen, the saponin QS21 and a sterol. It is stated in the patent that purified QS21 has two drawbacks, namely (i) it is unstable (see page 2, line 24) and (ii) it exhibits toxicity (e.g., necrosis at the injection site) when used as adjuvant (ibidem, lines 10-12). The patent in suit thus purports to overcome said drawbacks.

38. The parties propose two possible starting points for the problem-solution approach, i.e. in a first one, document (D6) or (D12) represents the closest prior art, whereas in a second one either of documents (D1), (D8) or (D18), disclosing immunogenic compositions containing an antigen, the saponin Quil A and a sterol, represents the closest prior art. It therefore needs to be established which of the above documents represents the closest prior art for assessing the inventive step.

39. Document (D8) and (D18) deal with the preparation of immunogenically enhanced formulations of Quil A-based vaccines in the form of Iscom's. Document (D1) deals with a similar specific enhanced formulation of Quil A-based vaccines, namely in the form of liposomes. However, documents (D1), (D8) and (D18) are silent as to the objective to reduce drawbacks (i) and/or (ii) emphasised in point 37 supra.

40. Document (D6) addresses the same drawbacks (i) and (ii) dealt with in the patent in suit. The document indeed discloses the purification of at least 22 fractions with saponin activity from the crude aqueous extract termed Superfos ("Quil A") from a Quillaja saponin preparation. Four saponins were identified as predominant in Quil A, i.e. those contained in fractions QA-7, QA-17, QA-18 and QA-21 (the latter being identical to fraction QS21 used in the patent in suit). Animals injected with QA-21 appeared mildly ill initially but appeared to recover fully within a few hours after injection, unlike those injected with Quil-A (see the passage bridging columns 21 and 22). The loss of adjuvant activity upon hydrolysis is referred to in column 22, lines 36-49 of this document.

41. The problem of (i) the instability of QS21 to base-mediated hydrolysis and (ii) toxicity have also been addressed in the review document (D12), co-authored by one designed inventor of document (D6) (see section 3.3. bridging pages 529 and 530 and page 538, first paragraph, respectively).

42. Both documents (D6) or (D12) thus represent prior art closer to the claimed subject-matter than documents (D1), (D8) and (D18). The board considers document (D6) as the appropriate starting point for the problem-solution approach, noting however, that any reasoning would not change by departing from document (D12).

43. The structural difference between the subject-matter of claim 1 and the compositions disclosed in document (D6) is the addition of a sterol in a specific ratio to the immunogenic composition containing QS21 of document (D6). In view of the achieved technical effect the problem to be solved can therefore be formulated as the provision of QS21 containing immunogenic compositions exhibiting decreased reactogenicity (toxicity/necrosis) at the injection site and enhanced stability of QS21 to base-mediated hydrolysis, while the adjuvant effect is maintained (see patent page 2 lines 22 to 26).

44. In view of the experimental results presented in Examples 1.4 to 1.6 and 1.8, 1.9 and 2 of the patent in suit and those filed during the opposition proceedings in the form of document (D10)(compare the figures for Group 2 (QS21 alone) with the figures for Groups 6, 7 and 8 (QS21 with cholesterol in various compositions), wherein the reduction in necrosis in the compositions containing cholesterol is evident), the board is satisfied that the above problems have been solved.

45. The respondent argues that the technical effects invoked by the appellant, namely detoxification and stabilisation of QS21 without loss of its adjuvant effect are shown neither in the patent nor in document (D10) since these documents dealt with formulations devoid of an antigen, contrary to the requirement of claim 1 at issue.

46. However, the purpose of these data relating to formulations lacking the antigen is to show that the toxic effect of QS21 is reduced and its stability is enhanced by the presence of a sterol. These effects, relevant to the inventive step issue, occur independently from the adjuvant (immunostimulant) effect of the composition, which adjuvant effect is also shown by the patent (see Examples 1.8, 1.9 and 2), albeit less relevant to the inventive step issue. Therefore, in the board's view, the data given in the patent in suit and in document (D10) are suited to demonstrate the detoxifying and stabilizing effect of a sterol on QS21, which technical effects are in turn suited to support inventive step.

47. The respondent also maintains that the advantageous effects are merely shown for the vaccines in the form of liposomes. However both documents (D10) (see "composition 8") and (D13) contain data showing the advantageous properties of compositions in the form of oil-in-water emulsions. It is true that these compositions contain 3D-MPL, however the fact that 3D-MPL is not involved in reducing the toxic effect of QS21 or in enhancing its stability has already been dealt with under point 20 supra in the context of sufficiency of disclosure.

48. Finally the respondent relies on paragraph [0028] of the patent for arguing that claim 1 covers embodiments which do not achieve the promised technical effects, and which are thus not inventive according to decision T 939/92 (Agrevo; OJ EPO 1996, 309).

49. However, the board does not see the factual situation of the present case in the framework of the above decision, but rather in that of the case law (see decision T 14/83, OJ EPO 1984, 105) that it is of no consequence that one specific set of parameters within a claim occasionally leads to a formulation not having the advantages promised by the patent (see paragraph [0028] of the patent), so long as substantially all embodiments covered by a claim provide a solution to the problem to be solved. An occasional failure can thus be "forgiven" since there is ample evidence before the board, not contradicted by any data from the respondent, that substantially all of the claimed formulations do provide a solution to the problems addressed by the patent.

50. Moreover, as emphasized under point 23 supra in the context of sufficiency of disclosure, completely altering the chemical nature of a molecule critical to obtaining an advantageous technical effect, in this case the sterol referred to in claim 1 at issue, which is normally lipophilic to make it water-soluble by attachment thereto of a long hydrophilic chain, is neither the way the cautious skilled person would normally proceed, nor the best manner for increasing his/her hope to succeed. Therefore, the (not completely unexpected) failure reported in paragraph [0028] of the patent cannot be considered as a proof against the fact that substantially all the claimed QS21/sterol adjuvants deliver the described advantages.

51. The only issue left to be decided is thus to whether or not the prior art rendered obvious to the skilled person to add to the immunogenic QS21 compositions of document (6) a sterol in the ratio indicated, i.e. QS21:sterol from 1:1 to 1:100 (w/w), in order to solve problems (i) and (ii) stated in point 37 supra.

52. Document (D6) does not propose any solution to problems (i) and (ii), let alone the sterol-based one. Only document (D12) (see page 529, last line to page 530, first line) proposes a solution for overcoming drawback (i) (hydrolysis) by using a lower pH and a higher QS21 concentration in the formulation, however, this points to another direction than the solution stated in claim 1.

53. Furthermore, as stated in point 26 above, certain cited documents disclose saponin, i.e. Quil A, containing immunogenic compositions which contain a sterol, inter alia documents (D1), (D8) and (D18). Documents (D8) and (D18) disclose, however, the sterol to be essential for the formation of Iscom's (see document (D8), page 2 line 37 and document (D18), abstract). Accordingly, these documents disclose the use of sterol in Quil A containing immunogenic preparations for a different purpose. Similarly, document (D1) discloses the use of cholesterol in Quil A-containing immunogenic compositions in the form of liposomes. The document is however silent as to the purpose of the addition of cholesterol.

54. In summary the board concludes that the use of sterols in QS21-containing immunogenic preparations as claimed for achieving increased hydrolysis stability and decreased toxicity of QS21, while retaining the adjuvant activity thereof has not been rendered obvious to the skilled person by any prior art document or combination thereof. The claims of the main request also satisfy the requirements of Article 56 EPC.