T 0767/95 (Interleukin 1/IMMUNEX CORPORATION) 05-09-2000

1. The appeal is admissible

Main request Right to priority

2. The respondent maintains that the claimed subject-matter can only base its priority on document (P3) filed 26 November 1984 because the respondent had no sequenceable IL-1ß before that date. However, the board observes that the sequence stated in claim 1 of the patent in suit Ser-Leu-Val-Met-Ser-Gly-Pro-Tyr-Glu-Leu-Lys-Ala- Leu-His-Leu-Gln-Gly-Gln-Asp-Met-Glu-Gln-Gln-Val-Val-Phe is to be found on page 10 of priority document (P2) filed on 27. July 1984, upon which the priority of the claimed subject-matter is thus validly based. As a consequence, the Fourth International Lymphokine Workshop held on 17 to 21 October 1984 at Schloß Elmau in Klais/Oberbayern (FRG)), the content of which the appellant maintains to be given in document (9), is not citable as prior art.

Novelty over documents (1) to (3)

3. It has to be established whether or not the LP preparation of documents (1) or (2), or the IL-1 as it is named in document (3) exhibit features (a) to (c) stated in claim 1 of the patent in suit.

4. As for feature (a), ie the molecular weight, the board cannot accept the appellant's proposition that the difference in mw (15 kd of document (1) compared with 17.5. kd of claim 1) is not significant. While it is true that Fig. 1, track B of document (1) shows a protein with a possible mw of 15,000 d after gel filtration, the mw of the LP preparation in Fig. 1, track D has shifted to a mw less than that of the cytochrome C standard (mw = 12,382 d) following immunoadsorbtion (compare tracks B, C and D of Fig. 1, taking into account that the mw's increase rightwards). Thus, a correct comparison is not 15 kd of document (1) compared with 17.5 kd of claim 1 but rather < 12,382 with 17,500. Therefore, the conclusion cannot be drawn that document (1) discloses a protein having a mw of 17,5 kd as stated in claim 1 of the patent in suit.

5. As regards feature (b), namely a pI of about 5.9-6.3 when solubilised in a buffer comprising 2% (w/v) SDS and 2% (v/v) 2-mercaptoethanol prior to electrophoresis, it has to be noted that document (1) relates to a "pool I" which contains all the pyrogen activity and which gives upon IEF three proteins having pI = 4.7, 5.6 and 7.0 (see page 4626, l-h column). Moreover, the pI value depends on the particular conditions used for performing the IEF SDS-PAGE. A higher SDS concentration renders the protein more acidic (more negative groups). In view of this, a comparison between the pI's of the LP material referred to in document (1) with the claimed one is not possible. Therefore, the appellant's proposition that the pI of 5.9-6.3 recited in claim 1.b is an aberration due to contamination or a different procedure, fails.

6. Feature (c) of claim 1 states a partial amino acid sequence, the requirements that IL-1ß be detected as a single band by SDS-PAGE and silver staining, and be sufficiently homogeneous to have the above noted amino acid sequence determined by Edman degradation. The appellant maintains that Fig. 5 of document (1) discloses homogeneous highly purified IL-1ß because it represents an IEF SDS-PAGE showing a single peak of radioactivity at pI = 7.0-7.1, which in turn yields a single peak when subjected to RP-HPLC chromatography (see page 4626, r-h column of document (1): "Further evidence that labelled LP was homogeneous was confirmed ...under high pressure gradient of CH3CN/10mM KH2PO4...a single peak of radioactivity was observed"). However, the board notes that the major peak in Fig. 5 has a distinct shoulder indicative of more protein species. Furthermore, it is possible to deduce from Fig. 2 on page 5 of document (12), a review of studies on "Endogenous Pyrogens" originating from the same author, that the result of subjecting this single peak from IEF SDS-PAGE to RP-HPLC chromatography step is a peak with a great many shoulders. Therefore, both Fig. 5 of document (1) and Fig. 2 of document (12) suggest a mixture of proteins for the LP material. The semipurified nature of the LP preparation is indeed confirmed by the following statements to be found in the scientific literature : "It was clear that the homogeneous band of the pyrogen consisted of at least three proteins" (document (1), page 4626, l-h column); "one cannot rule out the presence of interfering substances" (document (12), page 6); "However, there is no analysis of the amino acid sequence of IL-1 that would provide definitive proof of the homogeneity of IL-1 preparations" (document (3), page 55, r-h column; emphasis added). There was thus a blockage preventing the skilled person from sequencing the LP material of documents (1) or (2), or the IL-1 of document (3). Regardless of whether it arose from the semipurified nature of these preparations or from the process yielding only traces of the protein, this blockage prevented the teaching of documents (1), (2) or (3) from making available to the public a protein having technical feature (c) of claim 1.

7. In conclusion, since there is no evidence before the board that the LP material of documents (1) or (2) or the IL-1 of document (3) exhibit features (a) and (c) of claim 1 of the patent in suit, these documents do not affect the novelty thereof.

8. The appellant submits that the claimed protein is no more purified than the protein disclosed in document (1). In support of his proposition, arguments are provided inter alia about a peer review of the manuscript underlying document (9) by a respondent's scientist. In the board's judgement, however, it is the appellant who carries the burden of proof regarding facts barring patentability. Since the appellant failed to provide any corroborating evidence, these unsubstantiated allegations must be disregarded and the patent proprietor has to be given the benefit of doubt.

Novelty over document (4)

9. Document (4) is a European patent application enjoying a first priority date earlier than that of (P2) (see point 2 supra) and is thus prior art according to Article 54(3) EPC. It does not disclose a purified mature IL-1ß protein as stated in claim 1 of the patent in suit but merely relates to the inactive precursor of interleukin-1ß having a mw of 30 kd (page 7, line 3). Potential signal sequence cleavage sites are given between Ala8 and Ser9 and between Lys210 and Met211 (page 8, lines 18, 22 and 23). However, even assuming that document (4) enables the skilled person to cut the precursor protein at these sites, no mature IL-1ß as stated in claim 1 of the patent in suit would be obtained because these cutting sites have turned out to be wrong.

10. In view of the above findings, the novelty of the subject-matter of claim 1 has to be accepted. Since claims 2 to 12 all rely on the novel IL-1ß of claim 1, they have equally to be considered novel.

Inventive step

11. The board views document (1) as representing the closest prior art (documents (2) and (3) disclose essentially the same subject-matter as document (1)). However, the "LP" material of document (1) was not pure. The patent in suit addresses the problem of providing homogenous IL-1ß for inter alia clinical investigations and a process for its preparation. The board accepts that the patent solves the above problem. It has thus to be established whether or not homogenous IL-1ß and the process for its preparation follow in an obvious fashion from the prior art.

12. The appellant argues (see page 7 of the notice of appeal, 5th paragraph, case (3)) that "a purified protein can be patentable over a crude preparation thereof if no method was known for purifying the impure protein" and that "pure IL-1ß was an obvious desideratum, satisfied once a suitable purification technique became available" (ibidem, paragraph 4). The board agrees. As, on the evidence, the provision of homogenous IL-1ß for inter alia clinical investigations was only possible by solving the problem of developing a suitable purification technique, an inventive step can here be acknowledged for the provision of homogenous IL-1ß if the purification technique stated in claim 2 of the patent in suit does not follow in an obvious way from the prior art. Thus, contrary to the appellant's view, the purified protein need not exhibit unexpected advantageous properties over the protein of document (1) to be inventive, should the process for its preparation not be obvious.

13. The appellant maintains in essence that the skilled person would adopt the procedure disclosed in document (5) involving chromatography on dye ligands (procion red agarose) for separating interleukin-2 from contaminants in order to further purify the LP material of document (1). There was a high expectation of success in obtaining homogenous IL-1ß by applying this technique since IL-2 and IL-1ß were known to have the same size and pI and were expected to be contaminated by the same proteins (lymphokines) given their biological activity and origin.

However, according to document (5), "The binding of IL-2 to these dyes is likely a result of the electrostatic or hydrophobic interactions" (page 460, last paragraph) and "Lymphokines...such as IL-1, -interferon, ß-interferon,... have different capabilities of forming hydrophobic interactions. We have exploited these properties to separate IL-2 from other lymphokines..." (top of page 461). These passages demonstrate that IL-2 and IL-1ß behave differently vis-à-vis chromatography on a dye ligand. Therefore, the skilled person reading document (5) would not have been motivated to adopt this technique for separating IL-1ß from contaminants. Consequently, the process of claim 2 and the homogeneous IL-ß of claim 1 fulfil the requirements of Article 56 EPC. Since claims 3 to 12 all rely on the inventive homogeneous IL-1ß of claim 1 or inventive process of claim 2, their inventive step has equally to be accepted.

14. The board is satisfied that the claims of the main request meet the requirements of the EPC. No need arises to consider the "First Auxiliary request" or the "Second Auxiliary request".