T 0309/99 (Ultrasonic imaging agent/MOLECULAR BIOSYSTEMS) 17-09-2004

Summary of Facts and Submissions

I. This appeal is against the decision of the opposition division posted on 28 January 1999 to revoke European patent No. 0 324 938 ("the patent") based on European patent application No. 88 120 371.5 and concerning a "Concentrated stabilized microbubble-type ultrasonic imaging agent and method of production". Opposition was filed by the respondent against product claims 1 to 9 as granted, which all are directed to an ultrasonic imaging agent as such, on the grounds of lack of inventive step (Articles 56 and 100(a) EPC), lack of industrial applicability (Articles 57 and 100(a) EPC), and insufficient disclosure (Articles 83 and 100(b) EPC). None of the method claims 10 to 14 have been attacked in the notice of opposition. The claims of the patent as granted read as follows:

"1. A concentrated room-temperature stable ultrasonic imaging agent comprising a parenterally administrable aqueous medium containing a dispersion of microspheres at least 80% of which have diameters in the range of 1 to 9 µm, said microspheres consisting of gas microbubbles encapsulated in a water-insolubilized heat-denaturable biocompatible protein, said imaging agent having a homogeneously dispersed concentration of greater than 100 x 10/6 microspheres per ml and maintaining this concentration for over 4 weeks at a temperature of 20 to 25°C.

2. The imaging agent of claim 1 which has a homogeneously dispersed concentration of said microspheres greater than 200 x 10/6 microspheres per ml and which maintains this concentration for over 4 weeks at a temperature of 20 to 25°C.

3. The imaging agent of claim 1 in which said microbubbles are encapsulated with human serum albumin.

4. The imaging agent of claim 1 in which said microspheres are suspended in an aqueous solution of the same protein in which the microbubbles are encapsulated.

5. The imaging agent of claim 4 which has a homogeneously dispersed concentration of from 300 to 600 x 10/6 microspheres per ml, and which maintains such concentration for at least 8 weeks at a temperature of 20 to 25°C.

6. The imaging agent of claim 4 or claim 5 in which said protein is human serum albumin.

7. The imaging agent of claim 4 or claim 5 in which 90% or more of said microspheres have diameters in the range from 2 to 8 µm.

8. A concentrated room-temperature stable ultrasonic imaging agent for intravenous administration, comprising a sterile aqueous solution of human serum albumin containing a dispersion of microspheres at least 80% of which have diameters in the range of 1 to 9 µm, said microspheres consisting of a bubble of air encapsulated in a water-insolubilized layer of said albumin, said imaging agent having a homogeneously-dispersed concentration of from 300 to 600 x 10/6 microspheres per ml and maintaining this concentration for at least 8 weeks at a temperature of 20 to 25°C.

9. The imaging agent of claim 8 in which at least 90% of said microspheres have diameters in the range of 2 to 8 µm.

10. A method of producing a dispersion of microspheres according to any of claims 1 to 9 for use as an ultrasonic imaging agent in which an aqueous solution of a heat-denaturable biocompatible protein is subjected to sonication to form gas microbubbles while heating said solution to insolubilize a portion of the protein, wherein the improvement comprises: during an initial sonication phase directly contacting the tip of the sonicator horn with said solution and carrying out the sonication and heating of said solution without appreciable foaming, then withdrawing the sonicator horn to a position in the ambient atmosphere proximate to the surface of said solution and foaming the solution to increase the population of microbubbles, and encapsulating the microbubbles with denatured protein to obtain a dispersion of stabilized microspheres of increased concentration.

11. The method of claim 10 in which said protein is human serum albumin.

12. A method of producing a concentrated dispersion of microspheres for use as an ultrasonic imaging agent in which a solution of human serum albumin is subjected to a sonication process according to claim 10, wherein the improvement comprises holding a body of the thus-obtained microsphere dispersion without agitation for sufficient time to permit the microspheres to rise therein and concentrate in an upper layer above the clarified albumin solution, and separating a portion of the clarified albumin solution from the concentrated layer to obtain a dispersion of greater microsphere concentration.

13. The method of claim 12 in which said dispersion of greater concentration is fractionated by withdrawing a dispersion containing most of the microspheres while leaving behind a microsphere fraction containing the largest size microspheres which had collected near the upper surface of the dispersion.

14. The method of claim 12 in which at least 80% of said microspheres have diameters in the range from 1 to 9 µm but include microspheres of larger diameters, which method includes the further steps of holding a body of the microsphere dispersions without agitation for sufficient time to permit at least the microspheres of larger than 10 µm diameter to rise therein and concentrate in an upper layer, and withdrawing a dispersion from beneath said upper layer containing most of the microspheres of less than 10 µm diameter while leaving behind a microsphere fraction containing most of the microspheres of larger than 10 µm diameter."

II. Of the numerous documents cited in the course of the first instance opposition and subsequent appeal proceedings, the following are referred to in this decision:

(4) EP-A-0 224 934;

(5) M. W. Keller et al, "Successful left ventricular opacification following peripheral venous injection of sonicated contrast agent: An experimental evaluation", Am. Heart J. 114, 1987, pp 570-575.

III. At the close of the oral proceedings, held on 7 December 1998, the opposition division decided that the claimed subject- matter in the patent as granted, although complying with Articles 57 and 83 EPC and being novel, lacked an inventive step. The essence of the reasoning in the opposition division's decision was as follows:

There was general agreement that citation (4) represented the closest state of the art. This citation disclosed a contrast agent for ultrasonic imaging in the form of an aqueous protein solution comprising microbubbles (microspheres) produced by subjecting an aqueous solution of human serum albumin (HSA) to high- frequency ultrasonic energy. Of the microbubbles produced, approximately 9.5 x 10/6/ml of solution were in the 2-6 micron range, and relatively negligible amounts of microbubbles in the range above 6 microns were formed (see (4) especially bottom of page 7). As an alternative to denaturation of the protein layer of the microbubbles already resulting from development of heat during sonication, the protein could be further denaturated and the microspheres stabilized by an additional heat treatment at a temperature in the range of 50 to 60°C. The microspheres formed from a 5% aqueous albumin solution which had been sonicated and stabilized existed for 48 hours or longer (see (4), page 8, penultimate paragraph). Such microspheres could successfully be used for left ventricular opacification following peripheral venous injection and eliminated the air embolism toxicity risks inherent in this diagnostic method.

Citation (5), of which the inventor of (4) was a co- author, also reported successful left-ventricular opacification by the injection of microspheres obtained by a sonication process similar to that descried in (4). The mean particle size of the microspheres of (5) was below 9 µm and the mean concentration 22 x 10/6 microspheres/ml, although even higher concentrations up to 30-50 x 10/6 microspheres/ml would appear to be achievable by the sonication method disclosed in (5).

The opposition division then specifically pointed to the following statements in (5), namely that "the indicator-dilution analysis used indicated a linear relationship between bubble concentration and ultrasound backscatter" and that "further development and standardization techniques will certainly yield microbubbles more uniform in size and more stable".

The opposition division found that the only difference between the claimed subject-matter and the prior art of (4) and (5) was the higher concentration of microspheres/ml in the ultrasonic imaging agent in the patent. It emphasised that, according to the respondent's own submissions, a direct relationship between stability and concentration of the microspheres existed. This led the opposition division to infer in the decision under appeal that the "figures of concentration and stability duration are arbitrarily chosen over those known from the prior art" (see bottom of page 11 of the decision.

On the basis of its analysis of the cited state of the art the opposition division reached the conclusion that citation (4) had disclosed the use of high concentrations of microbubbles in ultrasonic imaging agents and that citation (5) clearly suggested to those skilled in the art that even higher concentrations might be highly desirable to improve the ultrasonic contrast. Moreover, in the opinion of the opposition division, those citations had already taught that a direct relationship existed between the stability of the microspheres and their concentration in the ultrasonic imaging agent. The opposition division concluded therefrom that the claimed ultrasonic imaging agent was the result of an obvious combination of the teachings of citations (4) and (5) and thus devoid of an inventive step. This was all the more so, because the use of a similar type of microbubbles was reported in (4) to eliminate the air embolism toxicity risks inherent in the administration of ultrasonic contrast agents and therefore the alleged technical prejudice against using the claimed contrast agents in the patent no longer existed.

IV. The proprietor (appellant) filed a notice of appeal and paid the appeal fee on 18 March 1999 and filed a statement of grounds of appeal on 28 May 1999. The respondent requested a two month extension of time to respond to the statement of grounds of appeal in a letter of 27 September 1999 and a further two month extension of time in a letter of 22 November 1999.

V. By a letter dated 1 December 1999, the Registrar of the board notified the parties of the board's refusal of the respondent's request for a second extension of time. In a communication of 10 December 1999, sent in response to a telephone call of 10 December 1999 by the respondent's representative to the Registrar, detailed reasons were given why the board had decided not to grant the further extension.

VI. In response to the summons to oral proceedings, scheduled for 22 January 2003, the respondent's representative informed the board in a letter of 16 December 2002 that the respondent would neither be present nor represented at those oral proceedings.

VII. In advance of the oral proceedings the appellant filed by facsimile of 10 January 2003, less than two weeks before the date fixed for the hearing before the board, further observations and three amended sets of claims forming its first, second and third auxiliary requests.

VIII. The independent product claim 1 of the first auxiliary request reads as follows, with the sole amendment indicated below in bold italic letters:

"1. A concentrated room-temperature stable ultrasonic imaging agent comprising a parenterally administrable aqueous medium containing a dispersion of microspheres at least 80% of which have diameters in the range of 1 to 9 µm, said microspheres consisting of gas microbubbles encapsulated in human serum albumin, said imaging agent having a homogeneously dispersed concentration of greater than 100 x 10/6 microspheres per ml and maintaining this concentration for over 4 weeks at a temperature of 20 to 25°C.

The independent product claim 1 of the second auxiliary request reads as follows, with the sole amendment indicated below in bold italic letters:

"1. A concentrated room-temperature stable ultrasonic imaging agent comprising a parenterally administrable aqueous medium containing a dispersion of microspheres at least 80% of which have diameters in the range of 1 to 9 µm, said microspheres consisting of gas microbubbles encapsulated in a water-insolubilized heat- denaturable biocompatible protein, said imaging agent having a homogeneously dispersed concentration of greater than 200 x 10/6 microspheres per ml and maintaining this concentration for over 4 weeks at a temperature of 20 to 25°C."

IX. The product claims 1 to 5 of the third auxiliary request read as follows, with the amendments in claim 1 indicated below in bold italic letters:

"1. A concentrated room-temperature stable ultrasonic imaging agent comprising a parenterally administrable aqueous medium containing a dispersion of microspheres at least 80% of which have diameters in the range of 1 to 9 µm, said microspheres consisting of gas microbubbles encapsulated in a water-insolubilized heat- denaturable biocompatible protein, and being suspended in an aqueous solution of the same protein in which the microbubbles are encapsulated, said imaging agent having a homogeneously dispersed concentration of from 300 to 600 x 10/6 microspheres per ml and which maintains such concentration for at least 8 weeks at a temperature of 20 to 25°C.

2. The imaging agent of claim 1 in which said microbubbles are encapsulated with human serum albumin.

3. The imaging agent of claim 1 in which 90% or more of said microspheres have diameters in the range from 2 to 8 µm.

4. A concentrated room-temperature stable ultrasonic imaging agent for intravenous administration, comprising a sterile aqueous solution of human serum albumin containing a dispersion of microspheres at least 80% of which have diameters in the range of 1 to 9 µm, said microspheres consisting of a bubble of air encapsulated in a water-insolubilized layer of said albumin, said imaging agent having a homogeneously-dispersed concentration of from 300 to 600 x 10/6 microspheres per ml and maintaining this concentration for at least 8 weeks at a temperature of 20 to 25°C.

5. The imaging agent of claim 4 in which at least 90% of said microspheres have diameters in the range of 2 to 8 µm."

The method claims 6 to 10 correspond to the method claims 10 to 14 as granted, with the dependencies amended as necessary.

X. Oral proceedings before the board were held in the absence of the respondent as provided for in Rule 71(2) EPC. At the end of the hearing, the board decided to continue the proceedings in writing, in accordance with directions to be given in a communication, in order to give the absent respondent the opportunity to present its comments on the appellant's late-filed auxiliary requests.

XI. In the said communication, sent on 27 January 2003, the board informed the parties that it had become clear during the oral proceedings that the board would be unlikely to allow the appellant's main request filed with the statement of grounds of appeal (maintenance of the patent in the form as granted), or its first or second auxiliary request. In the board's judgment, it appeared unclear whether, in assessing inventive step using the problem/solution approach, the problem as discussed during the oral proceedings had, according to claim 1 of the above-mentioned requests, been shown to be solved across the whole range. As a result of the discussion of the case at the hearing, it appeared, however, that the above objection would not arise as regards the claims of the third auxiliary request. However, the board considered the auxiliary requests filed with the appellant's facsimile of 10 January 2003 to be prima facie inadmissible by reason of being filed so late that, if one of those requests was indeed held to be admissible without giving the respondent an opportunity to comment on them, it might be said the respondent had been prejudiced.

The board made the following directions in its communication:

"1. The proceedings shall be continued in writing only for the purpose of giving the respondent an opportunity to comment on the allowability of the auxiliary requests. If it so wishes, it should file written observations to be received no later than two months after the deemed date of receipt of this communication.

2. If the respondent does file such observations, the appellant should file any observations in reply, and limited to replying thereto, to be received within two month after the deemed date of receipt from the board of the respondent's observations.

3. The time limits in 1 and 2 above will not be extended.

4. No submissions of any kind and no new evidence or requests (including requests for further oral proceedings) from either party will be considered.

5. The board's decision will include an order for apportionment of costs so that the appellant pays any costs incurred by the respondent after 10 January 2003. It follows from the above that those costs will be limited to only those reasonable costs properly incurred by the respondent in complying with these directions.

6. Since the continuation of the appeal proceedings will have the effect of continuing the period during which the effect of the decision under appeal is suspended (Article 106(1) EPC), the appellant has undertaken not to start any infringement proceedings on the patent in suit until the effective date of the board's decision."

XII. In its reply of 24 March 2003 to the board's communication (i.e. the first submission of the respondent in the course of the appeal proceedings), the respondent argued essentially as follows:

The first and second auxiliary requests did not appear to improve the appellant's position over the main request, since the only enabling disclosure in the patent was to a process that inevitably resulted in a suspension of the protein microcapsules in the protein solution that had been sonicated. The microcapsules could not be separated from the solution and either presented dry or suspended in another liquid. A suspension of the microcapsules in a solution of their own protein was the only product for which the appellant had any evidence of stability. This issue applied to albumin in accordance with the first auxiliary request just as much as to any other protein. In addition, as the respondent's experimental reports had shown, concentrations at the lower end of the concentration range (ie below 300 x 10/6/ml) in claim 1 as granted were not stable. Hence, the second auxiliary request was also not acceptable.

However, the respondent did not wish to object to claims 1 to 3 of the appellant's third auxiliary request (see IX above). However, it did object to claims 4 and 5 of the third auxiliary request (again, see IX above), since they were, in the respondent's opinion, not limited to the microspheres being suspended in a solution of the same protein as was used to prepare and encapsulate the microbubbles. It appeared that the omission of this feature from claims 4 and 5 of the third auxiliary request was an oversight, since the appellant's description of this claim request on page 2 of its letter of 10 January 2003 indicated that the request was supposed to be "a combination of claims 1, 4 and 5 as granted" and that "the microspheres are stated as being suspended in an aqueous solution of the same protein (in) which the microbubbles are encapsulated".

If the appellant amended its third auxiliary request to delete claims 4 and 5, or to make these dependent on claim 1, and made this his only claim request, then the respondent would withdraw its opposition.

XIII. In a further communication of 16 March 2004 the board repeated its view that the main request (maintenance of the patent with the claims as granted) and the first and second auxiliary requests would not appear to be acceptable for the reasons summarised in paragraph 2 of its previous communication of 23 January 2003. In this second communication, the board also remained of the view that the claims of the third auxiliary request did not suffer from this objection and were potentially allowable. In this respect the board noted that the respondent had submitted it would withdraw its opposition if the third auxiliary request was amended as set out in XII above, last paragraph.

The board communicated to the parties its opinion that, if the matter was capable of resolution on terms the parties could agree and which the board could in the public interest approve, then such a resolution should be advanced. Further, if the parties agreed on a single request, the board would have to give effect to that agreement by ending the appeal proceedings (T 615/96 of 13 November 2001, unpublished in OJ EPO). Although the respondent had indicated it would withdraw its opposition and thus cease for almost all purposes to be a party to the proceedings, it should remain a party in order for the condition of identity of pending requests to be satisfied. Both parties should also find it in their interest to have a formal decision and order - in the respondent's case to be able to enforce the order for an apportionment of costs and, in the appellant's case, to have confirmation that its undertaking of 22 January 2003 (not to take infringement proceedings until the effective date of the board's decision) was discharged.

Accordingly, the board's previous direction that no further requests would be considered was modified to the extent necessary to accommodate the following further directions: "Within two months of the deemed date of receipt of this communication:

- the appellant, if it so wishes, should file a request (called "sole request") in the form of the third auxiliary request filed on 10 January 2003 amended in one of the ways indicated by the respondent, withdraw its other requests and file its written consent to an order being made by the board in the terms of the annexed draft;

- the respondent, if it so wishes, should file its written consent to the "sole request" and to an order being made by the board in terms of the annexed draft."

The draft order annexed to the communication read as follows:

"1. The decision under appeal is set aside.

2. The case is remitted to the first instance with the order to maintain the patent on the basis of the claims in the request entitled "sole request" filed on (....... full date to be inserted when known).

3. The respondent's costs shall be apportioned so that the appellant pays to the respondent £ 494 (the sum to be paid was expressed in pounds sterling since it appeared the parties had agreed a sum in that currency).

4. The undertaking given to the board by the appellant on 22 January 2003, not to start any infringement proceedings on the patent in suit until the effective date of the board's decision, is hereby discharged (the effective date of the decision and thus the date of the discharge of the undertaking, would be the date the decision is given to the EPO postal service, see G 12/91, OJ EPO 1994, 285)."

At the end of this communication, the board made it unambiguously clear that, if the above directions were not complied with within the time indicated above, it would proceed to prepare and issue a decision on the basis of the materials then on file.

XIV. In its reply of 6 May 2004, the appellant indicated that there were four requests on file. These were the main request and its first, second and third auxiliary requests. It emphasised, however, that it would be prepared to file the third auxiliary request as a sole request (but not amended in one of the ways indicated by the respondent), if this assisted the board in these proceedings. It further noted that claim 4 of the third auxiliary request was originally claim 8 in the granted patent and it seemed that the respondent only commented on the third auxiliary request when invited to do so by the board in January 2003. It likewise appeared that the board had not specifically commented either, in a positive or negative manner, on the patentability of claim 4 of the third auxiliary request.

The respondent essentially argued in its reply to the board's communication that the technical feature of keeping the microspheres in a solution of the same protein from which they were made appeared to be essential for stability. This feature was present in claim 1 of auxiliary request 3 but was, in the respondent's opinion, not present in independent claim 4 of auxiliary request 3. This was why it continued to oppose it and could not withdraw the opposition.

XV. In view of the foregoing the following requests are on file:

The appellant requests that the decision under appeal be set aside and that the patent be maintained on the basis of its main request or its first, second or third auxiliary request in that order.

The respondent requests that the appeal be dismissed.