T 0611/19 () of 6.11.2023

Summary of Facts and Submissions

I. Both the opponent and the patent proprietor filed an appeal against the interlocutory decision of the opposition division to maintain European patent No. 2 305 173 on the basis of auxiliary request 15, which had been filed during the oral proceedings on 8 October 2018.

II. Oral proceedings before the board took place on 6 November 2023.

III. The appellant (opponent) requested that the decision under appeal be set aside and that the patent be revoked.

The other appellant (patent proprietor) requested that the decision under appeal be set aside and that the patent be maintained on the basis of the main request as filed on 24 October 2023 or on the basis of one of auxiliary requests 1 to 19 as filed with the patent proprietor's statement of grounds of appeal or on the basis of auxiliary request 20 as filed with the patent proprietor's letter dated 1 November 2023.

IV. Claim 1 of the main request reads as follows:

"A flow cytometry system for sorting a mixture of particles including particles having a characteristic A and particles having a characteristic B, the system including a fluid delivery system for delivering a fluid containing the particles, a flow cytometry apparatus for receiving the fluid, forming it into a stream and using flow cytometry to classify the particles according to the characteristics, and a sorting system including a laser for ablating selected particles in the stream according to the classification and according to a sorting strategy to provide at least one population containing desired particles, the system being characterised in that it includes:

a control responsive to information received from the flow cytometry apparatus for controlling the fluid delivery to vary the rate at which fluid is delivered as a function of at least one of the following:

(1) the purity of the at least one population with respect to either characteristic A particles or characteristic B particles; and

(2) the quantity of unablated characteristic A particles or unablated characteristic B particles in the said at least one population relative to the total quantity of characteristic A particles or characteristic B particles in the stream."

Claim 14 of the main request reads as follows:

"A method of using a flow cytometry system to sort a mixture of particles including particles having a characteristic A and particles having a characteristic B, the method including:

providing a flow cytometry apparatus;

delivering a fluid containing the particles;

forming the fluid into a stream and using flow cytometry to classify the particles in the stream according to the characteristics;

sorting the particles in the stream by ablating selected particles according to the classification and according to a sorting strategy thereby to provide at least one population containing desired particles; and

varying the rate at which fluid is delivered as a function of at least one of the following:

(1) the purity of the said at least one population with respect to either characteristic A particles or characteristic B particles; and

(2) the quantity of unablated characteristic A particles or unablated characteristic B particles in the said at least one population relative to the total quantity of characteristic A particles or characteristic B particles in the stream."

Claim 1 of auxiliary request 15 reads as follows:

"A flow cytometry system for sorting a mixture of particles including particles having a characteristic A and particles having a characteristic B, the system including a fluid delivery system for delivering a fluid containing the particles, a flow cytometry apparatus for receiving the fluid, forming it into a stream and using flow cytometry to classify the particles according to the characteristics, and a sorting system including a laser for ablating selected particles in the stream according to the classification and according to a sorting strategy to provide at least one population containing desired particles, the system being characterised in that it includes:

a control responsive to information received from the flow cytometry apparatus for controlling the laser to vary its sorting strategy or for controlling the fluid delivery to vary the rate at which fluid is delivered as a function of the purity of the at least one population with respect to either characteristic A particles or characteristic B particles."

Claim 1 of auxiliary request 20 reads as follows:

"A flow cytometry system for sorting a mixture of particles including particles having a characteristic A and particles having a characteristic B, the system including a fluid delivery system for delivering a fluid containing the particles, a flow cytometry apparatus for receiving the fluid, forming it into a stream and using flow cytometry to classify the particles according to the characteristics, and a sorting system including a laser for ablating selected particles in the stream according to the classification and according to a sorting strategy to provide at least one population containing desired particles, the system being characterised in that it includes:

a control responsive to information received from the flow cytometry apparatus for controlling the fluid delivery to vary the rate at which fluid is delivered as a function of the purity of the at least one population with respect to either characteristic A particles or characteristic B particles."

Claim 2 of auxiliary request 20 reads as follows:

"A flow cytometry system for sorting a mixture of particles including particles having a characteristic A and particles having a characteristic B, the system including a variable rate fluid delivery system for delivering a fluid containing the particles, a flow cytometry apparatus for receiving the fluid, forming it into a stream and using flow cytometry to classify the particles according to the characteristics, and a sorting system including a laser for ablating selected particles in the stream according to the classification and according to a sorting strategy to provide at least one population containing desired particles, the system being characterised in that it includes:

a control responsive to information received from the flow cytometry apparatus for controlling the fluid delivery to vary the rate at which fluid is delivered as a function the purity of the said at least one population with respect to either characteristic A particles or characteristic B particles."

V. The following documents are referred to in this decision:

D1 J. F. Keij et al., "High-Speed Photodamage Cell

Sorting: an Evaluation of the ZAPPER Prototype",

Methods in Cell Biology, vol. 42, chapter 22, 1994

D2 J. F. Keij et al., "High-Speed Photodamage Cell

Selection Using a Frequency-Doubled Argon Ion

Laser", Cytometry, 19, 1995, 209-216

D7 J. F. Keij et al., "Coincidence in High-Speed Flow

Cytometry: Models and Measurements", Cytometry,

12, 1991, 398-404

D15 M. J. McCutcheon et al., "Flexible Sorting

Decision and Droplet Charging Control Electronic

Circuitry for Flow Cytometer-Cell Sorters",

Cytometry, 2, 1981, 219-225

D16 US 5,199,576 A

VI. The arguments of the opponent can be summarised as follows:

Main request and auxiliary request 20 - admittance

The main request and auxiliary request 20 should not be admitted into the appeal proceedings since they did not meet the requirements of Article 13(1) and (2) RPBA.

The novelty issue to which the patent proprietor responded with claim 1 of the main request and claim 1 of auxiliary request 20 had been discussed right from the outset of the appeal proceedings. The opinion of the board expressed in its communication could not be considered exceptional circumstances for filing new requests. On the contrary, the fundamental principle of Article 13(2) RPBA was that amendments made to a party's case at such a late stage of the appeal proceedings should not generally be allowed.

Furthermore, the amendments could not be considered to restrict the case to previously presented claims since the subject-matter defined in the independent claims of the main request and auxiliary request 20 had not previously been independently pursued in any request.

In any case, the new requests did not resolve all of the issues raised; in fact, they gave rise to new objections. The main request also included an independent method claim (claim 14) which was broader than the apparatus claim and required a separate substantive evaluation of its patentability. It had been found that the subject-matter of claim 14 of the main request lacked novelty over D7 and lacked an inventive step in view of D15.

Auxiliary request 20 lacked an inventive step in view of D7. Thus, these documents should not be admitted into the appeal proceedings. Additionally, objections of added subject-matter and a lack of clarity also had to be raised against auxiliary request 20.

Moreover, the objections raised against the second option of claim 1 of the previous main request also applied to the subject-matter of the new main request and auxiliary request 20.

Hence, the admittance of these requests would be detrimental to procedural economy since they were not prima facie allowable. Consequently, the main request and auxiliary request 20 also failed to meet the requirements for admittance as set out in Article 13(1) RPBA.

Auxiliary requests 1 to 14 and 16 to 19 - admittance

The opponent did not provide any comments on auxiliary requests 1 to 14 and 16 to 19.

Auxiliary request 15 - novelty over D16

The subject-matter of claim 1 of auxiliary request 15 lacked novelty over D16.

In particular, D16 disclosed a flow cytometry system having a control responsive to information received from the flow cytometry apparatus. As shown in Figure 5 and described in column 8, lines 14 to 18, the sorter provided "individual sort/no sort decisions from conventional cell sorter". Column 15, lines 1 to 34, set out "how the algorithm uses information from the cell sorter operation which include individual sort or no sort decision from the traditional sort control 10", i.e. the assigned characteristic. It was also described in this passage that the algorithm optimised the yield/purity ratio according to the information received. Hence, D16 disclosed the use of pre-sort data for varying the sorting strategy.

Moreover, D16 also disclosed a laser ablation system. In particular, D16 explicitly mentioned in column 15, lines 62 and 63, the possibility of zapping as a method for destroying particular cells instead of droplet sorting. In the field of flow cytometry, "zapping" was a term in the art for laser ablation sorting.

Hence, D16 disclosed all of the features of claim 1 of auxiliary request 15. Consequently, the subject-matter of claim 1 of auxiliary request 15 lacked novelty.

VII. The arguments of the patent proprietor can be summarised as follows:

New main request and auxiliary request 20 - admittance

The claims of the main request and auxiliary request 20 should be admitted into the proceedings since they met the requirements of Article 13(1) and (2) RPBA.

In the case law in relation to new submissions in appeal proceedings it was held that exceptional circumstances within the meaning of Article 13(2) RPBA 2020 generally concerned new or unforeseen developments in the appeal proceedings themselves, such as new objections raised by the board or another party. Exceptional circumstances had been deemed present when objections had been raised for the first time in a board's communication.

The main request and auxiliary request 20 met these requirements since there were exceptional circumstances in view of the communication of the board dated 19 September 2023, in which it was indicated that the removal from claim 1 of the first option, relating to varying the sorting strategy, would render that claim novel and inventive over the cited prior art.

By deleting the first option from the claim, the new requests made the proceedings more expedient since they addressed and prima facie resolved the issues described in the preliminary opinion of the board. Hence, the amendments were not detrimental to procedural economy and did not give rise to new objections as the board had considered the remaining second option to meet the requirements of Articles 83, 54 and 56 EPC.

It had not been necessary to file these requests earlier in the proceedings since the opposition division had held auxiliary request 15 to be allowable. The preliminary opinion of the board, which was also issued at a late stage of the proceedings, was the first time a novelty objection against claim 1 had been made.

Furthermore, according to the case law of the Boards of Appeal, the deletion of an alternative from a claim did not constitute an amendment of a party's appeal case.

Auxiliary requests 1 to 14 and 16 to 19 - admittance

The patent proprietor did not comment on auxiliary requests 1 to 14 and 16 to 19.

Auxiliary request 15 - novelty over D16

D16 did not disclose the feature "a control responsive to information received from the flow cytometry apparatus".

Column 15, lines 29 to 34, of D16 clearly indicated that post-sort information was used to adjust the sorting strategy. To identify whether the sort decision resulted in the correct yield/purity ratio, the output of the sorting system had to be analysed rather than the input.

Furthermore, in the upper right-hand corner of Figure 5 it was clearly indicated that the sort result was sent to the learning algorithm. The term "sort result" had to be interpreted as the actual result of the sort, rather than anything relating to pre-sort data.

The alternative embodiment described in column 15, lines 35 to 40, also related to the use of post-sort information.

Moreover, D16 did not directly and unambiguously disclose that the sorting system included a laser for ablating selected particles since all of the embodiments of the Figures described droplet cell sorting.

Hence, the subject-matter of claim 1 of auxiliary request 15 did not lack novelty over D16.

Reasons for the Decision

1. Subject-matter of the patent

The patent relates to a flow cytometry system and a method for sorting a mixture of particles, for instance sperm cells. Before the sperm cells are fed by the fluid delivery system to the flow cytometry apparatus, they are stained using a DNA-selective dye such that, for instance, male sperm cells have a different colour from female sperm cells. The difference in colour is then used to analyse the cells and to classify them in the flow cytometry apparatus (detector). The cells are then sorted according to their classification in a sorting system using a laser for ablating selected particles in the stream.

The sequence of particles arriving at the sorting system is random, so when viewed as a continuous procession, the particles can be divided into different particle series, one following another, including a first particle series consisting only of one or more particles having characteristic A, a second particle series consisting only of one or more particles having characteristic B and a third particle series consisting of two or more closely spaced particles, at least one of which has characteristic A and at least one of which has characteristic B. The two or more particles in the third series (also referred to as the coincident set) may be closely spaced in the sense that the spatial separation between the particles is insufficient to allow accurate discrimination/classification of the particles, or because such separation is insufficient to permit one particle in the series to be ablated by the laser without damaging the other particle(s) in the same series. The number of these coincident sets increases when the flow rate of the particles is increased. In any event, the closely spaced particles in each (or at least some) of the coincident sets of particles can be ablated or not ablated, depending on the sorting strategy employed.

Different control sorting strategies can be employed in a photo-damage system, including the "high recovery" and "high purity" sorting strategies.

According to claim 1 of auxiliary request 15, the laser is controlled responsive to information received from the flow cytometry apparatus. This information concerns the identity of the particles in a series (characteristic A, characteristic B or coincident (both A and B)) and is used to vary the sorting strategy or the fluid delivery rate as a function of

the (desired) purity of the population with respect to either characteristic A or characteristic B.

In essence, the control of claim 1 deals with the question of whether or not the coincident sets, i.e. the third sets comprising both particles A and B, are sorted out (ablated).

If these coincident sets are sorted out (coincident reject or high purity strategy), the purity of the population of desired particles is kept high. However, a number of desired particles will be lost to the ablated population, thus reducing the recovery rate (yield). In this strategy, the particle delivery rate is inversely related to the percentage of desired particles in the collected population, since the faster the particle sets are delivered the more coincident sets are present in the stream.

On the other hand, if the coincident sets are not ablated but sorted into the desired population (coincident accept or high recovery strategy), the purity of the desired population will suffer while a high recovery rate can be achieved. In this strategy, the particle delivery rate is inversely related to the purity of the collected population of desired particles.

In a third strategy (constant flow rate strategy), the flow rate is kept constant and the percentage of collected (accepted) or ablated (rejected) coincident sets is varied.

2. Main request and auxiliary request 20 - admittance

2.1 The main request was filed by letter dated 24 October 2023 and auxiliary request 20 was filed by letter dated 1 November 2023.

Claim 1 of the main request is based on claim 1 of the previous main request (patent as granted) but the reference to varying the sorting strategy has been removed.

Claim 1 of auxiliary request 20 is based on claim 1 of auxiliary request 15 except here too the reference to varying the sorting strategy has been removed.

Both of these claim requests constitute an amendment to the patent proprietor's appeal case (see, for instance, J 14/19, Reasons 1.3 and 1.4) since one of the alternatives defined in granted claim 1 (control of the sorting strategy or the fluid, each option combined on the basis of purity or quantity of unablated particles or both) has been deleted. Since both requests were filed after the notification of the summons to oral proceedings, Article 13(2) RPBA 2020 applies with respect to the question of whether these requests should be admitted into the appeal proceedings.

2.2 According to Article 13(2) RPBA 2020, which was in force at the time the admittance decision was taken, any amendment to a party's appeal case made after notification of a summons to oral proceedings shall, in principle, not be taken into account unless there were exceptional circumstances which had been justified with cogent reasons by the party concerned, i.e. in the present case by the patent proprietor.

In its communication of 19 September 2023, the board had expressed its provisional opinion on what was then the main request. It considered the first option (varying the sorting strategy) of claim 1 of the main request on file at that time to lack novelty over D16, but the second option (varying the fluid flow rate) was considered novel and inventive. The novelty objection to the first alternative had already been raised in the first-instance proceedings and had been referred to by the opponent in its statement of grounds of appeal. The fact that the board expressed an opinion on this matter has to be regarded as the normal course of events, rather than as new or unforeseen developments that change the facts or circumstances of the case. Hence, the board does not consider there to have been any exceptional circumstances justifying the filing of new requests at this late stage of the proceedings. Rather, the patent proprietor could have filed these requests as possible fallback positions earlier in the proceedings.

In this regard, it is irrelevant when the communication setting out the preliminary opinion of the board was issued. Hence, there are no exceptional circumstances justifying the admittance of the main request and auxiliary request 20.

2.3 Moreover, in applying its discretion according to Article 13(2) RPBA 2020, a board may also apply the criteria set out in Article 13(1) RPBA 2020. According to Article 13(1) RPBA 2020, the board shall exercise its discretion to admit new requests in view of, inter alia, the current state of the proceedings, the suitability of the amendment to resolve the issues admissibly raised by another party in the appeal proceedings, whether the amendment is detrimental to procedural economy, and, in the case of an amendment to a patent, whether the party has demonstrated that any such amendment prima facie overcomes the issues raised by another party in the appeal proceedings or by the board and does not give rise to new objections.

It is acknowledged that the new main request and auxiliary request 20 address the issues mentioned in the preliminary opinion as a result of the first option having been deleted from the independent claims. However, as pointed out by the opponent, the sole option of varying the fluid flow rate according to the independent claims of the new main request and auxiliary request 20 had not previously been pursued in any request.

The board further agrees with the opponent that independent method claim 14 is broader than claim 1 since it does not require a controller responsive to the flow cytometer. This divergence in scope between claim 14 of the new main request and the previous requests triggered new objections from the opponent. In particular, the opponent considered that the subject-matter of claim 14 of the new main request lacked novelty and inventive step in view of documents D7 and D15. Furthermore, the opponent maintained the objections it had already raised against the second option of claim 1.

As to auxiliary request 20, the opponent raised new objections of added subject-matter and a lack of clarity. Furthermore, it maintained its objection that the subject-matter of claim 1 lacked an inventive step in view of D16 and also considered D7 to be relevant.

Hence, due to the broadening of the claimed subject-matter in relation to the previously pursued requests, the admittance of the new main request and auxiliary request 20 would also be detrimental to procedural economy.

2.4 For these reasons, the board has decided that the main request and auxiliary request 20 are not to be admitted into the appeal proceedings.

3. Admittance of documents D7 and D15

The opponent referred to D7 and D15 for the first time in the appeal proceedings after the issuance of the summons and only in connection with the new main request and auxiliary request 20. Since these requests have not been admitted, the board has decided not to admit D7 or D15 either.

4. Auxiliary requests 1 to 14 and 16 to 19 - admittance

As already pointed out by the board in its communication of 19 September 2023, none of auxiliary requests 1 to 14 and 16 to 19 were substantiated on appeal.

Pursuant to Article 12(5) RPBA, the board has therefore decided not to admit these requests.

5. Auxiliary request 15 - novelty over D16

5.1 D16 relates to a method and apparatus for flexibly controlling sorting decisions for a flow cytometer at a purity vs. yield ratio of sorted particles (D16, abstract). D16 also addresses the problem of the occurrence of coincident particle sets at higher flow rates (column 2, line 63, to column 3, line 51).

5.2 It is common ground that the system of D16 includes a fluid delivery system, a flow cytometry apparatus for receiving the fluid, forming it into a stream and classifying the particles according to the characteristics (data acquisition system 10b; column 8, lines 13 to 18), and a sorting system for sorting selected particles in the stream according to a sorting strategy (column 11, lines 6 to 12).

5.3 The board notes that in the context of Figure 5, referred to by both parties, the system is disclosed in relation to a deflection sorting system (i.e. the particles are electrically charged according to their classification and then sorted electrostatically). However, as argued by the opponent, it is mentioned in column 15, lines 57 to 64, that the system 100 of Figure 5 could also be used for "selective destruction (e.g. zapping) of objects" instead of sorting. It is known in the field of flow cytometry that "zapping" means laser ablation (see D1, Introduction; D2, abstract). Hence, D16 discloses the feature "a laser for ablating selected particles".

5.4 As pointed out by the opponent, D16 discloses an algorithm to identify the optimal sorting strategy (column 15, lines 1 to 29). This algorithm uses, inter alia, information from the "detection signals generated in response to the respective particles passing a selected point of the flow cytometer", hence, in the wording of the claim, information from the flow cytometry apparatus that classifies the particles, i.e. pre-sort information. This information is used to optimise the yield/purity ratio and to determine a sort decision to control the hardware circuitry of system 100 (D16, column 15, lines 25 to 29). This means that the sorting strategy (represented by the sort decision) is varied by the algorithm as a function of the desired purity and/or the desired yield, as required by the claim.

In addition to this algorithm, D16 discloses a learning algorithm (column 15, lines 29 to 34) to which both parties referred in their submissions. However, it does not matter whether the learning algorithm uses post-sort data or pre-sort data, since it is disclosed that the algorithm mentioned in line 2 of column 15 uses pre-sort data to determine an optimised sort decision, i.e. to vary the sorting strategy, as explained above.

Hence, D16 discloses the feature "a control responsive to information received from the flow cytometry apparatus ... to vary its sorting strategy".

5.5 Consequently, the subject-matter of claim 1 of auxiliary request 15 lacks novelty over D16.

6. As the only claim request admitted into the appeal proceedings is not allowable, the patent has to be revoked.

Order

For these reasons it is decided that:

1. The decision under appeal is set aside.

2. The patent is revoked.