Applying the Actavis questions to numerical limitations: Regen Lab v Estar

The new year sees the issue of yet another UK court case applying the doctrine of equivalents as established by the UK Supreme Court in Actavis v Eli Lilly ([2017] UKSC 48) ("Actavis"). The recent High Court case Regen Lab v Estar [2019] EWHC 63 (Pat) applied the Actavis questions to a numerical value for the first time. The case concerned the validity and alleged infringement by Estar medical ("Estar") of Regen Lab's ("Regen") EP (UK) 2073862 patent for a method of producing cells for regenerative medicine.

Actavis and numerical ranges

The issue of whether the doctrine of equivalents should apply to numerical ranges was discussed in the memorable UCL IBIL event that took place shortly after Actavis was handed down (IPKat event reports here and here, video here). Lord Neuberger commented at this event that he was "attracted by the point" that, where a party had specifically defined numerical limits, this should be a clear enough limitation that they didn't intend the scope of the claims to go outside these limits.  US Court of Appeal for the Federal Circuit (CAFC) Judge, Judge O'Malley, commented that there is usually a very good reason why a patentee has specified a numerical limitation, namely in order to avoid prior art.  Judge O'Malley suspected that this is why she had not seen many doctrine of equivalent cases involving numerical limitations. Dutch Judge, Judge Rian Kalden (Head of the IP Division, Court of Appeal, The Hague) also observed that in the Dutch court, as a general rule, it is difficult to sustain a doctrine of equivalents argument for a numerical limitation.

We may therefore have expected that establishing equivalence to a claimed numerical limitation would be a similarly high bar in the UK. The UK High Court decision in Regen Lab v Estar confounds any such expectation. 

The Technology
Platelets and red blood cells

The patent in question related to the field of regenerative medicine, and in particular to a method for producing platelet rich plasma (PRR) from whole blood. Platelets are small cell fragments necessary for blood clotting. PRR can be obtained by spinning down whole blood in a centrifuge. Red blood cells are forced to the bottom and PRR rises to the top. A thin layer of leukocytes and platelets (the buffy coat) separates the layer of red blood cells and the layer of plasma. Separation of the PRR can be facilitated by including a medium density gel that positions itself between the red blood cells and the buffy coat/plasma. The separation of whole blood in this way is a standard technique in the art. This Kat has herself spent many a happy hour during her PhD collecting buffy coats for the purpose of culturing macrophages.

The patent EP (UK) 2073862 at issue claims a process for the preparation of a cell composition, comprising the steps of centrifuging whole blood in a separator tube, removing half of the platelet poor plasma from the top and re-suspending the remaining plasma and buffy coat to produce enriched platelet rich plasma (PRP). The claim specifies the type of separator tube and the centrifugal force to be used. In particular the claim specifies that the separator tube is either (1) a glass tube containing thixotropic gel and 0.10 M sodium citrate, or (2) a polyethylene terephthalate separator tube containing a highly thixotropic gel formed by a polymer mixture and anhydrous sodium citrate at 3.5 mg/mL. The inventive concept of the claim was said to reside in the resuspension step, which permits preparation of PRP from whole blood using only one centrifuge step.

Separation of whole blood
Regen brought an infringement action against Estar.  Estar counterclaimed that Regen's patent was invalid. Estar has also filed an opposition against the granted patent at the EPO, and third party observations against a pending divisional application.

The issue of validity primarily concerned whether the claims were novel in view of Regen's own disclosures prior to the priority date of the patent. The issue of infringement depended on whether the use of a separator tube comprising sodium citrate at a different molarity than that specified in the claims, none-less-the infringed under a doctrine of equivalents.

A number of disagreements emerged between the witnesses provided by each party as the subject-matter of a disclosure by Regen's witness Mr Turzi, and whether this disclosure had been given in confidence. HHJ determined that a public disclosure of the claimed process had occurred, that the claimed process therefore lacked novelty.

One interesting point to be noted is that whilst HHJ Hacon was not able to determine whether the type of tube specified in the claim had been disclosed by Mr Turzi, this did not matter (para. 133). The tubes were available for purchase, and so disclosure of the use of the tube enabled use of the invention.


HHJ Hacon proceeded to consider the issue of infringement, applying the principles of claim interpretation set out by Actavis v Eli Lilly ([2017] UKSC 48), as reviewed by the Court of Appeal in Icescape v Iceworld (IPKat post here). HHJ addressed two issues relating to the Actavis questions, (1) should each limitation in a claim be treated separately or together, and (2) how should the Actavis questions be applied to a numerical limitation.

Multiple differences

Should multiple differences between an alleged infringement and the claim on a normal (i.e. purposive) construction be assessed separately or together? As HHJ Hacon pointed out, "if there is some interaction between the relevant elements of a claim, the answer to the revised Improver questions ["the Actavis questions"] could lead to one result if the equivalents are considered separately and the opposite result if considered together" (para. 211). In HHJ Hacon's view, "only the latter result is relevant", given that the question is whether an alleged infringing product or process as a whole is a variant of the claimed invention.

The question was at issue in this case because the alleged infringement differed in two features from the claimed invention: (1) the gel in the separation tube, and (2) the molarity of the sodium citrate solution was 0.136 M, not 0.10 M.

Numerical claims

Claim 1 claimed a separation tube comprising 0.10 M sodium citrate. Estar's tubes contained 0.136 M sodium citrate. As pointed out by HHJ Hacon, the law on claims with a numerical content was recently revisited in Jushi v OCV (IPKat post here). HHJ Hacon noted that this case confirmed that the approach to claims containing numerical ranges is the same as for any other claim, and that Actavis had not changed this. The Actavis questions should thus be applied to numerical claims in the same way as any other claims.

HHJ Hacon observed that, before Actavis, purposive construction did not mean "that an integer can be treated as struck out if it does not appear to make any difference to the inventive concept. It may have some other purpose buried in the prior art and even if this is not discernible, the patentee may have had some reason for introducing it" (para. 219, quoting Step v Emson [1993] RPC 513). However, as confirmed in Icescape, the focus should no longer be on the claim language, but should be directed to the "inventive concept" of the claim.

HHJ Hacon then made a distinction between "the inventive concept" and "the invention". HHJ Hacon observed that the invention is that which is claimed, according to Section 125(1) UKPA. Following Actavis, the patent protects more than the claimed invention, it protects the "inventive concept: "the new technical insight conveyed by the invention - the clever bit - as would be perceived by the skilled person" (para. 222).

If this Kat understands HHJ Hacon's reasoning correctly, the central position of the claim in the patent specification appears severely diminished. It appears to have been demoted to the description of a mere embodiment comprising the "inventive concept". In Icescape, for example, the claims were interpreted as describing an embodiment in which pipes were arranged in parallel, and that this did not prevent infringement by an alternative embodiment in which the pipes were arranged in series. This Kat is interested in readers views of HHJ Hacon's separation of "the inventive concept" from the "invention" (para. 222). Is this a real or useful distinction?

Some significance is apparently returned to the claims by the third Actavis question. This final question asks whether, if the alleged infringement is found to be a variant of the claimed invention, a reader of the patent would have none-the-less concluded that the patentee intended that strict compliance with the literal meaning of the claim was an essential requirement of the invention. However, HHJ Hacon's application of this test in the present case appears to place the bar for demonstrating this relatively high as compared to, for example, the US.

Applying the Actavis questions

HHJ Hacon applied the Actavis questions in order to determine whether Estar's tubes comprising a 0.136 M sodium citrate were equivalent to the claimed tube comprising 0.10 M sodium citrate.

a) Notwithstanding that it is not within the normal meaning of the claim, does the variant achieve substantially the same result in substantially the same way as the invention, i.e. the inventive concept revealed by the patent?

HHJ Hacon identified the inventive concept of the claim as the preparation of PRP for solely therapeutic use by employing a thixotropic gel wherein (a) there is only one centrifugation and (b) after centrifugation about half the supernatent is removed and the platelets are then re-suspended in the enriched plasma. On expert evidence that "[t]he molarity [of the sodium citrate] per se is not important", HHJ found that the inventive concept of claim 1 is exploited in substantially the same way to achieve substantially the same result by Estar's use of 0.136 M sodium citrate as opposed to 0.10 M citrate.

b) Would it be obvious to the person skilled in the art, reading the patent at the priority date, but knowing that the variant achieves substantially the same result as the invention, that it does so in substantially the same way as the invention?

HHJ determined that the view of the expert corresponded to what would have been the view of the skilled person at the priority date. The answer to this question was therefore "yes".

c) Would such a reader of the patent have concluded that the patentee nonetheless intended that strict compliance with the literal meaning of the relevant claim(s) of the patent was an essential requirement of the invention

In HHJ Hacon's view, this question "would only be answered yes if there had been a sufficiently clear indication to the skilled person that strict compliance with the figure of 0.10 M was intended" (para. 252). In the absence of such an indication in the specification or from common general knowledge, HHJ Hacon found no such indication.

Actavis permits recourse to the prosecution history, (1) if there is an issue of construction of scope that is unclear in view of the specification or claims, or (2) if it would be contrary to the public interest for the file to be ignored. The Defendants cited a letter from Regen to the EPO in which the novel features of the claims in view of prior art were indicated, including "a specific concentration" of sodium citrate. HHJ Hacon did not consider there was any matter of scope that was unclear or that it would be contrary to public interest to ignore the letter. HHJ Hacon thus determined that "the prosecution history has no effect on the scope of the claim".

HHJ Hacon therefore found that, had the patent been valid, it would have been infringed according to the doctrine of equivalents.

So why was the molarity limitation included in the claim?

Doctrine of equivalent cases always seem to beg the question of why, if a limitation is not essential or material to the inventive concept of the claim, was the limitation included in the claim?

In the present case, the 0.10 M limitation was specified in the priority document, both in claim 1 and throughout the description. Why was the claim drafted to include this feature if it was not intended to be limiting? The 0.10 M limitation does not seem to have been relied on for novelty during prosecution of the parent, but was cited as providing novelty in combination with other features. Limiting your claim with preferable but inessential features of your invention, corresponding to your commercial embodiment, is one strategy for achieving quick grant (as it can pre-empt novelty objections). Was this Regen's strategy? If so, is it fair that these limitations are disregarded in an assessment of infringement?

It therefore appears that the doctrine of equivalents, as established by Actavis and interpreted by HHJ Hacon, permits a patent proprietor to claim infringement by a variant that does not possess a claimed limitation, wherein the same limitation may be cited (if only obliquely) as a feature conferring novelty.

Notably, during prosecution of the pending divisional (EP3111974), the EPO Examiner acknowledges the 0.10 M concentration of sodium citrate as a novel feature distinguishing a composition produced by the claimed process from the prior art. See for example the EPO Examination report here, where novelty of a claim directed to a cell composition obtained by a process equivalent to the granted patent, is acknowledged over a Regen sales sheet "since the citrate concentration is not specified". See also the proprietor's submission to the Opposition Board for the granted case: 'D9 and D15 also do not disclose "a glass separator tube containing a polyester-based thixotripic gel and a buffered sodium citrate solution at 0.10 M' (page 12, second paragraph). Enough to satisfy the public interest test?

Wading through prosecution history
Estar has reported that, in an equivalent German infringement case in the Dusseldorf Regional Court, Estar was found not to infringe Regen's patent. IPKat has been unable to find a copy of this decision, and would be grateful readers could provide a pointer.

In Icescape v Iceworld and Regen v Estar the UK courts demonstrated their willingness to apply the principles of Actvais first to mechanical inventions and then to claims specifying clear numerical limitations. The opportunity for an alleged infringer to make recourse to prosecution history, the possibility of which was established by Actavis, has so far not provided any circumstance in which purposeful limitation by a patent proprietor can be demonstrated. Regen v Estar undoubtedly provides an interesting development of the UK doctrine of equivalents, one that even Lord Neuberger may not have foreseen.  It will be interesting to see if the reasoning will be adopted on appeal.
Applying the Actavis questions to numerical limitations: Regen Lab v Estar Applying the Actavis questions to numerical limitations: Regen Lab v Estar Reviewed by Rose Hughes on Monday, February 04, 2019 Rating: 5


  1. This stuff rather makes my brain ache, but one thing I do get from it is that infringement in the UK is now a total mess. How are we supposed to advise someone working around a patent whether their apparatus is likely to infringe when the scope of the claims is so unclear? The wording within them seems to be advisory rather than limiting.
    Please can we have another submission to the SC, when there is a sensible judge in place, to get this cleared up.

  2. IPKat also made reference to a recent decision 4b O 117/16 of 5 June 2018 by the district court (LG) Duesseldorf, which we briefly discuss here and is now be publicly available (
    The decision deals with a method for preparing a cell composition wherein the main claim comprises the feature "buffered sodium citrate solution of 0.10 M". The court concluded that literal patent infringement and infringement under the doctrine of equivalents (DoE) was denied for an embodiment having a concentration of 0.109 M (i.e. 9% above the claimed value). Besides, a further claim feature (polyester-based gel) was also considered to be not fulfilled.
    Since the concentration of 0.109 M was not regarded to be within typical tolerances, the court further assessed the criticality of the claimed concentration for the desired effect. As no reason was found why the claim was restricted to one single value, a skilled person would not have found an embodiment with 0.109 M as providing the same effect in accordance with the claimed value (corresponding to the third DoE question, which is: “Are the considerations that the person skilled in the art had to apply oriented to the technical teaching of the patent claim in such a way that the person skilled in the art took the variant into account as being an equivalent solution?”).
    The LG Duesseldorf decision confirms that measuring/manufacturing tolerances have to be considered when assessing literal infringement. Furthermore, the DoE does not expand the claim scope in the absence of a broader teaching in the patent.
    We look forward to further Decisions to be handed down regarding numerical values.
    Wuesthoff & Wuesthoff has extensive experience in preparing opinions and representing clients in infringement cases. For further information about our competencies and services, please do not hesitate to contact us


All comments must be moderated by a member of the IPKat team before they appear on the blog. Comments will not be allowed if the contravene the IPKat policy that readers' comments should not be obscene or defamatory; they should not consist of ad hominem attacks on members of the blog team or other comment-posters and they should make a constructive contribution to the discussion of the post on which they purport to comment.

It is also the IPKat policy that comments should not be made completely anonymously, and users should use a consistent name or pseudonym (which should not itself be defamatory or obscene, or that of another real person), either in the "identity" field, or at the beginning of the comment. Current practice is to, however, allow a limited number of comments that contravene this policy, provided that the comment has a high degree of relevance and the comment chain does not become too difficult to follow.

Learn more here:

Powered by Blogger.