Modernatx, Inc v Pfizer Limited & Ors

Modernatx, Inc v Pfizer Limited & Ors is a Court of Appeal patent decision about whether an earlier University of Pennsylvania patent application invalidated a Moderna patent claim for a specific modified mRNA.

The Court of Appeal dismissed the appeal. The clearest appellate conclusion was that the trial judge had made no error of law or principle in finding that claim 3 of EP949 was not obvious in light of UPenn.

The judgment is useful beyond the life sciences sector. It shows how courts deal with broad technical documents that contain many options, embodiments and lists. A prior publication does not automatically destroy a later patent just because the later solution can be found somewhere within a large field of possibilities.

This dispute sat in a very high-value commercial setting. Moderna and the Pfizer/BioNTech group were on opposite sides of litigation involving mRNA technology, and the alleged infringements related to Comirnaty, Pfizer/BioNTech’s mRNA-based SARS-CoV-2 vaccine.

At first instance, Meade J dealt with two Moderna patents after a 19 day trial. He held that EP949 was valid and had been infringed, while another patent, EP565, was invalid. The appeal did not reopen everything. Pfizer/BioNTech challenged only the validity of EP949.

Moderna also narrowed the case on appeal. It relied only on claim 3 of EP949. That mattered because patent disputes often become much more focused at appeal stage. A business reading a patent judgment should always check which claims are still live, because the commercial risk can turn on that detail.

Claim 3 covered an mRNA in which 100% of uracil-containing nucleotides were replaced with nucleotides comprising N1-methyl-pseudouridine, or m1Ψ. Pfizer/BioNTech said an earlier UPenn patent application had already got there first, or at least made that route obvious.

The Court of Appeal therefore had to decide whether UPenn really taught the claimed invention in the strict legal sense, or whether the challenge depended on selecting one option from a much broader technical disclosure with the benefit of hindsight.

The science mattered because the patent claim was narrow and specific. By 2010, scientists wanted to use cells to express chosen proteins for research and therapeutic purposes. One route was DNA, but DNA had drawbacks because it had to enter the nucleus and carried a risk of genomic integration.

mRNA offered advantages. It did not need to enter the nucleus and was easier to synthesise. But there were practical problems. Foreign RNA could trigger the immune system, be broken down and fail to translate efficiently into protein.

The judgment describes the importance of Karikó and Weissman’s work. Their 2005 paper showed that replacing uridine with pseudouridine and other modified nucleotides could reduce immune recognition. Their 2008 paper went further and showed that pseudouridine-containing mRNA could also improve translation efficiency.

UPenn built on that work. It was a long patent application covering RNA molecules with pseudouridine or modified nucleosides, methods of reducing immunogenicity and methods of increasing translation efficiency. It included many embodiments and many possible modifications.

That breadth was central to the appeal. UPenn mentioned m1Ψ among a number of pseudouridine-related possibilities. It also included broad percentage ranges for modification, including 100%, and covered different RNA types including mRNA. But the court had to decide whether that broad disclosure really amounted to a clear teaching of Moderna’s later claim.

The legal issue was whether claim 3 of EP949 was invalid because of UPenn. Pfizer/BioNTech ran two classic patent attacks. First, they said UPenn deprived claim 3 of novelty. Secondly, they said UPenn made claim 3 obvious.

On novelty, the judgment restated the strict rule. Prior art must disclose subject matter which, if performed, would necessarily infringe the later patent. The court said prior disclosure requires clear and unambiguous disclosure, or clear and unmistakable directions to do something that falls within the claim. It is not enough that a skilled person could modify the earlier teaching to get there.

The court also stressed that a whole document must be considered, but it is not a reservoir from which features can simply be picked and mixed unless the document clearly teaches that combination. That point matters in any industry where patents and technical papers contain long lists, classes or optional features.

On obviousness, the appeal focused heavily on the identity of the notional skilled person, the weight to be given to the expert evidence and whether the challenger’s reasoning was affected by hindsight. The court also considered motivation and expectation of success. In practical terms, would the relevant skilled person really have been led to test m1Ψ in the way Pfizer/BioNTech suggested?

The Court of Appeal dismissed the appeal. Lord Justice Arnold, with Lords Justices Snowden and Moylan agreeing, held that the judge had made no error of law or principle in concluding that claim 3 of EP949 was not obvious in light of UPenn.

A major part of the appeal concerned the skilled person. The trial judge had identified that person as someone with knowledge of RNA biology and a practical interest in improving the use of mRNA in relation to translation and immunogenicity across a range of practical fields. Those fields included immunotherapy, direct vaccination, gene or protein replacement therapy and other application-focused areas.

Pfizer/BioNTech argued that the judge had drawn the line wrongly and had unfairly sidelined evidence from Dr Enright, whom the judge saw as a pure, basic scientist interested in fundamental research. The Court of Appeal rejected that criticism. It held that the judge was entitled to assess how closely each expert reflected the attributes of the skilled person and to prefer evidence that better matched the practical application-focused perspective he had identified.

The court also rejected Pfizer/BioNTech’s argument about how paragraph [0056] of UPenn should be read. It did not accept that the judge should have treated that passage as a technical teaching presenting a list of pseudouridine-like nucleosides of particular interest in the way the appellants suggested.

On hindsight, the court upheld the judge’s view that the challenger’s approach placed too much weight on a narrow part of UPenn and was affected by hindsight. That mattered because obviousness must be assessed without knowledge of the invention.

On motivation and expectation of success, the court accepted that the judge had been entitled to find that the skilled person would not have had a concrete or positive expectation of success if considering whether to test m1Ψ. The court also accepted that this was not shown to be a routine experiment that the relevant skilled person would simply carry out without such an expectation.

The result was that the first instance validity finding for claim 3 remained in place and the appeal failed.

This case is a good example of how patent disputes are often won or lost on documents and expert framing rather than broad commercial narratives.

First, the wording of claim 3 mattered. The claim was tightly framed around mRNA, 100% replacement of uracil-containing nucleotides and the specific modified nucleoside m1Ψ. That precision shaped the whole appeal.

Secondly, the structure of UPenn mattered. It was not a short paper with one direct instruction. It was a long patent application with many embodiments, broad lists, broad ranges and both actual and prophetic examples. The court treated that breadth carefully rather than assuming every later-selected option had already been individually disclosed.

Thirdly, the expert evidence mattered. The court accepted that it was legitimate to ask which expert more closely reflected the attributes of the skilled person. That is commercially important because businesses often assume any eminent scientist will do. In patent litigation, the fit between the witness and the legal construct of the skilled person can be decisive.

Fourthly, the court focused on practical motivation. It was not enough to say that a basic scientist might test a range of options. The question was whether the relevant skilled person, as properly identified, would realistically be motivated to take that route in the relevant practical context.

If your business develops technology, this decision is a reminder that patent strength and patent risk are rarely answered by a quick search or a broad technical comparison. A prior publication may mention a concept, a family of compounds or a long list of options, but that does not automatically mean a later patent claim is invalid.

Courts ask a narrower question. Did the earlier material clearly and unambiguously teach the claimed solution, or was the later claim only reachable by selecting and combining possibilities with hindsight? That distinction matters in pharmaceuticals, biotech, software, engineering and any sector where innovation often involves narrowing down from many technical options.

The case also shows why businesses should not rely on a simplistic “obvious to try” argument. The court looked at whether the relevant skilled person would actually be motivated to run the experiment and whether it was truly routine in the relevant field. A test being possible is not enough.

This affects several commercial moments. During fundraising, investors may ask whether your IP is defensible. In licensing, the other side may challenge validity to improve its bargaining position. In M&A, buyers will want to know whether key patents are strong and whether products risk infringing third-party rights. In all of those settings, detailed claim analysis and prior art review matter.

It also underlines the value of internal records. If your team chose one technical route over many others, records showing the problem being solved, the alternatives considered and the practical reasons for the chosen path can become important later.

For a time-poor business owner, the practical response is process discipline. Patent disputes are expensive, but many of the underlying risks can be reduced by better review points and better records.

If you are building a technical product, do not leave patent review until the end. Build it into product development, R&D sign-off and commercial launch planning.

The Court of Appeal handed down judgment on 1 August 2025. The appeal was from Meade J’s Patents Court decision dated 2 July 2024, with the order made on 25 September 2024 following the trial.

For business readers, the key point is that the appeal failed and the first instance conclusion on claim 3’s validity remained in place.