Skinny labels are a powerful tool for generic drug companies to avoid infringement of method of treatment/ ‘medical use’ patents after the original drug patent expires, by allowing a ‘carve out’ of the still-patented medical indications. However, as a generic drug is identical to the originator’s branded drug, physicians may prescribe it ‘off-label’ for the carved-out indication. The originator company may then try to sue the generic manufacturer for patent infringement.
The US Supreme Court’s recent decision in Hikma Pharmaceuticals v Amarin Pharma Inc., ruled that generic manufacturer Hikma did not induce infringement of Amarin’s patent.
Read more to learn what this could mean for enforcement of pharmaceutical patents against generics in the US, and how this compares to the approach taken by the UK courts.
Skinny Labels
Pharmaceutical companies can apply for method of treatment/ medical use patents to maintain patent protection for their drug (limited to the claimed medical indications) for years beyond the original drug patent’s expiry date.
Legal systems aim to create a fair balance between IP protection and market competition; and health systems are motivated to bring down the cost of medicines when possible.
To try and achieve this balance, generic drugs are allowed to carry a ‘skinny label’ that omits patented medical indications. This ‘carve out’ of patented uses may allow the generic manufacturer to enter the market for off-patent indications before all of the drug’s patents expire.
Hikma v Amarin 2026 – Summary of the facts:
Amarin Pharma developed the drug Vascepa®, which was initially approved by the FDA to treat severe hypertriglyceridemia (SH). Later, Amarin obtained FDA approval and patents for a new method of use of Vascepa®: reducing cardiovascular risk (CV).
In 2020, Hikma Pharmaceuticals obtained FDA approval to sell its ‘generic Vascepa’ under a skinny label carving out the patented use in CV. Despite Hikma’s skinny label, Amarin alleged that Hikma’s website statements, press releases, and references to its product as ‘a generic version of Vascepa’ effectively encouraged physicians to prescribe the drug for the patented CV indication – i.e., Amarin alleged that Hikma induced patent infringement under 35 U.S Code § 271(b).
The question discussed before the US Supreme Court became:
Can a generic manufacturer be liable for induced infringement when it uses a skinny label that excludes the patented indication, but other communications allegedly encourage the patented use?
A ‘sheer possibility’ or ‘plausibility’ of inducing infringement?
The US Court considered the relevant legal question to be whether Hikma actively encouraged infringing use for CV – it was not enough for Amarin to assert that Hikma’s marketing material might, ‘passively’ encourage physicians to use the generic drug off-label for this patented indication. In the Court’s view, Amarin failed to plausibly show that Hikma – even implicitly – took the kind of ‘active steps’ to encourage infringement that are required for induced infringement liability.
This decision is a victory for generic drug manufacturers by confirming the high standard of proof required for originators to pursue induced-infringement claims in the US. Although a skinny label does not guarantee ‘safe harbour’, a generic manufacturer may be more confident of avoiding induced infringement in the US if they do not ‘actively encourage’ use of the generic drug in patented indications.
How does this compare to UK law?
The current position in the UK is somewhat less clear.
In the UK, the Supreme Court in Warner-Lambert Company LLC v Generics (UK) Ltd 2018 was asked to consider direct infringement of a ‘Swiss form’ 2nd medical use patent. As they found the patent to be invalid, the Court did not need to decide on infringement: the judges made revealing ‘obiter’ (non-binding) comments but did not provide a definitive test for assessing infringement by a skinny-labelled generic drug.
Warner-Lambert v Generics
The 5 UK Supreme Court judges were split between two different proposed legal tests: 1) based on outward presentation of the generic product – including packaging and labelling – whereby a skinny label would avoid a finding of infringement; and 2) based on subjective intent – whereby other factors such as “words, conduct and even inactivity” are assessed to determine whether the generic manufacturer intended to target the patent-protected market.
Therefore, uncertainty remains as to what a generic manufacturer must do to avoid infringement of a patented medical indication in the UK and any future decision is likely to be highly fact-specific. A test based on outward presentation would certainly favour the generics industry but may be unfair to originators where off-label use is widespread. A test based on subjective intent – or even a US-style assessment of ‘active encouragement’ – places a high evidentiary burden on originators but this more ‘holistic’ approach may better reflect some ‘real world’ practices.
Whichever test is applied, it seems that a properly executed skinny label may offer protection from infringement of pharma patents in the US and UK, so long as the generic manufacturer’s conduct does not – even implicitly, or by omission – encourage off-label use of the generic drug for a patented indication.
