The UK Supreme Court has ruled against Pfizer in a long-running legal battle over the validity of a second medical use patent protecting pregabalin.

The drug giant's original patent for pregabalin (sold as Lyrica) as a treatment for epilepsy expired in 2014, paving the way for Allergan (previously called Actavis) and others to launch cheaper generic formulations for the condition and generalised anxiety disorder.

But Pfizer also secured a second-use patent protecting pregabalin as a treatment for pain until July 2017. In the complex and closely-watched legal case, the firm argued that Allergan's generic alternative, and others, would inevitably also be used to treat pain despite targeting non-protected indications, and thus infringe its patent.

However, in October 2016, the Court of Appeal affirmed an earlier High Court decision that the patent covering pregabalin for pain was not infringed by generic forumations, and also that patent claims directed generally to pain and neuropathic pain are invalid.

The Supreme Court has now backed this decision, ruling that patent claims relevant to the neuropathic pain indications are invalid and marking the end of the line for Pfizer’s battle to uphold the drug’s protection in this setting.

Pfizer voiced disappointment with the decision. “This ruling has significant impact on innovation in public health,” it said in a statement.

“The period that a medicine is under patent is a critical phase in its lifecycle that fuels innovation – as science evolves and knowledge grows, patients increasingly benefit from ongoing research into new uses for existing medicines.

“As situations such as these are expected to become more common, it’s important for patients that pharmaceutical companies are able to protect patents, including second medical use patents.”

Nick Sutcliffe, partner at Mewburn Ellis, said the news is “potentially bad news for patentees, not least in the biotechnology and pharmaceutical fields.

“The ruling will make patents easier to avoid and more vulnerable to invalidation and thus weaken patent holders’ rights and ability to innovate with confidence.

“The ruling confirms that patentees need to provide a significantly broader range of evidence to justify the scope of their patent protection – which risks placing an onerous burden on rights holders and thus increases the cost and uncertainty of obtaining and enforcing patent rights.”