The NHS could reclaim up to £502 million in excess prescribing costs relating to Pfizer’s pregabalin if the drug giant’s last effort to uphold the drug’s legal protection is unsuccessful, a study has found.

Pfizer’s original patent for pregabalin (sold as Lyrica) as a treatment for epilepsy expired in 2014, paving the way for the launch of cheaper generic formulations for the condition and generalised anxiety disorder.

However, the drug giant subsequently secured a second-use patent protecting pregabalin as a treatment for pain until July 2017.

In a complex and closely-watched legal case, Pfizer maintains that generic alternatives would inevitably also be used to treat pain despite targeting non-protected indications, and thus infringe its second-use patent.

As such, the drug giant obtained an order against NHS England compelling the NHS to issue guidance that only its branded product should be prescribed for pain, and it also sent letters to doctors and pharmacists threatening legal action if they did not comply.

However, in a landmark ruling, the High Court ruled in 2015 that the patent covering pregabalin for pain is not infringed by generic alternatives, and also that patent claims directed generally to pain and neuropathic pain are invalid. This ruling was backed by the Court of Appeal in 2016, and is now being considered by the Supreme Court.

According to a study led by Oxford University researchers and published by BioRxiv, following Pfizer’s action and NHS England’s guidance on Lyrica for pain in 2015, prescriptions for the drug leapt 25 percent in England.

If Lyrica had come off patent in the September of that year and Pfizer had not appealed, the NHS would have spent around £502 million less on the drug in England to July 2017, the researchers claim, and stress this could potentially be claimed back by the NHS.

However, in a statement emailed to PharmaTimes, Pfizer said: “We strongly believe in the validity and importance of the second medical use patent for the use of Lyrica in pain. We await the decision from the Supreme Court and are unable to provide further comment until after this is received.”