Pfizer sued over COVID-19 antiviral drug

Pfizer is facing a lawsuit centring on its COVID-19 antiviral, Paxlovid (nirmatrelvir tablets; ritonavir tablets), after Enanta Pharmaceuticals filed a complaint citing patent infringement.

The biotech lodged the lawsuit at the US District Court for the District of Massachusetts on June 21.

Paxlovid generated first quarter 2022 sales of $1.5 billion for Pfizer with the pharma giant forecasting full-year 2022 sales of $22 billion.

Enanta is not seeking an injunction but it has asked for a judgment that Pfizer has infringed and continues to infringe US patent number 11,358,953 and an award of damages.

The ’953 patent discloses and claims compounds and pharmaceutically acceptable salts that inhibit coronavirus replication activity, and methods of treating a coronavirus infection.

The complaint outlines how in early 2020, when SARS-CoV-2 was emerging as a global pandemic, Enanta launched a COVID-19 research programme to discover direct acting antivirals to disrupt the replication of the disease.

In early 2021, Enanta identified its 3CL protease inhibitor EDP-235 as the lead compound for its COVID-19 programme, and it was specifically designed as a once-daily, oral treatment for COVID-19.

In March that year, the US Food and Drug Administration (FDA) granted fast-track designation for Enanta’s EDP-235.

The US Patent and Trademark Office awarded the patent to Enanta this month based on Enanta's July 2020 patent application.

Pfizer currently sells Paxlovid in the US under emergency use authorisation by the FDA for the treatment of mild-to-moderate COVID-19 in adults and younger patients (12 years of age and older weighing at least 40 kg), but who are at high risk of progression to severe COVID-19.

According to Enanta, Pfizer’s infringing product comprises nirmatrelvir tablets co-packaged with ritonavir for the treatment of COVID-19.

As Pfizer’s nirmatrelvir is a SARS-CoV-2 3CL protease inhibitor, the complaint holds that the pharma giant has infringed.

This move comes after RNAi therapeutics company Alnylam Pharmaceuticals filed patent infringement proceedings against Pfizer and Moderna in March over the alleged infringement of its biodegradable cationic lipids, which it held were “foundational to the success of the mRNA COVID-19 vaccines.”