French drugmaker Sanofi and US marketing partner Regeneron have announced they will appeal a ruling by a US federal district court judge that would prevent them from selling their cholesterol drug Praluent (alirocumab), a human monoclonal antibody targeting PCSK9 (proprotein convertase subtilisin/kexin type 9), in the country.

The judge issued an injunction after a jury said earlier that Sanofi and Regeneron had infringed Amgen’s patent for its rival drug Repatha. The companies were given 30 days to finalize an appeal. The latest development is part of a long-running patent dispute.

In a statement, Sanofi it would continue marketing Praluent in the US for the present. "We will immediately appeal today's ruling, along with the jury's earlier finding upholding the validity of Amgen's patents," the French company’s General Counsel Karen Linehan told US media. "It is our longstanding position that Amgen's patent claims are invalid and that the best interests of patients will be greatly disserved by an injunction preventing access to Praluent," she said.

So far, reports say, US sales have not been close to figures analysts had initially predicted for the new class of cholesterol treatment.  Original estimates had foreseen sales of a combined $3 billion for the two rival drugs by 2022; however, Praluent racked up sales of only $38 million in last year’s third quarter, compared with Repatha’s $40 million.

Both drugs, intended for patients with genetic conditions that will not allow them to take the cheaper statins, are expensive and can only be injected. Their costs run to about $14,000 annually, which means that many insurers are opting not to reimburse patients. The US court’s  ruling is being questioned by some legal experts, along with the Amgen move to ask for it. Some have argued that if the injunction takes effect, current Praluent patients may have to stop taking the drug, to their detriment.

Meanwhile, Japan’s Ministry of Health, Labor and Welfare has granted marketing and manufacturing authorization for Praluent for the treatment of uncontrolled low-density lipoprotein (LDL) cholesterol in certain adult patients with hypercholesterolemia, who are at high cardiovascular risk. Praluent 75 mg and 150 mg will be available in Japan as a single-dose pre-filled pen and syringe.

"Hypercholesterolemia is a significant concern in Japan, and many patients are not able to achieve their LDL cholesterol treatment goals despite current lipid-lowering therapy," said Jay Edelberg, head of Cardiovascular Development, Sanofi. "For these patients, Praluent could be an important treatment option to help address their needs."

Along with the EU and the US, Praluent has been approved by authorities in Canada and Mexico. The indications vary from country to country.