The US Food and Drug Administration (US) has handed AstraZeneca a complete response letter (CRL) regarding its anaemia drug roxadustat.

AZ had submitted a new drug application for roxadustat to the FDA for the treatment of anaemia of chronic kidney disease (CKD) in both non-dialysis dependent (NDD) and dialysis-dependent (DD) adult patients.

In the CRL, the FDA has requested an additional clinical trial on the safety of roxadustat in both the NDD and DD patient populations, AZ said in a statement.

FibroGen and AZ are currently working together with the FDA to evaluate the ‘next steps’ for the potentially first-in-class anaemia drug.

However, the companies have already complete a Phase III programme, including more than 8,000 patients, so it’s not immediately clear if they will be willing to complete an additional study.

“We are deeply disappointed with this result, and this is an unfortunate day for patients suffering from anaemia of CKD in the US,” said Enrique Conterno, chief executive officer, FibroGen.

“Roxadustat is changing the lives of patients around the world, and we and our partner AstraZeneca will discuss next steps in the US,” he added.

The drug is already approved in China, Japan, Chile and South Korea, and has received a positive opinion from the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP).