European regulators are undertaking a safety review of Gilead’s cancer drug Zydelig following a spike in serious adverse events observed in clinical trials.

Zydelig (idelalisib) is currently authorised in the European Union to treat the rare blood cancers chronic lymphocytic leukaemia (CLL) and follicular lymphoma (one of a group of cancers called non-Hodgkin lymphoma, or NHL).

But three clinical trials investigating the drug in combination with other cancer medicines have shown an increased rate of serious side effects including deaths, mostly due to infections, the European Medicines Agency said.

The studies involved patients with CLL and indolent non-Hodgkin lymphoma. However, the CLL study investigated combinations of medicines not approved while those in NHL included patients with disease characteristics different from those covered by the currently approved indications.

The EMA said it will now review the data from these studies to assess whether the findings have any consequences for the authorised uses of Zydelig, and is also considering whether any other immediate measures are necessary while the review is ongoing. 

The drug already carries a black-box warning on the serious risks linked with its use, including potentially fatal liver problems. 

Across the pond, the US Food and Drug Administration reportedly said it is “aware of and is looking into reports of deaths” with Zydelig during clinical trials, according to Bloomberg.