US regulators have told makers of big-selling tumour necrosis factor blockers that they need to put stronger warnings on their labels, particularly with relation to the risk of cancer to young users.

The US Food and Drug Administration says these must include an updated boxed warning, highlighting the increased risk of cancer in children and adolescents who receive these drugs to treat juvenile rheumatoid arthritis, Crohn’s disease, and other inflammatory conditions. The drugs included in the anti-TNF class include the blockbusters Johnson & Johnson and Schering-Plough's Remicade (infliximab), Amgen and Wyeth's Enbrel (etanercept) and Abbott Laboratories' Humira (adalimumab), as well as the recently-approved Cimzia (certolizumab pegol) and Simponi (golimumab), from UCB and J&J/S-P respectively.

The FDA said the action stems from an investigation begun in June 2008. An analysis of children and adolescents treated with TNF-blockers “showed an increased risk of cancer, occurring after 30 months of treatment on average”, the agency said, and about half of the cancers were lymphomas. Some of the reported cases were fatal.

The FDA said that it is working with the manufacturers “to explore new ways to further define the risk of cancer in children and adolescents who use these drugs”. It added that the updated warnings need to include reports of psoriasis associated with the use of TNF blockers.

Amgen and Wyeth responded quickest to the FDA’s pronouncement, saying that they “support the continued evaluation of the potential risks and benefits of TNF blockers for patients who are prescribed these therapies”. The companies added, however, that they believe Enbrel “continues to offer a favourable benefit-risk relationship for patients”.