Eli Lilly 's experimental lung cancer drug raised concerns with US regulators that it may increase patients' risk of suffering potentially deadly blood clots.

The drug, known as necitumumab, improved patients’ overall chances of survival, yet people taking the medicine also experienced more risk, the Food and Drug Administration said in a report on Tuesday.

Lilly is seeking to sell the medicine to treat a subset of the most common type of lung cancer. FDA advisers will meet on Thursday to discuss the risks and benefits of necitumumab for patients with advanced squamous non- small cell lung cancer, in combination with chemotherapy.

The FDA is expected to decide if Lilly can sell the drug by the end of the year. While the safety of necitumumab reflects that of similar drugs, the increased danger of clotting “in this already high risk population is of concern,” the FDA said.

One study showed that out of 538 patients taking necitumumab and chemotherapy, 9 per cent experienced a serious clot, compared with 5 per cent of 541 patients given only chemotherapy, according to the report.

- Bloomberg