Eli Lilly is facing a considerable delay in bringing its diabetic eye disease drug Arxxant to the US market, after the Food and Drug Administration said it wants a three-year, Phase III trial to bolster the application dossier.

Lilly received an approvable letter for Arxxant (ruboxistaurin mesylate) in August, and said at the time that it hoped to satisfy the FDA’s request for additional information by tapping the existing data on the product. Now, the company is facing a hefty five-year delay before it could bring the drug to market.

The news is also a blow to ophthalmology specialist Alcon, which signed a long-term co-promotion agreement for Arxxant with Lilly in July.

Arxxant is a first-in-class oral therapy for the treatment of moderate-to-severe non-proliferative diabetic retinopathy. It works by limiting the over-activation of a naturally-occurring enzyme linked to the development of the condition.

The drug was once tipped as a blockbuster medication for Lilly, but had its sales forecasts scaled down after failing to demonstrate efficacy in peripheral neuropathy, another common complication of diabetes.

In a statement, Lilly said it was weighing its options with regard to Arxxant’s future, but also stressed that diabetic retinopathy was a serious unmet medical need for which there are currently no approved treatments.

The company said it still believes in the potential of the compound and, while it decides its fate, current clinical trials of Arxxant will continue, including a study involving patients with macular oedema, another diabetic eye complication. It also said it would not withdraw the New Drug Application (NDA) filed for Arxxant with the FDA.