Corneal Crosslinking Drug Gets Cautious Nod From FDA Panel

February 27, 2015

An advisory panel of the US Food and Drug Administration (FDA) on February 24 recommended approval of a new drug that treats two eye disorders with corneal collagen crosslinking, but waved some yellow caution flags in the process.

The drug is riboflavin ophthalmic solution (Photrexa, Avedro), which is irradiated with ultraviolet A (UVA) light from an electronic device (KXL System) after it is applied to the cornea. One version of this ophthalmic solution, Photrexa Viscous, also contains dextran.

Avedro seeks FDA approval to use the drug to treat both progressive keratoconus and corneal ectasia after refractive surgery such as Lasik. A degenerative disease, keratoconus causes the cornea to thin out and bulge into a conelike shape, resulting in myopia, astigmatism, and sometimes blindness. The same pathology occurs in postoperative corneal ectasia.

Corneal collagen crosslinking attempts to halt the progression of both eye disorders by strengthening chemical bonds in the cornea. In so doing, it can prevent the need for a corneal implant.

Study One Device, Market Another?

Avedro's technology for corneal collagen crosslinking is already available in Europe and Asia. In 2011, the FDA granted orphan drug status to the company's riboflavin ophthalmic solution and KXL System. However, the product has been slow to gain market clearance here. In March 2014, the FDA sent back Avedro's application with a request for more information.

The FDA advisory panel that considered Photrexa/KXL System on February 24 also wanted to know more. The group consisted of the agency's Dermatologic and Ophthalmic Drugs Advisory Committee and the Ophthalmic Devices Panel of the Medical Devices Advisory Committee.

Several panel members complained that the UVA irradiation device that Avedro intends to market is not exactly the same one used in the clinical studies submitted to the FDA.

"They have no patients treated with the machinery that they're trying to get approved, and we don't know whether there are some subtle differences in the machinery design compared to the one on which the study was based," said Stephen Feman, MD, professor emeritus at Saint Louis University School of Medicine in Missouri, who opposed approving the drug. "That may make a difference." Dr Feman suggested that the manufacturer redo its studies with the KXL System.

Panel members also cited a lack of data about long-term efficacy, and efficacy in pediatric patients.

In the end, however, a majority of the FDA advisors agreed that the data on efficacy and safety were good enough — and the patient need great enough — to recommend approval of Photrexa/KXL System. The panel voted 10 to 4 with one abstention to endorse the drug for progressive keratoconus, and 6 to 4 with 4 abstentions and 1 uncast vote for corneal ectasia.

Several panel members suggested highlighting data deficiencies in the product's label.

"I would like to add to the labelling for patients as well as physicians that this machine (the KXL System) wasn't used in the study," said Jayne Weiss, MD, chair of the ophthalmology department at the Louisiana State University Health Sciences Center in New Orleans.

Jeremiah Brown, MD, director of ophthalmology research at the Brown Retina Institute in Schertz, Texas, said that he wanted a statement to the effect that the drug's long-term effects and durability after 12 months are unknown.

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