The FDA is advising eye care providers to evaluate all patients treated with Alcon's now-withdrawn glaucoma device CyPass Micro-Stent.
Alcon pulled the device from the market in August after five-year follow-up data showed 27% of implanted patients suffered a 30% or greater reduction in endothelial cell density.
The data led the FDA to categorize the product withdrawal as a Class I recall and recommend that physicians take steps to monitor implanted patients.
Alcon, a subsidiary of Novartis, indicated that the five-year follow-up data from patients treated with CyPass Micro-Stent contained some alarming findings when it withdrew the product in August, but at that stage no results were publicly available. All we knew is that the data had worsened significantly since the two-year results, when three of the 374 patients suffered 30% endothelial cell loss.
Since then, the data behind Alcon's action have come out. Of the 164 implanted patients enrolled in the smaller extension study, 44 suffered more than 30% loss of endothelial cell density after five years. That means the rate of the adverse event increased from 9% to 27% over three years. Ten percent of patients in the control arm suffered 30% cell loss at five years.
Early analyses of the cause of the jump in the adverse event rate centered on the positioning of the device. The FDA linked device malpositioning to endothelial cell loss when it approved the device in 2016 but the association has grown much stronger since then.
The five-year data reveal a correlation between loss in endothelial cell density and the amount the stent penetrates the anterior chamber of the eye. Visible retention rings on the device indicate the extent to which it extends into the chamber. Among the 55 patients whose devices were positioned so no rings were visible, cell density decreased by 3.1% between the two and five-year assessments. The loss increased to 31.4% among the patients whose devices had three rings visible.
In light of the findings, the FDA is advising eye care providers to assess the positioning of CyPass Micro-Stent in all patients treated with the implant. If two or more rings are visible, the FDA thinks patients should be evaluated for endothelial cell loss as soon as possible. The FDA is recommending all patients be assessed periodically for endothelial cell loss density until their number stabilizes.
With the five-year data suggesting patients will suffer further losses, there is a growing need for ways to stem the damage. The FDA wants surgeons to consider trimming, repositioning and removal but has limited data to support these interventions. Surgeons trimmed the devices of four patients who had three rings visible with positive results but these interventions took place in the week after the original implantation.
The FDA is monitoring the rate of cell loss in patients treated with other minimally-invasive glaucoma devices but the problem looks to be limited to Alcon’s implant. That preliminary finding is a boost for Glaukos, which markets a rival iStent device and saw its stock price increase by 40% when Alcon withdrew CyPass Micro-Stent.