I consider myself an early adopter, especially when it comes to new technology, ranging from electric cars to surgical heads-up displays. Having been an investigator in the Port Delivery System with ranibizumab (Susvimo, Genentech) trials, I was very excited by the concept of a reservoir that only needs to be refilled every six months or more. Seeing the devastating results of loss to follow-up, this platform seems to be a major mitigation strategy. I remember seeing one wet AMD patient in the Phase II LADDER trial, where device refill-exchanges weren’t mandated, who went over a year without needing a refill and was impressed.

So why hasn’t this platform taken off? On one hand, it’s almost a set it and forget it kind of device at least for six months or longer. One post-hoc analysis of subjects in PAGODA with bilateral DME found that fellow eyes which could be treated with anti-VEGF injections at any time had worse anatomical outcomes than the eyes that received the PDS despite being examined monthly, which makes me wonder if intermittent bolus injections are really a good way to manage disease.

On the flip side, it’s a surgical intervention with more risks than an injection, including  vitreous hemorrhage, implant dislocation, conjunctival blebs, erosion and retraction. More ominous was the nearly threefold increased risk of endophthalmitis (1.6 percent) in the Phase III ARCHWAY for wet AMD. The Phase III PAGODA and PAVILION (diabetic retinopathy) trials had lower rates—especially endophthalmitis, with no cases of it at one year. Since PAGODA and PAVILION came after ARCHWAY, surgical technique refinements may in part account for the decreasing risks. Alternatively, demographics may be playing a role, given the younger mean age in the diabetic trials where the conjunctiva and Tenon’s, which are necessary to cover the implant, are likely thicker. 

There’s also trepidation about the unknown. When I filled out the recent Preferences and Trends Survey from the American Society of Retina Specialists, only a small minority indicated an interest in the PDS. Our clinics have been steadily fine-tuned to deliver injections, which makes it hard to imagine switching gears. More durable agents are available, with injection intervals potentially reaching four or more months already and new ones, such as the tyrosine kinase inhibitors, expected to exceed that. As a result, I think many of us feel that injecting every six months makes more sense than a permanent device that needs to be refilled at about the same interval. 

Ultimately, time will tell where PDS will fall into our armamentarium. Since the device can theoretically deliver various drugs, I can imagine novel therapeutics that may be developed for this platform and help revolutionize retina care. RS