NATIONAL HARBOR, MD. – Just a month before results from the first of several new pivotal trials with a renal denervation device are to be presented, a Food and Drug Administration medical officer speaking at CRT 2020 sponsored by MedStar Heart & Vascular Institute explained which data will most attract the scrutiny of regulators.
Ted Bosworth/MDedge News
Dr. Meir Shinnar
“The FDA is very interested in these devices. We recognize that there is a clinical need, but a reasonable benefit-to-risk relationship has to be established,” said Meir Shinnar, MD, PhD, who works in the division of cardiac devices in the FDA’s Office of Device Evaluation.
The field of renal denervation is expected to heat up again if the results of the SPYRAL HTN OFF MED pivotal trial, planned as a late-breaking presentation at the annual meeting of the American College of Cardiology in March 2020, are positive. However, long-term safety will remain a concern, and positive results will not diminish the rigor with which the relative safety and efficacy of other devices in late stages of clinical testing are evaluated.
“The safety profile is unique to the device design and the procedural technique,” Dr. Shinnar said. For example, vascular injury from the energy employed for denervation, whether radiofrequency or another modality, is an important theoretical risk. A minor initial injury might have no immediate consequences but pose major risks if it leads to altered kidney function over time.
“Most of the follow-up data we have now [with renal denervation devices] is about 1-3 years, but I think long-term safety requires a minimum of 5 years of safety data,” Dr. Shinnar said. “We do not expect all that data to be available at the time of approval, but postmarketing studies will be needed.”
Almost 6 years after the SYMPLICITY HTN-3 trial failed to show a significant reduction in blood pressure among patients with resistant hypertension treated with renal denervation rather than a sham procedure (N Engl J Med 2014;370:1393-401), this treatment is again considered promising. The surprising SYMPLICITY HTN-3 result led to several revisions in technique based on the suspicion that denervation was inadequate.
However, the basic principles remain unchanged. For renal denervation, SPYRAL HTN OFF MED, like the SYMPLICITY HTN 3 study, is employing the Symplicity (Medtronic) device, which has been approved in 50 countries but not in the United States, Canada, or Japan.
SPYRAL HTN OFF MED is designed to provide a very straightforward test of efficacy. Unlike SYMPLICITY HTN-3, which permitted patients to remain on their antihypertensive medications, patients in SPYRAL HTN OFF MED will be tested in the absence of drug therapy (a trial with adjunctive antihypertensive drugs, SPYRAL HTN ON MED, is ongoing). This is a design feature that is relevant to regulatory evaluation.
Although not speaking about the SPYRAL HTN OFF MED trial specifically, Dr. Shinnar noted that “the bar is considered to be higher for a first-line indication than when a device is used as an adjunctive to drug therapy.”
Whether used with or without medications, devices are not likely to receive approval without showing a durable benefit. Dr. Shinnar, citing the surgical studies in which blood pressure control was lost 1-2 years after denervation, said 12 months is now considered a “preferred” length of follow-up to confirm efficacy.
If renal denervation moves forward as a result of the new wave of phase 3 trials, there will still be many unanswered questions, according to Dr. Shinnar, who noted that the FDA convened an advisory committee in December 2018 to gather expert opinion about meaningful safety as well as efficacy endpoints for this modality. One will be determining which populations, defined by age, gender, or phenotype, most benefit.
It also remains unclear whether the first approval will create a standard to which subsequent devices should be compared, according to Dr. Shinnar. Although the FDA recognizes blood pressure reductions as an acceptable endpoint, he believes that documentation of the impact on clinical events will be sought in postmarketing analyses.
“All of the denervation modalities involve class 3 devices that require significant data,” Dr. Shinnar cautioned.
Even if the SPYRAL HTN OFF MED trial is positive on the basis of efficacy, it does not guarantee regulatory approval. Dr. Shinnar described a multifaceted approach to defining an acceptable risk-to-benefit ratio from approved devices, and warned that several points regarding the evaluation of renal denervation devices by the FDA are still being debated internally.
Dr. Shinnar reported no potential financial conflicts of interest.