The two US FDA approvals of neurostimulators over the past few days show the sheer variety of uses to which this technique can be put. On Friday the agency approved Respicardia’s Remede system, which stimulates the phrenic nerve to help sleep apnoea patients breathe, and yesterday it was Livanova’s turn, with a new implantable generator, SenTiva, gaining US approval for drug-resistant epilepsy.
Over the past three years the US regulator has approved neurostimulators for conditions including dry eye disease and obesity (see table below). And plenty of research is being conducted in other conditions; neurostimulation could come to be even more versatile in the future.
Sleep apnoea is generally treated with continuous positive airway pressure, bi-level positive airway pressure or adaptive servo-ventilation systems, all of which are strapped to the patient’s face and force pressurised air into their lungs as they sleep. They are generally uncomfortable and restrictive, and compliance is low.
So there ought to be a market for Respicardia’s device. Remede is implanted in the upper chest and, when it detects that the patient has not taken a breath for too long, it delivers an impulse to the phrenic nerve, causing the diaphragm to contract and the patient to inhale.
Central vs obstructive
While patients will be keen, the market is limited: the device is indicated for moderate to severe central sleep apnoea, a separate condition to the more common obstructive sleep apnoea. According to the private company only the central form is neurological in nature, so Remede will have little use beyond this population (Respicardia looks to the US, September 14, 2016).
Intriguingly, however, some groups are attempting to develop a neurostimulator for obstructive sleep apnoea. Nyxoah is developing a device called Genio, designed to be implanted in the chin area with electrodes placed in contact with both branches of the hypoglossal nerve; stimulating this nerve causes airways to open, Nyxoah says.
The group, based in Belgium, raised €18m ($20m) last year from Gilde Healthcare Partners and the Société Régionale d’Investissement de Wallonie and says this cash ought to be enough to get the device CE marked; US approval would follow on from there.
US-based Imthera Medical is also conducting trials of a hypoglossal nerve stimulator for obstructive sleep apnoea.
Viva las vagus
Livanova is an old hand at neurostimulation, with its vagus nerve stimulator first approved for epilepsy back in 1997 when the company was known as Cyberonics. It now has approval for a new form of the VNS system, comprising the SenTiva implantable generator and VNS therapy programming system, a handheld wireless device that connects to an app on a tablet computer.
This new system permits doctors to customise VNS therapy for patients with drug-resistant epilepsy.
Vagus nerve stimulation has not been pursued much beyond epilepsy, though it is sometimes used off-label for Lennox-Gastaut syndrome. Exploratory trials have been conducted by academic researchers in asthma, anxiety, stroke and traumatic brain injury, and Setpoint Medical is pursuing vagus stimulation for rheumatoid arthritis (SetPoint off to a good start in the clinic, July 21, 2016).
This sector will bear watching to see how the next neurostimulator to reach market will work, and what it will treat.
|Selected US neurostimulator approvals of the last three years|
|Device||Company||Type of stimulator||Indication(s)||Regulatory pathway||Decision||FDA review time (months)|
|Sentiva||Livanova||Vagus nerve stimulator||Epilepsy||Unknown||Oct 9, 2017||Unknown|
|Remede||Respicardia||Phrenic nerve stimulator||Sleep apnoea||PMA - first approval||Oct 6, 2017||Unknown|
|TrueTear||Allergan||Intranasal tear neurostimulator||Dry eye disease||510(k) clearance (de novo)||Apr 24, 2017||9.6|
|Gammacore||Electrocore||External vagus nerve stimulator||Headache||510(k) clearance (de novo)||Apr 14, 2017||18.0|
|Axium||Abbott (then St Jude)||Spinal cord stimulator||Chronic pain||PMA - first approval||Feb 26, 2016||12.9|
|Algovita||Nuvectra||Spinal cord stimulator||Chronic pain||PMA - first approval||Nov 20, 2015||23.1|
|Brio||Abbott (then St Jude)||Deep brain stimulator||Parkinson’s disease and essential tremor||PMA - first approval||Jun 12, 2015||13.2|
|Senza||Nevro||Spinal cord stimulator||Chronic pain||PMA - first approval||May 8, 2015||19.2|
|Maestro||Enteromedics||Vagus nerve stimulator||Obesity||PMA - first approval||Jan 14, 2015||18.8|