The U.S. FDA granted Gtx Medical BV a breakthrough device designation for its implantable Go-2 Targeted Epidural Spinal Stimulation (TESS) system. The device enabled patients who had sustained traumatic spinal cord injuries to regain voluntary control over previously paralyzed muscles and walk again four or more years after paralysis, according to a study previously published in Nature.

The company, based in Eindhoven, Netherlands, and Lausanne, Switzerland, plans to start the first clinical trial for TESS in 2021. Gtx expects to begin a clinical trial for its wearable Lift System later this year. The first generation of the technology for the Lift System, which delivers noninvasive electrical spinal stimulation therapy to improve or restore upper limb and hand function, received breakthrough device designation in 2017.

“The FDA breakthrough device designation is an important regulatory milestone and underscores the transformative potential of the Go-2 system and the unmet medical need it addresses,” said Gtx Chairman Jan Öhrström. “With breakthrough device designation for the implantable Go-2 system and for the non-invasive LIFT technology, we are now on an accelerated pathway. Both designations support our aim to expeditiously bring Gtx’s innovative therapies for improving functional recovery, enhancing quality of life and independence of people with spinal cord injury.”

Clinical trials

The next year will see the rapid launch of several clinical trials for the company’s technology.

Gtx is still working out the details for the Go-2 trials, but the parameters are clear.

“Roughly, we anticipate 60 to 80 implants over the different premarket studies, starting in 2021,” Öhrström told BioWorld. “We may be conducting a pilot study before the pivotal study to build up the learning experience and we expect the first results by the end of 2021 and market approval around 2024.”

The company plans to conduct the Go-2 trials in centers in both the U.S. and Europe.

Trials for the Lift NESS therapy have been on pause for several years. Funding limitations had kept the company that originally developed the transcutaneous stimulator Gtx now calls Lift from initiating a multicenter clinical trial, despite very encouraging feasibility studies, Öhrström explained.

“The combined resources of Neurorecovery Technologies Inc. and Gtx were required to bring this project to fruition in a manner than promises to yield a positive impact on the options available to treat cervical SCI,” he said.

San Juan Capistrano, Calif.-based Neurorecovery Technologies and Gtx merged in October 2019.

The Up-Lift study, which is expected to begin enrollment later in 2020, will be the “first hypothesis-driven, statistically powered study to fully assess the safety and effectiveness of this therapy,” Öhrström said.

The technology

The Go-2 system facilitates reconnection of the brain with paralyzed leg muscles following spinal injury using electrical stimulation that activates intact, but silent pathways in the spinal cord to control movement of the lower limbs.

The Go-2 device is a paddle lead with 16 electrodes, like spinal cord stimulators used to control pain. In the Go-2, however, the electrode placement and dimensions of the paddle lead are tailored to promote locomotion.

Pre-implant imaging helps determine the precise location for each electrode in the lumbar area of the spinal cord to control leg movement.

“During the implant, Initial electrical measurements are performed to position the paddle lead over the correct area of the spine. During the activation phase, after the implanted components are settled, a precise titration is performed,” Öhrström explained. “At that time, individual electrodes or combinations can be linked to specific roots, resulting in a natural sequence of stimulations when the therapy is switched on.”

The electrodes provide burst or spatiotemporal stimulation, which does not interfere with the patient’s proprioception the way continuous epidural electrical stimulation (EES) does.

“These stimulations are delivered in a way that is felt by the user as more natural. He/she remains in control. TESS requires much shorter stimulation sequences for each root compared to continuous EES, which allows the proprioception to remain intact,” he added.

Bluetooth signals from foot sensors transmit the stimulation pace to the implanted device, allowing patients to learn how to use the sequence to meet their needs.

Patients received the implants in the Nature study between 2016 and 2018 and have continued to improve. All three of the patients featured regained the ability to walk using a walker. One of them can now walk independently in a community (non-lab) setting. The current records for patients with the implants are walking 500 meters or training for 90 minutes on a treadmill, Öhrström said.

“Also, of note is the further impact measured when closed loop stimulation was added to the system. The technological advance allows the [implantable pulse generator] to respond and engage muscle groups based on certain markers of a participant’s movement. This first in the field addition makes training beyond the traditional rehabilitation timelines viable and after implementation patients were able to make impressive gains in addition to those achieved through rehabilitation alone.”

The goal is for the implant to assist patients in their daily lives, which has been seen. Patients have shown progress in areas beyond walking, including improved trunk, spasticity and cardiovascular control; fewer pressure sores, better bowl, bladder and sexual function; and better mental health in general, according to Öhrström.

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