Additional Data Confirm Positive Results for Clinical Trial of ReActiv8®

Additional data confirm clinically important, statistically significant, and lasting improvement in pain, disability, and quality of life for people with Chronic Low Back Pain and limited treatment options

Dublin – Ireland, 4 December 2015 – Mainstay Medical International plc (Mainstay or the Company, listed on Euronext Paris: MSTY.PA and ESM of the Irish Stock Exchange: MSTY.IE), a medical device company focused on bringing to market ReActiv8®, a new implantable neurostimulation system to treat disabling Chronic Low Back Pain (CLBP), today announced additional results from the ReActiv8-A Clinical Trial, an international, multi-centre, prospective, single arm trial to gather data for a submission for CE Marking for ReActiv8. The additional results are consistent with those released on 31 August, 2015 and continue to show clinically important, statistically significant and lasting improvement in pain, disability and quality of life in this clinically challenging population.

NOTE: Results in this release have been updated including data from 13 subjects who had not yet reached the 180 day follow-up at the time of the August press release. A full description of the ReActiv8-A Trial and updated results are provided in an addendum to this release.
ReActiv8 is for treatment of people who suffer from CLBP, have attempted most or all available treatment options, and are not candidates for back surgery or spinal cord stimulation. The ReActiv8-A Trial population was relatively young (mean age 43.9 years) and had a long history of low back pain (mean 13.8 years). All of the subjects had attempted physical therapy, and 70% were taking opioids for back pain. The results presented are based on data from the first 47 subjects implanted in the ReActiv8-A Trial of whom 46 have reached the 90 day follow up and 45 have reached the 180 day follow up.
Results highlights:

? Clinical performance of ReActiv8 at 90 days compared to baseline for all subjects is:
o 63% with clinically important improvement in back pain defined as =2 point reduction on the 0-10 Numerical Rating Scale (NRS) for low back pain1 measured on the day.
o 57% responder rate for pain: A responder is defined as a subject with a clinically important improvement in mean of prior 7 days NRS with no clinically significant increase in medications taken for low back pain.
o 57% with a clinically important improvement2 in disability on the Oswestry Disability Index (ODI).
o 67% with a clinically important improvement3 in quality of life on the EQ-5D scale.
? Clinical performance at 90 days is even better for the group of subjects who do not receive financial compensation for being out of work due to their back pain. For those 32 subjects the results are:
o 72% with clinically important improvement in low back pain NRS on the day.
o 69% responder rate for pain.
o 63% with clinically important improvement in ODI.
o 69% with a clinically important improvement in EQ-5D.
? Improvements in low back pain, disability and quality of life were generally consistent or improved at 180 days (n=45). Paired data for all subjects at 90 and 180 days respectively are:
o 63% and 58% with clinically important improvement in low back pain NRS on the day.
o 57% and 60% with clinically important improvement in ODI.
o 67% and 73% with clinically important improvement in EQ-5D.
o 61% and 67% reported >50% Percent Pain Relief.
? Adverse Events (AEs) incidence and type were comparable to AEs in clinical trials reported for other neurostimulation devices, with no unanticipated AEs and no serious AEs related to the device, therapy or procedure.
? The observed lead migration incidence (<1%) demonstrates that the ReActiv8 lead mitigates the risk of lead migration identified with commercially available neurostimulation leads in the earlier Feasibility Trial.
? In the August press release, the Company announced a modification of the implant technique with different lead routing developed to mitigate the risk of breaks of the wires inside the lead, which had been observed in the ReActiv8-A Trial. Experience to date with the first 14 subjects implanted with the modified approach (new implants and revisions) are encouraging.
T
he Company announced on 2 November, 2015 that a submission for CE Marking was made.
Subjects continue to be enrolled in the ReActiv8-A Trial to gather additional data on performance and safety which the Company plans to incorporate into the Post Market Clinical Follow Up. To date there have been 6 additional subjects implanted in the ReActiv8-A Trial.

- ReActiv8-A Trial Results Below -
Addendum: ReActiv8-A Trial Description and Results
Subjects were enrolled in the ReActiv8-A Trial if they continued to experience disabling CLBP despite at least 90 days of medical management, which included at least physical therapy and drugs (most subjects had attempted many other treatments including chiropractic, massage, and acupuncture). In addition, subjects had no identifiable spine pathology that could be the clear cause of their CLBP, had no prior spine surgery, and were not candidates for spine surgery or spinal cord stimulation. Back pain was assessed using a Numerical Rating Scale (NRS) in which subjects were asked to grade their low back pain from 0 (no pain) to 10 (worst imaginable pain). Subjects were instructed to not change their medications for low back pain until after the 90 day end point.
Subjects were implanted with ReActiv8 in a short surgical procedure. After approximately 14 days, subjects began stimulation sessions with ReActiv8 for 30 minutes each morning and evening, and outcome data collection is at 90 days, 180 days and annually thereafter.

Baseline Characteristics & Outcomes available in pdf attached

Adverse Events
Adverse events are adjudicated by an independent Clinical Events Committee. As of the most recent adjudication in November, there were 67 reported AEs related to the device, therapy or procedure. There were three Serious Adverse Events (SAEs), none of which were related to the device, therapy or procedure. There were no unanticipated AEs or unanticipated device related AEs. The AE incidence and type were comparable to AEs in clinical trials reported for other neurostimulation devices.
6 See, for example, https://clinicalTrials.gov/show/NCT01609972 and https://clinicalTrials.gov/show/NCT01923285
7 Dworkin, R. H., Turk, D. C., Peirce-Sandner, S., Baron, R., Bellamy, N., Burke, L. B., … Witter, J. (2010). Research design considerations for confirmatory chronic pain clinical Trials: IMMPACT recommendations. Pain, 149(2), 177–93.

Lead Related Events
To date, the ReActiv8 lead has shown only one instance of lead migration (dislodgement) out of 134 implanted leads (including those implanted in revision procedures) for a lead migration incidence of less than 1%. These results demonstrate that the ReActiv8 lead mitigates the risk of lead migration identified with commercially available neurostimulation leads in the earlier Feasibility Trial.
In the August press release, the Company announced a modification of the implant technique with different lead routing developed to mitigate the risk of breaks of the wires inside the lead, which had been observed in the ReActiv8-A Trial. Experience to date with the first 14 subjects implanted with the modified approach (new implants and revisions) are encouraging.

Summary
These results demonstrate that for a population of people with long term Chronic Low Back Pain and limited treatment options, treatment with ReActiv8 delivers clinically important, statistically significant, and lasting improvement in pain, disability, and quality of life.
PR and IR Enquiries:
Consilium Strategic Communications (international strategic communications – business and trade media)
Chris Gardner, Mary-Jane Elliott, Matthew Neal, Hendrik Thys,
Tel: +44 203 709 5700 / +44 7921 697 654
Email: mainstaymedical@consilium-comms.com
FTI Consulting (for Ireland)
Jonathan Neilan, Tel: +353 1 663 3686
Email: jonathan.neilan@fticonsulting.com

FTI Consulting (for France)
Astrid Villette,
Tel: +33 1 47 03 69 51
Email: Astrid.Villette@fticonsulting.com
Investor relations:
The Trout Group LLC
Jillian Connell, Tel: +1 646 378 2956 / +1 617 309 8349
Email: jconnell@troutgroup.com
ESM Advisers:
Fergal Meegan or Barry Murphy, Davy
Tel: +353 1 679 6363
Email: fergal.meegan@davy.ie or barry.murphy2@davy.ie

About Mainstay
Mainstay is a medical device company focused on bringing to market an innovative implantable neurostimulation system, ReActiv8®, for people with disabling Chronic Low Back Pain (CLBP). The Company is headquartered in Dublin, Ireland. It has subsidiaries operating in Ireland, the United States and Australia, and is listed on Euronext Paris (MSTY.PA) and the ESM of the Irish Stock Exchange (MSTY.IE).
About the ReActiv8-A Trial
The ReActiv8-A clinical trial is a prospective single arm clinical trial with up to 96 subjects at sites in Australia and Europe. Outcome measures for the ReActiv8-A clinical trial are assessed at a three month endpoint after activation of stimulation and compared to baseline prior to implant. Further details can be obtained at https://clinicaltrials.gov/show/NCT01985230.

About Chronic Low Back Pain
One of the recognised root causes of CLBP is impaired control by the nervous system of the muscles that dynamically stabilise the spine in the lower back, and an unstable spine can lead to back pain. ReActiv8 is designed to electrically stimulate the nerves responsible for contracting these muscles and thereby help to restore muscle control and improve dynamic spine stability, allowing the body to recover from CLBP.
People with CLBP usually have a greatly reduced quality of life and score significantly higher on scales for pain, disability, depression, anxiety and sleep disorders. Their pain and disability can persist despite the best available medical treatments, and only a small percentage of cases result from an identified pathological condition or anatomical defect that may be correctable with spine surgery. Their ability to work or be productive is seriously affected by the condition and the resulting days lost from work, disability benefits and health resource utilisation put a significant burden on individuals, families, communities, industry, and governments.
Further information can be found at www.mainstay-medical.com
ReActiv8 is an investigational device and is not approved for commercialisation anywhere in the world.
CAUTION – in the United States, ReActiv8 is limited by federal law to investigational use only.

Forward looking statements
This announcement includes statements that are, or may be deemed to be, forward looking statements. These forward looking statements can be identified by the use of forward looking terminology, including the terms “anticipates”, “believes”, “estimates”, “expects”, “intends”, “may”, “plans”, “projects”, “should” or “will”, or, in each case, their negative or other variations or comparable terminology, or by discussions of strategy, plans, objectives, goals, future events or intentions. These forward looking statements include all matters that are not historical facts. They appear throughout this announcement and include, but are not limited to, statements regarding the Company’s intentions, beliefs or current expectations concerning, among other things, the Company’s results of operations, financial position, prospects, financing strategies, expectations for product design and development, regulatory applications and approvals, reimbursement arrangements, costs of sales and market penetration.
By their nature, forward looking statements involve risk and uncertainty because they relate to future events and circumstances. Forward looking statements are not guarantees of future performance and the actual results of the Company’s operations, and the development of its main product, the markets and the industry in which the Company operates, may differ materially from those described in, or suggested by, the forward looking statements contained in this announcement. In addition, even if the Company’s results of operations, financial position and growth, and the development of its main product and the markets and the industry in which the Company operates, are consistent with the forward looking statements contained in this announcement, those results or developments may not be indicative of results or developments in subsequent periods. A number of factors could cause results and developments of the Company to differ materially from those expressed or implied by the forward looking statements including, without limitation, the Company’s ability to obtain CE Marking for ReActiv8®, the initiation and success of the ReActiv8-B Clinical Trial, general economic and business conditions, the global medical device market conditions, industry trends, competition, changes in law or regulation, changes in taxation regimes, the availability and cost of capital, the time required to commence and complete clinical trials, the time and process required to obtain regulatory approvals, currency fluctuations, changes in its business strategy, political and economic uncertainty. The forward-looking statements herein speak only at the date of this announcement.