Results of a Pilot Study on the Safety and Early Efficacy of Novel Polymethyl Methacrylate Microspheres and a Hyaluronic Acid Device for the Treatment of Low Back Pain Caused by Degenerative and Diseased Intervertebral Discs of the Lumbar Spine

Background Low back pain (LBP) costs the healthcare system billions of dollars each year. Intervertebral disc (IVD) degeneration is a significant cause of LBP, due to structural defects, biomechanical instability, and inflammation. First-line therapy for patients with LBP includes physical therapy, medication, and steroid injections. DiscSealTM was developed to provide patients who are refractory to first-line therapy with a minimally invasive treatment alternative to invasive surgical procedures. The product is a combination of poly-methyl methacrylate (PMMA) microspheres in hyaluronic acid (HA) that is injected under modified discography into the IVD. Methods Two pain specialist centers in Australia recruited eligible participants who were followed up for 180 days post-procedure. The procedure was conducted using a modified discography technique. Low back and leg pain was reported using the Visual Analogue Scale (VAS) while other endpoints included were Oswestry Disability Index (ODI), Clinician and Patient Global Impact of Change, and Patient Rating of Overall Health Status. The general analytical approach for all endpoints was descriptive in nature and 95% confidence intervals of means were estimated. Results The pilot study achieved its primary objective which was an absence of peri-treatment or post-treatment device-related Serious Adverse Events (SAE) during the first 90 days. There were no device-related serious adverse events recorded throughout the study. The mean LBP percentage change from baseline at 90 and 180 days was -27.0% and -42.3% respectively. The mean ODI percentage change from baseline at 90 and 180 days was -22.3 and -14.2% respectively. End of study improvements shows a 67.8% (20.83) increase in Overall Health Status, as well as positive results for Participant and Clinician Global Impact of Change. These results were achieved based on treating one diseased IVD, although 83.3% of patients were diagnosed with multiple diseased IVDs. Conclusions The results from this pilot study showed that DiscSealTM is safe and well-tolerated. Early efficacy shows that DiscSealTM may be a promising treatment option for people suffering from discogenic LBP that have not responded to first-line treatment options. A larger, statistically powered study where all diseased discs are treated should be completed to validate the promising results from this early feasibility study.


Introduction
Low back pain (LBP) is a major healthcare problem causing more disability than any other medical condition 1 2 3 4 1 5 [1]. In developed countries, LBP is the second most common reason where patients seek medical treatment after a cough [2]. Patients with LBP experience pain, disability and loss of productivity leading to significant psychological, social, and economic burden. The direct and indirect costs of LBP in the United States alone are greater than $100 billion per year [1]. The lifetime prevalence of LBP is reported to be 60 -70% [3]. LBP is a World Health Organisation priority disease, with incidence and burden on health resources expected to increase as the world population ages [3].
Intervertebral disc (IVD) disease is a significant cause of pain in LBP patients and involves degenerative changes to the IVD leading to structural defects, biomechanical instability, and inflammation [4].
First-line therapy for patients with LBP includes physical therapy, oral pain relievers, and steroid injections [5]. Treatment options for patients who fail first-line therapy are limited to invasive surgical procedures such as total disc replacement or spinal fusion [6]. The recovery from such surgical procedures can be lengthy and may result in a permanent loss of flexibility. Many surgical approaches for LBP have limited or transient efficacy and there is little evidence to show which procedures work best for particular indications [4]. Hence, minimally invasive treatment options for LBP are urgently needed.
This study aimed to investigate the safety, tolerability, and exploratory efficacy of a novel intra-discal formulation for the treatment of degenerative and diseased intervertebral disc (IVD) of the lumbar spine.
The primary objective of the study was to show freedom from any peri-treatment or post-treatment devicerelated Serious Adverse Events (SAEs) during the first 90 days. A secondary aim of the study was to test the efficacy of the DiscSeal TM device.

Investigational product
The DiscSeal TM product platform is based on repurposing of dermal fillers and is a colloidal form of a viscous gel composed of cross-linked Poly (methyl methacrylate) (PMMA) microspheres (with diameters between 53-106 μm) and a proprietary formulation of aqueous buffered, high molecular weight sodium hyaluronate (HA), supplied as sterile 1.0 mL, single-use, pre-filled syringes. The intended mode of action of the product is to be injected directly into the nucleus pulposus (NP) of the IVD of the lumbar spine with the PMMA microspheres providing structural support, volume, bulk, and will potentially seal annular fissures of the IVD. DiscSeal TM could potentially also retard or delay further degradation or continued loss of IVD height and/or volume. The HA in DiscSeal TM is biodegradable and is intended to serve as a carrier for the microspheres, provide transition filling and flow properties, and supply viscosity for injection and retention of PMMA in the NP. The HA selected for DiscSealT M is not cross-linked and is made from recombinant processes and does not contain animal-derived products therefore there is no risk of transmissible spongiform encephalopathies (TSE)/bovine spongiform encephalopathy (BSE). It is believed the HA will be biologically absorbed within a few weeks of the procedure, leaving the PMMA microspheres within the NP. Phosphate Buffered Saline (PBS) and water are added as the aqueous buffer. It is postulated that the microspheres remaining in the IVD are either encapsulated by fibrotic tissue or native new collagen.
The biocompatibility and biological safety of DiscSeal TM has been investigated in several animal models. Large animal studies involving sheep resulted in no adverse health or neurological findings when followed up for eight months. Necropsy observations revealed no visible lesions or other abnormalities. Based on the histopathologic analysis, it was concluded that DiscSeal TM appears to be safe at eight months posttreatment via IVD injection with no evidence of tissue reaction/inflammation at the treated IVD. DiscSeal TM also appeared to stay localized primarily in the NP and annulus fibrosus (AF) of treated IVDs. DiscSeal TM also appeared to have no adverse effects on adjacent tissues and there was no migration of microspheres in any of the animal studies performed.
PMMA and HA are components of a large number of devices that have regulatory clearance by the Food and Drug Administration, European Medicines Agency, and Therapeutic Goods Australia and their safety profile is well known. Percutaneous vertebroplasty and kyphoplasty vertebral augmentation procedures with PMMA based bone cement have been widely used to treat painful vertebral compression fractures for decades with leaks outside the confines of the vertebral body often occurring but rarely resulting in clinical sequelae. PMMA in DiscSeal TM is delivered in much smaller volumes and as preformed, hardened microspheres, designed to decrease the risk of leakage, instead of widely used liquid, non-cured PMMA.

Study design
The study was a prospective, single-arm feasibility clinical study conducted at two Australian centers between 30 September 2019 and 22 January 2020. The study was reviewed and granted approval by Bellberry Ltd Human Research Ethics Committee (HREC Application No. 2019-07-595) prior to recruitment, and was prospectively registered in the WHO Primary Registry and Australia New Zealand Clinical Trials Registry (ANZCTR) (Trial ID: ACTRN1269001145190).

Participant selection
Males and females aged between 18 to 70 years were recruited if they had been diagnosed with chronic LBP (VAS ≥ 4) for at least six months where the etiology of their pain was predominantly discogenic in the lumbar spine (Degenerative Disc Disease, Internal Disc Disruption, or nonspecific Discogenic Disease) and they had failed at least six weeks of conservative management. Refer to Table 1 for the full list of eligibility criteria.

Inclusion Criteria
1 Male or female between the age group of 18-70 years (inclusive); If female, must have a negative pregnancy test at the time of treatment, be actively practicing contraception or abstinence, be surgically sterilized, or be postmenopausal.
2 Participant presently has degenerative disc disease, as evidenced by I. History and clinical findings suggestive of degenerative disc disease (DDD), internal disc disruption (IDD) or non-specific discogenic disease II. At least Modic Type 1 changes on MRI [7] III. Disc height of ≥50% of normal disc height (defined as the average height of adjacent normal discs) based on anteroposterior and lateral lumbar spine radiographs (plain X-ray images) 3 Visual Analog Scale (VAS) low back pain score of back pain of at least ≥ 4 [8] 4 Oswestry Disability Index (ODI) >21% (i.e., at least moderate disability) [9] 5 At least one lumbar disc with Pfirrmann Grade II-IV or Modic Type 1-2 changes without annular rupture [7] 6 No annular tears present in the disc planned for treatment which reach the distal periphery of the annulus with the potential for

Study procedure
All study participants were consented prior to screening. Medical history and concomitant medications were recorded. Baseline assessments included a full physical examination, vital signs, and the following screening questionnaires: Oswestry Disability Index (ODI), Visual Analog Scale (VAS) for pain, and Overall Health Score (OHS). Magnetic resonance imaging (MRI), and X-rays of the lumbar spine that were no less than six months old were used to identify disc degeneration. Participant data were reviewed by an independent medical monitor to assess eligibility. All eligible participants were enrolled for treatment.
DiscSeal TM injections were performed by qualified and experienced investigator clinicians who used their own standard of care to prepare and manage the participant for the procedure (including infection and pain control). Procedures were conducted under general sedation at the discretion of the investigator. Treatment was administered using 'modified discography', where a minimum amount of contrast was first injected into the IVD to determine if the disc could contain DiscSeal TM in situ and to confirm needle tip placement for the optimal injection process. As an additional safeguard, the DiscSeal TM material, which is not radiopaque, was transferred into a sterile receiving syringe prior to injection to ensure adequate flow and viscosity characteristics of the product. DiscSeal TM was injected into the target disc's nucleus under fluoroscopic image guidance via a 20 g Chiba needle at a rate similar to that of contrast injection during discography. DiscSeal TM was delivered until the investigator felt that the disc could not hold any more or the full 2.0 mL was administered. A target amount of 1.0 to 2.0 mL was described as it is the common range for other intradiscal treatments and the goldilocks amount that would have an effect without going beyond the tactile injection pressures.
A two-week pause was observed prior to doing a subsequent procedure for the first two participants to allow the independent Medical Monitor to perform a safety review.
Participants treated with DiscSeal TM were followed for 180 days, with study visits at seven days, 14 days (phone check-up for safety), 42 days, 90 days, and 180 days post-treatment (refer to

Statistical analysis
While the study was not powered for sample size calculations, the number of participants enrolled in the study was considered sufficient to adequately characterize the general safety profile of this type of device. Hence, descriptive statistics were used to assess mean, range, median, minimum and maximum for continuous variables and frequency counts and percentages for categorical variables. Missing values were not imputed, and baseline values were defined as the last available non-missing assessment prior to DiscSeal TM injection.
Secondary endpoints were summarized by study visit for the total score, absolute change from baseline, and percentage change from baseline with 95% confidence intervals of the mean estimated.
Three patient populations were defined pre-study for investigational analysis post-treatment. The Safety Population was to include all participants who received the DiscSeal TM injection. The Intent to Treat (ITT) population was to include all participants who received the DiscSeal TM injection and had at least one postbaseline measurement of VAS or ODI. The Per Protocol (PP) Population was to be a subset of the ITT population without major protocol deviations likely to affect the outcome.

Results
Ten participants consented to the study, of which four did not meet the eligibility criteria. Six participants were enrolled for treatment with DiscSeal TM . The mean participant population age was 38.8 ± 10.0 years, and the majority of subjects were male (83.3%, 5/6), and Caucasian in ethnicity (83.3%, 5/6). The mean height, weight, and BMI of participants were 174.3 ± 7.4 cm, 86.5 ± 17.7 kg, and 28.2 ± 4.2 kg/m 2 respectively. Full demographic information is available in Table 1. Five out of six (83%) participants were assessed with having multi-disc disease. However, each participant had only one disc treated with DiscSeal TM at the request of the ethics committee. The L4/L5 lumbar disc was treated in four participants, while two participants had their L5/S1 discs treated. The mean procedure time was 10.8 minutes with a range between 6-27 minutes. Refer to Table 3 for details around the procedure in the clinical investigation.  All participants who underwent the DiscSeal TM procedure were included in the Safety Population. The ITT population included all subjects in the study, and the PP population included all except one. The participant excluded from the PP population (Participant 02-002) exceeded the daily morphine equivalent dosage of oxycodone for an operation post-procedurally which met exclusion criteria 30 ( Table 1). Data will be reported with a distinction between ITT and PP populations.
The primary objective of the study was achieved and there were no peri-or post-treatment device-related SAEs throughout the study. Adverse events were recorded from the time of participant consent until study exit. A total of 16 adverse events were reported across all study participants (refer to    The mean LBP VAS percentage change from baseline was -27.0% and -42.3% at 90 and 180 days respectively (refer to Table 6 and Figure 2). The mean LBP VAS decreased every subsequent visit made to the clinical site after the first visit. The mean leg pain VAS percentage change from baseline was -47.0% and -36.6% at 90 and 180 days respectively (refer to Table 7). End of study improvements in OHS increased 67.8% (Table 8), as well as positive results for Patient and Clinician Global Impact of Change, which are represented in Table 9 and Table 10, respectively. In the PP Population, improvements from baseline were generally greater. Mean ODI percentage change from baseline was -39.6% and -27% at 90 and 180 days respectively ( Table 5). The overall mean LBP VAS percentage change from baseline was -32.4% and -45% at 90 and 180 days respectively ( Table 6), and the percentage change from baseline of OHS was 86.3% ( Table 8). The overall mean leg pain VAS percentage change from baseline was -56.4% and -38.14% at 90 and 180 days respectively (Refer to Table 7). Physical examination and vital sign changes were unremarkable.

Discussion
This first-in-human, interventional, pilot study shows that the novel formulation of PMMA microspheres and HA (DiscSeal TM ) is a safe medical device that may be used for the treatment of discogenic LBP. To determine safety, the study's primary objective, participants were closely monitored for adverse events. The 16 adverse events (AEs) that were reported were comparable to the AEs noted in other, similar intradiscal interventions [11] and were expected considering the close scrutiny under which participants were placed. Both SAEs reported were determined to be unrelated to the study device or procedure. AEs that were reported as being related to the study procedure and/or device were expected (for example, localized pain at the injection site). The results from the DiscSeal TM safety study are comparable with other injectables such as platelet-rich plasma (PRP) with a sustained reduction in LBP (42.3% decrease) at six months posttreatment [11][12][13][14], and a significant improvement for patients who are refractory to first-line therapy but have no alternative other than to continue on oral, Rx or pain management with limited success, -10.6 out of 100 points VAS reduction with conservative care management [14].
Participant satisfaction was also in line with other studies with 33.3% of participants reporting minimal improvement, while 16.7% reported their pain much improved and another 16.7% reported that their pain very much improved at the end of the study. These results are promising considering the confounding complications that occurred with some participant data.
Participant 01-006 had her results complicated due to confounding circumstances. The participant had to flee from a bushfire prior to the 42-day follow-up and reported an adverse event of increased low back pain from lifting heavy objects whilst trying to save their house. The participant reported an 8 out of 10 low back pain during the 42-day visit which reduced markedly to 3 out of 10 at the 90-day visit. The participant returned to work as a police officer after the 90-day visit and subsequently reported a higher LBP VAS of 7 out of 10 at the 180-day visit.
Mixed results were also seen for the participant 01-004 who reported a 4 out of 10 for LBP at day 42 followed by a 7 at day 90 and a 1 out of 10 at day 180. The participant did report an AE prior to the 90-day visit for increased pain on the hip and low back due to overexerting themselves at the gym.
Participant 02-002 was removed from the per-protocol population, primarily due to taking too much of the prohibited medication oxycodone. The medication was given for pain relief after a microdiscectomy procedure carried out for the SAE "L4/L5 disc extrusion". 02-002 also had multiple confounding factors that led to inconsistent results, indicating a 9 out of 10 for LBP VAS at the 42-day visit, 7 out of 10 at the 90-day visit, and a 5 out of 10 for LBP VAS (a decrease in 3 scores from screening) at the 180-day visit.
As the study was first-in-human, the researchers were limited to treating one diseased disc per participant by the ethics committee. Five out of the six participants had multiple diseased discs. The one participant who had a single diseased disc (participant 01-002) reported remarkable results. Participant 01-002 had been managing their pain using medication for 8.8 years. He was able to cease taking his pain medication from 90 days post-procedure onwards and maintained reduced pain levels throughout the end of the study. The participant scored a 5 out of 10 VAS for LBP and 34 for ODI at baseline. He subsequently reported 0 pain from day 42 to the end of the study at day 180 post-procedure. Additionally, he reported a 2 for ODI at the 42-day visit and 0 for the 90-day and 180-day visits. The participant's overall health score went from 45 at baseline to 95 at the study exit.

Conclusions
The results from this pilot study show that DiscSeal TM is safe and well-tolerated with early efficacy, indicating that DiscSeal TM may be a promising minimally invasive treatment option for people suffering from discogenic LBP, who have tried and have failed first-line therapy. Due to the small sample size, the confidence in the results are limited, and therefore a larger, longer and statistically powered study that allows multiple diseased, pain-generating discs treatment, should be conducted.