Mesoblast Ltd (MELBOURNE, Australia), a regenerative medicine company developing treatments for orthopaedic conditions, including the commercialization of a unique adult stem cell technology aimed at the regeneration and repair of bone and cartilage, announced that its allogeneic cell therapy was safe and effective in preclinical trials for fusion of the cervical spine in the neck. Mesoblast is currently in phase II clinical trials for fusion of the lumbar spine and, based on these new results, will extend its market opportunity to cover the entire spectrum of spinal fusion. Subject to US FDA approval, Mesoblast's therapy will eliminate the need for autograft, which requires a second operation and is often associated with severe pain at the graft site. Additionally, in view of the recent US FDA alert concerning life-threatening complications of rhBMP (recombinant human bone morphogenetic protein) in cervical fusion, Mesoblast believes that its treatment may translate into a safe and effective clinical alternative.

The company initiated trials at Monash University in Australia to determine the safety and efficacy profile of its allogeneic stem cell therapy in cervical fusion. Twenty-four ewes underwent anterior removal of the cervical intervertebral disc at the C3/4 level, and were randomized to one of four treatment arms: autograft, bone graft substitute (Medtronic Mastergraft granules), allogeneic cells at doses of 5 or 10 million cells implanted in an FDA-approved interbody cage. The trial was completed at 3 months. No cell-related adverse events were noted at any time throughout the study. Groups receiving either dose of the company’s allogeneic cells had earlier and more robust fusion than the other groups. By CT scan at 3 months, 9/12 (75%) cell-treated animals had continuous interbody bony bridging compared with only 1/6 autograft and 2/6 with bone graft substitute (P = .019 and P = .043, respectively). Functional X-rays at 3 months showed that cell-treated subjects had significantly reduced flexion/extension at the C3/4 level compared with the other groups (P = .007), indicating significantly superior fusion outcomes.

In July 2008, the US FDA issued a public health notification of life-threatening complications associated with rhBMP in cervical spine fusion. According to the notification to healthcare practitioners, the agency has received at least 38 reports during the last 4 years of complications associated with swelling of neck and throat tissue, which resulted in compression of the airway and/or neurological structures in the neck. Most complications occurred between 2 and 14 days postoperatively with only a few events occurring prior to day 2. When airway complications occurred, medical intervention was frequently necessary. Treatments needed included respiratory support with intubation, anti-inflammatory medication, tracheotomy and most commonly second surgeries to drain the surgical site.

The safety and effectiveness of rhBMP in the cervical spine have not been demonstrated and these products are not approved by the US FDA for this use, therefore, the agency recommends that practitioners either use approved alternative treatments or consider enrolling as investigators in approved clinical studies. The agency has approved the use of two rhBMPs for well-defined medical conditions in limited patient populations. rhBMP-2 (contained in InFuse Bone Graft) has received premarket approval for fusion of the lumbar spine in skeletally mature patients with degenerative disc disease at one level from L2-S1 and for healing of acute, open tibial shaft fractures stabilized with an intramuscular nail and treated within 14 days of initial injury. rhBMP-7 (referred to as OP-1 and contained in OP-1 Implant and OP-1 Putty) has received humanitarian device exemption approval as an alternative to autograft in recalcitrant long bone nonunions where use of autograft is unfeasible and alternative treatments have failed. It is also approved as an alternative to autograft in compromised patients requiring revision posterolateral (intertransverse) lumbar spinal fusion for whom autologous bone and bone marrow harvest are not feasible or are not expected to promote fusion.