Effect of implantation of Augment(®) Bone Graft on serum concentrations of platelet-derived growth factors: a pharmacokinetic study.

BACKGROUND: Augment(®) Bone Graft is a bone graft substitute intended to be used as an alternative to autologous bone graft in the fusion of hindfoot and ankle joints. Augment(®) Bone Graft is a combination device comprised of beta-tricalcium phosphate (ß-TCP) and recombinant human platelet-derived growth factor BB homodimer (rhPDGF-BB). OBJECTIVE: This human pharmacokinetic study was undertaken to assess the effect of Augment(®) Bone Graft implantation on the serum concentration of platelet-derived growth factors (PDGFs). METHODS: Under the terms of a Research Ethics Board-approved protocol, Augment(®) Bone Graft was implanted in patients (n = 7) undergoing hindfoot and ankle arthrodesis procedures requiring graft material. The control cohort of the study (n = 4) received autologous bone graft. The serum concentrations of PDGF isoforms AA, AB and BB in blood samples, obtained prior to and at ten time points (up to 7 days) after surgery, were measured using enzyme-linked immunosorbent assays (ELISA). RESULTS: The serum concentration of PDGF-BB did not vary significantly from baseline (median of the combined cohorts 3.89 ng/mL) throughout the course of the study. The serum concentrations of PDGF-AA, PDGF-AB and total PDGF did not deviate from their baseline values (medians of the combined cohorts were 2.87, 14.95 and 20.19 ng/mL for PDGF-AA, PDGF-AB and total PDGF, respectively) except for the last time point in which they were increased (medians for the combined cohorts were 4.71, 20.42 and 30.29 ng/mL for PDGF-AA, PDGF-AB and total PDGF, respectively). There were no differences between the two treatment groups with regard to changes in the serum concentrations of PDGF. None of the samples tested contained anti-PDGF-BB antibodies. CONCLUSION: Analysis of the data demonstrated that the serum concentrations of all three PDGF isoforms analysed were unaffected by implantation of Augment(®) Bone Graft.

The role of recombinant human platelet-derived growth factor-BB (rhPDGF-BB) in orthopaedic bone repair and regeneration.

Recombinant human PDGF BB homodimer (rhPDGF-BB) is a potent recruiter of, and strong mitogenic factor for, cells crucial to musculoskeletal tissue repair, including mesenchymal stem cells (MSCs), osteogenic cells and tenocytes. rhPDGF-BB also upregulates angiogenesis. These properties allow rhPDGF-BB to trigger the cascade of bone and adjoining soft tissue repair and regeneration. This mechanism of action has been established in numerous preclinical and clinical studies. Demonstration of the safety and efficacy of rhPDGF-BB in the healing of chronic foot ulcers in diabetic patients and regeneration of alveolar (jaw) bone lost due to chronic infection from periodontal disease has resulted in two FDA-approved products based on this molecule. A third product is in late stages of clinical development, with pilot and pivotal clinical studies of rhPDGF-BB mixed with an osteoconductive bone matrix (Augment(®) Bone Graft) in foot and ankle fusions demonstrating that this product is at least as effective as bone autograft, and has an improved safety profile. Additional combinations of rhPDGF-BB with tissue-specific matrices are also being studied clinically in additional musculoskeletal indications.