Comparison of the effect of intra-tendon applications of recombinant human platelet-derived growth factor-BB, platelet-rich plasma, steroids in a rat achilles tendon collagenase model.

This study compared the effect of intra-tendon (IT) delivery of recombinant human platelet-derived growth factor-BB (rhPDGF-BB), platelet-rich plasma (PRP) and corticosteroids in a rat tendinopathy model. Seven days after collagenase induction of tendinopathy, a 30-µl IT injection was administered. Treatments included: saline; 3 µg rhPDGF-BB; 10 µg rhPDGF-BB; PRP; and 300 µg triamcinolone acetonide (TCA). Outcomes were assessed 7 and 21 days after treatment. All groups exhibited good to excellent repair. Relative to saline, cell proliferation increased 65% in the 10 µg rhPDGF-BB group and decreased 74% in the TCA group; inflammation decreased 65% in the TCA group. At 7 days, maximum load-to-failure was increased in the 3 µg rhPDGF-BB group relative to saline, PRP, and TCA (p < 0.025). On day 21, maximum load-to-rupture was increased in the 10 µg rhPDGF-BB group relative to saline, PRP, and TCA (p < 0.035) and in the 3 µg rhPDGF-BB group compared to saline and TCA (p < 0.027). Stiffness in the 10 µg rhPDGF-BB group was increased compared to saline, PRP, and TCA (p < 0.038). Histology demonstrated similar repair in all groups. PRP and TCA did not improve mechanical properties compared to saline. Injections of rhPDGF-BB increased maximum load-to-failure (3 and 10 µg) and stiffness (10 µg) relative to controls and commonly used treatments. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:145-150, 2014.

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.

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.

Safety of recombinant human platelet-derived growth factor-BB in Augment(®) Bone Graft.

This article discusses nonclinical and clinical data regarding the safety of recombinant human platelet-derived growth factor-BB as a component of the Augment(®) Bone Graft (Augment). Augment is a bone graft substitute intended to be used as an alternative to autologous bone graft in the fusion of hindfoot and ankle joints. Nonclinical studies included assessment of the pharmacokinetic profile of intravenously administered recombinant human platelet-derived growth factor-BB in rat and dog, effects of intravenous administration of recombinant human platelet-derived growth factor-BB in a reproductive and development toxicity study in rats, and chronic toxicity and carcinogenicity of Augment in a 12-month implantation model. These studies showed that systemic exposure was brief and clearance was rapid. No signs of toxicity, carcinogenicity, or tumor promotion were observed even with doses far exceeding the maximum clinical dose. Results of clinical trials (605 participants) and commercial use of recombinant human platelet-derived growth factor-BB containing products indicate that these products are not associated with increased incidence of adverse events or cancer. The safety data presented provide evidence that recombinant human platelet-derived growth factor-BB is a safe therapeutic when used in combination products as a single administration during surgical procedures for bone repair and fusion. There is no evidence associating use of recombinant human platelet-derived growth factor-BB in Augment with chronic toxicity, carcinogenicity, or tumor promotion.

Augment bone graft products compare favorably with autologous bone graft in an ovine model of lumbar interbody spine fusion.

STUDY DESIGN: This study was designed to determine whether Augment Bone Graft (Augment, Biomimetic Therapeutics, Inc., Franklin, TN) and Augment Injectable Bone Graft (Augment Injectable, Biomimetic Therapeutics, Inc., Franklin, TN), 2 combination devices comprising recombinant human platelet-derived growth factor-BB and ß-tricalcium phosphate-containing matrices, promote bone bridging in an ovine model of lumbar spine fusion. Autologous bone graft (autograft) was used as a positive control. OBJECTIVE: The purpose of this study was to determine the ability of Augment products to promote fusion of the L2-L3 and L4-L5 vertebral bodies in an ovine model. SUMMARY OF BACKGROUND DATA: In interbody spine fusion, the intervertebral disc is removed and a spacer is inserted for support and to facilitate bone growth. The fusion is commonly enhanced with grafts. Autograft is the "gold standard" but it has limitations including availability and donor-site morbidity. Synthetic graft substitutes eliminate these complications. Augment products are combination devices including recombinant human platelet-derived growth factor-BB, a well-characterized chemotactic, mitogenic, and proangiogenic protein essential in wound and bone healing. METHODS: Twenty-two sheep received an uninstrumented, double-level, interbody lumbar spinal fusion procedure using a polyetheretherketone spacer, which was either empty or packed with iliac crest autograft, Augment or Augment Injectable. The same treatment was used at both levels. Animals were 24 weeks after surgery, and fusion was assessed by micro-computed tomography (micro-CT) and histology. RESULTS: Micro-CT and histologic assessment of fusion revealed that empty controls had significantly lower fusion rates. No differences were detected among autografts, Augment, and Augment Injectable-treated specimens. Residual ß-tricalcium phosphate particles embedded in the newly formed bone were visible in Augment- and Augment Injectable-treated specimens. CONCLUSION: Augment-treated specimens had the highest fusion scores. Treatment with either of the Augment products significantly promoted interbody spine fusion compared with empty spacers and was equivalent to autograft-induced fusion. No adverse events were noted.