Phase 1b Evaluation of Abaloparatide Solid Microstructured Transdermal System (Abaloparatide-sMTS) in Postmenopausal Women with Low Bone Mineral Density.

BACKGROUND AND OBJECTIVE: Abaloparatide, an anabolic osteoporosis treatment administered by subcutaneous (SC) injection, increases bone mineral density (BMD) and reduces fracture risk in postmenopausal women with osteoporosis. The abaloparatide-solid Microstructured Transdermal System [abaloparatide-sMTS (Kindeva, St Paul, MN, USA)], which delivers abaloparatide intradermally, is in development to provide an alternative method for abaloparatide delivery. The objective of this study was to evaluate the ability of subjects to self-administer abaloparatide-sMTS, based on pharmacokinetic and pharmacodynamic markers. METHODS: In this single-arm, open-label, Phase 1b study, 22 healthy postmenopausal women aged 50-85 years with low BMD were trained to self-administer abaloparatide-sMTS 300 µg once daily to the thigh for 5 min for 29 days. The primary endpoint was systemic exposure to abaloparatide. Secondary endpoints included percent change from baseline in serum procollagen type I N-terminal propeptide (s-PINP), patient experience, and safety. RESULTS: All 22 subjects completed the study. At baseline, mean age was 65.2 years, mean total hip T-score was - 1.32, and mean lumbar spine T-score was - 1.98. On Day 1, the median time to reach maximum concentration (Tmax) for abaloparatide-sMTS was 0.33 h and geometric mean (CV %) maximum concentration (Cmax) and area under the concentration-time curve from time 0 to the time of the last quantifiable concentration (AUC0-t) were 447 (38.0) pg/mL and 678 (45.3) pg·h/mL, respectively; the pharmacokinetic profile was similar on Days 15 and 29. Median percentage change in s-PINP was 45.4% and 64.4% at Days 15 and 29, respectively. The most common adverse events (AEs) were application site erythema, pain, and swelling, which were mostly of mild or moderate severity. No AEs led to study drug withdrawal and no serious AEs were reported. The success rate for self-administration at first application was 99.7%, and subject acceptability was high (~ 4.5 on a 5-point Likert Scale). CONCLUSIONS: Subjects successfully self-administered abaloparatide-sMTS, which provided a consistent pharmacokinetic profile over 29 days and produced s-PINP increases from baseline similar to that observed in the pivotal trial with abaloparatide-SC. Observed patient experience along with the clinical data support continued clinical development of abaloparatide-sMTS. TRIAL REGISTRATION NUMBER: NCT04366726, Date of registration 04/29/2020, retrospectively registered.

Osteoporosis is a serious health condition that causes more than 2 million fractures in the USA annually. Treatment options for osteoporosis include drugs that prevent bone resorption and anabolic agents that build new bone. Bone anabolic agents, such as abaloparatide, have been shown to increase bone mineral density and reduce the risk of fracture in postmenopausal women with osteoporosis. Currently, all bone anabolic agents are delivered by subcutaneous injection. However, some patients do not like injectable treatments, which can negatively impact patients' adherence to prescribed medication. In this study, we describe a novel mode of administration, the abaloparatide-solid Microstructured Transdermal System (abaloparatide-sMTS), which is applied to the thigh for 5 min and delivers abaloparatide intradermally. The study showed that this new method delivered abaloparatide into the blood as effectively as subcutaneous injections and demonstrated signs of activity in the body. Study participants were satisfied with abaloparatide-sMTS and found it easy to use. The most common side effects were skin related, including redness, pain, and swelling, which resolved shortly after dosing.

Controlled release of fibrin matrix-conjugated platelet derived growth factor improves ischemic tissue regeneration by functional angiogenesis.

Sustained, local, low dose growth factor stimulus of target tissues/cells is believed to be of imminent importance in tissue regeneration and engineering. Recently, a technology was developed to bind growth factors to a fibrin matrix using the transglutaminase (TG) activity of factor XIIIa, thus allowing prolonged release through enzymatic cleavage. In this study we aimed to determine whether TG-PDGF.AB in fibrin could improve tissue regeneration in a standard ischemic flap model. In vitro determination of binding and release kinetics of TG-PDGF.AB allowed proof of concept of the developed binding technology. A single spray application of TG-PDGF.AB in fibrin matrix at a concentration of 10 and 100ng/ml significantly reduced ischemia-induced flap tissue necrosis in vivo on day 7 after ischemic impact compared to controls. TG-PDGF.AB at a concentration of 100ng/ml fibrin induced distinct angiogenesis as reflected by significantly improved tissue perfusion assessed by laser Doppler imaging as well as enhanced von Willebrand factor (vWF) protein expression determined by immunohistochemical means. In addition, significantly more mature microvessels were observed with 100ng/ml TG-PDGF.AB in fibrin compared to control and vehicle groups as evidenced by an improved smooth muscle actin (sma)/vWF protein ratio. In conclusion, PDGF.AB in a conjugated fibrin matrix effectively reduced ischemia-induced tissue necrosis, increased tissue perfusion and induced the growth of a mature and functional neovasculature. The sealing properties of the fibrin matrix in conjunction with the prolonged growth factor stimulus enabled by the TG-hook binding technology may present an innovative and suitable tool in tissue regeneration. STATEMENT OF SIGNIFICANCE: In our experimental study we elucidated recombinant platelet derived growth factor (PDGF) as a potential candidate in inducing angiogenesis. To avoid preterm growth factor degradation in vivo PDGF.AB was covalently linked to a fibrin scaffold using a bi-domain functionalized peptide (FXIII substrate site and plasmin cleavage site). This allowed PDGF binding to fibrin during spray application to the donor site and subsequent prolonged release via endogenous plasmin. This resulted in a mature vascular network thus enhancing tissue perfusion and consequently improved clinical outcome. With our present work we could certainly provide researchers and clinicians with an innovative versatile and reproducible technology not only to induce functional vascularity but also to improve attempts in tissue engineering in general by e.g. using different growth factors. Hence, we believe that this approach studied in the present work may provide a valuable input in an effort to drive the aim forward bringing experimental work in tissue engineering to clinic by using a clinically well characterized and used fibrin scaffold in combination with a human recombinant growth factor (fibrin scaffold linked with the specific binding technology).

Fibrin biomatrix-conjugated platelet-derived growth factor AB accelerates wound healing in severe thermal injury.

Controlled delivery of growth factors from biodegradable biomatrices could accelerate and improve impaired wound healing. The study aim was to determine whether platelet-derived growth factor AB (PDGF.AB) with a transglutaminase (TG) crosslinking substrate site released from a fibrin biomatrix improves wound healing in severe thermal injury. The binding and release kinetics of TG-PDGF.AB were determined in vitro. Third-degree contact burns (dorsum of Yorkshire pigs) underwent epifascial necrosectomy 24 h post-burn. Wound sites were covered with autologous meshed (3:1) split-thickness skin autografts and either secured with staples or attached with sprayed fibrin sealant (FS; n = 8/group). TG-PDGF.AB binds to the fibrin biomatrix using the TG activity of factor XIIIa, and is subsequently released through enzymatic cleavage. Three doses of TG-PDGF.AB in FS (100 ng, 1 µg and 11 µg/ml FS) were tested. TG-PDGF.AB was bound to the fibrin biomatrix as evidenced by western blot analysis and subsequently released by enzymatic cleavage. A significantly accelerated and improved wound healing was achieved using sprayed FS containing TG-PDGF.AB compared to staples alone. Low concentrations (100 ng-1 µg TG-PDGF.AB/ml final FS clot) demonstrated to be sufficient to attain a nearly complete closure of mesh interstices 14 days after grafting. TG-PDGF.AB incorporated in FS via a specific binding technology was shown to be effective in grafted third-degree burn wounds. The adhesive properties of the fibrin matrix in conjunction with the prolonged growth factor stimulus enabled by this binding technology could be favourable in many pathological situations associated with wound-healing disturbances. Copyright © 2013 John Wiley & Sons, Ltd.

Mechanical stability in a human radius fracture treated with a novel tissue-engineered bone substitute: a non-invasive, longitudinal assessment using high-resolution pQCT in combination with finite element analysis.

The clinical gold standard in orthopaedics for treating fractures with large bone defects is still the use of autologous, cancellous bone autografts. While this material provides a strong healing response, the use of autografts is often associated with additional morbidity. Therefore, there is a demand for off-the-shelf biomaterials that perform similar to autografts. Biomechanical assessment of such a biomaterial in vivo has so far been limited. Recently, the development of high-resolution peripheral quantitative computed tomography (HR-pQCT) has made it possible to measure bone structure in humans in great detail. Finite element analysis (FEA) has been used to accurately estimate bone mechanical function from three-dimensional CT images. The aim of this study was therefore to determine the feasibility of these two methods in combination, to quantify bone healing in a clinical case with a fracture at the distal radius which was treated with a new bone graft substitute. Validation was sought through a conceptional ovine model. The bones were scanned using HR-pQCT and subsequently biomechanically tested. FEA-derived stiffness was validated relative to the experimental data. The developed processing methods were then adapted and applied to in vivo follow-up data of the patient. Our analyses indicated an 18% increase of bone stiffness within 2 months. To our knowledge, this was the first time that microstructural finite element analyses have been performed on bone-implant constructs in a clinical setting. From this clinical case study, we conclude that HR-pQCT-based micro-finite element analyses show high potential to quantify bone healing in patients.

Reduction in postlaminectomy epidural adhesions in sheep using a fibrin sealant-based medicated adhesion barrier.

Epidural adhesion formation is believed to be a central governing factor in the prevalence of pain after spinal surgery and is regarded as being the primary instigator of neural tethering, leading to complications during revision surgery. In this study, we assess the effectiveness and safety of fibrin sealant supplemented with tributyrin, termed Medicated Adhesion Barrier (MAB), as an alternative means of reducing the incidence of posterior spinal epidural adhesion formation. Laminectomy defects in sheep were treated with MAB, fibrin sealant alone, ADCONGel, or remained untreated. At 12 weeks postoperatively, the extent of fibrosis and epidural adhesion formation was evaluated using magnetic resonance imaging (MRI), peel-off testing, and histological examination. Initial invitro analysis revealed that tributyrin was retained in fibrin gel in a time-dependent manner and was an effective inhibitor of fibroblast proliferation. Treatment of sheep with MAB significantly reduced both the prevalence (p < 0.05) and tenacity (p < 0.05) of epidural adhesions. The effectiveness of MAB in preventing epidural adhesions was found to be comparable with that of ADCONGel. No adverse events were reported after the use of MAB. The MAB preparation seems to be an effective resorbable barrier for the prevention of epidural adhesions.

Bone healing induced by local delivery of an engineered parathyroid hormone prodrug.

Regenerative medicine requires innovative therapeutic designs to accommodate high morphogen concentrations in local depots, provide their sustained presence, and enhance cellular invasion and directed differentiation. Here we present an example for inducing local bone regeneration with a matrix-bound engineered active fragment of human parathyroid hormone (PTH(1-34)), linked to a transglutaminase substrate for binding to fibrin as a delivery and cell-invasion matrix with an intervening plasmin-sensitive link (TGplPTH(1-34)). The precursor form displays very little activity and signaling to osteoblasts, whereas the plasmin cleavage product, as it would be induced under the enzymatic influence of cells remodeling the matrix, was highly active. In vivo animal bone-defect experiments showed dose-dependent bone formation using the PTH-fibrin matrix, with evidence of both osteoconductive and osteoinductive bone-healing mechanisms. Results showed that this PTH-derivatized matrix may have potential utility in humans as a replacement for bone grafts or to repair bone defects.

A novel, tissue occlusive poly(ethylene glycol) hydrogel material.

The use of guided bone regeneration (GBR) techniques requires new materials meeting the needs of clinical application. Design criteria for GBR devices are biocompatibility, tissue occlusion, space provision, and clinical manageability. This study evaluates a novel biodegradable poly (ethylene glycol) (PEG) based material as tissue occlusive membrane. A subcutaneous implant model in rats was developed to test the barrier function of the PEG hydrogels over time. Fourteen rats received three membrane implants and two positive controls each. Explants were collected over a period of 7 months. Histological analysis revealed that for at least 4 months cellular infiltration in the membrane explants was lower than 1% of that of the positive controls. Therefore, the PEG based hydrogel can be regarded as tissue occlusive during this period of time. A barrier function seems to be maintained for up to 6 months. In vitro degradation studies performed with the same PEG constructs confirm the in vivo result. In conclusion, our results indicate that this novel PEG-based material has potential for use as a GBR barrier membrane.

Enhanced endothelial cell retention on shear-stressed synthetic vascular grafts precoated with RGD-cross-linked fibrin.

Clinical in vitro endothelialization has been shown to increase the patency of synthetic vascular grafts. The shear stress resistance of the cultured autologous endothelium represents a crucial cornerstone of the concept. We investigated whether an enrichment of the precoating matrix with adhesion sites can augment endothelial cell attachment. Adult human saphenous vein endothelial cells (AHSVECs) were seeded confluently ([58 +/- 11] x 10(3) AHSVECs/cm2) onto 10-cm-long ePTFE (expanded polytetrafluorethylene) vascular grafts (n = 24) precoated with commercial clinically approved fibrin gel (Tisseal) containing various concentrations of cross-linked RGD peptide (0.0, 4.0, 8.0, or 16.0 mg of RGD per milliliter of Tisseal fibrinogen component). Endothelialized grafts were postcultivated for 9 days before they were exposed to a pulsatile circulation model mimicking peak physiological shear stress conditions of the femoral artery (12 dyn/cm2; min/max, -60/+28 dyn/cm2). Cell loss after 24 h was quantitatively determined by image analysis of vital stains. Initial 24-h cell loss was 27.2 +/- 1.7% in grafts precoated with the non-RGD-enriched fibrin matrix. In contrast, cell loss was significantly less on fibrin containing 4.0 mg of RGD peptide per milliliter of Tisseal fibrinogen component (13.3 +/- 7.9%; p < 0.05). Cell loss on fibrin containing 8 and 16 mg of RGD per milliliter of Tisseal fibrinogen component was 41.0 +/- 27.4 and 43.0 +/- 23.2% (p > 0.05), respectively. We conclude that low concentrations of RGD peptide cross-linked into commercial fibrin matrices used for clinical in vitro lining of vascular grafts led to significantly increased endothelial cell retention. The failure of higher RGD concentrations to enhance endothelial cell attachment may be explained by competitive binding of endothelial cells to non-cross-linked RGD.

Bone repair with a form of BMP-2 engineered for incorporation into fibrin cell ingrowth matrices.

Most growth factors naturally involved in development and regeneration demonstrate strong binding to the extracellular matrix and are retained there until being locally mobilized by cells. In spite of this feedback between cell activity and growth factor mobilization in the extracellular matrix, this approach has not been extensively explored in therapeutic situations. We present an engineered bone morphogenetic protein-2 (BMP-2) fusion protein that mimics such function in a surgically relevant matrix, fibrin, incorporated into the matrix until it is locally liberated by cell surface-associated proteases. A tripartite fusion protein, denoted TG-pl-BMP-2, was designed and produced recombinantly. An N-terminal transglutaminase substrate (TG) domain provides covalent attachment to fibrin during coagulation under the influence of the blood transglutaminase factor XIIIa. A central plasmin substrate (pl) domain provides a cleavage site for local release of the attached growth factor from the fibrin matrix under the influence of cell-activated plasmin. A C-terminal human BMP-2 domain provides osteogenic activity. TG-pl-BMP-2 in fibrin was evaluated in vivo in critical-size craniotomy defects in rats, where it induced 76% more defect healing with bone at 3 weeks with a dose of 1 mug/defect than wildtype BMP-2 in fibrin. After a dosing study in rabbits, the engineered growth factor in fibrin was evaluated in a prospective clinical study for pancarpal fusion in dogs, where it induced statistically faster and more extensive bone bridging than equivalent treatment with cancellous bone autograft. The strong healing response shown by fibrin including a bound BMP-2 variant suggests that with the combination of bound growth factor and ingrowth matrix, it may be possible to improve upon the natural growth factor and even upon tissue autograft.

Bone healing in the rat and dog with nonglycosylated BMP-2 demonstrating low solubility in fibrin matrices.

A novel form of recombinant human bone morphogenetic protein-2 (BMP-2) was explored for effective incorporation and long-term retention into fibrin ingrowth matrices. The solubility of native BMP-2 is greatly dependent on its glycosylation. To enhance retention of BMP-2 in fibrin matrices, a nonglycosylated form (nglBMP-2), which is less soluble than the native glycosylated protein, was produced recombinantly and evaluated in critical-size defects in the rat calvarium (group n=6). When 1 or 20 microg nglBMP-2 was incorporated by precipitation within the matrix, 74 +/- 4% and 98 +/- 2% healing was observed in the rat calvarium, respectively, as judged radiographically by closure of the defect at 3 weeks. More soluble forms of BMP-2, used as controls, induced less healing, demonstrating a positive correlation between low solubility, retention in vitro, and healing in vivo. Subsequently, the utility of nglBMP-2 was explored in a prospective veterinary clinical trial for inter-carpal fusion in dogs, replacing the standard-of-care, namely autologous cancellous autograft, with nglBMP-2 in fibrin. In a study of 10 sequential canine patients, fibrin with 600 microg/ml nglBMP-2 performed better than autograft in the first weeks of bone healing and comparably thereafter. Furthermore, a greater fraction of animals treated with nglBMP-2 in fibrin demonstrated bone bridging across each of the treated joints at both 12 and 17 weeks than in animals treated with autograft. These results suggest that evaluation in a human clinical setting of nonglycosylated BMP-2 in fibrin matrices might be fruitful.

Treatment of nonunions with nonglycosylated recombinant human bone morphogenetic protein-2 delivered from a fibrin matrix.

OBJECTIVE: To report the results of the treatment of nonunions with nonglycosylated recombinant human bone morphogenetic protein-2 (nglBMP-2) delivered from a designed fibrin matrix. STUDY DESIGN: Experimental trial in rodents and prospective clinical study in dogs and cats with nonunion fractures. ANIMALS: Twenty adult female, albino, Sprague-Dawley rats; 8 client-owned cats and dogs. METHODS: After development of a fibrin matrix and evaluation of nglBMP-2 in a rodent femoral defect model, 8 consecutive long bone nonunion fractures (no progression in healing in > or = 3 months), were treated using 300 microg nglBMP-2 in a liquid fibrin precursor, injected into the defect gap after fracture revision and stabilization, or through a stab incision into the fracture site. The fibrin matrix was designed to clot in the wound after 60 seconds and to release the nglBMP-2 continuously over several days. RESULTS: Using only fibrin gel, 7% of the rat femoral defect was filled with new formed bone compared with 79% defect filling using 2 microg nglBMP-2 (P=.006). Five and 10 microg nglBMP in fibrin resulted in union of all femoral defects with complete filling of the gap with new bone. Bony bridging and clinical healing was achieved in 7 patients within 24 weeks of administration of nglBMP-2. CONCLUSIONS: Application of nglBMP-2 in a functional matrix can induce bone healing. Controlled release of nglBMP-2 from a fibrin matrix mimics the natural fracture hematoma. CLINICAL RELEVANCE: nglBMP-2/fibrin can successfully replace a cancellous bone autograft in fracture treatment with an associated reduction in graft donor site morbidity and surgical time.

Repair of bone defects using synthetic mimetics of collagenous extracellular matrices.

We have engineered synthetic poly(ethylene glycol) (PEG)-based hydrogels as cell-ingrowth matrices for in situ bone regeneration. These networks contain a combination of pendant oligopeptide ligands for cell adhesion (RGDSP) and substrates for matrix metalloproteinase (MMP) as linkers between PEG chains. Primary human fibroblasts were shown to migrate within these matrices by integrin- and MMP-dependent mechanisms. Gels used to deliver recombinant human bone morphogenetic protein-2 (rhBMP-2) to the site of critical- sized defects in rat crania were completely infiltrated by cells and were remodeled into bony tissue within five weeks. Bone regeneration was dependent on the proteolytic sensitivity of the matrices and their architecture. The cell-mediated proteolytic invasiveness of the gels and entrapment of rhBMP-2 resulted in efficient and highly localized bone regeneration.