Polymer particles for the intra-articular delivery of drugs to treat osteoarthritis.

Osteoarthritis (OA) is a leading cause of chronic disability. It is a progressive disease, involving pathological changes to the entire joint, resulting in joint pain, stiffness, swelling, and loss of mobility. There is currently no disease-modifying pharmaceutical treatment for OA, and the treatments that do exist suffer from significant side effects. An increasing understanding of the molecular pathways involved in OA is leading to many potential drug targets. However, both current and new therapies can benefit from a targeted approach that delivers drugs selectively to joints at therapeutic concentrations, while limiting systemic exposure to the drugs. Delivery systems including hydrogels, liposomes, and various types of particles have been explored for intra-articular drug delivery. This review will describe progress over the past several years in the development of polymer-based particles for OA treatment, as well as theirin vitro, in vivo, and clinical evaluation. Systems based on biopolymers such as polysaccharides and polypeptides, as well as synthetic polyesters, poly(ester amide)s, thermoresponsive polymers, poly(vinyl alcohol), amphiphilic polymers, and dendrimers will be described. We will discuss the role of particle size, biodegradability, and mechanical properties in the behavior of the particles in the joint, and the challenges to be addressed in future research.

GSK3787-Loaded Poly(Ester Amide) Particles for Intra-Articular Drug Delivery.

Osteoarthritis (OA) is a debilitating joint disorder affecting more than 240 million people. There is no disease modifying therapeutic, and drugs that are used to alleviate OA symptoms result in side effects. Recent research indicates that inhibition of peroxisome proliferator-activated receptor δ (PPARδ) in cartilage may attenuate the development or progression of OA. PPARδ antagonists such as GSK3787 exist, but would benefit from delivery to joints to avoid side effects. Described here is the loading of GSK3787 into poly(ester amide) (PEA) particles. The particles contained 8 wt.% drug and had mean diameters of about 600 nm. Differential scanning calorimetry indicated the drug was in crystalline domains in the particles. Atomic force microscopy was used to measure the Young's moduli of individual particles as 2.8 MPa. In vitro drug release studies showed 11% GSK3787 was released over 30 days. Studies in immature murine articular cartilage (IMAC) cells indicated low toxicity from the drug, empty particles, and drug-loaded particles and that the particles were not taken up by the cells. Ex vivo studies on murine joints showed that the particles could be injected into the joint space and resided there for at least 7 days. Overall, these results indicate that GSK3787-loaded PEA particles warrant further investigation as a delivery system for potential OA therapy.

Poly(ester amide) particles for controlled delivery of celecoxib.

Many potential pharmacological treatments for osteoarthritis can result in undesirable side effects due to the systemic administration of drugs, making the direct delivery of drugs to joints an attractive alternative. Poly(ester amide)s (PEAs) have been shown to exhibit promising properties for the development of particle-based intra-articular delivery vehicles. However, a limited range of PEA structures has been investigated. In this study, we prepared and characterized the properties of two different PEA particles composed of l-phenylalanine, sebacic acid, and either 1,4-butanediol or 1,8-octanediol (PBSe and POSe, respectively). The anti-inflammatory drug celecoxib (CXB) was encapsulated into the particles. Despite minor structural differences, PBSe and POSe exhibited different thermal and mechanical properties, and encapsulation of CXB influenced these properties. PBSe-CXB particles provided a slower release of drug in vitro relative to POSe-CXB. Toxicity studies showed that particles without drug exhibited low toxicity to ATDC5 and C2C12 cells, while the PBSe-CXB particles exhibited concentration-dependent toxicity. Host response to the particles was evaluated in an ovine model. No adverse effects were observed following intra-articular injection and it was observed that the particles diffused into the surrounding tissues. This work shows the importance of structural tuning in PEA delivery vehicles and demonstrates their potential for further development. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1235-1243, 2019.

Thermoresponsive and Covalently Cross-Linkable Hydrogels for Intra-Articular Drug Delivery.

The local delivery of drugs to joints is a recognized strategy in the treatment of osteoarthritis. Hydrogels, particularly those that can be injected as liquids but undergo gelation in the joint, are promising platforms for intra-articular drug delivery. However, their properties must be carefully designed and tuned to achieve sustained drug release, which has been a challenge with previous hydrogels. We describe here the use of a combination of noncovalent thermal gelation and covalent cross-linking with poly(caprolactone-co-lactide)(PCLA)-poly(ethylene glycol)(PEG)-PCLA triblock copolymers to achieve hydrogels with sustained drug release in joints. The hybrid cross-linking approach afforded higher viscoelastic and compression moduli compared to noncovalent cross-linking alone and enabled celecoxib as well as other drugs to be loaded without substantially compromising the mechanical properties. Celecoxib release in vitro was much slower for the hybrid cross-linked hydrogel, with only 20% released over 22 days, compared to 90% released over 22 days for a noncovalently cross-linked hydrogel. Furthermore, the burst release of celecoxib was reduced in vivo in horse joints compared to noncovalent systems, and the drug was detected in synovial fluid for a period of two months. Overall, this new hydrogel system shows significant promise as a platform for further development in intra-articular delivery.