Complete remission of experimental arthritis by joint targeting of glucocorticoids with long‐circulating liposomes

Abstract

Objective. To increase the therapeutic activity of glucocorticoids in experimental arthritis by encapsulation in long-circulating polyethylene glycol liposomes, which have shown the ability to preferentially accumulate in inflamed joints after intravenous administration.Methods. Rats with adjuvant-induced arthritis (AIA) were treated intravenously with liposomal and free prednisolone phosphate (PLP) a few days after the first signs of disease. The effect on paw inflammation scores during the weeks after treatment was evaluated. Liposome biodistribution and joint localization were investigated by labeling the preparation with radioactive 111 In-oxine. By studying PLP encapsulated in other types of liposomes, which show a distinctive tissue distribution pattern and reduced accumulation in inflamed joints, the importance of targeted delivery to inflamed joints for achieving an increased therapeutic effect was illustrated.Results. Liposomal PLP proved to be highly effective in the rat AIA model. A single injection of 10 mg/kg resulted in complete remission of the inflammatory response for almost a week. In contrast, the same dose of unencapsulated PLP did not reduce inflammation, and only a slight effect was observed after repeated daily injections. Evidence was found that preferential glucocorticoid delivery to the inflamed joint was the key factor explaining the observed strong therapeutic benefit obtained with the liposomal preparation, while other possible mechanisms, such as splenic accumulation or prolonged release of prednisolone in the circulation, were excluded.Conclusion. Targeted delivery using longcirculating liposomes is a promising, novel means to successfully intervene in arthritis with glucocorticoid therapy.

Targeting of angiogenic endothelial cells at sites of inflammation by dexamethasone phosphate–containing RGD peptide liposomes inhibits experimental arthritis

“…Levels of localization of all 3 types of liposomes in the inflamed skin were higher than those in normal skin. Control liposomes (RAD-PEG-L or PEG-L) most likely localized in the inflamed skin due to the enhanced permeability and retention effect, as demonstrated for longcirculating liposomes at sites of inflammation or infection (25,48). It has been reported that enhanced permeability and retention-mediated extravasation increases with increasing circulation time of the liposomes (31).…”

“…However, in previous studies the effects of free corticosteroids such as DEXP and prednisolone phosphate in relation to the efficacy of liposomal formulations have been carefully assessed in this arthritis model as well as in a murine collageninduced arthritis model. In all of these studies a single administration of free drug exerted minor or no efficacy in alleviating the inflammation, whereas liposomal formulations were efficacious (25)(26)(27).…”

“…Encapsulation of corticosteroids in liposomes has been proven to reduce their side effects and increase their half-life and accumulation in the inflamed joint, resulting in strongly enhanced efficacy in rat adjuvantinduced arthritis (AIA) compared with administration of free corticosteroid (25)(26)(27). To direct the antiinflammatory activity to VECs at the site of inflammation, we encapsulated water-soluble dexamethasone phosphate (DEXP) in long-circulating, polyethylene glycol-coated liposomes (28) to which a cyclic RGD peptide was covalently attached (RGD-PEG-L).…”

Targeting the inflamed synovium: The quest for specificity

“…The efficacy of MTXliposomes was reduced when PEG-liposomes were used, probably due to reduced uptake by macrophages within the synovium (24). More recently, Metselaar and colleagues demonstrated that liposomal prednisolone phosphate was significantly more efficacious than the same dose of the free drug in 2 murine arthritis models (25,26). They were able to show that the intravenously administered PEG-liposomes homed to the inflamed joints and that there was an associated reduction in cartilage damage.…”

“…This is the first time that specific targeting of liposomes has been shown to be effective in arthritis and represents an important step forward as well as raising some intriguing questions. Although free corticosteroid was not used as a control in these experiments, previous work has shown dramatic differences in efficacy of nontargeted liposomal steroid over the free drug, along with dramatic reductions in cartilage damage (25,26). There remains a significant minority of patients with RA in whom active disease persists despite treatment with multiple disease-modifying antirheumatic drugs and biologic therapies, and in some of these patients steroid treatment remains necessary despite obvious concerns about long-term side effects.…”