Clinical Drug Experience Knowledgebase

PHASE 2 STUDY OF DEXAMETHASONE 21-PHOSPHATE LOADED INTO AUTOLOGOUS ERYTHROCYTES IN STEROID-DEPENDENT ULCERATIVE COLITIS PATIENTS

Medical treatment of patients with ulcerative colitis (UC) presents a constant challenge. Corticosteroids are effective in the majority of patients, but benefits are offset by adverse events. For steroid-dependent patients therapeutic choices are limited to azathioprine/6-mercaptopurine, methotrexate and infliximab; however, 25% of more patients do not respond, become intolerant, or have contraindications (e.g. history of neoplasia) to these drugs.

A novel method of corticosteroids delivery by loading dexamethasone 21-phosphate into red blood cells has been validated. Owing to their long life span in the circulation and the capability of their cellular membrane to be opened and resealed in appropriate conditions, erythrocytes are excellent drug carriers. An ideal drug to be encapsulated into erythrocytes is Dex 21-P, a biologically inactive compound which undergoes dephosphorylation by intra-erythrocyte enzymes releasing the active metabolite, dexamethasone, by simple passive diffusion through cell membranes. In a previous pilot study in a cohort of steroid-dependent patients with inactive inflammatory bowel disease, Dexamethasone 21-phosphate loaded into autologous erythrocytes allowed to complete withdrawal of systemic steroids, and the overall cumulative exposure to corticosteroids from Dex 21-P-encapsulated erythrocytes (about 5-10 mg per month) was far less than conventional corticosteroids, and this translated into a lower rate of steroid-related events.