Abatacept is a

Abatacept is a fusion protein consisting of CTLA4 and the Fc poion of IgG1. It inhibits T cell activation by competitively inhibiting the costimulation of T cells that results from an interaction of T cell-expressed CD28 and CD80/86 expressed by antigen-presenting cells. It can be used with or without methotrexate, although its efficacy is greater as cotherapy with methotrexate. It has a positive effect on signs and symptoms of RA and also retards progressive bone damage.