Abatacept (CTLA4Ig) is a soluble fusion protein composed of the extracellular domain of human CTLA4 and a fragment of the Fc portion of human IgG1 (hinge and CH2 and 3 domains), functioning as a selective T-cell co-stimulation modulator and a protein drug for autoimmune diseases.

Abatacept reduces paw edema, with the SC multiple-dose group showing significantly greater reduction (tobs = 2.50) compared to the IV dose group. It exhibits linear PK across studied doses, with an NCA clearance (CL) of 20.8 mL/day/kg, volume (Vss) of 146 mL/kg, and bioavailability (F) of the SC dose at 57.7% [2]. Abatacept (oral; 10 mg/kg; every 2 days) also reduces the proportion of activated T cells (CD44highCD62L–) and inhibits the up-regulation of ICOS and CD71 in homozygous DO11.10 RAG-2–/–BALB/c (H-2d/d) mice [3].

Animal Model: Male Lewis rats (6-9 weeks old) with weights of 150-175 g. Dosage: 10 mg/kg (i.v.), 20 mg/kg (s.c. single-dose), 20 mg/kg (SC Multiple-dose) on day 21 with 10 mg/kg SC doses on days 23, 25, 27, and 29. Administration: i.v. or s.c. [2]