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Abatacept effective, safe when administered subcutaneously

Reuters Health • The Doctor's Channel Daily Newscast

NEW Y ORK (Reuters Health) – For patients with rheumatoid arthritis, the selective T-cell co-stimulation modulator abatacept works just as well whether administered subcutaneously (SC) once a week or intravenously once a month, researchers report.

“SC abatacept will provide additional treatment options,” Dr. Mark C Genovese, at Stanford University in Palo Alto, California, and colleagues state in Arthritis & Rheumatism online May 25. The availability of a subcutaneous formulation would be of particular benefit to those wishing to self-administer their therapy, they note.

The current study was a double-blind double-dummy 6-month study directly comparing the efficacy and safety of SC with IV abatacept in 1457 RA patients with inadequate responses to methotrexate. The primary endpoint was non-inferiority of SC abatacept compared to IV abatacept, based on rates of 20% reduction or better in arthritis symptoms (ACR 20 response).

Participants in the study continued taking methotrexate and were randomized to receive abatacept by SC injections (125 mg weekly) or by IV infusions (approximately 10 mg/kg every 4 weeks). Patients randomized to SC abatacept also received an IV abatacept loading dose on Day 1, “to ensure that the trough serum concentration of abatacept required to achieve full receptor occupancy, and thus maximal T-cell inhibition, was achieved as quickly as possible,” the authors explain.

Rates of ACR20 achieved at 6 months were 76.0% in the SC abatacept group and 75.8% in the IV abatacept group, Dr. Genovese and colleagues report.

Furthermore, they found that the safety profile of SC abatacept was generally comparable to IV abatacept. Discontinuation rates due to serious adverse events – mainly infections – were 1.1% and 1.9% in the SC and IV groups, respectively.

Injection site reactions were reported in 2.6% and 2.5% of patients in the SC and IV arms, respectively. One patient in each group had an anaphylactic reaction on Day 1 of treatment, both of which resolved on Day 2.

Additionally, the potential for an increased immune response to SC administration did not materialize. Three (0.4%) and five (0.7%) patients tested seropositive for anti-abatacept antibodies in the SC and IV groups, respectively, Dr. Genovese and colleagues report.

“These data,” they conclude, “support the use of abatacept for SC administration, providing an additional and beneficial treatment option for patients with RA.”

The study was funded by Bristol-Myers Squibb. The company announced last December that the US Food and Drug Administration had accepted for review a supplemental Biologics License Application for the subcutaneous formulation of abatacept.

Subcutaneous abatacept versus intravenous abatacept: A phase IIIb non-inferiority study in patients with an inadequate response to methotrexate
Arth Rheum 2011