Rheumatoid arthritis (RA) is an autoimmune disease primarily affecting the joints. Inflammation and joint damage occur which leads to pain and swelling. RA usually affects small joints of the hands, feet and wrists. However, larger joints such as the hips and knees can also be affected.

Abatacept is a selective costimulation modulator and is the first drug in a new class of agents. The drug specifically binds to CD80 and CD86 receptors on antigen-presenting cells, preventing their interaction with CD28 receptors on T lymphocytes. This inhibits T cell proliferation and resulting B cell immunological responses. In combination with methotrexate, abatacept has been shown to reduce the signs and symptoms of RA.

Abatacept, in combination with methotrexate, is indicated for:

  • Treatment of moderate to severe active rheumatoid arthritis in adults with an inadequate response or intolerance to other disease modifying anti-rheumatic drugs (DMARDs), such as methotrexate or tumour necrosis factor (TNF) inhibitors;
  • Treatment of severe, active and progressive rheumatoid arthritis in adults not previously treated with methotrexate;
  • Reducing the signs and symptoms of moderately to severely active polyarticular juvenile idiopathic arthritis in paediatric patients six years of age and older who have had an inadequate response to one or more DMARDs. Abatacept may be used as monotherapy or in combination with methotrexate in these patients; and
  • Treatment of active psoriatic arthritis in adults with an inadequate response to previous DMARD therapy.

For adult patients with RA or psoriatic arthritis, abatacept may be administered as an intravenous (IV) infusion or a subcutaneous (SC) injection.

IV dosing regimen

Patients with RA or psoriatic arthritis should receive all IV doses of abatacept as a 30-minute infusion. Table 1 demonstrates the weight-based dosing regimen recommended in the product information.

Table 1. Recommended IV dosing for abatacept

Bodyweight of patient Dose Number of 250mg abatacept vials
<60 kg 500 mg 2
≥60-≤100 kg 750 mg 3
≥100 kg 1,000 mg 4

Paediatric patients weighing less than 75kg are dosed at 10mg/kg. Paediatric and adolescent patients weighing greater than 75kg are dosed using the adult dosing regimen up to a maximum of 1,000mg per dose.

Following the initial IV administration, repeat infusions should be given at two and four weeks after the first infusion and every four weeks thereafter.

SC dosing regimen

Abatacept may also be administered as a weekly SC injection. However, this is only recommended in adult patients due to a lack of clinical trial data in children. An IV loading dose may be considered for patients being treated for RA, although this is not necessary for patients being treated for psoriatic arthritis. SC doses do not need to be adjusted for weight. When switching from IV therapy to SC administration, the first SC dose should be administered instead of the next scheduled intravenous dose.

While patients may be trained to self-administer SC abatacept, the first dose should be administered under medical supervision. In addition to training in appropriate injection technique, patients should be advised of the importance of injection site rotation and avoiding areas of tender, bruised, red or hard skin.

Abatacept is an immunosuppressant and is contraindicated in patients with severe and uncontrolled infections such as sepsis and opportunistic infections. Placebo-controlled trials demonstrate a greater risk of infections including serious infections when abatacept therapy is combined with a TNF inhibitor. The combined use is, therefore, not recommended. Patients who are transitioning from a TNF-inhibitor to abatacept should be carefully monitored for signs of infection. Administration with other biological DMARDs such as rituximab and anakinra should also be avoided due to a lack of data. Abatacept may be associated with reactivation of inactive hepatitis B and latent tuberculosis; screening should occur prior to initiation. Patients may receive concurrent vaccinations except for live vaccines which should not be given with abatacept or within three months of its discontinuation.

References:

  1. Australian Government Department of Health. Rheumatoid Arthritis. Health Direct: 2017.
  2. Australian Government Department of Health and Ageing. Australian Public Assessment Report for Abatacept. Woden: Therapeutic Goods Administration; 2012.
  3. Orencia® (abatacept) Australian approved product information. Approved July 2018.

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