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Pharmacology · Other immunomodulating biologics

Abatacept !

A fusion protein that blocks the second signal T cells need to switch on. Used in rheumatoid and psoriatic arthritis and to prevent graft-versus-host disease.

Updated 2026-11-01

The figure shows human CTLA-4 bound to B7-1 (CD80); abatacept carries this same CTLA-4 binding domain, fused to an IgG1 Fc.

Target in 3D: CD80 and CD86 (B7-1 and B7-2) on antigen-presenting cells. PDB structure 1I8L (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Abatacept is the extracellular domain of human CTLA-4 joined to a modified Fc portion of IgG1. CTLA-4 binds CD80 and CD86 more strongly than CD28 does, so abatacept occupies them and the CD28 co-stimulatory signal is lost. Without this second signal, naive T cells do not fully activate, make less IL-2 and drive less synovial inflammation. It does not deplete T cells.

  1. CTLA-4-Ig binds CD80/CD86
  2. CD28 gets no co-stimulation
  3. T cells do not fully activate
  4. Less IL-2 and synovitis

Pharmacokinetics

Absorption
Intravenous infusion or subcutaneous injection
Metabolism
Broken down like other proteins

Indications

Adverse effects

Common

  • Headache, dizziness
  • Runny nose, nosebleed
  • Nausea, diarrhoea, stomach pain
  • Injection-site bruising, redness and itching

Contraindications

  • Hypersensitivity to abatacept
  • Active serious infection

Key interactions

TNF inhibitors and anakinra
More serious infections without added benefit; not combined.
Vaccines, especially live vaccines
Not given during treatment or for three months after without the team's review.

What is monitored

  • Latent tuberculosis test and hepatitis B history before starting
  • Signs of infection
  • Breathing in people with COPD

Administration and safety

  • The intravenous form is a powder reconstituted with sterile water and infused by staff; the subcutaneous form is a prefilled syringe or autoinjector.
  • The laboratory is told about abatacept before blood tests.

Nursing care

  • Before the first dose, confirm the latent tuberculosis test and ask about hepatitis B, COPD and recurrent infections.
  • Check that no TNF inhibitor or anakinra is being used.
  • Teach to report fever, cough, night sweats, burning on urination or a red, hot area of skin.
  • Review planned vaccines with the team.

Pregnancy and breastfeeding

Human data are limited; the treating team weighs benefits and risks.

Test yourself

Think of the answer, then tap the question to see it.

Which T-cell signal does abatacept block?

Signal 2, the co-stimulation from CD80/CD86 binding CD28.

Which natural inhibitory receptor is abatacept built from?

CTLA-4, whose extracellular domain is fused to an IgG1 Fc.

Which lung disease calls for caution with abatacept?

Chronic obstructive pulmonary disease, which can worsen.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Abatacept Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); DailyMed - ADALIMUMAB- adalimumab-adaz injection, solution (DailyMed (U.S. National Library of Medicine), 2025); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 39 (McGraw Hill, 2023); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.