Biologic agents in rheumatoid arthritis

Pathogenetic rationale for use

In rheumatoid arthritis, synovial macrophages play a key role in joint destruction. They excessively secrete pro-inflammatory cytokines—interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-α). These substances trigger an aggressive cascade of reactions in tissues:

• Drastically stimulate the synthesis of the enzyme collagenase, which directly cleaves and destroys joint structures.
• Significantly increase bone resorption, weakening the bone.
• Inhibit cartilage proteoglycan synthesis, depriving it of the ability to regenerate.

Genetically engineered biological agents are designed to interrupt this pathological process. They act in a targeted manner: either binding the cytokines themselves or blocking their cellular receptors.

Interleukin-1 (IL-1) blockers

In educational literature, the term "receptor antagonist" is most commonly applied to anakinra. This is a genetically engineered biological drug that is a recombinant cytokine receptor antagonist.

• Mechanism of action: anakinra competitively binds to IL-1 receptors. By occupying the interleukin binding sites on the cell surface, the drug reliably blocks its action, thereby suppressing inflammation and halting cartilage destruction.
• Indications and regimen: the agent is prescribed for severe forms of rheumatoid arthritis, including when other disease-modifying antirheumatic drugs have proven ineffective. It is administered subcutaneously once daily.
• Side effects: therapy carries a risk of neutropenia. Furthermore, due to profound interference with the immune response, there is a high risk of opportunistic infections and tuberculosis, which requires continuous medical monitoring.

Tumor necrosis factor (TNF-α) blockers

This group is represented by drugs that neutralize TNF-α, but do so through different mechanisms.

1. Etanercept is a genetically engineered recombinant human TNF-α receptor. It acts as a sort of "decoy protein": circulating in the blood, it binds free TNF-α and physically blocks its interaction with actual cell receptors. The drug is indicated for moderate to severe rheumatoid arthritis. It is administered subcutaneously twice a week. It can be used either as monotherapy or in combination with methotrexate. It features relatively low toxicity; local injection site reactions are the most common side effect.
2. Infliximab are chimeric (murine-human) monoclonal IgG antibodies against TNF-α. Unlike etanercept, infliximab binds directly to the cytokine, preventing it from attaching to the receptor. In rheumatoid arthritis, it is prescribed exclusively in combination with methotrexate. The drug is also used for psoriasis, ankylosing spondylitis (Bechterew's disease), and Crohn's disease. It is administered via intravenous infusion (the procedure takes about two hours) once every two weeks. Local reactions (injection site inflammation) and severe hematological complications—pancytopenia (decreased neutrophil, leukocyte, and platelet counts)—are possible.

Risks of immunosuppressive therapy

Biological therapy for rheumatoid arthritis belongs to the class of immunosuppressive interventions. The main complication of such therapy is profound suppression of the immune response, leading to iatrogenic (medically induced) immunodeficiency.

This condition creates ideal conditions for the development of severe opportunistic infections. While taking cytokine antagonists, patients become extremely vulnerable to the reactivation of tuberculosis, severe systemic mycoses, and various viral infections. This is why prescribing genetically engineered biological agents requires thorough preliminary screening and continuous monitoring of blood counts throughout the entire course of treatment.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• The role of synovial macrophages in the pathogenesis of rheumatoid arthritis
• Mechanisms of pancytopenia development during anticytokine therapy
• Differential diagnosis of opportunistic infections in the setting of immunosuppression
• Special considerations for using methotrexate in combination with monoclonal antibodies

Other topics in the "Analgesics" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.