Biological Agents

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Introduction

Biological agents, or biologics, are a class of medications derived from living organisms or their products. They are engineered to target specific components of the immune system, making them effective in treating various autoimmune and inflammatory diseases. Their precision in targeting specific molecules has transformed the management of chronic conditions, especially in cases where traditional therapies have proven ineffective.

Mechanism of Action

• Biologics typically target specific cytokines or immune cells involved in inflammation and immune response. Examples include tumour necrosis factor (TNF) inhibitors, interleukin (IL) blockers, and B-cell or T-cell modulators.
• By blocking these cytokines or immune cells, biologics reduce inflammation and suppress abnormal immune activity, leading to symptom relief and disease progression control.
• They offer a more targeted approach compared to traditional immunosuppressive drugs, which often have broader effects on the immune system.

Uses of Biological Agents

• Rheumatoid Arthritis (RA): Biologics such as TNF inhibitors (e.g., adalimumab, etanercept) and IL-6 inhibitors (e.g., tocilizumab) are widely used in RA to reduce joint inflammation and prevent damage.
• Inflammatory Bowel Disease (IBD): Biologics, including TNF inhibitors and integrin inhibitors (e.g., vedolizumab), are effective in managing Crohn's disease and ulcerative colitis by reducing intestinal inflammation.
• Psoriasis and Psoriatic Arthritis: IL-17 and IL-23 inhibitors (e.g., secukinumab, ustekinumab) target specific inflammatory pathways in psoriasis, providing relief from skin and joint symptoms.
• Ankylosing Spondylitis: Biologics, particularly TNF inhibitors, are used to reduce spinal inflammation and improve mobility in this chronic arthritis condition.
• Multiple Sclerosis (MS): B-cell targeting biologics, such as ocrelizumab, are used to slow disease progression and reduce relapse rates in MS.
• Systemic Lupus Erythematosus (SLE): Belimumab, a biologic targeting B-cells, has shown effectiveness in managing SLE by reducing autoantibody production.

Classifications of Biological Agents

• Tumor Necrosis Factor (TNF) Inhibitors: These block TNF, a cytokine involved in systemic inflammation. Examples include adalimumab, infliximab, and etanercept.
• Interleukin (IL) Inhibitors: These target specific interleukins involved in immune responses, such as IL-6 (e.g., tocilizumab), IL-12/23 (e.g., ustekinumab), and IL-17 (e.g., secukinumab).
• B-cell Modulators: These target B-cells, a type of immune cell involved in antibody production. Examples include rituximab (targets CD20) and belimumab (targets B-lymphocyte stimulator protein).
• T-cell Modulators: These agents interfere with T-cell activation. An example is abatacept, which is used in rheumatoid arthritis.
• Integrin Inhibitors: These target integrins, proteins that play a role in cell adhesion, and are used in inflammatory bowel disease (e.g., vedolizumab).

Side Effects

• Increased Infection Risk: Biologics suppress parts of the immune system, making patients more susceptible to infections, especially respiratory and opportunistic infections (e.g., tuberculosis).
• Injection Site Reactions: Common with subcutaneous biologics, causing redness, itching, and pain at the injection site.
• Infusion Reactions: Biologics administered intravenously may cause infusion-related reactions, including fever, chills, and low blood pressure.
• Malignancies: Long-term use of biologics, particularly TNF inhibitors, may increase the risk of certain cancers, including lymphoma.
• Autoimmune Reactions: In rare cases, biologics may induce autoimmune conditions like lupus-like syndrome.
• Liver Toxicity: Some biologics may cause elevated liver enzymes, requiring periodic liver function monitoring.

Monitoring and Precautions

• Infection Screening: Before starting biologics, patients should be screened for latent infections, particularly tuberculosis and hepatitis B.
• Regular Blood Tests: Monitoring blood counts, liver function, and kidney function is essential, as biologics can affect these organs.
• Vaccinations: Live vaccines are generally avoided during biologic therapy due to the risk of infection. Patients may receive non-live vaccines before treatment initiation.
• Monitoring for Malignancies: Patients should be monitored for signs of malignancy, especially if there is a personal or family history of cancer.

Common Biological Agents: Uses and Side Effects