Biologics: Treating Autoimmune Diseases

Abida Mozid, BSc Biomedical Science

Figure 1: Depiction of anitbodies (17)

Biologics are a group of medications derived from living organisms, such as yeast, bacteria or plant and animal cells. ⁽¹⁾

They have transformed how many autoimmune diseases are treated.

Most biologics are intended to target pathways of the immune system implicated in inflammation and disease, in contrast to traditional medications that may impact multiple immune processes in the body. They are typically injected beneath the skin or infused into a vein using a needle. ⁽²⁾

What are biologics? 

Biologics are engineered through a complex process of biomanufacturing, rather than being manufactured through chemical synthesis like synthetic drugs are. ⁽³⁾ The three main categories of biologics include:

• Monoclonal antibody (mAb) products

• Non-mAb products

• Vaccines

For autoimmune diseases, monoclonal (mAb) antibodies are widely used for treatment. Monoclonal antibodies are a type of protein created in the laboratory that are instructed to target specific antigens on cells, receptors or immune cells. ⁽²⁾

They are widely used to improve the outcome of the following autoimmune disorders and more:

• Rheumatoid arthritis 

• Psoriasis

• Psoriatic arthritis

• Inflammatory Bowel Disorders (Crohn’s disease and ulcerative colitis)

• Ankylosing Spondylitis 

• Multiple Sclerosis 

• Some forms of lupus and uveitis

  
  

How are monoclonal antibody biologics produced?

Recombinant DNA Technology is the most frequently used method to produce biologics. ^{(4, 5)}

Steps of Recombinant DNA Technology for mAb biologic production: 

1. A fragment of human DNA is inserted into a living cell culture, e.g. yeast, bacterial, viral, or mammalian cell. 

   
   

2. The specially selected living cells are instructed by the DNA fragment to produce large quantities of the desired therapeutic protein. These proteins are the monoclonal antibodies (mAbs) in biologics.

   
   

3. The proteins are harvested, isolated, and purified and used as the active ingredient in biologic medicine.

How do biologics treat autoimmune diseases?

During a flare-up of an autoimmune disease, the body’s healthy cells are attacked by the immune system. Biologics operate by interfering with the abnormal and overactive immune pathways triggered by autoimmune disease, reducing chronic inflammation and tissue damage. ^(1,2)

Categories of biologic medications used to treat autoimmune diseases:

1. TNF Inhibitors

Tumour necrosis factor (TNF) inhibitors are currently the most common biologic medications used to treat autoimmune disorders ⁽⁶⁾, and are most well-known to treat rheumatoid arthritis. 

Patients with an autoimmune disorder such as rheumatoid arthritis can have excessive levels of TNF-alpha (TNF-ɑ), a cytokine that promotes chronic inflammation. ^(6,7,16) A cytokine is a cell-signalling protein that the immune cells use to regulate immune responses.⁽⁸⁾ Biologics such as adalimumab, etanercept and infliximab ^(6,7,16), work by inhibiting or blocking TNF-ɑ.

1. A patient experiences a flare-up of rheumatoid arthritis. Their immune system mistakenly attacks their joints, causing inflammation and pain. 

   
   

2. The patient's immune cells produce high amounts of TNF-ɑ, a cytokine that binds to receptors that further escalate the inflammatory response.

   
   

3. The patient is administered the adalimumab biologic. Adalimumab contains a specific monoclonal antibody produced to bind to TNF-ɑ. 

   
   

4. Once the antibody binds to TNF-ɑ, TNF-ɑ is blocked from binding to TNF-ɑ receptors on other cells.

   
   

5. This inhibition of TNF-ɑ by the antibody in adalimumab leads to decreased inflammation. Symptoms such as pain, swelling and stiffness will improve, whilst also reducing the risk of progressive joint damage. 

   
   

This displays how biologics are able to target a particular immune system pathway, instead of inhibiting general immunological function.

2. B-cell Inhibitors

This biologic also treats autoimmune conditions, with examples including rituximab and ocrelizumab. For instance, when treating rheumatoid arthritis, the biologic is designed to target and bind to the protein marker CD20, which is located on the surface of many B cells.⁽⁹⁾ This allows the B cells to be removed, known as B-Cell Depletion Therapy. ⁽¹⁰⁾

1. When a patient experiences an autoimmune flare-up, their B cells can produce autoantibodies. These are antibodies that attack the body’s own cells and tissues. 

   
   

2. When a B-cell inhibitor such as rituximab is administered, the antibody in this biologic specifically binds to the CD20 marker on the surface of the B cells.

   
   

3. Once the rituximab-CD20 complex forms, the opposite end of the rituximab antibody (called the Fc region) acts as a signal for the immune system. 

   
   

4. The immune system then targets and destroys the B cells that are coated in rituximab. 

   
   

5. As these B cells are removed, less autoantibodies are present to participate in the autoimmune response. Therefore, the mechanisms and pathways causing inflammation and symptoms such as pain and swelling reduce. 

   
   

3. Interleukin Inhibitors

Interleukin inhibitors operate by blocking either interleukins or the interleukin cell receptor. To manage immune responses, white blood cells and other immune cells release interleukins. Overactivity of these immune response causes inflammatory and autoimmune responses, as interleukins are another type of cytokine. ⁽¹¹⁾

An example of an interleukin inhibitor biologic is ustekinumab, a biologic used to treat psoriasis and psoriatic arthritis. This biologic targets two cytokines: interleukin-12 (IL-12) and interleukin-23 (IL-23). ⁽¹²⁾

1. A patient’s immune system can become dysregulated due to a psoriatic arthritis flare-up, causing over-inflammation and damage to healthy tissues.

   
   

2. The patient’s immune cells produce interleukins, with IL-12 and IL-23 driving inflammatory responses. 

   
   

3. Ustekinumab binds to a specific protein component that both IL-12 and IL-23 share with each other. This prevents the interleukins from binding to the receptors on immune cells, reducing the inflammatory signal this would trigger.

   
   

4. This allows decreased immune activity and less inflammation, leading to improved and controlled symptoms for the patient.

Why choose biologics to treat autoimmune disorders?

Prior to biologics, autoimmune diseases were usually treated with corticosteroids and other immunosuppressive medications. Corticosteroids work broadly across the immune system, and can quickly and efficiently reduce inflammation. However, prolonged or frequent use can lead to the accumulation of negative side effects from the medication.⁽¹³⁾

As both corticosteroids and biologics can suppress or change immune function, this can increase an individual’s susceptibility to infections and potentially affect cancer risk. However, biologics act selectively upon the immune system, rather than widely suppressing it like corticosteroids. This may decrease the risks associated with broad immunological suppression.^{(13, 14)}

Side effects and disadvantages

Due to biologics being administered via IV infusion or self-injections rather than pill form, there can be a mild risk of nausea, fever, and injection-site reactions for patients. Occasionally, like with any medication, biologics also have the risk of triggering an allergic or hypersensitive reaction. However, this is uncommon and the risk will depend on the type of biologic being used.⁽¹⁵⁾

Biologics are more difficult to routinely manufacture since they are often larger, more complex structures compared to traditional medications. As they are made from living cells, there can be slight variations between batches of medications, and they are also sensitive to changes in pH, temperature, and other environmental factors. Therefore, biologics must be produced under highly-regulated manufacturing procedures, stored under specialised conditions and transported with temperature-controlling measures. These requirements mean the cost of producing and supplying biologics are considerably higher than standard medicines.^(13,16)

Summary

Biologics are a complex medication to develop, but they offer a more targeted approach to treat autoimmune diseases. They focus on disrupting the specific immune mechanisms that cause inflammation, rather than widely suppressing the immune system. Biologics can significantly decrease autoimmune activity and in certain conditions, prevent long-term damage to bodily tissues. However, as with all medications, they can carry certain risks that make them unsuitable as a treatment for some individuals. It is important for each patient’s case that the advantages and risks of biologics are carefully considered.

References

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16. Serraino, C. (2025). Biologics for Autoimmune Disease: What You Should Know. [online] Global Autoimmune Institute ». Available at: https://www.autoimmuneinstitute.org/articles/biologics-for-autoimmune-disease-what-you-should-know/ 

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