Understanding Biologics

What is it? 

Biologics are a class of drugs that can be used in the treatment of moderate to severe inflammatory bowel disease (IBD). The two common forms of IBD are ulcerative colitis and Crohn’s disease. In most instances, biologics are not required to manage IBD, however, they are the mainstay of treatment for some patients with IBD.

How are biologics different from other drugs? 

Biologics are essentially proteins that can be produced by living cells. As a result, they tend to be much larger compared to traditional drugs that are routinely used in IBD (eg. Azathioprine, 5-Aminosalicylates). The route of administration is also different, as they need to be given via an injection.

What are the common biologics in IBD?

• Infliximab (Remicade™ and Remsima™)
• Adalimumab (Humira™)
• Vedolizumab (Entyvio™)

When are these biologics used? 

Infliximab and Adalimumab are licensed for use in patients with moderate to severe IBD when other immunosuppressant drugs (eg. Azathioprine, methotrexate) are not effective or poorly tolerated. They are also be used in conjunction with immunosuppressants and other conventional drugs for better effect.

Vedolizumab is awaiting HSA registration for licensed use in Singapore.

How are biologics given? 

As biologics are proteins, they cannot be taken orally as the digestive system will break them down. Thus, they have to be administered through other routes. Infliximab and vedolizumab are given via infusions. Adalimumab is administered via a subcutaneous (under the skin) injection either into the abdomen or thigh.

Risks of biologics

Biologics work by suppressing the immune system via different mechanisms. Infliximab and adalimumab are known as anti-TNF (anti-tumour necrosis alpha) agents as they dampen the effect of TNF (a chemical produced in the body that promotes inflammation). Vedolizumab is an anti-integrin protein, which works by reducing the number of circulating white blood cells from migrating to the gut, thus lowering intestinal inflammation.

As a consequence, anti-TNF agents lower the overall immunity of the patient, which may increase the risk of infections and cancers.

Side effects and intolerance 

As biologics are given via injections, the injection sites may develop redness, pain, bruising and itching. Occasionally, fever, headaches and allergic reactions may occur.

Infection risk 

Anti-TNF drugs impact the body’s ability to fight infections, including uncommon infections like tuberculosis and hepatitis B. As a result, your doctor may do tests to screen for such diseases prior to starting anti-TNF treatment.

The data for vedolizumab seem to suggest that it is safer than anti-TNF drugs as systemic immunity is less affected.

Cancer risk 

Anti-TNF have been noted to cause a small increase in the risk of developing lymphoma, uncommon cancer.

Conclusion 

Although useful, biologics do have risks associated with their use. However, in carefully selected patients, the benefits of biologics controlling intestinal inflammation in IBD would far outweigh the dangers of biologics. Do discuss this with your gastroenterologist should you need more information.

Dr Malcolm Tan
Associate Consultant
Dept of Gastroenterology and Hepatology
Changi General Hospital