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Biologic agents are immunosuppressant disease modifying drugs used in the treatment of psoriatic arthritis. They are made from biological (human or animal-based) proteins rather than artificial chemicals, much in the way that insulin was made from animal sources in the past.

Biologics are now available in two forms.  The originator form and a version called biosimilar.  These versions are offered as an alternate of the original form and are approved according to the same standards of pharmaceutical quality, safety and efficacy that apply to all biological medicines.

The treatments are different from other psoriatic arthritis medications as they are designed specifically to block particular parts of the immune system that cause inflammation. This is different to some conventional disease modifying drugs, like methotrexate, which generally suppress the immune system, or anti-inflammatories, which treat the symptoms of the disease.

They work by blocking the action of specific immune messengers or targeting particular cells of the immune system that are important in the causes of psoriatic arthritis. These messengers cause inflammation in certain cells by triggering the immune system. The most commonly used biologic and biosimilar products psoriatic arthritis are drugs that block a messenger called TNF (tumour necrosis factor). Alternatively, they can block the activation of certain immune cells (often T cells in psoriatic arthritis) or the release of other messengers (called interleukin 12/23 or interleukin 17) from them. The treatments act by copying the effects of substances naturally made by the immune system.

In the UK they are not considered first-line therapy. There are recommendations from the National Institute for Health and Care Excellence (NICE), the Scottish Medicines Consortium (SMC) and the All Wales Medicines Strategy Group (AWMSG) which define who can access these treatments. Usually they are only available to patients who do not respond to systemic therapies such as methotrexate. The choice of which biologic drug to use will depend on the severity of your joint and skin disease and any other medical problems which you have.

Biologic and biosimilar agents are given by injection or infusion and usually work quickly to relieve the symptoms and swelling associated with psoriatic arthritis. Although studies show that most people will improve within four to six weeks of treatment, a majority will notice some improvement after the first or second injection or infusion. Some people, however, can take the full 12 weeks to notice a response.

The most common side effects (adverse events) seen with injected medicines include skin reactions at the injection site. These occur in fewer than 30% of people and may last for up to two weeks. The most significant side effect of these medications is an increase in the risk of all types of infections, including tuberculosis (TB). Before starting an anti TNF (tumour necrosis factor) medication, your risk of TB is assessed and a TB skin or blood test (Mantoux test) is often carried out. The British Thoracic Society (BTS) guidelines state that Caucasian patients who are UK-born should not be tested, as the risk involved with TB prophylaxis (measures designed to preserve health) is higher than the risk of TB. Treatment with these agents should be stopped while you have an active infection and are taking an antibiotic, or if you have a high fever. People with significant congestive heart failure should not take anti-TNF agents.

In the UK reports of side effects to medicines should be reported to the MHRA Yellow Card scheme. In addition, the companies marketing treatments whether it’s an originator or a biosimilar, may have further increased safety data gathering once a product is available to the patients. 

Reference NHS UK 

Current available biologic agents