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Author: Vanessa Ngan, Staff Writer, 2003. Updated by Chief Editor: Hon Assoc Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, February 2015. Copy edited by Gus Mitchell. April 2018.
Biological agents, also known as biologics, biologic therapies, or biological response modifiers, are drugs derived from living material (human, plant, animal, or micro-organism). They interfere with specific parts of the body's immune system to treat and prevent immune-mediated inflammatory disorders and cancers. They are also called targeted therapies.
Biological agents approved for the treatment of psoriasis include:
The biological agent medications used for psoriasis are also used for other severe health problems. Registered indications in New Zealand in October 2019 are shown below.
Psoriasis is a disorder of the immune system. In psoriasis, abnormally large numbers of T cells trigger the release of cytokines that cause inflammation, redness, itching and flaky skin patches.
Biological agents work by interfering with specific components of the autoimmune response. Unlike general immunosuppressants that suppress the entire immune system, biological agents can fight more selectively and target only those chemicals involved in causing psoriasis.
Etanercept, infliximab and adalimumab belong to the class of biological medicines called tumour necrosis factor-alpha (TNFα) blockers. These work by blocking the activity of TNFα, the primary cytokine involved in psoriasis. Ustekinumab targets interleukin-12 (IL-12) and IL-23. Guselkumab and tildrakizumab target IL 23. Secukinumab, ixekinumab and brodalumab target IL-17.
The biological agents whose names end in 'mab' are monoclonal antibodies. Etancercept is a fusion protein.
All these biological medicines are given at defined intervals. The interval between doses is dependent on each individual biological medicine. Etanercept, alefacept and efalizumab are usually once weekly, and adalimumab is every two weeks by self-administered subcutaneous injection. Infliximab is given by intravenous infusion at a hospital or clinic, 3 times over a period of 6 weeks and then every 8 weeks.
In many cases, other topical and systemic medications for psoriasis (eg, methotrexate) may also be prescribed in an attempt to improve efficacy.
Biological medication is often very effective in psoriasis. However, in some cases, they lose their effectiveness after a period of time (secondary failure) and other treatment may be required.
To date, biological agents for psoriasis appear to have very few side effects. Because of their precise targets, they appear not to damage the entire immune system the way that general immunosuppressants do. However, biological agents should still be considered immunosuppressive and may increase the risk of infection and reactivation of tuberculosis (TB). Uncommon infections with organisms such as listeria and legionella may be more common and more serious in patients on biological agents. Infections are more common in older patients on biologics.
Screening for latent TB and other infections (hepatitis B, HIV and others) should be undertaken prior to commencing a TNFα inhibitor and other biological agents.
On the other hand, mortality may be reduced in patients taking TNFα inhibitors compared to that in patients with psoriasis that are not taking them. This is due to a marked reduction in myocardial infarction. Some of the newer biological agents may also be associated with lower rates of malignancy than arise in matched patients that are not taking them.
Due to the high cost of these medicines, their use is limited to patients with moderate to severe psoriasis where:
In New Zealand, infliximab, adalimumab, etanercept and secukinumab are funded by PHARMAC for some cases of severe psoriasis on Special Authority application.
Immunisation status should be reviewed prior to starting treatment with biological agents. If necessary, vaccines should be updated prior to treatment. Annual influenza vaccination is recommended.
As they may induce illness in immunodeficient individuals, live vaccines should not be used during treatment with biological agents. Currently-available live attenuated viral vaccines include measles, mumps, rubella, varicella, yellow fever, the intranasal form of influenza vaccine, and the oral polio vaccine. Live attenuated bacterial vaccines include BCG and oral typhoid vaccine.
It is recommended that patients on biological medications should be monitored, and should have routine blood tests at least every 6 months or so, including full blood count and liver function tests. Screening for latent TB should be repeated from time to time.
Research and development in the field of biological agents for psoriasis for treating psoriasis in 2015 include:
Other biological agents used for severe skin diseases (January 2018) include:
There are many other promising biological agents under investigation for skin conditions.
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