What are Biologics?
Biologics 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 targeted therapies. Currently four biologic therapies are available in New Zealand to treat psoriasis. These are Infliximab, Etanercept, Adalimumab and Ustekinumab.
How do biologics work in psoriasis?
Psoriasis is a disorder of the immune system. This appears genetically based. The patients T cells ( a type of white blood cell) trigger the release of cytokines (chemicals in the body’s immune system) that results in inflammation, redness, itching and flaky skin patches characteristic of psoriasis. Biologics work by interfering with specific components of the autoimmune response. Unlike general immunosuppressant’s that suppress the entire immune system, biologics are more selective. Etanercept, infiximab and adlimumab belong to the class of biological medicines called tumour necrosis factor (TNF) blockers. These work by blocking the activity of TNF-alpha, the primary cytokine involved in psoriasis. Ustekinumab targets interleukin-12 (IL-12) and IL-23. New biologics under investigation that targets IL-17. Other agents target the intercellular communications pathways.
How are biologic given for psoriasis?
All these biological medicines are given at defined intervals. The interval between doses is dependent on each individual medicine. Etancerpt is injected once weekly, adalimumab every two weeks by self-administered subcutaneous injection. Infliximab is given by intravenous infusion at the clinic, 3 times over a period of 6 weeks, then every 8 weeks and Ustekinumab is given every 3 months. In many cases systemic medications for psoriasis (eg. Methotrextae) may also be prescribed in an attempt to improve efficacy Biologic medication are usually effective in psoriasis. However, in some cases, they lose their effectiveness after a period of time and other treatment may be required.
What are the possible side effects of biologics?
To date, biologics for psoriasis appear to have very few side effects. Because of their precise targeting, they appear not to damage the entire immune system. However, biologics should still be considered immunosuppressive and may increase the risk of infection and in particular reactivation of TB. Uncommon infections with organisms such as listeria and legionella may be more common and more serious in patients on biologics. There is also a slightly increased risk of skin cancer, especially squamous cell carcinoma (SCC) and some lymphomas.
When should biologics be used?
Due to the high cost of these medicines, their use is limited to patients with severe psoriasis where all other treatments have failed or side effects have become intolerable or toxicity has occurred. Our clinic has expertise in the use of biologic agents having been involved in many clinical trials involving their use.