Etanercept for psoriasis
What is etanercept?
Etanercept belongs to the class of biologic medicines called tumour necrosis factor (TNF) blockers. TNF is a cytokine—a messenger chemical. The trade name for the original drug is Enbrel®. Generic etanercept biosimilars are also under development.
Etanercept is approved for the treatment of psoriasis, psoriatic arthritis, and ankylosing spondylitis in adults. It is approved for the treatment of psoriasis and juvenile idiopathic arthritis in children from 4 years of age. In the USA, etanercept is also approved for use in moderate to severe chronic plaque psoriasis in children aged 4 and older.
In New Zealand, PHARMAC has approved funding for severe treatment-resistant psoriasis in adults on Special Authority application. In children older than 4 years, it is approved for use for up to 24 weeks.
How does etanercept work?
Etanercept is genetically engineered from human protein. It works by directly binding to TNF molecules in the blood and diseased tissue. Etanercept-bound TNF cannot bind to or activate TNF receptors. TNF is involved in normal inflammatory and immune processes, and is there are high levels in skin affected by psoriasis.
How effective is etanercept in psoriasis?
Randomised, double-blind, placebo-controlled studies of etanercept in moderate-to-severe chronic plaque psoriasis showed that it significantly decreased disease activity (PASI score) with a favourable safety profile.
The PRESTA trial of bi-weekly dosing for 12 weeks then 50 mg once weekly reported that 70% of patients with moderate-to-severe chronic plaque psoriasis and psoriatic arthritis on etanercept achieved PASI 75 by week 24. It was also effective for psoriatic arthritis, with 77% achieving psoriatic arthritis response criteria. The similar PRISTINE trial reported 78% achieved PASI 75 by week 24, with the use of unrestricted additional topical medications after week 12.
How is etanercept given?
Etanercept is given by subcutaneous injection. The usual dose for psoriasis is 50 mg twice weekly for the first twelve weeks, then once weekly. After initial counselling and training by a health professional on how to prepare and inject the drug, patients can usually self-administer at home using a pre-filled syringe or autoinjector. Injections are usually into the thigh, abdomen or upper arm. A different site should be used at each injection to reduce soreness and prevent the skin from becoming tender, red, bruised or hard.
Etanercept can be give alone or if necessary, in combination with topical treatments, methotrexate, and/or phototherapy.
In children, the dose is 0.8 mg/kg up to a maximum dose of 50 mg once weekly.
Etanercept injections needs to be kept cold, including when travelling. See travel letter, which explains the need to carry the medication as hand luggage.
Precautions necessary for patients on etanercept
Careful assessment is required before treatment with etanercept. Regular follow-up visits to monitor the safety and efficacy of treatment are also necessary.
Because etanercept works by selectively targeting a cytokine involved in psoriatic arthritis and/or psoriasis, theoretically it should have little effect on the rest of the body's immune system. Even so, caution must be taken when considering its use in patients prone to infections or in those with chronic or recurrent infections. It should not be used in patients with sepsis or active infections in case it makes these worse.
Etanercept should not be started during pregnancy (category B2) or breast feeding.
Patients who require major surgery may be advised to stop etanercept temporarily 2 to 3 weeks prior to a planned operation. It can be started again 2 weeks after surgery, providing no infection is present.
Screening tests prior to etanercept
Screening tests recommended prior to starting etanercept usually include full blood count, liver enzymes, serum creatinine, urine analysis, antinuclear antibody (ANA), pregnancy test if relevant (urine or serum), HAV/HBV/HCV and HIV status.
Tuberculosis screening includes chest X-ray, and Mantoux intradermal test or QuantiFERON-TB Gold blood indirect test.
Vaccinations and etanercept
Immunisation status should be reviewed prior to starting etanercept. If necessary, vaccines should be updated. Annual influenza vaccination is recommended.
As they may induce illness in immunodeficient individuals, live vaccines should not be used during treatment with etanercept. Currently available live attenuated viral vaccines include measles, mumps, rubella, varicella, yellow fever, influenza (intranasal vaccine) and oral polio vaccine. Live attenuated bacterial vaccines include BCG and oral typhoid vaccine.
Side effects and risks of etanercept
Etanercept appears to be very well tolerated. Mild to moderate injection site reactions (redness, swelling, itching, pain) appear to be the most common side effect. These tend to occur in the first month and then become less frequent. Cool compresses and 1% hydrocortisone ointment may help to alleviate injection site discomfort. Some people complain of itchy skin, and weight gain has been reported.
If any of the following symptoms or signs are severe or do not go away you should contact your doctor.
- Coughing, wheezing, breathlessness or chest pain
- Nausea and/or vomiting and/or abdominal pain
- Fever, headache, chills or other signs of infection
- Hot, red, swollen area on the skin
- Bleeding or bruising
- Unexpected weight loss
- Sore eyes (uveitis has been described as a possible uncommon adverse reaction to etanercept).
Severe cutaneous reactions to etanercept have rarely been reported, including urticaria, angioedema, anaphylaxis and Stevens Johnson syndrome / toxic epidermal necrolysis.
Patients treated with etanercept may be at slightly greater risk of lymphoma and possibly other malignancies compared to the untreated population. In most cases, the patients have also been taking other medicines that suppress the immune system such as azathioprine or mercaptopurine.
Other conditions that have been reported in patients on etanercept include demyelinating diseases such as multiple sclerosis (MS), cardiac failure and bone marrow suppression. New onset of autoimmune diseases may occur; these may be associated with the underlying skin disease or its treatment.
Monitoring while on etanercept
It is recommended that patients on biologic medications have routine blood tests every 6 months or so, including full blood count and liver function tests. TB testing should also be repeated from time to time.