Q) What can you tell me about the new systemic drug that treats atopic dermatitis?
A) Dupixent (Dupilumab) was approved by Health Canada in 2017 but, despite its uniqueness as a new treatment option for atopic dermatitis, it has had a relatively slow uptake due to the same challenge that has sidelined many new drug treatments over the last decade; namely, its exorbitant cost.
Atopic dermatitis (AD) is considered one of the more severe forms of eczema (a nonspecific term used for many types of skin inflammation) that results in the skin becoming very itchy and inflamed and potentially leads to redness, swelling, vesicle formation (which look like tiny blisters), cracking, weeping, crusting and/ or scaling of the affected region(s). The skin area itself almost always appears to be very dry indicating that a large source of the problem seems to lie with maintaining proper hydration of the skin.
It tends to be a disorder of flares (this is when the skin becomes very inflamed) and remissions (when the skin appears relatively normal) with the flares triggered by multiple factors such as low humidity, seasonal allergies, the use of harsh soaps or detergents, stress, changes in hormone levels and cold weather.
Atopic dermatitis is far more common in children than it is in adults (up to 20% of children vs 3% of adults) and usually initially presents in the first 6 months of life. As the above numbers indicate, most children grow out of it but some will continue to have flares into adulthood.
No one is actually sure as to what causes atopic dermatitis but it is believed that a substance from either within or outside the body causes the immune system to over-react and produce inflammation.
Research has shown that many people with AD have a mutation of the gene responsible for producing the protein filaggrin. This protein is involved in maintaining a healthy protective barrier at our outermost skin layer. Impairment of this layer allows the loss of excess moisture from the skin and can allow viruses and bacteria to more easily penetrate into the body leading to the symptoms noted above.
Traditional treatment has relied on a variety of creams; mainly the corticosteroids (such as hydrocortisone & betamethasone) along with the topical calcineurin inhibitors (Protopic and Elidel) and vitamin D analogue creams such as Dovonex. For those who do not respond to topical (read cream/ ointment) therapy alone, there are a number of systemic treatments (i.e. pills) that were originally used for other conditions but have been proven to work in treating AD such as methotrexate, azathioprine and cyclosporin.
Now comes Dupixent, the first biologic medication approved for the treatment of adults with moderate to severe AD (what actually constitutes moderate to severe is not firmly defined but a rough definition is that the condition of your skin is bad enough to have a significant negative impact on your life). Biologics are the new”ish” class of drugs that are genetically engineered from proteins taken from living tissue and are designed to target specific parts of our immune system that are involved with inflammation.
Dupixent blocks two of the interleukin proteins (IL-4 & IL-13 for the bio nerds amongst us) from exerting their pro-inflammatory effects in AD. It is given as a sub cutaneous (which is the same manner in which insulin is injected meaning that patients can taught to self administer relatively easily) injection every 2 weeks at a dosage of 300mg (although the initial shot uses a dose of 600mg). In clinical trials, more than half of patients using Dupixent for 16 weeks reported their AD symptoms were reduced by 75%.
Side effects, always a concern with biologics, seem relatively mild with the most common ones being conjunctivitis (pink eye), cold sores on the lips and mouth and redness and pain at the site of the injection. Rarely, eosinophilia (a blood cell disorder in which the number of eosinophils is increased) is a possibility. There are some drug interactions of note (e.g. warfarin) but these can for the most part be avoided with the proper precautions.
The drug right now is only intended to be used in adults but trials are under away investigating its safety and effectiveness in children as young as 6 months of age.
The downsides are the lack of long-term safety data and the price tag. Dupixent costs about $2,300 a month and must be taken life long as its effects wear off when the treatment is stopped. It is this extraordinary price tag which has caused governments (& undoubtedly some private insurers as well) to shy away from covering the cost of the drug despite its promise as a safe and effective agent which is truly a shame.
However, given the growing strain on our health care budget that our continually greying population is causing, expect decisions such as this to become the norm as our bureaucrats struggle to maintain taxes and cover increasingly expensive new drugs.
