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Page 1 of 5 Biologics
Until this year, all traditional therapies for psoriasis have depended on treating the ‘symptoms’ of the condition once they have shown themselves on the skin – be that as a ‘topical’ cream or lotion, which is applied directly onto the affected areas or, in the case of systemics (MTX, Cyclosporin, Hydroxyurea or Acitretin), as an internal drug. Scientists have been researching the ‘causes’ of psoriasis for many decades and have finally isolated parts of the process which cause the abnormally high cell division in the skin of a sufferer. This is a hugely complex chain of events. To understand this as a ‘layperson’, the best way of thinking about the process is as a mechanical clock: “The outer surface (or dial) belies the complexity of what is going on inside. Take off the cover and at once you are confronted with a mass of springs, axles, cog wheels and balance wheels. Every part has to be in the correct position and functioning in order to tell the time. To prevent a clock telling the time, you could do many things – remove the hands while leaving the mechanism running, or block the mechanism by jamming up any one of the many components. The surface of psoriatic skin is like the dial – simply the end result of a very complex chain of events. Look inside, and you find a bewildering mixture of cells and chemicals all playing a role in perpetuating the disease. Many of these will be communicating with each other either by direct contact through receptors on their surface – in the way that the cog wheels of a clock interact – or by the release of chemical signals called cytokines. There are many cytokines with names such as tumour necrosis factor, (TNF), interleukins, interferons, and growth factors. These can trigger cell multiplication, abnormal development and inflammation” (ABPI – 03) To understand psoriasis, scientists have had to separate out all these ‘mechanical’ components. Once this is done, they can devise drugs which ‘jam’ up the works and prevent the process above, and thereby ‘turn’ off the psoriasis clock. The result of this research is what has become known as ‘Biologics’ or ‘Protein Fusion Drugs’. There are currently a number of biologics being researched and trialled across the world. Three of these are going through the process of UK licensing as of May 2005 for general patient use. These are Alefacept, Etanercept and Efalizumab: Alefacept/Amevive – Biogen Idec (www.amevive.com)How does it work? Amevive is a fusion of two human proteins and works in two ways: it appears to block the CD-2 receptors on the T-cells and rebalances their over-activity and it also kills off the abnormal keratinocytes by re-programming the immune system. How is it administered? Patients are injected with 15mg intramuscularly or intravenously once a week for an initial 12-week period. This can be repeated up to twelve times if the results of the first course are adequate. Blood work will be checked for T-cells levels and general health alongside the course. What are the side effects? Phase 2 & 3 testing has shown common side effects to be a sore throat, dizziness, nausea, headaches, chills, muscle aches and injection site inflammation. Even though part of the immune system is suppressed, no opportunistic infections were reported during trials. However, these are short term side effects. The long term effects cannot be calculated until the drug has been widely used for many years across a large number of patients. What are the results? Clinical tests show 38-42% of patients taking Amevive had a 50- 75% improvement. This can continue for up to seven months after the initial twelve week course. The continued remission time is one of the beneficial aspects of Amevive. |
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