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PVACTM
PVACTM is an experimental 'vaccine' for psoriasis. It it currently undergoing clinical trials in Brazil, the Philippines, and the United States. It may be possible for it to be available in the U.S. as soon as, say, the Summer of 2002, but this is just a guess, really. It may be available sooner or later, and depends on the country. Since the testing is not yet complete, it's possible it may never become available.
On August 16, 2000, Corixa (a Seattle-based biotechnology firm involved in the development) announced that it hoped to have the Phase II trials on PVACTM completed by the end of the calendar year. Analysis of the data from the trial would commence after that point, for an unknown length of time, but the New Zealand Herald reports that results are expected by mid-February, 2001. A Phase III trial will be required for approval by the FDA before PVACTM can be approved for use in the U.S., but other countries have different requirements.
In the Phase II trials, patients with moderate-to-severe psoriasis were given two injections, 21 days apart. They were then 'followed' for 12 weeks. The researchers appeared to be hoping for a 75% reduction in psoriasis severity, at least, overall.
Some history: The history of PVACTM is sketchy at best, given a lack of detailed online reporting. Dr. James Watson, while working in India, attempting to cure leprosy with heat-killed Mycobacterium vaccae (MV) vaccine, found that a patient who also had psoriasis cleared completely. Dr. Watson's company, Genesis Research and Development, teamed with Corixa to run a Phase I trial of PVACTM in the Leonard Woods Memorial Laboratories in Cebu, the Philippines. In this "open label" trial, 58% of the 25 patients found their psoriasis at least 50% cleared. Another 8% got a 25-50% reduction in PASI score. The remaining 8 patients (33%) had either a worsening of psoriasis (2 of them), or less than 25% reduction in symptoms. Five patients (21%) had complete clearance of psoriasis symptoms which lasted for over six months. Given this fairly promising start, the Phase II trials in the U.S. were okayed by the FDA in January of 2000.
To at least one reporter, Dr. Watson said that PVACTM would probably need to be injected into patients once every eight to ten months.
There are lots of questions, though. PVACTM was at one point called a "curative vaccine," and still tends to be called a 'vaccine' even though some of the latest Corixa press releases describe it as a derivative of heat-killed MV. The definition of 'vaccine' that I'm familiar with presents vaccines as preventative measures only, and not treatments for diseases already underway. And given that patients may require injections every eight months, the label 'vaccine' seems to me to be ludicrous, and "curative vaccine" even more so.
It is not known why PVACTM works as well as it appears to have done. Not even the researchers closest to the testing and development seem to know. And many questions surround this particular dilemma: Psoriasis is fairly well established as what is known as a "Th1" mediated disease. This means that T-helper cells with a "type-1 cytokine profile" are primarily responsible for the symptoms we see (as opposed to a "Th2" mediated condition, such as an allergy - although it's important to note that many T-helper cells don't conform to either the "Th1" or "Th2" categories, as these are largely just highly simplified distinctions). It was thought, at one point, that PVACTM suppressed the "Th1" kind of immune cells, perhaps by boosting the "Th2" type. Even Dr. Watson seems to say, though, that PVACTM stimulates the "Th1" response. If psoriasis is a "Th1" mediated condition, stimulating that response would, in a common-sense sort of way, make psoriasis worse. So, the mechanism for action of this treatment remains a mystery to date.
December 30, 2003 Update: Development of PVACTM has been terminated. On December 22, 2003, Corixa, Genesis Research, and Medicis announced that in trials, PVACTM did not meet expectations for psoriasis treatment. In fact, according to a Genesis press release, PVACTM alone was found to treat psoriasis no better than placebo, and PVACTM in conjunction with UV therapy worked no better than UV alone. The failure of a 2001 trial foreshadowed these results.
In at least one article, the CFO of Medicis is quoted as saying that PVACTM wouldn't have been available for another four or five years, anyway, as it was still early in the development cycle. Medicis and Corixa are instead focusing on other drugs (for other diseases) which will make it to market more quickly, especially since Corixa is losing money, stopped another drug in development a month ago, and will be laying off 18% of its workers.
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