Information about the experimental psoriasis drug PVAC, which was supposed to be a vaccine.

PVAC™ 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 PVAC™ 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 PVAC™ 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 PVAC™ 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 PVAC™ 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 PVAC™ would probably need to be injected into patients once every eight to ten months.

There are lots of questions, though. PVAC™ 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 PVAC™ 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 PVAC™ suppressed the “Th1” kind of immune cells, perhaps by boosting the “Th2” type. Even Dr. Watson seems to say, though, that PVAC™ 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 PVAC™ has been terminated. On December 22, 2003, Corixa, Genesis Research, and Medicis announced that in trials, PVAC™ did not meet expectations for psoriasis treatment. In fact, according to a Genesis press release, PVAC™ alone was found to treat psoriasis no better than placebo, and PVAC™ 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 PVAC™ 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.


Termination of Development:
Company News:
Corixa (December 22, 2003)
Genesis (December 22, 2003)
Medicis (December 22, 2003)
Corixa, Medicis giving up on psoriasis drug (December 23, 2003)
Corixa and Medicis Halt Psoriasis Drug (December 23, 2003)
Corixa discontinues work on psoriasis treatment (December 22, 2003)
Genesis Research Provide Update On PVAC™ Treatment (December 23, 2003)
Medicis, Corixa end psoriasis drug development (December 22, 2003)

Their Web site is defunct as of May 11, 2010

Genesis Research & Development Corporation Limited:
Their Web site is defunct as of May 11, 2010

Bioterrorism has formidable foe in Corixa (September 29, 2001)

Clinical Trial of PVAC™ with UVB in New Zealand (June 28, 2002)

Corixa starts new clinical trial of psoriasis drug (June 6, 2002)

Drug Trials Hit Corixa, Alexion (February 21, 2001)

Genesis Announces New U.S. Clinical Trial of PVAC™ (June 7, 2002)

Immunotherapy with Mycobacterium vaccae in the treatment of psoriasis.” (May 1998)

Improvement in psoriasis after intradermal administration of delipidated, deglycolipidated Mycobacterium vaccae (PVAC): results of an open-label trial.” (May, 2001)

Interview With Corixa CEO (March 8, 2001)

Medical Stock Spotlight (February 19, 2001)

PVAC (Corixa/Genesis/Medicis). (Abstract — November, 2002)

ShareChat Investor Interview: Genesis CEO, Dr Jim Watson (November, 2001)

TalkTalk — Psoriasis

BBC News: Vaccine “Switches Off” Psoriasis (January 11, 2001)