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Biotech / Medical : Pharmacyclics (PCYC) -- Ignore unavailable to you. Want to Upgrade?

To: QuietWon who wrote (407)	2/15/1999 9:19:00 PM
From: Biomaven	Read Replies (2) \| Respond to of 717

The Economist has an article about PDT. It's available on the web starting from www.economist.com(free registration required). Discusses QLT and DUSA, and here's the part about PCYC: Deeper still The prospects for photodynamic therapy, however, extend beyond the eyes and the skin. Thanks to fibre-optics, it is now possible to illuminate many of the body's remotest organs and darkest orifices. And where there is light, and a photosensitive drug, there may well be action. Since porphyrins are taken up by blood vessels, some researchers reckon that they might be useful in treating atherosclerosis—an inflammatory process that thickens and damages the vessel wall. Among these researchers are Jonathan Sessler, a chemist at the University of Texas at Austin, and Richard Miller, his former oncologist. The two have formed a company called Pharmacyclics, based in Sunnyvale, California. It is busy testing synthetic porphyrins on diseased blood vessels. Pharmacyclics's drug, called lutetium-texaphyrin, is activated by red light. That means its optical “switch” is able to shine through blood and reach the vessels' linings unhindered. Lutetium-texaphyrin has proved successful in shrinking atherosclerotic lesions in leg arteries. Patients are injected with the drug, and then have a catheter carrying an optical fibre threaded into the vessel to be treated. Conventional anti-atherosclerosis therapy, which is called angioplasty, also employs a catheter. This, however, has a tiny balloon at its business end. The balloon is inflated against the diseased wall to squash the lesion and clear the vessel. But angioplasty can damage the underlying tissue, causing more lesions to form—a troubling complication known as restenosis. A 12-minute dose of light beamed down the fibre on to the lesion to be shrunk seems to get round this. In a pilot study, admittedly of only 14 patients, 11 of them had their blocked vessels opened by at least 10%. And there was no sign of restenosis. Like QLT, Pharmacyclics is also testing its drug on cancers. This seems a promising approach for tumours in places where catheters can reach, such as the gut or chest wall, but not much use for those buried in more obscure corners of the body. Only X-rays penetrate this far. But X-rays are, in essence, just high-frequency light. That means they, too, can be used to generate singlet oxygen, given the right molecular intermediary. Pharmacyclics has developed such an intermediary, called gadolinium-texaphyrin. In mice with experimentally induced cancer, a single dose of this drug and a single blast of X-rays was enough to double the rate of survival. In people, gadolinium-texaphyrin has been tested against secondary brain cancers—those caused by renegade cancer cells breaking off from a primary tumour in the breast or lung and setting up shop in the head. So far, more than 60 patients have been treated with ten-days' worth of gadolinium-texaphyrin and X-rays. Of those, over three-quarters have had their brain-tumour load halved. They have also survived longer than would be expected with conventional radiotherapy. Larger, more rigorous clinical trials of gadolinium-texaphyrin have just started, and the approach is also being tried for prostate, pancreatic and neck tumours. Photodynamic therapy may not be the magic bullet for cancer, but even a little light relief is welcome.