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Biotech / Medical : QLT PhotoTherapeutics (QLTI)
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To: Zeev Hed who wrote (318)4/11/1998 4:09:00 PM
From: SC  Read Replies (1) of 1321
 
I believe you are correct regarding the singlet oxygen state (but don't know for sure). As far as spot size for the laser used for this particular procedure I simply don't know. The lesion is identified by fluorescein angiogram but as to how adequate presumably overlapping treatment is determined I don't know. In the photocoagulation procedures currently used the laser produces an immediate whitening of the retina in the area where the spot is applied, I don't know if the laser used to activate the vertoporphyrin causes any immediate effect. I have seen before and after flourescein angiograms and they were impressive (the angiogram looked normal 1 week following treatment). However the presenter said the srnvm recurred but was smaller 12 weeks following treatment. I don't recall how long the photosensitization lasts but the patient needs to take precautions to avoid excessive exposure to sunlight(I'm also not sure what constitutes excessive)until the photosensitization wears off. Obviously if the photosensitization wears off in days rather than weeks ongoing retreatment would be more practical. Other potential concerns would be if there was any cumulative toxicity to any organ system. The presenter did say that the companies response when told of the recurrence was a suggestion to re-treat. I believe the presentation that I saw was based on the initial pre-TAP investigations. The presenter stated that they tried higher doses of vertoporphyrin but this caused closure of the normal retinal vessels (an absolutely unacceptable outcome). I saw the presentation at a continuing medical education conference at Emory University about a month ago.

Very exciting, but also highly speculative as any new drug or new use of an existing drug always is prior to FDA approval. I usually stay away from investments based on promising but not yet approved drugs for this reason (it's too much like gambling). I wouldn't bet the farm on this one yet but I couldn't resist making a relatively small wager on this one.

sc
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