Mexico First to Approve Prostate Cancer Drug Invented at Weizmann Institute

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Mexico has become the first nation to approve a drug based on bacterial chlorophyll to treat early-stage prostate cancer. The breakthrough technique invented by Israeli scientists, which seems to involve no side effects to speak of and can preclude prostate removal, is also undergoing approval processes in Europe.

The combined therapy of the novel drug, Tookad Soluble, and laser illumination was invented at the Weizmann Institute of Science, Rehovot. Clinical development was done together with Steba Biotech, a Luxembourg company specializing in prostate cancer therapies.

The therapy, provided as an outpatient procedure lasting just a few hours, has been approved by the Mexican health authority Cofepris for the focal treatment of early-stage prostate cancer, Weizmann announced Monday.

Focal treatment is a cousin of targeted treatment. The idea is to treat diseased tissue while not touching noncancerous tissue, since many of the cancer therapies are generally poisonous or otherwise obnoxious to the body. It is the latest wrinkle in prostate cancer therapy, as an alternative to whole-gland therapy, culminating in radical excision of the offending gland.

The therapy paradigm developed by Prof. Yoram Salomon of the Biological Regulation Department and Prof. Avigdor Scherz of the Plant and Environmental Sciences Department at Weizmann consists of an intravenous Tookad infusion, immediately followed by shining near-infrared laser light "inserted" into the sick tissue using thin optic fibers, guided by ultrasound.

Plants famously use chlorophyll to turn sunlight energy into food. Certain bacteria can do the same. Scherz is the one who first cooked up Tookad in his lab from bacteriochlorophyll.

Chlorophyll-containing bacteria are microscopic, but here we see they can proliferate to the point of being noticed by NASA: A bloom of cyanobacteria forming around Fiji. Credit: Norman Kuring, NASA Earth Observatory, Wikimedia Commons

Once the drug is administered, the laser light "turns on" the circulating drug locally. The result is the extensive generation of unstable toxic molecules, oxygen and nitric oxide radicals, which damage the blood vessels feeding the tumor. Starved for blood and oxygen, the tumor tissue dies but nearby tissues remain unaffected.

Where the light is not shined on the drug, it circulates around the patient’s blood system doing nothing much until being totally cleared after some three to four hours.

"The use of near-infrared illumination, together with the rapid clearance of the drug from the body and the unique non-thermal mechanism of action, makes it possible to safely treat large, deeply embedded cancerous tissue using a minimally invasive procedure," Weizmann stated.

The marketing approval follows success in the Phase III clinical trial in Mexico, Peru and Panama, involving 80 patients. The test confirmed efficacy and the "minimal side effects" previously found in Phase II clinical trials, Weizmann stated.

Pressed by Haaretz, the Weizmann team explained that the side effects found were "transient and were related to the procedure itself" – meaning, not the drug. They included, for instance, the side effects that may be caused by insertion of a catheter, such as burning when urinating shortly afterwards. Others may feel nausea after anesthesia, but the Tookad itself was not seen to have side effects.  

 Meanwhile in Europe, a second Phase III clinical trial was recently wrapped up. The study compared disease progression, the rate of freedom from cancer and urinary and erectile functions in patients treated with Tookad and those undergoing active surveillance with a follow-up of two years, among more than 400 patients in 11 European countries. The findings are being evaluated by the European Medicines Agency.

Weizmann and Cofepris have not begun the process of seeking marketing approved in Israel yet. The normal process for any Israeli-developed drug is to first seek approval in the United States or Europe, explained the institute's spokesman, Yivsam Azgad: Israel is simply too small to be able to sustain a system for the regulatory testing of drugs, which is extremely expensive and complicated. When the Food & Drugs Administration in the United States or European authorities test and approve a drug, they hand over the file with all the test information, which Israel reviews for the sake of its own regulatory approvals.

Tolypothrix, another species of cyanobacteria, which contain chlorophyll molecules to fix sunlight into food. Credit: Matthew Parker, Wikimedia Commons