YM BioSciences announces results of cancer antibody-radionuclide conjugate development collaboration

Collaboration utilizes antibodies selectively targeting cancer cells combined with nuclear delivery technology developed at University of Toronto

YM BioSciences Inc. (NYSE Amex:YMI, TSX:YM) today announced results of a collaboration with researchers at the University of Toronto for the development of highly potent antibody-radionuclide conjugates for use in the treatment of cancer. The approach has successfully concluded its first series of proof-of-principle experiments establishing promise for future development and application. The first antibody conjugate is nimotuzumab coupled to a radionuclide, indium-111, and a cell-nucleus delivery system developed in the laboratory of Dr. Raymond Reilly, Professor, Leslie Dan Faculty of Pharmacy at the University of Toronto.

"Nimotuzumab is ideal for conjugation to potent compounds with a high cytotoxic activity such as the radionuclide used in this initial experiment in which it is combined with a cell-nucleus delivery system, or targeted radiotherapy, because of nimotuzumab's demonstrated attribute of selecting for antigen over-expression," said David Allan, Chairman & CEO of YM BioSciences Inc. "This property of selectivity differentiates nimotuzumab from other EGFR-targeting monoclonal antibodies permitting it to carry toxic payloads without the collateral toxicity to normal cells that would occur with indiscriminate binding."

"YM anticipates that the addition of a potent compound with a high cytotoxic activity to YM's affinity-optimized IntelliMab(TM) HER2-targeting antibody analog, announced on December 10th, 2009, that avoids the demonstrated cardiac toxicity of Herceptin, would be a valuable addition to the armamentarium against breast cancer," said Sean Thompson, Vice President, Corporate Development of YM and General Manager of the IntelliMab platform. "Since it is nimotuzumab's apparently ideal affinity optimization that permits it to combine efficacy with minimal toxicity YM plans to follow these initial experiments with nimotuzumab with our IntelliMab HER 2-targeting antibody since it is expected to enjoy the same attributes as nimotuzumab in specifically targeting cancer cells and largely avoiding cardiac myocytes."

"The prospect of safe and selective delivery of potent compounds with high cytotoxic activity, including radionuclides, to cancerous tissues via antibodies with improved attractive biodistribution properties is most compelling," said Dr. Reilly. "Administration of many anticancer toxins is challenging and requires efficient and selective targeting to address concerns with normal tissue toxicity. I anticipate that these results will be submitted for upcoming cancer research symposia."

Preliminary experimental data with the nimotuzumab radionuclide conjugate demonstrates that the combination is active against cancer cells over-expressing EGFR, as is nimotuzumab alone, but with significantly improved potency due to the radiation emitted by the indium-111 conjugated toxin. "I look forward to generating additional data to build on these promising initial observations and expand our collaboration to new antibodies developed by YM's IntelliMab platform," noted Dr. Reilly.

YM's IntelliMab technology is designed to generate novel antibodies that selectively target cancer cells and was developed from the same principle believed to cause nimotuzumab to selectively target cancer cells over-expressing EGFR while avoiding the lower density of EGF receptors found in normal tissue. This makes IntelliMab-generated antibodies promising for a number of targets as well as for conjugation to a range of highly potent toxins. These would include chemotherapies as well as radio-emitters for delivery to tumors with minimal off-tumor toxicity.

"This collaboration is an important example of the utility of antibodies with superior cancer targeting for delivery of toxic payloads selectively to cancer cells. We expect new antibodies generated by the IntelliMab(TM) platform to be excellent drug candidates as well as safe delivery vehicles for use with conjugation technologies such as those developed by Dr. Reilly. We look forward to collaborating with Dr. Reilly and others in conjugating IntelliMab antibodies to toxic payloads and taking these products forward into the clinic," added Mr. Thompson.