A cancer vaccine, developed by Biomira Inc., containing anadjuvant by Ribi ImmunoChem Research Inc. has stimulated animmune response in patients, according to preliminary Phase Idata.

The trial showed that the patients, whose extensivelymetastasized ovarian cancers had resisted standardchemotherapy, produced increased levels of antibodies to thecancer antigen that was used as the vaccine. Two of the 10patients in the preliminary safety trial showed some transientshrinkage of their tumors.

The trial represents the first human study showing an immuneresponse to a "clinically relevant cancer-associated antigen"generated by a synthetic carbohydrate analog of the antigen,according to the researchers reporting in the May Journal ofImmunotherapy.

The vaccine mimics an antigen expressed on many cancer cellscalled Thomsen-Friedenreich determinant. Biomira(NASDAQ:BIOMF) is continuing to refine the antigen as avaccine candidate because the patients' antibodies cross-reacted to related synthetic antigens and had less activityagainst natural antigen than the synthetic one.

The Edmonton, Alberta, company has not yet decided whichadjuvant will serve as the boosting agent for its cancervaccines, Alex McPherson, president and CEO, told BioWorld.Biomira has an agreement with researchers at the MemorialSloan-Kettering Cancer Center in New York to allow use of itscancer antigen with different adjuvants, he said.

Sloan-Kettering is testing an adjuvant developed by CambridgeBiotech Inc. (NASDAQ:CBCX) in Phase I testing of Biomira'sTheratope antigen in melanoma patients. The Worcester, Mass.,company's QS-21 adjuvant, called Stimulon, is marketed as partof a veterinary vaccine and is being evaluated as a componentof other human and animal vaccines.

The ovarian cancer tests demonstrated that the Ribi product isan "acceptable adjuvant for the generation of high titer-specificanti-carbohydrate responses in human cancer patients," saidthe investigators, including researchers at the University ofAlberta and the Tom Baker Cancer Center in Calgary.

Ribi (NASDAQ:RIBI) of Hamilton, Mont., is testing its Detoxadjuvant as part of its Melacine therapeutic vaccine in a PhaseIII trial in late-stage melanoma.

-- Roberta Friedman, Ph.D. Special to BioWorld

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