Nuclear imaging is taking a new turn, with isotopes targeted todisease sites using small peptides instead of larger andpotentially more risky monoclonal antibodies, Diatech Inc.reported Wednesday at the Society of Nuclear Medicine's 40thAnnual Meeting in Toronto.

The Londonderry, N.H., radiopharmaceutical company was oneof three companies announcing biotechnology-based imagingresults at the meeting.

Diatech has funded preclinical studies at medical and academicresearch centers showing that peptide carriers accumulate indisease target sites.

"We believe that, when tagged with technetium-99m, peptideswill provide a safe, effective and inexpensive way to detectdisease and may, in some cases, replace monoclonal antibodiesas the technology of choice for nuclear medicine specialists,"said Richard Dean, Diatech's president and chief executiveofficer.

Diatech has begun Phase I/II trials with Tc-99m P215 to imageatherosclerosis. It is set to begin clinical trials with P280, whichhas shown efficacy in human and animal studies to detectblood clots in the lower leg and lung. The company also plansclinical trials this year with a peptide to detect infection.

The synthetically prepared peptides should have lowprobability of invoking an immune reaction, and should besuited for repeat use. Also, diagnostic imaging proceduresshould be rapid since background levels of the agent clearquickly.

Immunomedics Presents Results on ImmuRAID

At the same meeting, Immunomedics Inc. (NASDAQ:IMMU)reported clinical results of its infectious disease imaging agent,ImmuRAID-MN3, a technetium-99m conjugate of a monoclonalantibody fragment. The compound, in Phase III studies, seeksout infection-

fighting granulocytes that are visualized with a nuclearmedicine camera.

ImmuRAID-MN3 accurately detected inflammation in 10patients with known infections in a study at Our Lady of theLake Regional Medical Center in Baton Rouge, La., andidentified osteomyelitis and soft tissue infections with betterthan 80 percent accuracy in 20 patients with suspectedinfections studied at the University Erlangen-Nuremberg,Germany.

The agent concentrated at the infection site within about anhour of injection, and no patients developed human anti-mouseantibody (HAMA) reactions or other adverse responses,company representatives said.

Immunomedics of Morris Plains, N.J., also reported that asecond injection of its ImmuRAID-CEA in 18 colorectal cancerpatients did not produce a HAMA reaction. This agent is underreview for marketing approval in the U.S., Europe and Canada.

Cytogen Reports Safety of Imaging Agent

Cytogen Corp. of Princeton, N.J., also reported safe repeatadministration of its colorectal cancer imaging agent. In amulticenter study led by Hani Nabi of the State University ofNew York in Buffalo, OncoScint Colorectal was repeatedly givento 95 patients, with some receiving four or more infusions. Theagent detected lesions in 30 of 38 patients with known diseaseand produced HAMA responses in 34 percent of patients.

"Statistically, the overall sensitivity and adverse effect rate (2.1percent) upon repeat infusion in this study were virtuallyidentical to the sensitivity and adverse effect rate seen inearlier studies involving only single infusions of OncoScint,"Nabi said.

Cytogen (NASDAQ:CYTO) is seeking expanded FDA approval forOncoscint Colorectal to be used in repeated administrations.

-- Nancy Garcia Associate Editor

(c) 1997 American Health Consultants. All rights reserved.

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