Replacing 99mTc with 111In Improves MORF/cMORF Pretargeting by Reducing Intestinal Accumulation
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To reduce accumulation in the abdomen by MORF/cMORF pretargeting, 111In was compared to 99mTc as the radiolabel.
After receiving either 99mTc (MAG3)-cMORF or 111In (DTPA)-cMORF, normal mice were imaged and killed for pharmacokinetics. Thereafter, tumored mice were pretargeted with MORF-antibody, 48 h later were given an injection of 99mTc- or 111In-cMORF, and finally were imaged repeatedly.
The cMORF biodistribution in both normal and pretargeted tumored mice was influenced by its radiolabel. While excretion of both 99mTc-cMORF and 111In-cMORF was rapid and mainly through the kidneys, about 2% of 99mTc accumulated in the intestines compared to essentially no intestinal accumulation for 111In at any time. Tumor accumulation was unchanged.
In applications of MORF/cMORF pretargeting intended to image organs deep within the abdomen such as the pancreas, radiolabeling with 111In may be superior to 99mTc.
Key wordsPretargeting Anticancer Antibodies Tumor Radioimmunotargeting
The authors are grateful to Dr Jeffery Schlom (Laboratory of Tumor Immunology and Biology, Center for Cancer Research, NCI, NIH, Bethesda, MD) for providing the CC49 hybridoma. Financial support was from the National Institute of Health and Juvenile Diabetes Research Foundation International (CA94994, CA107360, and JDRF 37-2009-7).
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