99mTc labeled VIP analog: evaluation for imaging colorectal cancer.

Area of Science:

• Nuclear Medicine
• Oncology
• Radiopharmaceutical Chemistry

Background:

• Early and reliable diagnosis of colorectal cancer remains a significant clinical challenge.
• Colorectal cancer cells exhibit high expression of Vasoactive Intestinal Peptide (VIP) receptors.

Purpose of the Study:

• To develop and evaluate a novel technetium-99m-labeled VIP analog (TP3654) as a potential imaging agent for colorectal cancer.
• To assess the biodistribution, pharmacokinetics, and safety of (99m)Tc-TP3654 in preclinical and human studies.

Main Methods:

• Synthesis of (99m)Tc-labeled TP3654, a VIP analog.
• Comparative tissue distribution studies in nude mice bearing human colorectal cancer xenografts using (99m)Tc-TP3654, (111)In-DTPA-Octreotide, and (99m)Tc-anti-CEA scan.
• Pharmacokinetic and tissue distribution studies of (99m)Tc-TP3654 in normal human volunteers.

Main Results:

• Efficient preparation of (99m)Tc-TP3654 with preserved receptor specificity and biological activity.
• In the animal model, (99m)Tc-TP3654 demonstrated a favorable tissue distribution profile compared to other agents, despite modest tumor uptake (0.21 +/- 0.07% I.D./g at 24 hr).
• Human studies revealed no adverse effects. Renal and hepatobiliary clearance occurred within 24 hours (approx. 70% and 20%, respectively). Rapid tumor uptake was observed in cancer patients, with slower hepatobiliary clearance in non-fasting volunteers.

Conclusions:

• (99m)Tc-TP3654 is a safely prepared radiotracer with potential for colorectal cancer imaging.
• Its favorable biodistribution and observed tumor uptake suggest it is a promising diagnostic agent for colorectal cancer.