PET/CT Imaging of Head-and-Neck and Pancreatic Cancer in Humans by Targeting the "Cancer Integrin" αvβ6 with Ga-68-Trivehexin

Abstract

PurposeTo develop a new probe for the αvβ6-integrin and assess its potential for PET imaging of carcinomas.MethodsGa-68-Trivehexin was synthesized by trimerization of an optimized αvβ6-integrin selective cyclicnonapeptide on the TRAP chelator core and automated labeling with Ga-68. The tracer wascharacterized by ELISA for activities towards integrin subtypes αvβ6, αvβ8, αvβ3, and α5β1, as well asby cell binding assays on H2009 (αvβ6-positive) and MDA-MB-231 (αvβ6-negative) cells. SCID micebearing subcutaneous xenografts of the same cell lines were used for dynamic (90 min) and static(75 min p.i.) μPET imaging, as well as for biodistribution (90 min p.i.). Structure-activity-relationshipswere established by comparison with the predecessor compound Ga-68-TRAP(AvB6)3. Ga-68-Trivehexin was tested for in-human PET/CT imaging of HNSCC, parotideal adenocarcinoma, andPDAC.ResultsGa-68-Trivehexin showed a high αvβ6-integrin affinity (IC50 = 0.033 nM), selectivity over othersubtypes (IC50-based factors: αvβ8, 188; αvβ3, 82; α5β1, 667), blockable uptake in H2009 cells, andnegligible uptake in MDA-MB-231 cells. Biodistribution and preclinical PET imaging confirmed a hightarget-specific uptake in tumor and a low non-specific uptake in other organs and tissues except theexcretory organs (kidneys and urinary bladder). Preclinical PET corresponded well to in-human results,showing high and persistent uptake in metastatic PDAC and HNSCC (SUVmax = 10–13) as well as inkidneys/urine. Ga-68-Trivehexin enabled PET/CT imaging of small PDAC metastases and showed highuptake in HNSCC but not in tumor-associated inflammation.ConclusionsGa-68-Trivehexin is a valuable probe for imaging of αvβ6-integrin expression in human cancers.