SPECT/CT imaging, biodistribution and radiation dosimetry of a 177Lu-DOTA-integrin αvβ6 cystine knot peptide in a pancreatic cancer xenograft model

Sachindra, S.; Hellberg, T.; Exner, S.; Prasad, S.; Beindorff, N.; Rogalla, S.; Kimura, R.; Gambhir, S. S.; Wiedenmann, B.; Groetzinger, C.

doi:10.1101/2021.03.23.436654

bioRxiv · 10.1101/2021.03.23.436654

SPECT/CT imaging, biodistribution and radiation dosimetry of a 177Lu-DOTA-integrin αvβ6 cystine knot peptide in a pancreatic cancer xenograft model

Sachindra, S.·Hellberg, T.·Exner, S.·Prasad, S.·Beindorff, N.·Rogalla, S.·Kimura, R.·Gambhir, S. S.·Wiedenmann, B.·Groetzinger, C.

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Abstract

IntroductionPancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive malignant neoplasms, as many cases go undetected until they reach an advanced stage. Integrin v{beta}6 is a cell surface receptor overexpressed in PDAC. Consequently, it may serve as a target for the development of probes for imaging diagnosis and radioligand therapy. Engineered cystine knottin peptides specific for integrin v{beta}6 have recently been developed showing high affinity and stability. This study aimed to evaluate an integrin v{beta}6-specific knottin molecular probe containing the therapeutic radionuclide 177Lu for targeting of PDAC. MethodsThe expression of integrin v{beta}6 in PDAC cell lines BxPC3 and Capan2 was analyzed using RT-qPCR and immunofluorescence. In vitro competition and saturation radioligand binding assays were performed to calculate the binding affinity of the DOTA-coupled tracer loaded with and without lutetium to BxPC3 and Capan2 cell lines. To evaluate tracer accumulation in the tumor and organs, SPECT/CT, biodistribution and dosimetry projections were carried out using a Capan2 xenograft tumor mouse model. ResultsRT-qPCR and immunofluorescence results showed high expression of integrin v{beta}6 in BxPC3 and Capan2 cells. A competition binding assay revealed high affinity of the tracer with IC50 values of 1.69 nM and 9.46 nM for BxPC3 and Capan2, respectively. SPECT/CT and biodistribution analysis of the conjugate 177Lu-DOTA-integrin v{beta}6 knottin demonstrated accumulation in Capan2 xenograft tumors (3.13 {+/-} 0.63 %IA/g at day 1 post injection) with kidney uptake at 19.2 {+/-} 2.5 %IA/g, declining much more rapidly than in tumors. Conclusion177Lu-DOTA-integrin v{beta}6 knottin was found to be a high-affinity tracer for PDAC tumors with considerable tumor accumulation and moderate, rapidly declining kidney uptake. These promising results warrant a preclinical treatment study to establish therapeutic efficacy.

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Sachindra, S., Hellberg, T., Exner, S., Prasad, S., Beindorff, N., Rogalla, S., Kimura, R., Gambhir, S. S., Wiedenmann, B., Groetzinger, C.. 2021-03-23. SPECT/CT imaging, biodistribution and radiation dosimetry of a 177Lu-DOTA-integrin αvβ6 cystine knot peptide in a pancreatic cancer xenograft model. https://doi.org/10.1101/2021.03.23.436654

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