ImmunoPET Predicts Response to Met-targeted Radioligand Therapy in Models of Pancreatic Cancer Resistant to Met Kinase Inhibitors

Abstract

Background: Pancreatic ductal adenocarcinoma (PDAC) has limited standard of care therapeutic options. While initially received with enthusiasm, results from targeted therapy with small molecule tyrosine kinases inhibitors (TKIs) have been mixed, in part due to poor patient selection and compensatory changes in signaling networks upon blockade of one or more kinase of tumors. Here, we demonstrate that in PDACs otherwise resistant to rational kinase inhibition, Met-directed immuno-positron emission tomography (immunoPET) can identify targets for cell-signaling independent targeted radioligand therapy (RLT). In this study, we use Met-directed immunoPET and RLT in models of human pancreatic cancer that are resistant to Met- and MEK-selective TKIs, despite over-expression of Met and KRAS-pathway activation.Methods: We assessed cell membrane Met levels in human patient samples and pancreatic ductal adenocarcinoma (PDAC) cell lines (BxPC3, Capan2, Suit2, and MIA PaCa-2) using immunofluorescence, flow cytometry and cell-surface biotinylation assays. To determine whether Met expression levels correlate with sensitivity to Met inhibition by tyrosine kinase inhibitors (TKIs), we performed cell viability studies. A Met-directed imaging agent was engineered by labeling Met-specific onartuzumab with zirconium-89 (Zr-89) and its in vivo performance was evaluated in subcutaneous and orthotopic PDAC xenograft models. To assess whether the immunoPET agent would predict for targeted RLT response, onartuzumab was then labeled with lutetium (Lu-177) as the therapeutic radionuclide to generate our [177Lu]Lu-DTPA-onartuzumab RLT agent. [177Lu]Lu-DTPA-onartuzumab was administered at 9.25MBq (250μCi)/20μg in three fractions separated by three days in mice subcutaneously engrafted with BxPC3 (high cell-membrane Met) or MIA PaCa-2 (low cell-membrane Met). Primary endpoints were tumor response and overall survival.Results: Flow cytometry and cell-surface biotinylation studies showed that cell-membrane Met was significantly more abundant in BxPC3, Capan2, and Suit2 when compared with MIA PaCa-2 pancreatic tumor cells. Crizotinib and cabozantinib, TKIs with known activity against Met and other kinases, decreased PDAC cell line viability in vitro. The TKI with the lowest IC50 for Met, capmatinib, had no activity in PDAC lines. No additive effect was detected on cell viability when Met-inhibition was combined with MEK1/2 inhibition. We observed selective tumor uptake of [89Zr]Zr-DFO-onartuzumab in mice subcutaneously and orthotopically engrafted with PDAC lines containing high cell-surface levels of Met (BxPC3, Capan2, Suit2), but not in mice engrafted with low cell-surface levels of Met (MIA PaCa-2). Significant tumor growth delay and overall survival benefit were observed in both BxPC3 and MIA PaCa-2 engrafted animals treated with RLT when compared to controls, however, the benefit was more pronounced and more durable in the BxPC3 engrafted animals treated with [177Lu]Lu-DTPA-onartuzumab RLT.Conclusions: Our findings demonstrate that while ove...

Light-Induced Radiosynthesis of 89Zr-DFO-Azepin-Onartuzumab for Imaging the Hepatocyte Growth Factor Receptor

“…(13) MetMAb has been investigated in phase III trials (14) as a treatment for non-small-cell lung cancer (NSCLC) and onartuzumab has been used for immuno-PET with 89 Zr or 76 Br radionuclides, and for radioimmunotherapy with 177 Lu. (8)(9)(10)(11) Our group has recently developed a one-pot photoradiosynthesis approach for the simultaneous conjugation and 89 Zr-radiolabeling of mAbs. (15)(16)(17)(18)(19) Here, we evaluated the photoradiosynthesis of 89 Zr-radiolabeled onartuzumab starting from fully formulated MetMAb without pre-purification of the protein or isolation of an intermediate (Figure 1).…”

Therapeutic Application of Monoclonal Antibodies in Pancreatic Cancer: Advances, Challenges and Future Opportunities

“…and Dammes & Peer for further detail [ 206 , 207 ]. Antibody-based theranostic pairs have been developed targeting a variety of antigens including carcinoembrionic antigen (CEA) [ 208 ], tissue factor [ 35 ], CUB domain containing protein 1 (CDCP1) [ 209 ] and Met [ 210 ]. For instance, Knutson and colleagues have reported the development of a theranostic monoclonal antibody specific for CEA, conjugated to paclitaxel and a PEGylated near-infrared fluorophore (DyLight™ 680-4xPEG, Thermo Fisher Scientific, #46603, Rockford, IL, USA).…”

“…Furthermore, targeting of Met by the mAb onartuzumab labelled with zirconium-89 ( 89 Zr) demonstrated tumour uptake of 89 Zr-DFO-onartuzumab in Met overexpressing subcutaneous and orthotopic pancreatic tumours by immunoPET, while the construct 177 Lu-DTPA-onartuzumab induced significant tumour growth delay and improved survival in treated animals. 89 Zr-DFO-onartuzumab was able to predict treatment response to 177 Lu-DTPA-onartuzumab [ 210 ]. Similar theranostic approaches using small molecule inhibitors, peptides or nanoparticles targeting integrin αvβ6 [ 211 ], fibroblast activation protein [ 212 , 213 ], GPC1 [ 214 ] and IGF1 receptor [ 215 ] have also been investigated in mouse models of pancreatic cancer,…”

ImmunoPET as Stoichiometric Sensor for Glypican-3 in Models of Hepatocellular Carcinoma

“…Range benchtop Orbitrap system with heated electrospray ionization source (HESI) was used to determine the number of DFO chelators coupled per antibody as previously described (11).…”

“…Accordingly, tumorselective PET imaging agents could be quite valuable in HCC. Radiolabeled tumor antigen-selective antibodies have been developed as immunoPET theranostic agents and have demonstrated success in preclinical (6)(7)(8)(9)(10)(11) and clinical studies (12)(13)(14)(15)(16)(17)(18). Conventionally, given the 3-7 day blood half-life of most full length antibodies (19), radioisotopes with corresponding physical half-lives such as Zr-89 (3.5 days) or I-124 (4.2 days) are utilized for antibody labeling.…”