Eva J Razumienko1, Jason C Chen1, Zhongli Cai1, Conrad Chan1, Raymond M Reilly2. 1. Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario, Canada. 2. Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario, Canada Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada Toronto General Research Institute, Toronto, Ontario, Canada; and Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada raymond.reilly@utoronto.ca.
Abstract
UNLABELLED: One mechanism of resistance to trastuzumab in human epidermal growth factor receptor-2 (HER2)-positive breast cancer (BC) is increased epidermal growth factor receptor (EGFR) expression. We have developed (111)In-labeled bispecific radioimmunoconjugates (bsRICs) that bind HER2 and EGFR on BC cells by linking trastuzumab Fab fragments through a polyethylene glycol (PEG24) spacer to epidermal growth factor (EGF). We hypothesized that tumors coexpressing HER2 and EGFR could be treated by dual-receptor-targeted radioimmunotherapy with these bsRICs labeled with the β-particle emitter (177)Lu or the Auger electron-emitter (111)In. METHODS: The binding of (177)Lu-DOTA-Fab-PEG24-EGF to tumor cells (MDA-MB-231, SK-OV-3, MDA-MB-231/H2N, or TrR1) coexpressing HER2 and EGFR was assessed in competition assays. The clonogenic survival of these cells was measured after exposure to (177)Lu-DOTA-Fab-PEG24-EGF or (111)In-DTPA-Fab-PEG24-EGF or to monospecific (177)Lu- or (111)In-labeled trastuzumab Fab or EGF. The tumor and normal tissue biodistribution of (177)Lu-DOTA-Fab-PEG24-EGF was studied at 48 h after injection in athymic mice bearing subcutaneous MDA-MB-231/H2N tumors. Radiation-absorbed doses to tumors and normal tissues were estimated and compared for (111)In- and (177)Lu-labeled bsRICs. The maximum injected amount of (177)Lu-DOTA-Fab-PEG24-EGF that caused no observable adverse effects (NOAEL) was identified in BALB/c mice. Athymic CD1 nu/nu mice bearing subcutaneous trastuzumab-sensitive MDA-MB-231/H2N or trastuzumab-resistant TrR1 tumors were treated with (177)Lu-DOTA-Fab-PEG24-EGF or (111)In-DTPA-Fab-PEG24-EGF at the NOAEL, or with unlabeled immunoconjugates or normal saline. Tumor growth was evaluated over a period of 49 d. RESULTS: (177)Lu-DOTA-Fab-PEG24-EGF bound specifically to HER2 and EGFR on tumor cells. Monospecific (177)Lu- and (111)In-labeled trastuzumab Fab or EGF killed tumor cells that predominantly expressed HER2 or EGFR, respectively, whereas bsRICs were cytotoxic to cells that displayed either HER2 or EGFR or both receptors. bsRICs were more effective than monospecific agents. (177)Lu-DOTA-Fab-PEG24-EGF was more cytotoxic than (111)In-DTPA-Fab-PEG24-EGF. The tumor uptake of (177)Lu-DOTA-Fab-PEG24-EGF was 2-fold greater than (177)Lu-DOTA-trastuzumab Fab or (177)Lu-DOTA-EGF. The NOAEL for (177)Lu-DOTA-Fab-PEG24-EGF was 11.1 MBq (10 μg). Trastuzumab-sensitive MDA-MB-231/H2N and trastuzumab-resistant TrR1 tumors were growth-inhibited by (177)Lu-DOTA-Fab-PEG24-EGF or (111)In-DTPA-Fab-PEG24-EGF. Unlabeled immunoconjugates had no effect on tumor growth. (177)Lu-DOTA-Fab-PEG24-EGF inhibited tumor growth more effectively than (111)In-DTPA-Fab-PEG24-EGF because of a 9.3-fold-higher radiation-absorbed dose (55.0 vs. 5.9 Gy, respectively). CONCLUSION: These results are encouraging for further development of these bsRICs for dual-receptor-targeted radioimmunotherapy of BC coexpressing HER2 and EGFR, including trastuzumab-resistant tumors.
UNLABELLED: One mechanism of resistance to trastuzumab in humanepidermal growth factor receptor-2 (HER2)-positive breast cancer (BC) is increased epidermal growth factor receptor (EGFR) expression. We have developed (111)In-labeled bispecific radioimmunoconjugates (bsRICs) that bind HER2 and EGFR on BC cells by linking trastuzumabFab fragments through a polyethylene glycol (PEG24) spacer to epidermal growth factor (EGF). We hypothesized that tumors coexpressing HER2 and EGFR could be treated by dual-receptor-targeted radioimmunotherapy with these bsRICs labeled with the β-particle emitter (177)Lu or the Auger electron-emitter (111)In. METHODS: The binding of (177)Lu-DOTA-Fab-PEG24-EGF to tumor cells (MDA-MB-231, SK-OV-3, MDA-MB-231/H2N, or TrR1) coexpressing HER2 and EGFR was assessed in competition assays. The clonogenic survival of these cells was measured after exposure to (177)Lu-DOTA-Fab-PEG24-EGF or (111)In-DTPA-Fab-PEG24-EGF or to monospecific (177)Lu- or (111)In-labeled trastuzumabFab or EGF. The tumor and normal tissue biodistribution of (177)Lu-DOTA-Fab-PEG24-EGF was studied at 48 h after injection in athymic mice bearing subcutaneous MDA-MB-231/H2N tumors. Radiation-absorbed doses to tumors and normal tissues were estimated and compared for (111)In- and (177)Lu-labeled bsRICs. The maximum injected amount of (177)Lu-DOTA-Fab-PEG24-EGF that caused no observable adverse effects (NOAEL) was identified in BALB/c mice. Athymic CD1 nu/nu mice bearing subcutaneous trastuzumab-sensitive MDA-MB-231/H2N or trastuzumab-resistant TrR1 tumors were treated with (177)Lu-DOTA-Fab-PEG24-EGF or (111)In-DTPA-Fab-PEG24-EGF at the NOAEL, or with unlabeled immunoconjugates or normal saline. Tumor growth was evaluated over a period of 49 d. RESULTS: (177)Lu-DOTA-Fab-PEG24-EGF bound specifically to HER2 and EGFR on tumor cells. Monospecific (177)Lu- and (111)In-labeled trastuzumabFab or EGF killed tumor cells that predominantly expressed HER2 or EGFR, respectively, whereas bsRICs were cytotoxic to cells that displayed either HER2 or EGFR or both receptors. bsRICs were more effective than monospecific agents. (177)Lu-DOTA-Fab-PEG24-EGF was more cytotoxic than (111)In-DTPA-Fab-PEG24-EGF. The tumor uptake of (177)Lu-DOTA-Fab-PEG24-EGF was 2-fold greater than (177)Lu-DOTA-trastuzumabFab or (177)Lu-DOTA-EGF. The NOAEL for (177)Lu-DOTA-Fab-PEG24-EGF was 11.1 MBq (10 μg). Trastuzumab-sensitive MDA-MB-231/H2N and trastuzumab-resistant TrR1 tumors were growth-inhibited by (177)Lu-DOTA-Fab-PEG24-EGF or (111)In-DTPA-Fab-PEG24-EGF. Unlabeled immunoconjugates had no effect on tumor growth. (177)Lu-DOTA-Fab-PEG24-EGF inhibited tumor growth more effectively than (111)In-DTPA-Fab-PEG24-EGF because of a 9.3-fold-higher radiation-absorbed dose (55.0 vs. 5.9 Gy, respectively). CONCLUSION: These results are encouraging for further development of these bsRICs for dual-receptor-targeted radioimmunotherapy of BC coexpressing HER2 and EGFR, including trastuzumab-resistant tumors.
Authors: Haiming Luo; Christopher G England; Shreya Goel; Stephen A Graves; Fanrong Ai; Bai Liu; Charles P Theuer; Hing C Wong; Robert J Nickles; Weibo Cai Journal: Mol Pharm Date: 2017-03-24 Impact factor: 4.939
Authors: Ekaterina Revskaya; Zewei Jiang; Alfred Morgenstern; Frank Bruchertseifer; Muctarr Sesay; Susan Walker; Steven Fuller; Michael S Lebowitz; Claudia Gravekamp; Hossein A Ghanbari; Ekaterina Dadachova Journal: Cancer Biother Radiopharm Date: 2017-03 Impact factor: 3.099