One-Step Labeling of Antibodies to High Specific Activity with Actinium-225

Abstract

Provided herein is a one-step method for chelating actinium-225 to a construct comprising a chelator linked to a biomolecule, such as, an antibody or monoclonal antibody, via a bifunctional ligand in, for example, a 3-arm configuration. Also provided are methods for increasing the radiochemical yield of an actinium-225-chelant-biomolecule complex and for producing a high specific activity actinium-225 complex. The chelation is performed at a physiological temperature, about 37° C. Also provided are high specific activity actinium-225 complexes, that is, actinium-225 chelated to the chelator-biomolecule construct and pharmaceutical compositions thereof. Further provided are methods of treating a neoplastic disease or disorder with the actinium-225 complexes.

1 . A one-step chelation process for actinium-225, comprising:
 chelating, at physiological temperature of about 37° C. and a pH of about 5.8, actinium-225 to a 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) comprising a bifunctional ligand conjugated thereto in a 3-arm configuration and a monoclonal antibody covalently linked thereto in a ratio of about 10 DOTAs per monoclonal antibody to produce an actinium-225-DOTA-monoclonal antibody complex chelated at a high specific activity of about 0.7 Ci/g to about 3.5 Ci/g, wherein said monoclonal antibody is Lintuzumab, Rituximab or ESK.   
     
     
         2 . (canceled) 
     
     
         3 . The one-step chelation process of  claim 1 , wherein a radiochemical yield of said process is about 50% to about 85%. 
     
     
         4 - 5 . (canceled) 
     
     
         6 . The one-step chelation process of  claim 1 , wherein the bifunctional ligand is benzyl-isothiocyanate or N-hydroxysuccinimide. 
     
     
         7 - 27 . (canceled) 
     
     
         28 . The one-step chelation process of  claim 1 , comprising chelating the actinium-225 to DOTA that is conjugated to benzyl-isothiocyanate or N-hydroxysuccinimide in the 3-arm configuration and covalently linked to the monoclonal antibody Lintuzumab. 
     
     
         29 . The one-step chelation process of  claim 1 , comprising chelating the actinium-225 to DOTA that is conjugated to benzyl-isothiocyanate or N-hydroxysuccinimide in the 3-arm configuration and covalently linked to the monoclonal antibody Rituxumab. 
     
     
         30 . A method for increasing the radiochemical yield of an actinium-225-DOTA-monoclonal antibody complex, comprising:
 conjugating 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) to a monoclonal antibody that is Lintuzumab, Rituximab and ESK via a bifunctional ligand in a 3-arm configuration to form a DOTA-monoclonal antibody construct in a ratio of about 10 chelators per monoclonal antibody; and   chelating actinium-225 to said 3-arm DOTA-monoclonal antibody construct at a physiological temperature of about 37° C. and a pH of about 5.8 to form an actinium-225-DOTA-monoclonal antibody complex, said reaction enabling an increase in an amount of actinium-225 chelated thereto to a high specific activity of about 0.7 Ci/g to about 3.5 Ci/g, thereby increasing the radiochemical yield of the complex.   
     
     
         31 . The method of  claim 30 , wherein said radiochemical yield is about 50% to about 85%. 
     
     
         32 . The method of  claim 30 , said conjugating step comprising conjugating DOTA to the monoclonal antibody Lintuzumab via the bifunctional ligand benzyl-isothiocyanate or N-hydroxysuccinimide in the 3-arm configuration to form a DOTA-Lintuzumab construct in the ratio of about 10 chelators per monoclonal antibody. 
     
     
         33 . The method of  claim 30 , said conjugating step comprising conjugating DOTA to the monoclonal antibody Rituxumab via the bifunctional ligand benzyl-isothiocyanate or N-hydroxysuccinimide in the 3-arm configuration to form a DOTA-Rituxumab construct in the ratio of about 10 chelators per monoclonal antibody. 
     
     
         34 . The one-step chelation process of  claim 30 , wherein the bifunctional ligand is benzyl-isothiocyanate or N-hydroxysuccinimide. 
     
     
         35 . A method for producing a high specific activity actinium-225-DOTA-monoclonal antibody, comprising:
 chelating at a physiological temperature of about 37° C. and a pH of about 5.8 actinium-225 to a DOTA-monoclonal antibody construct that comprises about 10 DOTA per monoclonal antibody and a bifunctional ligand conjugating the monoclonal antibody to the DOTA in a 3-arm or a 4-arm configuration, wherein said monoclonal antibody is Lintuzumab, Rituximab or ESK and wherein said physiological temperature enables an increase in the activity incorporated onto the monoclonal antibody, thereby producing the high specific activity actinium-225 complex of about 0.7 Ci/g to about 3.5 Ci/g.   
     
     
         36 . The method of  claim 35 , wherein a radiochemical yield of said complex is about 50% to about 85%. 
     
     
         37 . The method of  claim 35 , wherein the bifunctional ligand is benzyl-isothiocyanate or N-hydroxysuccinimide, said actinium-225 chelated to a DOTA-Lintuzumab construct via the bifunctional ligand. 
     
     
         38 . The method of  claim 35 , wherein the bifunctional ligand is benzyl-isothiocyanate or N-hydroxysuccinimide, said actinium-225 chelated to a DOTA-Rituximab construct via the bifunctional ligand. 
     
     
         39 . The one-step chelation process of  claim 35 , wherein the bifunctional ligand is benzyl-isothiocyanate or N-hydroxysuccinimide. 
     
     
         40 . An actinium-225-DOTA-monoclonal antibody complex in a 4-arm configuration with the high-specific activity of about 0.7 Ci/g to about 3.5 Ci/g produced by the method of  claim 35  or a pharmaceutical composition thereof, wherein said monoclonal antibody is Lintuzumab, Rituximab or ESK. 
     
     
         41 . The actinium-225-chelant-monoclonal antibody complex of  claim 40 , comprising an actinium-225-DOTA-Lintuzumab complex. 
     
     
         42 . The actinium-225-chelant-monoclonal antibody complex of  claim 40 , comprising an actinium-225-DOTA-Rituxumab complex.