Using Targeted Radiotherapy (TRT) to Drive Anti-Tumor Immune Response to Immunotherapies

Abstract

The disclosed method of treating a malignant solid tumor in a subject includes the steps of administering to the subject an immunomodulatory dose of a radioactive phospholipid ether metal chelate, a radiohalogenated phospholipid ether, or other targeted radiotherapy (TRT) agent that is differentially retained within malignant solid tumor tissue, and either (a) performing in situ tumor vaccination in the subject by introducing into at least one of the malignant solid tumors one or more agents capable of stimulating specific immune cells within the tumor microenvironment, or (b) performing immunotherapy in the subject by systemically administering to the subject an immunostimulatory agent, such as an immune checkpoint inhibitor. In a non-limiting example, the radioactive phospholipid ether metal chelate or radiohalogenated phospholipid ether has the formula: wherein R 1 comprises a chelating agent that is chelated to a metal atom, wherein the metal atom is an alpha, beta or Auger emitting metal isotope with a half-life of greater than 6 hours and less than 30 days, or wherein R 1 comprises a radioactive halogen isotope. In one such embodiment, a is 1, n is 18, m is 0, b is 1, and R 2 is —N + (CH 3 ) 3 .

1 . A method of treating a metastatic cancer in a subject, wherein the metastatic cancer comprises a primary malignant solid tumor and one or more metastatic tumors capable of causing concomitant immune tolerance, comprising systemically administering to the subject:
 (a) an immunomodulatory dose of a targeted radiotherapy (TRT) agent that is differentially taken up by and retained within the malignant solid tumor tissue, wherein the TRT agent is a phospholipid ether metal chelate that has the formula:   
       
         
           
           
               
               
           
         
         or a salt thereof, wherein: 
         R 1  comprises a chelating agent that is chelated to a metal atom, wherein the metal atom is a metal isotope that comprises  47 Sc,  177 Lu,  166 Ho,  186 Re,  188 Re,  67 Cu,  199 Au,  105 Rh,  223 Ra,  225 Ac, 212Pb, or  227 Th; 
         a is 0 or 1; 
         Y is selected from the group consisting of —H, —OH, —COOH, —COOX, —OCOX, and —OX, wherein X is an alkyl or an arylalkyl; 
         and wherein:
 (i) m is 0, b is 1, n is an integer from 12 to 30, and R 2  is —N + Z 3 , wherein each Z is independently an alkyl or an aryl; or 
 (ii) m is 1, b is 1, n is an integer from 12 to 30, and R 2  is —N + Z 3 , wherein each Z is independently an alkyl or an aryl; or 
 (iii) m is 0, b is 1, n is 18, and R 2  is —N + Z 3 , wherein each Z is independently an alkyl or an aryl; or 
 (iv) m is 1, b is 1, n is 18, and R 2  is —N + Z 3 , wherein each Z is independently an alkyl or an aryl; and 
 
         (b) one or more immunostimulatory agents capable of stimulating specific immune cells within the tumor microenvironment; 
         whereby the concomitant immune tolerance caused by the metastatic tumors is prevented and the metastatic cancer is treated in the subject. 
       
     
     
         2 . The method of  claim 1 , wherein the one or more immunostimulatory agents are immune checkpoint inhibitors capable of targeting one or more checkpoint molecules. 
     
     
         3 . The method of  claim 2 , wherein the one or more checkpoint molecules that the checkpoint inhibitors are capable of targeting are selected from the group consisting of A2AR (adenosine A2a receptor), BTLA (B and T lymphocyte attenuator), CTLA4 (cytotoxic T lymphocyte-associated protein 4), KIR (killer cell immunoglobulin-like receptor), LAG3 (Lymphocyte Activation Gene 3), PD-1 (programmed death receptor 1), PD-L1 (programmed death ligand 1), CD40 (cluster of differentiation 40), CD27 (cluster of differentiation 27), CD28 (cluster of differentiation 28), CD137 (cluster of differentiation 137), OX40 (CD134; cluster of differentiation 134), OX40L (OX40 ligand; cluster of differentiation 252), GITR (glucocorticoid-induced tumor necrosis factor receptor-related protein), GITRL (glucocorticoid-induced tumor necrosis factor receptor-related protein ligand), ICOS (inducible T-cell costimulator), ICOSL (inducible T-cell costimulator ligand), B7H3 (CD276; cluster of differentiation 276), B7H4 (VTCN1; V-set domain-containing T-cell activation inhibitor 1), IDO (Indoleamine 2,3-dioxygenase), TIM-3 (T-cell Immunoglobulin domain and Mucin domain 3), Gal-9 (galectin-9), and VISTA (V-domain Ig suppressor of T cell activation). 
     
     
         4 . The method of  claim 2 , wherein the one or more immune checkpoint inhibitors comprise one or more anti-immune checkpoint molecule antibodies or one or more small molecule immune checkpoint inhibitors that act to block one or more immune checkpoint molecules. 
     
     
         5 . The method of  claim 4 , wherein the one or more anti-immune checkpoint molecule antibodies are selected from the group consisting of an anti-CTLA4 antibody, an anti-PD-1 antibody, an anti-PD-L1 antibody, an anti-LAG3 antibody, an anti-KIR antibody, an anti-A2AR antibody, and anti-BTLA antibody, an anti-CD40 antibody, an anti-CD27 antibody, an anti-CD28 antibody, an anti-CD137 antibody, an anti-OX40 antibody, an anti-OX40L antibody, a GITR antibody, a GITRL antibody, an ICOS antibody, an ICOSL antibody, a B7H 3  antibody, a B7H 4  antibody, an IDO antibody, a TIM-3 antibody, a Gal-9 antibody, and a VISTA antibody: or wherein the one or more small molecule immune checkpoint inhibitors that act to block one or more immune checkpoint molecules comprise a small molecule PD-L1 inhibitor. 
     
     
         6 . The method of  claim 1 , wherein the radioactive phospholipid ether metal chelate is NM600. 
     
     
         7 . The method of  claim 1 , wherein the chelating agent is selected from the group consisting of 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (D03A) and its derivatives; 1,4,7-triazacyclononane-1,4-diacetic acid (NODA) and its derivatives; 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) and its derivatives; 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and its derivatives; 1,4,7-triazacyclononane, 1-glutaric acid-4,7-diacetic acid (NODAGA) and its derivatives; 1,4,7,10-tetraazacyclodecane, 1-glutaric acid-4,7,10-triacetic acid (DOTAGA) and its derivatives; 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid (TETA) and its derivatives; 1,4,8,11-tetraazabicyclo[6.6.2]hexadecane-4,11-diacetic acid (CB-TE2A) and its derivatives; diethylene triamine pentaacetic acid (DTPA), its diester, and its derivatives; 2-cyclohexyl diethylene triamine pentaacetic acid (CHX-A″-DTPA) and its derivatives; deforoxamine (DFO) and its derivatives; 1,2-[[6-carboxypyridin-2-yl]methylamino]ethane (H 2 dedpa) and its derivatives; and DADA and its derivatives, wherein DADA comprises the structure: 
       
         
           
           
               
               
           
         
       
     
     
         8 . The method of  claim 1 , wherein each Z is independently —CH 2 CH 3  or —CH 3 . 
     
     
         9 . The method of  claim 8 , wherein each Z is —CH 3 . 
     
     
         10 . The method of  claim 1 , wherein the chelating agent chelated to the metal atom is selected from the group consisting of: 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
     
     
         11 . The method of  claim 1 , wherein the radioactive phospholipid ether metal chelate has the formula selected from the group consisting of: 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         wherein the selected compound is chelated to the metal atom. 
       
     
     
         12 . The method of  claim 1 , wherein a is 1, b is 1, m is 0, n is 18, and R 2  is —N + (CH 3 )3. 
     
     
         13 . The method of  claim 12 , wherein the radioactive phospholipid ether metal chelate is NM600 chelated to the metal atom. 
     
     
         14 . The method of  claim 13 , wherein the radioactive phospholipid ether metal chelate is  177 Lu-NM600. 
     
     
         15 . The method of  claim 13 , wherein the radioactive phospholipid ether metal chelate is  47 Sc,  166 Ho-NM600,  186 Re-NM600,  188 Re-NM600,  67 Cu-NM600,  199 Au-NM600,  105 Rh-NM600,  223 Ra-NM600,  225 Ac-NM600,  212 Pb-NM600,  227 Th-NM600. 
     
     
         16 . The method of  claim 1 , wherein the TRT agent; the immunostimulatory agent; or both; are administered intravenously. 
     
     
         17 . The method of  claim 1 , wherein the subject is a human. 
     
     
         18 . The method of  claim 1 , wherein the cancer that is treated is selected from the group consisting of melanoma, neuroblastoma, lung cancer, adrenal cancer, colon cancer, colorectal cancer, ovarian cancer, prostate cancer, liver cancer, subcutaneous cancer, squamous cell cancer of the skin or head or neck, intestinal cancer, retinoblastoma, cervical cancer, glioma, breast cancer, pancreatic cancer, soft tissue sarcoma, Ewings sarcoma, rhabdomyosarcoma, osteosarcoma, Wilms' tumor, and pediatric brain tumors. 
     
     
         19 . The method of  claim 1 , wherein the cancer is treated without administering to the subject an antibody to a tumor antigen that is not a checkpoint molecule or an anti-GD2 antibody. 
     
     
         20 . The method of  claim 1 , wherein the immunomodulatory dose of the targeted radiotherapy (TRT) agent delivers a radiation dose of from 2 Gy to 8 Gy to the metastatic tumors.