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277. Small Molecule-Regulated Antigen Recognition System for Inducible T Cell Targeting of Cancer Cells
Cancer-Immunotherapy, Cancer Vaccines I 276. Long-Term Relapse-Free Survival of Patients with Acute Myeloid Leukemia (AML) Receiving a Telomerase-Engineered Dendritic Cell Immunotherapy
Jane S. Lebkowski , Hanna J. Khoury , Robert H. Collins , William Blum4, Patrick Stiff5, Edward Wirth6, Kevin Nishimoto6, John DiPersio7 1 Asterias Biotherapeutics, Portola Valley, CA, 2Emory University, Atlanta, GA, 3UT Southwestern, Dallas, TX, 4Ohio State University, Columbus, OH, 5Loyola University, Maywood, IL, 6Asterias Biotherapeutics, Fremont, CA, 7Washington University, St Louis, MO 1
2
3
There are few treatment options for patients with intermediate and high risk AML, and remission and relapse rates are dismal especially in patients ≥60 years old. A Phase 2 clinical trial was conducted in subjects with AML to assess a dendritic cell immunotherapy (ASTVAC1) engineered to express a modified form of telomerase that is processed through both the MHC Class I and II antigen presentation pathways. AST-VAC1 was prepared from leukapheresis collections from 33 subjects and were transfected with an mRNA encoding near full length telomerase (hTERT) modified with a lysosomal sorting signal, LAMP-1, which enhances presentation to both CD4+ helper and CD8+ cytotoxic T cells. hTERT is essential for maintaining the extended proliferative lifespan of tumor cells. AML patients were enrolled if they were in complete remission (CR1 or CR2) with intermediate or high risk cytogenetics. AST-VAC1 was prepared after induction therapy and before or after completion of consolidation cycles. AST-VAC1 containing 1 x 107 cells was administered as 6 weekly followed by 6 biweekly intradermal injections. If AST-VAC1 doses were available, patients were eligible to receive additional monthly boosts. Twenty one patients (median age: 55) in complete remission (16 CR1 and 3 CR2) or early relapse (2) received at least 3 injections of AST-VAC1. Only one Grade 3 or 4 adverse event, (idiopathic thrombocytopenia), possibly related to the immunotherapy was observed. The majority of adverse events were transient including headache, fatigue, erythema and rash. The two patients who were vaccinated during early relapse progressed rapidly and did not receive the full dosing regimen of AST-VAC1. Of the 19 patients that were in CR, 13 received all 12 doses of AST-VAC1. Fifty-eight percent (11/19) developed T cell immune responses to hTERT as assessed by ELISpot analysis. Eleven of 19 patients (median follow-up 52 mos.) were in remission as of last follow-up; seven developed detectable cellular immune responses to hTERT. Of the 19 CR patients, 7 were ≥ 60 years old at the time of AST-VAC1 immunotherapy. Four of 7 patients ≥ 60 years old remained relapse free 52-59 months post ASTVAC1 immunotherapy with all four developing immune responses to hTERT. The three patients that received AST-VAC1 while in CR2 were in remission as of their last follow-up of 24, 50 and 59 months with two having hTERT immune responses. The median duration of complete remission was greater than that observed in historical controls especially for patients ≥ 60 years old where relapse-free survival at 4 years is typically 5-20%. The results suggest that immunotherapy with AST-VAC1 is safe, can stimulate immune responses to telomerase, and may extend relapse-free survival even in patients with high risk AML.
277. Small Molecule-Regulated Antigen Recognition System for Inducible T Cell Targeting of Cancer Cells
Wai-Hang Leung1, Michael Certo2, Holly Horton2, Iulia Diaconu2, Tracy VandenBerg2, Jordan Jarjour1, Alexander Astrakhan1 1 Bluebird Bio, Seattle, WA, 2Bluebird Bio, Cambridge, MA Redirecting T cells against tumors by introducing chimeric antigen receptors (CAR) has demonstrated promising clinical results in certain cancers. However, the constitutive activity of these receptors limits which antigens can be targeted with this approach and may result in persistent elimination of healthy antigen-expressing cells. Successful CAR-T targeting of CD19+ tumors, for example, produces chronic B cell aplasia and necessitates life-long intravenous immunoglobulin (IVIG) treatment. Daric is an alternative antigen targeting approach that aims to: i) minimize the long-term toxicity of CAR-T treatment; ii) allows targeting of previously inaccessible antigens; and iii) is amenable to multiplex antigen targeting and other advanced targeting designs and strategies. The Daric system separates the antigen recognition and signaling functions of a CAR into two distinct polypeptides that contain the FKPB12 and FRB dimerization domains but lack signaling activity in the absence of a dimerization agent. Addition of the FKBP12-FRB bridging drug rapamycin or a non-immunosuppressive rapamycin analogue AP21967 heterodimerizes the signaling and antigen recognition components and restores signaling competency for antigen-dependent T cell activation. Importantly, the FKB12 and FRB dimerization partners are located extracellularly, minimizing interference with endogenously expressed signaling components and eliminating the requirement for rapamycin/AP21967 cell penetrance. A range of extracellular linkers and transmembrane domains were used to design a variety of CD19-targeting Daric constructs that exhibit minimal basal activity and robust drug-dependent antigen-specific cytolytic activity and cytokine production. The CD19-specific Daric T cells exhibited comparable levels of cytokine release, proliferation and cytolytic activity compared to a CD19-targeting CAR T cells. In vitro, Daric T cells were activated at sub-nanomolar to nanomolar concentrations of rapamycin or AP21967. No differences in cellular phenotype, expansion or functional responsiveness of Daric T cells compared to CAR T cells were observed. As expected, rapamycin was immunosuppressive to CAR T cell functionality, however Daric T cells continued to produce high level of cytokines even in the presence of rapamycin. These results highlight the potential of the Daric system to target highly expressed antigens and minimize the off-tumor on-target toxicity associated with traditional CAR designs.
278. Next-Generation Non-Viral Gene Transfer to Redirect T-Cell Specificity
Harjeet Singh1, Mary Helen Huls2, Matthew J. Figliola1, Ling Zhang1, Tiejuan Mi1, Sourindra Maiti1, Gabrielle Romain3, Simon Olivares1, Shihuang Su1, Lenka V. Hurton1, Navin Varadarajan3, Laurence J. N. Cooper4, Partow Kebriaei5 1 Pediatrics, UT MD Anderson Cancer Center, Houston, TX, 2 Intrexon, Germantown, MD, 3Chemical and Biomolecular Engineering, University of Houston, Houston, TX, 4Ziopharm Oncology, Boston, MA, 5Stem Cell Transplantation and Cellular Therapy, UT MD Anderson Cancer Center, Houston, TX Non-viral gene transfer using the Sleeping Beauty (SB) transposon/ transposase system has been successfully tested in humans to express a chimeric antigen receptor (CAR) to redirect T-cell specificity to CD19. This system has been modified to (i) improve the design of the CD19-specific CAR and (ii) reduce the time in culture to 14 days. Our previous clinical trials infused T cells expressing a 2nd generation CAR (designated CD19RCD28) with an IgG4-Fc stalk that activated via chimeric CD28 and CD3ζ. To evaluate the length of extracellular
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Molecular Therapy Volume 24, Supplement 1, May 2016 Copyright © The American Society of Gene & Cell Therapy
Jane S. Lebkowski , Hanna J. Khoury , Robert H. Collins , William Blum4, Patrick Stiff5, Edward Wirth6, Kevin Nishimoto6, John DiPersio7 1 Asterias Biotherapeutics, Portola Valley, CA, 2Emory University, Atlanta, GA, 3UT Southwestern, Dallas, TX, 4Ohio State University, Columbus, OH, 5Loyola University, Maywood, IL, 6Asterias Biotherapeutics, Fremont, CA, 7Washington University, St Louis, MO 1
2
3
There are few treatment options for patients with intermediate and high risk AML, and remission and relapse rates are dismal especially in patients ≥60 years old. A Phase 2 clinical trial was conducted in subjects with AML to assess a dendritic cell immunotherapy (ASTVAC1) engineered to express a modified form of telomerase that is processed through both the MHC Class I and II antigen presentation pathways. AST-VAC1 was prepared from leukapheresis collections from 33 subjects and were transfected with an mRNA encoding near full length telomerase (hTERT) modified with a lysosomal sorting signal, LAMP-1, which enhances presentation to both CD4+ helper and CD8+ cytotoxic T cells. hTERT is essential for maintaining the extended proliferative lifespan of tumor cells. AML patients were enrolled if they were in complete remission (CR1 or CR2) with intermediate or high risk cytogenetics. AST-VAC1 was prepared after induction therapy and before or after completion of consolidation cycles. AST-VAC1 containing 1 x 107 cells was administered as 6 weekly followed by 6 biweekly intradermal injections. If AST-VAC1 doses were available, patients were eligible to receive additional monthly boosts. Twenty one patients (median age: 55) in complete remission (16 CR1 and 3 CR2) or early relapse (2) received at least 3 injections of AST-VAC1. Only one Grade 3 or 4 adverse event, (idiopathic thrombocytopenia), possibly related to the immunotherapy was observed. The majority of adverse events were transient including headache, fatigue, erythema and rash. The two patients who were vaccinated during early relapse progressed rapidly and did not receive the full dosing regimen of AST-VAC1. Of the 19 patients that were in CR, 13 received all 12 doses of AST-VAC1. Fifty-eight percent (11/19) developed T cell immune responses to hTERT as assessed by ELISpot analysis. Eleven of 19 patients (median follow-up 52 mos.) were in remission as of last follow-up; seven developed detectable cellular immune responses to hTERT. Of the 19 CR patients, 7 were ≥ 60 years old at the time of AST-VAC1 immunotherapy. Four of 7 patients ≥ 60 years old remained relapse free 52-59 months post ASTVAC1 immunotherapy with all four developing immune responses to hTERT. The three patients that received AST-VAC1 while in CR2 were in remission as of their last follow-up of 24, 50 and 59 months with two having hTERT immune responses. The median duration of complete remission was greater than that observed in historical controls especially for patients ≥ 60 years old where relapse-free survival at 4 years is typically 5-20%. The results suggest that immunotherapy with AST-VAC1 is safe, can stimulate immune responses to telomerase, and may extend relapse-free survival even in patients with high risk AML.
277. Small Molecule-Regulated Antigen Recognition System for Inducible T Cell Targeting of Cancer Cells
Wai-Hang Leung1, Michael Certo2, Holly Horton2, Iulia Diaconu2, Tracy VandenBerg2, Jordan Jarjour1, Alexander Astrakhan1 1 Bluebird Bio, Seattle, WA, 2Bluebird Bio, Cambridge, MA Redirecting T cells against tumors by introducing chimeric antigen receptors (CAR) has demonstrated promising clinical results in certain cancers. However, the constitutive activity of these receptors limits which antigens can be targeted with this approach and may result in persistent elimination of healthy antigen-expressing cells. Successful CAR-T targeting of CD19+ tumors, for example, produces chronic B cell aplasia and necessitates life-long intravenous immunoglobulin (IVIG) treatment. Daric is an alternative antigen targeting approach that aims to: i) minimize the long-term toxicity of CAR-T treatment; ii) allows targeting of previously inaccessible antigens; and iii) is amenable to multiplex antigen targeting and other advanced targeting designs and strategies. The Daric system separates the antigen recognition and signaling functions of a CAR into two distinct polypeptides that contain the FKPB12 and FRB dimerization domains but lack signaling activity in the absence of a dimerization agent. Addition of the FKBP12-FRB bridging drug rapamycin or a non-immunosuppressive rapamycin analogue AP21967 heterodimerizes the signaling and antigen recognition components and restores signaling competency for antigen-dependent T cell activation. Importantly, the FKB12 and FRB dimerization partners are located extracellularly, minimizing interference with endogenously expressed signaling components and eliminating the requirement for rapamycin/AP21967 cell penetrance. A range of extracellular linkers and transmembrane domains were used to design a variety of CD19-targeting Daric constructs that exhibit minimal basal activity and robust drug-dependent antigen-specific cytolytic activity and cytokine production. The CD19-specific Daric T cells exhibited comparable levels of cytokine release, proliferation and cytolytic activity compared to a CD19-targeting CAR T cells. In vitro, Daric T cells were activated at sub-nanomolar to nanomolar concentrations of rapamycin or AP21967. No differences in cellular phenotype, expansion or functional responsiveness of Daric T cells compared to CAR T cells were observed. As expected, rapamycin was immunosuppressive to CAR T cell functionality, however Daric T cells continued to produce high level of cytokines even in the presence of rapamycin. These results highlight the potential of the Daric system to target highly expressed antigens and minimize the off-tumor on-target toxicity associated with traditional CAR designs.
278. Next-Generation Non-Viral Gene Transfer to Redirect T-Cell Specificity
Harjeet Singh1, Mary Helen Huls2, Matthew J. Figliola1, Ling Zhang1, Tiejuan Mi1, Sourindra Maiti1, Gabrielle Romain3, Simon Olivares1, Shihuang Su1, Lenka V. Hurton1, Navin Varadarajan3, Laurence J. N. Cooper4, Partow Kebriaei5 1 Pediatrics, UT MD Anderson Cancer Center, Houston, TX, 2 Intrexon, Germantown, MD, 3Chemical and Biomolecular Engineering, University of Houston, Houston, TX, 4Ziopharm Oncology, Boston, MA, 5Stem Cell Transplantation and Cellular Therapy, UT MD Anderson Cancer Center, Houston, TX Non-viral gene transfer using the Sleeping Beauty (SB) transposon/ transposase system has been successfully tested in humans to express a chimeric antigen receptor (CAR) to redirect T-cell specificity to CD19. This system has been modified to (i) improve the design of the CD19-specific CAR and (ii) reduce the time in culture to 14 days. Our previous clinical trials infused T cells expressing a 2nd generation CAR (designated CD19RCD28) with an IgG4-Fc stalk that activated via chimeric CD28 and CD3ζ. To evaluate the length of extracellular
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Molecular Therapy Volume 24, Supplement 1, May 2016 Copyright © The American Society of Gene & Cell Therapy