Cancer immunotherapy aims to harness the antitumor potential of the immune system and translate it into effective therapies for patients. One such approach, chimeric antigen receptor (CAR) T-cell therapy, has yielded promising initial clinical results. CAR T-cell therapy employs gene transfer techniques to reprogram endogenous T cells to target a specific tumor antigen. Most of the collective experience with this treatment has involved the use of CAR T cells to target CD19, a pan–B-cell antigen expressed in most B-cell malignancies. Genetically modified T cells expressing an anti-CD19 CAR have shown promise in several clinical trials for patients with acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL), and B-cell non-Hodgkin lymphoma (NHL).[1-7] However, CAR T-cell therapy is associated with toxicities including cytokine release syndrome (CRS), a novel inflammatory process correlating with the in vivo activation and expansion of CD19 CAR T cells; neurologic effects; and B-cell aplasia.
The promise of CAR-modified T-cell therapy derives from its combined immunologic benefits; these include the specificity of a targeted antibody, the ability to expand the T-cell population in vivo for an amplified antitumor response, and the potential for long-term persistence to facilitate ongoing tumor surveillance. Given the successes of early-phase trials with anti-CD19 CAR T cells, larger studies are underway to assess the feasibility of evaluating this treatment modality across multiple centers and in larger patient cohorts. In addition, modification of CARs to target new antigens and a variety of tumor types, including solid tumors, is the focus of ongoing investigations. In this review, we will describe the mechanism of action of CAR T cells, discuss outcomes of current clinical trials, and highlight emerging directions for this exciting approach to cancer treatment.
CAR T Cells
CARs are engineered to combine an extracellular single-chain antigen-recognition domain (usually the variable regions of a specific monoclonal antibody) with one or more intracellular T-cell signaling domains. With the use of gene transfer techniques, CARs can then be introduced into normal T cells, redirecting them to target new antigens (such as CD19) in a manner independent of major histocompatibility complexes.[8,9] Transduction of T cells with CARs encoded in lentiviral or retroviral vectors results in permanent modification of the genome and thus the potential for ongoing expression of the CAR protein for the life of the T cell. The components of the CAR signaling domain are critical for maximal activation, expansion, and persistence of CAR T cells, and therefore are a key target for manipulation. The so-called “first-generation” CARs, which included only the antigen-recognition domain with an intracellular CD3ζ signaling domain, had limited clinical activity[10-12] (Figure 1). They were unable to adequately activate T cells in vivo, especially when tumor cells lacked expression of T-cell costimulatory molecules.[8,9,11,13]
Several groups have worked to improve treatment efficacy by developing “second-generation” CARs, which include a costimulatory domain typically derived from CD28 or CD137 (also known as 4-1BB), in addition to the CD3ζ domain. The strong indication from preclinical trials that second-generation CARs would have greater antitumor potency[14,15] has now been proven by the clinically significant treatment outcomes seen in patients with relapsed and refractory (R/R) CD19-positive malignancies (see Figure 1).[1-4,6] Although the optimal costimulatory domain for second-generation CARs is not known, preclinical studies suggest that 4-1BB CARs may improve in vivo expansion and persistence. In clinical studies, 4-1BB CARs have exhibited prolonged persistence when used in the treatment of patients with CLL and ALL, which may correlate with sustained remissions.[4,6,15] Investigation of third-generation CARs (which have multiple costimulatory domains) is underway to assess whether the efficacy of CAR T-cell therapy can be further improved (see Figure 1).
The anti-CD19 CAR T cells used in various clinical trials may differ in regard to the design of the CAR molecule, the method of CAR transfer into T cells, and other aspects of the CAR T-cell culture environment. The basic steps involved in the manufacture of anti-CD19 CAR T cells at the University of Pennsylvania (Penn) and in most other clinical trial programs are summarized in Figure 2. Patients undergo an apheresis procedure to collect autologous T cells. Once collected, T cells are genetically modified with the CAR construct and expanded ex vivo for clinical use. While lentiviral and retroviral vectors are the methods of gene transfer in the represented studies, other methods such as electroporation and RNA-based methods can be employed.[12,17] The type of cell culture manufacturing system used may impact the final phenotypic composition of the CAR T-cell product, yielding different clinical outcomes.[18-20] As an example, the manufacturing process at our institution uses an anti-CD3/CD28 antibody-coated magnetic bead system that results in a final product capable of memory function and persistence. Prior to anti-CD19 CAR T-cell infusion, patients typically receive chemotherapy; the goal is to induce lymphodepletion and thereby enhance CAR T-cell expansion and persistence in vivo. Lymphodepletion may have the additional benefit of tumor cytoreduction, which can potentially improve CAR T-cell treatment efficacy and minimize toxicity. Notably, however, some patients have responded to CAR T-cell therapy in the absence of prior lymphodepletion. Besides variations in the investigational product, other differences across CAR T-cell treatment protocols include the type and intensity of lymphodepletion, the timing and dose of anti-CD19 CAR T-cell infusions, and of course the target patient population and malignancy.
Clinical Outcomes of Anti-CD19 CAR T-Cell Therapy
The greatest clinical experience with CAR T cells is with targeting CD19, which is a pan–B-cell antigen expressed in the majority of B-cell malignancies, including ALL, CLL, and NHL. This ubiquitous expression of CD19 on malignant B cells, plus the limitation of off-tumor expression on healthy B cells, make CD19 an attractive target associated with limited “on-target/off-tumor” cytotoxicities.
The prognosis for adult patients with R/R B-cell ALL is poor, and almost all patients will die from their disease.[22-29] The only possible curative approach in this setting is the use of a salvage strategy, followed by allogeneic stem cell transplantation (SCT) in patients who achieve complete remission. In a retrospective review of 547 adult patients with first relapse of Philadelphia chromosome–negative ALL, no patient who had not undergone SCT was alive after 1 year, compared with 38% of patients who received SCT after initial salvage therapy. Even poorer outcomes are seen in adult patients who relapse after SCT, most of whom have chemotherapy-resistant disease with low response rates to donor leukocyte infusion. While the majority of children diagnosed with ALL respond well to traditional treatment approaches, those with primary refractory disease have a poor prognosis, with an overall survival rate of about 30% at 10 years. Children with relapsed disease are traditionally more responsive to initial attempts at salvage therapy than their adult counterparts, but relapsed ALL remains a leading cause of cancer deaths in children.[32,33] The dismal prognosis and lack of conventional treatment options for patients with R/R ALL have driven the pursuit of therapies with alternative mechanisms of action. Immunotherapeutic approaches that target ALL antigens (such as CD19, CD20, and CD22) are proving to be remarkably effective but transient in the R/R ALL population.[1,3,4,29,34-36] Outcomes using CAR T cells directed at anti-CD19 highlight the potential of an immunologic approach.
Unprecedented remission rates of 67% to 90% have been observed in adult and pediatric patients with R/R ALL treated with second-generation anti-CD19 CAR T cells (see the Table).[1,3,4,7] In our program, we reported a 90% complete response (CR) rate in 25 pediatric and 5 adult patients treated with CTL019 cells, which are anti-CD19 CAR T cells incorporating the 4-1BB costimulatory domain. Flow cytometry to assess for minimal residual disease (MRD) was negative in 22 patients, positive in 3 patients (with 0.1%, 0.09%, and 0.22% levels of MRD), and not performed in 2 patients who achieved a CR. Of interest, responders included 2 patients who were refractory to blinatumomab, an agent that uses a bispecific antibody to redirect cytotoxic T cells to eliminate B cells with its anti-CD3 and anti-CD19 arms. Eighteen of the 30 patients treated had relapsed after a prior allogeneic SCT; T cells were successfully collected and manufactured from these recipients, and no post-infusion graft-vs-host disease (GVHD) was observed. Of the 27 responding patients, 7 relapsed (6 weeks to 8.5 months after infusion) and 1 developed myelodysplastic syndrome. Three of these relapses occurred in patients with CD19-negative leukemia. Importantly, sustained remissions lasting from 2 months to more than 24 months were noted in the remaining 19 patients, 15 of whom did not receive further treatment (3 were consolidated in remission with SCT). The durable remissions observed in patients not bridged to allogeneic SCT correlated with CAR T-cell persistence and the biological correlate of ongoing CAR T-cell activity, B-cell aplasia.
Similarly high response rates have also been observed in an ALL treatment study by researchers from Memorial Sloan Kettering Cancer Center (MSKCC), using anti-CD19–directed CAR T cells containing a CD28 costimulatory domain (as opposed to the 4-1BB domain used in Penn/Children’s Hospital of Philadelphia [CHOP] protocols). Of 16 adults with R/R ALL who were treated with the regimen, 14 (88%) achieved a CR. Four patients had relapsed after allogeneic SCT, and no patient developed GVHD. Of the 16 patients treated, 7 underwent allogeneic SCT, with 2 deaths related to SCT complications and the remaining 5 patients in ongoing remission (with follow-up ranging from 2 to 24 months). The duration of CAR T-cell persistence in this study was limited to 1 to 3 months after infusion.
In a National Cancer Institute (NCI) study (ClinicalTrials.gov identifier: NCT01593696), a CR rate of 67% was observed in a phase I intent-to-treat analysis of 20 children and young adults with B-cell ALL treated with anti-CD19–directed CAR T cells containing a CD28 domain. Ten of the 14 responding patients subsequently underwent SCT. Two patients who were not consolidated with SCT developed CD19-negative relapse, similar to the Penn/CHOP reports. Three patients who did not respond to initial treatment were reinfused with CAR T cells, but they did not respond to therapy. CAR T cells did not persist beyond 68 days. Similar to the MSKCC experience described previously, no patient treated with CAR T cells after allogeneic SCT (n = 8) developed GVHD.
Recently, investigators from the Fred Hutchinson Cancer Research Center reported similar outcomes in 29 adult patients with ALL in a trial with several unique features. First, CD4-positive and CD8-positive central memory T cells were enriched. CAR T cells were manufactured separately from the CD4-positive and CD8-positive T-cell subsets; this was achieved by using an anti-CD19 CAR incorporating the CD3ζ signaling and 4-1BB costimulatory domains transduced via a retrovirus that also contained a truncated epidermal growth factor receptor (EGFR). Inclusion of this truncated EGFR allowed identification and selection of virally transduced cells. Cells were then reconstituted in a 1:1 ratio of CD4:CD8 cells for infusion. The authors reported a CR rate of 93% (86% of whom were MRD-negative). Ten of 12 patients who received cyclophosphamide or etoposide alone achieved a CR, but 7 of them subsequently relapsed. The next 17 patients received fludarabine and cyclophosphamide. They had higher peak expansion and persistence through day 28. While 94% of these patients achieved a CR, the follow-up duration was short; however, disease-free survival seemed to be improved compared with that of patients treated with cyclophosphamide alone. This suggests that, indeed, the intensity of the lymphodepletion may impact overall outcomes. This interesting approach is the first attempt at using a defined T-cell population for CAR therapy; it is hoped that future studies will identify the ideal ratio of CAR-modified T-cell subtypes, and evaluate whether or not this approach can improve outcomes, compared with trials that do not preselect T-cell populations.
Anti-CD19 CAR T-cell therapy can be used successfully as a bridge to curative allogeneic SCT. In patients who do not undergo consolidation with SCT, long-term disease control may be dependent in large part on the persistence of anti-CD19 CAR T cells, although the optimal length of persistence (months to lifelong) is unknown. An important problem (even in patients with CAR T-cell persistence) is CD19-negative relapse. Anti-CD19 CAR T cells are effective in the post-SCT setting, where it is feasible to collect and manufacture donor-derived T cells from the recipient and safely infuse anti-CD19–directed CAR T cells into the patient without triggering GVHD.[1,3,4] Multicenter studies using anti-CD19–directed CAR T cells in adult and pediatric ALL are underway or in development.
CLL and NHL
Despite a wide array of available treatment options, CLL remains incurable without an allogeneic SCT, and the prognosis is quite poor for patients with refractory or multiply relapsed disease and short progression-free intervals between treatments. Anti-CD19 CAR T cells have been used by several centers to treat patients with R/R CLL.[2,6,38] We recently reported outcomes of long-term follow-up of the first 14 patients with CLL treated at Penn using CTL019 cells. The overall response rate (ORR) in this heavily pretreated cohort was 57%, with 4 CRs and 4 partial responses (PRs). Similar to our experience with CAR T-cell immunotherapy for ALL, durable remissions have been observed that correlate with anti-CD19 CAR T-cell expansion and persistence. Remarkably, 2 of these patients with CLL completed CAR T-cell infusion more than 5 years ago, and both are in molecular remission with detectable levels of functional anti-CD19 CAR T cells. In the Penn program, we have not yet been able to identify baseline disease- or patient-related characteristics that differentiate CLL responders from nonresponders.
In an NCI-led study, researchers used anti-CD19 CAR T cells with a CD28 costimulatory domain to treat 15 patients with advanced CD19-positive B-cell malignancies. All 4 patients with CLL in the study responded to treatment, with 3 having sustained CRs lasting longer than 1 year. However, the initial experiences of MSKCC investigators using anti-CD19 CAR T cells with a CD28 costimulatory domain in patients with chemotherapy-refractory or relapsed B-cell lymphomas were more disappointing, with 0 of 7 evaluable CLL patients responding. The reasons for this lack of response are not clear but may be related to differences in the protocol (a phase I design with 3 of 7 CLL patients not undergoing lymphodepletion) or in patient selection criteria, compared with the NCI and Penn studies.
Data on the use of anti-CD19 CAR T cells as treatment for NHL are less mature. Nine patients with diffuse large B-cell lymphoma (DLBCL) or primary mediastinal B-cell lymphoma received this therapy at the NCI, with 4 achieving a CR, 2 a PR, 1 stable disease, and 2 not evaluable for response. Preliminary results describing outcomes using anti-CD19 CAR T cells in CD19-positive NHL from Penn and the University of Washington, Seattle, were presented at the 2015 American Society of Hematology Annual Meeting.[39,40] Researchers from Penn reported an ORR of 68% following treatment with CTL019 in 22 patients with heavily pretreated NHL (13 with DLBCL, 7 with follicular lymphoma, and 2 with mantle cell lymphoma). At a median follow-up of 11.7 months, the rate of progression-free survival was 62%. The group from Seattle reported their experience using an anti-CD19 CAR containing the 4-1BB costimulatory domain in 28 patients with NHL (18 with DLBCL, 6 with follicular lymphoma, and 4 with mantle cell lymphoma). A differential response was noted in 12 patients treated with cyclophosphamide as lymphodepletion, compared with 12 (of 16 evaluable) patients who received fludarabine plus cyclophosphamide as lymphodepletion. Response rates were improved in patients pretreated with fludarabine (ORR, 67% vs 50%), and correlated with higher peak levels of CAR T cells in vivo and improved CAR T-cell persistence; similar to results observed in patients with ALL, these findings suggest that the process of lymphodepletion may have an important impact on overall treatment outcomes for patients with B-cell malignancies.
1. Davila ML, Riviere I, Wang X, et al. Efficacy and toxicity management of 19-28z CAR T cell therapy in B cell acute lymphoblastic leukemia. Sci Transl Med. 2014;6:224ra25.
2. Kochenderfer JN, Dudley ME, Kassim SH, et al. Chemotherapy-refractory diffuse large B-cell lymphoma and indolent B-cell malignancies can be effectively treated with autologous T cells expressing an anti-CD19 chimeric antigen receptor. J Clin Oncol. 2015;33:540-9.
3. Lee DW, Kochenderfer JN, Stetler-Stevenson M, et al. T cells expressing CD19 chimeric antigen receptors for acute lymphoblastic leukaemia in children and young adults: a phase 1 dose-escalation trial. Lancet. 2015;385:517-28.
4. Maude SL, Frey N, Shaw PA, et al. Chimeric antigen receptor T cells for sustained remissions in leukemia. N Engl J Med. 2014;371:1507-17.
5. Garfall AL, Maus MV, Hwang WT, et al. Chimeric antigen receptor T cells against CD19 for multiple myeloma. N Engl J Med. 2015;373:1040-7.
6. Porter DL, Hwang WT, Frey NV, et al. Chimeric antigen receptor T cells persist and induce sustained remissions in relapsed refractory chronic lymphocytic leukemia. Sci Transl Med. 2015;7:303ra139.
7. Turtle CJ, Hanafi LA, Berger C, et al. CD19 CAR-T cells of defined CD4+:CD8+ composition in adult B cell ALL patients. J Clin Invest. 2016;126:2123-8.
8. June CH, Blazar BR, Riley JL. Engineering lymphocyte subsets: tools, trials and tribulations. Nat Rev Immunol. 2009;9:704-16.
9. Brentjens R, Hollyman D, Park J, et al. Enhanced in-vivo activation of adoptively transferred genetically targeted T cells following cyclophosphamide chemotherapy: initial results from a phase I clinical trial treating CLL patients with autologous CD19 targeted T cells. Blood. 2009;144:3436a.
10. Jensen MC, Popplewell L, Cooper LJ, et al. Antitransgene rejection responses contribute to attenuated persistence of adoptively transferred CD20/CD19-specific chimeric antigen receptor redirected T cells in humans. Biol Blood Marrow Transplant. 2010;16:1245-56.
11. Savoldo B, Ramos CA, Liu E, et al. CD28 costimulation improves expansion and persistence of chimeric antigen receptor-modified T cells in lymphoma patients. J Clin Invest. 2011;121:1822-6.
12. Till BG, Jensen MC, Wang J, et al. Adoptive immunotherapy for indolent non-Hodgkin lymphoma and mantle cell lymphoma using genetically modified autologous CD20-specific T cells. Blood. 2008;112:2261-71.
13. Zou W. Immunosuppressive networks in the tumour environment and their therapeutic relevance. Nat Rev Cancer. 2005;5:263-74.
14. Maher J, Brentjens RJ, Gunset G, et al. Human T-lymphocyte cytotoxicity and proliferation directed by a single chimeric TCRzeta/CD28 receptor. Nat Biotechnol. 2002;20:70-5.
15. Milone MC, Fish JD, Carpenito C, et al. Chimeric receptors containing CD137 signal transduction domains mediate enhanced survival of T cells and increased antileukemic efficacy in vivo. Mol Ther. 2009;17:1453-64.
16. Maus MV, Grupp SA, Porter DL, June CH. Antibody-modified T cells: CARs take the front seat for hematologic malignancies. Blood. 2014;123:2625-35.
17. Maude SL, Teachey DT, Porter DL, Grupp SA. CD19-targeted chimeric antigen receptor T-cell therapy for acute lymphoblastic leukemia. Blood. 2015;125:4017-23.
18. Kim JV, Latouche JB, Riviere I, Sadelain M. The ABCs of artificial antigen presentation. Nat Biotechnol. 2004;22:403-10.
19. Levine BL, Cotte J, Small CC, et al. Large-scale production of CD4+ T cells from HIV-1-infected donors after CD3/CD28 costimulation. J Hematother. 2009;7:437-48.
20. Levine BL. T lymphocyte engineering ex vivo for cancer and infectious disease. Expert Opin Biol Ther. 2008;8:475-89.
21. Klebanoff CA, Khong HT, Antony PA, et al. Sinks, suppressors and antigen presenters: how lymphodepletion enhances T cell-mediated tumor immunotherapy. Trends Immunol. 2005;26:111-7.
22. Annino L, Vegna ML, Camera A, et al. Treatment of adult acute lymphoblastic leukemia (ALL): long-term follow-up of the GIMEMA ALL 0288 randomized study. Blood. 2002;99:863-71.
23. Fielding AK, Richards SM, Chopra R, et al. Outcome of 609 adults after relapse of acute lymphoblastic leukemia (ALL); an MRC UKALL12/ECOG 2993 study. Blood. 2007;109:944-50.
24. Gokbuget N, Stanze D, Beck J, et al. Outcome of relapsed adult lymphoblastic leukemia depends on response to salvage chemotherapy, prognostic factors, and performance of stem cell transplantation. Blood. 2012;120:2032-41.
25. Kantarjian H, Thomas D, O’Brien S, et al. Long-term follow-up results of hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone (Hyper-CVAD), a dose-intensive regimen, in adult acute lymphocytic leukemia. Cancer. 2004;101:2788-801.
26. Marks DI, Paietta EM, Moorman AV, et al. T-cell acute lymphoblastic leukemia in adults: clinical features, immunophenotype, cytogenetics, and outcome from the large randomized prospective trial (UKALL XII/ECOG 2993). Blood. 2009;114:5136-45.
27. Thomas X, Boiron JM, Huguet F, et al. Outcome of treatment in adults with acute lymphoblastic leukemia: analysis of the LALA-94 trial. J Clin Oncol. 2004;22:4075-86.
28. Oriol A, Vives S, Hernandez-Rivas JM, et al. Outcome after relapse of acute lymphoblastic leukemia in adult patients included in four consecutive risk-adapted trials by the PETHEMA Study Group. Haematologica. 2010;95:589-96.
29. Frey NV, Luger SM. How I treat adults with relapsed or refractory Philadelphia chromosome-negative acute lymphoblastic leukemia. Blood. 2015;126:589-96.
30. de Lima M, Porter DL, Battiwalla M, et al. Proceedings from the National Cancer Institute’s Second International Workshop on the Biology, Prevention, and Treatment of Relapse After Hematopoietic Stem Cell Transplantation: part III. Prevention and treatment of relapse after allogeneic transplantation. Biol Blood Marrow Transplant. 2014;20:4-13.
31. Schrappe M, Hunger SP, Pui CH, et al. Outcomes after induction failure in childhood acute lymphoblastic leukemia. N Engl J Med. 2012;366:1371-81.
32. Bhojwani D, Pui CH. Relapsed childhood acute lymphoblastic leukaemia. Lancet Oncol. 2013;14:e205-e217.
33. Nguyen K, Devidas M, Cheng SC, et al. Factors influencing survival after relapse from acute lymphoblastic leukemia: a Children’s Oncology Group study. Leukemia. 2008;22:2142-50.
34. Ai J, Advani A. Current status of antibody therapy in ALL. Br J Haematol. 2015;168:471-80.
35. Kantarjian H, Thomas D, Jorgensen J, et al. Results of inotuzumab ozogamicin, a CD22 monoclonal antibody, in refractory and relapsed acute lymphocytic leukemia. Cancer. 2013;119:2728-36.
36. Topp MS, Gokbuget N, Zugmaier G, et al. Long-term follow-up of hematologic relapse-free survival in a phase 2 study of blinatumomab in patients with MRD in B-lineage ALL. Blood. 2012;120:5185-7.
37. Dreger P, Schetelig J, Andersen N, et al. Managing high-risk CLL during transition to a new treatment era: stem cell transplantation or novel agents? Blood. 2014;124:3841-9.
38. Brentjens RJ, Riviere I, Park JH, et al. Safety and persistence of adoptively transferred autologous CD19-targeted T cells in patients with relapsed or chemotherapy refractory B-cell leukemias. Blood. 2011;118:4817-28.
39. Turtle CJ, Berger C, Sommermeyer D, et al. Anti-CD19 chimeric antigen receptor-modified T cell therapy for B cell NHL and CLL: fludarabine and cyclophosphamide lymphodepletion improves in vivo expansion and persistence of CAR-T cells and clinical outcomes. Blood. 2015;126:184.
40. Schuster SJ, Svoboda J, Nasta S, et al. Sustained remissions following chimeric antigen receptor modified T cells directed against CD19 (CTL019) in patients with relapsed or refractory CD19+ lymphomas. Blood. 2015;126:183.
41. Grupp SA, Kalos M, Barrett D, et al. Chimeric antigen receptor-modified T cells for acute lymphoid leukemia. N Engl J Med. 2013;368:1509-18.
42. Cruz CR, Micklethwaite KP, Savoldo B, et al. Infusion of donor-derived CD19-redirected virus-specific T cells for B-cell malignancies relapsed after allogeneic stem cell transplant: a phase 1 study. Blood. 2013;122:2965-73.
43. Valton J, Guyot V, Marechal A, et al. A multidrug-resistant engineered CAR T cell for allogeneic combination immunotherapy. Mol Ther. 2015;23:1507-18.
44. Shah NN, Stevenson MS, Yuan CM, et al. Characterization of CD22 expression in acute lymphoblastic leukemia. Pediatr Blood Cancer. 2015;62:964-9.
45. Ramsay AG, Johnson AJ, Lee AM, et al. Chronic lymphocytic leukemia T cells show impaired immunological synapse formation that can be reversed with an immunomodulating drug. J Clin Invest. 2008;118:2427-37.
46. Riches JC, Gribben JG. Understanding the immunodeficiency in chronic lymphocytic leukemia: potential clinical implications. Hematol Oncol Clin North Am. 2013;27:207-35.
47. Christopoulos P, Pfeifer D, Bartholome K, et al. Definition and characterization of the systemic T-cell dysregulation in untreated indolent B-cell lymphoma and very early CLL. Blood. 2011;117:3836-46.
48. Fraietta JA, Beckwith KA, Patel PR, et al. Ibrutinib enhances chimeric antigen receptor T-cell engraftment and efficacy in leukemia. Blood. 2016;127:1117-27.
49. Kakarla S, Gottschalk S. CAR T cells for solid tumors: armed and ready to go? Cancer J. 2014;20:151-5.
50. Gill S, Maus MV, Porter DL. Chimeric antigen receptor T cell therapy: 25 years in the making. Blood Rev. 2016;30:157-67.
51. Johnson LA, Scholler J, Ohkuri T, et al. Rational development and characterization of humanized anti-EGFR variant III chimeric antigen receptor T cells for glioblastoma. Sci Transl Med. 2015;7:275ra22.
52. Maus MV, Haas AR, Beatty GL, et al. T cells expressing chimeric antigen receptors can cause anaphylaxis in humans. Cancer Immunol Res. 2013;1:26-31.
53. Robbins PF, Morgan RA, Feldman SA, et al. Tumor regression in patients with metastatic synovial cell sarcoma and melanoma using genetically engineered lymphocytes reactive with NY-ESO-1. J Clin Oncol. 2011;29:917-24.
54. Morgan RA, Yang JC, Kitano M, et al. Case report of a serious adverse event following the administration of T cells transduced with a chimeric antigen receptor recognizing ERBB2. Mol Ther. 2010;18:843-51.
55. Kloss CC, Condomines M, Cartellieri M, et al. Combinatorial antigen recognition with balanced signaling promotes selective tumor eradication by engineered T cells. Nat Biotechnol. 2013;31:71-5.
56. Hoyos V, Savoldo B, Quintarelli C, et al. Engineering CD19-specific T lymphocytes with interleukin-15 and a suicide gene to enhance their anti-lymphoma/leukemia effects and safety. Leukemia. 2010;24:1160-70.
57. Wu CY, Roybal KT, Puchner EM, et al. Remote control of therapeutic T cells through a small molecule-gated chimeric receptor. Science. 2015;350:aab4077.
58. Newick K, O’Brien S, Sun J, et al. Augmentation of CAR T cell trafficking and antitumor efficacy by blocking protein kinase A (PKA) localization. Cancer Immunol Res. 2016;4:541-51.
59. Frey NV, Porter DL. CAR T-cells merge into the fast lane of cancer care. Am J Hematol. 2016;91:146-50.