Marie Andrée Forget

Adoptive T-cell Therapy Using Autologous Tumor-infiltrating Lymphocytes for Metastatic Melanoma: Current Status and Future Outlook

Immunotherapy using autologous T cells has emerged to be a powerful treatment option for patients with metastatic melanoma. These include the adoptive transfer of autologous tumor-infiltrating lymphocytes (TILs), T cells transduced with high-affinity T cell receptors against major tumor antigens, and T cells transduced with chimeric antigen receptors composed of hybrid immunoglobulin light chains with endodomains of T-cell signaling molecules. Among these and other options for T-cell therapy, TILs together with high-dose interleukin 2 have had the longest clinical history with multiple clinical trials in centers across the world consistently demonstrating durable clinical response rates near 50% or more. A distinct advantage of TIL therapy making it still the T-cell therapy of choice is the broad nature of the T-cell recognition against both defined and undefined tumors antigens against all possible major histocompatibility complex, rather than the single specificity and limited major histocompatibility complex coverage of the newer T cell receptors and chimeric antigen receptor transduction technologies. In the past decade, significant inroads have been made in defining the phenotypes of T cells in TIL-mediating tumor regression. CD8+ T cells are emerging to be critical, although the exact subset of CD8+ T cells exhibiting the highest clinical activity in terms of memory and effector markers is still controversial. We present a model in which both effector-memory and more differentiated effector T cells ultimately may need to cooperate to mediate long-term tumor control in responding patients. Although TIL therapy has shown great potential to treat metastatic melanoma, a number of issues have emerged that need to be addressed to bring it more into the mainstream of melanoma care. First, we have a reached the point where a pivotal phase II or phase III trial is needed in an attempt to gain regulatory approval of TILs as standard of care. Second, improvements in how we expand TILs for therapy are needed that minimize the time the T cells are in culture and improve the memory and effector characteristics of the T cells for longer persistence and enhanced anti-tumor activity in vivo. Third, there is a critical need to identify surrogate and predictive biomarkers to better select suitable patients for TIL therapy to improve response rate and duration. Overall, the outlook for TIL therapy for melanoma is very bright. We predict that TILs will indeed emerge to become an approved treatment in the upcoming years through pivotal clinical trials. Moreover, new approaches combining TILs with targeted signaling pathway drugs, such as mutant B-RAF inhibitors, and synergistic immunomodulatory interventions enhancing T-cell costimulation and preventing negative regulation should further increase therapeutic efficacy and durable complete response rates.

Phase I trials using Sleeping Beauty to generate CD19-specific CAR T cells

BACKGROUND T cells expressing antigen-specific chimeric antigen receptors (CARs) improve outcomes for CD19-expressing B cell malignancies. We evaluated a human application of T cells that were genetically modified using the Sleeping Beauty (SB) transposon/transposase system to express a CD19-specific CAR. METHODS T cells were genetically modified using DNA plasmids from the SB platform to stably express a second-generation CD19-specific CAR and selectively propagated ex vivo with activating and propagating cells (AaPCs) and cytokines. Twenty-six patients with advanced non-Hodgkin lymphoma and acute lymphoblastic leukemia safely underwent hematopoietic stem cell transplantation (HSCT) and infusion of CAR T cells as adjuvant therapy in the autologous (n = 7) or allogeneic settings (n = 19). RESULTS SB-mediated genetic transposition and stimulation resulted in 2,200- to 2,500-fold ex vivo expansion of genetically modified T cells, with 84% CAR expression, and without integration hotspots. Following autologous HSCT, the 30-month progression-free and overall survivals were 83% and 100%, respectively. After allogeneic HSCT, the respective 12-month rates were 53% and 63%. No acute or late toxicities and no exacerbation of graft-versus-host disease were observed. Despite a low antigen burden and unsupportive recipient cytokine environment, CAR T cells persisted for an average of 201 days for autologous recipients and 51 days for allogeneic recipients. CONCLUSIONS CD19-specific CAR T cells generated with SB and AaPC platforms were safe, and may provide additional cancer control as planned infusions after HSCT. These results support further clinical development of this nonviral gene therapy approach. TRIAL REGISTRATION Autologous, NCT00968760; allogeneic, NCT01497184; long-term follow-up, NCT01492036. FUNDING National Cancer Institute, private foundations, and institutional funds. Please see Acknowledgments for details.

Tethered IL-15 augments antitumor activity and promotes a stem-cell memory subset in tumor-specific T cells

Significance We describe an approach based on cytokine therapeutics to enhance the persistence and effectiveness of T-cell–based immunotherapies using chimeric antigen receptors (CARs). This strategy is effective without the use of high-dose exogenous cytokines that are typically associated with toxicities. Moreover, we report that the persistence of the least differentiated memory T cell, the T-memory stem cell, was promoted by signaling induced by a membrane-bound chimeric IL-15 cytokine-fusion molecule. These findings may contribute to improving the safety and therapeutic efficacy of CAR-based immunotherapies of patients with advanced cancer. Adoptive immunotherapy retargeting T cells to CD19 via a chimeric antigen receptor (CAR) is an investigational treatment capable of inducing complete tumor regression of B-cell malignancies when there is sustained survival of infused cells. T-memory stem cells (TSCM) retain superior potential for long-lived persistence, but challenges exist in manufacturing this T-cell subset because they are rare among circulating lymphocytes. We report a clinically relevant approach to generating CAR+ T cells with preserved TSCM potential using the Sleeping Beauty platform. Because IL-15 is fundamental to T-cell memory, we incorporated its costimulatory properties by coexpressing CAR with a membrane-bound chimeric IL-15 (mbIL15). The mbIL15-CAR T cells signaled through signal transducer and activator of transcription 5 to yield improved T-cell persistence independent of CAR signaling, without apparent autonomous growth or transformation, and achieved potent rejection of CD19+ leukemia. Long-lived T cells were CD45ROnegCCR7+CD95+, phenotypically most similar to TSCM, and possessed a memory-like transcriptional profile. Overall, these results demonstrate that CAR+ T cells can develop long-term persistence with a memory stem-cell phenotype sustained by signaling through mbIL15. This observation warrants evaluation in clinical trials.

Human activated T lymphocytes modulate IDO expression in tumors through Th1/Th2 balance.

Previous cancer vaccination approaches have shown some efficiency in generating measurable immune responses, but they have rarely led to tumor regression. It is therefore possible that tumors emerge with the capacity to down-regulate immune counterparts, through the local production of immunosuppressive molecules, such as IDO. Although it is known that IDO exerts suppressive effects on T cell functions, the mechanisms of IDO regulation in tumor cells remain to be characterized. Here, we demonstrate that activated T cells can induce functional IDO expression in breast and kidney tumor cell lines, and that this is partly attributable to IFN-γ. Moreover, we found that IL-13, a Th2 cytokine, has a negative modulatory effect on IDO expression. Furthermore, we report IDO expression in the majority of breast and kidney carcinoma samples, with infiltration of activated Th1-polarized T cells in human tumors. These findings demonstrate complex control of immune activity within tumors. Future immune therapeutic interventions should thus include strategies to counteract these negative mechanisms.

Novel algorithmic approach predicts tumor mutation load and correlates with immunotherapy clinical outcomes using a defined gene mutation set

BackgroundWhile clinical outcomes following immunotherapy have shown an association with tumor mutation load using whole exome sequencing (WES), its clinical applicability is currently limited by cost and bioinformatics requirements.MethodsWe developed a method to accurately derive the predicted total mutation load (PTML) within individual tumors from a small set of genes that can be used in clinical next generation sequencing (NGS) panels. PTML was derived from the actual total mutation load (ATML) of 575 distinct melanoma and lung cancer samples and validated using independent melanoma (n = 312) and lung cancer (n = 217) cohorts. The correlation of PTML status with clinical outcome, following distinct immunotherapies, was assessed using the Kaplan–Meier method.ResultsPTML (derived from 170 genes) was highly correlated with ATML in cutaneous melanoma and lung adenocarcinoma validation cohorts (R2 = 0.73 and R2 = 0.82, respectively). PTML was strongly associated with clinical outcome to ipilimumab (anti-CTLA-4, three cohorts) and adoptive T-cell therapy (1 cohort) clinical outcome in melanoma. Clinical benefit from pembrolizumab (anti-PD-1) in lung cancer was also shown to significantly correlate with PTML status (log rank P value < 0.05 in all cohorts).ConclusionsThe approach of using small NGS gene panels, already applied to guide employment of targeted therapies, may have utility in the personalized use of immunotherapy in cancer.

Exploiting the neoantigen landscape for immunotherapy of pancreatic ductal adenocarcinoma

Immunotherapy approaches for pancreatic ductal adenocarcinoma (PDAC) have met with limited success. It has been postulated that a low mutation load may lead to a paucity of T cells within the tumor microenvironment (TME). However, it is also possible that while neoantigens are present, an effective immune response cannot be generated due to an immune suppressive TME. To discern whether targetable neoantigens exist in PDAC, we performed a comprehensive study using genomic profiles of 221 PDAC cases extracted from public databases. Our findings reveal that: (a) nearly all PDAC samples harbor potentially targetable neoantigens; (b) T cells are present but generally show a reduced activation signature; and (c) markers of efficient antigen presentation are associated with a reduced signature of markers characterizing cytotoxic T cells. These findings suggest that despite the presence of tumor specific neoepitopes, T cell activation is actively suppressed in PDAC. Further, we identify iNOS as a potential mediator of immune suppression that might be actionable using pharmacological avenues.

Activation and propagation of tumor-infiltrating lymphocytes on clinical-grade designer artificial antigen-presenting cells for adoptive immunotherapy of melanoma.

Purpose: Adoptive cell therapy with autologous tumor-infiltrating lymphocytes (TIL) is a therapy for metastatic melanoma with response rates of up to 50%. However, the generation of the TIL transfer product is challenging, requiring pooled allogeneic normal donor peripheral blood mononuclear cells (PBMC) used in vitro as “feeders” to support a rapid-expansion protocol. Here, we optimized a platform to propagate TIL to a clinical scale using K562 cells genetically modified to express costimulatory molecules such as CD86, CD137-ligand, and membrane-bound IL-15 to function as artificial antigen-presenting cells (aAPC) as an alternative to using PBMC feeders. Experimental Design: We used aAPC or &ggr;-irradiated PBMC feeders to propagate TIL and measured rates of expansion. The activation and differentiation state was evaluated by flow cytometry and differential gene expression analyses. Clonal diversity was assessed on the basis of the pattern of T-cell receptor usage. T-cell effector function was measured by evaluation of cytotoxic granule content and killing of target cells. Results: The aAPC propagated TIL at numbers equivalent to that found with PBMC feeders, whereas increasing the frequency of CD8+ T-cell expansion with a comparable effector-memory phenotype. mRNA profiling revealed an upregulation of genes in the Wnt and stem-cell pathways with the aAPC. The aAPC platform did not skew clonal diversity, and CD8+ T cells showed comparable antitumor function as those expanded with PBMC feeders. Conclusions: TIL can be rapidly expanded with aAPC to clinical scale generating T cells with similar phenotypic and effector profiles as with PBMC feeders. These data support the clinical application of aAPC to manufacture TIL for the treatment of melanoma.

Stimulation of Wnt/ß-Catenin Pathway in Human CD8+ T Lymphocytes from Blood and Lung Tumors Leads to a Shared Young/Memory Phenotype

Cancer can be treated by adoptive cell transfer (ACT) of T lymphocytes. However, how to optimally raise human T cells to a differentiation state allowing the best persistence in ACT is a challenge. It is possible to differentiate mouse CD8+ T cells towards stem cell-like memory (TSCM) phenotype upon TCR stimulation with Wnt/ß-catenin pathway activation. Here, we evaluated if TSCM can be obtained from human mature CD8+ T cells following TCR and Wnt/ß-catenin activation through treatment with the chemical agent 4,6-disubstituted pyrrolopyrimidine (TWS119), which inhibits the glycogen synthase kinase-3β (GSK-3β), key inhibitor of the Wnt pathway. Human CD8+ T cells isolated from peripheral blood or tumor-infiltrating lymphocytes (TIL), and treated with TWS119 gave rise to CD62L+CD45RA+ cells, indicative of early differentiated stage, also expressing CD127 which is normally found on memory cells, and CD133, an hematopoietic stem cell marker. TSCM cells raised from either TIL or blood secreted numerous inflammatory mediators, but in lower amounts than those measured without TWS119. Finally, generated TSCM CD8+ T cells expressed elevated Bcl-2 and no detectable caspase-3 activity, suggesting increased persistence. Our data support a role for Wnt/ß-catenin pathway in promoting the TSCM subset in human CD8+ T cells from TIL and the periphery, which are relevant for ACT.

Genomic and immune heterogeneity are associated with differential responses to therapy in melanoma

Appreciation for genomic and immune heterogeneity in cancer has grown though the relationship of these factors to treatment response has not been thoroughly elucidated. To better understand this, we studied a large cohort of melanoma patients treated with targeted therapy or immune checkpoint blockade (n = 60). Heterogeneity in therapeutic responses via radiologic assessment was observed in the majority of patients. Synchronous melanoma metastases were analyzed via deep genomic and immune profiling, and revealed substantial genomic and immune heterogeneity in all patients studied, with considerable diversity in T cell frequency, and few shared T cell clones (<8% on average) across the cohort. Variables related to treatment response were identified via these approaches and through novel radiomic assessment. These data yield insight into differential therapeutic responses to targeted therapy and immune checkpoint blockade in melanoma, and have key translational implications in the age of precision medicine.Melanoma: Tumor differences within a patient may explain heterogeneous responsesPatients with metastatic melanoma display molecular and immune differences across tumor sites associated with differential drug responses. A team led by Jennifer Wargo from the University of Texas MD Anderson Cancer Center, Houston, USA, studied the radiological responses of 60 patients with metastatic melanoma, half of whom received targeted drug therapy and half of whom received an immune checkpoint inhibitor. The majority (83%) showed differences in responses across metastases. The group then profiled tumors in a subset, and found molecular and immune heterogeneity in different tumors within the same patient. Heterogeneity in mutational and immune profiles within tumors from individual patients could explain differences in treatment response. Knowing this, the authors emphasize the importance of acquiring biopsies from more than one tumor site in order to best tailor therapies to the features of metastatic cancer.

TCR Repertoire Intratumor Heterogeneity in Localized Lung Adenocarcinomas: An Association with Predicted Neoantigen Heterogeneity and Postsurgical Recurrence

Genomic intratumor heterogeneity (ITH) may be associated with postsurgical relapse of localized lung adenocarcinomas. Recently, mutations, through generation of neoantigens, were shown to alter tumor immunogenicity through T-cell responses. Here, we performed sequencing of the T-cell receptor (TCR) in 45 tumor regions from 11 localized lung adenocarcinomas and observed substantial intratumor differences in T-cell density and clonality with the majority of T-cell clones restricted to individual tumor regions. TCR ITH positively correlated with predicted neoantigen ITH, suggesting that spatial differences in the T-cell repertoire may be driven by distinct neoantigens in different tumor regions. Finally, a higher degree of TCR ITH was associated with an increased risk of postsurgical relapse and shorter disease-free survival, suggesting a potential clinical significance of T-cell repertoire heterogeneity.Significance: The present study provides insights into the ITH of the T-cell repertoire in localized lung adenocarcinomas and its potential biological and clinical impact. The results suggest that T-cell repertoire ITH may be tightly associated to genomic ITH and disease relapse. Cancer Discov; 7(10); 1088-97. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 1047.