Cooperative Armoring of CAR and TCR T Cells by T Cell-Restricted IL15 and IL21 Universally Enhances Solid Tumor Efficacy

PURPOSE

Chimeric antigen receptor (CAR) and T-cell receptor (TCR) T-cell therapies are effective in a subset of patients with solid tumors, but new approaches are needed to universally improve patient outcomes. Here, we developed a technology to leverage the cooperative effects of IL15 and IL21, two common cytokine-receptor gamma chain family members with distinct, pleiotropic effects on T cells and other lymphocytes, to enhance the efficacy of adoptive T cells.

EXPERIMENTAL DESIGN

We designed vectors that induce the constitutive expression of either membrane-tethered IL15, IL21, or IL15/IL21. We used clinically relevant preclinical models of transgenic CARs and TCRs against pediatric and adult solid tumors to determine the effect of the membrane-tethered cytokines on engineered T cells for human administration.

RESULTS

We found that self-delivery of these cytokines by CAR or TCR T cells prevents functional exhaustion by repeated stimulation and limits the emergence of dysfunctional natural killer (NK)-like T cells. Across different preclinical murine solid tumor models, we observed enhanced regression with each individual cytokine but the greatest antitumor efficacy when T cells were armored with both.

CONCLUSIONS

The coexpression of membrane-tethered IL15 and IL21 represents a technology to enhance the resilience and function of engineered T cells against solid tumors and could be applicable to multiple therapy platforms and diseases. See related commentary by Ruffin et al., p. 1431.

CD3ζ ITAMs enable ligand discrimination and antagonism by inhibiting TCR signaling in response to low-affinity peptides

The T cell antigen receptor (TCR) contains ten immunoreceptor tyrosine-based activation motif (ITAM) signaling sequences distributed within six CD3 subunits; however, the reason for such structural complexity and multiplicity is unclear. Here we evaluated the effect of inactivating the three CD3ζ chain ITAMs on TCR signaling and T cell effector responses using a conditional 'switch' mouse model. Unexpectedly, we found that T cells expressing TCRs containing inactivated (non-signaling) CD3ζ ITAMs (6F-CD3ζ) exhibited reduced ability to discriminate between low- and high-affinity ligands, resulting in enhanced signaling and cytokine responses to low-affinity ligands because of a previously undetected inhibitory function of CD3ζ ITAMs. Also, 6F-CD3ζ TCRs were refractory to antagonism, as predicted by a new in silico adaptive kinetic proofreading model that revises the role of ITAM multiplicity in TCR signaling. Finally, T cells expressing 6F-CD3ζ displayed enhanced cytolytic activity against solid tumors expressing low-affinity ligands, identifying a new counterintuitive approach to TCR-mediated cancer immunotherapy.

Multi-tiered approach to detect autoimmune cross-reactivity of therapeutic T cell receptors

T cell receptor (TCR)-engineered T cell therapy using high-affinity TCRs is a promising treatment modality for cancer. Discovery of high-affinity TCRs especially against self-antigens can require approaches that circumvent central tolerance, which may increase the risk of cross-reactivity. Despite the potential for toxicity, no standardized approach to screen cross-reactivity has been established in the context of preclinical safety evaluation. Here, we describe a practical framework to prospectively detect clinically prohibitive cross-reactivity of therapeutic TCR candidates. Cross-reactivity screening consisted of multifaceted series of assays including assessment of p-MHC tetramer binding, cell line recognition, and reactivity against candidate peptide libraries. Peptide libraries were generated using conventional contact residue motif-guided search, amino acid substitution matrix-based search unguided by motif information, and combinatorial peptide library scan-guided search. We demonstrate the additive nature of a layered approach, which efficiently identifies unsafe cross-reactivity including one undetected by conventional motif-guided search. These findings have important implications for the safe development of TCR-based therapies.

Replication competent retrovirus testing (RCR) in the National Gene Vector Biorepository: No evidence of RCR in 1,595 post-treatment peripheral blood samples obtained from 60 clinical trials

The clinical impact of any therapy requires the product be safe and effective. Gammaretroviral vectors pose several unique risks, including inadvertent exposure to replication competent retrovirus (RCR) that can arise during vector manufacture. The US FDA has required patient monitoring for RCR, and the National Gene Vector Biorepository is an NIH resource that has assisted eligible investigators in meeting this requirement. To date, we have found no evidence of RCR in 338 pre-treatment and 1,595 post-treatment blood samples from 737 patients associated with 60 clinical trials. Most samples (75%) were obtained within 1 year of treatment, and samples as far out as 9 years after treatment were analyzed. The majority of trials (93%) were cancer immunotherapy, and 90% of the trials used vector products produced with the PG13 packaging cell line. The data presented here provide further evidence that current manufacturing methods generate RCR-free products and support the overall safety profile of retroviral gene therapy.

Engineered T cell therapy for viral and non-viral epithelial cancers

Engineered T cell therapy has shown remarkable efficacy in hematologic malignancies and has the potential for application to common epithelial cancers. Diverse T cell therapy strategies including adoptive transfer of tumor-infiltrating lymphocytes, chimeric antigen receptor (CAR)-T cells, and T cell receptor (TCR)-T cells have been studied in clinical trials. Recent research has established treatment of human papillomavirus (HPV)-associated cancers with TCR-T cells as a model for proof-of-principle studies in epithelial cancers. These studies and others have provided critical insight into mechanisms of tumor regression, therapeutic targets, treatment safety, treatment design, and barriers to curative cell therapies for common types of cancer. This perspective will review and consolidate understanding gained from clinical trials to treat viral and non-viral epithelial cancers with cell and gene therapy and will examine how past experience may guide future strategy in treatment and biomarker discovery.

Size-dependent activation of CAR-T cells

As the targets of chimeric antigen receptor (CAR)-T cells expand to a variety of cancers, autoimmune diseases, viral infections, and fibrosis, there is an increasing demand for identifying new antigens and designing new CARs that can be effectively activated. However, the rational selection of antigens and the design of CARs are limited by a lack of knowledge regarding the molecular mechanism by which CARs are activated by antigens. Here, we present data supporting a "size exclusion" model explaining how antigen signals are transmitted across the plasma membrane to activate the intracellular domains of CARs. In this model, antigen engagement with CAR results in a narrow intermembrane space that physically excludes CD45, a bulky phosphatase, out of the CAR zone, thus favoring CAR phosphorylation by kinases, which further triggers downstream pathways leading to T cell activation. Aligned with this model, increasing the size of CAR extracellular domains diminished CAR-T activation both in vitro and in a mouse lymphoma model; membrane-proximal epitopes activated CAR-Ts better than membrane-distal epitopes. Moreover, increasing the size of CD45 by antibody conjugation enhanced the activation of CARs that recognize membrane-distal epitopes. Consistently, CAR-Ts expressing CD45RABC, the larger isoform, were activated to a higher level than those expressing a smaller isoform CD45RO. Together, our work revealed that CAR-T activation depends on the size difference between the CAR-antigen pair and CD45; the size of CAR, antigen, and CD45 can thus be targets for tuning CAR-T activation.

Non-synergy of PD-1 blockade with T-cell therapy in solid tumors

Background

Cell therapy has shown promise in the treatment of certain solid tumors, but its efficacy may be limited by inhibition of therapeutic T cells by the programmed cell death protein-1 (PD-1) receptor. Clinical trials are testing cell therapy in combination with PDCD1 disruption or PD-1-axis blockade. However, preclinical data to support these approaches and to guide the treatment design are lacking.

Methods

Mechanisms of tumor regression and interaction between cell therapy and PD-1 blockade were investigated in congenic murine tumor models based on targeting established, solid tumors with T-cell receptor T cells directed against tumor-restricted, non-self antigens (ie, tumor neoantigens).

Results

In solid tumor models of cell therapy, PD-1 blockade mediated a reproducible but non-synergistic increase in tumor regression following adoptive T-cell transfer. Tumor regression was associated with increased tumor infiltration by endogenous T cells but not by transferred T cells. The effect was independent of PD-1 receptor expression by transferred T cells and was dependent on the endogenous T-cell repertoire and on tumor antigenicity. PD-1 blockade primarily induced cell state changes in endogenous tumor-antigen-specific T cells rather than transferred T cells.

Conclusions

Together, these findings support the concept that PD-1 blockade acts primarily through endogenous rather than transferred T cells to mediate a non-synergistic antitumor effect in solid tumor cell therapy. These findings have important implications for strategies to leverage PD-1 receptor disruption or blockade to enhance the efficacy of cell therapy.

A phase I trial of T-cell receptor gene therapy targeting KK-LC-1 for gastric, breast, cervical, lung and other KK-LC-1 positive epithelial cancers

TPS2678

Background: T cell receptor (TCR)-T cell therapy is an emerging cancer treatment strategy. Thus far, demonstration of clinical activity has been limited to a subset of solid tumors including melanoma, synovial cell sarcoma and HPV-associated cancer. It is estimated that metastatic epithelial cancers are responsible for approximately 90% of cancer deaths in the United States. The estimated 600,000 cancer deaths each year is driven largely by lung adeno- and squamous cell carcinoma and invasive breast cancer, which account for approximately 30% of all cancer-related deaths. Kita-Kyushu Lung Cancer Antigen 1 (KK-LC-1) is a cancer germline antigen with expression restricted to germ cells in adults and certain epithelial cancers including lung, breast, gastric and cervical. We identified a KK-LC-1 TCR from the tumor-infiltrating lymphocytes (TIL) of a patient with cervical cancer who had a complete tumor response to TIL therapy. The KK-LC-1 TCR was the most dominate clonotype in the infused TIL product and persisted in the peripheral blood following infusion, suggesting that it may have contributed to cancer regression in this patient. Methods: We are conducting a phase I cell dose escalation trial to test the safety and efficacy of KK-LC-1 TCR-T cell therapy in patients with metastatic KK-LC-1 positive epithelial cancer. Patients receive a lymphocyte depleting conditioning regimen followed by a one-time infusion of genetically engineered T cells expressing the KK-LC-1 TCR (KK-LC-1 TCR-T cells) and high-dose systemic aldesleukin. KK-LC-1 positivity is determined by RNAscope assay measuring the percentage of cancer cells expressing CT83 (gene encoding KK-LC-1) with a percentage of 25 or greater considered positive. Main inclusion criteria include HLA-A*01:01 allele, prior first-line therapy, ECOG of 0 or 1 and adequate organ and hematologic function. Main exclusion criteria include active major medical illness of the cardiovascular, respiratory or immune system, primary or secondary immunodeficiency and autoimmune disease. Participants will be entered in sequential dose levels and receive escalating doses of cells beginning at 1x108 and ending with 6x1010. Dose-limiting toxicities will be assessed during the first 30 days of cell infusion. The primary objective is to determine the maximally tolerated dose of KK-LC-1 TCR-T cells. Exploratory objectives include assessing the safety and efficacy of KK-LC-1 TCR-T cells and to conduct immunologic studies to understand and improve the administered treatment. Clinical trial information: NCT05035407.

Bintrafusp alfa, a bifunctional fusion protein targeting TGF-β and PD-L1, in patients with human papillomavirus-associated malignancies

BACKGROUND

Bintrafusp alfa is a first-in-class bifunctional fusion protein composed of the extracellular domain of transforming growth factor (TGF)-βRII (a TGF-β 'trap') fused to a human IgG1 mAb blocking programmed cell death ligand 1. This is the largest analysis of patients with advanced, pretreated human papillomavirus (HPV)-associated malignancies treated with bintrafusp alfa.

METHODS

In these phase 1 (NCT02517398) and phase 2 trials (NCT03427411), 59 patients with advanced, pretreated, checkpoint inhibitor-naive HPV-associated cancers received bintrafusp alfa intravenously every 2 weeks until progressive disease, unacceptable toxicity, or withdrawal. Primary endpoint was best overall response per Response Evaluation Criteria in Solid Tumors (RECIST) V.1.1; other endpoints included safety.

RESULTS

As of April 17, 2019 (phase 1), and October 4, 2019 (phase 2), the confirmed objective response rate per RECIST V.1.1 in the checkpoint inhibitor-naive, full-analysis population was 30.5% (95% CI, 19.2% to 43.9%; five complete responses); eight patients had stable disease (disease control rate, 44.1% (95% CI, 31.2% to 57.6%)). In addition, three patients experienced a delayed partial response after initial disease progression, for a total clinical response rate of 35.6% (95% CI, 23.6% to 49.1%). An additional patient with vulvar cancer had an unconfirmed response. Forty-nine patients (83.1%) experienced treatment-related adverse events, which were grade 3/4 in 16 patients (27.1%). No treatment-related deaths occurred.

CONCLUSION

Bintrafusp alfa showed clinical activity and manageable safety and is a promising treatment in HPV-associated cancers. These findings support further investigation of bintrafusp alfa in patients with advanced, pretreated HPV-associated cancers.

Dual PD-L1 and TGF-b blockade in patients with recurrent respiratory papillomatosis

Background

Recurrent respiratory papillomatosis (RRP) is a human papillomavirus (HPV) driven neoplastic disorder of the upper aerodigestive tract that causes significant morbidity and can lead to fatal airway obstruction. Prior clinical study demonstrated clinical benefit with the programmed death-ligand 1 (PD-L1) monoclonal antibody avelumab. Bintrafusp alfa is a bifunctional inhibitor of PD-L1 and transforming growth factor-beta (TGF-b) that has shown clinical activity in several cancer types.

Methods

We conducted a phase II clinical trial evaluating bintrafusp alfa in adults with RRP. Papilloma samples before and after treatment with bintrafusp alfa were assessed for correlates of response with multiplex immunofluorescence as well as immunological and genomic analyses. Post hoc analyses of papilloma samples before and after treatment with avelumab were assessed for comparison.

Results

Dual PD-L1/TGF-b inhibition failed to abrogate papilloma growth in most subjects and increased the frequency of clinically indicated interventions after treatment in four of eight subjects based on each subject’s own historical control. TGF-b neutralization consistently decreased pSMAD3 and p21 and increased Ki67 expression within the basal layers of papillomas, indicating that TGF-b restrained proliferation. These alterations were not observed in papillomas treated with PD-L1 blockade alone. Dual PD-L1/TGF-b inhibition did not enhance anti-HPV immunity within papillomas beyond that observed with PD-L1 blockade. Genomic alterations in TGF-b superfamily genes were infrequent in papillomas and normal mucosa but present in a significant fraction of head and neck carcinomas.

Conclusions

Intact TGF-b signaling restrains proliferation within papillomas, and the use of clinical agents that abrogate this pathway should be avoided in patients with RRP.

Trial registration numbers

NCT03707587 and NCT02859454.

Advances in Adoptive Cell Therapy for Head and Neck Cancer

This article reviews the most recent literature describing clinical advances in adoptive cell therapy for patients with head and neck cancer. Clinical trials with tumor-infiltrating lymphocyte and gene-engineered T-cell receptor T-cell therapy are highlighted.

Phase II evaluation of the triple combination of PDS0101, M9241, and bintrafusp alfa in patients with HPV 16 positive malignancies

2501

Background: There are more than 630,000 cases of HPV associated malignancies including cervical, oropharyngeal and anal cancer worldwide annually. HPV 16 is responsible for the majority of these cases. About 15-20% of HPV associated malignancies respond to PD-(L)1 inhibitors, but for the overwhelming majority of patients who progress on these immunotherapies there is no effective standard of care therapy. Preclinical studies have shown that the triple combination of PDS0101 (Versamune-HPV), a liposomal multipeptide therapeutic vaccine targeting HPV 16 E6/E7, M9241, a tumor-targeting immunocytokine composed of IL-12 heterodimers fused to a monoclonal antibody targeting free DNA in necrotic tumor regions, and bintrafusp alfa, a bifunctional fusion protein targeting TGF-β and PD-L1, resulted in maximum HPV-specific T cell responses, T cell tumor infiltration and tumor reduction as compared to any one or two of these agents alone. Methods: Fourteen pts with HPV 16+ relapsed or refractory advanced cancer were enrolled to the triple combination of PDS0101, M9241 and bintrafusp alfa (NCT04287868). Pts received bintrafusp alfa at 1200 mg flat dose i.v. every 2 weeks, M9241 at 16.8 mcg/kg s.c. every 4 weeks and PDS0101 given as two separate 0.5 ml s.c. injections every 4 weeks. Dose reductions of M9241 to 8 mcg/kg were allowed as well as skipped doses of any agent for ongoing toxicities. Results: Fourteen pts with advanced HPV 16+ cancers (5 cervical, 2 vaginal/vulvar, 4 anal, 3 oropharyngeal) were treated. 4/14 (28.6%) pts had a grade 3 treatment related toxicity including grade 3 hematuria in 2 pts with cervical ca and prior pelvic radiation and grade 3 AST/ALT elevation in 2 pts, one with anal ca and one with vaginal ca. For one patient with grade 3 AST/ALT elevation dose reduction of M9241 from 16.8 to 8 mcg/kg allowed for continued treatment with AST/ALT remaining at grade 1 or less. One additional patient had transient asymptomatic grade 4 neutropenia. No other treatment related grade 3 or greater toxicities were noted. 10/14 (71%) pts have had objective responses: 1 CR (anal ca) and 9 PRs (3 cervical, 2 vulvar/vaginal, 2 anal, 2 oropharyngeal) with 9/10 of these responses ongoing after a median 5 month of follow up. Of the 14 pts, 6 pts have checkpoint naïve disease and 8 pts have checkpoint refractory disease. 5/6 (83%) pts with checkpoint naïve disease and 5/8 (63%) pts with checkpoint refractory disease have had objective responses. Analyses of immune responses and other immune correlates are ongoing. Conclusions: Triple combination of PDS0101, M9241 and bintrafusp alfa appears to have a manageable safety profile along with early evidence of notable clinical activity for pts with both checkpoint naïve as well as checkpoint refractory HPV 16+ advanced malignancies. Clinical trial information: NCT04287868.

Enhanced efficacy and limited systemic cytokine exposure with membrane-anchored interleukin-12 T-cell therapy in murine tumor models

Background

Interleukin-12 (IL-12) is a potent, proinflammatory cytokine that holds promise for cancer immunotherapy, but its clinical use has been limited by its toxicity. To minimize systemic exposure and potential toxicity while maintaining the beneficial effects of IL-12, we developed a novel IL-12-based therapeutic system that combines tumor-specific T-cell-mediated delivery of IL-12 with membrane-restricted IL-12 localization and inducible IL-12 expression.

Methods

Therapeutic T cells targeting a tumor antigen were genetically engineered to express membrane-anchored IL-12 (aIL-12). Expression, function, and shedding of the aIL-12 molecule was assessed in vitro. Tumor treatment efficacy was assessed in vivo with T cell receptor (TCR) transgenic murine tumor models and a tumor xenograft model. Key outcomes were change in tumor size, circulating levels of IL-12 and other cytokines, and survival. Toxicity was assessed via change in body weight. Tumor growth curve measurements were compared using repeated-measures two-way analyses of variance.

Results

Retroviral gene transfer resulted in cell membrane expression of aIL-12 by transduced T cells. In each of two transgenic murine tumor models, tumor-specific T cells constitutively expressing aIL-12 demonstrated increased antitumor efficacy, low circulating IL-12 and interferon-γ, and no weight loss. Expression of aIL-12 via a NFAT-inducible promoter resulted in coordinate expression of aIL-12 with T cell activation. In an OT-I TCR transgenic murine tumor model, the NFAT-inducible aIL-12 molecule improved tumor treatment and did not result in detectable levels of IL-12 in serum or in weight loss. In a human tumor xenograft model, the NFAT-inducible aIL-12 molecule improved antitumor responses by human T cells coexpressing a tumor-specific engineered TCR. Serum IL-12 levels were undetectable with the NFAT-inducible construct in both models.

Conclusion

Expression of aIL-12 by tumor-targeting therapeutic T cells demonstrated low systemic exposure and improved efficacy. This treatment strategy may have broad applications to cellular therapy with tumor-infiltrating lymphocytes, chimeric antigen receptor T cells, and TCR T cells.

Safety and clinical activity of gene-engineered T-cell therapy targeting HPV-16 E7 for epithelial cancers

101

Background: Genetically engineered T-cell therapy has shown remarkable clinical activity in hematologic malignancies. It is not known if this type of treatment can be applied effectively to epithelial cancers, which account for 80% to 90% of human malignancies. Methods: We conducted a phase I clinical trial with a 3 + 3 dose escalation in which patients with metastatic HPV-16+ epithelial cancers were treated with a one-time infusion of genetically engineered T cells expressing a T-cell receptor targeting an HLA-A*02:01-restricted epitope of HPV-16 E7 (E7 TCR-T cells). A lymphocyte-depleting conditioning regimen was administered before cell infusion, and high-dose systemic aldesleukin was administered after cell infusion. Results: Twelve patients, previously treated with a median of 4 (range, 3 to 7) anticancer agents, were treated. The cell dose was not limited by toxicity. Six patients demonstrated objective clinical responses, which included regression of bulky tumors and complete elimination of some tumors. Responses occurred in patients with vulvar, anal, head and neck, and cervical cancer. Four patients who previously received PD-1-based therapy responded. Response duration ranged from 3 to 9 months. Sustained, high-level engraftment of E7 TCR-T cells in peripheral blood was observed (median after approximately 6 weeks, 66% of total T cells, range 1% to 88%) and correlated with cell dose but not with clinical response. Infused T cell characteristics did not correlate strongly with response. Of the 4 resistant tumors that were studied, 3 demonstrated genetic defects in HLA-A*02:01 or B2M (necessary components of the target complex) and 1 demonstrated copy loss with decreased expression of antigen presentation and interferon response molecules (i.e. TAP1, TAP2, IFNGR1, IFNGR2). Of the 3 sensitive tumors studied, 0 showed genetic defects in these molecules. Conclusions: E7 TCR-T cells demonstrated safety and clinical activity in the treatment of highly refractory metastatic HPV-16+ cancers. Treatment resistance was linked to definitive genetic defects in the targeted peptide-HLA complex and to manifold defects in antigen processing and interferon response. Clinical trial information: NCT02858310.

Cancer targeting by TCR gene-engineered T cells directed against Kita-Kyushu Lung Cancer Antigen-1

T cell receptor (TCR) gene-engineered T cells have shown promise in the treatment of melanoma and synovial cell sarcoma, but their application to epithelial cancers has been limited. The identification of novel therapeutic TCRs for the targeting of these tumors is important for the development of new treatments. Here, we describe the preclinical characterization of a TCR directed against Kita-Kyushu Lung Cancer Antigen-1 (KK-LC-1, encoded by CT83), a cancer germline antigen with frequent expression in human epithelial malignancies including gastric cancer, breast cancer, and lung cancer. Gene-engineered T cells expressing the KK-LC-1 TCR (KK-LC-1 TCR-Ts) demonstrated recognition of CT83+ tumor lines in vitro and mediated regression of established CT83+ xenograft tumors in immunodeficient mouse models. Cross-reactivity studies based on experimental determination of the recognition motifs for the target epitope did not demonstrate cross-reactivity against other human proteins. CT83 gene expression studies in 51 non-neural tissues and 24 neural tissues showed expression restricted exclusively to germ cells. CT83 was however expressed by a range of epithelial cancers, with the highest expression noted in gastric cancer. Collectively, these findings support the further investigation and clinical testing of KK-LC-1 TCR-Ts for gastric cancer and possibly other malignancies.

T-Cell Receptor Gene Therapy for Human Papillomavirus-Associated Epithelial Cancers: A First-in-Human, Phase I/II Study

PURPOSE

Genetically engineered T-cell therapy is an emerging treatment of hematologic cancers with potential utility in epithelial cancers. We investigated T-cell therapy for the treatment of metastatic human papillomavirus (HPV)–associated epithelial cancers.

METHODS

This phase I/II, single-center trial enrolled patients with metastatic HPV16-positive cancer from any primary tumor site who had received prior platinum-based therapy. Treatment consisted of autologous genetically engineered T cells expressing a T-cell receptor directed against HPV16 E6 (E6 T-cell receptor T cells), a conditioning regimen, and systemic aldesleukin.

RESULTS

Twelve patients were treated in the study. No dose-limiting toxicities were observed in the phase I portion. Two patients, both in the highest-dose cohort, experienced objective tumor responses. A patient with three lung metastases experienced complete regression of one tumor and partial regression of two tumors, which were subsequently resected; she has no evidence of disease 3 years after treatment. All patients demonstrated high levels of peripheral blood engraftment with E6 T-cell receptor T cells 1 month after treatment (median, 30%; range, 4% to 53%). One patient’s resistant tumor demonstrated a frameshift deletion in interferon gamma receptor 1, which mediates response to interferon gamma, an essential molecule for T-cell–mediated antitumor activity. Another patient’s resistant tumor demonstrated loss of HLA-A*02:01, the antigen presentation molecule required for this therapy. A tumor from a patient who responded to treatment did not demonstrate genetic defects in interferon gamma response or antigen presentation.

CONCLUSION

Engineered T cells can induce regression of epithelial cancer. Tumor resistance was observed in the context of T-cell programmed death-1 expression and defects in interferon gamma and antigen presentation pathway components. These findings have important implications for development of cellular therapy in epithelial cancers.

Safety and clinical activity of PD-L1 blockade in patients with aggressive recurrent respiratory papillomatosis

Background

Recurrent respiratory papillomatosis (RRP) is a human papillomavirus (HPV)-driven disorder that causes substantial morbidity and can lead to fatal distal airway obstruction and post-obstructive pneumonias. Patients require frequent surgical debridement of disease, and no approved systemic adjuvant therapies exist.

Methods

A phase II study was conducted to investigate the clinical activity and safety of programmed death-ligand 1 (PD-L1) blockade with avelumab in patients with RRP.

Results

Twelve patients were treated. All patients with laryngeal RRP displayed improvement in disease burden, and 5 of 9 (56%) displayed partial responses. None of 4 patients with pulmonary RRP displayed a response. Using each patient’s surgical history as their own control, patients required fewer surgical interventions after avelumab treatment (p = 0.008). A subset of partial responders developed HPV-specific reactivity in papilloma-infiltrating T-cells that correlated with reduced HPV viral load and an increased Tissue Inflammation Signature.

Conclusions

Avelumab demonstrated safety and clinical activity in patients with laryngeal RRP. Further study of immune checkpoint blockade for RRP, possibly with longer treatment duration or in combination with other immunotherapies aimed at activating antiviral immunity, is warranted.

Trial registration

NCT, number NCT02859454, registered August 9, 2016.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0603-3) contains supplementary material, which is available to authorized users.

A killer sidekick for antitumor T cells

Engineered NK cells kill myeloid-derived suppressor cells to aid CAR-T cell antitumor responses.

T cell receptors communicate by movement

Dynamic structural changes in the α chain transmembrane region convey T cell receptor signals.

A Phase II Study of Tumor-infiltrating Lymphocyte Therapy for Human Papillomavirus-associated Epithelial Cancers

PURPOSE

Cellular therapy is an emerging cancer treatment modality, but its application to epithelial cancers has been limited. This clinical trial evaluated tumor-infiltrating lymphocyte (TIL) therapy for the treatment of patients with metastatic human papillomavirus (HPV)-associated carcinomas.

PATIENTS AND METHODS

The trial was a phase II design with two cohorts, cervical cancers and noncervical cancers. Cell infusion was preceded by a lymphocyte-depleting conditioning regimen and followed by systemic high-dose aldesleukin.

RESULTS

Objective tumor responses occurred in 5 of 18 (28%) patients in the cervical cancer cohort and 2 of 11 (18%) patients in the noncervical cancer cohort. Two of the responses in cervical cancer were complete and are ongoing 67 and 53 months after treatment. Responses in the noncervical cancer cohort were in anal cancer and oropharyngeal cancer. The HPV reactivity of the infused T cells correlated with clinical response. Peripheral blood repopulation with HPV-reactive T cells also correlated with clinical response.

CONCLUSIONS

These findings support the concept that cellular therapy can mediate the regression of epithelial cancers, and they suggest the importance of predictive biomarkers and novel treatment platforms for more effective therapies.

Self-defeating CAR-Ts protect leukemic cells

Transfer of a CAR gene to a leukemic cell confers resistance to CAR-T cell therapy.

Tumor influence over immune cells

Tumor cell–intrinsic factors, unrelated to antigenicity, control immune cell infiltration and sensitivity to immunotherapy in a mouse model.

Human Papillomavirus T-Cell Cross-reactivity in Cervical Cancer: Implications for Immunotherapy Clinical Trial Design

IMPORTANCE

Clinical trials are testing vaccines that target human papillomavirus 16 (HPV-16) oncoproteins for the treatment of cervical cancer regardless of the HPV type of the tumor. For patients with HPV-18-positive cancers, this strategy relies on cross-reactivity of HPV-16-reactive T cells against the HPV-18 oncoproteins.

OBJECTIVES

To determine the prevalence of HPV-16 and HPV-18 metastatic cervical cancers in women enrolling in clinical trials at a US medical center and to assess whether HPV oncoprotein-targeting tumor-infiltrating lymphocytes (TILs) and T-cell receptors (TCRs) possess HPV-16/HPV-18 oncoprotein cross-reactivity.

DESIGN, SETTING, AND PARTICIPANTS

This study was conducted at the National Institutes of Health Clinical Center, a tertiary care research hospital in the United States. The HPV type of the tumors from 65 consecutive patients with cervical cancer who were evaluated for participation in clinical trials was determined by retrospective medical record review. Immunological assays testing HPV cross-reactivity were conducted on all available archived samples of oncoprotein-reactive TILs from HPV-positive tumors (n = 16) and on a library of previously identified TCRs (n = 10).

INTERVENTIONS

The HPV genotype of each patient's tumor was determined. The cross-reactivity of archived TILs and a library of TCRs was assessed.

MAIN OUTCOMES AND MEASURES

The main outcomes were the prevalence of each HPV genotype and the frequency of TILs or TCRs with HPV oncoprotein-T-cell cross-reactivity. Cross-reactivity was assessed by enzyme-linked immunospot assays and interferon-γ production assays.

RESULTS

The median (range) age of 65 referred patients was 44 (24-64) years. Ethnicity was recorded for 39 of 65 patients; 35 (89.7%) were white, 3 (7.7%) were Asian, and 1 (2.6%) was American Indian/Alaskan Native. Histologic tumor subtype was recorded for 41 of 65 patients; 25 (61.0%) were squamous cell carcinomas, 12 (29.3%) were adenocarcinomas, 2 (4.9%) were adenosquamous cell carcinomas, and 2 (4.9%) were neuroendocrine tumors. Thirty-nine of 65 patients (60.0%) had HPV-16-positive tumors and 21 patients (32.3%) had HPV-18-positive tumors. In the analysis of cross-reactivity, 1 of 16 oncoprotein-reactive archived TILs (9 from cervical cancers and 7 from other cancers) displayed HPV-16/HPV-18 cross-reactivity. None of the 10 oncoprotein-reactive TCRs displayed HPV-16/HPV-18 cross-reactivity.

CONCLUSIONS AND RELEVANCE

Cervical cancers that tested positive for HPV-18 were common in this study and may be common in other US clinical trial populations. Results showed that HPV-16/HPV-18 intergenotype T-cell cross-reactivity of T cells from HPV-16-positive and HPV-18-positive cancers was uncommon. These findings support clinical trial designs in which the HPV type targeted by a therapeutic vaccine is matched with the HPV type of a cancer and suggest a change is necessary in the design of active clinical trials.

Gene transfer delivers (β-globin)

Transplantation of genetically engineered hematopoietic stem cells eliminates or reduces transfusion dependence in β-thalassemia.

Engineered T cells targeting E7 mediate regression of human papillomavirus cancers in a murine model

T cell receptor (TCR) T cell therapy is a promising cancer treatment modality. However, its successful development for epithelial cancers may depend on the identification of high-avidity TCRs directed against tumor-restricted target antigens. The human papillomavirus (HPV) E7 antigen is an attractive therapeutic target that is constitutively expressed by HPV+ cancers but not by healthy tissues. It is unknown if genetically engineered TCR T cells that target E7 can mediate regression of HPV+ cancers. We identified an HPV-16 E7-specific, HLA-A*02:01-restricted TCR from a uterine cervix biopsy from a woman with cervical intraepithelial neoplasia. This TCR demonstrated high functional avidity, with CD8 coreceptor-independent tumor targeting. Human T cells transduced to express the TCR specifically recognized and killed HPV-16+ cervical and oropharyngeal cancer cell lines and mediated regression of established HPV-16+ human cervical cancer tumors in a mouse model. These findings support the therapeutic potential of this approach and established the basis for an E7 TCR gene therapy clinical trial in patients with metastatic HPV+ cancers (NCT02858310).

Cell-based molecularly targeted therapy: targeting oncoproteins with T cell receptor gene therapy

As oncogenes drive carcinogenesis and promote cancer cell survival, they are highly attractive therapeutic targets, and oncogene-targeting small molecules have achieved some clinical success. While many oncogenes are presently considered to be "druggable," tumors often acquire treatment resistance, and patients are rarely cured in response to oncogene-specific treatment. In this issue of the JCI, Veatch and colleagues describe a patient with metastatic acral melanoma who experienced a complete tumor response following infusion of tumor-infiltrating T cells that targeted multiple tumor antigens, including a BRAFV600E driver mutation. T cells genetically engineered to express an anti-BRAFV600E T cell receptor (TCR) from the patient demonstrated recognition of an epitope that spanned the BRAFV600E mutation. These findings suggest that BRAFV600E might be targeted therapeutically with adoptive transfer of anti-BRAFV600E T cells. This research supports the emerging therapeutic paradigm of targeting oncogenic drivers with T cell immunotherapy.

Can interleukin-15 keep its therapeutic promise?

The search continues for a therapeutic niche for interleukin-15 in human cancer treatment.

Enhanced clinical-scale manufacturing of TCR transduced T-cells using closed culture system modules

Background

Genetic engineering of T-cells to express specific T cell receptors (TCR) has emerged as a novel strategy to treat various malignancies. More widespread utilization of these types of therapies has been somewhat constrained by the lack of closed culture processes capable of expanding sufficient numbers of T-cells for clinical application. Here, we evaluate a process for robust clinical grade manufacturing of TCR gene engineered T-cells.

Methods

TCRs that target human papillomavirus E6 and E7 were independently tested. A 21 day process was divided into a transduction phase (7 days) and a rapid expansion phase (14 days). This process was evaluated using two healthy donor samples and four samples obtained from patients with epithelial cancers.

Results

The process resulted in ~ 2000-fold increase in viable nucleated cells and high transduction efficiencies (64–92%). At the end of culture, functional assays demonstrated that these cells were potent and specific in their ability to kill tumor cells bearing target and secrete large quantities of interferon and tumor necrosis factor. Both phases of culture were contained within closed or semi-closed modules, which include automated density gradient separation and cell culture bags for the first phase and closed GREX culture devices and wash/concentrate systems for the second phase.

Conclusion

Large-scale manufacturing using modular systems and semi-automated devices resulted in highly functional clinical-grade TCR transduced T-cells. This process is now in use in actively accruing clinical trials and the NIH Clinical Center and can be utilized at other cell therapy manufacturing sites that wish to scale-up and optimize their processing using closed systems.

Landscape of immunogenic tumor antigens in successful immunotherapy of virally induced epithelial cancer

Immunotherapy has clinical activity in certain virally associated cancers. However, the tumor antigens targeted in successful treatments remain poorly defined. We used a personalized immunogenomic approach to elucidate the global landscape of antitumor T cell responses in complete regression of human papillomavirus-associated metastatic cervical cancer after tumor-infiltrating adoptive T cell therapy. Remarkably, immunodominant T cell reactivities were directed against mutated neoantigens or a cancer germline antigen, rather than canonical viral antigens. T cells targeting viral tumor antigens did not display preferential in vivo expansion. Both viral and nonviral tumor antigen-specific T cells resided predominantly in the programmed cell death 1 (PD-1)-expressing T cell compartment, which suggests that PD-1 blockade may unleash diverse antitumor T cell reactivities. These findings suggest a new paradigm of targeting nonviral antigens in immunotherapy of virally associated cancers.

Circulating Cell-free DNA for Metastatic Cervical Cancer Detection, Genotyping, and Monitoring

Purpose: Circulating cell-free (ccf) human papillomavirus (HPV) DNA may serve as a unique tumor marker for HPV-associated malignancies, including cervical cancer. We developed a method to genotype and quantify circulating HPV DNA in patients with HPV16- or HPV18-positive metastatic cervical cancer for potential disease monitoring and treatment-related decision making.Experimental Design: In this retrospective study, HPV ccfDNA was measured in serum samples from 19 metastatic cervical cancer patients by duplex digital droplet PCR (ddPCR). Nine patients had received tumor-infiltrating lymphocyte (TIL) immunotherapy. ccfDNA data were aligned with the tumor HPV genotype, drug treatment, and clinical outcome.Results: In blinded tests, HPV ccfDNA was detected in 19 of 19 (100%) patients with HPV-positive metastatic cervical cancer but not in any of the 45 healthy blood donors. The HPV genotype harbored in the patients' tumors was correctly identified in 87 of 87 (100%) sequential patient serum samples from 9 patients who received TIL immunotherapy. In three patients who experienced objective cancer regression after TIL treatment, a transient HPV ccfDNA peak was detected 2-3 days after TIL infusion. Furthermore, persistent clearance of HPV ccfDNA was only observed in two patients who experienced complete response (CR) after TIL immunotherapy.Conclusions: HPV ccfDNA represents a promising tumor marker for noninvasive HPV genotyping and may be used in selecting patients for HPV type-specific T-cell-based immunotherapies. It may also have value in detecting antitumor activity of therapeutic agents and in the long-term follow-up of cervical cancer patients in remission. Clin Cancer Res; 23(22); 6856-62. ©2017 AACR.

A phase I/II clinical trial of E6 T-cell receptor gene therapy for human papillomavirus (HPV)-associated epithelial cancers

3009

Background: Engineered T-cell therapy has shown promise in B-cell malignancies and melanoma, but clinical investigation in epithelial cancers has been limited. Methods: We conducted a phase I/II clinical trial of T cells genetically engineered to express a T-cell receptor that targets an HLA-A*02:01-restricted epitope of E6 (E6 TCR T Cells) for patients with metastatic HPV-16+ carcinoma. The cell dose was escalated in cohorts of single patients (1 x 109, 1 x 1010, and 1-2 x 1011cells). Patients received a nonmyeloablative conditioning regimen of cyclophosphamide and fludarabine, a single infusion of E6 TCR T Cells, and systemic high-dose aldesleukin. Results: Twelve patients were treated, 9 at the highest cell dose, plus one retreatment. The cancer types were 6 cervical, 4 anal, 1 oropharyngeal, and 1 vaginal. No dose-limiting toxicity, autoimmune adverse events, or cytokine storm were observed. Two patients with anal cancer treated at the highest cell dose experienced partial tumor responses lasting 6 and 3 months after treatment. The patient with a 6-month response had complete regression of one tumor and partial regression of two tumors that were resected upon progression; she has no evidence of disease 22 months after treatment. T-cell receptor gene transfer efficiency was 45 and 51% in the responding patients, and 47-76% (median 61%) in the non-responding patients. Responding patients showed robust levels of E6 TCR T cell memory (30 and 46% of circulating T cells 1-month after treatment). Non-responding patients showed wide-ranging levels of E6 TCR T cell memory (range 4-53%, median 29%). Expression of programmed cell death protein 1 (PD-1) by circulating E6 TCR T Cells 1-month after treatment was low in all patients ( < 5%). The patient with a 6-month response had 7% E6 TCR T Cells in a resected tumor 10 months after treatment, 25% of which expressed PD-1. A patient with no response had no detectable E6 TCR T Cells in a resected tumor 3 months after treatment. Conclusions: E6 TCR T-cell therapy was safe at doses up to 2 x 1011 cells. Regression of metastatic HPV+ carcinoma occurred in two patients following treatment, suggesting that TCR T-cell therapy can mediate epithelial cancer regression. Clinical trial information: NCT02280811.

Molecular Pathways: Breaking the Epithelial Cancer Barrier for Chimeric Antigen Receptor and T-cell Receptor Gene Therapy

Adoptive transfer of T cells genetically engineered to express a tumor-targeting chimeric antigen receptor (CAR) or T-cell receptor (TCR) can mediate cancer regression in some patients. CARs are synthetic single-chain proteins that use antibody domains to target cell surface antigens. TCRs are natural heterodimeric proteins that can target intracellular antigens through recognition of peptides bound to human leukocyte antigens. CARs have shown promise in B-cell malignancies and TCRs in melanoma, but neither approach has achieved clear success in an epithelial cancer. Treatment of epithelial cancers may be particularly challenging because of a paucity of target antigens expressed by carcinomas and not by important healthy tissues. In addition, epithelial cancers may be protected by inhibitory ligands and soluble factors in the tumor microenvironment. One strategy to overcome these negative regulators is to modulate expression of T-cell genes to enhance intrinsic T-cell function. Programmable nucleases, which can suppress inhibitory genes, and inducible gene expression systems, which can enhance stimulatory genes, are entering clinical testing. Other work is delineating whether control of genes for immune checkpoint receptors (e.g.,PDCD1, CTLA4) and cytokine and TCR signaling regulators (e.g.,CBLB, CISH, IL12, IL15) can increase the antitumor activity of therapeutic T cells.

Targeting of HPV-16+ Epithelial Cancer Cells by TCR Gene Engineered T Cells Directed against E6

PURPOSE

The E6 and E7 oncoproteins of HPV-associated epithelial cancers are in principle ideal immunotherapeutic targets, but evidence that T cells specific for these antigens can recognize and kill HPV(+) tumor cells is limited. We sought to determine whether TCR gene engineered T cells directed against an HPV oncoprotein can successfully target HPV(+) tumor cells.

EXPERIMENTAL DESIGN

T-cell responses against the HPV-16 oncoproteins were investigated in a patient with an ongoing 22-month disease-free interval after her second resection of distant metastatic anal cancer. T cells genetically engineered to express an oncoprotein-specific TCR from this patient's tumor-infiltrating T cells were tested for specific reactivity against HPV(+) epithelial tumor cells.

RESULTS

We identified, from an excised metastatic anal cancer tumor, T cells that recognized an HLA-A*02:01-restricted epitope of HPV-16 E6. The frequency of the dominant T-cell clonotype from these cells was approximately 400-fold greater in the patient's tumor than in her peripheral blood. T cells genetically engineered to express the TCR from this clonotype displayed high avidity for an HLA-A*02:01-restricted epitope of HPV-16, and they showed specific recognition and killing of HPV-16(+) cervical, and head and neck cancer cell lines.

CONCLUSIONS

These findings demonstrate that HPV-16(+) tumors can be targeted by E6-specific TCR gene engineered T cells, and they provide the foundation for a novel cellular therapy directed against HPV-16(+) malignancies, including cervical, oropharyngeal, anal, vulvar, vaginal, and penile cancers.

Complete regression of metastatic cervical cancer after treatment with human papillomavirus-targeted tumor-infiltrating T cells

PURPOSE

Metastatic cervical cancer is a prototypical chemotherapy-refractory epithelial malignancy for which better treatments are needed. Adoptive T-cell therapy (ACT) is emerging as a promising cancer treatment, but its study in epithelial malignancies has been limited. This study was conducted to determine if ACT could mediate regression of metastatic cervical cancer.

PATIENTS AND METHODS

Patients enrolled onto this protocol were diagnosed with metastatic cervical cancer and had previously received platinum-based chemotherapy or chemoradiotherapy. Patients were treated with a single infusion of tumor-infiltrating T cells selected when possible for human papillomavirus (HPV) E6 and E7 reactivity (HPV-TILs). Cell infusion was preceded by lymphocyte-depleting chemotherapy and was followed by administration of aldesleukin.

RESULTS

Three of nine patients experienced objective tumor responses (two complete responses and one partial response). The two complete responses were ongoing 22 and 15 months after treatment, respectively. One partial response was 3 months in duration. The HPV reactivity of T cells in the infusion product (as measured by interferon gamma production, enzyme-linked immunospot, and CD137 upregulation assays) correlated positively with clinical response (P = .0238 for all three assays). In addition, the frequency of HPV-reactive T cells in peripheral blood 1 month after treatment was positively associated with clinical response (P = .0238).

CONCLUSION

Durable, complete regression of metastatic cervical cancer can occur after a single infusion of HPV-TILs. Exploratory studies suggest a correlation between HPV reactivity of the infusion product and clinical response. Continued investigation of this therapy is warranted.

Exploiting the curative potential of adoptive T-cell therapy for cancer

Adoptive T-cell therapy (ACT) is a potent and flexible cancer treatment modality that can induce complete, durable regression of certain human malignancies. Long-term follow-up of patients receiving tumor-infiltrating lymphocytes (TILs) for metastatic melanoma reveals a substantial subset that experienced complete, lasting tumor regression - and may be cured. Increasing evidence points to mutated gene products as the primary immunological targets of TILs from melanomas. Recent technological advances permit rapid identification of the neoepitopes resulting from these somatic gene mutations and of T cells with reactivity against these targets. Isolation and adoptive transfer of these T cells may improve TIL therapy for melanoma and permit its broader application to non-melanoma tumors. Extension of ACT to other malignancies may also be possible through antigen receptor gene engineering. Tumor regression has been observed following transfer of T cells engineered to express chimeric antigen receptors against CD19 in B-cell malignancies or a T-cell receptor against NY-ESO-1 in synovial cell sarcoma and melanoma. Herein, we review recent clinical trials of TILs and antigen receptor gene therapy for advanced cancers. We discuss lessons from this experience and consider how they might be applied to realize the full curative potential of ACT.

HPV-targeted tumor-infiltrating lymphocytes for cervical cancer

LBA3008

Background: Adoptive T-cell therapy (ACT) is a promising cancer treatment modality with potentially broad application. It is not known if ACT can mediate regression of carcinomas, the most common solid tumors in humans. We studied carcinoma of the uterine cervix, a virally induced malignancy that constitutively expresses the HPV E6 and E7 oncoproteins, as a model cancer to test if ACT can mediate regression of an epithelial malignancy. Methods: We initiated a clinical trial to treat metastatic HPV+ cancers with tumor-infiltrating lymphocytes (TIL) selected for HPV E6- and E7-reactivity (HPV-TIL). Patients from the cervical cancer cohort are reported here. HPV-TIL infusion was preceded b y non-myeloablative conditioning and followed by high-dose bolus aldesleukin. HPV-reactivity was assessed by ELISPOT, IFN-gamma production, and CD137 expression assays. Results: Nine patients were treated on the study. They received a median of 81 x 109 T cells (range 33 to 159 x 109) as a single infusion. The infused cells possessed reactivity against high-risk HPV E6 and/or E7 in 6/8 patients. The two patients with no HPV reactivity did not respond to treatment. 3/6 patients with HPV reactivity demonstrated objective tumor responses by RECIST (1 PR and 2 CR). One patient had a 39% best response. Two patients with widespread metastases had complete tumor responses that are ongoing 18 and 11 months after treatment. One patient with a complete response had a chemotherapy-refractory HPV-16+ squamous cell carcinoma and the other a chemoradiation-refractory HPV-18+ adenocarcinoma. Both patients demonstrated prolonged repopulation with HPV-reactive T cells following treatment. Increased frequencies of HPV-specific T cells were detectable after 13 months in one patient and 6 months in the other. Two patients with HPV-reactive TIL that did not respond to treatment did not display repopulation with HPV-reactive T cells. Conclusions: HPV-TIL can mediate durable, complete regression of metastatic cervical cancer. Continued investigation of HPV-TIL for cervical cancer, and possibly other HPV+ malignancies, is warranted. Cellular therapy can mediate complete regression of an epithelial malignancy. Clinical trial information: NCT01585428.

Cancer immunotherapy based on mutation-specific CD4+ T cells in a patient with epithelial cancer

Limited evidence exists that humans mount a mutation-specific T cell response to epithelial cancers. We used a whole-exomic-sequencing-based approach to demonstrate that tumor-infiltrating lymphocytes (TIL) from a patient with metastatic cholangiocarcinoma contained CD4+ T helper 1 (T(H)1) cells recognizing a mutation in erbb2 interacting protein (ERBB2IP) expressed by the cancer. After adoptive transfer of TIL containing about 25% mutation-specific polyfunctional T(H)1 cells, the patient achieved a decrease in target lesions with prolonged stabilization of disease. Upon disease progression, the patient was retreated with a >95% pure population of mutation-reactive T(H)1 cells and again experienced tumor regression. These results provide evidence that a CD4+ T cell response against a mutated antigen can be harnessed to mediate regression of a metastatic epithelial cancer.

Phenotype and function of T cells infiltrating visceral metastases from gastrointestinal cancers and melanoma: implications for adoptive cell transfer therapy

Adoptive cell transfer of tumor-infiltrating lymphocytes (TILs) can mediate cancer regression in patients with metastatic melanoma, but whether this approach can be applied to common epithelial malignancies remains unclear. In this study, we compared the phenotype and function of TILs derived from liver and lung metastases from patients with gastrointestinal (GI) cancers (n = 14) or melanoma (n = 42). Fewer CD3(+) T cells were found to infiltrate GI compared with melanoma metastases, but the proportions of CD8(+) cells, T cell differentiation stage, and expression of costimulatory molecules were similar for both tumor types. Clinical-scale expansion up to ~50 × 10(9) T cells on average was obtained for all patients with GI cancer and melanoma. From GI tumors, however, TIL outgrowth in high-dose IL-2 yielded 22 ± 1.4% CD3(+)CD8(+) cells compared with 63 ± 2.4% from melanoma (p < 0.001). IFN-γ ELISA demonstrated MHC class I-mediated reactivity of TIL against autologous tumor in 5 of 7 GI cancer patients tested (9% of 188 distinct TIL cultures) and in 9 of 10 melanoma patients (43% of 246 distinct TIL cultures). In these assays, MHC class I-mediated up-regulation of CD137 (4-1BB) expression on CD8(+) cells suggested that 0-3% of TILs expanded from GI cancer metastases were tumor-reactive. This study implies that the main challenge to the development of TIL adoptive cell transfer for metastatic GI cancers may not be the in vitro expansion of bulk TILs, but the ability to select and enrich for tumor-reactive T cells.

Determinants of successful CD8+ T-cell adoptive immunotherapy for large established tumors in mice

PURPOSE

Adoptive cell transfer (ACT) of tumor infiltrating or genetically engineered T cells can cause durable responses in patients with metastatic cancer. Multiple clinically modifiable parameters can comprise this therapy, including cell dose and phenotype, in vivo antigen restimulation, and common gamma-chain (γ(c)) cytokine support. However, the relative contributions of each these individual components to the magnitude of the antitumor response have yet to be quantified.

EXPERIMENTAL DESIGN

To systematically and quantitatively appraise each of these variables, we employed the Pmel-1 mouse model treating large, established B16 melanoma tumors. In addition to cell dose and magnitude of in vivo antigen restimulation, we also evaluated the relative efficacy of central memory (T(CM)), effector memory (T(EM)), and stem cell memory (T(SCM)) subsets on the strength of tumor regression as well as the dose and type of clinically available γ(c) cytokines, including IL-2, IL-7, IL-15, and IL-21.

RESULTS

We found that cell dose, T-cell differentiation status, and viral vaccine titer each were correlated strongly and significantly with the magnitude of tumor regression. Surprisingly, although the total number of IL-2 doses was correlated with tumor regression, no significant benefit to prolonged (≥6 doses) administration was observed. Moreover, the specific type and dose of γ(c) cytokine only moderately correlated with response.

CONCLUSION

Collectively, these findings elucidate some of the key determinants of successful ACT immunotherapy for the treatment of cancer in mice and further show that γ(c) cytokines offer a similar ability to effectively drive antitumor T-cell function in vivo.

A high molecular weight melanoma-associated antigen-specific chimeric antigen receptor redirects lymphocytes to target human melanomas

Immunotherapy, particularly the adoptive cell transfer (ACT) of tumor-infiltrating lymphocytes (TIL), is a very promising therapy for metastatic melanoma. Some patients unable to receive TIL have been successfully treated with autologous peripheral blood lymphocytes (PBL), genetically modified to express human leukocyte antigen (HLA) class I antigen-restricted, melanoma antigen-reactive T-cell receptors; however, substantial numbers of patients remain ineligible due to the lack of expression of the restricting HLA class I allele. We sought to overcome this limitation by designing a non-MHC-restricted, chimeric antigen receptor (CAR) targeting the high molecular weight melanoma-associated antigen (HMW-MAA), which is highly expressed on more than 90% of human melanomas but has a restricted distribution in normal tissues. HMW-MAA-specific CARs containing an antigen recognition domain based on variations of the HMW-MAA-specific monoclonal antibody 225.28S and a T-cell activation domain based on combinations of CD28, 4-1BB, and CD3zeta activation motifs were constructed within a retroviral vector to allow stable gene transfer into cells and their progeny. Following optimization of the HMW-MAA-specific CAR for expression and function in human PBL, these gene-modified T cells secreted cytokines, were cytolytic, and proliferated in response to HMW-MAA-expressing cell lines. Furthermore, the receptor functioned in both CD4(+) and CD8(+) cells, was non-MHC restricted, and reacted against explanted human melanomas. To evaluate this HMW-MAA-specific CAR in patients with metastatic melanoma, we developed a clinical-grade retroviral packaging line. This may represent a novel means to treat the majority of patients with advanced melanoma, most notably those unable to receive current ACT therapies.