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The programmed cell death protein 1 receptor (PD-1) and programmed death ligand 1 (PD-L1) coinhibitory pathway suppresses T-cell–mediated immunity. We hypothesized that cotargeting of PD-1 and PD-L1 with a bispecific antibody molecule could provide an alternative therapeutic approach, with enhanced antitumor activity, compared with monospecific PD-1 and PD-L1 antibodies. Here, we describe LY3434172, a bispecific IgG1 mAb with ablated Fc immune effector function that targets both human PD-1 and PD-L1. LY3434172 fully inhibited the major inhibitory receptor–ligand interactions in the PD-1 pathway. LY3434172 enhanced functional activation of T cells in vitro compared with the parent anti–PD-1 and anti–PD-L1 antibody combination or respective monotherapies. In mouse tumor models reconstituted with human immune cells, LY3434172 therapy induced dramatic and potent antitumor activity compared with each parent antibody or their combination. Collectively, these results demonstrated the enhanced immunomodulatory (immune blockade) properties of LY3434172, which improved antitumor immune response in preclinical studies, thus supporting its evaluation as a novel bispecific cancer immunotherapy.

Supplementary Figures 1-9 and Supplementary Tables 1-3

Figure S9 shows antitumor efficacy of combination therapy in the L55 NSCLC tumor xenograft model

Fig. S1. CARTmeso cell manufacturing and treatment schedules. Fig. S2. Detection of human anti-chimeric antibody responses in patients post-CARTmeso cell infusion. Fig. S3. Serum cytokines and chemokines in PDA patient 21211-101. Fig. S4. CARTmeso cytolytic activity against allogeneic and autologous pancreatic cancer cell lines Table S1. Patient demographics. Table S2. Treatment-related adverse events. Table S3. Protoarray analysis of serum samples from mesothelioma patient 17510-105 Table S4. Protoarray analysis of serum samples from pancreatic cancer patient 21211-101

Table S2 shows human immune effector ADCC and CDC activity EC50 (nM)

Supplementary Materials and Methods

This study compared second-generation chimeric antigen receptors (CAR) encoding signaling domains composed of CD28, ICOS, and 4-1BB (TNFRSF9). Here, we report that certain CARs endow T cells with the ability to undergo long-term autonomous proliferation. Transduction of primary human T cells with lentiviral vectors encoding some of the CARs resulted in sustained proliferation for up to 3 months following a single stimulation through the T-cell receptor (TCR). Sustained numeric expansion was independent of cognate antigen and did not require the addition of exogenous cytokines or feeder cells after a single stimulation of the TCR and CD28. Results from gene array and functional assays linked sustained cytokine secretion and expression of T-bet (TBX21), EOMES, and GATA-3 to the effect. Sustained expression of the endogenous IL2 locus has not been reported in primary T cells. Sustained proliferation was dependent on CAR structure and high expression, the latter of which was necessary but not sufficient. The mechanism involves constitutive signaling through NF-κB, AKT, ERK, and NFAT. The propagated CAR T cells retained a diverse TCR repertoire, and cellular transformation was not observed. The CARs with a constitutive growth phenotype displayed inferior antitumor effects and engraftment in vivo. Therefore, the design of CARs that have a nonconstitutive growth phenotype may be a strategy to improve efficacy and engraftment of CAR T cells. The identification of CARs that confer constitutive or nonconstitutive growth patterns may explain observations that CAR T cells have differential survival patterns in clinical trials. Cancer Immunol Res; 3(4); 356–67. ©2015 AACR.

Table S1: Expression of c-Met and Mesothelin mRNA in activated CD4 T Cells. Table S2: Genes upregulated in CD4+ T cells of healthy human adults expressing c-Met IgG4 continuous CAR or CD19 CD8α non-continuous CAR on day 11. Table S3: Genes downregulated in CD4+ T cells of healthy human adults expressing c-Met IgG4 continuous CAR or CD19 CD8α non-continuous CAR on day 11. Figure S1. Chimeric antigen receptor constructs and relative expression levels. Figure S2. CAR T cells with constitutive proliferation retain specific cytotoxicity. Figure S3. c-Met and mesothelin expression are not detected on human CD4+ T cells. Figure S4. Supernatant from CARs displaying the growth phenotype induces activation of naïve unstimulated T cells. Figure S5.The role of fetal bovine serum in the constitutive growth of c-Met IgG4 28ζ CAR T cells. Figure S6. A) CARs with a constitutive growth phenotype display a unique gene signature. B) CAR T cells with a constitutive growth phenotype display distinct transcription factors. Figure S7. Genome-wide microarray analysis of CAR T cells with constitutive proliferation. Figure S8. Distinct gene expression signature of CAR T cells with constitutive proliferation. Figure S9. CAR T cells with constitutive proliferation have ligand-independent NFAT activation. Figure S10. Transgene expression levels are sufficient to convey the constitutive CAR growth phenotype. Figure S11. Constitutive CAR T cell proliferation results in differentiation and evolution of a distinct cell surface phenotype. Figure S12. Effects of stimulation and cell culture on differentiation of non-transduced T cells. Figure S13. Temporal patterns of telomere restriction fragment length (TRF) in continuous CAR T cells and mock transduced T cells. Figure S14. CAR T cells with a constitutive growth phenotype retain a diverse TCR Vβ repertoire. Figure S15. Engraftment and proliferation of continuous CAR T cells in NSG mice. Figure S16. PGK100 promoter results in antigen driven accumulation of CAR T cells in tissue but not blood.

Off-target toxicity due to the expression of target antigens in normal tissue represents a major obstacle to the use of chimeric antigen receptor (CAR)-engineered T cells for treatment of solid malignancies. To circumvent this issue, we established a clinical platform for engineering T cells with transient CAR expression by using in vitro transcribed mRNA encoding a CAR that includes both the CD3-ζ and 4-1BB costimulatory domains. We present two case reports from ongoing trials indicating that adoptive transfer of mRNA CAR T cells that target mesothelin (CARTmeso cells) is feasible and safe without overt evidence of off-tumor on-target toxicity against normal tissues. CARTmeso cells persisted transiently within the peripheral blood after intravenous administration and migrated to primary and metastatic tumor sites. Clinical and laboratory evidence of antitumor activity was shown in both patients, and the CARTmeso cells elicited an antitumor immune response revealed by the development of novel antiself antibodies. These data show the potential of using mRNA-engineered T cells to evaluate, in a controlled manner, potential off-tumor on-target toxicities and show that short-lived CAR T cells can induce epitope spreading and mediate antitumor activity in patients with advanced cancer. Thus, these findings support the development of mRNA CAR-based strategies for carcinoma and other solid tumors. Cancer Immunol Res; 2(2); 112–20. ©2013 AACR.

Supplementary Figure Legends & Tables

Figure S1. Efficacy of pemetrexed in Lewis Lung carcinoma model and metabolomic analysis of MC38 tumor bearing mice treated with 50 mg/kg of pemetrexed Figure S2. T cell inflamed phenotype induced by pemetrexed is modestly reduced in tumors upon combination with cisplatin Figure S3. Combination Effects of pemetrexed -/+ anti-PD-L1 in MC38, LLC and Colon26 tumor models Figure S4 (A) Mice bearing Colon26 tumors were treated starting 10 days after tumor implantation with pemetrexed (50 mg/kg, 5 days on, 2 days off, IP) and/or anti-PD-L1 (αPD-L1) (500 ug/mouse, weekly IP), and tumors were isolated after 14 days of treatment and single cell suspensions were subjected to flow cytometry analysis. FACS plots show representative data of intra-tumor CD45+ tumor-infiltrating lymphocyte (TIL) T cell (CD3+) and Myeloid cell (CD11b+) subsets frequencies; and percentage of Ki67+ CD4+ T effector cells based on the gating scheme indicated. (B) Spleens, TDLNs and tumors were isolated and antigen specific T cell responses were measured by IFNγ ELISpot, gp70 Tetramer staining (Tet) and Intracellular cytokine staining. (Left) CD8 T cells isolated from pooled spleens and TDLNs from individual mice were cultured alone (control) with irrelevant BALB/c tumor EMT6 or cognate Colon26 tumor cells overnight and number of IFNγ producing T cells was measured by ELISpot. (Middle) Freshly isolated CD8+ T cells from spleens and TDLNs were assessed for % of gp70 Tet+ cells. (Right) Freshly isolated tumors single cell suspensions were stimulated with PMA/ phorbol myristate acetate (PMA) and ionomycin with monensin for 4 hrs and the % of TNF-alpha positive and gp70 Tet+ CD8 T cells were measured from the Live CD45+, CD3+ T cells by FACS. Figure S5. Concordance between QuantiGene and nCounter gene expression data for in vitro activated T cells treated in the presence or absence of pemetrexed (related to Figure 6F). Supplementary Table 1. Ingenuity pathway analysis (IPA) of MC38 tumors treated with pemetrexed or paclitaxel with or without carboplatin Supplementary Table 2: IPA results for Colon26 experiment in Figure 4 sorted by functional class. Pemetrexed monotherapy in this experiment at this timepoint did not have enough differentially expressed genes to generate IPA results.

PDF file - 1065KB, Supplemental Data for Figure 4.

PDF file - 48KB

Supplementary Materials, Methods, Figures and Table legends - PDF file 87K, Supplementary file giving details of supplementary materials and methods, figure legends and table legends

Supplementary Figure S2 - PDF file 84K, Phenotype of DCs following lysate-pulsing (i.e. HOCl-L, UVB-L or FTL), and activation with LPS and IFN-gamma. Unpulsed, mature (mDC) or immature DCs (iDC) served as controls. Data was presented as mean plus-minus SEM

Supplementary Table S1 - PDF file 191K, Cytokine and chemokine productions from DCs of ovarian cancer subjects that were loaded with HOCl-oxidized autologous whole tumor lysate and matured with LPS and IFN-gamma

Purpose: Responses to therapy with chimeric antigen receptor T cells recognizing CD19 (CART19, CTL019) may vary by histology. Mantle cell lymphoma (MCL) represents a B-cell malignancy that remains incurable despite novel therapies such as the BTK inhibitor ibrutinib, and where data from CTL019 therapy are scant. Using MCL as a model, we sought to build upon the outcomes from CTL019 and from ibrutinib therapy by combining these in a rational manner.Experimental Design: MCL cell lines and primary MCL samples were combined with autologous or normal donor-derived anti-CD19 CAR T cells along with ibrutinib. The effect of the combination was studied in vitro and in mouse xenograft models.Results: MCL cells strongly activated multiple CTL019 effector functions, and MCL killing by CTL019 was further enhanced in the presence of ibrutinib. In a xenograft MCL model, we showed superior disease control in the CTL019- as compared with ibrutinib-treated mice (median survival not reached vs. 95 days, P < 0.005) but most mice receiving CTL019 monotherapy eventually relapsed. Therefore, we added ibrutinib to CTL019 and showed that 80% to 100% of mice in the CTL019 + ibrutinib arm and 0% to 20% of mice in the CTL019 arm, respectively, remained in long-term remission (P < 0.05).Conclusions: Combining CTL019 with ibrutinib represents a rational way to incorporate two of the most recent therapies in MCL. Our findings pave the way to a two-pronged therapeutic strategy in patients with MCL and other types of B-cell lymphoma. Clin Cancer Res; 22(11); 2684–96. ©2016 AACR.

Purpose: Whole tumor lysates are promising antigen sources for dendritic cell (DC) therapy as they contain many relevant immunogenic epitopes to help prevent tumor escape. Two common methods of tumor lysate preparations are freeze-thaw processing and UVB irradiation to induce necrosis and apoptosis, respectively. Hypochlorous acid (HOCl) oxidation is a new method for inducing primary necrosis and enhancing the immunogenicity of tumor cells.Experimental Design: We compared the ability of DCs to engulf three different tumor lysate preparations, produce T-helper 1 (TH1)-priming cytokines and chemokines, stimulate mixed leukocyte reactions (MLR), and finally elicit T-cell responses capable of controlling tumor growth in vivo.Results: We showed that DCs engulfed HOCl-oxidized lysate most efficiently stimulated robust MLRs, and elicited strong tumor-specific IFN-γ secretions in autologous T cells. These DCs produced the highest levels of TH1-priming cytokines and chemokines, including interleukin (IL)-12. Mice vaccinated with HOCl-oxidized ID8-ova lysate–pulsed DCs developed T-cell responses that effectively controlled tumor growth. Safety, immunogenicity of autologous DCs pulsed with HOCl-oxidized autologous tumor lysate (OCDC vaccine), clinical efficacy, and progression-free survival (PFS) were evaluated in a pilot study of five subjects with recurrent ovarian cancer. OCDC vaccination produced few grade 1 toxicities and elicited potent T-cell responses against known ovarian tumor antigens. Circulating regulatory T cells and serum IL-10 were also reduced. Two subjects experienced durable PFS of 24 months or more after OCDC.Conclusions: This is the first study showing the potential efficacy of a DC vaccine pulsed with HOCl-oxidized tumor lysate, a novel approach in preparing DC vaccine that is potentially applicable to many cancers. Clin Cancer Res; 19(17); 4801–15. ©2013 AACR.

PDF file - 54KB, Adverse Events Table.

PDF file - 198KB, MAGE-A3 Trojan Peptide Vaccine Reactogenicity.

PDF file - 40KB, ELISA Antibody Responses for the PCV (Prevnar-13(registered trademark)).

Purpose: Myeloma-directed cellular immune responses after autologous stem cell transplantation (ASCT) may reduce relapse rates. We studied whether coinjecting the TLR-3 agonist and vaccine adjuvant Poly-ICLC with a MAGE-A3 peptide vaccine was safe and would elicit a high frequency of vaccine-directed immune responses when combined with vaccine-primed and costimulated autologous T cells.Experimental Design: In a phase II clinical trial (NCT01245673), we evaluated the safety and activity of ex vivo expanded autologous T cells primed in vivo using a MAGE-A3 multipeptide vaccine (compound GL-0817) combined with Poly-ICLC (Hiltonol), granulocyte macrophage colony-stimulating factor (GM-CSF) ± montanide. Twenty-seven patients with active and/or high-risk myeloma received autografts followed by anti-CD3/anti-CD28–costimulated autologous T cells, accompanied by MAGE-A3 peptide immunizations before T-cell collection and five times after ASCT. Immune responses to the vaccine were evaluated by cytokine production (all patients), dextramer binding to CD8+ T cells, and ELISA performed serially after transplant.Results: T-cell infusions were well tolerated, whereas vaccine injection site reactions occurred in >90% of patients. Two of nine patients who received montanide developed sterile abscesses; however, this did not occur in the 18 patients who did not receive montanide. Dextramer staining demonstrated MAGE-A3–specific CD8 T cells in 7 of 8 evaluable HLA-A2+ patients (88%), whereas vaccine-specific cytokine-producing T cells were generated in 19 of 25 patients (76%). Antibody responses developed in 7 of 9 patients (78%) who received montanide and only weakly in 2 of 18 patients (11%) who did not. The 2-year overall survival was 74% [95% confidence interval (CI), 54%–100%] and 2-year event-free survival was 56% (95% CI, 37%–85%).Conclusions: A high frequency of vaccine-specific T-cell responses were generated after transplant by combining costimulated autologous T cells with a Poly-ICLC/GM-CSF–primed MAGE-A3 vaccine. Clin Cancer Res; 20(5); 1355–65. ©2013 AACR.

Supplementary Methods: Fluorescence in situ hybridization (FISH); MTT (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide) enzymatic conversion assay; Western blot analysis; Multiparametric flow cytometry; Table S1. List of the antibodies used for multiparametric flow cytometry; Degranulation assay; Proliferation assay; Cytotoxicity assays; Cytokine measurements; Animal experiments; Figure S1. Different sensitivity to ibrutinib in hematological cell lines; Figure S2. MCL-RL engrafted mice: tumor burden and histology; Figure S3. CTL019 design and production; Figure S4. CTL019 cell production from primary MCL samples; Figure S5. Effect of ibrutinib in T cell function in vitro and in vivo; Figure S5. Effect of ibrutinib in T cell function in vitro and in vivo. A. CTL019 proliferation assay in the presence of ibrutinib;Figure S6. Peripheral blood T cell subsets in mice treated with CART19 or CART19-ibrutinib; Figure S7. CXCR4 and inhibitory/costimulatory receptor expression in peripheral blood of mice treated with CART19 or CART19-ibrutinib; Figure S8. A. Ibrutinib did not enhance the anti-tumor activity of control untransduced T cells.

Purpose:Combination strategies leveraging chemotherapeutic agents and immunotherapy have held the promise as a method to improve benefit for patients with cancer. However, most chemotherapies have detrimental effects on immune homeostasis and differ in their ability to induce immunogenic cell death (ICD). The approval of pemetrexed and carboplatin with anti-PD-1 (pembrolizumab) for treatment of non–small cell lung cancer represents the first approved chemotherapy and immunotherapy combination. Although the clinical data suggest a positive interaction between pemetrexed-based chemotherapy and immunotherapy, the underlying mechanism remains unknown.Experimental Design:Mouse tumor models (MC38, Colon26) and high-content biomarker studies (flow cytometry, Quantigene Plex, and nCounter gene expression analysis) were deployed to obtain insights into the mechanistic rationale behind the efficacy observed with pemetrexed/anti-PD-L1 combination. ICD in tumor cell lines was assessed by calreticulin and HMGB-1 immunoassays, and metabolic function of primary T cells was evaluated by Seahorse analysis.Results:Pemetrexed treatment alone increased T-cell activation in mouse tumors in vivo, robustly induced ICD in mouse tumor cells and exerted T-cell–intrinsic effects exemplified by augmented mitochondrial function and enhanced T-cell activation in vitro. Increased antitumor efficacy and pronounced inflamed/immune activation were observed when pemetrexed was combined with anti-PD-L1.Conclusions:Pemetrexed augments systemic intratumor immune responses through tumor intrinsic mechanisms including immunogenic cell death, T-cell–intrinsic mechanisms enhancing mitochondrial biogenesis leading to increased T-cell infiltration/activation along with modulation of innate immune pathways, which are significantly enhanced in combination with PD-1 pathway blockade.See related commentary by Buque et al., p. 6890

The CD137 receptor plays a key role in mediating immune response by promoting T cell proliferation, survival, and memory. Effective agonism of CD137 has the potential to reinvigorate potent antitumor immunity either alone or in combination with other immune-checkpoint therapies. In this study, we describe the discovery and characterization of a unique CD137 agonist, 7A5, a fully human IgG1 Fc effector-null monoclonal antibody. The biological properties of 7A5 were investigated through in vitro and in vivo studies. 7A5 binds CD137, and the binding epitope overlaps with the CD137L binding site based on structure. 7A5 engages CD137 receptor and activates NF-κB cell signaling independent of cross-linking or Fc effector function. In addition, T cell activation measured by cytokine IFNγ production is induced by 7A5 in peripheral blood mononuclear cell costimulation assay. Human tumor xenograft mouse models reconstituted with human immune cells were used to determine antitumor activity in vivo. Monotherapy with 7A5 inhibits tumor growth, and this activity is enhanced in combination with a PD-L1 antagonist antibody. Furthermore, the intratumoral immune gene expression signature in response to 7A5 is highly suggestive of enhanced T cell infiltration and activation. Taken together, these results demonstrate 7A5 is a differentiated CD137 agonist antibody with biological properties that warrant its further development as a cancer immunotherapy.

Prolonged activation of vascular endothelial growth factor receptor-2 (VEGFR-2) due to mis-regulation of the VEGF pathway induces aberrant blood vessel expansion, which supports growth and survival of solid tumors. Therapeutic interventions that inhibit the VEGFR-2 pathway have therefore become a mainstay of cancer treatment. Non-clinical studies have recently revealed that blockade of angiogenesis can modulate the tumor microenvironment and enhance the efficacy of concurrent immune therapies. Ramucirumab is an FDA-approved anti-angiogenic antibody that inhibits VEGFR-2 and is currently being evaluated in clinical studies in combination with anti-programmed cell death (PD-1) axis checkpoint inhibitors (pembrolizumab, durvalumab, or sintilimab) across several cancer types. The purpose of this study is to establish a mechanistic basis for the enhanced activity observed in the combined blockade of VEGFR-2 and PD-1-axis pathways. Pre-clinical studies were conducted in murine tumor models known to be responsive to anti-PD-1 axis therapy, using monoclonal antibodies that block mouse VEGFR-2 and programmed death-ligand 1 (PD-L1). Combination therapy resulted in enhanced anti-tumor activity compared to anti-PD-L1 monotherapy. VEGFR-2 blockade at early timepoints post-anti-PD-L1 therapy resulted in a dose-dependent and transient enhanced infiltration of T cells, and establishment of immunological memory. VEGFR-2 blockade at later timepoints resulted in enhancement of anti-PD-L1-driven immune cell infiltration. VEGFR-2 and PD-L1 monotherapies induced both unique and overlapping patterns of immune gene expression, and combination therapy resulted in an enhanced immune activation signature. Collectively, these results provide new and actionable insights into the mechanisms by which concurrent VEGFR-2 and PD-L1 antibody therapy leads to enhanced anti-tumor efficacy.

The programmed cell death protein 1 receptor (PD-1) and programmed death ligand 1 (PD-L1) coinhibitory pathway suppresses T-cell–mediated immunity. We hypothesized that cotargeting of PD-1 and PD-L1 with a bispecific antibody molecule could provide an alternative therapeutic approach, with enhanced antitumor activity, compared with monospecific PD-1 and PD-L1 antibodies. Here, we describe LY3434172, a bispecific IgG1 mAb with ablated Fc immune effector function that targets both human PD-1 and PD-L1. LY3434172 fully inhibited the major inhibitory receptor–ligand interactions in the PD-1 pathway. LY3434172 enhanced functional activation of T cells in vitro compared with the parent anti–PD-1 and anti–PD-L1 antibody combination or respective monotherapies. In mouse tumor models reconstituted with human immune cells, LY3434172 therapy induced dramatic and potent antitumor activity compared with each parent antibody or their combination. Collectively, these results demonstrated the enhanced immunomodulatory (immune blockade) properties of LY3434172, which improved antitumor immune response in preclinical studies, thus supporting its evaluation as a novel bispecific cancer immunotherapy.

Background Modulation of the PD-1/PD-L1 axis through antagonist antibodies that block either receptor or ligand has been shown to reinvigorate the function of tumor-specific T cells and unleash potent anti-tumor immunity, leading to durable objective responses in a subset of patients across multiple tumor types. Results Here we describe the discovery and preclinical characterization of LY3300054, a fully human IgG1λ monoclonal antibody that binds to human PD-L1 with high affinity and inhibits interactions of PD-L1 with its two cognate receptors PD-1 and CD80. The functional activity of LY3300054 on primary human T cells is evaluated using a series of in vitro T cell functional assays and in vivo models using human-immune reconstituted mice. LY3300054 is shown to induce primary T cell activation in vitro, increase T cell activation in combination with anti-CTLA4 antibody, and to potently enhance anti-tumor alloreactivity in several xenograft mouse tumor models with reconstituted human immune cells. High-content molecular analysis of tumor and peripheral tissues from animals treated with LY3300054 reveals distinct adaptive immune activation signatures, and also previously not described modulation of innate immune pathways. Conclusions LY3300054 is currently being evaluated in phase I clinical trials for oncology indications.

Transforming growth factor-β (TGFβ) is an important driver of tumor growth via intrinsic and extrinsic mechanisms, and is therefore an attractive target for developing cancer therapeutics. Using preclinical models, we characterized the anti-tumor activity of a small molecule inhibitor of TGFβ receptor I (TGFβRI), galunisertib (LY2157299 monohydrate). Galunisertib demonstrated potent and selective inhibition of TGFβRI with corresponding inhibition of downstream signaling via inhibition of SMAD phosphorylation (pSMAD). Galunisertib also inhibited TGFβ-induced pSMAD in vivo, which enabled a pharmacokinetic/pharmacodynamic profile in Calu6 and EMT6-LM2 tumors. Galunisertib demonstrated anti-tumor activity including inhibition of tumor cell migration and mesenchymal phenotype, reversal of TGFβ-mediated immune-suppression, and tumor growth delay. A concentration-effect relationship was established with a dosing schedule to achieve the optimal level of target modulation. Finally, a rat model demonstrated a correlation between galunisertib-dependent inhibition of pSMAD in tumor tissues and in PBMCs, supporting the use of PBMCs for assessing pharmacodynamic effects. Galunisertib has been tested in several clinical studies with evidence of anti-tumor activity observed in subsets of patients. Here, we demonstrate that galunisertib inhibits a number of TGFβ-dependent functions leading to anti-tumor activity. The enhanced understanding of galunisertib provides rationale for further informed clinical development of TGFβ pathway inhibitors.

The field of cell therapy is rapidly emerging as a priority area for oncology research and drug development. Currently, two chimeric antigen receptor T-cell therapies are approved by the US Food and Drug Administration and other agencies worldwide for two types of hematologic cancers. To facilitate the development of these therapies for patients with life-threatening cancers with limited or no therapeutic options, science- and risk-based approaches will be critical to mitigating and balancing any potential risk associated with either early clinical research or more flexible manufacturing paradigms. Friends of Cancer Research and the Parker Institute for Cancer Immunotherapy convened an expert group of stakeholders to develop specific strategies and proposals for regulatory opportunities to accelerate the development of cell therapies as promising new therapeutics. This meeting took place in Washington, DC on May 17, 2019. As academia and industry expand research efforts and cellular product development pipelines, this report summarizes opportunities to accelerate entry into the clinic for exploratory studies and optimization of cell products through manufacturing improvements for these promising new therapies.

Purpose: Combination strategies leveraging chemotherapeutic agents and immunotherapy have held the promise as a method to improve benefit for patients with cancer. However, most chemotherapies have detrimental effects on immune homeostasis and differ in their ability to induce immunogenic cell death (ICD). The approval of pemetrexed and carboplatin with anti-PD-1 (pembrolizumab) for treatment of non–small cell lung cancer represents the first approved chemotherapy and immunotherapy combination. Although the clinical data suggest a positive interaction between pemetrexed-based chemotherapy and immunotherapy, the underlying mechanism remains unknown. Experimental Design: Mouse tumor models (MC38, Colon26) and high-content biomarker studies (flow cytometry, Quantigene Plex, and nCounter gene expression analysis) were deployed to obtain insights into the mechanistic rationale behind the efficacy observed with pemetrexed/anti-PD-L1 combination. ICD in tumor cell lines was assessed by calreticulin and HMGB-1 immunoassays, and metabolic function of primary T cells was evaluated by Seahorse analysis. Results: Pemetrexed treatment alone increased T-cell activation in mouse tumors in vivo, robustly induced ICD in mouse tumor cells and exerted T-cell–intrinsic effects exemplified by augmented mitochondrial function and enhanced T-cell activation in vitro. Increased antitumor efficacy and pronounced inflamed/immune activation were observed when pemetrexed was combined with anti-PD-L1. Conclusions: Pemetrexed augments systemic intratumor immune responses through tumor intrinsic mechanisms including immunogenic cell death, T-cell–intrinsic mechanisms enhancing mitochondrial biogenesis leading to increased T-cell infiltration/activation along with modulation of innate immune pathways, which are significantly enhanced in combination with PD-1 pathway blockade. See related commentary by Buque et al., p. 6890

Potent CD19-directed immunotherapies, such as chimeric antigen receptor T cells (CART) and blinatumomab, have drastically changed the outcome of patients with relapsed/refractory B cell acute lymphoblastic leukemia (B-ALL). However, CD19-negative relapses have emerged as a major problem that is observed in approximately 30% of treated patients. Developing approaches to preventing and treating antigen-loss escapes would therefore represent a vertical advance in the field. Here, we found that in primary patient samples, the IL-3 receptor α chain CD123 was highly expressed on leukemia-initiating cells and CD19-negative blasts in bulk B-ALL at baseline and at relapse after CART19 administration. Using intravital imaging in an antigen-loss CD19-negative relapse xenograft model, we determined that CART123, but not CART19, recognized leukemic blasts, established protracted synapses, and eradicated CD19-negative leukemia, leading to prolonged survival. Furthermore, combining CART19 and CART123 prevented antigen-loss relapses in xenograft models. Finally, we devised a dual CAR-expressing construct that combined CD19- and CD123-mediated T cell activation and demonstrated that it provides superior in vivo activity against B-ALL compared with single-expressing CART or pooled combination CART. In conclusion, these findings indicate that targeting CD19 and CD123 on leukemic blasts represents an effective strategy for treating and preventing antigen-loss relapses occurring after CD19-directed therapies.

Background Modulation of the PD-1/PD-L1 axis through antagonist antibodies that block either receptor or ligand has been shown to reinvigorate the function of tumor-specific T cells and unleash potent anti-tumor immunity, leading to durable objective responses in a subset of patients across multiple tumor types. Results Here we describe the discovery and preclinical characterization of LY3300054, a fully human IgG1λ monoclonal antibody that binds to human PD-L1 with high affinity and inhibits interactions of PD-L1 with its two cognate receptors PD-1 and CD80. The functional activity of LY3300054 on primary human T cells is evaluated using a series of in vitro T cell functional assays and in vivo models using human-immune reconstituted mice. LY3300054 is shown to induce primary T cell activation in vitro, increase T cell activation in combination with anti-CTLA4 antibody, and to potently enhance anti-tumor alloreactivity in several xenograft mouse tumor models with reconstituted human immune cells. High-content molecular analysis of tumor and peripheral tissues from animals treated with LY3300054 reveals distinct adaptive immune activation signatures, and also previously not described modulation of innate immune pathways. Conclusions LY3300054 is currently being evaluated in phase I clinical trials for oncology indications. Electronic supplementary material The online version of this article (10.1186/s40425-018-0329-7) contains supplementary material, which is available to authorized users.

Cancer immunotherapy based on genetically redirecting T cells has been used successfully to treat B cell malignancies1-3. In this strategy, the T cell genome is modified by integration of viral vectors or transposons encoding chimaeric antigen receptors (CARs) that direct tumour cell killing. However, this approach is often limited by the extent of expansion and persistence of CAR T cells4,5. Here we report mechanistic insights from studies of a patient with chronic lymphocytic leukaemia treated with CAR T cells targeting the CD19 protein. Following infusion of CAR T cells, anti-tumour activity was evident in the peripheral blood, lymph nodes and bone marrow; this activity was accompanied by complete remission. Unexpectedly, at the peak of the response, 94% of CAR T cells originated from a single clone in which lentiviral vector-mediated insertion of the CAR transgene disrupted the methylcytosine dioxygenase TET2 gene. Further analysis revealed a hypomorphic mutation in this patient's second TET2 allele. TET2-disrupted CAR T cells exhibited an epigenetic profile consistent with altered T cell differentiation and, at the peak of expansion, displayed a central memory phenotype. Experimental knockdown of TET2 recapitulated the potency-enhancing effect of TET2 dysfunction in this patient's CAR T cells. These findings suggest that the progeny of a single CAR T cell induced leukaemia remission and that TET2 modification may be useful for improving immunotherapies.

Positive detection of minimal residual disease (MRD) by multichannel flow cytometry (MFC) prior to hematopoietic cell transplantation (HCT) of patients with acute lymphoblastic leukemia (ALL) identifies patients at high risk for relapse, but many pre-HCT MFC-MRD negative patients also relapse, and the predictive power MFC-MRD early post-HCT is poor. To test whether the increased sensitivity of next-generation sequencing (NGS)-MRD better identifies pre- and post-HCT relapse risk, we performed immunoglobulin heavy chain (IgH) variable, diversity, and joining (V[D]J) DNA sequences J NGS-MRD on 56 patients with B-cell ALL enrolled in Children's Oncology Group trial ASCT0431. NGS-MRD predicted relapse and survival more accurately than MFC-MRD (P < .0001), especially in the MRD negative cohort (relapse, 0% vs 16%; P = .02; 2-year overall survival, 96% vs 77%; P = .003). Post-HCT NGS-MRD detection was better at predicting relapse than MFC-MRD (P < .0001), especially early after HCT (day 30 MFC-MRD positive relapse rate, 35%; NGS-MRD positive relapse rate, 67%; P = .004). Any post-HCT NGS positivity resulted in an increase in relapse risk by multivariate analysis (hazard ratio, 7.7; P = .05). Absence of detectable IgH-V(D)J NGS-MRD pre-HCT defines good-risk patients potentially eligible for less intense treatment approaches. Post-HCT NGS-MRD is highly predictive of relapse and survival, suggesting a role for this technique in defining patients early who would be eligible for post-HCT interventions. The trial was registered at www.clinicaltrials.gov as #NCT00382109.

This study compared second-generation chimeric antigen receptors (CAR) encoding signaling domains composed of CD28, ICOS, and 4-1BB (TNFRSF9). Here, we report that certain CARs endow T cells with the ability to undergo long-term autonomous proliferation. Transduction of primary human T cells with lentiviral vectors encoding some of the CARs resulted in sustained proliferation for up to 3 months following a single stimulation through the T-cell receptor (TCR). Sustained numeric expansion was independent of cognate antigen and did not require the addition of exogenous cytokines or feeder cells after a single stimulation of the TCR and CD28. Results from gene array and functional assays linked sustained cytokine secretion and expression of T-bet (TBX21), EOMES, and GATA-3 to the effect. Sustained expression of the endogenous IL2 locus has not been reported in primary T cells. Sustained proliferation was dependent on CAR structure and high expression, the latter of which was necessary but not sufficient. The mechanism involves constitutive signaling through NF-κB, AKT, ERK, and NFAT. The propagated CAR T cells retained a diverse TCR repertoire, and cellular transformation was not observed. The CARs with a constitutive growth phenotype displayed inferior antitumor effects and engraftment in vivo. Therefore, the design of CARs that have a nonconstitutive growth phenotype may be a strategy to improve efficacy and engraftment of CAR T cells. The identification of CARs that confer constitutive or nonconstitutive growth patterns may explain observations that CAR T cells have differential survival patterns in clinical trials. Cancer Immunol Res; 3(4); 356–67. ©2015 AACR.

Summary: Abemaciclib, an inhibitor of cyclin dependent kinases 4 and 6 (CDK4/6), has recently been approved for the treatment of hormone receptor-positive breast cancer. In this study, we use murine syngeneic tumor models and in vitro assays to investigate the impact of abemaciclib on T cells, the tumor immune microenvironment and the ability to combine with anti-PD-L1 blockade. Abemaciclib monotherapy resulted in tumor growth delay that was associated with an increased T cell inflammatory signature in tumors. Combination with anti-PD-L1 therapy led to complete tumor regressions and immunological memory, accompanied by enhanced antigen presentation, a T cell inflamed phenotype, and enhanced cell cycle control. In vitro, treatment with abemaciclib resulted in increased activation of human T cells and upregulated expression of antigen presentation genes in MCF-7 breast cancer cells. These data collectively support the clinical investigation of the combination of abemaciclib with agents such as anti-PD-L1 that modulate T cell anti-tumor immunity. : Schaer, Beckmann et al. describe unique immune-modulating properties of abemaciclib that include upregulation of antigen presentation on tumor cells and increased T cell activation. These activities synergize with anti-PD-L1 therapy to further enhance immune activation, including macrophage and DC antigen presentation, and also lead to a reciprocal increase in abemaciclib-dependent cell cycle gene regulation. Keywords: CDK4/6, abemaciclib, PD-1, PD-L1, combination immunotherapy, cancer

Several decades of humoral immunotherapy using monoclonal antibodies and cellular immunotherapy using hematopoietic cell transplantation have recently culminated in a successful merger: the development and clinical application of genetically engineered antibody–T cell chimeras. Also known as chimeric antigen receptor T cells (CAR T cells), these entities combine the exquisite antigen specificity of antibodies with the polyfunctionality and potency of cellular immunity and are a prime example of the potential for synthetic biology to treat disease. CAR T cells overcome several of the biologic obstacles that have historically hampered immunotherapy while providing fundamental mechanistic insights into cellular immunology and revealing new challenges in genetic engineering and target selection. Results from early-phase CAR T-cell–based clinical trials demonstrate the significant potential for this approach to affect dramatic and complete clinical responses while revealing novel toxicities associated with activation of potent and specific antitumor immunity. Cancer Res; 74(22); 6383–9. ©2014 AACR.

Direct immune activation via agonistic mAbs is a potentially complementary approach to therapeutic blockade of inhibitory immune receptors in cancer. Here, we provide genetic analysis of the immunologic consequences associated with the use of an agonistic CD40 mAb in a patient with metastatic melanoma who responded, underwent a single metastasectomy, and then achieved a complete remission ongoing for more than 9 years after starting therapy. Tumor microenvironment after immunotherapy was associated with proinflammatory modulations and emergence of a de novo T-cell repertoire as detected by next-generation sequencing of T-cell receptors (TCR) in the tumor and blood. The de novo T-cell repertoire identified in the posttreatment metastasectomy sample was also present—and in some cases expanded—in the circulation years after completion of therapy. Comprehensive study of this “exceptional responder” highlights the emerging potential of direct immune agonists in the next wave of cancer immunotherapies and a potential role for TCR deep sequencing in cancer immune assessment. Cancer Immunol Res; 2(11); 1051–8. ©2014 AACR.

Adoptive immunotherapy, or the infusion of lymphocytes, is a promising approach for the treatment of cancer and certain chronic viral infections. The application of the principles of synthetic biology to enhance T cell function has resulted in substantial increases in clinical efficacy. The primary challenge to the field is to identify tumor-specific targets to avoid off-tumor, on-target toxicity. Given recent advances in efficacy in numerous pilot trials, the next steps in clinical development will require multicenter trials to establish adoptive immunotherapy as a mainstream technology.

Aberrant regulation of DNA methylation is characteristic of cancer cells and clearly influences phenotypes of various malignancies. Despite clear correlations between DNA methylation and patient outcome, tests that directly measure multiple-locus DNA methylation are typically expensive and technically challenging. Previous studies have demonstrated that the prognosis of patients with acute myeloid leukemia can be predicted by the DNA methylation pattern of 18 loci. We have developed a novel strategy, termed microsphere HpaII tiny fragment enrichment by ligation-mediated PCR (MELP), to simultaneously analyze the DNA methylation pattern at these loci using methylation-specific DNA digestion, fluorescently labeled microspheres, and branched DNA hybridization. The method uses techniques that are inexpensive and easily performed in a molecular laboratory. MELP accurately reflects the methylation levels at each locus analyzed and segregates patients with acute myeloid leukemia into prognostic subgroups. Our results demonstrate the usefulness of MELP as a platform for simultaneous evaluation of DNA methylation of multiple loci.

Off-target toxicity due to the expression of target antigens in normal tissue represents a major obstacle to the use of chimeric antigen receptor (CAR)-engineered T cells for treatment of solid malignancies. To circumvent this issue, we established a clinical platform for engineering T cells with transient CAR expression by using in vitro transcribed mRNA encoding a CAR that includes both the CD3-ζ and 4-1BB costimulatory domains. We present two case reports from ongoing trials indicating that adoptive transfer of mRNA CAR T cells that target mesothelin (CARTmeso cells) is feasible and safe without overt evidence of off-tumor on-target toxicity against normal tissues. CARTmeso cells persisted transiently within the peripheral blood after intravenous administration and migrated to primary and metastatic tumor sites. Clinical and laboratory evidence of antitumor activity was shown in both patients, and the CARTmeso cells elicited an antitumor immune response revealed by the development of novel antiself antibodies. These data show the potential of using mRNA-engineered T cells to evaluate, in a controlled manner, potential off-tumor on-target toxicities and show that short-lived CAR T cells can induce epitope spreading and mediate antitumor activity in patients with advanced cancer. Thus, these findings support the development of mRNA CAR-based strategies for carcinoma and other solid tumors. Cancer Immunol Res; 2(2); 112–20. ©2013 AACR.

Chimeric antigen receptor–modified T (CART)-cell–based targeting of solid tumors remains a considerable and worthwhile challenge in the field of immunotherapy. The role of chemotherapy to target stroma and enhance chimeric antigen receptor (CAR) cell antitumor function, expansion, and persistence is still unresolved. Clin Cancer Res; 24(6); 1246–7. ©2018 AACR. See related article by Guo et al., p. 1277