scholarly journals 782 PD-L1-targeted ISAC combines myeloid cell activation, immune-checkpoint inhibition and ADCP to improve anti-tumor efficacy over anti-PD-L1 antibodies in preclinical models

2021 ◽  
Vol 9 (Suppl 3) ◽  
pp. A817-A817
Author(s):  
Justin Kenkel ◽  
Rishali Gadkari ◽  
Karla Henning ◽  
Romas Kudirka ◽  
William Mallet ◽  
...  
Keyword(s):  
T Cell ◽  
Tumor Cells ◽  
Immune Checkpoint ◽  
Cell Activation ◽  
Myeloid Cell ◽  
Checkpoint Inhibition ◽  
Immune Checkpoint Inhibition ◽  
Tumor Models

BackgroundPD-L1 is an immune checkpoint that regulates anti-tumor T cell responses and is expressed on tumor cells as well as tumor-infiltrating immune cells across many tumor types. Immune-stimulating antibody conjugates (ISACs) consist of tumor-targeting antibodies conjugated to immune stimulants and are designed to activate the innate and adaptive immune systems against tumor cells following systemic administration. Here we show that PD-L1-targeted TLR7/8 ISACs elicit robust myeloid cell activation which leads to improved anti-tumor responses compared to anti-PD-L1 treatment in pre-clinical tumor models.MethodsA panel of proprietary anti-PD-L1 antibodies was identified through a phage display screen and subsequently tested for PD-L1 binding affinity and specificity, PD-L1/PD-1 blocking, antibody-dependent cellular phagocytosis (ADCP) by myeloid cells, and anti-tumor efficacy. Lead antibodies were conjugated to proprietary TLR7/8 agonists, and the resulting PD-L1 ISACs were evaluated for in vitro myeloid cell activation and in vivo efficacy against syngeneic and xenograft tumors.ResultsAnti-PD-L1 antibodies induced robust ADCP by myeloid effector cells and medium to strong PD-L1/PD-1 blockade in vitro. Selected antibodies inhibited the growth of syngeneic MC38-hPD-L1 tumors in vivo, confirming efficient immune-checkpoint blockade. The conjugated PD-L1 ISACs induced robust, target-dependent activation of myeloid cells when co-cultured with PD-L1-expressing tumor cells, as measured by increased secretion of such cytokines as IL-12p70, IFN-alpha, and TNF-alpha. Importantly, myeloid activation was observed following co-culture with tumor cells having various levels of endogenous PD-L1 expression that was within the range of PD-L1 expression observed in human tumors. Systemically administered surrogate PD-L1 ISACs were well tolerated in mice and showed improved anti-tumor efficacy over anti-PD-L1 antibodies, with significant tumor growth delay or complete responses frequently observed in syngeneic (e.g. MB49, MC38-hPD-L1) as well as xenograft (e.g. HCC1954-hPD-L1) tumor models.ConclusionsThese data demonstrate the potential of a PD-L1-targeted ISAC as a multifunctional therapeutic that may improve efficacy of PD-L1/PD-1 inhibition by combining three mechanisms of action into a single molecule: TLR-mediated myeloid cell activation, T cell activation through immune-checkpoint inhibition as well as ADCP.Ethics ApprovalAll animal studies were performed in accordance with Institutional Animal Care and Use Committee (IACUC)-approved protocols.

Bispecific anti-PD-1/PD-L1 antibody CTX-8371 to promote cellular clustering and PD-1 shedding, antitumor activity and tolerability.

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. e15056-e15056
Author(s):  
Diana I. Albu ◽  
Yan Qin ◽  
Xianzhe Wang ◽  
Vivian Li ◽  
Taeg Kim ◽  
...  
Keyword(s):  
T Cell ◽  
Transgenic Mice ◽  
T Cell Activation ◽  
Cell Activation ◽  
Mouse Tumor ◽  
Tumor Models ◽  
Cynomolgus Monkeys ◽  
Range Finding

e15056 Background: Checkpoint blockade therapies targeting PD-1 and PD-L1 have shown great success for the treatment of various malignancies. However, a substantial fraction of patients with PD-L1-positive tumors remain unresponsive to these therapies. Novel therapy with significantly greater activity than the leading PD-1/PD-L1 inhibitors is expected to bring additional clinical benefit to patients. Here we describe the preclinical evaluation of CTX-8371, which combines anti-PD-1 and anti-PD-L1 monoclonal antibodies in one bispecific tetravalent molecule. Methods: The immune-enhancing activity of CTX-8371 was tested in vitro in T cell activation assays and tumor cell killing assay. CTX-8371 anti-tumor efficacy in vivo was assessed using mouse tumor cells expressing human PD-L1 implanted in transgenic mice humanized at the PD-1 and PD-L1 loci. CTX-8371 anti-tumor activity was also tested in xenograft tumor models. The mechanism of action of CTX-8371 was investigated in vitro using Jurkat cells expressing PD-1 or PD-L1, human PBMCs, and in vivo in tumor-bearing, chimeric PD-1/PD-L1 transgenic mice. CTX-8371 PK was determined in mice using an MSD ELISA-based assay and in cynomolgus monkeys using a qualified ELISA method. Dose range finding and toxicokinetic studies were performed in cynomolgus monkeys. Results: CTX-8371 potently enhanced T cell activation and function in vitro and showed curative efficacy as monotherapy in multiple solid tumor models, isografts or xenografts. Furthermore, CTX-8371 demonstrated superior anti-tumor efficacy compared to Keytruda or atezolizumab in checkpoint inhibitors-sensitive and resistant syngeneic mouse tumor models. Mechanistically, in addition to blocking PD-1 interaction with PD-L1, CTX-8371 bispecific antibody facilitated cell to cell bridging between cells expressing PD-1 and cells expressing PD-L1. Furthermore, we show that simultaneous binding of CTX-8371 to both PD-1 and PD-L1 resulted in long term PD-1 shedding. This suggests that CTX-8371 may prevent or overcome T cell exhaustion within the tumor microenvironment, thus providing additional advantage over existing therapies. Lastly, excellent tolerability was observed in non-human primates given 2 weekly drug infusions at up to 50 mg/kg dose. Conclusions: CTX-8371 displays multiple mechanisms of action over monoclonal PD1/PD-L1 blockade. These unique pharmacological properties of CTX-8371 could explain the enhanced T cell responses to tumor antigens and superior efficacy over current monoclonal antibody therapies. With favorable PK/PD and toxicology profiles in mice and cynomolgus monkeys, CTX-8371 warrants further advancement to clinical testing.

550 An Axl-targeting monoclonal antibody that inhibits Axl activity and potently stimulates the innate immune response

2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A587-A587
Author(s):  
Diego Alvarado ◽  
Laura Vitale ◽  
Mike Murphy ◽  
Thomas O’Neill ◽  
Edward Natoli ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
T Cell ◽  
Tumor Cells ◽  
T Cell Activation ◽  
Cell Activation ◽  
Human Cancer ◽  
Cell Activity ◽  
Negative Regulator

BackgroundAxl is a member of the TAM (Tyro3/Axl/MerTK) family of receptor tyrosine kinases and a negative regulator of innate immunity. Activation of Axl through its ligand Gas6 leads to suppression of myeloid cell activity, while its activation in tumor cells drives tumor growth, metastasis, and is associated with acquired resistance to targeted therapies, radiotherapy and chemotherapy.MethodsPurified monoclonal antibodies and variants thereof were tested in human cancer lines and primary human myeloid cells for effects on Axl signaling and immune activation, respectively.ResultsWe describe a humanized IgG1 Axl-targeting monoclonal antibody (mAb), CDX-0168, that binds to the ligand-binding domain of Axl with sub-nanomolar affinity and potently inhibits Gas6 binding. In tumor cells, CDX-0168 inhibits Gas6-dependent Axl phosphorylation and signaling and elicits tumor cell killing via ADCC in vitro and in vivo. In primary human immune cells, CDX-0168 treatment induces potent release of pro-inflammatory cytokines and chemokines from dendritic cells, monocytes and macrophages through an Fc receptor-dependent mechanism and enhanced T cell activation in mixed lymphocyte reactions. Axl inhibition may further enhance antitumor activity associated with PD-(L)1 blockade. To this end, we generated a tetravalent bispecific Axl x PD-L1 antibody combining CDX-0168 with a potent anti-PD-L1 mAb (9H9) using an IgG-scFv format. The bispecific antibody elicits greater cytokine release and T cell activation in vitro than the combination of the parental antibodies, while maintaining robust Axl and PD-L1 blockade.ConclusionsAdditional studies investigating simultaneous blockade of the Axl and PD-L1 pathways with other agents may further exploit the potential for this novel anti-cancer therapeutic approach.

scholarly journals Potent and Selective Antitumor Activity of a T-Cell Engaging Bispecific Antibody Targeting a Membrane-Proximal Epitope of ROR1

2017 ◽  
Author(s):  
Junpeng Qi ◽  
Xiuling Li ◽  
Haiyong Peng ◽  
HaJeung Park ◽  
Christoph Rader
Keyword(s):  
T Cell ◽  
Antitumor Activity ◽  
Tumor Cells ◽  
T Cell Activation ◽  
Cell Activation ◽  
Three Dimensional ◽  
Bispecific Antibodies ◽  
Dimensional Structure

AbstractT-cell engaging bispecific antibodies present a promising strategy for cancer immunotherapy and numerous bispecific formats have been developed for retargeting cytolytic T cells toward tumor cells. To explore the therapeutic utility of T-cell engaging bispecific antibodies targeting the receptor tyrosine kinase ROR1, which is expressed by tumor cells of various hematologic and solid malignancies, we used a bispecific ROR1 × CD3 scFv-Fc format based on a heterodimeric and aglycosylated Fc domain designed for extended circulatory half-life and diminished systemic T-cell activation. A diverse panel of ROR1-targeting scFv derived from immune and naïve rabbit antibody repertoires was compared in this bispecific format for target-dependent T-cell recruitment and activation. A ROR1-targeting scFv with a membrane-proximal epitope, R11, revealed potent and selective antitumor activity in vitro and in vivo and emerged as a prime candidate for further preclinical and clinical studies. To elucidate the precise location and engagement of this membrane-proximal epitope, which is conserved between human and mouse ROR1, the three-dimensional structure of scFv R11 in complex with the kringle domain of ROR1 was determined by X-ray crystallography at 1.6-Å resolution.

scholarly journals 863 In vitro and in vivo studies establish DuoBody®-CD3xB7H4 as a novel drug candidate for the treatment of solid cancers

2021 ◽  
Vol 9 (Suppl 3) ◽  
pp. A904-A904
Author(s):  
Louise Koopman ◽  
Laura Smits-de Vries ◽  
Frederikke Lihme Egerod ◽  
Sebastiaan Wubben ◽  
Mischa Houtkamp ◽  
...  
Keyword(s):  
T Cell ◽  
Antitumor Activity ◽  
Tumor Cells ◽  
T Cell Activation ◽  
Cell Activation ◽  
Cynomolgus Monkeys ◽  
Animal Care ◽  
Dose Dependent

BackgroundThe immune checkpoint protein B7H4 is expressed on malignant cells in various solid cancers, whereas its expression is highly restricted in normal tissue. B7H4 is therefore an attractive target for a CD3 bispecific antibody (bsAb) therapeutic. Moreover, its expression is reported to be inversely correlated with PD-L1. Here, we describe the preclinical characterization of two B7H4-targeting CD3 bsAbs with different CD3 affinities, supporting the selection of our clinical lead, DuoBody-CD3xB7H4 (GEN1047).MethodsB7H4 protein expression in patient-derived samples was determined by immunohistochemistry. Controlled Fab-arm exchange of an Fc-silenced B7H4 antibody with two Fc-silenced CD3ε-binding antibodies generated two CD3xB7H4 bsAbs that differ in CD3 binding affinity by approximately 30-fold. In vitro T-cell mediated cytotoxicity, T-cell activation, and cytokine release were assayed using cocultures of B7H4-expressing tumor cells and healthy donor T cells. Nonclinical safety (NCS) of the two CD3xB7H4 bsAbs was assessed in cynomolgus monkeys, and antitumor activity of the clinical lead in vivo was tested in a patient-derived xenograft (PDX) screen in mice with a humanized immune system (HIS).ResultsB7H4 protein expression was confirmed in tumor biopsies from multiple indications, including breast, ovarian and lung cancer. Both bsAbs induced target-specific and dose-dependent tumor cell kill in vitro. Maximal kill and T-cell activation were comparable for both variants, although the potency of the high CD3 affinity bsAb was higher. However, production of inflammatory cytokines at comparable effective concentrations (IC90) was lower for the low CD3 affinity bsAb. Single dose NCS studies in cynomolgus monkeys showed that both CD3xB7H4 bsAbs were well-tolerated. A dose-dependent increase in plasma cytokines IL-6 and MCP-1 2 hours after dosing was observed only with the high CD3 affinity bsAb. Based on these findings, the low CD3 affinity bsAb was selected for follow-up studies and named DuoBody-CD3xB7H4 (GEN1047). DuoBody-CD3xB7H4 demonstrated antitumor activity in vivo in a PDX screen in HIS mice. Repeated dosing of DuoBody-CD3xB7H4 in cynomolgus monkeys confirmed an acceptable safety profile up to the maximal dose tested (30 mg/kg).ConclusionsThese studies describe the preclinical development of DuoBody-CD3xB7H4, a bsAb that induces T-cell mediated cytotoxicity of B7H4-positive tumor cells, which may provide an alternative therapeutic modality in the immune-oncology space for patients with solid cancers.Ethics ApprovalAnimal experiments were performed according to the guidelines of the Institutional Animal Care and Use Committee (IACUC) and in accordance with the regulations of the Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC). NCS studies were conducted at Citoxlab (Evreux, France) and Charles River Laboratories (Tranent, UK) in accordance with the European Convention for the Protection of Vertebrate Animals Used for Experimental and Other Scientific Purposes (Council of Europe).

scholarly journals 704 Preclinical mechanism of action and pharmacodynamic biomarker studies of DuoBody®-CD3x5T4 in vitro and in vivo in solid cancer models

2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A746-A746
Author(s):  
Kristel Kemper ◽  
Ellis Gielen ◽  
Mischa Houtkamp ◽  
Peter Boross ◽  
Saskia Burm ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Tumor Cells ◽  
T Cell Activation ◽  
Cell Activation ◽  
T Cell Subsets ◽  
Animal Protection ◽  
Anti Tumor Activity

BackgroundThe tumor-associated antigen 5T4 is expressed across a wide range of solid cancers. DuoBody-CD3x5T4 is a bispecific antibody (bsAb) that crosslinks CD3 on T cells with 5T4 on tumor cells, thereby inducing T-cell activation and T-cell mediated cytotoxicity in 5T4-expressing tumor cells. Here, we tested the capacity of DuoBody-CD3x5T4 to engage different T-cell subsets in vitro and investigated the mechanism of action (MoA) in vivo by combining preclinical efficacy studies with exploratory pharmacodynamic (PD) biomarker analysesMethodsImmunohistochemistry was performed on patient-derived tumor tissue-microarrays using a commercial 5T4 monoclonal antibody (EPR5529). The capacity of DuoBody-CD3x5T4 to engage naïve and memory T-cell subsets was assessed in co-cultures of T cells and 5T4-positive tumor cells, using T-cell activation and T-cell mediated cytotoxicity as readouts. Anti-tumor activity in vivo as well as peripheral and intratumoral PD biomarkers were investigated in humanized mice bearing 5T4-expressing cell line-derived xenograft (CDX) or patient-derived xenograft (PDX) tumor models.ResultsHigh prevalence of 5T4 expression (in >86% of biopsies) was observed in NSCLC, SCCHN, TNBC, bladder, esophageal, prostate and uterine cancer. In co-cultures of 5T4+ tumor cells and T cells in vitro, DuoBody-CD3x5T4 induced dose-dependent cytotoxicity, associated with T-cell activation, proliferation, and cytokine, perforin and granzyme production. Crosslinking of T cells with 5T4-expressing tumor cells was essential as no cytotoxicity was observed in CRISPR-Cas9-generated 5T4-knockout tumor cells or with control bsAbs targeting only CD3 or 5T4. Importantly, naïve and memory CD4+ or CD8+ T-cell subsets had equal capacity to mediate DuoBody-CD3x5T4-induced cytotoxicity, although naïve T-cell subsets showed slower kinetics. DuoBody-CD3x5T4 (0.5–20 mg/kg) demonstrated anti-tumor activity in 5T4+ breast and prostate cancer CDX and lung cancer PDX models in humanized mice. Treatment with DuoBody-CD3x5T4 was associated with intratumoral and peripheral T-cell activation as well as elevated cytokine levels, including IFNγ, IL-6 and IL-8, in peripheral blood.ConclusionsDuoBody-CD3x5T4 induced T-cell mediated cytotoxicity in 5T4-expressing tumor cells, associated with T-cell activation and cytokine production in vitro. DuoBody-CD3x5T4 efficiently engaged naïve and memory T cells within both CD4+ and CD8+ T-cell populations to induce T-cell mediated cytotoxicity in 5T4+ tumor cells. In humanized CDX and PDX mouse models, DuoBody-CD3x5T4 showed anti-tumor activity, in addition to PD biomarkers associated with T-cell activation in the tumor and periphery. Currently, DuoBody-CD3x5T4 is being investigated in a first-in-human clinical trial for the treatment of solid tumors (NCT04424641), in which exploratory biomarker analyses to study the clinical MoA and PD are included.Ethics ApprovalThe CDX animal experiments performed are in compliance with the Dutch animal protection law (WoD) translated from the directives (2010/63/EU) and are approved by the Ethical committee of Utrecht. For the PDX models, all patients had given written informed consent, and the animal experiments were carried out in accordance with the German Animal Protection Law (LaGeSoBerlin, A0452/08). The studies were approved by the local Institutional Review Board of Charite University Medicine, Germany.

scholarly journals 781 Validation of the combinatorial effect of blinatumomab and nivolumab in cancer therapy

2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A831-A831
Author(s):  
Tienan Wang ◽  
Qing Lin ◽  
Jie Zhang
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cd8 T Cells ◽  
Immune Checkpoint ◽  
Culture System ◽  
Cell Activation ◽  
Checkpoint Inhibitors

BackgroundCancer immunotherapies, including immune checkpoint inhibitors, CAR-T, cancer vaccines and bispecific antibodies, have been brought to spot light in recent years as several therapeutic strategies targeting the immune system have produced exciting clinical results. Bispecific antibody typically play dual roles in blocking the immune checkpoint and redirecting/re-boosting the function of the immune effector cells. Blinatumomab belongs to CD3 bispecific T cell engager (CD3 BiTE), which was engineered to harbor two arms binding with CD3 and CD19 simultaneously and direct CD8+ T cells to specifically recognize CD19 positive lymphoma cells to execute cytotoxicity. Approval of Blinatumomab for patients with relapse/refractory B cell acute lymphoblastic leukemia (ALL) has driven remarkable increase in combination studies of Blinatumomab with other immunotherapies such as checkpoint inhibitors.MethodsIn this study, we developed CD8+ T cytotoxic system targeting different B lymphoma cell line and fully validated the function of Blinatumomab in promoting target tumor cell lysis by primary CD8+ T cells (figure 1). In addition, we established a mixed lymphocyte and tumor system to mimic physiological TME to dissect the combinational role of Nivolumab and Blinatumomab (figure 2).ResultsThe result suggest that combinatory therapy is highly depend on the dosage of Blinatumomab and also T cell number in the TME, which might give an instruction for ongoing clinical trial design. Finally, we have employed humanized mouse models bearing Raji or Daudi tumor cells to further validate this combination treatment in vivo. Both In-vivo and In-vitro data support that Blinatumomab is dominant in activing T cell and Nivolumab can only exhibit synergistic effect under suboptimal dosage of Blinatumomab.Abstract 781 Figure 1Establishment of In vitro co-culture system for CD3 BiTEestablish in vitro human PBMC based system to validate CD3 BiTE functionAbstract 781 Figure 2Opdivo and CD3 BiTE CombinationOpdivo could further promote T cell activation under the treatment of CD3 BiTEConclusionsSuccessfully establish in vitro system to evaluate the function of CD3 BiTE and also take advantage of MLR/tumor co-culture system to demonstrate PD1 antibody could further promote T cell activation under appropriate dosage of CD3 BiTE.

scholarly journals Generation of T-cell-redirecting bispecific antibodies with differentiated profiles of cytokine release and biodistribution by CD3 affinity tuning

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Lauric Haber ◽  
Kara Olson ◽  
Marcus P. Kelly ◽  
Alison Crawford ◽  
David J. DiLillo ◽  
...  
Keyword(s):  
T Cell ◽  
Tumor Cells ◽  
Binding Affinity ◽  
T Cell Activation ◽  
Cell Activation ◽  
Therapeutic Index ◽  
Bispecific Antibodies ◽  
Cytokine Release

AbstractT-cell-redirecting bispecific antibodies have emerged as a new class of therapeutic agents designed to simultaneously bind to T cells via CD3 and to tumor cells via tumor-cell-specific antigens (TSA), inducing T-cell-mediated killing of tumor cells. The promising preclinical and clinical efficacy of TSAxCD3 antibodies is often accompanied by toxicities such as cytokine release syndrome due to T-cell activation. How the efficacy and toxicity profile of the TSAxCD3 bispecific antibodies depends on the binding affinity to CD3 remains unclear. Here, we evaluate bispecific antibodies that were engineered to have a range of CD3 affinities, while retaining the same binding affinity for the selected tumor antigen. These agents were tested for their ability to kill tumor cells in vitro, and their biodistribution, serum half-life, and anti-tumor activity in vivo. Remarkably, by altering the binding affinity for CD3 alone, we can generate bispecific antibodies that maintain potent killing of TSA + tumor cells but display differential patterns of cytokine release, pharmacokinetics, and biodistribution. Therefore, tuning CD3 affinity is a promising method to improve the therapeutic index of T-cell-engaging bispecific antibodies.

scholarly journals Potent and selective antitumor activity of a T cell-engaging bispecific antibody targeting a membrane-proximal epitope of ROR1

2018 ◽  
Vol 115 (24) ◽  
pp. E5467-E5476 ◽  
Author(s):  
Junpeng Qi ◽  
Xiuling Li ◽  
Haiyong Peng ◽  
Erika M. Cook ◽  
Eman L. Dadashian ◽  
...  
Keyword(s):  
T Cell ◽  
Antitumor Activity ◽  
Tumor Cells ◽  
T Cell Activation ◽  
Cell Activation ◽  
Ex Vivo ◽  
3D Structure ◽  
X Ray Crystallography

T cell-engaging bispecific antibodies (biAbs) present a promising strategy for cancer immunotherapy, and numerous bispecific formats have been developed for retargeting cytolytic T cells toward tumor cells. To explore the therapeutic utility of T cell-engaging biAbs targeting the receptor tyrosine kinase ROR1, which is expressed by tumor cells of various hematologic and solid malignancies, we used a bispecific ROR1 × CD3 scFv-Fc format based on a heterodimeric and aglycosylated Fc domain designed for extended circulatory t1/2 and diminished systemic T cell activation. A diverse panel of ROR1-targeting scFv derived from immune and naïve rabbit antibody repertoires was compared in this bispecific format for target-dependent T cell recruitment and activation. An ROR1-targeting scFv with a membrane-proximal epitope, R11, revealed potent and selective antitumor activity in vitro, in vivo, and ex vivo and emerged as a prime candidate for further preclinical and clinical studies. To elucidate the precise location and engagement of this membrane-proximal epitope, which is conserved between human and mouse ROR1, the 3D structure of scFv R11 in complex with the kringle domain of ROR1 was determined by X-ray crystallography at 1.6-Å resolution.

scholarly journals Modulation of temozolomide dose differentially affects T-cell response to immune checkpoint inhibition

2019 ◽  
Vol 21 (6) ◽  
pp. 730-741 ◽  
Author(s):  
Aida Karachi ◽  
Changlin Yang ◽  
Farhad Dastmalchi ◽  
Elias J Sayour ◽  
Jianping Huang ◽  
...  
Keyword(s):  
T Cell ◽  
Immune Checkpoint ◽  
Standard Dose ◽  
Antibody Therapy ◽  
Tumor Infiltrating Lymphocytes ◽  
T Cell Response ◽  
Checkpoint Inhibition ◽  
Immune Checkpoint Inhibition ◽  
Dose Modulation ◽  
Infiltrating Lymphocytes

Abstract Background The changes induced in host immunity and the tumor microenvironment by chemotherapy have been shown to impact immunotherapy response in both a positive and a negative fashion. Temozolomide is the most common chemotherapy used to treat glioblastoma (GBM) and has been shown to have variable effects on immune response to immunotherapy. Therefore, we aimed to determine the immune modulatory effects of temozolomide that would impact response to immune checkpoint inhibition in the treatment of experimental GBM. Methods Immune function and antitumor efficacy of immune checkpoint inhibition were tested after treatment with metronomic dose (MD) temozolomide (25 mg/kg × 10 days) or standard dose (SD) temozolomide (50 mg/kg × 5 days) in the GL261 and KR158 murine glioma models. Results SD temozolomide treatment resulted in an upregulation of markers of T-cell exhaustion such as LAG-3 and TIM-3 in lymphocytes which was not seen with MD temozolomide. When temozolomide treatment was combined with programmed cell death 1 (PD-1) antibody therapy, the MD temozolomide/PD-1 antibody group demonstrated a decrease in exhaustion markers in tumor infiltrating lymphocytes that was not observed in the SD temozolomide/PD-1 antibody group. Also, the survival advantage of PD-1 antibody therapy in a murine syngeneic intracranial glioma model was abrogated by adding SD temozolomide to treatment. However, when MD temozolomide was added to PD-1 inhibition, it preserved the survival benefit that was seen by PD-1 antibody therapy alone. Conclusion The peripheral and intratumoral immune microenvironments are distinctively affected by dose modulation of temozolomide.

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