Checkpoint Blockade Inhibitors Research Articles

Abstract LB113: Immunogenicity of Atezolizumab plus personalized neoantigen vaccination (PGV-001) in patients with urothelial cancer in adjuvant vs metastatic setting

Abstract Background: Urothelial cancer (UC) of the genitourinary tract, most commonly arising from the bladder, has historically been a challenging area for the development of new therapeutics. Immune checkpoint blockade inhibitors (CBIs) induce durable responses only in a subset of patients with UC, potentially due to lack of neoantigen primed T cells. To build on this hypothesis, we designed a study to evaluate safety and immunogenicity of a combination treatment with atezolizumab and PGV-001, a personalized genomic neoantigen vaccine. Having previously reported clinical outcomes, here we describe analysis of immunogenicity induced by the treatment. Methods: In this phase I trial (NCT03359239) UC patients were enrolled to receive PGV-001 with atezolizumab in the adjuvant (undergone radical cystectomy or nephroureterectomy with a high risk of recurrence) or metastatic setting. Each PGV001 vaccine included up to 10 neoantigen (predicted using OpenVax pipeline) synthetic long peptides (SLPs). Each subject received 10 PGV-001 vaccines and 1200 mg i.v. atezolizumab every 3 weeks for up to 12 months (adjuvant) or 24 months (metastatic). To investigate T cell immunity, ex vivo IFNγ ELISPOT and T cell expansion assays were performed using 15mer overlapping peptide (OLP) pools corresponding to each neoantigen SLP. Results: Samples from 9 subjects (3 adjuvant and 6 metastatic) were evaluable for ex vivo ELISPOT analysis. In 100% of the subjects, at least 1 neoantigen was found to elicit an immune response. Overall, out of 87 evaluated neoantigens, 47% were immunogenic, with the immunogenic peptides inducing an average of 16.7 fold increase in ex vivo ELISPOT response over baseline. While 39% (11/28) of the peptides in adjuvant cohort were immunogenic vs 51% (39/50) in metastatic cohort, it is not possible to determine statistically significant difference in response between metastatic and adjuvant cohort. The T cell expansion assay was performed for 6 subjects, 3 each from the adjuvant and metastatic cohorts. Among 57 evaluated neoantigens, 46% and 54% of the peptides elicited a CD8+ and CD4+ T cell targeted immune response, respectively. A greater proportion of neoantigens induced both CD8+ and CD4+ T cell responses in subjects treated in the metastatic setting vs adjuvant setting. Upon epitope mapping, for 5 evaluable subjects, 141 OLPs were analyzed and a similar number of OLPs were found to be immunogenic for CD8+ (31.2%, 44/141) and CD4+ response (30%, 43/141). Conclusions: These data indicate that vaccination with personalized neoantigens in combination with systemic anti-PD-L1 can induce neoantigen-focused T cell responses in both adjuvant and metastatic disease settings. However, the single arm nature of the trial, and sample size, preclude definitive assessment of the contribution of the components of the combination therapy. Future studies will investigate the efficacy of this approach on a larger scale with pre- and on-treatment analyses of treatment-driven immunomodulation. Citation Format: Mansi Saxena, Jonathan Anker, Julia Kodysh, Timothy O'Donnell, Marcia Meseck, Olivia Hapanowicz, Scot Niglio, Hardik Shah, Yayoi Kinoshita, Rachel Brody, Alex Rubinsteyn, Robert Sebra, Nina Bhardwaj, Mathew Galsky. Immunogenicity of Atezolizumab plus personalized neoantigen vaccination (PGV-001) in patients with urothelial cancer in adjuvant vs metastatic setting [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB113.

Abstract 3721: EZH2 inhibition enhances PD-L1 protein stability through USP22-mediated deubiquitination in colorectal cancer

Abstract The regulation of PD-L1 is the key question which largely determines the outcome of the immune checkpoint inhibitors (ICIs) based therapy. The epigenetic mechanism is involved in transcriptional regulation towards PD-L1. However, besides the transcription level, the protein stability of PD-L1 is closely correlated to its function and has drawn more and more attention. In this study, EZH2 inhibition could enhance PD-L1 expression and protein stability, and the deubiquitinase ubiquitin-specific peptidase 22 (USP22) is identified as a key mediator in this process. EZH2 inhibition upregulates the expression of USP22 via canonical mechanism, and upregulated USP22 further stabilize PD-L1. Importantly, a combination of EZH2 inhibitors with anti-PD-1 immune checkpoint blockade therapy could improve the tumor microenvironment, promotes immune cell infiltration, enhances sensitivity to immunotherapy and exerts synergistic anti-cancer effects. In addition, knocking down USP22 could potentially enhance the therapeutic efficacy of EZH2 inhibitor on colon cancer. These findings unveil the novel role of EZH2 inhibitors (EZH2i) in tumor immune evasion by upregulating PD-L1. Although it may be one reason of EZH2i inefficacy due to the fact that it elicits the immune suppressive effect, appropriately utilizing this drawback to arouse PD-L1 expression may convert the tumor into more responsive upon ICI cancer therapy. In addition, the EZH2-USP22-PD-L1 regulatory axis could further facilitating to identify populations sensitive to immunotherapy or provide novel strategy for combined treatment. Therefore, these findings provide valuable insights into the intricate interplay between EZH2 and PD-L1, shedding light on the optimization of combining both immune checkpoint blockade and EZH2 inhibitor based epigenetic therapies to achieve more efficacies and accuracy in cancer treatment. Citation Format: Jianling Yang, Jiaqi Huang, Qianqian Yin, Lixiang Xue. EZH2 inhibition enhances PD-L1 protein stability through USP22-mediated deubiquitination in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3721.

New insights into the role of mast cells as a therapeutic target in cancer through the blockade of immune checkpoint inhibitors.

Mast cells release different anti-and pro-inflammatory agents changing their role from protective to pro-inflammatory cells involved in the progression of different pathological conditions, including autoimmune diseases and tumors. Different mediators released by mast cells are involved in their biological activities which may be anti-tumorigenic and/or pro-tumorigenic. For these reasons, tumor mast cells have been considered a novel therapeutic target to prevent tumor progression and metastatic process. Many different agents have been suggested and used in the past pre-clinical and clinical settings. Among the novel immunotherapeutic approaches to cancer treatment, different immune checkpoint inhibitors targeting PD-1/PDL-1 have been used in the treatment of many human tumors improving overall survival. In this context, inhibition of mast cell activity may be considered a novel strategy to improve the efficacy of anti-PD-1/PDL-1 therapy. The blockade of the PD-1/PD-L1 interaction may be suggested as a useful and novel therapeutic approach in the treatment of tumors in which mast cells are involved.

Immune cell infiltrates in peritoneal metastases from colorectal cancer.

The presence of peritoneal metastases (PMs) in patients with colorectal cancer (CRC) confers a poor prognosis and only a minority of patients will benefit from the available treatment options. In primary CRC tumors, it is well established that a high infiltration of CD8+ effector T cells correlates to a favorable patient outcome. In contrast, the immune response induced in PMs from CRC and how it relates to patient survival is still unknown. In this study, we characterized the immune infiltrates and the distribution of immune checkpoint receptors on T cells from PMs from CRC, in order to evaluate the potential benefit of checkpoint blockade immunotherapy for this patient group. Surgically resected PM tissue from CRC patients (n=22) and synchronous primary tumors (n=8) were processed fresh to single cell suspensions using enzymatic digestion. Surface markers and cytokine production were analyzed using flow cytometry. T cells dominated the leukocyte infiltrate in the PM specimens analyzed, followed by monocytes and B cells. Comparing two different PMs from the same patient usually showed a similar distribution of immune cells in both samples. The T cell infiltrate was characterized by an activated phenotype and markers of exhaustion were enriched compared with matched circulating T cells, in particular the checkpoint receptors PD-1 and TIGIT. In functional assays most cytotoxic and helper T cells produced INF-γ and TNF following polyclonal stimulation, while few produced IL-17, indicating a dominance of Th1-type responses in the microenvironment of PMs. Immune cells were present in all PMs from CRC examined. Although infiltrating T cells express markers of exhaustion, they produce Th1-type cytokines when stimulated. These results indicate the possibility to augment tumor-specific immune responses within PMs using checkpoint blockade inhibitors.

Immune checkpoint blockade combined with targeted therapies to provide disease control in mismatch repair-proficient colorectal cancer with peritoneal metastases.

133 Background: Metastatic colorectal adenocarcinoma (mCRC) with proficient mismatch repair (pMMR) is associated with poor response to cytotoxic chemotherapy in the refractory setting, with a median overall survival (OS) of 10.8 months. Recent immunotherapy (IO) regimens utilizing a combination of immune checkpoint blockade (ICB) and tyrosine kinase inhibitors (TKIs) that suppress tumor-associated macrophages (TAMs) have shown promise for extra-hepatic, but not hepatic metastases. However, few studies include patients with peritoneal metastases (PMs) and the response rate of PMs to these therapies is unknown. We sought to examine the disease control rates (DCR) and OS of patients treated with PM who were treated with ICB regimens. Methods: Patients with pMMR tumors treated with ICB and TKI after progression on 1st and 2nd-line therapy from 2015 to 2022 were identified. Date of start of therapy, end of therapy, last follow up and vital status were determined from the medical record. Radiographic disease response within each metastasis site at 6 months and at last follow-up on therapy was determined for each patient. Overall survival was estimated using the Kaplan-Meier method. Results: A total of 93 patients treated with an ICB and TKI after at least two lines of cytotoxic systemic therapy were identified. Five were excluded due to dMMR/MSI-H status and eight due to lack of follow-up. A total of 33 patients with PM, with or without other metastases, had a median follow-up on therapy of 6.1 months and median follow-up until death or censoring of 9.8 months. Median OS was 15.1 (9.7-29.5) months, and 18-month survival was 43% (95%CI: 24-62%). OS was not associated with either BRAF (HR 0.98, 0.38-2.6, p=0.98) or RAS (HR 1.50, 0.62- 3.63, p=0.37) mutation status. Partial response of PM was noted in 5 patients (15%), stable disease in 14 (42%) and progressive disease in 14 (42%), resulting in DCR of 57%. Disease control for all metastatic sites was noted in 9 (27%) of patients, and median OS was not reached at 2 years. Median OS for patients without peritoneal progression was 22.0 months [12.3-NR], and PM progression was associated with worse OS (HR 0.66, p=0.024). A total of 32 patients with any metastatic site were treated for at least 6 months. Median follow-up was 16.1 months for this cohort. DCR at 6 months for CRLM was 23% (3/13), PM was 58% (14/24, p=0.08 vs CRLM) and for LM was 62% (8/13, p=0.11 vs CRLM). Conclusions: Response to ICB and targeted therapy combinations can vary widely by metastatic site, with liver trending towards less response than peritoneum or lung. Disease control in the peritoneum can be achieved in the majority of patients, and median OS compares favorably to standard-of-care therapy in the refractory setting. Patients with peritoneal disease should be included in future trials of ICBs as treatment options are otherwise limited.

Primary retroperitoneal choriocarcinoma with lung and liver metastasis in a male patient: case report

Abstract Objectives Non-gestational primary choriocarcinoma is an extremely rare malignant tumor with atypical clinical symptoms, especially in males. It usually occurs in the midline of the body, such as the mediastinum and retroperitoneum. Pathological diagnosis of primary retroperitoneal choriocarcinoma presents many challenges. More importantly, it is insensitive to therapy and has a poor prognosis. To date, there is still no standard treatment strategy for primary choriocarcinoma. Case presentation This case report presented a 27-year-old male with acute abdominal pain as the main symptom. And then, retroperitoneal choriocarcinoma with lung and liver metastasis was diagnosed. Palliative surgery was performed to alleviate the abdominal pain but complete tumor removal was not achieved. Subsequently, we gave the treatment with cytotoxic chemotherapy and immune checkpoint inhibitor blockade. The tumor was significantly reduced in size after six cycles of immunotherapy and chemotherapy, and also β-hCG level returned to normal. The tumor was not in complete remission, so penpulimab immuno-maintenance therapy was given. So far, the tumor control is stable, and the patient’s quality of life is also very well. Conclusions Pathological diagnosis of primary choriocarcinoma is very necessary, and the related molecular markers can assist. Immunotherapy combined with chemotherapy is effective in the treatment of primary retroperitoneal choriocarcinoma.

CAR T-Cell-Based Combination Therapy for Pancreatic Ductal Adenocarcinoma (PDAC)

It is projected that by 2030, following the lung cancer, pancreatic cancer will rank among the deadliest cancers. Because of the limited initial symptoms and early diagnosis, PDAC has one of the most dismal prognosis among all types of malignancies. Therefore, it is crucial to develop promising treatments for PDAC cases. Genetically engineering the T lymphocytes to express designed chimeric antigen receptors (CAR) is an emerging direction, but the major hindrance is the complex tumor microenvironment (TME) that restricts its performance. This review paper discusses the existing combinations between CAR T-cell and other therapies, the challenges, and future improvements in promoting the therapeutic outcomes of PDAC. Multiple chemotherapeutic drugs remodel the complicated TME to upregulate the potency of T cells. Some radiotherapies augment tumor-associated antigen expression to increase the anticancer activities. Additionally, the cytotoxicity of the engineered T cells is enhanced by checkpoint inhibitor blockade (CPB). Oncolytic viruses (OVs) represent another novel approach in CAR T-cell combination. OVs stimulate cytokines, which then trigger the chemokines in CAR-T-cell regulations. Being well-versed in the potential concurrent therapies in CAR T-cell-based manner facilitates researchers in conducting future studies in a more targeted way towards PDAC.

IMMU-38. INTRATUMORAL CORRELATION OF MULTIPLEX IMMUNOFLUORESCENCE AND89ZR-CREFMIRLIMAB BERDOXAM IMMUNOPET IN RECURRENT GBM PATIENTS TREATED WITH NEOADJUVANT ANTI-PD-1 +/- ANTI-CTLA-4 THERAPY

Abstract Glioblastoma (GBM) is a highly aggressive brain tumor that responds poorly to checkpoint blockade inhibitors (ICIs), such as anti-PD-1. We previously reported that neoadjuvant anti-PD-1 therapy activated and recruited T cells into recurrent GBM (rGBM) tumors, but also increased immune checkpoint interactions between T cells and myeloid cells. To overcome this resistance mechanism, we are currently conducting a phase 1B clinical trial of neoadjuvant anti-PD-1 (Nivolumab, BMS) +/- anti-CTLA-4 (Ipilimumab, BMS) combination therapy for rGBM patients (NCT04606316). To evaluate the systemic and local tumor microenvironment effects of these checkpoint inhibitors, we used immuno-positron emission tomography (CD8 immunoPET, 89Zr-crefmirlimab berdoxam, ImaginAb) to track CD8+ T cells in five rGBM patients before and after neoadjuvant anti-PD-1 or combination therapy with anti-CTLA-4, and used multiplex immunofluorescence (mIF) to analyze the intratumoral immune profile of patient-matched tumors. We found that CD8 ImmunoPET imaging could detect physiologic tracer uptake in the lymph node basins and tumor bed prior to and following checkpoint blockade, suggesting a systemic immunometabolic response within the tumor after therapy. Correlation with mIF found that combination therapy (n=1) increased the density of conventional type 1 and 2 dendritic cells (cDC1: CD3-CD141+XCR1+ and cDC2: CD3-CD1c+) in the tumors, especially cDC1, compared to anti-PD-1 monotherapy (n=4) or untreated patients (n=3) (the densities of cDC1 and cDC2 cells were 163 cells/mm2 and 13.3 cells/mm2 respectively). Moreover, combination ICI therapy was associated with enhanced infiltration of CD8+ and CD4+ T cells in the tumor (28.7 cells/mm2 and 73.8 cells/mm2, respectively) with a specific increase in CD4+ T cells compared to anti-PD-1 monotherapy. In summary, preliminary results of the correlation of the longitudinal brain immunoPET imaging with the intratumoral mIF analysis in these five rGBM patients suggests distinct effects of monotherapy vs. combination neoadjuvant anti-PD-1 and anti-CTLA-4 therapy on the intratumoral immunometabolic profile of rGBM patients.

Leveraging efferocytosis blockade for improved cancer chemo-immunotherapy through synchronized release of doxorubicin and BMS777607 confined within tailored mesoporous silica nanoparticles

Effective antitumor activity of chemotherapy can be counterbalanced by efferocytosis by generating immunosuppressive tumor microenvironment. Targeted blocking efferocytosis at an early stage of cell apoptosis exerts promising benefits on achieving improved chemotherapy, but it appears to have considerably limited outcome due to the uncontrolled release of chemotherapeutic and efferocytosis inhibitors. Herein, a mesoporous silica nanoparticle (MSN)-based nanoconfined assembly strategy is created to co-deliver chemotherapeutic drug doxorubicin (DOX) and efferocytosis inhibitor BMS777607 (BMS) for efficient cancer chemo-immunotherapy. DOX and BMS self-assembly forms nanoparticulate crystal confined within the mesopore of tailor-made MSN, and nanocrystal-encapsulated MSN (denoted as SC-MSN@D/B) enables synchronized drug release behaviors, which is beneficial for efferocytosis blockade at the early stage of apoptosis. Consequently, intravenous injection of SC-MSN@D/B leads to a synergistic inhibition of tumor growth in colon and breast cancer models through inducing a stimulatory immune response, from the secretion of pro-inflammatory cytokines to the inhibition of tumor associated macrophages and regulatory T cells infiltration. The combination of SC-MSN@D/B with checkpoint blockade inhibitors further amplifies the therapeutic effect of on tumor growth and pulmonary metastasis of orthotopic 4T1 breast tumors, and establishes long-term immune memory, offering tremendous potential for a combined efferocytosis-blocking strategy in cancer chemo-immunotherapy.

126P Effect of sequential antitumoral treatment with immune checkpoint blockade and tyrosine kinase inhibitors in hepatocellular carcinoma

126P Effect of sequential antitumoral treatment with immune checkpoint blockade and tyrosine kinase inhibitors in hepatocellular carcinoma

Abstract PO-005: Phase 1/2 study of Ad/PNP with fludarabine for the treatment of head & neck squamous cell carcinoma (HNSCC)

Abstract The project pursues clinical testing of a gene-based treatment for refractory malignancy of the head and neck. Background We are evaluating intratumoral nucleoside cleavage by E. coli purine nucleoside phosphorylase (PNP) as an experimental therapy for refractory solid tumors. The approach requires delivery of PNP transgene to tumor parenchyma followed by prodrug administration, and provides “bystander” killing by a very potent purine antimetabolite (F-Ade) generated intratumorally. F-Ade is 1,000-times more potent than fluorouracil, the chemotherapeutic produced by cytosine deaminase (CD; a first-generation construct used for tumor sensitization). PNP/F-Ade has been found to be superior to CD/fluorouracil by several laboratories. In a Phase 1 study (Rosenthal et al., Ann. Oncol.), antitumor activity was observed after IT injections of a recombinant adenovirus encoding PNP (Ad/PNP), followed by IV fludarabine phosphate (F-araAMP, a prodrug converted by PNP to F-Ade). Methods Patients in the present trial have RECIST 1.1 measurable HNSCC amenable to local injection and no other palliative treatment options. A single-arm protocol is being used to evaluate safety of repeat cycles of Ad/PNP and F-araAMP. Ad/PNP is injected intratumorally twice on Day 1 and once on Day 2, followed by infusion of F-araAMP on Days 3, 4, and 5 every 4 weeks for up to 5 cycles. Results Eight patients have been enrolled to date. There have been no dose limiting toxicities, no serious adverse events (SAEs) definitively attributable to treatment, and no AEs above grade 3 severity. Up to five cycles of Ad/PNP treatment have been administered without limiting sequelae. Intratumoral expression of PNP transgene by RT-PCR has been established in treated tumors. Other correlative endpoints are in process and will be discussed. One patient exhibited tumor volume reduction by approximately 21% (as judged by CT imaging) and did not increase during five months of treatment, consistent with clinically stable disease. Two other patients completed three months of Ad/PNP with stable disease by RECIST criteria during the treatment period. Another patient’s tumor (largest dimension 3.1 cm) demonstrated 25% decrease after one treatment cycle. Challenges have included: 1) complexity of distribution of agent into large volume tumors (e.g., >100 ml) with small volume of Ad/PNP, and 2) acute swelling of tumor tissue following intratumoral virus injection in two patients, consistent with inflammatory response and/or disease progression. Conclusions Administration of Ad/PNP is safe and feasible. Injections of large volume tumors remains a challenge. The strategy is also being considered for earlier-stage HNSCC with less tumor burden, including a role similar to neoadjuvant or cytoreductive radiotherapy in combination with checkpoint blockade inhibition. A muti-center trial is planned to define MTD and feasibility in smaller tumors. Citation Format: A. Dimitrios Colevas, Eric J. Sorscher, William B. Parker, Roan Courtney Raymundo, Jeong S. Hong, Regina Rab, Camilo Henao, Nikki Schmitt, Madison Stallings, Kelly T. McKee, Eben Rosenthal, Joseph Curry. Phase 1/2 study of Ad/PNP with fludarabine for the treatment of head & neck squamous cell carcinoma (HNSCC) [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Innovating through Basic, Clinical, and Translational Research; 2023 Jul 7-8; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2023;29(18_Suppl):Abstract nr PO-005.

Targeted delivery of a PD-1-blocking scFv by CD133-specific CAR-T cells using nonviral Sleeping Beauty transposition shows enhanced antitumour efficacy for advanced hepatocellular carcinoma

BackgroundCD133 is considered a marker for cancer stem cells (CSCs) in several types of tumours, including hepatocellular carcinoma (HCC). Chimeric antigen receptor-specific T (CAR-T) cells targeting CD133-positive CSCs have emerged as a tool for the clinical treatment of HCC, but immunogenicity, the high cost of clinical-grade recombinant viral vectors and potential insertional mutagenesis limit their clinical application.MethodsCD133-specific CAR-T cells secreting PD-1 blocking scFv (CD133 CAR-T and PD-1 s cells) were constructed using a sleeping beauty transposon system from minicircle technology, and the antitumour efficacy of CD133 CAR-T and PD-1 s cells was analysed in vitro and in vivo.ResultsA univariate analysis showed that CD133 expression in male patients at the late stage (II and III) was significantly associated with worse progression-free survival (PFS) (P = 0.0057) and overall survival (OS) (P = 0.015), and a multivariate analysis showed a trend toward worse OS (P = 0.041). Male patients with advanced HCC exhibited an approximately 20-fold higher PD-L1 combined positive score (CPS) compared with those with HCC at an early stage. We successfully generated CD133 CAR-T and PD-1 s cells that could secrete PD-1 blocking scFv based on a sleeping beauty system involving minicircle vectors. CD133 CAR-T and PD-1 s cells exhibited significant antitumour activity against HCC in vitro and in xenograft mouse models. Thus, CD133 CAR-T and PD-1 s cells may be a therapeutically tractable strategy for targeting CD133-positive CSCs in male patients with advanced HCC.ConclusionsOur study provides a nonviral strategy for constructing CAR-T cells that could also secrete checkpoint blockade inhibitors based on a Sleeping Beauty system from minicircle vectors and revealed a potential benefit of this strategy for male patients with advanced HCC and high CD133 expression (median immunohistochemistry score > 2.284).

T Cells in Colorectal Cancer: Unravelling the Function of Different T Cell Subsets in the Tumor Microenvironment.

Therapeutic options for metastatic colorectal cancer (mCRC) are very limited, and the prognosis using combination therapy with a chemotherapeutic drug and a targeted agent, e.g., epidermal growth factor receptor or tyrosine kinase, remains poor. Therefore, mCRC is associated with a poor median overall survival (mOS) of only 25-30 months. Current immunotherapies with checkpoint inhibitor blockade (ICB) have led to a substantial change in the treatment of several cancers, such as melanoma and non-small cell lung cancer. In CRC, ICB has only limited effects, except in patients with microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) tumors, which comprise about 15% of sporadic CRC patients and about 4% of patients with metastatic CRC. The vast majority of sporadic CRCs are microsatellite-stable (MSS) tumors with low levels of infiltrating immune cells, in which immunotherapy has no clinical benefit so far. Immunotherapy with checkpoint inhibitors requires the presence of infiltrating T cells into the tumor microenvironment (TME). This makes T cells the most important effector cells in the TME, as evidenced by the establishment of the immunoscore-a method to estimate the prognosis of CRC patients. The microenvironment of a tumor contains several types of T cells that are anti-tumorigenic, such as CD8+ T cells or pro-tumorigenic, such as regulatory T cells (Tregs) or T helper 17 (Th17) cells. However, even CD8+ T cells show marked heterogeneity, e.g., they can become exhausted, enter a state of hyporesponsiveness or become dysfunctional and express high levels of checkpoint molecules, the targets for ICB. To kill cancer cells, CD8+ T cells need the recognition of the MHC class I, which is often downregulated on colorectal cancer cells. In this case, a population of unconventional T cells with a γδ T cell receptor can overcome the limitations of the conventional CD8+ T cells with an αβT cell receptor. γδ T cells recognize antigens in an MHC-independent manner, thus acting as a bridge between innate and adaptive immunity. Here, we discuss the effects of different T cell subsets in colorectal cancer with a special emphasis on γδ T cells and the possibility of using them in CAR-T cell therapy. We explain T cell exclusion in microsatellite-stable colorectal cancer and the possibilities to overcome this exclusion to enable immunotherapy even in these "cold" tumors.

Radiation in Combination with Immune Checkpoint Blockade and DNA Damage Response Inhibitors in Mice: Dosage Optimization in MC38 Syngeneic Tumors via Modelling and Simulation.

Clinical trials assessing the impact of radiotherapy (RT) in combination with DNA damage response pathway inhibitors (DDRis) and/or immune checkpoint blockade are currently ongoing. However, current methods for optimizing dosage and schedule are limited. A mathematical model was developed to capture the impacts of RT in combination with DDRi and/or anti-PD-L1 [immune checkpoint inhibitor (ICI)] on tumor immune interactions in the MC38 syngeneic tumor model. The model was fitted to datasets that assessed the impact of RT in combination with the DNA protein kinase inhibitor (DNAPKi) AZD7648. The model was further fitted to datasets from studies that were used to assess both RT/ICI combinations as well as RT/ICI combinations followed by concurrent administration of the poly ADP ribose polymerase inhibitor (PARPi) olaparib. Nonlinear mixed-effects modeling was performed followed by internal validation with visual predictive checks (VPC). Simulations of alternative dosage regimens and scheduling were performed to identify optimal candidate dosage regimens of RT/DNAPKi and RT/PARPi/ICI. Model fits and VPCs confirmed a successful internal validation for both datasets and demonstrated very small differences in the median, lower, and upper percentile values of tumor diameters between RT/ICI and RT/PARPi/ICI, which indicated that the triple combination of RT/PARPi/ICI at the given dosage and schedule does not provide additional benefit compared with ICI in combination with RT. Simulation of alternative dosage regimens indicated that lowering the dosage of ICI to between 2 and 4 mg/kg could induce similar benefits to the full dosage regimen, which could be of translational benefit. SIGNIFICANCE STATEMENT: This work provides a mixed-effects model framework to quantify the effects of combination radiotherapy/DNA damage response pathway inhibitors/immune checkpoint inhibitors in preclinical tumor models and identify optimal dosage regimens, which could be of translational benefit.

Molecular predictors and immunomodulatory role of dual checkpoint inhibitor blockade using ipilimumab/nivolumab in patients with extensive stage small cell lung cancer.

8597 Background: Small cell lung cancer (SCLC) is an aggressive neuroendocrine carcinoma with poor prognosis. In extensive stage patients, frontline treatment with chemoimmunotherapy shows modest clinical benefit. However, the biological impact of immunotherapy in SCLC is poorly understood with no clear predictive biomarkers to guide patient selection in this setting. Methods: We collected paired baseline (pre-treatment), on-treatment (week 4), and progression biopsies from patients with relapsed advanced-stage SCLC treated with combination nivolumab (nivo) and ipilimumab (ipi) in a single-arm, phase 2 clinical trial (NCT03670056). Nivo 1 mg/kg and ipi 3 mg/kg were administered every 3 weeks for 4 cycles, followed by nivo maintenance until progressive disease (PD) by RECIST 1.1 or treatment-limiting toxicity. Paired pre/on-treatment samples were available from 16/22 patients, as well as 3 biopsies at progression. The tumor samples were studied using whole exome DNA sequencing (including germline DNA) and RNA-sequencing coupled to Ocean Genomics TxomeAI data analysis pipeline. Results: 6/11 evaluable patients had PD; 5 patients showed clinical activity of treatment (3 with stable disease, 2 with partial response). The frequency of deleterious mutations in TP53 and RB1 was 91% and 64%, respectively. Mutations in HLA-A were more common in baseline samples from patients with PD than those with clinical activity. New TP53 and PLEC mutations were found 4 of 6 patients with PD in week 4 samples vs baseline. The baseline tumor mutational burden was not associated with treatment sensitivity and prominently increased in week 4 biopsies of PD patients. All four molecular SCLC transcriptomic subtypes based on the expression of ASCL1, NEUROD1, and POU2F3 were present in the trial with SCLC-A being the most common (9/16 cases). All patients with clinical activity to ipi/nivo were of SCLC-A subtype. 2/16 of cases showed a different molecular subtype after 4 weeks of treatment: one case with SCLC-N switched to SCLC-A and another case converted from SCLC-A to SCLC-N. Comparison of baseline and on-treatment samples showed upregulation of transcripts associated with T-cell activation and PD-1 signaling. In the 3 biopsies at progression, transcriptomic changes included reduction of neutrophil degranulation, type 1/2 interferon and signatures, as well as down-regulation of β-2 microglobulin, while cell cycle and mitotic prophase pathways were overexpressed. Conclusions: Dual checkpoint blockade using nivo/ipi has a prominent immunomodulatory role in extensive stage SCLC characterized by increased local adaptive immune responses, reduced HLA class-I antigen presentation and change in the molecular subtype in a subset of cases. We identified genomic features associated with treatment sensitivity/resistance. Clinical trial information: NCT03670056 .

Tuning peptide specificity for T cell tolerance in Type 1 diabetes

Abstract Type 1 Diabetes (T1D) is a classical T-cell mediated autoimmune disease, and fundamental data have implicated insulin as the dominant autoantigen in T1D disease. In the NOD mouse model of T1D, notable studies have found that mice lacking native insulin expression but with an altered insulin sequence to maintain blood glucose levels are protected from insulitis and diabetes. Growing evidence also indicates how the insulin peptide is bound within MHC Class II (peptide register) is essential in determining the strength of interactions and recognition of autoreactive T-cells. We have uncovered a unique peptide binding characterized by the dominant insulin epitope InsB:9–23. The majority of InsB:9–23-specific CD4 T-cells in the periphery recognize insulin bound in the unusual register 3, and knocking in this single amino acid variation into just one copy of the insulin gene in NOD mice, confers protection against T1D. In addition, these mice were protected from T1D, even when treated with checkpoint inhibitor blockade, unlike their wild-type littermates. Introducing this superagonist epitope into the NOD mouse has allowed us to address several key questions surrounding pathways of peptide generation, presentation by MHC molecules, and recognition by auto-reactive pathogenic T cells. In addition, we have been able to model how central and peripheral tolerance mechanisms can be altered when major epitopes in the Insulin gene are mutated, allowing us to explore means of dominant tolerance to understand the potential for translation into treatments for T1D. Supported by grants from NIH (R01 DK133443-01A)

Tunable B cell response through allosteric modulation of Bruton’s tyrosine kinase

Abstract The B cell receptor (BCR) is essential for both the initial burst of B cell proliferation in response to antigens, and for the differentiation of plasma cells and memory B cells during germinal center reactions. However, the BCR’s precise role in germinal center selection has been difficult to assess: mechanistic investigations into its modulation during the decision of B cell fate suffer from experimental limitations due to the fundamental role of the BCR in B cell biology. Bruton’s tyrosine kinase (BTK), a member of the TEC family, is a key component of BCR signaling. Using a computational screening method based on small molecule docking outside of the BTK active site, we have identified putative allosteric modulators of BTK. In vitro primary B cell Nur77 upregulation, calcium flux, proliferation and plasma cell differentiation confirmed that these molecular probes alter B cell activation strength, kinetics, and fate only when the BCR is engaged. In vivo immunization using an antigen model reveled that BTK agonism strongly favors B cell differentiation into switched plasma cells. BTK agonism, either at the time of the immunization or at the peak of germinal center formation, enhanced humoral immunity, proving for the first time that transient, augmented BCR signaling during germinal center reaction has a direct impact on B cell differentiation ability. In addition to being powerful tools for basic B cell biology investigation, allosteric agonists of BTK could be developed into antigen-licensed B cell adjuvants for vaccines in at risk populations, as well as into cancer immunotherapy drugs which hyperactivate B cells in tumor microenvironments during checkpoint inhibitor blockade therapies.

Clinical guideline highlights for the hospitalist: Management of immune-related adverse events in patients treated with immune checkpoint inhibitor therapy.

Management of Immune-Related Adverse Events in Patients Treated with Immune Checkpoint Inhibitor Therapy: ASCO Guideline Update RELEASE DATE: November 1, 2021 PRIOR VERSION(S): February 14, 2018 DEVELOPER: American Society of Clinical Oncology FUNDING SOURCE: American Society of Clinical Oncology TARGET POPULATION: Adult patients with cancer receiving treatment with immune checkpoint blockade inhibitors alone.

Abstract 6414: Concomitant anti-tumor immunity and checkpoint blockade responses are restored by depletion of CD62L expressing cells

Abstract Studies have shown the importance of CD62L in leukocyte trafficking. However, the significance of CD62L-expressing cells in concomitant anti-tumor immunity has not been investigated. Using a model of post-surgical tumor immunity, we show that in vivo depletion of CD62L-expressing cells before or immediately after surgical tumor resection enabled the development of anti-tumor concomitant responses against poorly immunogenic B16 (melanoma) or MTE-Ras (head & neck cancer) tumor cells. Anti-CD62L mAb administration depleted the cellular immune components that express CD62L, including NK, NKT, Mo, Ma, B, and T cells. Within the T cell compartment, naïve T cells (CD44lo CD62Lhi), effector (CD44hi CD62Llo), memory (CD44hi CD62Lhi) and regulatory T cells (Treg, CD4 CD25 Foxp3) were also depleted, while effector CD62L-negative T cells were spared in the TDLN. Tumor immunity did not occur in the absence of a primary tumor (sham surgery group) or after CD8 depletion. Whereas anti-CTLA-4 or anti-PD-1 mAbs failed as monotherapies, their administration during CD62L depletion restored their anti-tumor properties. The unified global gene expression analysis of the TDLN shows the significant enrichment of biological processes involved in the CD8 T cell effector phase, IL-2/IL-15, TNF-α, IFN-γ, IFN-α, IL-6, responses, mitotic cell division, glycolysis, and acetylation. Also, genes related to Treg responses were downregulated. These data point to a process in which depletion of CD62L cells in tumor-bearing hosts transforms the TDLN into a highly active immunological site in which tumor-reactive effector CD8 T cells (CD62L-negative) actively divide in the absence of Treg, accompanied by a cytokine response, glucose consumption, and acetylation of transcriptional factors and histones. These results identify an unrecognized role of CD62L-expressing cells in regulating concomitant anti-tumor immunity and restoring anti-tumor responses by checkpoint blockade inhibitors. Our study provides a new framework that could help understand how anti-tumor responses are limited. Citation Format: Brianna Burke, Lourdes Plaza-Rojas, Cynthia Perez, Elena Kostenko, Anna Austin, Justin Boucher, Kushal Prajapati, Michael Delos Reyes, Christine Chung, Jose-Alejandro Guevara-Patino. Concomitant anti-tumor immunity and checkpoint blockade responses are restored by depletion of CD62L expressing cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6414.

Abstract 896: Investigating tissue-resident memory T cell differentiation of CAR T cells reveals an unexpected role for CD69

Abstract Adoptive cell therapy using chimeric antigen receptor-expressing (CAR) CD8+ T cells has revolutionized the treatment of liquid tumors; however, CAR T cells have had more limited success against solid tumors. The tumor microenvironment can impair T cell function within solid tumors through a variety of mechanisms, including nutrient deprivation, hypoxia, and recruitment of immuno-suppressive cells. CD8+ tissue-resident memory T cells (Trm), which are characterized by surface expression of CD69 and CD103 and a unique transcription factor circuit, are found within solid tumors, important for tumor surveillance, and responsive to checkpoint inhibitor blockade. However, it is unclear whether CAR T cells adopt Trm features in the tumor microenvironment and how the nature of the CAR costimulatory domain could impact Trm differentiation and efficacy against solid tumors. To investigate Trm differentiation in solid tumors, we utilized murine the MC38 syngeneic graft tumor model and found three populations of tumor-infiltrating CD8+ T lymphocytes: CD69-CD103-, CD69+CD103- and CD69+CD103+. CD69+ populations downregulated circulating T cells genes and expressed Trm signature genes often found in non-tumor Trm cells. To examine if tumor infiltrating CAR T cells follow a similar differentiation pattern, human carcinoembryonic antigen (hCEA)-specific CAR T cells with either a CD28 or 4-1BB costimulatory domain were transferred into hosts bearing MC38-hCEA tumors. hCEA-CD28 CAR T cells accumulated in the tumor, while hCEA-41BB CAR T cells and T cells without a CAR were present at much lower numbers. hCEA-CD28 CAR T cells displayed delayed Trm differentiation with an increased proportion of CD69-CD103- cells when compared to hCEA-41BB CAR T cells or T cells without a CAR. While hCEA-CD28 CAR signaling drove T cell accumulation, there was significant heterogeneity in the degree of T cell expansion, and the size of CD69-CD103- population correlated strongly with the number of hCEA-CD28 CAR T cells within the tumor. CD69-CD103- hCEA-CD28 CAR T cells were more proliferative and expressed lower levels of surface markers associated with dysfunction, including PD-1 and LAG3. These observations suggested CD69 could be a negative regulator of T cell proliferation and function. Indeed, deletion of CD69 in hCEA-CD28 CAR T cells further enhanced proliferation, which resulted in greater numbers of CAR T cells in tumor. In summary, hCEA-CD28 CAR signaling prolonged T cell proliferation in solid tumors by delaying Trm differentiation and the upregulation of CD69, whose expression impairs T cell proliferation. Citation Format: Menglin Cheng, Tessa Bergsbaken. Investigating tissue-resident memory T cell differentiation of CAR T cells reveals an unexpected role for CD69 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 896.