Citations

Abstract PD-L1/PD-1 receptor pathway represents an important way of cancer cells to escape immune surveillance, yet only small portions of patients can benefit from PD-1/PD-L1 inhibitors. This is at least partially due to incomplete understanding of PD-1/PD-L1 biology in cancer. Although the interaction of extracellular domains between PD-L1 and PD-1 on cancer cells and immune cells is well studied, the function of PD-L1 inside cells, however, has not been well established. In our previous data, we found that intracellular PD-L1 acts as an RNA binding protein and interacts with NBS1 and BRCA1 mRNAs. Furthermore, intracellular PD-L1 protects targeted RNAs from degradation by RNA exosome, therefore increasing cellular resistance to DNA damage. Since Clinical approved PD-1/PD-L1 inhibitors have little effect on intracellular PD-L1, we sought to find new drugs to target intracellular PD-L1. Here we developed a new PD-L1 antibody, H1A, which has a different effect on PD-L1. Instead of blocking of PD-1/PD-L1 interaction, we found that this antibody disrupts the interaction of PD-L1 and CMTM6, which leads to degradation of PD-L1 by the lysosome. Therefore, H1A can unleash host antitumor activity and enhance the effects of DNA damaging therapy in cancer cells at the same time. Indeed, applying H1A in vivo significantly sensitized tumors to radiation and chemotherapy in a PDX models. Moreover, in a humanized immune competent TNBC PDX model, H1A monotherapy exhibited better therapeutic efficacy compared with clinically available PD-L1 inhibitor, suggesting that H1A activates anti-tumor immunity through PD-L1 degradation. Therefore, H1A may be a potential new drug to target both intracellular and extracellular PD-L1 to improve cancer therapy.

Abstract Aging is considered to be a major risk factor for host morbidity and mortality upon acute respiratory virus infections. To better elucidate the immune determinants of viral pathogenesis during aging, we chronological characterized lung cellular and molecular profiles following influenza virus (PR8) infection in young or aged mice till 60 days post infection. Time-course scRNAseq coupled with high dimensional flow cytometry enabled the description of changes in both immune and stromal compartment between young and aged hosts. We further zoomed into the myeloid compartment and focused on the dynamic responses of lung macrophages given their complex roles in viral pathogenesis, tissue repair and lung fibrosis. Enlarged Monocyte-derived Macrophage (MoM) population as well as decreased resident-Alveolar Macrophage (AM) population were observed in the aged mice when compared to those of the young mice. Despite the self-sustain nature of AMs during homeostasis, it has been reported that Ly6Chi monocytes can gain AM identity following severe lung damage like influenza virus infection. We found that the gain of AM identity from monocytes was abrogated in the aged hosts, which likely contributed to the age-associated impairment in lung recovery after influenzas virus infection. Additionally, trajectory analysis with scRNAseq allowed us to identify IFNα/γ signaling to be potential pathways contributing to such defect. This notion is also supported by elevated IFNγ level in BAL from the aged host during lung recovery. Our results thus have improved our understanding on the cellular and molecular mechanisms by which aged hosts exhibit severe diseases and delayed recovery after respiratory viral infection.

Abstract Immune related adverse events (irAEs) from immune checkpoint inhibitors (ICIs) are well documented for nearly every organ system, except for the reproductive system. Mouse models have demonstrated that ICIs can decrease ovarian follicular reserve and impair oocyte maturation, which may have implications for fertility (PMID: 36008687). There are no studies investigating the effect of ICIs on fertility in humans. We sought to evaluate ovarian function in women treated with ICIs compared to untreated women by evaluating non-invasive surrogate markers of ovarian reserve, anti-müllerian hormone (AMH) and antral follicle counts (AFC). We enrolled women 18 - 40 years old diagnosed with stage III or IV melanoma. Participants underwent phlebotomy for AMH levels and a pelvic ultrasound to assess AFC. The medical record was retrospectively reviewed to obtain data on patient characteristics, treatments, and outcomes. A total of 14 patients with stage IIIA - IV melanoma participated. Six patients received ICI treatment before AMH and AFC testing while 8 had no prior ICI exposure. The ICI group ages ranged from 22-40 years with a median age of 31 years. The untreated group ages ranged from 25-39 years with a median age of 32 years. The time between starting an ICI and enrolling in the study ranged from 28 - 351 days. ICI regimens included ipilimumab/nivolumab, nivolumab, pembrolizumab, and atezolizumab (on a clinical trial). Four of these six patients experienced an irAE during their course, including: dermatitis, hepatitis, colitis, thyroid dysfunction, and adrenal insufficiency. Median AMH levels were lower for patients treated with ICIs (2.9 vs 4.0 ng/mL), as was median AFC (22.5 vs 23.5 ng/mL). Only three patients’ clinicians discussed fertility preservation. None of the patients underwent fertility preservation. Our study found lower AMH and AFC in women with melanoma who were treated with an ICI compared to untreated women. Although AMH and AFC are surrogate markers for ovarian reserve and fertility, and our study is a small cohort, these early results suggest that ICIs may impact ovarian function. Age is less likely to be a confounding factor as the median age of the treated group was younger than the untreated group. While these results are preliminary, when considered in conjunction with recent pre-clinical data showing changes within the ovaries after ICI treatment, fertility consultation should be considered for young women prior to ICI initiation. We are investigating associations between AMH, AFC, age, ICI exposure, and future pregnancies in an ongoing prospective study. Citation Format: Ashley Hickman, Katherine Smith, Zaraq Khan, Elizabeth Ann Enninga, Yulian Zhao, Elizabeth Cathcart-Rake, Haidong Dong, Lisa Kottschade, Svetomir Markovic, Heather Montane, Anastasios Dimou, Yiyi Yan. Investigating the effect of immune checkpoint inhibitors (ICI) on ovarian function in young patients with melanoma. [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 6644.

9093 Background: Pembrolizumab interrupts PD-1/-L1 interaction and is efficacious in many cancers. However, resistance invariably emerges in the majority of patients. Potential mechanisms include activation of compensatory pathways. The inhibition of sonic hedgehog signaling (sHH) was previously shown to induce intra-tumoral (IT) infiltration by CD4+, CD8+ and HLA-DR class II cells. Our preclinical data showed sHH inhibitor enhanced IT penetration by monoclonal antibodies and induced PD-L1 expression. We conducted a phase I study using a novel sequential pulse dosing of sonedegib followed by pembrolizumab in aST with an expansion cohort to determine the maximum tolerated dose (MTD), tolerability and preliminary efficacy. Methods: The dose escalation utilized a 3+3 design to determine the MTD and proceeded to expansion cohort upon determination of the MTD. Patients enrolled to each dose level were observed for dose limiting toxicities (DLTs) during the 1st cycle. The expansion cohort consisted of NSCLC and head/neck squamous cell carcinoma (HNSCC) previously treated by anti-PD1/-L1. The recommended phase 2 dose (RP2D) was determined following the review of the toxicity profile of the combination from all cycles. The study treatment consisted of sonidegib oral daily from day 1 to 8 and pembrolizumab I.V. 200 mg on day 8 on an every 3-week cycle. The sonidegib dose levels explored were 400, 600 and 800 mg. Archival tumor and blood specimens were collected for correlative studies. Adverse events (AEs) were categorized and graded per CTCAE v5.0, and tumor response by RECIST v1.1. Results: The study enrolled a total of 33 patients and 29 received treatment (13 in escalation and 16 in expansion), including patients with NSCLC, HNSCC, skin cancer, gastric cancer and melanoma. The enrollment to the NSCLC cohort is complete and HNSCC continues. No DLT was encountered during dose escalation and the MTD was not reached. The highest planned dose level was selected to proceed to expansion (sonidegib 800mg days 1-8 in combination with pembrolizumab I.V. 200 mg on day 8 on an every 3-week cycle). The expansion cohort proceeded to enroll 15 patients evaluable for AEs (10 NSCLC and 5 HSNCC). Grade 3 and above treatment-related AEs across all patients were hyperglycemia, fatigue, dyspepsia, abdominal pain. The mature efficacy data will be reported at the meeting. Conclusions: The study successfully determined the RP2D of sonidegib when dosed sequentially with pembrolizumab in advanced solid tumors. The AE profile of the combination is similar to that for respective agents given individually. The efficacy data among anti-PD1/-PDL1-treated NSCLC will be reported at the meeting. Clinical trial information: NCT04007744 .

Abstract The intrinsic and acquired resistance to PD-1/PD-L1 immune checkpoint blockade is an important challenge for patients and clinicians because no reliable tool has been developed to predict individualized response to immunotherapy. In this study, we demonstrate the translational relevance of an ex vivo functional assay that measures the tumor cell killing ability of patient-derived CD8 T and NK cells (referred to as “cytotoxic lymphocytes,” or CLs) isolated from the peripheral blood of patients with renal cell carcinoma. Patient-derived PBMCs were isolated before and after nephrectomy from patients with renal cell carcinoma. We compared the efficacy of U.S. Food and Drug Administration (FDA)-approved PD-1/PD-L1 inhibitors (pembrolizumab, nivolumab, atezolizumab) and a newly developed PD-L1 inhibitor (H1A Ab) in eliciting cytotoxic function. CL activity was improved at 3 mo after radical nephrectomy compared with baseline, and it was associated with higher circulating levels of tumor-reactive effector CD8 T cells (CD11ahighCX3CR1+GZMB+). Treatment of PBMCs with FDA-approved PD-1/PD-L1 inhibitors enhanced tumor cell killing activity of CLs, but a differential response was observed at the individual-patient level. H1A demonstrated superior efficacy in promoting CL activity compared with FDA-approved PD-1/PD-L1 inhibitors. PBMC immunophenotyping by mass cytometry revealed enrichment of effector CD8 T and NK cells in H1A-treated PBMCs and immunosuppressive regulatory T cells in atezolizumab-treated samples. Our study lays the ground for future investigation of the therapeutic value of H1A as a next-generation immune checkpoint inhibitor and the potential of measuring CTL activity in PBMCs as a tool to predict individual response to immune checkpoint inhibitors in patients with advanced renal cell carcinoma.

Abstract Although cancer burden in patients with advanced diseases results in T cell exhaustion and failed prior therapies, some of them achieved durable clinical responses to salvage therapy (chemotherapy or radiation therapy) implying a presence of tumor-reactive resilient T cells in them. However, the phenotype and functional features of resilient T cells have not been clearly defined. We found that CX3CR1+ CD8+ T cells with low mitochondrial membrane potential demonstrated features of resilient T cells: (a) their cytotoxic T cell function (degranulation/CD107a expression) recovered quickly after tumor burden has been reduced by radiation therapy or chemotherapy; (b) they maintain a low profile of glycolysis but produce optimal levels of ATP; (c) they express lower levels of PD-1 and TOX; (4) they share a feature of stem-like T cells (TCF1+PD-1+) that can be responsive to immunotherapy; (5) they avoid accumulation of a harmful level of cytosolic reactive oxygen species (ROS) that may cause T cell exhaustion; (6) they upregulate malic enzyme 1 (ME1) to balance glycolysis and ROS, and to expand cytotoxic effector T cells. These unique features of resilient T cells may not only be used as T cell biomarker to design rational combination therapy to control advanced cancers but can also be used to convey a resilient functional state to T cells in patients who lack them. Citation Format: Joanina K. Gicobi, Yiyi Yan, Hu Zeng, Sean Park, Haidong Dong. Characterization of cytotoxic resilient T cells in patients with advanced cancers in response to salvage radiation therapy or chemotherapy. [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 4160.

548 Background: PD-L1 and B7-H3 have been found to be overexpressed in urothelial carcinoma (UC) of the urinary bladder. Recent studies have also demonstrated that B7-H3 and PD-L1 can promote resistance to platinum-based drugs but the predictive value of B7-H3 expression in patients treated with platinum-based chemotherapy is unknown. This study aims to investigate the association of PD-L1 and B7-H3 tumor expression with oncological outcomes in patients who underwent radical cystectomy (RC) and received subsequent adjuvant chemotherapy. Methods: Immunohistochemistry was performed on paraffin-embedded sections from bladder and lymph node specimens of 81 patients who had RC for bladder cancer. PD-L1 and B7-H3 expression on tumor cells was assessed by immunohistochemistry in both primary tumors and lymph node specimens. Association with clinicopathologic outcomes was determined using Fisher’s exact test and postoperative survival using Kaplan–Meier survival curves and Cox regression model. Results: B7-H3 expression in cystectomy specimens was more common than PD-L1 expression (72.8% vs. 35.8%). For both markers, no association was found with pathologic tumor stage, lymph node (LN) status, and histological subtype. Similar findings were observed for double-positive tumors (PD-L1+B7-H3+). Concordance between the primary tumor and patient-matched lymph nodes was found in 76.2% and 54.1% of patients for PD-L1 and B7-H3, respectively. PD-L1 tumor expression was not associated with oncologic outcomes. However, B7-H3 expression was associated with recurrence-free survival (HR: 2.38, 95% CI 1.06–5.31, p = 0.035) and cancer-specific survival (HR: 2.67, 95% CI 1.18–6.04, p = 0.019). Conclusions: In our single institutional study, B7-H3 is highly expressed in patients with UC treated with adjuvant chemotherapy and it was associated with decreased recurrence-free survival and cancer-specific survival. Pending further validation in larger cohorts, B7-H3 expression may function as a predictor of response to adjuvant chemotherapy and thus be useful in patient and regimen selection.

Abstract Checkpoint blockade has improved patient outcome through reinvigorating T cells against cancer. Despite this success, many patients don’t respond, leaving them with few options. Tumors utilize many immunosuppressive mechanisms, including altering the function of innate immune cells. Cancer cells can promote differentiation of macrophages into tolerogenic “M2-like” macrophages, which support tumor growth. Macrophage differentiation by cancer cells is influenced by many receptors, including Siglec-E. Siglec-E binds to α2,8-linked disialic acids, generated by the enzyme ST8Sia6, on O-linked glycoproteins, and functions to inhibit activation of innate immune cells. In some tumor types, higher expression of ST8Sia6 correlates with poorer survival. Therefore, ST8Sia6 overexpressing tumors may engage Siglec-E, leading to immune suppression and accelerating tumor growth. Mice injected with ST8Sia6 overexpressing MC38 and B16-F10 tumors had increased tumor burden, reduced survival and increased M2 macrophage polarization, which suppresses the immune response. This acceleration of tumor growth was abrogated when injected into Siglec-E knockout mice. Thus, the primary function of ST8Sia6 in tumors is an extrinsic alteration of the immune response, rather than an intrinsic effect on cell growth. Similarly, in a spontaneous colon cancer model, ST8Sia6 overexpression in a murine colon cancer model accelerated the development of tumors, decreasing survival to 2.5 months instead of 6 months. The overexpression of ST8Sia6 leads to increased Arg-1 expression by colonic tumor macrophages. Therefore, ST8Sia6 expression in tumors inhibits the immune response to promote tumor growth in a Siglec-E dependent manner.

Abstract The immune responses to anti-PD-1 therapy in cancer patients are not completely defined due to lack of reliable biomarkers that identifies responsive and functional T cells. Bim, a molecule of the Bcl-2 family, was recently identified as a downstream signaling molecule of PD-1 pathway in CD8+ T cells and has both pro-apoptotic and effective roles in CD8 T cells. Our clinical data shown that high level of Bim in CD8+ T cells (before checkpoint blockade) was predictive of response in metastatic melanoma whereas in colorectal cancer, low level of Bim was associated with treatment response. Using co-immunoprecipitation, high resolution microscopy and FRET we identified ANT2 (Adenine Nucleotide Translocase 2, an inner membrane protein of mitochondria) as a protein interacting with Bim. Accordingly, we found CD8+ T cells with low and high mitochondrial potential demonstrated different ANT2/Bim ratio, and high ANT2/Bim ratio fall in effector T cells with low mitochondrial potential but high cytotoxic activity. Given the pro-survival of ANT2, our results indicate that ANT2 may function to balance the pro-apoptotic and effective role of Bim in mitochondria in order to preserve effector T cells before contraction. Understanding the molecular mechanism of Bim and ANT2 interaction in CD8+ T cells may provide a novel marker to identify resilient CD8+ T cells responsive to anti-PD-1 therapy, and predict clinical response to the therapy.

TPS780 Background: Pancreatic adenocarcinoma is an aggressive malignancy with a limited number of therapeutic options. One subset of patients (up to 15%) carries germline and/or somatic mutations in homologous recombination repair genes, most notably BRCA1, BRCA2 and PALB2 amongst others, that confer sensitivity to PARP inhibition. Combinations of PARP inhibitors with anti-PD1 immunotherapy have shown activity in breast and ovarian cancer and have not yet been thoroughly studied in pancreatic cancer. Methods: We designed a single-arm phase 2 investigator-initiated study utilizing the combination of niraparib, a highly selective PARP inhibitor and a dostarlimab, an anti PD1 antibody, in the subset of pancreatic cancer patients with germline or somatic mutations in BRCA1/2, PALB2, BARD1, RAD51C, or RAD51D. Additional inclusion criteria include metastatic pancreatic adenocarcinoma, receipt of a platinum agent in 1st or 2nd line unless contraindicated, and at least 1 but not more than 2 prior lines of systemic therapy not including maintenance. Prior PARP inhibition is allowed, but not immediately prior to enrollment. Exclusion criteria include active unstable autoimmune disease or prior malignancy requiring active treatment within 2 years. Patients are treated with niraparib 200 mg orally once daily on days 1 through 21 of a 21 day cycle. Dostarlimab is administered IV 500 mg every 3 weeks for the 1st 4 cycles and then 1000 mg IV every 6 weeks subsequently. The primary endpoint of the study is the disease control rate at 12 weeks using standard iRECIST criteria. Twenty patients will be enrolled to ensure 19 evaluable. The design has 80% power to detected improvement in disease control rate from 25-50% with significance level of 0.10. Descriptive factors include gene mutated for inclusion, germline/somatic, and platinum refractoriness. Given the size of the study along with genetic heterogeneity there will be no interim analysis. Patients are being enrolled at 3 Mayo clinic sites in Rochester Minnesota, Phoenix Arizona, Jacksonville Florida. To date, 13 patients have been enrolled across all 3 sites. Full accrual is anticipated by early 2023. Correlative studies include genomic characterization of baseline tumors, assessment of immune infiltration of tumor microenvironment, tumor collection for organoid/xenograft, and serial circulating cell-free DNA and immune biomarkers. Trial Identifiers: NCT04493060, Mayo: MC1841. Supported by Glaxo Smith Kline. Clinical trial information: NCT04493060 .