ICOS costimulation in combination with CTLA-4 blockade remodels tumor-associated macrophages toward an antitumor phenotype

We have previously demonstrated synergy between ICOS costimulation (IVAX; ICOSL-transduced B16-F10 cellular vaccine) and CTLA-4 blockade in antitumor therapy. In this study, we employed CyTOF and single-cell RNA sequencing and observed significant remodeling of the lymphoid and myeloid compartments in combination therapy. Compared with anti-CTLA-4 monotherapy, the combination therapy enriched Th1 CD4 T cells, effector CD8 T cells, and M1-like antitumor proinflammatory macrophages. These macrophages were critical to the therapeutic efficacy of anti-CTLA-4 combined with IVAX or anti-PD-1. Macrophage depletion with clodronate reduced the tumor-infiltrating effector CD4 and CD8 T cells, impairing their antitumor functions. Furthermore, the recruitment and polarization of M1-like macrophages required IFN-γ. Therefore, in this study, we show that there is a positive feedback loop between intratumoral effector T cells and tumor-associated macrophages (TAMs), in which the IFN-γ produced by the T cells polarizes the TAMs into M1-like phenotype, and the TAMs, in turn, reshape the tumor microenvironment to facilitate T cell infiltration, immune function, and tumor rejection.

The future of targeting cytotoxic T-lymphocyte-associated protein-4: Is there a role?

The 2022 yearly Think Tank Meeting in Siena, Tuscany (Italy), organized by the Italian Network for Tumor Biotherapy (NIBIT) Foundation, the Parker Institute for Cancer Immunotherapy and the World Immunotherapy Council, included a focus on the future of integrating and expanding the use of targeting cytotoxic T-lymphocyte-associated protein 4 (CTLA-4). The conference members exchanged their views on the lessons from targeting CTLA-4 and compared the effect to the impact of blocking Programmed cell death protein 1 (PD1) or its ligand (PDL1). The increasing experience with both therapeutic approaches and their combination suggests that targeting CTLA-4 may lead to more durable responses for a sizeable proportion of patients, though the specific mechanism is not entirely understood. Overcoming toxicity of blocking CTLA-4 is currently being addressed with different doses and dose regimens, especially when combined with PD1/PDL1 blocking antibodies. Novel therapeutics targeting CTLA-4 hold the promise to reduce toxicities and thus allow different combination strategies in the future. On the whole, the consent was that targeting CTLA-4 remains an important strategy to improve the efficacy of cancer immunotherapies.

Exercise Training Reduces the Inflammatory Response and Promotes Intestinal Mucosa-Associated Immunity in Lynch Syndrome

PURPOSE

Lynch syndrome (LS) is a hereditary condition with a high lifetime risk of colorectal and endometrial cancers. Exercise is a non-pharmacologic intervention to reduce cancer risk, though its impact on patients with LS has not been prospectively studied. Here, we evaluated the impact of a 12-month aerobic exercise cycling intervention in the biology of the immune system in LS carriers.

PATIENTS AND METHODS

To address this, we enrolled 21 patients with LS onto a non-randomized, sequential intervention assignation, clinical trial to assess the effect of a 12-month exercise program that included cycling classes 3 times weekly for 45 minutes versus usual care with a one-time exercise counseling session as control. We analyzed the effects of exercise on cardiorespiratory fitness, circulating, and colorectal-tissue biomarkers using metabolomics, gene expression by bulk mRNA sequencing, and spatial transcriptomics by NanoString GeoMx.

RESULTS

We observed a significant increase in oxygen consumption (VO2peak) as a primary outcome of the exercise and a decrease in inflammatory markers (prostaglandin E) in colon and blood as the secondary outcomes in the exercise versus usual care group. Gene expression profiling and spatial transcriptomics on available colon biopsies revealed an increase in the colonic mucosa levels of natural killer and CD8+ T cells in the exercise group that were further confirmed by IHC studies.

CONCLUSIONS

Together these data have important implications for cancer interception in LS, and document for the first-time biological effects of exercise in the immune system of a target organ in patients at-risk for cancer.

Inflammation induced by tumor-associated nerves promotes resistance to anti-PD-1 therapy in cancer patients and is targetable by interleukin-6 blockade

While the nervous system has reciprocal interactions with both cancer and the immune system, little is known about the potential role of tumor associated nerves (TANs) in modulating anti-tumoral immunity. Moreover, while peri-neural invasion is a well establish poor prognostic factor across cancer types, the mechanisms driving this clinical effect remain unknown. Here, we provide clinical and mechniastic association between TANs damage and resistance to anti-PD-1 therapy. Using electron microscopy, electrical conduction studies, and tumor samples of cutaneous squamous cell carcinoma (cSCC) patients, we showed that cancer cells can destroy myelin sheath and induce TANs degeneration. Multi-omics and spatial analyses of tumor samples from cSCC patients who underwent neoadjuvant anti-PD-1 therapy demonstrated that anti-PD-1 non-responders had higher rates of peri-neural invasion, TANs damage and degeneration compared to responders, both at baseline and following neoadjuvant treatment. Tumors from non-responders were also characterized by a sustained signaling of interferon type I (IFN-I) - known to both propagate nerve degeneration and to dampen anti-tumoral immunity. Peri-neural niches of non-responders were characterized by higher immune activity compared to responders, including immune-suppressive activity of M2 macrophages, and T regulatory cells. This tumor promoting inflammation expanded to the rest of the tumor microenvironment in non-responders. Anti-PD-1 efficacy was dampened by inducing nerve damage prior to treatment administration in a murine model. In contrast, anti-PD-1 efficacy was enhanced by denervation and by interleukin-6 blockade. These findings suggested a potential novel anti-PD-1 resistance drived by TANs damage and inflammation. This resistance mechanism is targetable and may have therapeutic implications in other neurotropic cancers with poor response to anti-PD-1 therapy such as pancreatic, prostate, and breast cancers.

Immune checkpoint therapy-current perspectives and future directions

Immune checkpoint therapy (ICT) has dramatically altered clinical outcomes for cancer patients and conferred durable clinical benefits, including cure in a subset of patients. Varying response rates across tumor types and the need for predictive biomarkers to optimize patient selection to maximize efficacy and minimize toxicities prompted efforts to unravel immune and non-immune factors regulating the responses to ICT. This review highlights the biology of anti-tumor immunity underlying response and resistance to ICT, discusses efforts to address the current challenges with ICT, and outlines strategies to guide the development of subsequent clinical trials and combinatorial efforts with ICT.

Abstract 4149: Anti-CTLA-4 generates memory T-cells with greater expansion and functionality than anti-PD-1

Blocking either cytotoxic T-lymphocyte antigen-4 (CTLA-4) or programmed cell death-1 (PD-1) pathway relieves the negative regulation of T-cells resulting in durable tumor rejection in patients with cancer and improved survival rate. However, it remains unclear how these immunotherapies affect memory T-cell response. Here we address whether anti-CTLA-4 and anti-PD-1 have different effects on memory T-cells. We used anti-CTLA-4 or anti-PD-1 therapy in combination with irradiated cancer vaccine in mice. After re-challenge, we observed that in murine tumor models, anti-CTLA-4 generates a more robust memory antitumor response than anti-PD-1 as demonstrated by smaller tumor volumes at all time points. We have traced and profiled antigen-specific CD8 T-cells throughout priming, memory phase, and re-challenge. We observed the memory responses generated by anti-CTLA-4 and anti-PD-1 diverge at priming; where anti-CTLA-4 generates more TCF-1+ memory-like T-cells than anti-PD-1, and remains apparent throughout activation and expansion as anti-PD-1 results in a higher percentage of TOX1+ terminally-differentiated T cells. During re-challenge, the memory T-cells generated by anti-CTLA-4 1) expand in greater frequency, 2) have greater cytokine production and antitumor activity, and 3) more frequently differentiate into the population of KLRG1+ effector CD8 T-cells than those generated with anti-PD-1. We found each of these traits correlated with a more effective memory response.

Citation Format: Stephen Mok, Nana-Ama A.S. Anang, James J. Mancuso, James P. Allison. Anti-CTLA-4 generates memory T-cells with greater expansion and functionality than anti-PD-1. [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 4149.

Neoadjuvant chemotherapy plus nivolumab with or without ipilimumab in operable non-small cell lung cancer: the phase 2 platform NEOSTAR trial

Neoadjuvant ipilimumab + nivolumab (Ipi+Nivo) and nivolumab + chemotherapy (Nivo+CT) induce greater pathologic response rates than CT alone in patients with operable non-small cell lung cancer (NSCLC). The impact of adding ipilimumab to neoadjuvant Nivo+CT is unknown. Here we report the results and correlates of two arms of the phase 2 platform NEOSTAR trial testing neoadjuvant Nivo+CT and Ipi+Nivo+CT with major pathologic response (MPR) as the primary endpoint. MPR rates were 32.1% (7/22, 80% confidence interval (CI) 18.7-43.1%) in the Nivo+CT arm and 50% (11/22, 80% CI 34.6-61.1%) in the Ipi+Nivo+CT arm; the primary endpoint was met in both arms. In patients without known tumor EGFR/ALK alterations, MPR rates were 41.2% (7/17) and 62.5% (10/16) in the Nivo+CT and Ipi+Nivo+CT groups, respectively. No new safety signals were observed in either arm. Single-cell sequencing and multi-platform immune profiling (exploratory endpoints) underscored immune cell populations and phenotypes, including effector memory CD8⁺ T, B and myeloid cells and markers of tertiary lymphoid structures, that were preferentially increased in the Ipi+Nivo+CT cohort. Baseline fecal microbiota in patients with MPR were enriched with beneficial taxa, such as Akkermansia, and displayed reduced abundance of pro-inflammatory and pathogenic microbes. Neoadjuvant Ipi+Nivo+CT enhances pathologic responses and warrants further study in operable NSCLC. (ClinicalTrials.gov registration: NCT03158129 .).

Intestinal toxicity to CTLA-4 blockade driven by IL-6 and myeloid infiltration

Immune checkpoint blockade (ICB) has revolutionized cancer treatment, yet quality of life and continuation of therapy can be constrained by immune-related adverse events (irAEs). Limited understanding of irAE mechanisms hampers development of approaches to mitigate their damage. To address this, we examined whether mice gained sensitivity to anti-CTLA-4 (αCTLA-4)-mediated toxicity upon disruption of gut homeostatic immunity. We found αCTLA-4 drove increased inflammation and colonic tissue damage in mice with genetic predisposition to intestinal inflammation, acute gastrointestinal infection, transplantation with a dysbiotic fecal microbiome, or dextran sodium sulfate administration. We identified an immune signature of αCTLA-4-mediated irAEs, including colonic neutrophil accumulation and systemic interleukin-6 (IL-6) release. IL-6 blockade combined with antibiotic treatment reduced intestinal damage and improved αCTLA-4 therapeutic efficacy in inflammation-prone mice. Intestinal immune signatures were validated in biopsies from patients with ICB colitis. Our work provides new preclinical models of αCTLA-4 intestinal irAEs, mechanistic insights into irAE development, and potential approaches to enhance ICB efficacy while mitigating irAEs.

Immune checkpoint therapy: Forging ahead

Spatiotemporal immune monitoring in clinical trials and reverse translation will help to determine optimal combination immune therapies to cure cancer.

Neoadjuvant relatlimab and nivolumab in resectable melanoma

Relatlimab and nivolumab combination immunotherapy improves progression-free survival over nivolumab monotherapy in patients with unresectable advanced melanoma1. We investigated this regimen in patients with resectable clinical stage III or oligometastatic stage IV melanoma (NCT02519322). Patients received two neoadjuvant doses (nivolumab 480 mg and relatlimab 160 mg intravenously every 4 weeks) followed by surgery, and then ten doses of adjuvant combination therapy. The primary end point was pathologic complete response (pCR) rate2. The combination resulted in 57% pCR rate and 70% overall pathologic response rate among 30 patients treated. The radiographic response rate using Response Evaluation Criteria in Solid Tumors 1.1 was 57%. No grade 3-4 immune-related adverse events were observed in the neoadjuvant setting. The 1- and 2-year recurrence-free survival rate was 100% and 92% for patients with any pathologic response, compared to 88% and 55% for patients who did not have a pathologic response (P = 0.005). Increased immune cell infiltration at baseline, and decrease in M2 macrophages during treatment, were associated with pathologic response. Our results indicate that neoadjuvant relatlimab and nivolumab induces a high pCR rate. Safety during neoadjuvant therapy is favourable compared to other combination immunotherapy regimens. These data, in combination with the results of the RELATIVITY-047 trial1, provide further confirmation of the efficacy and safety of this new immunotherapy regimen.

T cells specific for α-myosin drive immunotherapy-related myocarditis

Immune-related adverse events, particularly severe toxicities such as myocarditis, are major challenges to the utility of immune checkpoint inhibitors (ICIs) in anticancer therapy1. The pathogenesis of ICI-associated myocarditis (ICI-MC) is poorly understood. Pdcd1-/-Ctla4+/- mice recapitulate clinicopathological features of ICI-MC, including myocardial T cell infiltration2. Here, using single-cell RNA and T cell receptor (TCR) sequencing of cardiac immune infiltrates from Pdcd1-/-Ctla4+/- mice, we identify clonal effector CD8+ T cells as the dominant cell population. Treatment with anti-CD8-depleting, but not anti-CD4-depleting, antibodies improved the survival of Pdcd1-/-Ctla4+/- mice. Adoptive transfer of immune cells from mice with myocarditis induced fatal myocarditis in recipients, which required CD8+ T cells. The cardiac-specific protein α-myosin, which is absent from the thymus3,4, was identified as the cognate antigen source for three major histocompatibility complex class I-restricted TCRs derived from mice with fulminant myocarditis. Peripheral blood T cells from three patients with ICI-MC were expanded by α-myosin peptides. Moreover, these α-myosin-expanded T cells shared TCR clonotypes with diseased heart and skeletal muscle, which indicates that α-myosin may be a clinically important autoantigen in ICI-MC. These studies underscore the crucial role for cytotoxic CD8+ T cells, identify a candidate autoantigen in ICI-MC and yield new insights into the pathogenesis of ICI toxicity.

Abstract 5545: Intestinal toxicity to CTLA-4 blockade driven by IL-6 and myeloid infiltration

Immunotherapies such as anti-CTLA-4 immune checkpoint blockade (ICB) have revolutionized cancer treatment, yet quality of life and continuation of therapy can be constrained by off-target tissue damage or immune-related adverse events (irAEs). At present, there is limited understanding of irAE mechanisms, hampering development of approaches to mitigate their damage. We addressed this problem by generating animal models of intestinal irAE. Our results show that disruption of homeostatic immunity by genetic predisposition to intestinal inflammation or acute gastrointestinal infection sensitizes mice to anti-CTLA-4-mediated intestinal toxicity. Inflammation-prone mice treated with anti-CTLA-4 showed neutrophil accumulation, systemic interleukin-6 (IL-6) release, and dysbiosis. Significantly, IL-6 blockade combined with antibiotic treatment improved anti-CTLA-4 therapeutic efficacy and reduced intestinal irAEs. Immune signatures were validated in biopsies from patients who developed colitis during ICB, supporting the utility of our models. This study provides new pre-clinical models, mechanistic insight into irAEs, and potential approaches to enhance ICB efficacy while mitigating irAEs.

Citation Format: Yifan Zhou, Yusra B. Medik, Bhakti Patel, Daniel B. Zamler, Sijie Chen, Thomas Chapman, Sarah Schneider, Rachel L. Babcock, Taylor T. Chrisikos, Laura M. Kahn, Allison M. Dyevoich, Elizabeth M. Park, Alexandria P. Cogdill, Daniel H. Johnson, Sarah B. Johnson, Khalida M. Wani, Debora A. Ledesma, Courtney W. Hudgens, Jingjing Wang, Md Abdul Wadud Khan, Aron Y. Joon, Weiyi Peng, Haiyan S. Li, Reetakshi Arora, Ximing Tang, Maria Gabriela Raso, Xuegong Zhang, Wai Chin Foo, Michael T. Tetzlaff, Gretchen E. Diehl, Karen Clise-Dwyer, Elizabeth M. Whitley, Matthew M. Gubin, James P. Allison, Patrick Hwu, Nadim J. Ajami, Adi Diab, Jennifer A. Wargo, Stephanie S. Watowich. Intestinal toxicity to CTLA-4 blockade driven by IL-6 and myeloid infiltration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5545.

Abstract 662: Late CTLA-4 Ig treatment improves antitumor efficacy of immunotherapy

The promising approach of combining immune checkpoint therapies such as anti-CTLA-4 and anti-PD-1 increases antitumor response and overall survival rate relative to single treatments. However, it also increases the frequency and severity of immune-related adverse events (irAEs), such as cardiotoxicity. Our previous results showed that CTLA-4 Ig (abatacept), an inhibitor of T cell costimulation through CD28, can reverse those irAEs in patients with cancer, however, its effect on the antitumor response remains unclear. In the B16F10 melanoma model, we injected mice with CTLA-4 Ig antibody when: 1) mice were first treated with anti-CTLA-4, anti-PD-1, or combination (early time point) and 2) the immunotherapy was finished (late time point). We demonstrated that CTLA-4 Ig at the early time point compromised the antitumor efficacy of the immunotherapy. In contrast, the antitumor efficacy of the immunotherapy was improved if mice were treated with CTLA-4 Ig at the late time point. We also found that the antitumor response induced by CTLA-4 Ig (late) was dependent on CD80/86. Interestingly, the frequency of ICOS+ Foxp3+ Tregs was significantly reduced by CTLA-4 Ig at the late time point. Thus, we treated B16F10 tumors in Foxp3DTR mice with anti-CTLA-4 and then with CTLA-4 Ig (late). The antitumor tumor efficacy was similar between mice treated with or without Diphtheria toxin (DT) at the late time point. This suggests that the improved antitumor efficacy of CTLA-4 Ig at the late time point was Treg dependent. Collectively, we show that CTLA-4 Ig treatment has a differential role throughout the time course of immunotherapy treatments, and this work suggests a potential combination treatment strategy with checkpoint blockade and late CTLA-4 Ig treatment.

Citation Format: Stephen Mok, James P. Allison. Late CTLA-4 Ig treatment improves antitumor efficacy of immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 662.

Interleukin-6 blockade abrogates immunotherapy toxicity and promotes tumor immunity

Immune checkpoint blockade (ICB) therapy frequently induces immune-related adverse events. To elucidate the underlying immunobiology, we performed a deep immune analysis of intestinal, colitis, and tumor tissue from ICB-treated patients with parallel studies in preclinical models. Expression of interleukin-6 (IL-6), neutrophil, and chemotactic markers was higher in colitis than in normal intestinal tissue; T helper 17 (Th17) cells were more prevalent in immune-related enterocolitis (irEC) than T helper 1 (Th1). Anti-cytotoxic T-lymphocyte-associated antigen 4 (anti-CTLA-4) induced stronger Th17 memory in colitis than anti-program death 1 (anti-PD-1). In murine models, IL-6 blockade associated with improved tumor control and a higher density of CD4+/CD8+ effector T cells, with reduced Th17, macrophages, and myeloid cells. In an experimental autoimmune encephalomyelitis (EAE) model with tumors, combined IL-6 blockade and ICB enhanced tumor rejection while simultaneously mitigating EAE symptoms versus ICB alone. IL-6 blockade with ICB could de-couple autoimmunity from antitumor immunity.

A phase 1-2 trial of sitravatinib and nivolumab in clear cell renal cell carcinoma following progression on antiangiogenic therapy

The accumulation of immune-suppressive myeloid cells is a critical determinant of resistance to anti-programmed death-1 (PD-1) therapy in advanced clear cell renal cell carcinoma (ccRCC). In preclinical models, the tyrosine kinase inhibitor sitravatinib enhanced responses to anti-PD-1 therapy by modulating immune-suppressive myeloid cells. We conducted a phase 1-2 trial to choose an optimal sitravatinib dose combined with a fixed dose of nivolumab in 42 immunotherapy-naïve patients with ccRCC refractory to prior antiangiogenic therapies. The combination demonstrated no unexpected toxicities and achieved an objective response rate of 35.7% and a median progression-free survival of 11.7 months, with 80.1% of patients alive after a median follow-up of 18.7 months. Baseline peripheral blood neutrophil-to-lymphocyte ratio correlated with response to sitravatinib and nivolumab. Patients with liver metastases showed durable responses comparable to patients without liver metastases. In addition, correlative studies demonstrated reduction of immune-suppressive myeloid cells in the periphery and tumor microenvironment following sitravatinib treatment. This study provides a rationally designed combinatorial strategy to improve outcomes of anti-PD-1 therapy in advanced ccRCC.

Abstract P2-14-14: Durvalumab and tremelimumab before surgery in patients with hormone receptor positive, HER2 negative stage II-III breast cancer

Background: The checkpoint inhibitors atezolizumab (anti-PD-L1) and pembrolizumab (anti-PD-1) are FDA approved for the treatment of patients with PD-L1 positive, metastatic triple negative breast cancer in combination with chemotherapy. The response rates to checkpoint blockade in hormone receptor positive, HER2 negative metastatic breast cancer have been less encouraging (RR 12% for pembrolizumab in KEYNOTE-028 and RR 2.8% for avelumab in the phase 1b trial JAVELIN). We conducted a feasibility trial and enrolled patients with Stage II-III hormone receptor positive, HER2 negative breast cancer to treatment with 2 cycles of durvalumab (anti-PD-L1) plus tremelimumab (anti-CTLA-4) prior to standard neoadjuvant chemotherapy and breast surgery.Methods: Eligible patients were treated with durvalumab at a dose of 1500 mg and tremelimumab at a dose of 75 mg, both administered intravenously, on days 1 and 28. Pre- and post-treatment tumor biopsies and blood samples were available for 5 out of 8 patients and were analyzed by CyTOF, IHC, and NanoString. Patients then received standard neoadjuvant chemotherapy prior to breast surgery. The target enrollment was 20 patients. Results: After 8 patients were enrolled and treated on protocol, the trial was stopped early due to toxicity, slow accrual, and delays in patients receiving standard neoadjuvant chemotherapy. The median age of the patients was 55 (range 39-66) and all 8 patients were women. All patients had ER/PR positive, HER2 negative invasive ductal carcinoma (2 with lobular features, 1 with focal mucinous features) and all patients had clinical Stage II disease. Five patients received both cycles of durvalumab/tremelimumab and the remaining 3 patients only received the first cycle. One patient discontinued therapy out of concern for progression, though repeat breast and lymph node biopsies were benign and she went on to have a pathologic complete response after standard neoadjuvant chemotherapy. The remaining 2 patients discontinued treatment after the first cycle due to Grade 3 colitis (Patient #1) and Grade 3 thyroiditis/adrenal insufficiency (Patient #8). Both patients required treatment with steroids and experienced delays in receiving standard therapy due to these adverse events (AEs). The other AEs reported were all Grade 1 or 2. A post-durvalumab/tremelimumab breast ultrasound was performed in 7 of 8 patients and the percentage change in volume of each patient’s primary breast mass was: -55%, +104% (biopsy benign), +65%, -30%, +90%, -8%, and -53%. Patient #1 (colitis) had chemotherapy administered adjuvantly and Patient #8 (thyroiditis, adrenal insufficiency) declined chemotherapy. Only 1 of 8 patients had a pathologic complete response at the time of surgery. IHC, CYTOF, and gene expression analyses showed an increase in immune cell subsets in tumor stroma post neoadjuvant immunotherapy. Conclusions: We conducted a feasibility trial of neoadjuvant durvalumab plus tremelimumab administered prior to standard neoadjuvant chemotherapy in patients with hormone receptor positive/HER2 negative Stage II or III breast cancer. The trial was stopped early after 2 of 8 patients experienced Grade 3 immune-related adverse events (colitis in 1 patient and thyroiditis/adrenal insufficiency in another patient).

Citation Format: Haven R. Garber, Sreyashi Basu, Sonali Jindal, Akshara Singareeka Raghavendra, Lumarie Santiago, Beatriz E. Adrada, Padmanee Sharma, James P. Allison, Jennifer Litton. Durvalumab and tremelimumab before surgery in patients with hormone receptor positive, HER2 negative stage II-III breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-14-14.

Dietary fiber and probiotics influence the gut microbiome and melanoma immunotherapy response

Gut bacteria modulate the response to immune checkpoint blockade (ICB) treatment in cancer, but the effect of diet and supplements on this interaction is not well studied. We assessed fecal microbiota profiles, dietary habits, and commercially available probiotic supplement use in melanoma patients and performed parallel preclinical studies. Higher dietary fiber was associated with significantly improved progression-free survival in 128 patients on ICB, with the most pronounced benefit observed in patients with sufficient dietary fiber intake and no probiotic use. Findings were recapitulated in preclinical models, which demonstrated impaired treatment response to anti–programmed cell death 1 (anti–PD-1)–based therapy in mice receiving a low-fiber diet or probiotics, with a lower frequency of interferon-γ–positive cytotoxic T cells in the tumor microenvironment. Together, these data have clinical implications for patients receiving ICB for cancer.

Pilot study of Tremelimumab with and without cryoablation in patients with metastatic renal cell carcinoma

Cryoablation in combination with immune checkpoint therapy was previously reported to improve anti-tumor immune responses in pre-clinical studies. Here we report a pilot study of anti-CTLA-4 (tremelimumab) with (n = 15) or without (n = 14) cryoablation in patients with metastatic renal cell carcinoma (NCT02626130), 18 patients with clear cell and 11 patients with non-clear cell histologies. The primary endpoint is safety, secondary endpoints include objective response rate, progression-free survival, and immune monitoring studies. Safety data indicate ≥ grade 3 treatment-related adverse events in 16 of 29 patients (55%) including 6 diarrhea/colitis, 3 hepatitis, 1 pneumonitis, and 1 glomerulonephritis. Toxicity leading to treatment discontinuation occurs in 5 patients in each arm. 3 patients with clear cell histology experience durable responses. One patient in the tremelimumab arm experiences an objective response, the median progression-free survival for all patients is 3.3 months (95% CI: 2.0, 5.3 months). Exploratory immune monitoring analysis of baseline and post-treatment tumor tissue samples shows that treatment increases immune cell infiltration and tertiary lymphoid structures in clear cell but not in non-clear cell. In clear cell, cryoablation plus tremelimumab leads to a significant increase in immune cell infiltration. These data highlight that treatment with tremelimumab plus cryotherapy is feasible and modulates the immune microenvironment in patients with metastatic clear cell histology.

Checkpoint Blockade + Chemotherapy: the Right Combination for AML?

An emerging strategy to enhance the efficacy of immune checkpoint blockade in relapsed/refractory cancers is increasing immunogenic cell death via combination with cytotoxic therapies. Understanding the effects of cytotoxic and immunotherapeutic agents on immune cell populations will enable improved mechanism-based design of combination therapies to maximum efficacy and minimum toxicity.See related article by Zeidner et al., p. 616.

Single cell T cell landscape and T cell receptor repertoire profiling of AML in context of PD-1 blockade therapy

In contrast to the curative effect of allogenic stem cell transplantation in acute myeloid leukemia via T cell activity, only modest responses are achieved with checkpoint-blockade therapy, which might be explained by T cell phenotypes and T cell receptor (TCR) repertoires. Here, we show by paired single-cell RNA analysis and TCR repertoire profiling of bone marrow cells in relapsed/refractory acute myeloid leukemia patients pre/post azacytidine+nivolumab treatment that the disease-related T cell subsets are highly heterogeneous, and their abundance changes following PD-1 blockade-based treatment. TCR repertoires expand and primarily emerge from CD8⁺ cells in patients responding to treatment or having a stable disease, while TCR repertoires contract in therapy^-resistant patients. Trajectory analysis reveals a continuum of CD8⁺ T cell phenotypes, characterized by differential expression of granzyme B and a bone marrow-residing memory CD8⁺ T cell subset, in which a population with stem-like properties expressing granzyme K is enriched in responders. Chromosome 7/7q loss, on the other hand, is a cancer-intrinsic genomic marker of PD-1 blockade resistance in AML. In summary, our study reveals that adaptive T cell plasticity and genomic alterations determine responses to PD-1 blockade in acute myeloid leukemia.

Combined CTLA-4 and PD-L1 blockade in patients with chemotherapy-naïve metastatic castration-resistant prostate cancer is associated with increased myeloid and neutrophil immune subsets in the bone microenvironment

BACKGROUND

Immune checkpoint therapy (ICT) has low response rates in patients with metastatic castration-resistant prostate cancer (mCRPC), in part due to few T cells in the tumor microenvironment (TME). Anti-cytotoxic T lymphocyte-associated protein 4 (CTLA-4) promotes intratumoral T cell infiltration but induces upregulation of PD-1 and programmed death ligand-1 (PD-L1) within the prostate TME. Combined anti-CTLA-4 plus anti-PD-1 can partly overcome this adaptive resistance and was recently shown to augment responses in patients with mCRPC with measurable disease. Although bone is the most common site of metastasis in prostate cancer, patients with bone-predominant disease are frequently excluded from trials because they lack measurable disease, which limits assessment of disease progression and tissue sampling. We therefore designed this study to investigate combined ICT in mCRPC to bone.

HYPOTHESIS

Combined anti-CTLA-4 (tremelimumab) plus anti-PD-L1 (durvalumab) is safe and well tolerated in patients with chemotherapy-naïve mCRPC to bone.

PATIENTS AND METHODS

In this single-arm pilot study, men with chemotherapy-naïve mCRPC to bone received tremelimumab (75 mg intravenous) plus durvalumab (1500 mg intravenous) every 4 weeks (up to four doses), followed by durvalumab (1500 mg intravenous) maintenance every 4 weeks (up to nine doses). The primary endpoint was incidence of adverse events. Secondary endpoints included serum prostate-specific antigen (PSA), progression-free survival (PFS), radiographic PFS (rPFS), and maximal PSA decline.

RESULTS

Twenty-six patients were treated between August 8, 2017 and March 28, 2019. Grade ≥3 treatment-related adverse events (TRAEs) occurred in 11 patients (42%), with no grade 4 or 5 events. TRAEs leading to discontinuation occurred in three patients (12%). PSA decline ≥50% occurred in three patients (12%). Six patients (24%) achieved stable disease for >6 months. At a median follow-up of 43.6 months, median rPFS was 3.7 months (95% CI: 1.9 to 5.7), and median overall survival was 28.1 months (95% CI: 14.5 to 37.3). Post-treatment evaluation of the bone microenvironment revealed transcriptional upregulation in myeloid and neutrophil immune subset signatures and increased expression of inhibitory immune checkpoints.

CONCLUSIONS

Tremelimumab plus durvalumab was safe and well tolerated in patients with chemotherapy-naïve mCRPC to bone, with potential activity in a small number of patients as measured by rPFS. Combination of CTLA-4 and PD-L1 blockade with therapies targeting the myeloid compartment or other inhibitory immune receptors may be necessary to overcome mechanisms of resistance within prostate bone microenvironment.

TRIAL REGISTRATION NUMBER

NCT03204812.

Pilot Phase II Trial of Neoadjuvant Immunotherapy in Locoregionally Advanced, Resectable Cutaneous Squamous Cell Carcinoma of the Head and Neck

PURPOSE

In locoregionally advanced, resectable cutaneous squamous cell carcinoma of the head and neck (CSCC-HN), surgery followed by radiotherapy is standard but can be cosmetically and functionally devastating, and many patients will have recurrence.

PATIENTS AND METHODS

Newly diagnosed or recurrent stage III-IVA CSCC-HN patients amenable to curative-intent surgery received two cycles of neoadjuvant PD-1 inhibition. The primary endpoint was ORR per RECIST 1.1. Secondary endpoints included pathologic response [pathologic complete response (pCR) or major pathologic response (MPR; ≤10% viable tumor)], safety, DSS, DFS, and OS. Exploratory endpoints included immune biomarkers of response.

RESULTS

Of 20 patients enrolled, 7 had recurrent disease. While only 6 patients [30%; 95% confidence interval (CI), 11.9-54.3] had partial responses by RECIST, 14 patients (70%; 95% CI, 45.7-88.1) had a pCR (n = 11) or MPR (n = 3). No SAEs ocurred during or after the neoadjuvant treatment. At a median follow-up of 22.6 months (95% CI, 21.7-26.1), one patient progressed and died, one died without disease, and two developed recurrence. The 12-month DSS, DFS, and OS rates were 95% (95% CI, 85.9-100), 89.5% (95% CI, 76.7-100), and 95% (95% CI, 85.9-100), respectively. Gene expression studies revealed an inflamed tumor microenvironment in patients with pCR or MPR, and CyTOF analyses demonstrated a memory CD8+ T-cell cluster enriched in patients with pCR.

CONCLUSIONS

Neoadjuvant immunotherapy in locoregionally advanced, resectable CSCC-HN is safe and induces a high pathologic response rate. Pathologic responses were associated with an inflamed tumor microenvironment.

Gut microbiota signatures are associated with toxicity to combined CTLA-4 and PD-1 blockade

Treatment with combined immune checkpoint blockade (CICB) targeting CTLA-4 and PD-1 is associated with clinical benefit across tumor types, but also a high rate of immune-related adverse events. Insights into biomarkers and mechanisms of response and toxicity to CICB are needed. To address this, we profiled the blood, tumor and gut microbiome of 77 patients with advanced melanoma treated with CICB, with a high rate of any ≥grade 3 immune-related adverse events (49%) with parallel studies in pre-clinical models. Tumor-associated immune and genomic biomarkers of response to CICB were similar to those identified for ICB monotherapy, and toxicity from CICB was associated with a more diverse peripheral T-cell repertoire. Profiling of gut microbiota demonstrated a significantly higher abundance of Bacteroides intestinalis in patients with toxicity, with upregulation of mucosal IL-1β in patient samples of colitis and in pre-clinical models. Together, these data offer potential new therapeutic angles for targeting toxicity to CICB.

LILRB4 suppresses immunity in solid tumors and is a potential target for immunotherapy

Immune receptors expressed on TAMs are intriguing targets for tumor immunotherapy. In this study, we found inhibitory receptor LILRB4 on a variety of intratumoral immune cell types in murine tumor models and human cancers, most prominently on TAMs. LILRB4, known as gp49B in mice, is a LILRB family receptor. Human and murine LILRB4 have two extracellular domains but differ in the number of intracellular ITIMs (three versus two). We observed a high correlation in LILRB4 expression with other immune inhibitory receptors. After tumor challenge, LILRB4^−/− mice and mice treated with anti-LILRB4 antibody showed reduced tumor burden and increased survival. LILRB4^−/− genotype or LILRB4 blockade increased tumor immune infiltrates and the effector (Teff) to regulatory (Treg) T cell ratio and modulated phenotypes of TAMs toward less suppressive, CD4⁺ T cells to Th1 effector, and CD8⁺ T cells to less exhausted. These findings reveal that LILRB4 strongly suppresses tumor immunity in TME and that alleviating that suppression provides antitumor efficacy.

First-in-Human Phase I Study of ABBV-085, an Antibody-Drug Conjugate Targeting LRRC15, in Sarcomas and Other Advanced Solid Tumors

PURPOSE

Leucine-rich repeat containing 15 (LRRC15) is expressed on stromal fibroblasts in the tumor microenvironment of multiple solid tumor types and may represent an interesting target for therapy, particularly in patients with sarcomas where LRRC15 is also expressed by malignant cells. ABBV-085 is a monomethyl auristatin-E antibody-drug conjugate that targets LRRC15 and showed antineoplastic efficacy in preclinical experiments. Herein, we report findings of ABBV-085 monotherapy or combination therapy in adult patients with sarcomas and other advanced solid tumors.

PATIENTS AND METHODS

This first-in-human phase I study (NCT02565758) assessed ABBV-085 safety, pharmacokinetics/pharmacodynamics, and preliminary antitumor activity. The study consisted of two parts: dose escalation and dose expansion. ABBV-085 was administered by intravenous infusion at 0.3 to 6.0 mg/kg every 14 days.

RESULTS

In total, 85 patients were enrolled; 45 patients received the recommended expansion dose of 3.6 mg/kg ABBV-085 monotherapy, including 10 with osteosarcoma and 10 with undifferentiated pleomorphic sarcoma (UPS). Most common treatment-related adverse events were fatigue, nausea, and decreased appetite. The overall response rate for patients with osteosarcoma/UPS treated at 3.6 mg/kg was 20%, including four confirmed partial responses. No monotherapy responses were observed for other advanced cancers treated at 3.6 mg/kg. One patient treated with ABBV-085 plus gemcitabine achieved partial response.

CONCLUSIONS

ABBV-085 appeared safe and tolerable at a dose of 3.6 mg/kg every 14 days, with preliminary antitumor activity noted in patients with osteosarcoma and UPS. Given the high unmet need in these orphan malignancies, further investigation into targeting LRRC15 in these sarcomas may be warranted.

A Genetic Mouse Model Recapitulates Immune Checkpoint Inhibitor-Associated Myocarditis and Supports a Mechanism-Based Therapeutic Intervention

Immune checkpoint inhibitors (ICI) targeting CTLA4 or PD-1/PD-L1 have transformed cancer therapy but are associated with immune-related adverse events, including myocarditis. Here, we report a robust preclinical mouse model of ICI-associated myocarditis in which monoallelic loss of Ctla4 in the context of complete genetic absence of Pdcd1 leads to premature death in approximately half of mice. Premature death results from myocardial infiltration by T cells and macrophages and severe ECG abnormalities, closely recapitulating the clinical and pathologic hallmarks of ICI-associated myocarditis observed in patients. Using this model, we show that Ctla4 and Pdcd1 functionally interact in a gene dosage-dependent manner, providing a mechanism by which myocarditis arises with increased frequency in the setting of combination ICI therapy. We demonstrate that intervention with CTLA4-Ig (abatacept) is sufficient to ameliorate disease progression and additionally provide a case series of patients in which abatacept mitigates the fulminant course of ICI myocarditis. SIGNIFICANCE: We provide a preclinical model of ICI-associated myocarditis which recapitulates this clinical syndrome. Using this model, we demonstrate that CTLA4 and PD-1 (ICI targets) functionally interact for myocarditis development and that intervention with CTLA4-Ig (abatacept) attenuates myocarditis, providing mechanistic rationale and preclinical support for therapeutic clinical studies.See related commentary by Young and Bluestone, p. 537.This article is highlighted in the In This Issue feature, p. 521.

CTLA-4 blockade synergizes with cryoablation to mediate tumor rejection

We report that cryoablation of primary tumors synergizes with anti-CTLA-4 treatment to mediate rejection of secondary tumors in the TRAMP mouse model of prostate cancer. T cells, in particular CD8⁺ T cells specific for the TRAMP antigen SPAS-1, were enriched in both secondary tumors and spleens of combination-treated mice.

Abstract PR003: Single-cell profiling of acute myeloid leukemia (AML) and its microenvironment reveals a CD8 continuum and adaptable T cell plasticity in response to PD-1 blockade-based therapy

Introduction: Allogeneic hematopoietic stem cell transplantation (ASCT) remains the only curative option for patients with relapsed/refractory (R/R) AML, achieved via the grafted T cells versus leukemia effect. Since ASCT is not viable option to many AML patients, our group investigated (NCT02397720) whether T cells can be harnessed to eradicate R/R AML by combining azacitidine, a hypomethylating agent, and nivolumab, a PD-1 blocker. The tumor microenvironment (TME) factors impacting response and resistance to PD-1 blockade-based treatment in AML is unknown. Methods: We performed single cell RNA sequencing (scRNAseq) of 13,633 healthy bone marrow (BM) donor, and 113,394 BM cells, paired with >30,000 single cell T cell receptor (scTCR) repertoires, from 22 aspirates (8 pre- and 14 post- treatment) from 8 R/R AML patients (median age 73 years) treated with azacitidine/nivolumab. 3/8 patients were responders, while 2/8 and 3/8 had stable disease, and no response, respectively. Results: We identified marked variation in the T cell components across AML patients at pre- and post- treatment, demonstrating significant dynamic changes in CD4, CD8 and non-classical T cells populations, including mucosal associated invariant T (MAIT) cells. Among CD8 cells, we identified a unique GZMK-enriched population that was higher at pretreatment in responders compared to non-responders. Pseudotemporal trajectory analysis revealed a continuum of CD8 cell states that is intermediated by the less exhausted, GZMK-enriched CD8 population. We similarly identified GZMK to discriminate between 2 MAIT populations. Further characterization of GZMK-enriched cells revealed increased expression of the stem-like T cell transcription factor TCF7, and the T cell memory transcription factor EOMES. Pathway enrichment of the 33 overlapping genes in the GZMK-enriched CD8 and MAIT versus cytotoxic T lymphocyte (CD8 CTL) signatures demonstrated highest enrichment for pathways involved in leukocyte differentiation, calcium signaling, and cytokine production. scTCR clonotype assessment revealed more shared clonotypes with the terminally effector CD8 CTL cells following PD-1 blockade. Following treatment, novel clones represented 38.7% (39/101) of total clones, followed by contracted clones (32.6%) and expanded (28.7%) clones. However, 76.9% and 72.4% of novel and expanded clones were contributed by the responders. On the other hand, non-responders contributed only 5% and 3.4% of the novel and expanded clones, respectively. Conclusion: We identified a CD8 continuum in BMs of patients with AML. The response to combined azacitidine/nivolumab is driven by emergence of novel clones and expansion of prior clones demonstrating T cell plasticity and adaptability. Our results demonstrate that the subverted T cells can be reinvigorated via PD-1 blockade and elicit responses in AML and warrants further functional characterization of GZMK expressing lymphocytes in mediating antileukemic responses.

This abstract is also being presented as PO059.

Citation Format: Hussein A. Abbas, Dapeng Hao, Katarzyna Tomczak, Praveen Barrodia, Jin Seon Im, Patrick K. Reville, Gheath Al-Atrash, Jing Ning, Maomao Ding, Jairo T. Mathews, Latasha Little, Jianhua Zhang, Sreyashi Basu, Marina Konopleva, Guillermo Garcia-Manero, Michael R. Green, Padmanee Sharma, James P. Allison, Steven M. Kornblau, Kunal Rai, Linghua Wang, Naval Daver, Andrew Futreal. Single-cell profiling of acute myeloid leukemia (AML) and its microenvironment reveals a CD8 continuum and adaptable T cell plasticity in response to PD-1 blockade-based therapy [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PR003.

Frontiers in cancer immunotherapy-a symposium report

Cancer immunotherapy has dramatically changed the approach to cancer treatment. The aim of targeting the immune system to recognize and destroy cancer cells has afforded many patients the prospect of achieving deep, long-term remission and potential cures. However, many challenges remain for achieving the goal of effective immunotherapy for all cancer patients. Checkpoint inhibitors have been able to achieve long-term responses in a minority of patients, yet improving response rates with combination therapies increases the possibility of toxicity. Chimeric antigen receptor T cells have demonstrated high response rates in hematological cancers, although most patients experience relapse. In addition, some cancers are notoriously immunologically "cold" and typically are not effective targets for immunotherapy. Overcoming these obstacles will require new strategies to improve upon the efficacy of current agents, identify biomarkers to select appropriate therapies, and discover new modalities to expand the accessibility of immunotherapy to additional tumor types and patient populations.

Abstract A23: Effects of anti-CTLA-4 and anti-PD-1 on memory T-cell differentiation and resistance to tumor relapse

Both anti-CTLA-4 and anti-PD-1 mediate significant response rates in cancer patients. As a hallmark of successful immunotherapies, they also mediate durable responses that last for years. For example, anti-CTLA-4 mediates a 22% 10-year overall survival rate, while anti-PD-1 mediates a 34% 5-year overall survival rate. Because of the broader uses of immunotherapies, the number of patients who have tumor relapse also increases. About 25% of patients who initially responded to anti-PD-1 have tumor relapse within 24 months. However, the relationship between tumor relapse and long-term effect of immunotherapies is still not clear. The goal of this study is to understand the differential effect of anti-CTLA-4 and anti-PD-1 on memory T-cell differentiation in murine tumor models. By rechallenging mice with tumor cells that have had tumors previously eradicated by either treatment, our results have shown that anti-CTLA-4 induces a more durable memory antitumor response compared to that treated with anti-PD-1. By tracing the antigen-specific CD8 T-cells throughout the memory phase, anti-CTLA-4 increases the frequency and cytokine production of antigen-specific T cells compared with anti-PD-1. We have also found that anti-CTLA-4 induces the population of KLRG1+ effector CD8 T cells among the effectors compared with anti-PD-1 during rechallenge, despite the ratio between central memory and effectors remaining the same. Our studies enable us to identify the long-term effect of immunotherapies on immune system.

Citation Format: Stephen Mok, Colm R. Duffy, Nana-Ama A. Anang, James P. Allison. Effects of anti-CTLA-4 and anti-PD-1 on memory T-cell differentiation and resistance to tumor relapse [abstract]. In: Proceedings of the AACR Special Conference on Melanoma: From Biology to Target; 2019 Jan 15-18; Houston, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(19 Suppl):Abstract nr A23.

Heterogeneous antibodies against SARS-CoV-2 spike receptor binding domain and nucleocapsid with implications for COVID-19 immunity

Evaluation of potential immunity against the novel severe acute respiratory syndrome (SARS) coronavirus that emerged in 2019 (SARS-CoV-2) is essential for health, as well as social and economic recovery. Generation of antibody response to SARS-CoV-2 (seroconversion) may inform on acquired immunity from prior exposure, and antibodies against the SARS-CoV-2 spike protein receptor binding domain (S-RBD) are speculated to neutralize virus infection. Some serology assays rely solely on SARS-CoV-2 nucleocapsid protein (N-protein) as the antibody detection antigen; however, whether such immune responses correlate with S-RBD response and COVID-19 immunity remains unknown. Here, we generated a quantitative serological ELISA using recombinant S-RBD and N-protein for the detection of circulating antibodies in 138 serial serum samples from 30 reverse transcription PCR–confirmed, SARS-CoV-2–hospitalized patients, as well as 464 healthy and non–COVID-19 serum samples that were collected between June 2017 and June 2020. Quantitative detection of IgG antibodies against the 2 different viral proteins showed a moderate correlation. Antibodies against N-protein were detected at a rate of 3.6% in healthy and non–COVID-19 sera collected during the pandemic in 2020, whereas 1.9% of these sera were positive for S-RBD. Approximately 86% of individuals positive for S-RBD–binding antibodies exhibited neutralizing capacity, but only 74% of N-protein–positive individuals exhibited neutralizing capacity. Collectively, our studies show that detection of N-protein–binding antibodies does not always correlate with presence of S-RBD–neutralizing antibodies and caution against the extensive use of N-protein–based serology testing for determination of potential COVID-19 immunity.

Detection of SARS-CoV-2 nucleocapsid protein binding antibodies does not always correlate with the presence of spike protein receptor binding domain neutralizing antibodies.

Abstract LB-399: Late interferon-gamma blockade improves antitumor efficacy of anti-CTLA-4 and anti-PD-1 combination treatment

The FDA has approved the use of immune checkpoint blockade antibodies targeting cytotoxic T-lymphocyte antigen-4 (CTLA-4) and programmed cell death-1 (PD-1) for cancer. Patients with metastatic melanoma that receive anti-CTLA-4 have a 22% 10-year overall survival rate, while those treated with anti-PD-1 have a 34% 5-year overall survival rate. The combination treatment of both mediates a 64% overall survival rate. Current literature suggests interferon signaling mediates the expression of inhibitory receptors such as programmed death-ligand 1 (PD-L1) in tumor microenvironment that may affect the responseivness to immunotherapy. However, the role of interferon signaling network throughout the timecourse of treatment remains unclear. In the B16F10 melanoma model, we first show that activated T-cells in combination treated mice produce more interferon-gamma (IFN-gamma) than naïve controls. Then, we have injected mice with anti-IFN-gamma antibody when 1) mice are first treated with combination CTLA-4/PD-1 blockade (early time point) and 2) the combination treatment is finished (late time point). We demonstrated that blocking IFN-gamma at the early time point compromises the antitumor efficacy of the combination treatment. In contrast, the antitumor efficacy of the combination treatment is improved and the expression of inducible co-stimulator (ICOS) on CD8 T-cells is increased if IFN-gamma is blocked at the late time point. Additionally, we found that the expression of PD-L1 in the tumor microenvironment is significantly reduced by IFN-gamma blockade at the late time point. Thus, we treated mice with anti-PD-L1 blocking antibody at the late time point and its antitumor tumor efficacy is similar to the mice treated with anti-IFN-gamma. It suggests that the improved antitumor efficacy of IFN-gamma blockade at the late time point in combination-treated mice is PD-L1 dependent. Collectively, we show that IFN-gamma has a complex and differential role throughout the time course of immunotherapy treatments, and this work suggests a potential combination treatment strategy with checkpoint blockade and late IFN-gamma blockade.

Citation Format: Stephen Mok, Renee Chin, James P. Allison. Late interferon-gamma blockade improves antitumor efficacy of anti-CTLA-4 and anti-PD-1 combination treatment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-399.

ARID1A mutation plus CXCL13 expression act as combinatorial biomarkers to predict responses to immune checkpoint therapy in mUCC

Immune checkpoint therapy (ICT) can produce durable antitumor responses in metastatic urothelial carcinoma (mUCC); however, the responses are not universal. Despite multiple approvals of ICT in mUCC, we lack predictive biomarkers to guide patient selection. The identification of biomarkers may require interrogation of both the tumor mutational status and the immune microenvironment. Through multi-platform immuno-genomic analyses of baseline tumor tissues, we identified the mutation of AT-rich interactive domain-containing protein 1A (ARID1A) in tumor cells and expression of immune cytokine CXCL13 in the baseline tumor tissues as two predictors of clinical responses in a discovery cohort (n = 31). Further, reverse translational studies revealed that CXCL13^-/- tumor-bearing mice were resistant to ICT, whereas ARID1A knockdown enhanced sensitivity to ICT in a murine model of bladder cancer. Next, we tested the clinical relevance of ARID1A mutation and baseline CXCL13 expression in two independent confirmatory cohorts (CheckMate275 and IMvigor210). We found that ARID1A mutation and expression of CXCL13 in the baseline tumor tissues correlated with improved overall survival (OS) in both confirmatory cohorts (CheckMate275, CXCL13 data, n = 217; ARID1A data, n = 139, and IMvigor210, CXCL13 data, n = 348; ARID1A data, n = 275). We then interrogated CXCL13 expression plus ARID1A mutation as a combination biomarker in predicting response to ICT in CheckMate275 and IMvigor210. Combination of the two biomarkers in baseline tumor tissues suggested improved OS compared to either single biomarker. Cumulatively, this study revealed that the combination of CXCL13 plus ARID1A may improve prediction capability for patients receiving ICT.

Spatially resolved analyses link genomic and immune diversity and reveal unfavorable neutrophil activation in melanoma

Complex tumor microenvironmental (TME) features influence the outcome of cancer immunotherapy (IO). Here we perform immunogenomic analyses on 67 intratumor sub-regions of a PD-1 inhibitor-resistant melanoma tumor and 2 additional metastases arising over 8 years, to characterize TME interactions. We identify spatially distinct evolution of copy number alterations influencing local immune composition. Sub-regions with chromosome 7 gain display a relative lack of leukocyte infiltrate but evidence of neutrophil activation, recapitulated in The Cancer Genome Atlas (TCGA) samples, and associated with lack of response to IO across three clinical cohorts. Whether neutrophil activation represents cause or consequence of local tumor necrosis requires further study. Analyses of T-cell clonotypes reveal the presence of recurrent priming events manifesting in a dominant T-cell clonotype over many years. Our findings highlight the links between marked levels of genomic and immune heterogeneity within the physical space of a tumor, with implications for biomarker evaluation and immunotherapy response.

Abstract IA20: Immune checkpoint blockade in cancer therapy: New insights and opportunities, and prospects for cures

The existence of multiple nonredundant inhibitory pathways that limit T-cell responses offers novel strategies for mobilizing the immune system to attack cancer cells. The best characterized of these immune checkpoints is CTLA-4, which inhibits T-cell proliferation by interfering with the interaction of the costimulatory molecule CD28 with its ligands B7-1 and B7-2 on the surface of antigen-presenting cells. Antibodies to CTLA-4 have proved effective against multiple tumor types in both preclinical and clinical studies. Ipilimumab, an antibody to human CTLA-4, showed long-term (>4 years) survival benefit in about 20% of patients in a randomized, placebo-controlled trial in late-stage melanoma. In 2011 it was approved by the FDA for treatment of late-stage melanoma, and it remains part of the standard of care for that disease. PD-1, another checkpoint, recruits a phosphatase and seems to interfere with T-cell antigen receptor-mediated signaling. It has two ligands, PD-L1 and PD-L2, which are both expressed on dendritic cells. However, many tumor cells also express PD-L1. Antibodies to PD-1 and PD-L1 have both shown objective responses against several tumor types in clinical trials with response rates of about 25%. Combination of anti-PD-1 and anti-CTLA-4 in melanoma provides objective responses in about 50% of late-stage melanoma patients. The FDA has now approved 6 different checkpoint antibodies for a variety of cancers including urothelial, renal, and lung cancers. A major focus of current efforts is the rational identification of combinatorial treatments that improve the response rate and expand the range of immune checkpoint inhibitors. We used high-parameter flow cytometry to identify the mostly nonoverlapping cellular mechanisms of CTLA-4 and PD-1 blockade, which may partially explain the enhanced effect of their combination. Further work has shown that combined CTLA-4 and PD-1 blockade, which provides higher response rates against a wider range of cancers than either monotherapy, acts through a population of T cells not enriched in either single treatment. T-cell responses are largely directed toward neoantigens arising as a result of mutational events associated with the carcinogenesis. While all tumors with antigens recognizable by the immune system should be targets for checkpoint blockade, tumors with lower burdens of mutations (e.g., prostate, breast, and kidney cancer) present special challenges for immune therapy. Recent evidence suggests that even the few neoantigens carried by these can provide targets for immune attack. Strategies for effective treatment of such tumors will be discussed.

Citation Format: James P. Allison. Immune checkpoint blockade in cancer therapy: New insights and opportunities, and prospects for cures [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr IA20.

Neoantigen responses, immune correlates, and favorable outcomes after ipilimumab treatment of patients with prostate cancer

Tumors with high mutational burden (TMB) tend to be responsive to immune checkpoint blockade (ICB) because there are neoantigens available for targeting by reinvigorated T cells, whereas those with low TMB demonstrate limited clinical responses. To determine whether antigen-specific T cell responses can be elicited after treatment with ICB in cancers that have a low TMB, we conducted a clinical trial with ipilimumab in 30 patients with metastatic castration-resistant prostate cancer. We identified two distinct cohorts by survival and progression times: "favorable" (n = 9) and "unfavorable" (n = 10). Patients in the favorable cohort had high intratumoral CD8 T cell density and IFN-γ response gene signature and/or antigen-specific T cell responses. Two patients with a relatively low TMB had T cell responses against unique neoantigens. Moreover, six of nine patients in the favorable group are still alive at the time of analysis, with survival ranging from 33 to 54 months after treatment. All 10 patients in the unfavorable cohort have succumbed to their disease and had survival ranging from 0.6 to 10.3 months. Collectively, our data indicate that immunological correlates associated with effector T cell responses are observed in patients with metastatic prostate cancer who benefit from ICB.

Immune profiling of human tumors identifies CD73 as a combinatorial target in glioblastoma

Immune checkpoint therapy with anti-CTLA-4 and anti-PD-1/PD-L1 has revolutionized the treatment of many solid tumors. However, the clinical efficacy of immune checkpoint therapy is limited to a subset of patients with specific tumor types^1,2. Multiple clinical trials with combinatorial immune checkpoint strategies are ongoing; however, the mechanistic rationale for tumor-specific targeting of immune checkpoints is elusive. To garner an insight into tumor-specific immunomodulatory targets, we analyzed 94 patients representing five different cancer types, including those that respond relatively well to immune checkpoint therapy and those that do not, such as glioblastoma multiforme, prostate cancer and colorectal cancer. Through mass cytometry and single-cell RNA sequencing, we identified a unique population of CD73^hi macrophages in glioblastoma multiforme that persists after anti-PD-1 treatment. To test if targeting CD73 would be important for a successful combination strategy in glioblastoma multiforme, we performed reverse translational studies using CD73^-/- mice. We found that the absence of CD73 improved survival in a murine model of glioblastoma multiforme treated with anti-CTLA-4 and anti-PD-1. Our data identified CD73 as a specific immunotherapeutic target to improve antitumor immune responses to immune checkpoint therapy in glioblastoma multiforme and demonstrate that comprehensive human and reverse translational studies can be used for rational design of combinatorial immune checkpoint strategies.

Phase II Trial of Ipilimumab with Stereotactic Radiation Therapy for Metastatic Disease: Outcomes, Toxicities, and Low-Dose Radiation-Related Abscopal Responses

Ipilimumab is effective for patients with melanoma, but not for those with less immunogenic tumors. We report a phase II trial of ipilimumab with concurrent or sequential stereotactic ablative radiotherapy to metastatic lesions in the liver or lung (NCT02239900). Ipilimumab (every 3 weeks for 4 doses) was given with radiotherapy begun during the first dose (concurrent) or 1 week after the second dose (sequential) and delivered as 50 Gy in 4 fractions or 60 Gy in 10 fractions to metastatic liver or lung lesions. In total, 106 patients received ≥1 cycle of ipilimumab with radiation. Median follow-up was 10.5 months. Median progression-free survival time was 2.9 months (95% confidence interval, 2.45-3.40), and median overall survival time was not reached. Rates of clinical benefit of nonirradiated tumor volume were 26% overall, 28% for sequential versus 20% for concurrent therapy (P = 0.250), and 31% for lung versus 14% for liver metastases (P = 0.061). The sequential lung group had the highest rate of clinical benefit at 42%. There were no differences in treatment-related adverse events between groups. Exploratory analysis of nontargeted lesions revealed that lesions receiving low-dose radiation were more likely to respond than those that received no radiation (31% vs. 5%, P = 0.0091). This phase II trial of ipilimumab with stereotactic radiotherapy describes satisfactory outcomes and low toxicities, lending support to further investigation of combined-modality therapy for metastatic cancers.

Donor and host B7-H4 expression negatively regulates acute graft-versus-host disease lethality

B7-H4 is a negative regulatory B7 family member. We investigated the role of host and donor B7-H4 in regulating acute graft-versus-host disease (GVHD). Allogeneic donor T cells infused into B7-H4-/- versus WT recipients markedly accelerated GVHD-induced lethality. Chimera studies pointed toward B7-H4 expression on host hematopoietic cells as more critical than parenchymal cells in controlling GVHD. Rapid mortality in B7-H4-/- recipients was associated with increased donor T cell expansion, gut T cell homing and loss of intestinal epithelial integrity, increased T effector function (proliferation, proinflammatory cytokines, cytolytic molecules), and reduced apoptosis. Higher metabolic demands of rapidly proliferating donor T cells in B7-H4-/- versus WT recipients required multiple metabolic pathways, increased extracellular acidification rates (ECARs) and oxygen consumption rates (OCRs), and increased expression of fuel substrate transporters. During GVHD, B7-H4 expression was upregulated on allogeneic WT donor T cells. B7-H4-/- donor T cells given to WT recipients increased GVHD mortality and had function and biological properties similar to WT T cells from allogeneic B7-H4-/- recipients. Graft-versus-leukemia responses were intact regardless as to whether B7-H4-/- mice were used as hosts or donors. Taken together, these data provide new insights into the negative regulatory processes that control GVHD and provide support for developing therapeutic strategies directed toward the B7-H4 pathway.

Blockade of CTLA-4 and PD-1 Enhances Adoptive T-cell Therapy Efficacy in an ICOS-Mediated Manner

Adoptive transfer of tumor-reactive T cells (ACT) has led to modest clinical benefit in the treatment of solid tumors. Failures with this therapy are primarily due to inadequate infiltration and poor function of adoptively transferred cells in the tumor microenvironment. To improve the efficacy of ACT, we combined ACT with dual blockade of CTLA-4 and PD-1. Treatment with anti-CTLA-4 plus anti-PD-1 compared with monotherapy resulted in durable antitumor responses, enhanced effector function of ACT, utilizing PMEL-1 transgenic (Tg⁺) CD8⁺ T cells, and improved survival. Using PMEL-1ICOS^-/- mice, we showed that deletion of the inducible T-cell costimulator (ICOS) receptor abolished the therapeutic benefits, with selective downregulation of Eomesodermin (Eomes), interferon gamma (IFNγ), and perforin. Higher expression of IFNγ and Eomes was noted in human ICOS^hi CD8⁺ T cells compared with ICOS^low counterparts. Together, our data provide direct evidence that ACT combined with immune-checkpoint therapy confers durable antitumor responses, which largely depended on CD8⁺ T-cell-intrinsic expression of ICOS. Our study provides a foundation of testing combinatorial therapy of ACT of CD8 T cells and dual blocking of CTLA-4 and PD-1 in patients with melanoma.

Characterization and Comparison of GITR Expression in Solid Tumors

PURPOSE

Determine the differential effect of a FcγR-binding, mIgG2a anti-GITR antibody in mouse tumor models, and characterize the tumor microenvironment for the frequency of GITR expression in T-cell subsets from seven different human solid tumors.Experimental Design: For mouse experiments, wild-type C57BL/6 mice were subcutaneously injected with MC38 cells or B16 cells, and BALB/c mice were injected with CT26 cells. Mice were treated with the anti-mouse GITR agonist antibody 21B6, and tumor burden and survival were monitored. GITR expression was evaluated at the single-cell level using flow cytometry (FC). A total of 213 samples were evaluated for GITR expression by IHC, 63 by FC, and 170 by both in seven human solid tumors: advanced hepatocellular carcinoma, non-small cell lung cancer (NSCLC), renal cell carcinoma, pancreatic carcinoma, head and neck carcinoma, melanoma, and ovarian carcinoma.

RESULTS

The therapeutic benefit of 21B6 was greatest in CT26 followed by MC38, and was least in the B16 tumor model. The frequency of CD8 T cells and effector CD4 T cells within the immune infiltrate correlated with response to treatment with GITR antibody. Analysis of clinical tumor samples showed that NSCLC, renal cell carcinoma, and melanoma had the highest proportions of GITR-expressing cells and highest per-cell density of GITR expression on CD4⁺ Foxp3⁺ T regulatory cells. IHC and FC data showed similar trends with a good correlation between both techniques.

CONCLUSIONS

Human tumor data suggest that NSCLC, renal cell carcinoma, and melanoma should be the tumor subtypes prioritized for anti-GITR therapy development.

Immunologic Correlates of Pathologic Complete Response to Preoperative Immunotherapy in Hepatocellular Carcinoma

In hepatocellular carcinoma (HCC), surgical resection is associated with high recurrence rate, and no effective adjuvant therapy currently exists. We initiated a pilot randomized trial of perioperative immunotherapy with nivolumab and ipilimumab for resectable HCC. Here, we provide an illustrative report of a case that achieved a complete response and report immunologic correlates of this complete pathologic response to perioperative immunotherapy. Clinical response was correlated with an increase in CD8⁺ T-cell infiltration, with an increase in two effector T-cell clusters. This study is ongoing, and the final results may contribute to a paradigm shift in the perioperative treatment of HCC, leading to the incorporation of immunotherapy in the curative setting.

Abstract 499: NanoString®GeoMx®digital spatial profiling further defines the role of B cells in the response to immune checkpoint blockade

Background: While treatment with immune checkpoint blockade (ICB) has markedly improved outcomes in advanced melanoma patients and other malignancies, predicting response remains a challenge. Biomarkers including tumor mutational burden (TMB), T-cell infiltration, and PD-L1 expression, have been identifiedbut remain inadequate. Other components of innate and adaptive immunity, including B-cells and tertiary lymphoid structures (TLS), have been implicated in the response to other cancer therapies, andpreclinical data suggests B cells may contribute in the response to immunotherapy. Here, we use targeted protein expression profiling-via NanoString digital spatial profiling (DSP) technology (research use only)-to demonstrate a role for B cells in the response to ICB in patients with high-risk resectable melanoma; furthermore, we characterize the B cell subsets that enable this function.

Methods: We conducted a phase 2 clinical trial of neoadjuvant ICB therapy in patients with high-risk resectable melanoma (PD-1 blockade monotherapy or combined CTLA-4/PD-1 blockade) (NCT02519322). Longitudinal tumor samples were taken during therapy. Formalin-fixed paraffin embedded tissue sections from tumor samples (n=10 responders [R], n=10 non-responders [NR]) were analyzed by NanoString DSP technology and stained with a cocktail of S100B, CD45, CD19 and a 40-protein cocktail of antibodies conjugated to UV-photocleavable DNA barcodes. Regions of interest (ROI) were delineated using immunofluorescence followed by UV excitation of the defined ROIs, releasing the DNA barcodes for downstream quantitation on the NanoString nCounter®platform. Utilizing masking strategies, we define the unique expression pattern within discrete subsets of immune cells. These same tumors have concurrently been analyzed by RNAseq, immunohistochemistry, CYTOF, and single-cell RNAseq.

Results: Biomarker counts are highly concordant across samples from the same patient’s tumor. High concordance between DSP and quantitative fluorescence is seen as a validation for the DSP method. We identify B cells as components of TLS; the B cells are closely integrated with CD4 and CD8 T cells and follicular dendritic cells. There are significantly more TLS identified in R compared to NR patients. Utilizing CYTOF, we concurrently identify specific subsets of B cells present within the TLS associated with response. We characterize the spatial relationship of these same B cell subsets with other components of the TLS and define the protein expression patterns of these cells.

Conclusion: NanoString DSP data complement our deep molecular and immune profiling of tumors from melanoma patients treated with ICB; together, they provide a novel predictive role for B-cells and TLS in the response to ICB and, importantly, provide mechanistic insight into their potential contribution in the response to cancer therapy.

Citation Format: Beth A. Helmink, Sangeetha Reddy, Jorge Blando, Yan Liang, Sarah Warren, Vancheswaran Gopalakrishnan, Hussein A. Tawbi, Rodabe N. Amaria, Michael Davies, Jeffrey E. Gershenwald, Elizabeth Burton, Rafet Basar, Alexander J. Lazar, Courtney W. Hudgens, Katy Rezvani, James P. Allison, Padmanee Sharma, Joseph M. Beechem, Jennifer A. Wargo, Michael T. Tetzlaff. NanoString®GeoMx®digital spatial profiling further defines the role of B cells in the response to immune checkpoint blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 499.