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Diverse factors contribute to the limited clinical response to radiotherapy (RT) and immunotherapy in metastatic non–small cell lung cancer (NSCLC), among which is the ability of these tumors to recruit a retinue of suppressive immune cells—such as M2 tumor-associated macrophages (TAM)—thereby establishing an immunosuppressive tumor microenvironment that contributes to tumor progression and radio resistance. M2 TAMs are activated by the STAT6 signaling pathway. Therefore, we targeted STAT6 using an antisense oligonucleotide (ASO) along with hypofractionated RT (hRT; 3 fractions of 12 Gy each) to primary tumors in three bilateral murine NSCLC models (Lewis lung carcinoma, 344SQ-parental, and anti–PD-1–resistant 344SQ lung adenocarcinomas). We found that STAT6 ASO plus hRT slowed growth of both primary and abscopal tumors, decreased lung metastases, and extended survival. Interrogating the mechanism of action showed reduced M2 macrophage tumor infiltration, enhanced TH1 polarization, improved T-cell and macrophage function, and decreased TGFβ levels. The addition of anti–PD-1 further enhanced systemic antitumor responses. These results provide a preclinical rationale for the pursuit of an alternative therapeutic approach for patients with immune-resistant NSCLC.

Supplementary Figure S1. CONSORT flow diagram for patient selection

Patient characteristics

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.

Supplementary Figures

Supplementary Figures and Tables

Immune checkpoint inhibitors, such as anti–PD-1/PD-L1, have emerged as promising therapies for advanced non–small cell lung cancer (NSCLC). However, approximately 80% of patients do not respond to immunotherapy given alone because of intrinsic or acquired resistance. Radiotherapy (XRT) can overcome PD-1 resistance and improve treatment outcomes, but its efficacy remains suboptimal. The tyrosine phosphatase SHP-2, expressed in some cancers and in immune cells, has been shown to negatively affect antitumor immunity. Our hypothesis was that SHP-2 inhibition in combination with anti–PD-L1 would enhance immune-mediated responses to XRT and synergistically boost antitumor effects in an anti–PD-1–resistant mouse model. We treated 129Sv/Ev mice with anti–PD-1–resistant 344SQ NSCLC adenocarcinoma with oral SHP099 (a SHP-2 inhibitor) combined with XRT and intraperitoneal anti–PD-L1. Primary tumors were treated with XRT (three fractions of 12 Gy each), whereas abscopal (out-of-field) tumors were observed but not treated. XRT in combination with SHP099 and anti–PD-L1 promoted local and abscopal responses, reduced lung metastases, and improved mouse survival. XRT also increased SHP-2+ M1 tumor-associated macrophages in abscopal tumors (P = 0.019). The addition of SHP099 also associated with a higher M1/M2 ratio, greater numbers of CD8+ T cells, and fewer regulatory T cells. This triple-combination therapy had strong antitumor effects in a mouse model of anti–PD-1–resistant NSCLC and may be a novel therapeutic approach for anti–PD-1–resistant NSCLC in patients.

Diverse factors contribute to the limited clinical response to radiotherapy (RT) and immunotherapy in metastatic non–small cell lung cancer (NSCLC), among which is the ability of these tumors to recruit a retinue of suppressive immune cells—such as M2 tumor-associated macrophages (TAM)—thereby establishing an immunosuppressive tumor microenvironment that contributes to tumor progression and radio resistance. M2 TAMs are activated by the STAT6 signaling pathway. Therefore, we targeted STAT6 using an antisense oligonucleotide (ASO) along with hypofractionated RT (hRT; 3 fractions of 12 Gy each) to primary tumors in three bilateral murine NSCLC models (Lewis lung carcinoma, 344SQ-parental, and anti–PD-1–resistant 344SQ lung adenocarcinomas). We found that STAT6 ASO plus hRT slowed growth of both primary and abscopal tumors, decreased lung metastases, and extended survival. Interrogating the mechanism of action showed reduced M2 macrophage tumor infiltration, enhanced TH1 polarization, improved T-cell and macrophage function, and decreased TGFβ levels. The addition of anti–PD-1 further enhanced systemic antitumor responses. These results provide a preclinical rationale for the pursuit of an alternative therapeutic approach for patients with immune-resistant NSCLC.

We have previously demonstrated that PD-1 blockade decreased the incidence of high-grade dysplasia in a carcinogen-induced murine model of oral squamous cell carcinoma (OSCC). It remains unknown, however, whether there are additional factors involved in escape from immune surveillance that could serve as additional targets for immunoprevention. We performed this study to further characterize the immune landscape of oral premalignant lesions (OPL) and determine the impact of targeting of the PD-1, CTLA-4, CD40, or OX40 pathways on the development of OPLs and oral carcinomas in the 4-nitroquinoline 1-oxide model. The immune pathways were targeted using mAbs or, in the case of the PD-1/PD-L1 pathway, using PD-L1–knockout (PD-L1ko) mice. After intervention, tongues and cervical lymph nodes were harvested and analyzed for malignant progression and modulation of the immune milieu, respectively. Targeting of CD40 with an agonist mAb was the most effective treatment to reduce transition of OPLs to OSCC; PD-1 alone or in combination with CTLA-4 inhibition, or PD-L1ko, also reduced progression of OPLs to OSCC, albeit to a lesser extent. Distinct patterns of immune system modulation were observed for the CD40 agonists compared with blockade of the PD-1/PD-L1 axis with or without CTLA-4 blockade; CD40 agonist generated a lasting expansion of experienced/memory cytotoxic T lymphocytes and M1 macrophages, whereas PD-1/CTLA-4 blockade resulted in a pronounced depletion of regulatory T cells among other changes. These data suggest that distinct approaches may be used for targeting different steps in the development of OSCC, and that CD40 agonists merit investigation as potential immunoprevention agents in this setting.Prevention Relevance:PD-1/PD-L1 pathway blockade, as well as activation of the CD40 pathway, were able to prevent OPL progression into invasive OSCC in a murine model. A distinct pattern of immune modulation was observed when either the CD40 or the PD-1/PD-L1 pathways were targeted.

Percentage of CD4+CD44hi

Table 1: Pathology classification criteria. Table 2: Flow cytometry antibodies

Purpose: Radiation is used extensively to treat localized cancer, but improved understanding of its effects on the immune system has increased interest in its potential systemic (abscopal) effects, particularly in combination with checkpoint inhibitors such as anti-PD1. The majority of patients either do not respond or develop resistance to monotherapy over time. Here, we investigated the efficacy of OX40 (CD134) stimulation as an alternative immunotherapeutic approach in combination with radiotherapy (XRT) in a murine model of anti–PD1-resistant lung tumors.Experimental Design: We established a bilateral tumor model in 129Sv/Ev mice using an anti–PD1-resistant lung tumor cell line. Primary tumors were treated with intratumoral injection of an OX40 agonist antibody, given as adjuvant therapy after XRT (36 Gy in three 12-Gy fractions), whereas secondary tumors were left untreated to investigate abscopal outcomes.Results: The combination of XRT followed by OX40 stimulation effectively inhibited local and systemic antitumor growth, limited lung metastases, and improved survival rates. This treatment regimen augmented CD4+ and CD8+ T-cell expansion. XRT induced the expression of OX40 on T cells in tumors and spleens and increased the percentages of splenic CD103+ dendritic cells.Conclusions: Our data extend the benefits of radiation to systemic disease control, especially when combined with anti-OX40 agonist to promote immunologically mediated abscopal effects. Moreover, this study provides a rational treatment approach and sequence to overcome anti–PD1-resistant poorly immunogenic tumors. Clin Cancer Res; 24(22); 5735–43. ©2018 AACR.

CD8+ CD103+ TRM cells express high levels of PD1. Flow cytometric analysis for TILs on day 29 from the triple therapy group (RT + α-PD1 + α-MerTK). Cells were gated on CD45 population then on CD4 and CD8, followed by CD8 and CD103 to check for PD1 expression in the final gate.

Purpose:Radiotherapy (RT) traditionally has been used for local tumor control in the treatment of cancer. The recent discovery that radiotherapy can have anticancer effects on the immune system has led to recognition of its ability to sensitize the tumor microenvironment to immunotherapy. However, radiation can also prompt adverse immunosuppressive effects that block aspects of systemic response at other tumor sites. Our hypothesis was that inhibition of the MER proto-oncogene tyrosine kinase (MerTK) in combination with anti-programmed cell death-1 (α-PD1) checkpoint blockade will enhance immune-mediated responses to radiotherapy.Experimental Design:We tested the efficacy of this triple therapy (Radiation + α-PD1 + α-MerTK mAbs) in 129Sv/Ev mice with bilateral lung adenocarcinoma xenografts. Primary tumors were treated with stereotactic radiotherapy (36 Gy in 3 12-Gy fractions), and tumors were monitored for response.Results:The triple therapy significantly delayed abscopal tumor growth, improved survival rates, and reduced numbers of lung metastases. We further found that the triple therapy increased the activated CD8+ and NK cells populations measured by granzyme B expression with upregulation of CD8+CD103+ tissue-resident memory cells (TRM) within the abscopal tumor microenvironment relative to radiation only.Conclusions:The addition of α-PD1 + α-MerTK mAbs to radiotherapy could alter the cell death to be more immunogenic and generate adaptive immune response via increasing the retention of TRM cells in the tumor islets of the abscopal tumors which was proven to play a major role in survival of non-small cell lung cancer patients.

Radiotherapy (XRT), a well-known activator of the inflammasome and immune priming, is in part capable of reversing resistance to anti-PD1 treatment. Although NLRP3 is typically observed for its role in exacerbating XRT-induced tissue damage, the NLRP3 inflammasome can also be protective and augment the effect of XRT when used in proper dosing and sequencing. However, whether NLRP3 agonist boosts radiation-induced immune priming and promote abscopal responses in anti-PD1 resistant model is still unknown. Therefore, in this study, we paired intratumoral injection of an NLRP3 agonist with XRT to stimulate the immune system in both wild type (344SQ-P) and anti-PD1 resistant (344SQ-R) murine-implanted lung adenocarcinoma models. We found that the combination of XRT + NLPR3 agonist enhanced control of implanted lung adenocarcinoma primary as well as secondary tumors in a radiological dose-dependent manner, in which 12Gy x 3 fractions of stereotactic XRT was better than 5Gy x 3, while 1Gy x 2 did not improve the NLRP3 effect. Survival and tumor growth data also showed significant abscopal response with the triple therapy (12Gyx3 + NLRP3 agonist + α-PD1) in both 344SQ-P and 344SQ-R aggressively growing models. Multiple pro-inflammatory cytokines (IL-1b, IL-4, IL-12, IL-17, IFN-γ and GM-CSF) were elevated in the serum of mice treated with XRT + NLRP3 or triple therapy. The Nanostring results showed that NLRP3 agonist is capable of increasing antigen presentation, innate function, and T-cell priming. This study can be of particular importance to treat patients with immunologically-cold solid tumors whom are also refractory to prior checkpoint treatments.

To report early findings from a phase II trial of high-dose radiotherapy (HD-RT) with or without low-dose RT (LD-RT) for metastatic cancer.Eligible patients had metastatic disease that progressed on immunotherapy within 6 months. Patients were given either HD-RT (20-70 Gy total; 3-12.5 Gy/f), or HD-RT + LD-RT (0.5-2 Gy/f up to 1-10 Gy total) to separate lesions, with continued immunotherapy. Radiographic response was assessed per RECIST 1.1 and Immune-Related Response Criteria (irRC). Primary endpoints: (1) 4-month disease control (DCR, complete/partial response [CR/PR] or stable disease [SD]) or an overall response (ORR, CR/PR) at any point in ≥10% of patients, per RECIST 1.1; (2) dose-limiting toxicity within 3 months not exceeding 30%. Secondary endpoint was lesion-specific response.Seventy-four patients (NSCLC, n = 38; melanoma n = 21) were analyzed (39 HD-RT and 35 HD-RT + LD-RT). The median follow-up time was 13.6 months. The primary endpoint was met for 72 evaluable patients, with a 4-month DCR of 42% (47% [16/34] vs. 37% [14/38] in HD-RT + LD-RT vs. HD-RT, P = 0.38), and 19% ORR at any time (26% [9/34] vs. 13% [5/38] in HD-RT + LD-RT vs. HD-RT, P = 0.27). Three patients had toxicity ≥grade 3. LD-RT lesion response (53%) was improved compared to nonirradiated lesions in HD-RT + LD-RT (23%, P = 0.002) and HD-RT (11%, P 0.001). T- and NK cell infiltration was enhanced in lesions treated with LD-RT.HD-RT plus LD-RT safely improved lesion-specific response in patients with immune resistant solid tumors by promoting infiltration of effector immune cells into the tumor microenvironment.

We have previously demonstrated that PD-1 blockade decreased the incidence of high-grade dysplasia in a carcinogen-induced murine model of oral squamous cell carcinoma (OSCC). It remains unknown, however, whether there are additional factors involved in escape from immune surveillance that could serve as additional targets for immunoprevention. We performed this study to further characterize the immune landscape of oral premalignant lesions (OPL) and determine the impact of targeting of the PD-1, CTLA-4, CD40, or OX40 pathways on the development of OPLs and oral carcinomas in the 4-nitroquinoline 1-oxide model. The immune pathways were targeted using mAbs or, in the case of the PD-1/PD-L1 pathway, using PD-L1–knockout (PD-L1ko) mice. After intervention, tongues and cervical lymph nodes were harvested and analyzed for malignant progression and modulation of the immune milieu, respectively. Targeting of CD40 with an agonist mAb was the most effective treatment to reduce transition of OPLs to OSCC; PD-1 alone or in combination with CTLA-4 inhibition, or PD-L1ko, also reduced progression of OPLs to OSCC, albeit to a lesser extent. Distinct patterns of immune system modulation were observed for the CD40 agonists compared with blockade of the PD-1/PD-L1 axis with or without CTLA-4 blockade; CD40 agonist generated a lasting expansion of experienced/memory cytotoxic T lymphocytes and M1 macrophages, whereas PD-1/CTLA-4 blockade resulted in a pronounced depletion of regulatory T cells among other changes. These data suggest that distinct approaches may be used for targeting different steps in the development of OSCC, and that CD40 agonists merit investigation as potential immunoprevention agents in this setting.Prevention Relevance:PD-1/PD-L1 pathway blockade, as well as activation of the CD40 pathway, were able to prevent OPL progression into invasive OSCC in a murine model. A distinct pattern of immune modulation was observed when either the CD40 or the PD-1/PD-L1 pathways were targeted.

Introduction: Immunoradiotherapy combining radiotherapy and immune checkpoint blockade, has achieved impressive treatment outcomes. We have previously demonstrated that photon (XRT) and proton (PRT) localized radiotherapy in combination with immune checkpoint blockade and NBTXR3, a radioenhancing nanoparticle, could induce a systemic antitumor immune response. However, no studies have compared the treatment efficacy of PRT and XRT immunoradiotherapy. Here, we compared the capabilities of PRT and XRT when combined with NBTXR3 and PD1 blockade for inducing an antitumor immune response. Methods: 344SQR cells were inoculated in the right and left hindlimbs of 129Sv/Ev mice on day 0 and day 4 to establish primary and secondary tumors, respectively. Mice were divided into five treatment groups: 1) untreated control; 2) XRT+αPD1; 3) NBTXR3+XRT+αPD1; 4) PRT+αPD1; 5) NBTXR3+PRT+αPD1. The primary tumors were intratumorally injected with NBTXR3 nanoparticles on day 7, followed by two fractions of 12 Gy XRT or PRT on days 8 and 9 (total dose of 24 Gy). Two hundred μg of αPD1 was given to the mice on days 7, 10, 14, 21, 28, 35, and 42 through intraperitoneal injection. We assayed whole tumor RNAs with a Nanostring pan-cancer immune panel to profile the tumor immune microenvironment changes. In addition, immune cells extracted from the tumors were analyzed with single-cell RNA sequencing (scRNAseq). The survivor mice treated with the NBTXR3+PRT+αPD1 were rechallenged with 344SQR and 344SQP cells. Results: PRT+ αPD1 resulted in significantly better control of the primary tumors than XRT+ αPD1. No significant difference was observed in the volume of the secondary tumors treated with XRT+ αPD1 and the control. In contrast, PRT+ αPD1 resulted in a pronounced abscopal effect. Adding NBTXR3 to XRT+ αPD1 and PRT+ αPD1 improved the control of both the primary and secondary tumors. In addition, NBTXR3+PRT+αPD1 achieved significantly slower growth of the two tumors and more prolonged survival than NBTXR3+XRT+αPD1. Remarkably, NBTXR3+PRT+αPD1 eradicated both primary and secondary tumors in 40% of the treated mice, while no mice were cured by NBTXR3+XRT+αPD1. Nanostring analysis and scRNAseq revealed better activation and infiltration of antitumoral immune cells to the two tumors when treated with PRT than XRT. The survivor mice treated with NBTXR3+PRT+αPD1 effectively rejected tumor growth after rechallenge with 344SQR and 344SQP cells. Conclusions: When combined with NBTXR3, PRT with αPD1 exhibited significantly better treatment efficacy than XRT with αPD1. The superior efficacy of NBTXR3+PRT+αPD1 is accompanied by a more robust immune activation and immune cell infiltration in irradiated and unirradiated tumors. Citation Format: Yun Hu, Sébastien Paris, Narayan Sahoo, Qi Wang, Qianxia Wang, Hampartsoum B. Barsoumian, Jordan Da Silva, Célia Bienassis, Ailing Huang, Nahum Puebla-Osorio, Saumil Gandhi, Quynh-Nhu Nguyen, Jing Wang, Maria A. Cortez, James W. Welsh. NBTXR3 radio-enhancing nanoparticle achieves a more robust antitumor immune response when combined with proton radiotherapy than photon radiotherapy [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 2415.

Metastatic cancer is a heterogeneous entity, some of which could benefit from local consolidative radiation therapy (RT). Although randomized evidence is growing in support of using RT for oligometastatic disease, a highly active area of investigation relates to whether RT could benefit patients with polymetastatic disease. This article highlights the preclinical and clinical rationale for using RT for polymetastatic disease, proposes an exploratory framework for selecting patients best suited for these types of treatments, and briefly reviews potential challenges. The goal of this hypothesis-generating review is to address personalized multimodality systemic treatment for patients with metastatic cancer. The rationale for using high-dose RT is primarily for local control and immune activation in either oligometastatic or polymetastatic disease. However, the primary application of low-dose RT is to activate distinct antitumor immune pathways and modulate the tumor stroma in efforts to better facilitate T cell infiltration. We explore clinical cases involving high- and low-dose RT to demonstrate the potential efficacy of such treatment. We then group patients by extent of disease burden to implement high- and/or low-dose RT. Patients with low-volume disease may receive high-dose RT to all sites as part of an oligometastatic paradigm. Subjects with high-volume disease (for whom standard of care remains palliative RT only) could be treated with a combination of high-dose RT to a few sites for immune activation, while receiving low-dose RT to several remaining lesions to enhance systemic responses from high-dose RT and immunotherapy. We further discuss how emerging but speculative concepts such as immune function may be integrated into this approach and examine therapies currently under investigation that may help address immune deficiencies. The review concludes by addressing challenges in using RT for polymetastatic disease, such as concerns about treatment planning workflows, treatment times, dose constraints for multiple-isocenter treatments, and economic considerations.

Immune function (e.g. absolute lymphocyte count (ALC)) and modifiable predictors thereof (e.g. volume of the heart/lungs receiving low-dose radiation) impact outcomes of cancer patients, but this has not been well-studied in the immunotherapy era. This investigation of metastatic lung cancer assessed the interaction of dosimetric parameters (e.g. lung/heart V5), radiotherapy technique (e.g. stereotactic (SBRT) or traditional radiotherapy), lymphopenia, and survival outcomes.Patients were collected from three institutional phase I/II trials of combined immunotherapy and lung irradiation. SBRT referred to 50 Gy/4 fractions or 60 Gy/10 fractions, and traditional RT as 45 Gy/15 fractions. Blood collections were standardized on the first and last day of radiotherapy and each cycle of immunotherapy. Statistics included multivariable linear regression to identify variables associated with ALC decline, Kaplan-Meier analysis of overall and progression-free survival (PFS), and Cox multivariate analysis.The median follow-up of the 165 patients was 21 months. The only factor independently predictive of ALC decline was traditional RT (p 0.001). Therefore, the analysis was repeated for traditional RT and SBRT separately; lung V5 was associated with lymphopenia for traditional RT (p 0.001) but not SBRT (p = 0.12). Pre-radiotherapy ALC was independently associated with PFS in both cohorts (p 0.05 for both); post-RT ALC predicted for PFS in the traditional RT (p = 0.048) but not the SBRT (p = 0.90) group. Neither heart nor lung V5 was independently associated with PFS.When combined with immunotherapy, SBRT may better preserve lymphocytes (and hence improve outcomes) than traditional RT. When administering traditional RT, constraining the lung V5 may indirectly impact outcomes by means of ALC preservation.

Immune checkpoint inhibitors, such as anti–PD-1/PD-L1, have emerged as promising therapies for advanced non–small cell lung cancer (NSCLC). However, approximately 80% of patients do not respond to immunotherapy given alone because of intrinsic or acquired resistance. Radiotherapy (XRT) can overcome PD-1 resistance and improve treatment outcomes, but its efficacy remains suboptimal. The tyrosine phosphatase SHP-2, expressed in some cancers and in immune cells, has been shown to negatively affect antitumor immunity. Our hypothesis was that SHP-2 inhibition in combination with anti–PD-L1 would enhance immune-mediated responses to XRT and synergistically boost antitumor effects in an anti–PD-1–resistant mouse model. We treated 129Sv/Ev mice with anti–PD-1–resistant 344SQ NSCLC adenocarcinoma with oral SHP099 (a SHP-2 inhibitor) combined with XRT and intraperitoneal anti–PD-L1. Primary tumors were treated with XRT (three fractions of 12 Gy each), whereas abscopal (out-of-field) tumors were observed but not treated. XRT in combination with SHP099 and anti–PD-L1 promoted local and abscopal responses, reduced lung metastases, and improved mouse survival. XRT also increased SHP-2+ M1 tumor-associated macrophages in abscopal tumors (P = 0.019). The addition of SHP099 also associated with a higher M1/M2 ratio, greater numbers of CD8+ T cells, and fewer regulatory T cells. This triple-combination therapy had strong antitumor effects in a mouse model of anti–PD-1–resistant NSCLC and may be a novel therapeutic approach for anti–PD-1–resistant NSCLC in patients.

This study combines a novel strategy of radiotherapy that utilizes high- and low- dose radiation with immune oncology agents (anti-TIGIT and anti-PD1 monoclonal antibodies) in order to overcome the inhibitory tumor stroma and battle tumors systemically. The findings from this work will impact how checkpoint inhibitors are delivered to maximize their efficacy. Tumors deploy various immune-evasion mechanisms that create a suppressive environment and render effector T-cells exhausted and inactive. Therefore, a rational utilization of checkpoint inhibitors may alleviate exhaustion and may partially restore antitumor functions. However, in high-tumor-burden models, the checkpoint blockade fails to maintain optimal efficacy, and other interventions are necessary to overcome the inhibitory tumor stroma. One such strategy is the use of radiotherapy to reset the tumor microenvironment and maximize systemic antitumor outcomes. In this study, we propose the use of anti-PD1 and anti-TIGIT checkpoint inhibitors in conjunction with our novel RadScopal technique to battle highly metastatic lung adenocarcinoma tumors, bilaterally established in 129Sv/Ev mice, to mimic high-tumor-burden settings. The RadScopal approach is comprised of high-dose radiation directed at primary tumors with low-dose radiation delivered to secondary tumors to improve the outcomes of systemic immunotherapy. Indeed, the triple therapy with RadScopal + anti-TIGIT + anti-PD1 was able to prolong the survival of treated mice and halted the growth of both primary and secondary tumors. Lung metastasis counts were also significantly reduced. In addition, the low-dose radiation component reduced TIGIT receptor (PVR) expression by tumor-associated macrophages and dendritic cells in secondary tumors. Finally, low-dose radiation within triple therapy decreased the percentages of TIGIT(+) exhausted T-cells and TIGIT(+) regulatory T-cells. Together, our translational approach provides a new treatment alternative for cases refractory to other checkpoints and may bring immunotherapy into a new realm of systemic disease control., United States Department of Health and Human Services; National Institutes of Health (NIH); NIH National Cancer Institute (NCI)

Purpose: Radiotherapy (RT) traditionally has been used for local tumor control in the treatment of cancer. The recent discovery that radiotherapy can have anticancer effects on the immune system has led to recognition of its ability to sensitize the tumor microenvironment to immunotherapy. However, radiation can also prompt adverse immunosuppressive effects that block aspects of systemic response at other tumor sites. Our hypothesis was that inhibition of the MER proto-oncogene tyrosine kinase (MerTK) in combination with anti-programmed cell death-1 (α-PD1) checkpoint blockade will enhance immune-mediated responses to radiotherapy. Experimental Design: We tested the efficacy of this triple therapy (Radiation + α-PD1 + α-MerTK mAbs) in 129Sv/Ev mice with bilateral lung adenocarcinoma xenografts. Primary tumors were treated with stereotactic radiotherapy (36 Gy in 3 12-Gy fractions), and tumors were monitored for response. Results: The triple therapy significantly delayed abscopal tumor growth, improved survival rates, and reduced numbers of lung metastases. We further found that the triple therapy increased the activated CD8+ and NK cells populations measured by granzyme B expression with upregulation of CD8+CD103+ tissue-resident memory cells (TRM) within the abscopal tumor microenvironment relative to radiation only. Conclusions: The addition of α-PD1 + α-MerTK mAbs to radiotherapy could alter the cell death to be more immunogenic and generate adaptive immune response via increasing the retention of TRM cells in the tumor islets of the abscopal tumors which was proven to play a major role in survival of non-small cell lung cancer patients.

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.