PD-1 Monoclonal Antibody Research Articles

Irradiation combined with PD-1 inhibitor aggravates immune-related pneumonitis of the non-irradiated lung in a preclinical model.

e14569 Background: The combination of radiation with PD-1 inhibitors for lung cancer is a trend. However, the combination is limited by immune-related adverse effects, particularly checkpoint inhibitor pneumonitis (CIP). The incidence and the mechanism of CIP of the non-irradiated lung caused by radiation plus PD-1 inhibitors remain unknown. This study was designed to evaluate the incidence of CIP and lung tissue morphology in the preclinical model induced by radiation combined with a PD-1 inhibitor (αPD-1). Methods: Fifty-four C57BL/6 mice were divided randomly into the normal group, the irradiation combined with the αPD-1 group (RT + αPD-1 group), and the single irradiation group (RT group). Mice in the RT + αPD-1 group were treated with right lung irradiation (8 Gy once) on day1 and anti-mouse PD-1 monoclonal antibody three times a week. Mice in the RT group received right lung irradiation alone. The mice were euthanized on day10, day15, and day20 after the end RT. Lung tissue morphology and pathological changes were assessed by hematoxylin-eosin staining. Lung fibrosis was evaluated by Masson staining and analysis of hydroxyproline. Results: Histopathological examination revealed that the inflammation in the irradiated lung is more severe than the unirradiated site. With the extension of time, the lung inflammation of mice in the RT group and RT + αPD-1 group was significantly aggravated, and the whole lung fibrosis appeared on day20. Inflammatory infiltrate scores, alveoli deformation scores, collagen volume fractions, and hydroxyproline contents in lung tissues were all significantly higher in mice administered αPD-1 plus irradiation than in the other groups. In particular, the inflammation is significantly worse in the unirradiated site of the mice administered PD-1 inhibitor plus irradiation than in the RT group on day15 and day20. Conclusions: Radiotherapy combined with PD-1 inhibitors could aggravate CIP on both sides. Further studies on the mechanism are under investigation. Our findings highlight the potential risk of CIP in non-irradiated lung in patients treated with radiotherapy and PD-1 inhibitors. Research Sponsor: This work was supported by the National Natural Science Foundation of China [No. 81972853, No. 81572279] and Clinical Research Startup Program of Southern Medical University by High-level University Construction Funding of Guangdong Provincial Department of Education (LC2019ZD009).

Anti PD-1 monoclonal antibody in patients with MSI-high and/or high tumor mutational burden for solid malignancies.

e15539 Background: High microsatellite instability (MSI-H) tumors have been associated with good responses to check-point inhibitors (CPI). With overall response rates (ORR) ranging between 36-46% among colorectal cancer (CRC) and other solid malignancies. Data regarding predictors of response and responses in non-CRC malignancies remains limited. We sought to evaluate the response to PD-1/PDL-1 CPI in patients with MSI-H and/or high TMB solid malignancies. Methods: Retrospective analysis of 16 patients (pts) who received 18 CPI-based therapies between October 2017 and February 2022. MSI-H and TMB status was assessed by CARIS, Guardant360 or INVITAE genetic testing. Primary objective was to determine objective response rate (ORR), defined as complete response (CR) or partial response (PR) by RECIST1.1. Secondary outcomes included progression-free survival(PFS); overall survival (OS), and duration of overall response (DOR). Results: A total of 16 pts were included. The median age of 72 years (range 53-83), 44% were male and 75% Hispanic. 44% of pts had RCR and 50% were previously treated, and 50% were stage IV at diagnosis. The most common mutations were BRCA2 31%, PIK3cA 31%, KRAS 25%, and GNAS 25%. The majority of pts received single-agent CPI therapy (72%). After a median follow-up of 52 months, 11 pts continued to receive therapy, 2 pts completed treatment. 3 pts died from progression of the disease. 1 pts switched from single-agent pembrolizumab to nivolumab-ipilimumab combination followed by nivolumab maintenance due to disease progression. 15 pts were evaluable for response with an ORR of 33%, including 33% among pts with CRC and 27% for non-CRC malignancies. (Table - Response rates) The OS was not reached (NR), with a PFS of 53 months (PFS of 64% at 1 year and 56% at 4 years). The median DOR was not reached (NR). The treatment was well tolerated and pts received a median of cycles was 19 (range 3-51) with no discontinuations due to toxicities. The molecular mutations, clinical characteristics, type of malignancy, MSI-H, or H-TMB status were not significantly associated with response to CPI after logistical regression analysis. Conclusions: CPIs are an effective treatment option for patients with MSI-H and/or High TMB, with an ORR of 33%. However, pts achieved durable responses, with a median DOR not reached. We identify a higher incidence of SD rates among CRC pts (67% vs. 18% non-CRC). We did not identify any predictors associated with response to CPI, likely due to the small number of pts. However, there was a tendency to highest response rates among pts with MSI-H and high TMB.[Table: see text]

MTDH antisense oligonucleotides reshape the immunosuppressive tumor microenvironment to sensitize Hepatocellular Carcinoma to immune checkpoint blockade therapy

Immune checkpoint blockade (ICB) therapy is an important treatment option for individuals with cancer, but it has certain limitations. Identifying a better target that can overcome tumor immune escape and stimulate T cell activity is critical. This research aimed to delve into the molecular mechanism underlying the immunoregulatory function of metadherin (MTDH), which is a novel and potential therapeutic target in hepatocellular cancer (HCC). A small interfering RNA library was screened using the luciferase reporter assay and PD-L1 promoter. The Cancer Genome Atlas database and HCC tissues were used to investigate the relationship between MTDH and PD-L1. The association between MTDH and β-catenin/lymphoid enhancer binding factor (LEF-1) was discovered by co-immunoprecipitation. The chromatin immunoprecipitation assay was used to investigate the interaction of MTDH with the PD-L1 promoter when LEF-1 expression was silenced. Locked nucleic acid antisense oligonucleotides (ASOs) were used to inhibit MTDH. We utilized in vitro co-cultures and in vivo syngeneic tumor development experiments to confirm the effectiveness of MTDH ASO combined with PD-1 monoclonal antibody (mAb). MTDH was demonstrated to be a PD-L1 modulator. MTDH increased PD-L1 expression and upregulated PD-L1 transcriptional activity through β-catenin/LEF-1 signaling. More importantly, MTDH ASO improved the anti-PD-1 response and increased cytotoxic T-cell infiltration in PD-1 mAb-treated malignancies. MTDH effectively predicts the therapeutic efficacy of ICB therapy. Our results imply that combining MTDH ASO with PD-1 mAb could be a promising therapeutic strategy for HCC. In addition, MTDH is a potential novel biomarker for predicting the effectiveness of immune checkpoint inhibitor treatment.

Preclinical Studies of a Novel Human PD-1 B-Cell Peptide Cancer Vaccine PD1-Vaxx From BALB/c Mice to Beagle Dogs and to Non-Human Primates (Cynomolgus Monkeys)

Immunotherapy with monoclonal antibodies to checkpoint inhibitors against the PD-1/PD-L1 signaling pathway is a landmark achievement in cancer therapy. Some anti-PD-1 inhibitors such as nivolumab and pembrolizumab have shown clinical success, in a percentage of patients with prolonged survival rates. However, adverse effects accompany these benefits. In this case, strategies with lower toxicity and increased specificity are urgently required. Cancer vaccines have the ability to stimulate the native immune system and in particular, an engineered B-cell epitope can elicit high-affinity polyclonal antibodies with similar efficacy to PD-1 monoclonal antibodies in murine animal models. We have previously designed and synthesized a unique B-cell vaccine, PD1-Vaxx [MVF-PD-1(92-110)], and we have tested the immunogenicity and antitumor properties in CT26 colon cancer BALB/c syngeneic mice model. This manuscript provides results from comprehensive preclinical pharmacology studies encompassing primary and secondary pharmacodynamics, biodistribution, and safety studies. The results from these preclinical studies support the use of PD1-Vaxx in a first-in-human clinical trial in patients with non-small cell lung cancer (NSCLC). A phase I trial in patients with NSCLC has commenced.

The Effect of Anlotinib Combined with anti-PD-1 in the Treatment of Gastric Cancer.

BackgroundProtein tyrosine kinase (PTK) signaling pathway has been confirmed to be involved in the proliferation, differentiation and migration of tumor cells. Anlotinib, as a multi-target tyrosine kinase inhibitor, which can inhibit the expression of vascular endothelial growth factor receptor (VEGFR), has been confirmed to have significant therapeutic effects on non-small cell lung cancer, medullary thyroid carcinoma, and soft tissue sarcoma, but the therapeutic effect on gastric cancer (GC) is still unclear.MethodsAnlotinib was screened out of 880 drugs through Cell Counting Kit 8 (CCK-8) technology. TCGA was used to detect the expression of VEGFR in GC, and Kaplan-Meier Plotter was used to analyze the correlation between the expression of VEGFR and the survival rate of GC patients. The impacts exerted by anlotinib to GC cell proliferating, migrating and invading processes were assessed through wound healing assay, transwell assay, and proliferation assay in vitro. In vivo experiments of GC were performed in C57/B6 mouse model to evaluate the function of anlotinib and PD-1 antibody.ResultsIt was found from more than compunds that anlotinib has a significant inhibitory effect on GC cells. In vitro experiments show that anlotinib can significantly inhibit the proliferation, invasion and proliferation of GC cells. The expression level of VEGFR is related to the prognosis and survival of GC. GC patients with low expression of VEGFR have better survival. Anlotinib can inhibit the expression of PD-L1, and achieve better therapeutic effects after combined with PD-1 antibody.ConclusionThe present study reveals that anlotinib down regulates PD-L1. The combination of anlotinib and PD-1 monoclonal antibody is beneficial to GC therapy.

Camrelizumab: an investigational agent for hepatocellular carcinoma

ABSTRACT Introduction : Although many approaches have been used to treat hepatocellular carcinoma (HCC), the clinical benefits were limited, particularly for advanced HCC. However, recent treatments with PD-1/PD-L1 inhibitor monotherapy and its combination with other therapies, have demonstrated remarkable results. Camrelizumab, a selective, humanized, high-affinity IgG4 PD-1 monoclonal antibody, has been approved as a second-line treatment in patients with advanced HCC by NMPA in China. Areas covered : This paper introduces anti-PD-1/PD-L1 immunotherapies for advanced HCC and progresses to discuss the pharmacology, safety, and efficacy of camrelizumab in the treatment of advanced HCC. It also considers future research directions for camrelizumab in this setting. Expert opinion : The PD-1 binding epitope of camrelizumab is different from other PD-1 inhibitors. The IC50 and EC50 of camrelizumab for inhibiting the binding of PD-1 and PD-L1 is similar to pembrolizumab, is significantly lower than other PD-1 inhibitors, and has a higher affinity for PD-1 site. Camrelizumab exhibits a promising antitumor activity and an acceptable safety profile similar to other PD-1 inhibitors in advanced HCC. Apatinib (a VEGFR-2 tyrosine kinase inhibitor) can reduce the incidence of camrelizumab-specific reactive cutaneous capillary endothelial proliferation (RCCEP).

43P Update on long term outcome of a multicentre, prospective, real-world study of camrelizumab in the treatment of patients with advanced lung cancer

Camrelizumab is a humanized PD-1 monoclonal antibody. We sought to analyse the antitumour activity and toxicity of camrelizumab in advanced lung cancer to explore benefit subgroups and optimal treatments. Preliminary data had been previously presented.

Combined angiogenesis and PD-1 inhibition for immunomodulatory TNBC: concept exploration and biomarker analysis in the FUTURE-C-Plus trial

BackgroundImmune checkpoint inhibitors had a great effect in triple-negative breast cancer (TNBC); however, they benefited only a subset of patients, underscoring the need to co-target alternative pathways and select optimal patients. Herein, we investigated patient subpopulations more likely to benefit from immunotherapy and inform more effective combination regimens for TNBC patients.MethodsWe conducted exploratory analyses in the FUSCC cohort to characterize a novel patient selection method and actionable targets for TNBC immunotherapy. We investigated this in vivo and launched a phase 2 trial to assess the clinical value of such criteria and combination regimen. Furthermore, we collected clinicopathological and next-generation sequencing data to illustrate biomarkers for patient outcomes.ResultsCD8-positivity could identify an immunomodulatory subpopulation of TNBCs with higher possibilities to benefit from immunotherapy, and angiogenesis was an actionable target to facilitate checkpoint blockade. We conducted the phase II FUTURE-C-Plus trial to assess the feasibility of combining famitinib (an angiogenesis inhibitor), camrelizumab (a PD-1 monoclonal antibody) and chemotherapy in advanced immunomodulatory TNBC patients. Within 48 enrolled patients, the objective response rate was 81.3% (95% CI, 70.2–92.3), and the median progression-free survival was 13.6 months (95% CI, 8.4–18.8). No treatment-related deaths were reported. Patients with CD8- and/or PD-L1- positive tumors benefit more from this regimen. PKD1 somatic mutation indicates worse progression-free and overall survival.ConclusionThis study confirms the efficacy and safety of the triplet regimen in immunomodulatory TNBC and reveals the potential of combining CD8, PD-L1 and somatic mutations to guide clinical decision-making and treatments.Trial registrationClinicalTrials.gov: NCT04129996. Registered 11 October 2019.

KMT2C is a Potential Biomarker of Anti-PD-1 Treatment Response in Metastatic Melanoma.

Metastatic melanoma (MM) represents a common malignancy with poor prognosis. Immune checkpoint inhibition (ICI), including PD-1 blockade, has been emerging as the popular therapeutic in MM for its durable treatment effect, but its response rate is still limiting. We comprehensively analyzed the associations between KMT2C somatic mutation and the tumor microenvironment as well as the ICI response of MM patients based on three published cohorts. Gene differential expression analysis between tumor samples with mutated and wild-type KMT2C was performed by DESeq2 package. Functional enrichment analysis was conducted by using clusterProfiler package. Kaplan-Meier was used to perform overall survival probability estimate through survival package and rms package was applied for the construction of nomogram model. We report here that KMT2C is a potential biomarker for anti-PD-1 treatment in MM. This biomarker can be used for comprehensively analyzing its association with patients' prognosis, tumor microenvironment and genomic features. Mutations of KMT2C profoundly altered expression of immune- and DNA replication-related genes in MM tumors. MM patients harboring KMT2C mutations showed significantly better overall survival (OS) after treatment with PD-1 monoclonal antibody as compared to wild-type KMT2C. Although KMT2C mutation has no significant influence on immune cell infiltration into MM tumors, the tumor mutation load and neoantigen load are indeed elevated in KMT2C mutated MM samples. This might represent a possible pathway through which KMT2C regulates the response of MM patients to anti-PD-1 treatment. Finally, we constructed a nomogram model by combing the independent prognostic factors, including KMT2C mutation, which could effectively predict the 1-year survival probability of MM patients after anti-PD-1 treatment. In conclusion, we report the role of KMT2C in anti-PD-1 treatment response regulation in MM for the first time. This may consequently be helpful for KMT2C personalized application.

EEF2K promotes PD-L1 stabilization through inactivating GSK3β in melanoma

BackgroundImmune checkpoint blockade (ICB) targeting programmed death ligand-1 (PD-L1)/programmed cell death protein-1 (PD-1) pathway has become an attractive strategy for cancer treatment; however, unsatisfactory efficacy has limited its clinical benefits....

Anti-PD-1 Monoclonal Antibody Combined With Anti-VEGF Agent Is Safe and Effective in Patients With Recurrent/Metastatic Head and Neck Squamous Cancer as Second-Line or Beyond Treatment.

BackgroundNumerous preclinical studies have revealed the complex regulatory mechanisms between anti-angiogenesis and immune inhibition in the tumor immune microenvironment and have proposed the efficacy of combined immunotherapy and anti-angiogenic treatment. Moreover, the combination strategy had been confirmed in a number of clinical trials. In this study, we aimed to evaluate the safety and efficacy of this combination strategy in recurrent/metastatic head and neck squamous cell carcinoma.MethodsIn this real-world study, 43 patients who received the combination of programmed cell death protein 1 (PD-1) inhibitors and anti-vascular endothelial growth factor (VEGF) agents in Zhejiang cancer hospitals between March 2019 and December 2020 were reviewed. Clinical characteristics and follow-up data were collected, and the preliminary efficacy and safety of the combination therapy were assessed.ResultsThe median follow-up time was 12.4 months (range, 3.7-25.3 months), and the follow-up rate was 100%. The median duration of exposure was 9.5 months. Thirty-seven patients (86.0%) reported treatment-related adverse events (TRAEs) of any grade. The most frequently reported events were fatigue, decreased appetite, and hypertension. Grade 3 TRAEs occurred in 8 patients (18.6%), and no grade 4 or 5 TRAEs occurred. Twenty-four patients (55.9%) had an overall response to treatment: 6 (14.0%) had a complete response and 18 (41.9%) had a partial response. In addition, 5 (11.6%) patients had stable disease, and the disease control rate 12 was 67.4%. The median time to response was 1.6 months (range, 1.1-2.8 months). The median progression-free survival (PFS) was not reached, and the 1-year PFS rate was 69.1%. The 1-year overall survival (OS) rate was 87.7%. Patients with primary tumors located in the nasopharynx had better OS than those with tumors outside the nasopharynx. ECOG PS were related to PFS; patients with an ECOG PS of 0 had a slight survival advantage.ConclusionThe combination strategy of anti–PD-1 monoclonal antibodies and anti-VEGF agents was tolerable in patients with recurrent/metastatic head and neck cancer. This treatment exhibited antitumor potential despite the heavily pretreated population.

Dietary Lactobacillus-Derived Exopolysaccharide Enhances Immune-Checkpoint Blockade Therapy.

Gut microbiota- and probiotic-derived metabolites are attractive agents to augment the efficacy of immunotherapies. Here we demonstrated that dietary consumption of Lactobacillus-derived exopolysaccharide induced CCR6+ CD8+ T cells in Peyer's patches and improved the tumor microenvironment to augment the therapeutic effects of immune-checkpoint blockade against CCL20-producing tumors. See related commentary by Di Luccia and Colonna, p. 1189. This article is highlighted in the In This Issue feature, p. 1171.

Anti-PD-1 Therapy Reverses HIV Latency in Patients with HIV and Cancer.

Anti-PD-1 monoclonal antibodies reversed HIV latency in CD4+ T cells after the first infusion.

LncRNA IFITM4P promotes immune escape by up-regulating PD-L1 via dual mechanism in oral carcinogenesis

Oral squamous cell carcinoma (OSCC), which is typically preceded by oral leukoplakia (OL), is a common malignancy with poor prognosis. However, the signaling molecules governing this progression remain to be defined. Based on microarray analysis of genes expressed in OL and OSCC samples, we discovered that the long non-coding RNA IFITM4P was highly expressed in OSCC, and ectopic expression or knockdown of IFITM4P resulted in increased or decreased cell proliferation invitro and in xenografted tumors, respectively. Mechanistically, in the cytoplasm IFITM4P acted as a scaffold to facilitate recruiting SASH1 to bind and phosphorylate TAK1 (Thr187), and in turn to increase the phosphorylation of nuclear factor κB (Ser536) and concomitant induction of PD-L1 expression, resulting in activation of an immunosuppressive program that allows OL cells to escape anti-cancer immunity in cytoplasm. In nucleus, IFITM4P reduced Pten transcription by enhancing the binding of KDM5A to the Pten promoter, thereby upregulating PD-L1 in OL cells. Moreover, mice bearing tumors with high IFITM4P expression had notable therapeutic sensitivity to PD-1 monoclonal antibody (mAb) treatment. Collectively, these data demonstrate that IFITM4P may serve as a new therapeutic target in blockage of oral carcinogenesis, and PD-1 mAb can be an effective reagent to treat OSCC.

Identification of Key Pathways and Genes Related to Immunotherapy Resistance of LUAD Based on WGCNA Analysis.

Immunotherapy resistance is a major barrier in the application of immune checkpoint inhibitors (ICI) in lung adenocarcinoma (LUAD) patients. Although recent studies have found several mechanisms and potential genes responsible for immunotherapy resistance, ways to solve this problem are still lacking. Tumor immune dysfunction and exclusion (TIDE) algorithm is a newly developed method to calculate potential regulators and indicators of ICI resistance. In this article, we combined TIDE and weighted gene co-expression network analysis (WGCNA) to screen potential modules and hub genes that are highly associated with immunotherapy resistance using the Cancer Genome Atlas (TCGA) dataset of LUAD patients. We identified 45 gene co-expression modules, and the pink module was most correlated with TIDE score and other immunosuppressive features. After considering the potential factors in immunotherapy resistance, we found that the pink module was also highly related to cancer stemness. Further analysis showed enriched immunosuppressive cells in the extracellular matrix (ECM), immunotherapy resistance indicators, and common cancer-related signaling pathways in the pink module. Seven hub genes in the pink module were shown to be significantly upregulated in tumor tissues compared with normal lung tissue, and were related to poor survival of LUAD patients. Among them, THY1 was the gene most associated with TIDE score, a gene highly related to suppressive immune states, and was shown to be strongly expressed in late-stage patients. Immunohistochemistry (IHC) results demonstrated that THY1 level was higher in the progressive disease (PD) group of LUAD patients receiving a PD-1 monoclonal antibody (mAb) and positively correlated with SOX9. Collectively, we identified that THY1 could be a critical biomarker in predicting ICI efficiency and a potential target for avoiding tumor immunotherapy resistance.

Evaluation of Short‐Term Efficacy of PD‐1 Monoclonal Antibody Immunotherapy for Lymphoma by Positron Emission Tomography/Computed Tomography Imaging with Convolutional Neural Network Image Registration Algorithm

The objective of this study was to investigate the value of PET/CT imaging based on CNN image registration algorithm in evaluating the short-term efficacy of PD-1 monoclonal antibody immunotherapy for lymphoma. 36 patients with advanced lymphoma confirmed by histology or cytochemistry and treated with PD-1 monoclonal antibody admitted to hospital were included. In addition, 38 normal controls were from healthy volunteers. All patients were treated with PD-1 monoclonal antibody intravenous infusion, and the image data were processed by CT with intelligent segmentation algorithm. Medication method: nivolumab 3 mg/kg for 2 weeks; pembrolizumab 2 mg/kg for 3 weeks; and continuous medication until tumor progression or unacceptable adverse reactions. Efficacy was evaluated every 3 cycles. Imaging examinations were performed after 3 weeks of medication to evaluate the therapeutic effect. The concentrations of IL-2, IL-7, basic fibroblast growth factor (FGF), granulocyte-macrophage colony-stimulating factor (GM-CSF), platelet-derived growth factor (PDGF-bb), and other factors in the normal control group were significantly higher than those in the advanced lymphoma patients, and the differences were statistically significant (P < 0.05). The PET/CT imaging automatic segmentation accuracy of the CNN image registration algorithm was greater than 81%, and 27 patients were treated for more than 3 cycles, including 1 case of partial remission (PR) (3.7%), 16 cases of stable disease (SD) (59.3%) after 3 cycles of treatment, and 10 cases of progressive disease (PD) (37%). After 6 cycles of treatment, 1 case was PR (8.3%), 7 cases were SD (58.4%), and 4 cases were PD (33.3%). Adverse reactions included fever, fatigue, gastrointestinal reactions, hypothyroidism, and interstitial pneumonia. PD-1 monoclonal antibody immunotherapy had a certain short-term effect on lymphoma.

Effect of PD-1 Inhibitor Combined with X-Ray Irradiation on the Inflammatory Microenvironment and Lung Tissue Injury in Mice.

PurposeThis study was designed to evaluate the effects of PD-1 inhibitor on lung tissue morphology and the immune system in a mouse model of radiation-induced lung injury (RILI) and to assess interactions between radiation therapy and PD-1 inhibition.MethodsTwenty C57BL/6 mice were divided randomly into four groups of five mice each. Mice were treated with an anti-mouse PD-1 monoclonal antibody, whole thorax irradiation, both or neither. Lung tissue morphology and pathological changes were assessed by hematoxylin-eosin staining; lung fibrosis was assessed by Masson staining and analysis of hydroxyproline; CD3+, CD4+, and CD8+ T lymphocytes in lung tissues were detected immunohistochemically; and the concentrations of transforming growth factor-β1 (TGF-β1) and interleukin-6 (IL-6) in lung tissue were evaluated by cytokine multiplex analysis.ResultsLung injury scores and indicators of pulmonary fibrosis were higher in mice administration whole thorax irradiation than in control mice. Inflammatory infiltrate scores, alveoli deformation scores, collagen volume fractions and hydroxyproline contents in lung tissues were all significantly higher in mice administered PD-1 inhibitor plus irradiation than in the other three groups. Similarly, the percentages of CD3+ and CD8+T cells and the concentrations of IL-6 and TGF-β1 in lung tissue were significantly higher in mice treated with radiation and PD-1 inhibitor than in the other groups. However, PD-1 inhibitor and irradiation interacted significantly only in the elevation of TGF-β1 level.ConclusionWhole thorax X-ray irradiation in mice can cause pulmonary injury and fibrosis, which could be exacerbated by PD-1 inhibitors. Radiotherapy combined with PD-1 inhibitors may aggravate RILI by synergistically upregulating TGF-β1 expression, thereby affecting the immune-inflammatory microenvironment in the lungs.

Abstract P103: The introduction of a single strain of Bacillus into a germ-free environment did not impact the anti-PD-1 efficacy in a MC38 syngeneic model

Abstract Background. Although immunotherapy has led to exceptional and durable clinical response, the majority of patients respond poorly to the current immunotherapies. Growing evidence has linked some of the poor responsiveness to the gut microbiota, and the modulation of gut microbiome composition is becoming a promising new strategy to enhance immune checkpoint inhibitor (ICI) treatment outcome. Mouse tumor modelling under germ-free (GF) conditions combined with introduction of defined bacterial strains could be a useful approach to investigate the impact of microbiota on ICI efficacy, as well as understanding the underlying mechanisms. We previously demonstrated that GF mice exhibited a significantly poor response to anti-PD-1 therapy when compared to the specific pathogen free (SPF) mice in a subcutaneous MC38 colorectal cancer model, which is consistent with other reports. Methods. Introduction of a single strain of Bacillus in the GF-environment was assessed for its impact on the anti-mouse PD-1 monoclonal antibody (mAb) therapy in GF-mice and SPF mice, both for efficacy and pharmacodynamics tumor infiltrating lymphocytes (TILs) profiling. C57BL/6 mice were inoculated subcutaneously with MC38 tumor cells and when the tumors were reached 80-120mm3, the mice were randomized for isotype or anti-PD-1 mAb treatment. Fecal sample 16S rRNA analysis (NGS) was used to confirm the gut bacteria status. Results. The MC38 tumor in GF mice has significantly fast baseline growth kinetics, even with the introduction of Bacillus under GF conditions compared to SPF mice, suggesting tumor immunity was not enhanced by Bacillus. Despite the introduction of Bacillus, GF mice also showed reduced response to anti-PD-1 treatment when compared to the SPF mice as previously reported, further confirming that introduction of Bacillus had minimal effects on the efficacy of anti-PD-1 therapy. Moreover, the SPF mice and GF mice with Bacillus exhibited distinct profiles of TILs, consistent with distinct efficacies as observed. GF free mice showed a lower frequency of CD45+ TILs in comparison to SPF mice. In addition, GF mice exhibited lower frequency of CD8+ TILs and TIL- NKT when compared to the SPF mice, both of which are consistent with the stronger efficacy seen in SPF mice. Meanwhile, GF mice also exhibited higher granulocytic myeloid derived suppressor cells (gMDSC) and lower M1/M2 ratio, both of which imply a more suppressive tumor microenvironment in GF mice. Fecal sample analysis using 16S rRNA analysis confirmed a single strain of Bacillus was indeed introduced into the guts of all the GF mice. Conclusions. The GF conditions provide a useful environment for the investigation of specific microbiota strains on the impact on ICI treatment outcome. In summary, the introduction of Bacillus in GF mice did not impact the efficacy of anti-PD-1, thus suggesting that other strain(s) of gut microbiota in SPF mice may impact this and need to be investigated. Citation Format: Tao Yang, Bonnie Xiaobo Chen, Rongfei Lu, Xiaoyu An, Mingfa Zang, Jingjun Li, Sheng Guo, Wubin Qian, Jian Fei, Tongyang Hao, Edward Xu, Henry Li. The introduction of a single strain of Bacillus into a germ-free environment did not impact the anti-PD-1 efficacy in a MC38 syngeneic model [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P103.

116TiP KEYNOTE-B98: Phase Ib/II study of pembrolizumab plus investigational agents as second-line treatment for anti–PD-1/PD-L1-refractory extensive-stage small cell lung cancer (ES-SCLC)

Immune checkpoint inhibitors plus platinum chemotherapy are first-line standard-of-care therapy for ES-SCLC. Treatment options for patients who progress after first-line therapy have limited efficacy. The anti–PD-1 monoclonal antibody (mAb) pembrolizumab has demonstrated antitumor activity as monotherapy in patients who have received prior therapy for advanced SCLC in the KEYNOTE-028 and KEYNOTE-158 studies. KEYNOTE-B98 (NCT04938817) is a randomized, phase 1b/2, rolling-arm, multicenter, open-label study evaluating pembrolizumab plus investigational agents as second-line therapy in patients with anti–PD-1/PD-L1 refractory ES-SCLC.

A competitive ligand-binding assay for the detection of neutralizing antibodies against dostarlimab (TSR-042)

Dostarlimab is a humanized anti–PD-1 monoclonal antibody. Dostarlimab (JEMPERLI; TSR-042) was recently approved in the USA and in the EU. The presence of neutralizing antibodies (NAbs) is a cause for concern because they block the therapeutic function of the antibody and reduce drug efficacy. Therefore, programs developing therapeutic biologics need to develop and validate assays that adequately assess the presence of NAbs in the serum of patients treated with biologic therapies. Presented here is the development and validation of a competitive ligand-binding assay that specifically detects anti-dostarlimab NAbs in human serum. Precision, sensitivity, hook effect, selectivity, assay robustness, stabilities, and system suitability were evaluated. In addition, drug tolerance of the assay with the implementation of a drug removal process was investigated. The cut point factor for the detection of NAbs in human serum at a 1% false-positive rate was determined. The assay’s precision, sensitivity, hook effect, selectivity, robustness, and drug interference were tested and found to be acceptable. With system suitability and stability established, this assay has been used to evaluate NAbs to guide the development of dostarlimab.Trial registration: Clinicaltrials.gov, NCT02715284. Registered 9 March 2016