Microbiome influencers of checkpoint blockade-associated toxicity

Role of gut microbiome in the outcome of lymphoma patients treated with checkpoint inhibitors-The MicroLinf Study

Biomarkers for immune checkpoint inhibitors (ICIs) response and resistance include PD-L1 expression and other environmental factors, among which the gut microbiome (GM) is gaining increasing interest especially in lymphomas. To explore the potential role of GM in this clinical issue, feces of 30 relapsed/refractory lymphoma (Hodgkin and primary mediastinal B-cell lymphoma) patients undergoing ICIs were collected from start to end of treatment (EoT). GM was profiled through Illumina, that is, 16S rRNA sequencing, and subsequently processed through a bioinformatics pipeline. The overall response rate to ICIs was 30.5%, with no association between patients clinical characteristics and response/survival outcomes. Regarding GM, responder patients showed a peculiar significant enrichment of Lachnospira, while non-responder ones showed higher presence of Enterobacteriaceae (at baseline and maintained till EoT). Recognizing patient-related factors that may influence response to ICIs is becoming critical to optimize the treatment pathway of heavily pretreated, young patients with a potentially long-life expectancy. These preliminary results indicate potential early GM signatures of ICIs response in lymphoma, which could pave the way for future research to improve patients prognosis with new adjuvant strategies.

Review article: Contemporary management of gastrointestinal, pancreatic and hepatic toxicities of immune checkpoint inhibitors

BACKGROUND

Immune checkpoint inhibitors (ICIs) are effective oncologic agents which frequently cause immune-related adverse events (irAEs) which can impact multiple organ systems. Onco-Gastroenterology is a novel and emerging subspecialty within gastroenterology focused on cancer treatment-related complications. Gastroenterologists must be prepared to identify and manage diverse immune-mediated toxicities including enterocolitis, hepatitis, pancreatitis and other ICI-induced toxicities.

AIM

To provide a narrative review of the epidemiology, diagnostic evaluation and management of checkpoint inhibitor-induced gastrointestinal and hepatic toxicities.

METHODS

We searched Cochrane and PubMed databases for articles published through August 2023.

RESULTS

Gastrointestinal and hepatic irAEs include most commonly enterocolitis and hepatitis, but also pancreatitis, oesophagitis, gastritis, motility disorders (gastroparesis) and other rarer toxicities. Guidelines from the National Comprehensive Cancer Network, American Society of Clinical Oncology and European Society for Medical Oncology, in combination with emerging cohort and clinical trial data, offer strategies for management of ICI toxicities. Evaluation of irAEs severity by formal classification and clinical stability, and a thorough workup for alternative etiologies which may clinically mimic irAEs underlie initial management. Treatments include corticosteroids, biologics and other immunosuppressive agents plus supportive care; decisions on dosing, timing and choice of steroid adjuncts and potential for subsequent checkpoint inhibitor dosing are nuanced and toxicity-specific.

CONCLUSIONS

Expanding clinical trial and cohort data have clarified the epidemiology and clinical characteristics of gastrointestinal, pancreatic and hepatic toxicities of ICIs. Guidelines, though valuable, remain based principally on retrospective cohort data. Quality prospective, controlled studies may refine algorithms for treatment and potential immunotherapy rechallenge.

Reduction of product composition variability using pooled microbiome ecosystem therapy and consequence in two infectious murine models

Growing evidence demonstrates the key role of the gut microbiota in human health and disease. The recent success of microbiotherapy products to treat recurrent Clostridioides difficile infection has shed light on its potential in conditions associated with gut dysbiosis, such as acute graft-versus-host disease, intestinal bowel diseases, neurodegenerative diseases, or even cancer. However, the difficulty in defining a "good" donor as well as the intrinsic variability of donor-derived products' taxonomic composition limits the translatability and reproducibility of these studies. Thus, the pooling of donors' feces has been proposed to homogenize product composition and achieve higher taxonomic richness and diversity. In this study, we compared the metagenomic profile of pooled products to corresponding single donor-derived products. We demonstrated that pooled products are more homogeneous, diverse, and enriched in beneficial bacteria known to produce anti-inflammatory short chain fatty acids compared to single donor-derived products. We then evaluated pooled products' efficacy compared to corresponding single donor-derived products in Salmonella and C. difficile infectious mouse models. We were able to demonstrate that pooled products decreased pathogenicity by inducing a structural change in the intestinal microbiota composition. Single donor-derived product efficacy was variable, with some products failing to control disease progression. We further performed in vitro growth inhibition assays of two extremely drug-resistant bacteria, Enterococcus faecium vanA and Klebsiella pneumoniae oxa48, supporting the use of pooled microbiotherapies. Altogether, these results demonstrate that the heterogeneity of donor-derived products is corrected by pooled fecal microbiotherapies in several infectious preclinical models.IMPORTANCEGrowing evidence demonstrates the key role of the gut microbiota in human health and disease. Recent Food and Drug Administration approval of fecal microbiotherapy products to treat recurrent Clostridioides difficile infection has shed light on their potential to treat pathological conditions associated with gut dysbiosis. In this study, we combined metagenomic analysis with in vitro and in vivo studies to compare the efficacy of pooled microbiotherapy products to corresponding single donor-derived products. We demonstrate that pooled products are more homogeneous, diverse, and enriched in beneficial bacteria compared to single donor-derived products. We further reveal that pooled products decreased Salmonella and Clostridioides difficile pathogenicity in mice, while single donor-derived product efficacy was variable, with some products failing to control disease progression. Altogether, these findings support the development of pooled microbiotherapies to overcome donor-dependent treatment efficacy.

Biomarkers for immune-related adverse events in cancer patients treated with immune checkpoint inhibitors

Although immune checkpoint inhibitors have greatly improved cancer therapy, they also cause immune-related adverse events, including a wide range of inflammatory side effects resulting from excessive immune activation. Types of immune-related adverse events are diverse and can occur in almost any organ, with different frequencies and severities. Furthermore, immune-related adverse events may occur within the first few weeks after treatment or even several months after treatment discontinuation. Predictive biomarkers include blood cell counts and cell surface markers, serum proteins, autoantibodies, cytokines/chemokines, germline genetic variations and gene expression profiles, human leukocyte antigen genotype, microRNAs and the gut microbiome. Given the inconsistencies in research results and limited practical utility, there is to date no established biomarker that can be used in routine clinical practice, and additional investigations are essential to demonstrate efficacy and subsequently facilitate integration into routine clinical use.

Univariable and multivariable Mendelian randomization study identified the key role of gut microbiota in immunotherapeutic toxicity

BACKGROUND

In cancer patients receiving immune checkpoint inhibitors (ICIs), there is emerging evidence suggesting a correlation between gut microbiota and immune-related adverse events (irAEs). However, the exact roles of gut microbiota and the causal associations are yet to be clarified.

METHODS

To investigate this, we first conducted a univariable bi-directional two-sample Mendelian randomization (MR) analysis. Instrumental variables (IVs) for gut microbiota were retrieved from the MiBioGen consortium (18,340 participants). GWAS summary data for irAEs were gathered from an ICIs-treated cohort with 1,751 cancer patients. Various MR analysis methods, including inverse variance weighted (IVW), MR PRESSO, maximum likelihood (ML), weighted median, weighted mode, and cML-MA-BIC, were used. Furthermore, multivariable MR (MVMR) analysis was performed to account for possible influencing instrumental variables.

RESULTS

Our analysis identified fourteen gut bacterial taxa that were causally associated with irAEs. Notably, Lachnospiraceae was strongly associated with an increased risk of both high-grade and all-grade irAEs, even after accounting for the effect of BMI in the MVMR analysis. Akkermansia, Verrucomicrobiaceae, and Anaerostipes were found to exert protective roles in high-grade irAEs. However, Ruminiclostridium6, Coprococcus3, Collinsella, and Eubacterium (fissicatena group) were associated with a higher risk of developing high-grade irAEs. RuminococcaceaeUCG004, and DefluviitaleaceaeUCG011 were protective against all-grade irAEs, whereas Porphyromonadaceae, Roseburia, Eubacterium (brachy group), and Peptococcus were associated with an increased risk of all-grade irAEs.

CONCLUSIONS

Our analysis highlights a strong causal association between Lachnospiraceae and irAEs, along with some other gut microbial taxa. These findings provide potential modifiable targets for managing irAEs and warrant further investigation.

Immune-Related Colitis Is Associated with Fecal Microbial Dysbiosis and Can Be Mitigated by Fecal Microbiota Transplantation

Colitis induced by treatment with immune-checkpoint inhibitors (ICI), termed irColitis, is a substantial cause of morbidity complicating cancer treatment. We hypothesized that abnormal fecal microbiome features would be present at the time of irColitis onset and that restoring the microbiome with fecal transplant from a healthy donor would mitigate disease severity. Herein, we present fecal microbiota profiles from 18 patients with irColitis from a single center, 5 of whom were treated with healthy-donor fecal microbial transplantation (FMT). Although fecal samples collected at onset of irColitis had comparable α-diversity to that of comparator groups with gastrointestinal symptoms, irColitis was characterized by fecal microbial dysbiosis. Abundances of Proteobacteria were associated with irColitis in multivariable analyses. Five patients with irColitis refractory to steroids and biologic anti-inflammatory agents received healthy-donor FMT, with initial clinical improvement in irColitis symptoms observed in four of five patients. Two subsequently exhibited recurrence of irColitis symptoms following courses of antibiotics. Both received a second "salvage" FMT that was, again, followed by clinical improvement of irColitis. In summary, we observed distinct microbial community changes that were present at the time of irColitis onset. FMT was followed by clinical improvements in several cases of steroid- and biologic-agent-refractory irColitis. Strategies to restore or prevent microbiome dysbiosis in the context of immunotherapy toxicities should be further explored in prospective clinical trials.

Gut microbiome for predicting immune checkpoint blockade-associated adverse events

BACKGROUND

The impact of the gut microbiome on the initiation and intensity of immune-related adverse events (irAEs) prompted by immune checkpoint inhibitors (ICIs) is widely acknowledged. Nevertheless, there is inconsistency in the gut microbial associations with irAEs reported across various studies.

METHODS

We performed a comprehensive analysis leveraging a dataset that included published microbiome data (n = 317) and in-house generated data from 16S rRNA and shotgun metagenome samples of irAEs (n = 115). We utilized a machine learning-based approach, specifically the Random Forest (RF) algorithm, to construct a microbiome-based classifier capable of distinguishing between non-irAEs and irAEs. Additionally, we conducted a comprehensive analysis, integrating transcriptome and metagenome profiling, to explore potential underlying mechanisms.

RESULTS

We identified specific microbial species capable of distinguishing between patients experiencing irAEs and non-irAEs. The RF classifier, developed using 14 microbial features, demonstrated robust discriminatory power between non-irAEs and irAEs (AUC = 0.88). Moreover, the predictive score from our classifier exhibited significant discriminative capability for identifying non-irAEs in two independent cohorts. Our functional analysis revealed that the altered microbiome in non-irAEs was characterized by an increased menaquinone biosynthesis, accompanied by elevated expression of rate-limiting enzymes menH and menC. Targeted metabolomics analysis further highlighted a notably higher abundance of menaquinone in the serum of patients who did not develop irAEs compared to the irAEs group.

CONCLUSIONS

Our study underscores the potential of microbial biomarkers for predicting the onset of irAEs and highlights menaquinone, a metabolite derived from the microbiome community, as a possible selective therapeutic agent for modulating the occurrence of irAEs.

Faecalibacterium prausnitzii Abrogates Intestinal Toxicity and Promotes Tumor Immunity to Increase the Efficacy of Dual CTLA4 and PD-1 Checkpoint Blockade

Immune checkpoint inhibitors (ICI) have revolutionized cancer therapy; however, their application is limited by the occurrence of immune-related adverse events. The gut microbiota plays important roles in the response to and toxicity of immunotherapy and Faecalibacterium prausnitzii (F. prausnitzii) has been shown to possess immunomodulatory potential. Here, we found that patients receiving ICIs who developed colitis had a lower abundance of F. prausnitzii. In vivo, immunocompetent mice administered with dextran sodium sulfate and immunodeficient NSG mice with human peripheral blood mononuclear cell transfer were treated with ICIs to study ICI-induced colitis. Dual CTLA4 and PD-1 blockade exacerbated autoimmune colitis, activated an inflammatory response, and promoted myeloid cell infiltration, with higher percentages of macrophages, dendritic cells, monocytes, and neutrophils. F. prausnitzii administration mitigated the exacerbated colitis induced by ICIs. Concomitantly, F. prausnitzii enhanced the antitumor immunity elicited by ICIs in tumor-bearing mice while abrogating colitis. In addition, administration of F. prausnitzii increased gut microbial alpha diversity and modulated the microbial composition, increasing a subset of gut probiotics and decreasing potential gut pathogens. F. prausnitzii abundance was reduced in mice that developed ICI-associated colitis. Together, this study shows that F. prausnitzii administration ameliorates ICI-induced colitis, reshapes the gut microbial composition, and enhances the antitumor activity of immunotherapy.

SIGNIFICANCE

F. prausnitzii alleviates colitis while enhancing the tumor-suppressive effects of immune checkpoint blockade, indicating that supplementation with F. prausnitzii could be a treatment strategy to mitigate immunotherapy toxicity in patients with cancer.

Manipulating the gut and tumor microbiota for immune checkpoint inhibitor therapy: from dream to reality

The past decade has witnessed a revolution in cancer treatment by shifting from conventional therapies to immune checkpoint inhibitors (ICIs). These immunotherapies unleash the host immune system against the tumor and have achieved unprecedented durable remission. However, 80% of patients do not respond. This review discusses how bacteria are unexpected drivers that reprogram tumor immunity. Manipulating the microbiota impacts on tumor development and reprograms the tumor microenvironment (TME) of mice on immunotherapy. We anticipate that harnessing commensals and the tumor microbiome holds promise to identify patients who will benefit from immunotherapy and guide the choice of new ICI combinations to advance treatment efficacy.

[Advances in Predictive Research of Immune Checkpoint Inhibitors-related Adverse Events]

The era of tumor treatment has been revolutionized by the advent of immune checkpoint inhibitors. However, while immunotherapy benefits patients, it can also lead to immune-related adverse events that may affect multiple organs and systems throughout the body, potentially even posing a life-threatening risk. The diverse clinical manifestations and onset times of these adverse events further complicate their prediction and diagnosis. The purpose of this paper is to review the clinical characteristics and predicted biomarkers of adverse events related to inhibitors at immune checkpoints, in order to help clinicians evaluate drug risks and early warn adverse events.
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Microbiota-dependent regulation of costimulatory and coinhibitory pathways via innate immune sensors and implications for immunotherapy

Our bodies are inhabited by trillions of microorganisms. The host immune system constantly interacts with the microbiota in barrier organs, including the intestines. Over decades, numerous studies have shown that our mucosal immune system is dynamically shaped by a variety of microbiota-derived signals. Elucidating the mediators of these interactions is an important step for understanding how the microbiota is linked to mucosal immune homeostasis and gut-associated diseases. Interestingly, the efficacy of cancer immunotherapies that manipulate costimulatory and coinhibitory pathways has been correlated with the gut microbiota. Moreover, adverse effects of these therapies in the gut are linked to dysregulation of the intestinal immune system. These findings suggest that costimulatory pathways in the immune system might serve as a bridge between the host immune system and the gut microbiota. Here, we review mechanisms by which commensal microorganisms signal immune cells and their potential impact on costimulation. We highlight how costimulatory pathways modulate the mucosal immune system through not only classical antigen-presenting cells but also innate lymphocytes, which are highly enriched in barrier organs. Finally, we discuss the adverse effects of immune checkpoint inhibitors in the gut and the possible relationship with the gut microbiota.

Mediators and mechanisms of immune checkpoint inhibitor-associated myocarditis: Insights from mouse and human

The broad application of immune checkpoint inhibitors (ICIs) has led to significant gains in cancer outcomes. By abrogating inhibitory signals, ICIs promote T cell targeting of cancer cells but can frequently trigger autoimmune manifestations, termed immune-related adverse events (irAEs), affecting essentially any organ system. Among cardiovascular irAEs, immune-related myocarditis (irMyocarditis) is the most described and carries the highest morbidity. The currently recommended treatment for irMyocarditis is potent immunosuppression with corticosteroids and other agents, but this has limited evidence basis. The cellular pathophysiology of irMyocarditis remains poorly understood, though mouse models and human data have both implicated effector CD8+ T cells, some of which are specific for the cardiomyocyte protein α-myosin. While the driving molecular signals and transcriptional programs are not well defined, the involvement of chemokine receptors such as CCR5 and CXCR3 has been proposed. Fundamental questions regarding why only approximately 1% of ICI recipients develop irMyocarditis and why irMyocarditis carries a much worse prognosis than other forms of lymphocytic myocarditis remain unanswered. Further work in both murine systems and with human samples are needed to identify better tools for diagnosis, risk-stratification, and treatment.

The long and winding road of faecal microbiota transplants to targeted intervention for improvement of immune checkpoint inhibition therapy

INTRODUCTION

Immune checkpoint inhibition (ICI) therapy has revolutionized the treatment of cancer. Inhibitory molecules, either on the tumor or on cells of the immune system, are blocked, allowing the immune system of the patient to attack and eradicate the tumor. Not all patients respond to ICI therapy, and response or non-response has been associated with composition of gut microbiota.

AREA COVERED

Fecal microbiota transplantation (FMT) is used as adjunctive therapy in order to improve the outcome of ICI. ClinicalTrials.gov, and other databases were searched (October 2022) for studies dealing with gut microbiota modification and the outcome of ICI.

EXPERT OPINION

There is ample evidence for the beneficial effect of FMT on the outcome of ICI therapy for cancer, especially melanoma. Progress is being made in the unraveling of the mechanisms by which microbiota and their metabolites (butyrate and the tryptophan metabolite indole-3-aldehyde) interact with the mucosal immune system of the host. A better understanding of the mechanisms involved will allow the identification of key bacterial species which mediate the effect of FMT. Promising species are Faecalibacterium prausnitzii, Eubacterium rectale, Bifidobacterium adolescentis, B. bifidum, and B. longum, because they are important direct and indirect butyrate producers.

Microbial Influences on Immune Checkpoint Inhibitor Response in Melanoma: The Interplay between Skin and Gut Microbiota

Immunotherapy has revolutionized the treatment of melanoma, but its limitations due to resistance and variable patient responses have become apparent. The microbiota, which refers to the complex ecosystem of microorganisms that inhabit the human body, has emerged as a promising area of research for its potential role in melanoma development and treatment response. Recent studies have highlighted the role of microbiota in influencing the immune system and its response to melanoma, as well as its influence on the development of immune-related adverse events associated with immunotherapy. In this article, we discuss the complex multifactorial mechanisms through which skin and gut microbiota can affect the development of melanoma including microbial metabolites, intra-tumor microbes, UV light, and the immune system. In addition, we will discuss the pre-clinical and clinical studies that have demonstrated the influence of different microbial profiles on response to immunotherapy. Additionally, we will explore the role of microbiota in the development of immune-mediated adverse events.

The effect of concomitant proton pump inhibitor use on survival outcomes of Nivolumab-treated renal cell carcinoma patients: a multicenter study

AIM

We aimed to evaluate the effect of concomitant proton pump inhibitors (PPI) use with nivolumab on survival outcomes in metastatic renal cell carcinoma (mRCC) in second-line setting.

METHODS

The study was designed as a multicenter and retrospective involving patients with metastatic renal cell carcinoma receiving second-line nivolumab therapy. One hundred and nine patients with mRCC were divided into two groups based on whether they use PPI concomitantly with nivolumab: concomitant PPI users and non-users. Overall survival (OS) and progression-free survival (PFS) were compared between the groups with and without concurrent PPIs.

RESULTS

Of 109 patients in our study, 59 were not using PPI concomitantly with nivolumab and 50 were using PPI concomitantly. The median PFS was 6.37 (5.2-7.5) months in the concomitant PPI group and 9.7 (4.5-15) months in the non-users (p = 0.03). The median OS was 14.6 (7.1-22.1) months in patients on PPI concurrently with nivolumab and 29.9 (17.1-42.7) months in the non-users (p = 0.01). Accordingly, PPI use for PFS (Non-use vs. Use = HR: 0.44, 95%Cl 0.28-0.96, p = 0.014) and PPI use for OS (Non-use vs. Use = HR: 0.68, 95%Cl 0.22-0.88, p = 0.01) were found to be as independent risk factors.

CONCLUSIONS

Concomitant use of PPIs is associated with worse survival outcomes in patients with mRCC treated with nivolumab. Clinicians should carefully consider the concomitant use of PPIs in such patients.