CYP8B1 downregulation mediates the metabolic effects of vertical sleeve gastrectomy in mice

BACKGROUND AND AIMS

Although the benefits of vertical sleeve gastrectomy (VSG) surgery are well known, the molecular mechanisms by which VSG alleviates obesity and its complications remain unclear. We aim to determine the role of CYP8B1 (cytochrome P450, family 8, subfamily B, polypeptide 1) in mediating the metabolic benefits of VSG.

APPROACH AND RESULTS

We found that expression of CYP8B1, a key enzyme in controlling the 12α-hydroxylated (12α-OH) bile acid (BA) to non-12α-OH BA ratio, was strongly downregulated after VSG. Using genetic mouse models of CYP8B1 overexpression, knockdown, and knockout, we demonstrated that overexpression of CYP8B1 dampened the metabolic improvements associated with VSG. In contrast, short hairpin RNA-mediated CYP8B1 knockdown improved metabolism similar to those observed after VSG. Cyp8b1 deficiency diminished the metabolic effects of VSG. Further, VSG-induced alterations to the 12α-OH/non-12α-OH BA ratio in the BA pool depended on CYP8B1 expression level. Consequently, intestinal lipid absorption was restricted, and the gut microbiota (GM) profile was altered. Fecal microbiota transplantation from wild type-VSG mice (vs. fecal microbiota transplantation from wild-type-sham mice) improved metabolism in recipient mice, while there were no differences between mice that received fecal microbiota transplantation from knockout-sham and knockout-VSG mice.

CONCLUSIONS

CYP8B1 is a critical downstream target of VSG. Modulation of BA composition and gut microbiota profile by targeting CYP8B1 may provide novel insight into the development of therapies that noninvasively mimic bariatric surgery to treat obesity and its complications.

Characterization of the microbial resistome in a prospective trial of CBM588 in metastatic renal cell carcinoma (mRCC) offers mechanism for interplay between antibiotic (abx) use and immune checkpoint inhibitor (ICI) activity

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Background: The negative association between ICI response and abx therapy is well defined (Derosa et al Cancer Discov 2021). Paradoxically, a retrospective assessment of the live bacterial product (LBP) CBM588 in patients (pts) with advanced lung cancer showed improved outcome with ICIs when the combination of CBM588 and abx (as compared to CBM588 alone) was employed (Tomita et al Cancer Immunol Res 2020). We postulated that the microbial resistome (genes encoding antimicrobial resistance) could shift in a manner with CBM588 therapy that facilitated ICI response. Methods: Pts with newly diagnosed mRCC with clear cell and/or sarcomatoid histology and intermediate/high risk disease per IMDC criteria were randomized to nivolumab/ipilimumab (nivo/ipi) or nivo/ipi/CBM588 in a 1:2 ratio. Stool samples were collected at baseline and week 12. Whole-metagenome sequencing was performed to analyze stool microbiome composition. Abx resistance genes (RGs) were inferred using publicly available database (McArthur et al. Antimicrob Agents Chemother 2013), and groups of abx RGs for various classes of abx were characterized. Wilcoxon signed-rank test was used for comparison of abx RG abundance between baseline and week 12 in each treatment arm and in responders (R) and non-responders (NR). Results: The study enrolled 30 pts, with the final analysis including 29 eligible pts (median age: 66 years, M:F 21:8, nivo/ipi: 19 pts, nivo/ipi/CBM588:10 pts). Objective response was 20% and 58% in nivo/ipi and nivo/ipi/CBM588 arms, respectively. The overall abundance of abx RGs remained unchanged between baseline and week 12 in pts receiving nivo/ipi alone. In contrast, a decrease in abx RGs was observed in pts receiving nivo/ipi with CBM588 arm from baseline to week 12 (p = 0.042 in Rs; p = 0.078 in NRs). More specifically, nivo/ipi/CBM588 treatment led to a significant reduction in fosfomycin RGs and nitroimidazole (e.g., metronidazole) RGs in both pts with R (p = 0.019 and 0.042, respectively) and NR (p = 0.031 and p = 0.031, respectively). A multitude of other clinically relevant abx RGs were downregulated in pts receiving CBM588, including those mediating resistance to glycopeptide (e.g., vancomycin) and lincosamide (e.g., clindamycin) abx. Conclusions: In the first interrogation of the resistome in mRCC, we demonstrate that CBM588 decreases abx RGs associated with multiple commonly used classes of abx. Abx clear commensals and increase pathogenic (abx resistant) bacteria in the gut. Based on our data, we formulate the hypothesis that combining abx with CBM588 may decrease potentially pathobionts and favor butyrogenic species, thereby improving CPI response. Clinical studies using CBM588 with abx priming may be warranted. Clinical trial information: NCT03829111.

Nivolumab/ipilimumab with or without CBM588 in metastatic renal cell carcinoma: A randomized phase Ib study and the evolution of the functionality of microbial communities with treatment

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Background: The role of gut microbial composition as a determinant of clinical outcomes has been well established in several cancers, including metastatic renal cell carcinoma (mRCC) (Routy et al Science 2018). A growing body of evidence suggests that examining the metabolic function of microbial communities may provide a more insightful understanding of these associations (Helmink et al Nature Medicine 2019). Herein, we aimed to examine the effect of nivolumab/ipilimumab with or without CBM588 on clinical outcomes and gut microbiome functionality. Methods: Treatment naïve mRCC pts with clear cell and/or sarcomatoid histology and IMDC intermediate/high risk disease were enrolled and randomized into receiving nivolumab/ipilimumab or nivolumab/ipilimumab with CBM588 in 1:2 fashion. Whole metagenome sequencing was performed on stool samples collected at baseline and week 12. Generated MetaPhlan 3.0 data was run through HUMAnN 3.0 to identify differentially expressed metabolic pathways between two timepoints in each arm and with respect to treatment response. Results: A total of 30 pts were enrolled and randomized, and 29 pts were eligible for analysis as one patient was excluded as tumor tissue next-generation sequencing revealed genomic alterations pathognomonic for sarcoma after initiation of protocol-based therapy. Median age of the participants was 66 years, 21 pts (72%) were male, 10 pts (34%) had sarcomatoid features, and 29 pts (45%) had prior nephrectomy. Objective response was achieved in 58% and 20% of the pts in nivolumab/ipilimumab/CBM-588 and nivolumab/ipilimumab arm, respectively. Significant changes in 40 metabolic pathways (37 with upregulation and 3 with downregulation) in nivolumab/ipilimumab arm and 52 metabolic pathways (49 with downregulation and 3 with upregulation) in nivolumab/ipilimumab with CBM588 arm were identified. In detail, dTDP-β-L-rhamnose biosynthesis, L-lysine biosynthesis II and superpathway of pyrimidine ribonucleosides degradation pathways were found upregulated while O-antigen building blocks biosynthesis (E. coli) pathway was found downregulated after treatment with nivolumab/ipilimumab and CBM588 (p = 0.001, p = 0.007, p = 0.037, p = 0.005 respectively). Heatmaps detailing the dynamics of metabolic pathway expressions in regard to response in each arm will be presented. Conclusions: We observed an increase in the activity of the pathways associated with butyrate consumption and a resultant decrease in glycolytic dependence. Further, suppression of the pathogenic E. coli function was observed, suggesting a role for CBM588 in protection from pathogenic species. Our findings provide mechanistic evidence for the effect of the addition of CBM588 to nivolumab/ipilimumab on gut microbiome function and resultant improvement in clinical outcomes in mRCC. Clinical trial information: NCT03829111.

Intestinal microbiome associated with development of grade 3/4 adverse in patients with metastatic renal cell carcinoma (mRCC) treated with nivolumab plus ipilimumab (N/I) and probiotic support: Results from a phase Ib study

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Background: Treatment with N/I with the addition of CBM588, a live bacterial product comprised primarily of Clostridium butyricum, improved PFS and RR versus N/I alone when used as first line treatment for patients with mRCC (Meza et al ASCO 2021). Increased abundance of certain bacterial species in the gut microbiome have been associated with the development of treatment related adverse events (TREAs) in lung cancer patients receiving immunotherapy (Chau et al BMC Cancer 2021). However, this association has not yet been delineated in the setting of mRCC. Here, we present results of an exploratory analysis assessing the differences in stool microbiome composition between patients who experienced grade (G) 3/4 TREAs and those who did not. Methods: Patients were randomized 2:1 to receive N/I with or without CBM588. Stool collection for bacteriomic profiling was planned at baseline and after 12 weeks of therapy for all randomized patients. Whole metagenome sequencing was performed using previously published methods (Dizman et al Cancer Med 2021) and differences in microbiome composition were measured based on the occurrence of G 3/4 TREAs. Results: 30 patients were enrolled and 29 included in the study. At the time of data cutoff (April 15, 2021) the median follow up was 12.2 months (95% confidence intervals [CI], 10.6-13.8). Grade 3/4 TRAEs were experienced in 52, 50, and 53% of patients in the overall cohort, control, and intervention arms, respectively (p = NS). Among the most common G 3/4 TRAEs, subjects experienced fatigue, diarrhea, and hyperglycemia. Patients with a complete set of stool samples were included for the microbiome analysis (n = 26). In patients who experienced G 3/4 TRAEs, a significantly greater baseline abundance of Escherichia coli, Klebsiella spp. and Blautia spp. (p = 0.02, 0.03, 0.05) were seen when compared to those not experiencing G 3/4 TRAEs. In contrast, Bacteroides intestinalis and B. thetaiotamicron, were observed in significantly higher abundances in baseline stool specimens of patients who did not experience G 3/4 TREAs (p = 0.03 for both). No significant differences were seen for any of these species at the 12-week timepoint. Conclusions: We are among the first to investigate the differences in baseline stool microbiome in mRCC patients experiencing G 3/4 TRAEs while receiving immunotherapy. Our results suggest that certain taxa of bacteria are predictors of the development of serious TRAEs. Larger cohorts are needed to corroborate these findings. Clinical trial information: NCT03829111.

First results of a randomized phase IB study comparing nivolumab/ipilimumab with or without CBM-588 in patients with metastatic renal cell carcinoma

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Background: Recent evidence suggests that the gut microbiome is a potent mediator of immune checkpoint inhibitor (ICI) activity in metastatic renal cell carcinoma (mRCC), with both specific bacterial species and cumulative microbial diversity driving response (Routy et al Science 2018; Salgia et al Eur Urol 2020). We examined whether the butyrate-producing bacterium Clostridium butyricum, the key constituent of CBM-588, could modulate the gut microbiome in patients (pts) with mRCC receiving nivolumab/ipilimumab (N/I) and secondarily improve clinical outcome. Methods: An open-label, randomized study was conducted, with key eligibility criteria including confirmed clear cell and/or sarcomatoid mRCC, intermediate/poor risk by IMDC criteria and no systemic therapy for metastatic disease. Patients were randomized 2:1 to receive either N/I+CBM-588 or N/I alone. N/I was dosed at 3 mg/kg and 1 mg/kg IV every 3 weeks for 12 weeks, followed by N at 480 mg IV every 4 weeks. CBM-588 was dosed orally at 80 mg bid. Stool was collected for bacteriomic profiling at baseline and 12 weeks. Metagenomic sequencing was employed using previously published methods (Dizman et al Cancer Med 2020). The primary endpoint of the study was change in Bifidobacterium spp. from baseline to week 12. Secondary endpoints included change in microbial diversity and clinical outcomes including response rate (RR) and progression-free survival (PFS). Results: 30 pts were randomized between April 2019 and Nov 2020; 1 pt was excluded after genomic sequencing clarified a diagnosis of sarcoma. Among 29 evaluable patients (21:8 M:F), median age was 66, 10 pts (34%) had sarcomatoid features and 24 pts (83%) were intermediate risk. Metagenomic sequencing of paired stool specimens showed an 8-fold increase in B. bifidum and a 6-fold increase in B. adolescentis in pts receiving N/I+CBM-588 from baseline to week 12. C. butyricum was detected only in pts receiving CBM-588. Pathogenic species (e.g., Escherichia. coli and Klebsiella spp.) were more prevalent in pts not receiving CBM-588. RR was significantly higher among pts receiving N/I+CBM-588 vs N/I alone (59% vs 11%; P = 0.024). Median PFS was also prolonged with the addition of CBM-588 to N/I (NR vs 11 weeks; P < 0.001). No significant difference in grade 3/4 toxicities were observed between study arms. Conclusions: This is the first randomized, prospective study to suggest enhancement of ICI response with a live bacterial product. The observed clinical impact is corroborated by biologic findings supporting gut modulation by CBM-588. Clinical trial information: NCT03829111.

Associations between plasma cytokine levels and gut microbiota composition in metastatic renal cell carcinoma (mRCC)

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Background: Plasma cytokines and the gut microbiome have been shown separately to influence the response to systemic therapy in mRCC. We sought associations between serum cytokines and gut microbial composition in patients (pts) with mRCC. Methods: Eligibility requirements included histologically proven mRCC and an intent to receive either vascular endothelial growth factor-tyrosine kinase inhibitor (VEGF-TKI) or immune checkpoint inhibitor (ICI). Blood samples were collected prior to treatment initiation and immunologic profiles were evaluated using a Human Cytokine 30-plex protein assay (Invitrogen). Stool was collected at baseline and shotgun metagenomic sequencing was performed to quantify gut microbial populations using previously published methods (Salgia et al Eur Urol 2020). Results: A total of 50 pts were studied (36:14 M:F) with a median age of 67 (range, 32-85). Twenty pts and 30 pts had subsequent initiation of VEGF-TKI and ICI therapy, respectively. Levels of Akkermansia spp were significantly higher in pts who were IL-6 low (P = 0.023). In contrast, pts who were IL-6 high had higher levels of enteric pathogens, including Salmonella spp and Enterococcus spp. Both Akkermansia spp and Bacteroides spp levels were higher in pts who were IL-8 low. Associations between cytokine levels, microbiome composition, and treatment response will be presented. Conclusions: Given studies suggesting the role of Akkermansia spp in enhancing ICI response (Routy et al Science 2018), our data provide a critical link between the gut microbiome and systemic immunomodulation.

First assessment of the stool mycobiome in patients (pts) with metastatic renal cell carcinoma (mRCC) receiving targeted therapy (TT) or immunotherapy (IO)

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Background: Previous studies have associated specific stool bacterial species with response to both targeted therapy and immunotherapy (Routy et al Science 2018; Dizman et al Cancer Med 2020). Abundant fungal elements also constitute the human microbiome (the so-called “mycobiome”); we explore whether these could be related to clinical benefit (CB) from TT. Methods: Pts from 2 simultaneously conducted studies were included in the analysis. Both studies enrolled patients with histologically confirmed RCC with metastatic disease; in one study, pts received standard of care (SOC) TT, while in the other pts received SOC IO. In both studies, stool was collected at baseline and at multiple timepoints thereafter. Whole metagenome sequencing was performed for fungal microbiome composition (TGen North, AZ). Linear discriminant analysis (LDA) effect size (LEfSe) was used for comparison of the gut mycobiome in patients who obtained clinical benefit (CB; complete response, partial response or stable disease > 6mos) versus no clinical benefit (NCB; progressive disease or stable disease ≤6mos) from TT or IO. Results: A total of 50 samples from 24 pts (19:5 M:F) were included in the analysis. The majority of pts (19; 79%) had clear cell histology. 15 pts received TT while 9 pts received IO. The fungal genera demonstrating the highest abundance was Saccharomyces with a median relative abundance of 86.9% (range, 11%-99%). LEfSe performed in different taxonomic levels revealed Malassezia globosa (LDA = 4.93; P = 0.038) and Alternaria infectoria (LDA 4.94; P = 0.018) as gut mycobiome components associated with NCB, and order Russulales associated with CB from TT (LDA = 4.93; P = 0.018). In contrast, no association was identified between mycobiome profile and CB in the IO-treated group. The presence of several pathogenic fungi such as Candida albicans and Aspergillus fumigatus was noted in a minority of pts and did not have any bearing on clinical outcome. In pts with serial samples, a trend towards decreasing Saccharomyces spp. (the most abundant species) and increasing fungal diversity was noted. Conclusions: Our study is the first to highlight potential associations between the mycobiome and CB with TT. Our finding of Malassezia spp resulting in lack of CB with TT bolsters findings from Aykut et al (Nature 2019), implicating the same genera in progression of pancreatic cancer. Confirmation of these findings in larger series is underway.

Randomized prospective trial assessing Bifidobacterium-containing probiotic supplementation in metastatic renal cell carcinoma (mRCC) patients receiving vascular endothelial growth factor-tyrosine kinase inhibitors (VEGF-TKIs)

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Background: Studies suggest a link between the gut microbiome and mRCC outcomes, including evidence that mRCC patients (pts) possess a lower abundance of Bifidobacterium spp compared to healthy adults (Pal et al Clin Cancer Res 2015). The aim of this study was to assess if Bifidobacterium-containing probiotics could modulate the gut microbiome and impact rates of clinical benefit (CB) from VEGF-TKIs. Methods: Pts initiating VEGF-TKI therapy for mRCC were randomized to probiotic supplemented (PSu) or probiotic restricted (PRe) treatment arms. Pts in the PSu arm consumed two 4 oz servings of Activia daily. Stool samples were collected prior to therapy and at wks 2, 3, 4 and 12. Gut microbiota composition was assessed using whole genome shotgun metagenomic sequencing (Zhu et al Microbiome 2018). The primary endpoint was change in Bifidobacterium spp with therapy. Microbiome composition was compared across pts with CB (complete/partial response or stable disease) versus no CB (NCB). Results: In total, 20 pts were enrolled. The most frequent VEGF-TKIs were cabozantinib (45%), sunitinib (25%) and lenvatinib (25%). Median progression-free survival (PFS) was 6.5 months (95%CI 0.3-12.9) and CB rate was 75%. Bifidobacterium animalis, the active ingredient of Activia, reached detectable levels in all pts in the PSu arm, but was only detectable in one pt in the PRe arm. CB rate was not significantly different in PSu vs PRe arms (70% vs 80%, p > 0.05), and there was no difference in PFS. LDA effect size (LEfSe) analysis of MetaPhIAn2 data captured 25 enriched species demonstrating an LDA score > 3 in either CB or NCB. Of those with high LDA scores, Barnesiella intesitinihominis and Akkermansia municiphila were the most significant members (p = 7.4 x 10−6 and p = 5.6 10−3, respectively). While 92% of B. intestinihominis positive pts obtained a CB, only 50% of B. intestinihominis negative pts obtained CB (p = 0.036). Conclusions: This is the first prospective randomized study demonstrating modulation of the gut microbiome with probiotics in mRCC. While microbiome modulation by probiotics did not increase CB rates as intended, consecutive stool specimens allowed us to identify an association between B. intesitinihominis, A. municiphila and CB with VEGF-TKIs. In addition to the previously documented association between A. municiphila and immunotherapy outcome (Routy et al. Science 2018), this species may predict activity with VEGF-TKIs. Clinical trial information: NCT02944617 .