Faculty Bibliography

Background/Purpose : The trillions of microorganisms (microbiota) found within the human gut play a critical role in shaping the immune system, yet these complex microbial communities are also highly sensitive to numerous environmental factors. While much of the focus to date has been on dietary intake, emerging data has begun to suggest that the use of pharmaceutical drugs, even those that are not considered to be antibiotics, can alter the human gut microbiota with unknown consequences for treatment outcomes. Here, we examine the effect of methotrexate (MTX), which is first-line therapy for rheumatoid arthritis (RA), on microbiota composition and physiology as well as downstream consequences on the host ' s immune system. Methods : To examine the effect of MTX on human gut microbiota composition in vivo , gnotobiotic mice were colonized with microbiota from either healthy or RA patient donors and treated with oral MTX at varying doses. We performed high-throughput sequencing of the 16S rRNA gene to examine changes in taxonomic composition. We looked at the effects of varying the route of administration or co-administration with folic acid. To determine the direct effects of MTX on bacterial growth, we treated monocultures of 42 different human gut isolates with MTX and monitored growth using optical density. To identify MTX-induced transcriptional changes, we performed RNA-Seq on 4 isolates treated with MTX. To determine the effects of MTX on bacterial taxonomy in vivo , fecal samples from RA patients (100% fulfilling ACR criteria) starting MTX were profiled longitudinally using 16S sequencing. To determine if MTX-induced shifts reduce the inflammatory potential of the RA microbiome, microbiota from RA patient donors either before or after MTX initiation were transplanted into germ-free mice. These mice were challenged with an inflammatory trigger with dextran-sodium sulfate (DSS), and immune profiling was done to assess inflammation. Results : MTX altered community composition in vivo in humanized mice, leading to reduced Bacteroidetes and increased Firmicutes. Varying the route of drug administration or co-administration with folic acid produced similar, reproducible shifts. MTX directly altered growth of many human gut isolates. At the phylum level, Bacteroidetes tended to be more sensitive than Firmicutes, recapitulating the trends observed in gnotobiotic mice in vivo . RNA-Seq revealed that MTX alters transcriptional pathways involved in purine and pyrimidine metabolism. Furthermore, longitudinal analyses of the in vivo gut microbiotas of RA patients showed that MTX-induced shifts in bacterial relative abundance are associated with improved drug response. Transplant experiments revealed that mice harboring MTXaltered microbiota exhibited a reduced Th17 and Th1 response to DSS compared to mice harboring pre-treatment microbiota, suggesting that MTX alters the inflammatory potential of the RA patient microbiome. Conclusion : Together, these results suggest that the mechanism-of-action of non-antibiotic drugs may be due in part to off-target effects on the gut microbiota, while providing a critical first step towards explaining long-standing differences in drug response between patients

Background/Purpose : Early treatment initiation in rheumatoid arthritis (RA) is fundamental to avoid chronic joint destruction and disability. Despite remarkable advances in RA therapeutics, oral methotrexate (MTX) remains the anchor drug and mainstay of treatment worldwide. However, MTX bioavailability has a wide inter-individual variability and >50% of patients with moderate or severe RA show no or suboptimal improvement in their symptoms in response to MTX. The reasons for these disparities in treatment response remain unclear. Prior studies have shown that the biotransformation of MTX is altered in germ-free and microbiome-depleted mice, prompting us to hypothesize that inter-individual differences in the human gut microbiome could impact drug bioavailability and thus clinical efficacy. We sought to determine differences in the microbiome of drug-naive, new onset RA (NORA) patients that could predict response to MTX therapy. Methods : We enrolled 27 drug-naive, NORA patients priori to MTX initiation (test cohort), and classified them as either MTX-responders (MTX-R; 39% of the cohort) or non-responders (MTX-NR; 61%) based on a stringent definition of clinical response (delta improvement of DAS28 >1.8 by month 4). We performed 16S rRNA gene and Shotgun Metagenomic sequencing on the baseline gut microbiomes of these NORA patients and confirmed the results in an independent validation cohort (n=31). NMR and LC-MS were performed in ex vivo incubations to measure the capacity of each NORA microbiome to metabolize MTX. Results : Our analysis revealed significant associations between the abundance of gut bacterial taxa and future MTX response. Patients that responded to therapy had significantly lower microbial diversity (p< 0.05). A significant difference in overall gut microbial community structure was also observed between groups (Bray-Curtis distance; PERMANOVA < 0.05). At the class level, we observed statistically higher abundance of Clostridia and lower abundance of Bacteroidia in MTX-NR (p< 0.05; q< 0.2). Furthermore, the baseline metagenome separated most MTX-R from MTX-NR (PCoA; PERMANOVA p< 0.05). We identified 8 microbial modules and 23 pathways, whose abundance significantly differed between groups (p< 0.05, q< 0.2), including genes related with purine and MTX metabolism, indicating a major difference in metabolic and biosynthetic potential between the microbiome of MTX-R and MTX-NR patients. Machine learning techniques were applied to this metagenomic data, resulting in a robust model based on bacterial gene abundance that accurately predicted response to MTX in an independent cohort. Finally, MTX available levels remaining after ex vivo incubation with distal gut samples from pre-treatment RA patients significantly correlated with the magnitude of future clinical response, suggesting a direct effect of the gut microbiome on MTX bioavailability and response to therapy. Conclusion : Together, these results provide the first step towards predicting response to oral MTX in NORA patients and support the utility of the gut microbiome as a prognostic tool and perhaps even as a target for manipulation in the treatment of rheumatic and autoimmune disease

PURPOSE OF REVIEW/OBJECTIVE:The therapeutic response to biologic agents in psoriasis is significantly higher than observed in psoriatic arthritis (PsA). In this review, specific actions to improve treatment outcomes in PsA are discussed. RECENT FINDINGS/RESULTS:Increased understanding of disease pathogenesis derived from improved preclinical models and advances in cell-based and molecular technologies provide new tools to identify therapeutic targets. In addition to the important contributions of metabolic comorbidities, chronic pain and the lack of a diagnostic biomarker signal the need for new strategies to improve outcomes. Potential strategies include the following: (1) discover a novel pathway or cellular subset, (2) apply stratification biomarkers to individualize therapy, (3) preclinical intervention, (4) combination therapy, (5) lifestyle modification, (6) address chronic pain and fatigue, and (7) multidisciplinary care. The future holds great promise for enhanced treatment responses in PsA based on improved understanding of individual variation in disease pathophysiology coupled with comprehensive and integrated treatment programs.

Gut-dwelling Prevotella copri (P. copri), the most prevalent Prevotella species in the human gut, have been associated with diet and disease. However, our understanding of their diversity and function remains rudimentary because studies have been limited to 16S and metagenomic surveys and experiments using a single type strain. Here, we describe the genomic diversity of 83 P. copri isolates from 11 human donors. We demonstrate that genomically distinct isolates, which can be categorized into different P. copri complex clades, utilize defined sets of polysaccharides. These differences are exemplified by variations in susC genes involved in polysaccharide transport as well as polysaccharide utilization loci (PULs) that were predicted in part from genomic and metagenomic data. Functional validation of these PULs showed that P. copri isolates utilize distinct sets of polysaccharides from dietary plant, but not animal, sources. These findings reveal both genomic and functional differences in polysaccharide utilization across human intestinal P. copri strains.

Background: IL-17F shares structural homology and pro-inflammatory function with IL-17A. Preclinical and early clinical data support neutralisation of IL-17F, in addition to IL-17A, as a novel targeting approach in psoriatic disease.
Objective(s): The objective of this Phase 2b study (NCT02969525) was to assess the dose response, long-term efficacy and safety of bimekizumab (BKZ), a mAb that potently and selectively neutralises IL-17A and IL-17F, over 48 weeks in patients (pts) with active PsA.
Method(s): 206 pts with active PsA, >=3/76 swollen joint count, >=3/78 tender joint count and CASPAR score >=3, were randomised (1:1:1:1:1) to receive subcutaneous BKZ 16mg, 160mg, 160mg with 320mg loading dose (160mg [LD]), 320mg or placebo (PBO) Q4W, for 12 weeks (double-blind period). After Week 12, pts receiving PBO or BKZ 16mg were re-randomised (1:1) to BKZ 160mg or 320mg; all other pts continued on their initial dose (dose-blind period). The primary endpoint was ACR50 response at Week 12. [TABLE PRESENTED HERE]Results: 203/206 and 189/206 pts completed the double- A nd dose-blind periods, respectively. Overall, demographics and baseline disease characteristics were balanced across groups. 19% of pts had prior exposure to TNF inhibitors (TNFi). There was a statistically significant (p<0.05) dose-response at Week 12 for ACR50 response rates. At Week 12, significantly more pts receiving BKZ versus PBO achieved ACR50 (primary endpoint: 16-160mg [LD] doses), ACR20 and PASI90 (in those pts with baseline body surface area >=3%; 160-320mg doses) (table). ACR20/50/70, PASI75/90/100, MDA and resolution of enthesitis response rates increased between Week 12 and Week 24 in those continuing on their initial BKZ dose; Week 24 responses were maintained through the study; responses were similar across the three highest dose groups at Week 48 (PASI100 analyses were post hoc). Rapid improvements were observed across all response criteria in pts re-allocated to BKZ 160 or 320mg (table). BKZ-treated pts naive to TNFi achieved ACR20/50 and PASI90/100 at comparable rates to the overall population at Week 12 and 48. There was no apparent relationship between dose and TEAEs. Serious AEs were reported by 9/206 (4.4%) pts up to Week 48 (8/206 [3.9%] patients were receiving BKZ). The most common TEAE up to Week 48 was nasopharyngitis 25/206 [12.1%]). Oral candidiasis was reported at Week 48 by 10/206 (4.9%) pts (all cases during BKZ treatment). No deaths, or cases of IBD or MACE were reported.
Conclusion(s): Dual neutralisation of IL-17A and IL-17F with BKZ provided substantial improvements in both musculoskeletal and skin outcomes; response rates increased after Week 12 (primary analysis) and were sustained from Week 24 to 48, with a safety profile consistent with previous BKZ studies. These data provide further support that neutralising IL-17F in addition to IL-17A with BKZ is a promising therapeutic approach in pts with active PsA

Psoriasis is one of the most common chronic inflammatory skin diseases, affecting 3% of the world's population, and approximately one-third of patients with psoriasis will eventually transition to having psoriatic arthritis (PsA). The evolution from cutaneous to synovio-entheseal inflammation in these patients presents an opportunity to investigate the critical events linked to arthritis development. The events responsible for progression to PsA are currently unclear. Genetic and clinical-demographic risk factors (most notably familial aggregation and psoriasis sub-phenotypes) provide relevant insights into the variables that promote transition. The specific underlying molecular and cellular mechanisms, however, remain poorly defined. Intriguingly, although targeting the IL-23-IL-17 axis substantially improves psoriasis outcomes, this strategy is not more effective than TNF inhibitors in improving musculoskeletal symptoms in PsA. Major unmet needs in the field of PsA include defining those patients with psoriasis at increased risk of developing arthritis, improving our understanding of the natural history of disease and characterizing the immune, environmental and molecular subclinical events preceding PsA onset. Improving our knowledge of this transition is essential for designing clinical trials with treatments that can delay, attenuate or even prevent the development of PsA in patients with psoriasis.