Sterile faecal filtrate transplantation alters phage-microbe dynamics in individuals with metabolic syndrome: a double blind, randomised, placebo-controlled clinical trial assessing efficacy and safety

Objective Bacteriophages (phages) are viruses of bacteria and have been shown to shape microbial communities. Previous studies have shown that altering the microbiota through faecal microbiota transplantation (FMT) can improve insulin resistance in individuals with metabolic syndrome (MetSyn). Interestingly, similar effects were observed in diet-induced obese mice after a faecal virome transplantation (FVT), raising the question whether phages of a healthy donor can improve glucose metabolism in individuals with MetSyn as well. Design We performed a double-blind, randomised, placebo-controlled pilot study in which 24 individuals with MetSyn were randomised to receive a sterile faecal filtrate transplantation (FFT) from a lean healthy donor or a placebo. From baseline up to 28 days, we assessed safety, effects on glucose metabolism, and longitudinal changes within the bacteriome and phageome. Results The FFT was well-tolerated and safe and glucose variability (time between 3.9-10 mmol/L glucose) improved in the week following the FFT. Glucose excursions during oral glucose tolerance tests were comparable in both the FFT and placebo group after 28 days. The phage virion composition was significantly altered two days after FFT as compared to placebo. Moreover, we found that FFT induced more virulent phage-microbe interactions within the first two days after administration, while these interactions appeared more temperate in the placebo group. Conclusion We provide evidence that gut phages from a healthy donor can be safely administered to transiently alter the gut microbiota of recipients, thereby providing a critical basis for follow-up studies. Trial registration number Dutch Trial Registry: NL8289 ### Competing Interest Statement MN is founder and scientific advisors of Caelus Health, however none of this bears any relevance to the content of the current paper. KW, PAdJ, TPMS, IA, EMK, and HH report no conflict of interest. ### Clinical Trial NL8289 ### Funding Statement KW was supported by a Novo Nordisk Foundation CAMIT grant 2018 (28232) to MN and a Diabetes II Breakthrough grant (459001008) to HH. PAdJ en TPMS were supported by DDRF Senior fellowship (2019.82.004) to HH. IA was supported through a Le Ducq consortium grant (17CVD01) to MN. MN was supported by a personal ZONMW-VICI grant 2020 (09150182010020) and a Le Ducq consortium grant (17CVD01). HH was supported by a Senior Fellowship of the Dutch Diabetes Research Foundation (2019.82.004). The funders had no role in the study design, the collection, analysis, and interpretation of data, the writing of the report, and the decision to submit the article for publication. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Medical Research Ethics Committee of the Academic Medical Center Amsterdam gave ethical approval for this work I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The sequencing data generated in this study have been deposited in the European Nucleotide Archive database under accession code: PRJEB60691. The data are freely available without restriction.