FMT capsules (MBK-01) compared to fidaxomicin for the treatment of primary and recurrent Clostridioides difficile infection

FMT capsules (MBK-01) compared to fidaxomicin for the treatment of primary and recurrent Clostridioides difficile infection | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article FMT capsules (MBK-01) compared to fidaxomicin for the treatment of primary and recurrent Clostridioides difficile infection Javier Cobo, Elena Bereciartua, Javier Crespo, Esther Saez de Adana, and 15 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7712660/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objectives: Clostridioides difficile infection (ICD) is a major cause of nosocomial diarrhea, with high recurrence rates following standard antibiotic treatments. Fecal microbiota transplantation (FMT) has emerged as a promising therapy for recurrent CDI (rCDI), though its efficacy in primary CDI remains under investigation. This study evaluates the safety and efficacy of MBK-01, a novel oral FMT capsule, compared to fidaxomicin, the current standard of care, in both primary and rCDI. Methods : In this randomized, open-label, multicenter phase III trial, patients with primary or rCDI were randomized to receive MBK01 (with or without a short period of prior antibiotic treatment) or fidaxomicin (200 mg/12h for 10 days). The primary endpoint was absence of recurrence at 8 weeks post-treatment. Secondary endpoints included time to recurrence and adverse events at 6 months. The study is registered with ClinicalTrials.gov (NCT05201079). Results : 92 patients with CDI (45 in the MBK-01 group and 47 in the fidaxomicin group) were enrolled across 21 centers in Spain. MBK-01 demonstrated non-inferiority to fidaxomicin, with recurrence rate differences of 11.69% in the overall population (p=0.013), -1.06% in primary CDI cases (p=0.013), 42.79% in recurrent episodes (p=0.003), and 20% in participants without prior antibiotic treatment (p=0.008). Additionally, in rCDI, MBK-01 showed superiority compared to fidaxomicin (p=0.014). Notably, MBK-01 achieved 100% effectiveness in participants without antibiotic pre-treatment, versus 80% for fidaxomicin. The median time to recurrence in the overall population was similar. MBK-01 was associated with fewer treatment-related adverse events. Conclusions : MBK-01 represents a safe, effective, and less antibiotic-dependent option for CDI, particularly in recurrent cases. Its efficacy in primary CDI and favorable safety profile suggests that MBK-01 could serve as first-line therapy, potentially reducing antibiotic reliance and improving outcomes. These findings support broader use of microbiota-based therapies in the management of CDI. Clinical trial number: NCT05201079 Figures Figure 1 Figure 2 Figure 3 Introduction Clostridiodes difficile infection (CDI) is the main cause of nosocomial diarrhea in developed countries, representing up to 25% of cases of antibiotic-associated diarrhea ( 1 ). CDI symptoms usually range from mild to moderate diarrhea but can escalate to pseudomembranous colitis, toxic megacolon, septic shock, and even death in severe cases ( 2 ). CDI constitutes an important economic burden for Western healthcare systems ( 3 ). Its reported incidence currently remains elevated, partially by the inappropriate use of the antibiotics and the emergence of more virulent CD strains, but also by the advancements in diagnostic methods ( 4 ). Antibiotics constitute the first line of treatment against CDI. Fidaxomicin has demonstrated comparable efficacy to vancomycin with lower rates of recurrence at 28 days post-treatment ( 5 , 6 ). Consequently, both the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA) recommend the use of fidaxomicin for primary cases and the first recurrence of CDI, while vancomycin is considered an alternative treatment ( 7 ). The European Society of Clinical Microbiology and Infectious Diseases similarly advises this approach ( 8 ). A peculiarity of CDI is its tendency to recur after successful treatment, which occurs in up to 20% of cases 2 . Fecal microbiota transplantation (FMT) has emerged as a therapeutic option in cases of recurrent CDI (rCDI), demonstrating high efficacy and safety, also in patients with different comorbidities ( 9 – 11 ). FMT has historically been compared to vancomycin in most studies and only in one prior study has it been directly compared to fidaxomicin for recurrent episodes of CDI ( 12 ). FMT has been also proposed as a potential treatment for primary CDI ( 13 – 16 ). However, some safety problems were reported in FMT associated to a poor fecal donor screening ( 17 , 18 ). Thus, the FDA recommends FMT only in those patients with multiple recurrences of CDI who have failed antibiotic treatment and after an appropriate screening of both donor and donor fecal specimen. Effectively bringing FMT to patients requires much more than just the existence of a clinically effective procedure ( 19 ). A centralized and commercialized FMT product could reduce variability, ensure high-quality standards, and improve patients' access. In a meta-analysis involving 38 randomized clinical trials and 8,102 participants, the superiority of FMT in preventing rCDI was demonstrated, showing only mild gastrointestinal adverse events ( 20 ). Thus, the present phase III, prospective follow-up clinical trial was conducted to evaluate the efficacy and safety of the investigational oral medicinal FMT product (MBK-01 capsules) compared to fidaxomicin in patients with both recurrent and primary episodes of CDI. Methods Trial design and Participants This randomized, open-label, controlled multicenter phase III trial was performed from July 2021 through November 2023 in accordance with the national (Royal Decree 1090/2015) and the European regulation (Union Directive 2001/20/EC), following all the ethical principles of the Declaration of Helsinki. Spanish regulatory authorities and the Ethics Committee of Euskadi approved the trial. Participants included adults (≥ 18 years) with confirmed CDI, either primary or recurrent), experiencing an episode of diarrhea (≥ 3 stools/24 hours) and testing positive for CD toxin A and/or B in fecal samples by a direct toxin detection test or by the PCR technique for the detection of toxin/s producing genes. Patients with previous FMT were excluded. Detailed eligibility criteria are provided in the Supplementary Appendix . Written informed consent was obtained from all participants. Randomization and Interventions Two treatment groups were included in the study. Participants who met all inclusion criteria and none of the exclusion criteria were randomly assigned in a 1:1 ratio to the experimental or control arm. Before randomization, vancomycin (3–5 days) or fidaxomicin (< 24h) was permitted. In instances where these treatments were employed or if the patient was undergoing systemic treatment with other antibiotics, a 24-hour washout period was implemented before commencing the trial treatment. Participants assigned to the control group were treated with fidaxomicin at a dosage of 200 mg/12 hours for 10 days. Participants in the experimental FMT group were treated with MBK-01, which consisted of 4 capsules of 250 mg/capsule (≥ 2x10 11 microorganisms/g) administered orally in a single dose on an empty stomach. MBK-01 is an investigational medicinal product containing lyophilized heterologous intestinal microbiota (Full Spectrum & Purified Intestinal Microbiota) from healthy donors. In this study, MBK-01 was derived from seven different donors; however, each patient received FMT from a single donor, as each donation corresponded to a specific batch of MBK-01. The rationale for the dose was calculated to be above the minimum dose that has been proven to be effective with lyophilized FMT capsules ( 21 ). Details of the inclusion and exclusion criteria of the donors and stool samples are provided in the Supplementary Appendix . After baseline assessment, when treatment was first administered, participants were followed up for a total of 6 months. In case of a participant withdrawn, the subject was monitored for ≥ 30 days after treatment initiation. At baseline and subsequent visits, information of potential trial outcomes, adverse events and concomitant therapies were collected. Efficacy and Safety endpoints The main objective was to evaluate the efficacy of MBK-01 compared to fidaxomicin at 8 weeks after initiation of the treatment. The primary efficacy outcome was the absence of recurrence of CDI. Recurrence means the reappearance of clinical manifestations of a new episode of CDI within 8 weeks after the onset of a previous episode that was resolved ( 22 ). Moreover, the time to recurrence was also determined. The secondary objective involved evaluating the safety of MBK-01 at 6 months after the treatment, including treatment-related Adverse Events (AEs), and serious AEs (SAEs) in relation to the treatment. AEs were classified using MedDRA version 26.1. Statistical analysis The study was initially designed to evaluate the superiority of MBK-01 compared to fidaxomicin in recurrent CDI cases. However, to expedite recruitment, the study was later expanded to include primary CDI cases as well. This adjustment led to the consideration of a non-inferiority analysis for the overall mixed population (primary and recurrent CDI) and a subsequent post-hoc subgroup analysis. This approach provided additional insights into the potential efficacy of MBK-01 as a first-line treatment. The efficacy analysis was planned to be carried out with the intention to treat (ITT) population, defined as all randomized participants, and for proportions of recurrence in the ITT modified (participants with available data at 8 weeks after finishing treatment and resolving the on-course episode). The difference in recurrence rates between treatments was analyzed by means of a one-sided A/B test (difference between proportions of independent samples). For the non-inferiority tests, the efficacy of the two treatments was compared as a difference of recurrence rates. The non-inferiority margin of -0.10 was incorporated into the null hypothesis as an acceptable maximum difference in non-recurrence proportions between the treatments. Based on the known recurrence rate of approximately 12% found in clinical trials we selected a non-inferiority margin of 10% ( 6 ). The primary focus of the analysis remained on demonstrating non-inferiority in the mixed population, with subgroup analyses conducted to assess differences between primary and recurrent CDI cases. Although the study initially prioritized the superiority analysis for recurrent cases, this was later reframed as a post hoc exploratory analysis to provide additional insights and to guide future hypothesis generation. The statistical difference between proportions in the null hypothesis for the superiority analysis was set to 0, and a one-sided A/B test was carried out. Subgroup analyses of the probability of recurrence considered participants with primary or recurrent episodes and participants with no antibiotic pre-treatment. Survival analysis was performed, examining time to recurrence measured in weeks, with the treatment group acting as the independent variable. Kaplan-Meier curves were employed to estimate survival probabilities, while the log-rank test was utilized to compare between treatment groups. AEs were analyzed descriptively, focusing on frequencies and percentages observed throughout the study period. This analysis was conducted on the Safety Population (SP). The significance level for all the inferential analyses presented was α = 0.0294. The analyses were programmed in R statistical software (version 4.2.3, R Core Team, 2023), and the RStudio interface (version 2023.09.0). Results Recruitment and baseline characteristics of the participants Between October 2021 and November 2023, a total of 92 patients were enrolled among 21 centers in Spain. The ITT population consisted of 92 participants, of whom 45 were randomly assigned to the MBK-01 group and 47 to the fidaxomicin group. For the efficacy analysis, the modified ITT (mITT) population was defined as all ITT patients with available data on recurrence status at visit 4 or later. This population included 77 evaluable participants (37 in the MBK-01 group and 40 in the fidaxomicin group). The reasons why some participants were considered non-evaluable (8 in the MBK-01 group and 7 in the fidaxomicin group) are detailed in Fig. 1 . The per-protocol (PP) population consisted of 48 participants. In the MBK-01 group, 23 participants completed the study, while 22 did not. In the fidaxomicin group, 25 participants completed the study, whereas 22 did not. The reasons for protocol deviations in these subjects are specified in Fig. 1 . For non-evaluable participants, reasons for exclusion included factors such as prohibited medication use or adverse events. However, not all participants with these factors were excluded. Those who had medication prohibited by protocol but could still complete the required follow-up were included in the analysis, as their data remained valid for efficacy assessment. In contrast, participants whose protocol deviations could interfere with treatment evaluation, either by affecting the drug’s mechanism of action or leading to early discontinuation, were excluded. This distinction has been clarified in Fig. 1 . Safety analysis (SP) included 92 participants (45 in the MBK-01 and 47 in the fidaxomicin group). This approach ensured that safety outcomes were assessed in all participants who received at least one dose of the assigned treatment according to the study guidelines. Baseline demographic and clinical characteristics were similar between groups, as shown in Table 1. Efficacy evaluation Recurrence-free survival at 8 weeks post-treatment was assessed in the modified intention-to-treat (mITT) population using both a non-inferiority and superiority approach. MBK-01 demonstrated non-inferiority to fidaxomicin in the general population for CDI treatment. At 8 weeks post-treatment, recurrence was observed in 10.81% (4/37) of MBK-01 treated patients, compared to 22.50% (9/40) in the fidaxomicin group. The absolute risk difference was 11.69% (95% CI: − 7.7 to 30.7; p = 0.013), confirming non-inferiority within the predefined margin of − 10%. However, superiority was not established. The number needed to treat (NNT) to prevent one recurrence was 8.55. These results are summarized in Table 2 and Fig. 2 A. In patients with primary CDI episodes, recurrence rates were similar between groups: 4.76% (1/21) in the MBK-01 group and 3.70% (1/27) in the fidaxomicin group, with an absolute risk difference of − 1.06% (95% CI: − 26.6 to 24.7). This confirms that MBK-01 was as effective as fidaxomicin in these cases (Table 2, Fig. 2 B) For recurrent CDI episodes, MBK-01 was significantly more effective. Recurrence occurred in 18.75% (3/16) of patients treated with MBK-01 compared to 61.54% (8/13) of those receiving fidaxomicin, with an absolute risk difference of 42.79% (95% CI: 2.6 to 71.8; p = 0.003). Both non-inferiority and superiority were demonstrated. The odds ratio (OR) was 6.93, indicating that for each recurrence in the MBK-01 group, nearly seven recurrences occurred in the fidaxomicin group (Table 2, Fig. 2 C). Among patients without pretreatment with vancomycin or fidaxomicin, MBK-01 was also more effective, reducing recurrences by 20.00% compared to fidaxomicin (0% [0/17] vs. 20.00% [3/15]). The percentage risk difference was 20.00% (95% CI: − 4.8 to 48.6). Both non-inferiority and superiority were achieved (Table 2, Fig. 2 D). When analyzing the overall time to recurrence, including all participants regardless of whether they experienced a recurrence, a trend was observed toward earlier and more frequent recurrences in the fidaxomicin group (Fig. 3 ). Among participants who experienced a recurrence, the mean time to recurrence was 31 days (SD = 12 days) for fidaxomicin and 25 days (SD = 25 days) for MBK-01. However, the greater variability in MBK-01 group prevents concluding due to the low number of recurrences observed. These findings are consistent with those seen in clinical practice and with other studies evaluating these treatments ( 6 ). Safety Outcomes and treatment-related Adverse Events The safety profile of MBK-01 was assessed throughout the study, focusing on treatment-emergent adverse events (AEs), serious adverse events (SAEs), and adverse events of special interest (AESIs). MBK-01, as a novel therapeutic agent, was generally well tolerated, with most reported adverse events being mild to moderate in severity. Among participants receiving MBK-01, the overall incidence of AEs was 46.35%. The most frequently reported events included diarrhea, increased C-reactive protein levels, vomiting and abdominal pain. AESIs were reported with an incidence of 50.39% for MBK-01, with the most common events being increased C-reactive protein levels, vomiting and abdominal pain (4 events each). Diarrhea was the most prevalent AESI, reported in 26 cases. A total of 11 SAEs were documented in the MBK-01 group, representing 68.75% of all reported SAEs. Although none of these events were deemed directly related to MBK-01, a detailed list is provided in supplementary materials (Table 3). Importantly, no treatment-related deaths were reported. Regarding adverse events probably or definitely related to treatment, diarrhea was the only event observed in the MBK-01 group, affecting one participant. In the fidaxomicin-treated group, one subject experienced treatment-related diarrhea, while another participant experienced both flatulence and fatigue potentially related to the treatment. Furthermore, no clinically significant changes in laboratory parameters, vital signs, or electrocardiogram readings were observed that could be attributed to MBK-01. Discussion This phase III trial demonstrated that MBK-01 was non-inferior to fidaxomicin for the treatment of Clostridioides difficile infection (CDI) and superior in recurrent cases (rCDI). The results support MBK-01 as a potential therapeutic alternative, with the added advantage of avoiding antibiotic exposure. While recurrence free survival rates were comparable in primary CDI, MBK-01 showed a significantly lower recurrence rate in rCDI, suggesting that early microbiota-based intervention could enhance microbiota restoration and reduce recurrence risk, particularly in rCDI cases ( 23 ). However, concerns remain regarding the safety of FMT, and further studies are needed to determine whether the absence of antibiotic exposure with MBK-01 translates into additional clinical benefits beyond recurrence prevention. To date, two microbiota-based therapies, SER-109 and RBX2660, have received regulatory approval in the USA for the prevention of CDI recurrence after standard antibiotic treatment. However, neither are indicated as a first-line treatment of the infection itself ( 24 , 25 ). In addition, another investigational product based on Microbiota (VE3033) is being developed as a preventive measure following treatment with antibiotics ( 31 ). In contrast, MBK-01, as demonstrated in this study, not only shows promise as an effective first-line treatment for primary CDI but also demonstrates superior efficacy in rCDI cases compared to fidaxomicin. Furthermore, MBK-01 was effective both with a very short course of vancomycin or fidaxomicin and even without the use of these antibiotics. This positions MBK-01 as a unique and innovative therapeutic option, addressing both the immediate and long-term needs of CDI management. Fidaxomicin and vancomycin are commonly used therapeutic alternatives for the treatment of CDI, especially in primary episodes. However, the growing concern over antibiotic resistance, particularly resistance to vancomycin and fidaxomicin, along with the rise of certain hypervirulent and multidrug-resistant (MDR) CD ribotypes, such as ribotypes 027 and 176, poses a significant challenge in CDI management ( 26 , 27 ). A microbiota-based oral therapy has been shown to reduce antimicrobial resistance in rCDI patients compared to placebo (p = 0.003) ( 28 ). Since this study confirms the non-inferiority of MBK-01 to fidaxomicin, it is essential to emphasize the indirect benefits of reducing antibiotic use. In our study, recurrence rates were relatively low compared to some previous trials, which reported rates of 29% for FMT, 67% for fidaxomicin, and 81% for vancomycin in rCDI patients ( 29 ). Earlier studies reported recurrence rates of 24.0% and 35.5% for vancomycin, while fidaxomicin-treated patients had a recurrence rate ranging from 16.3% to 26.4% for both primary and recurrent episodes ( 30 – 32 ). In a randomized phase 2 trial involving patients with primary or recurrent CDI, recurrence rates at week 8 were 13.8% with high-dose oral VE303 (a defined bacterial consortium), 37% with a low-dose, and 45.5% with placebo ( 33 ). However, a meta-analysis reported a 22% recurrence rate after the first FMT ( 34 ). In contrast, MBK-01-treated patients in this study had a recurrence rate of 18.75%, significantly lower than fidaxomicin (61.54%) and below several previously published rates ( 21 , 35 ). This suggests that FMT, and by extension MBK-01, offers a therapeutic alternative with superior efficacy compared to other standard antibiotics ( 36 , 37 ). One of the most innovative aspects of this trial was the evaluation of FMT in primary CDI episodes. We reported non-inferior efficacy of MBK-01 compared to fidaxomicin in this subgroup, aligning with a prospective randomized trial where FMT by enema showed no statistical differences with metronidazole (56% vs 45% full primary response, p = 1.00) in primary CDI ( 14 ). Moreover, 78% of the FMT-treated patients achieved an overall treatment response compared to 45% for metronidazole (p = 0.20) ( 14 ). A recent randomized controlled trial (EarlyFMT) showed significantly higher CDI resolution rates at 8 weeks with FMT (90%) compared to placebo (33%; p = 0.0003), leading to early trial termination for ethical reasons ( 38 ). In another retrospective study, 59 patients with primary CDI were treated with two FMT infusions after pre-treatment with vancomycin and/or metronidazole for 10–14 days. Four to eight weeks post-FMT, there was a significant reduction in abdominal pain (p < 0.05), diarrhea, and bleeding (both p < 0.01). FMT demonstrated high efficacy, low recurrences, and no adverse events ( 15 ). However, as patients received 10–14 days of antibiotic pre-treatment, FMT was primarily employed as a "recurrence prevention" strategy rather than as a standalone treatment for CDI. This context should be considered when interpreting the results. Furthermore, it is not surprising that FMT shows greater effectiveness in primary episodes compared to secondary or tertiary episodes. A retrospective trial involving 96 patients showed that FMT following 10-day antibiotic pre-treatment was more effective in preventing recurrences in primary (5.25%) compared to secondary (15.15%) or tertiary (27.3%) severe episodes (p < 0.05) ( 16 ). However, despite antibiotic pre-treatment being used, in the study by Popa et al. ( 16 ) as well as in the present one, it was not required to demonstrate non-inferiority of FMT. Moreover, none of the MBK-01-treated subjects with no antibiotic pre-treatment showed recurrences. Additionally, MBK-01 did not increase the frequency of AEs commonly associated with CDI or standard antibiotic treatment. None of the SAEs were probably or definitely related to either treatment, as most could be attributed to the participants´ compromised clinical condition. A more detailed analysis would be necessary to evaluate the potential contribution of underlying comorbidities or concomitant medications. Despite these considerations, MBK-01 appears to be a safe and well-tolerated treatment, similar to other microbiome products ( 39 ). MBK-01 offers several advantages over both traditional FMT and fidaxomicin. Its standardized capsule formulation and single-dose administration eliminate the need for invasive delivery methods, improving patient compliance and accessibility. Moreover, MBK-01 has demonstrated efficacy without the need for prior antibiotic treatment, highlighting its potential as a standalone therapy for CDI. This streamlined approach not only reduces antibiotic use but also achieves outcomes at least comparable to more invasive FMT techniques, such as colonoscopy ( 9 , 36 ). One of the main limitations of the study was the challenge of statistically comparing MBK-01 with fidaxomicin, given that fidaxomicin is highly effective treatment. This made it difficult to identify significant differences in superiority analyses. Additionally, the limited sample size and low study completion rates (below 50%) restrict the generalizability of the findings. These limitations were evident in the subgroup of patients without prior antibiotic treatment, where the small sample size made it difficult to detect significant differences between treatments. Although a robust intention-to-treat approach and subgroup analyses provided valuable insights, the open-label design introduces the risk of potential bias. In addition, most studies evaluating the efficacy of FMT in CDI focus on rCDI, limiting comparisons when discussing primary episodes. Another important consideration is that the study did not include severe CDI cases, which limits the extrapolation of findings to patients with more severe infections. Additionally, regarding long-term safety, a prospective study following 609 patients for up to 6.8 years found a low risk of infection transmission and no direct FMT-related long-term complications. Most reported new diagnoses (e.g., gastrointestinal issues, infections, weight gain) were deemed unrelated to FMT ( 40 ). While these results support the long-term safety of FMT, further studies are needed to confirm these findings. Despite these limitations, the study demonstrated that reduced antibiotic use correlates with lower recurrence rates, regardless of the treatment employed. This study provides compelling evidence for the potential of MBK-01 to redefine CDI treatment paradigms, particularly by reducing antibiotic reliance. While current guidelines primarily recommend FMT for recurrent CDI cases, the observed efficacy of MBK-01 in primary CDI suggests it could be considered for broader use. The integration of MBK-01 into global clinical practice is a real possibility, especially given the rising concern of antibiotic resistance and the limited treatment options for CDI. Another key consideration is that the availability of MBK-01 could facilitate easier access to FMT in Europe while reducing variability in its composition compared to the current reliance on multiple “homemade” FMT preparations. These findings align with the global need for microbiota preserving therapies, offering a sustainable solution for CDI. In conclusion, MBK-01 is shown to be an effective therapy in CDI. In primary CDI episodes and when no antibiotic pre-treatment was used, MBK-01 demonstrated non-inferiority to fidaxomicin, potentially reducing the need for antibiotics. For rCDI, MBK-01 showed superior efficacy compared to fidaxomicin. Overall, MBK-01 represents an effective, safe, and easy-to-administer treatment for CDI. Declarations Transparency Declaration Conflict of Interest The authors declare no conflicts of interest related to this study. This statement is consistent with the individual conflict of interest disclosure forms submitted by each author by ICMJE guidelines. Funding This study did not receive external funding. All expenses related to the development and execution of the clinical trial were covered by Mikrobiomik Healthcare Company S.L. Acknowledgments We would like to express our sincere gratitude to all the hospitals and clinical centers that participated in the development and execution of this clinical trial. We are especially grateful to the Departments of Infectious Diseases, Microbiology, and Pharmacy for their invaluable contributions to patient recruitment, clinical data collection, and microbiological analyses. We are also deeply grateful to all the patients who participated in this study. Their willingness and trust were essential in making this research possible. The preliminary results of this study were presented at the SEIMC 2024 (Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica) annual congress by Dr. Elena Bereciartua. Data Access Dr. Javier Cobo Reinoso and Dr. Olaia Aurtenetxe Saez had full access to all the data in the study. Dr. Javier Cobo serves as the guarantor for the accuracy and integrity of the data presented. Author Contributions Javier Cobo Reinoso and Olaia Aurtenetxe Saez contributed equally to the study design, data analysis, and drafting and critical revision of the manuscript. Other co-authors (as listed in the manuscript): contributed to patient recruitment, data collection, statistical analysis, and manuscript review. All authors have read and approved the final version of the manuscript and agree with its content. Authors: Javier Cobo, M.D., Ph.D., Elena Bereciartua, M.D., Javier Crespo, M.D., Ph.D., Esther Saez de Adana, M.D., Alicia Rico, M.D., María Luisa Martín, M.D., Jose Luis Calleja, M.D., Ph.D., Fernando Cereto, M.D., Ph.D., Juan José Castón, M.D., Ph.D., Esperanza Merino, M.D., Ph.D., Alex Soriano, M.D., Ph.D., Daniel Carnevali, M.D., Jordi Guardiola, M.D., Patricia Muñoz, M.D., Ph.D., José Ramón Paño-Pardo, M.D., Ph.D., Olaia Aurtenetxe, Ph.D, Patricia del Río, Ph.D., Celia Morales, Ph.D., Juan Basterra, M.D. References Polage CR, Solnick JV and Cohen SH. Nosocomial diarrhea: evaluation and treatment of causes other than Clostridium difficile. Clin Infect Dis. 2012;55 (7): 982-9. Di Bella S, Sanson G, Monticelli J, et al. Clostridioides difficile infection: history, epidemiology, risk factors, prevention, clinical manifestations, treatment, and future options. Clin Microbiol Rev . 2024;37 (2): e0013523. Wingen-Heimann SM, Davies K, Viprey VF, et al. Clostridioides difficile infection (CDI): A pan-European multicenter cost and resource utilization study, results from the Combatting Bacterial Resistance in Europe CDI (COMBACTE-CDI). Clin Microbiol Infect . 2023;29 (5): 651.e1-651.e8. Mizusawa M, Carroll KC. Advances and required improvements in methods to diagnosing Clostridioides difficile infections in the healthcare setting. Expert Rev Mol Diagn. 2021;21 (3):311-321. Louie TJ, Miller MA, Mullane KM, et al. Fidaxomicin versus vancomycin for Clostridium difficile infection. N Engl J Med. 2011;364 (5):422-431. Cornely OA, Crook DW, Esposito R, et al. Fidaxomicin versus vancomycin for infection with Clostridium difficile in Europe, Canada, and the USA: a double-blind, non-inferiority, randomised controlled trial. Lancet Infect Dis . 2012;12 (4):281-9. Johnson S, Lavergne V, Skinner AM, et al. Clinical Practice Guideline by the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA): 2021 Focused Update Guidelines on Management of Clostridioides difficile Infection in Adults. Clin Infect Dis . 2021;73 (5):e1029-e1044. van Prehn J, Reigadas E, Vogelzang EH, et al. European Society of Clinical Microbiology and Infectious Diseases: 2021 update on the treatment guidance document for Clostridioides difficile infection in adults. Clin Microbiol Infect . 2021;27 Suppl 2:S1-S21. Baunwall SMD, Lee MM, Eriksen MK, et al. Faecal microbiota transplantation for recurrent Clostridioides difficile infection: An updated systematic review and meta-analysis. EClinicalMedicine. 2020;29-30:100642. Cheng YW, Alhaffar D, Saha S, et al. Fecal microbiota transplantation is safe and effective in patients with Clostridioides difficile infection and cirrhosis. Clin Gastroenterol Hepatol . 2021;19 (8):1627-1634. Mendelsohn RB, Kaltsas A, King S, et al. Fecal Microbiota Transplantation Is Safe for Clostridiodies difficile Infection in Patients with Solid Tumors Undergoing Chemotherapy. Dig Dis Sci . 2022;67 (6):2503-2509. Hvas CL, Dahl Jørgensen SM, Jørgensen SP, et al. Fecal microbiota transplantation is superior to fidaxomicin for treatment of recurrent Clostridium difficile infection. Gastroenterology. 2019;156 (5):1324-1332.e3. Camacho-Ortiz A, Gutiérrez-Delgado EM, Garcia-Mazcorro JF, et al. Randomized clinical trial to evaluate the effect of fecal microbiota transplant for initial Clostridium difficile infection in intestinal microbiome. PLoS One. 2017;12 (12):e0189768. Juul FE, Garborg K, Bretthauer M, et al. Fecal Microbiota Transplantation for Primary Clostridium difficile Infection. N Engl J Med. 2018;378 (26):2535-2536. Roshan N, Clancy AK, Borody TJ. Faecal Microbiota Transplantation is Effective for the Initial Treatment of Clostridium difficile Infection: A Retrospective Clinical Review. Infect Dis Ther . 2020;9 (4):935-942. Popa D, Neamtu B, Mihalache M, et al. Fecal Microbiota Transplant in Severe and Non-Severe Clostridioides difficile Infection. Is There a Role of FMT in Primary Severe CDI? J Clin Med. 2021;10 (24):5822. DeFilipp Z, Bloom PP, Torres Soto M, et al. Drug-Resistant E. coli Bacteremia Transmitted by Fecal Microbiota Transplant. N Engl J Med . 2019;381 (21):2043-2050. US Food and Drug Administration. Safety alert regarding use of fecal microbiota for transplantation and additional safety protections pertaining to SARS-CoV-2 and COVID-19. 2020. (https://www.fda.gov/vaccines-blood-biologics/safety-availability-biologics/safety-alert-regarding-use-fecal-microbiota-transplantation-and-additional-safety-protections). Accessed 24 Sep 2024. Hocking L, Ianiro G, Leong RW, et al. Faecal microbiota transplantation for recurrent C. difficile infections: challenges and improvement opportunities for clinical practice and healthcare systems. Aliment Pharmacol Ther . 2023;57 (5):549-564. Madoff SE, Urquiaga M, Alonso CD, Kelly CP. Prevention of recurrent Clostridioides difficile infection: A systematic review of randomized controlled trials. Anaerobe. 2020;61:102098. Reigadas E, Bouza E, Olmedo M, et al. Faecal microbiota transplantation for recurrent Clostridioides difficile infection: experience with lyophilized oral capsules. J Hosp Infect . 2020;105 (2):319-324. Debast SB, Bauer MP, Kuijper EJ; European Society of Clinical Microbiology and Infectious Diseases. European Society of Clinical Microbiology and Infectious Diseases: update of the treatment guidance document for Clostridium difficile infection. Clin Microbiol Infect . 2014;20 Suppl 2:1-26. Wei S, Bahl MI, Baunwall SMD, Dahlerup JF, Hvas CL, Licht TR. Gut microbiota differs between treatment outcomes early after fecal microbiota transplantation against recurrent Clostridioides difficile infection. Gut Microbes . 2022;14 (1):2084306. Feuerstadt P, Louie TJ, Lashner B, Wang EL, et al. SER-109, an Oral Microbiome Therapy for Recurrent Clostridioides difficile Infection. N Engl J Med. 2022, 386:220-229 Khanna S, Assi M, Lee C, et al. Efficacy and Safety of RBX2660 in PUNCH CD3, a Phase III, Randomized, Double-Blind, Placebo-Controlled Trial with a Bayesian Primary Analysis for the Prevention of Recurrent Clostridioides difficile Infection [published correction appears in Drugs. 2022 Oct;82 (15):1539. Rao K, Micic D, Natarajan M, et al. Clostridium difficile ribotype 027: relationship to age, detectability of toxins A or B in stool with rapid testing, severe infection, and mortality. Clin Infect Dis. 2015;61 (2):233-241. Redmond SN, Cadnum JL, Jencson AL, et al. Emergence and Spread of Clostridioides difficile Isolates With Reduced Fidaxomicin Susceptibility in an Acute Care Hospital. Clin Infect Dis . 2025; ciaf028. Straub TJ, Lombardo MJ, Bryant JA, et al. Impact of a Purified Microbiome Therapeutic on Abundance of Antimicrobial Resistance Genes in Patients With Recurrent Clostridioides difficile Infection. Clin Infect Dis. 2024;78 (4):833-841. Hvas CL, Dahl Jørgensen SM, Jørgensen SP, et al. Fecal Microbiota Transplantation Is Superior to Fidaxomicin for Treatment of Recurrent Clostridium difficile Infection. Gastroenterology. 2019;156 (5):1324-1332.e3. Vardakas KZ, Polyzos KA, Patouni K, Rafailidis PI, Samonis G, Falagas ME. Treatment failure and recurrence of Clostridium difficile infection following treatment with vancomycin or metronidazole: a systematic review of the evidence. Int J Antimicrob Agents . 2012;40 (1):1-8. Cornely OA, Miller MA, Louie TJ, Crook DW, Gorbach SL. Treatment of first recurrence of Clostridium difficile infection: fidaxomicin versus vancomycin. Clin Infect Dis . 2012;55 Suppl 2 (Suppl 2):S154-61. Escudero-Sánchez, R., Valencia-Alijo, A., Cuéllar Tovar, S. et al. Real-life experience with fidaxomicin in Clostridioides difficile infection: a multicenter cohort study on 244 episodes. Infection. 2021;49: 475–482. Louie T, Golan Y, Khanna S, et al. VE303, a Defined Bacterial Consortium, for Prevention of Recurrent Clostridioides difficile Infection: A Randomized Clinical Trial. JAMA . 2023;329 (16):1356-1366. Tariq R, Syed T, Yadav D, et al. Outcomes of Fecal Microbiota Transplantation for C. difficile Infection in Inflammatory Bowel Disease: A Systematic Review and Meta-analysis. J Clin Gastroenterol . 2023;57 (3):285-293. Hota SS, Sales V, Tomlinson G, et al. Oral Vancomycin Followed by Fecal Transplantation Versus Tapering Oral Vancomycin Treatment for Recurrent Clostridium difficile Infection: An Open-Label, Randomized Controlled Trial. Clin Infect Dis. 2017;64 (3):265-271. Pomares Bascuñana RÁ, Veses V, Sheth CC. Effectiveness of fecal microbiota transplant for the treatment of Clostridioides difficile diarrhea: a systematic review and meta-analysis. Lett Appl Microbiol . 2021;73 (2):149-158. Minkoff NZ, Aslam S, Medina M, Tanner-Smith EE, Zackular JP, Acra S, Nicholson MR, Imdad A. Fecal microbiota transplantation for the treatment of recurrent Clostridioides difficile (Clostridium difficile). Cochrane Database Syst Rev. 2023;4 (4): CD013871. Baunwall SMD, Ellegaard S, Mejlby M, et al. Faecal microbiota transplantation for first or second Clostridioides difficile infection (EarlyFMT): a randomized, double-blind, placebo-controlled trial. Lancet Gastroenterol Hepatol. 2022;7 (12):1083-1091. Sims MD, Khanna S, Feuerstadt P, et al. Safety and Tolerability of SER-109 as an Investigational Microbiome Therapeutic in Adults With Recurrent Clostridioides difficile Infection: A Phase 3, Open-Label, Single-Arm Trial. JAMA Netw Open . 2023;6 (2):e2255758. Saha S, Mara K, Pardi DS and Khanna S. Long-term safety of fecal microbiota transplantation for recurrent Clostridioides difficile infection. Gastroenterology. 2021;160 (6):1961–1969.e3. Tables Tables 1 to 3 are available in the Supplementary Files section Additional Declarations No competing interests reported. Supplementary Files ICD01protocol01072025.pdf SupplementaryAppendixICD0101072025.pdf ICD01BBDDVer.6.022Nov2022nopw.xlsx De-identified patient data Table1.pdf Table 1. Characteristics of the Participants at Baseline. Demographic and clinical characteristics of patients at study entry in the MBK-01 and fidaxomicin groups. Table2.pdf Table 2. Recurrence A/B test analyses. Recurrence A/B test analyses. The table includes the difference between recurrences in percentage, Z-scores and p-values for both non-inferiority and superiority testing (separately). Note: all values correspond to the ITT (Intention-to-Treat) population. α=0.0294. Table3.pdf Table 3. Serious Adverse Events (SAEs). Detailed list of Serious Adverse Events (SAEs) reported during the study for both MBK-01 and fidaxomicin treatment groups. None of these events were deemed related to the treatments by investigators, highlighting their independence from the study medication. N/A: not applicable. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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CONSORT guidelines were considered to elaborate the flow chart. ITT: Intention to treat population. SP: Safety population.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7712660/v1/38679e85fbfb26deb907e825.png"},{"id":99186953,"identity":"9fdd9871-aa4d-4832-a7dc-0b1390522b0e","added_by":"auto","created_at":"2025-12-30 00:08:39","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":167879,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7712660/v1/e46b09ffb40d796631258f90.png"},{"id":99186963,"identity":"b0f8ac23-df94-4884-b725-18ec61c1d39c","added_by":"auto","created_at":"2025-12-30 00:08:40","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":119681,"visible":true,"origin":"","legend":"\u003cp\u003eTime to recurrence expressed in weeks in the overall population in the MBK-01 (red) and in the fidaxomicin-treated (blue) groups, indicating the cumulative recurrences in percentage by week and group. Kaplan-Meier curves were employed to estimate survival probabilities.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7712660/v1/187626367071e46ff95a5104.png"},{"id":105033529,"identity":"23014973-9fda-45d8-a112-66dd78eb8606","added_by":"auto","created_at":"2026-03-20 07:19:23","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1426062,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7712660/v1/919a2a5b-5e20-438e-9bd1-fa30289cb6bd.pdf"},{"id":99186958,"identity":"7988bd48-2efe-415c-b256-89aef7593861","added_by":"auto","created_at":"2025-12-30 00:08:39","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":947959,"visible":true,"origin":"","legend":"","description":"","filename":"ICD01protocol01072025.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7712660/v1/905509b2da49824a7547b8ba.pdf"},{"id":99186959,"identity":"8e9ebe32-ac5d-46e2-ab26-9bd769f8a663","added_by":"auto","created_at":"2025-12-30 00:08:39","extension":"pdf","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":210450,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryAppendixICD0101072025.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7712660/v1/c13981a503e50b7c14693f1f.pdf"},{"id":99186969,"identity":"341168df-e954-45d4-b981-64b240567765","added_by":"auto","created_at":"2025-12-30 00:08:41","extension":"xlsx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":65464704,"visible":true,"origin":"","legend":"\u003cp\u003eDe-identified patient data\u003c/p\u003e","description":"","filename":"ICD01BBDDVer.6.022Nov2022nopw.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-7712660/v1/cdaf8b45afb88bd1e2cada67.xlsx"},{"id":99315812,"identity":"5e5ac9b3-d0e3-4a32-a9ac-9d26f28097dc","added_by":"auto","created_at":"2025-12-31 16:27:22","extension":"pdf","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":221900,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTable 1. Characteristics of the Participants at Baseline. \u003c/strong\u003eDemographic and clinical characteristics of patients at study entry in the MBK-01 and fidaxomicin groups.\u003c/p\u003e","description":"","filename":"Table1.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7712660/v1/6e1ed227b5d2682febde6267.pdf"},{"id":99186950,"identity":"a9ac7f9e-bdf8-4662-b13d-c50789937975","added_by":"auto","created_at":"2025-12-30 00:08:39","extension":"pdf","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":221119,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTable 2. Recurrence A/B test analyses. \u003c/strong\u003eRecurrence A/B test analyses. The table includes the difference between recurrences in percentage, Z-scores and p-values for both non-inferiority and superiority testing (separately). Note: all values correspond to the ITT (Intention-to-Treat) population. α=0.0294.\u003c/p\u003e","description":"","filename":"Table2.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7712660/v1/08fe410f774df23c546c7f83.pdf"},{"id":99186945,"identity":"af316c65-b10e-4f4b-bced-8915c70d7790","added_by":"auto","created_at":"2025-12-30 00:08:38","extension":"pdf","order_by":6,"title":"","display":"","copyAsset":false,"role":"supplement","size":220907,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTable 3. Serious Adverse Events (SAEs). \u003c/strong\u003eDetailed list of Serious Adverse Events (SAEs) reported during the study for both MBK-01 and fidaxomicin treatment groups. None of these events were deemed related to the treatments by investigators, highlighting their independence from the study medication. N/A: not applicable.\u003c/p\u003e","description":"","filename":"Table3.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7712660/v1/4cc574ca469436de2bd114a3.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eFMT capsules (MBK-01) compared to fidaxomicin for the treatment of primary and recurrent Clostridioides difficile infection\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003e\u003cem\u003eClostridiodes difficile\u003c/em\u003e infection (CDI) is the main cause of nosocomial diarrhea in developed countries, representing up to 25% of cases of antibiotic-associated diarrhea (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). CDI symptoms usually range from mild to moderate diarrhea but can escalate to pseudomembranous colitis, toxic megacolon, septic shock, and even death in severe cases (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). CDI constitutes an important economic burden for Western healthcare systems (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). Its reported incidence currently remains elevated, partially by the inappropriate use of the antibiotics and the emergence of more virulent CD strains, but also by the advancements in diagnostic methods (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eAntibiotics constitute the first line of treatment against CDI. Fidaxomicin has demonstrated comparable efficacy to vancomycin with lower rates of recurrence at 28 days post-treatment (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e). Consequently, both the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA) recommend the use of fidaxomicin for primary cases and the first recurrence of CDI, while vancomycin is considered an alternative treatment (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). The European Society of Clinical Microbiology and Infectious Diseases similarly advises this approach (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eA peculiarity of CDI is its tendency to recur after successful treatment, which occurs in up to 20% of cases\u003csup\u003e2\u003c/sup\u003e. Fecal microbiota transplantation (FMT) has emerged as a therapeutic option in cases of recurrent CDI (rCDI), demonstrating high efficacy and safety, also in patients with different comorbidities (\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). FMT has historically been compared to vancomycin in most studies and only in one prior study has it been directly compared to fidaxomicin for recurrent episodes of CDI (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). FMT has been also proposed as a potential treatment for primary CDI (\u003cspan additionalcitationids=\"CR14 CR15\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). However, some safety problems were reported in FMT associated to a poor fecal donor screening (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e). Thus, the FDA recommends FMT only in those patients with multiple recurrences of CDI who have failed antibiotic treatment and after an appropriate screening of both donor and donor fecal specimen.\u003c/p\u003e\u003cp\u003eEffectively bringing FMT to patients requires much more than just the existence of a clinically effective procedure (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e). A centralized and commercialized FMT product could reduce variability, ensure high-quality standards, and improve patients' access.\u003c/p\u003e\u003cp\u003eIn a meta-analysis involving 38 randomized clinical trials and 8,102 participants, the superiority of FMT in preventing rCDI was demonstrated, showing only mild gastrointestinal adverse events (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e). Thus, the present phase III, prospective follow-up clinical trial was conducted to evaluate the efficacy and safety of the investigational oral medicinal FMT product (MBK-01 capsules) compared to fidaxomicin in patients with both recurrent and primary episodes of CDI.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eTrial design and Participants\u003c/h2\u003e\u003cp\u003e This randomized, open-label, controlled multicenter phase III trial was performed from July 2021 through November 2023 in accordance with the national (Royal Decree 1090/2015) and the European regulation (Union Directive 2001/20/EC), following all the ethical principles of the Declaration of Helsinki. Spanish regulatory authorities and the Ethics Committee of Euskadi approved the trial.\u003c/p\u003e\u003cp\u003eParticipants included adults (\u0026ge;\u0026thinsp;18 years) with confirmed CDI, either primary or recurrent), experiencing an episode of diarrhea (\u0026ge;\u0026thinsp;3 stools/24 hours) and testing positive for CD toxin A and/or B in fecal samples by a direct toxin detection test or by the PCR technique for the detection of toxin/s producing genes. Patients with previous FMT were excluded. Detailed eligibility criteria are provided in the \u003cem\u003eSupplementary Appendix\u003c/em\u003e. Written informed consent was obtained from all participants.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eRandomization and Interventions\u003c/h3\u003e\n\u003cp\u003eTwo treatment groups were included in the study. Participants who met all inclusion criteria and none of the exclusion criteria were randomly assigned in a 1:1 ratio to the experimental or control arm. Before randomization, vancomycin (3\u0026ndash;5 days) or fidaxomicin (\u0026lt;\u0026thinsp;24h) was permitted. In instances where these treatments were employed or if the patient was undergoing systemic treatment with other antibiotics, a 24-hour washout period was implemented before commencing the trial treatment. Participants assigned to the control group were treated with fidaxomicin at a dosage of 200 mg/12 hours for 10 days. Participants in the experimental FMT group were treated with MBK-01, which consisted of 4 capsules of 250 mg/capsule (\u0026ge;\u0026thinsp;2x10\u003csup\u003e11\u003c/sup\u003e microorganisms/g) administered orally in a single dose on an empty stomach. MBK-01 is an investigational medicinal product containing lyophilized heterologous intestinal microbiota (Full Spectrum \u0026amp; Purified Intestinal Microbiota) from healthy donors. In this study, MBK-01 was derived from seven different donors; however, each patient received FMT from a single donor, as each donation corresponded to a specific batch of MBK-01. The rationale for the dose was calculated to be above the minimum dose that has been proven to be effective with lyophilized FMT capsules (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e). Details of the inclusion and exclusion criteria of the donors and stool samples are provided in the \u003cem\u003eSupplementary Appendix\u003c/em\u003e.\u003c/p\u003e\u003cp\u003eAfter baseline assessment, when treatment was first administered, participants were followed up for a total of 6 months. In case of a participant withdrawn, the subject was monitored for \u0026ge;\u0026thinsp;30 days after treatment initiation. At baseline and subsequent visits, information of potential trial outcomes, adverse events and concomitant therapies were collected.\u003c/p\u003e\n\u003ch3\u003eEfficacy and Safety endpoints\u003c/h3\u003e\n\u003cp\u003eThe main objective was to evaluate the efficacy of MBK-01 compared to fidaxomicin at 8 weeks after initiation of the treatment. The primary efficacy outcome was the absence of recurrence of CDI. Recurrence means the reappearance of clinical manifestations of a new episode of CDI within 8 weeks after the onset of a previous episode that was resolved (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e). Moreover, the time to recurrence was also determined.\u003c/p\u003e\u003cp\u003eThe secondary objective involved evaluating the safety of MBK-01 at 6 months after the treatment, including treatment-related Adverse Events (AEs), and serious AEs (SAEs) in relation to the treatment. AEs were classified using MedDRA version 26.1.\u003c/p\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eThe study was initially designed to evaluate the superiority of MBK-01 compared to fidaxomicin in recurrent CDI cases. However, to expedite recruitment, the study was later expanded to include primary CDI cases as well. This adjustment led to the consideration of a non-inferiority analysis for the overall mixed population (primary and recurrent CDI) and a subsequent post-hoc subgroup analysis. This approach provided additional insights into the potential efficacy of MBK-01 as a first-line treatment.\u003c/p\u003e\u003cp\u003eThe efficacy analysis was planned to be carried out with the intention to treat (ITT) population, defined as all randomized participants, and for proportions of recurrence in the ITT modified (participants with available data at 8 weeks after finishing treatment and resolving the on-course episode). The difference in recurrence rates between treatments was analyzed by means of a one-sided A/B test (difference between proportions of independent samples). For the non-inferiority tests, the efficacy of the two treatments was compared as a difference of recurrence rates. The non-inferiority margin of -0.10 was incorporated into the null hypothesis as an acceptable maximum difference in non-recurrence proportions between the treatments. Based on the known recurrence rate of approximately 12% found in clinical trials we selected a non-inferiority margin of 10% (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe primary focus of the analysis remained on demonstrating non-inferiority in the mixed population, with subgroup analyses conducted to assess differences between primary and recurrent CDI cases. Although the study initially prioritized the superiority analysis for recurrent cases, this was later reframed as a post hoc exploratory analysis to provide additional insights and to guide future hypothesis generation.\u003c/p\u003e\u003cp\u003eThe statistical difference between proportions in the null hypothesis for the superiority analysis was set to 0, and a one-sided A/B test was carried out. Subgroup analyses of the probability of recurrence considered participants with primary or recurrent episodes and participants with no antibiotic pre-treatment.\u003c/p\u003e\u003cp\u003eSurvival analysis was performed, examining time to recurrence measured in weeks, with the treatment group acting as the independent variable. Kaplan-Meier curves were employed to estimate survival probabilities, while the log-rank test was utilized to compare between treatment groups.\u003c/p\u003e\u003cp\u003eAEs were analyzed descriptively, focusing on frequencies and percentages observed throughout the study period. This analysis was conducted on the Safety Population (SP).\u003c/p\u003e\u003cp\u003eThe significance level for all the inferential analyses presented was α\u0026thinsp;=\u0026thinsp;0.0294. The analyses were programmed in R statistical software (version 4.2.3, R Core Team, 2023), and the RStudio interface (version 2023.09.0).\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eRecruitment and baseline characteristics of the participants\u003c/h2\u003e\u003cp\u003eBetween October 2021 and November 2023, a total of 92 patients were enrolled among 21 centers in Spain. The ITT population consisted of 92 participants, of whom 45 were randomly assigned to the MBK-01 group and 47 to the fidaxomicin group. For the efficacy analysis, the modified ITT (mITT) population was defined as all ITT patients with available data on recurrence status at visit 4 or later. This population included 77 evaluable participants (37 in the MBK-01 group and 40 in the fidaxomicin group). The reasons why some participants were considered non-evaluable (8 in the MBK-01 group and 7 in the fidaxomicin group) are detailed in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe per-protocol (PP) population consisted of 48 participants. In the MBK-01 group, 23 participants completed the study, while 22 did not. In the fidaxomicin group, 25 participants completed the study, whereas 22 did not. The reasons for protocol deviations in these subjects are specified in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eFor non-evaluable participants, reasons for exclusion included factors such as prohibited medication use or adverse events. However, not all participants with these factors were excluded. Those who had medication prohibited by protocol but could still complete the required follow-up were included in the analysis, as their data remained valid for efficacy assessment. In contrast, participants whose protocol deviations could interfere with treatment evaluation, either by affecting the drug\u0026rsquo;s mechanism of action or leading to early discontinuation, were excluded. This distinction has been clarified in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eSafety analysis (SP) included 92 participants (45 in the MBK-01 and 47 in the fidaxomicin group). This approach ensured that safety outcomes were assessed in all participants who received at least one dose of the assigned treatment according to the study guidelines.\u003c/p\u003e\u003cp\u003eBaseline demographic and clinical characteristics were similar between groups, as shown in Table\u0026nbsp;1.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eEfficacy evaluation\u003c/h3\u003e\n\u003cp\u003eRecurrence-free survival at 8 weeks post-treatment was assessed in the modified intention-to-treat (mITT) population using both a non-inferiority and superiority approach.\u003c/p\u003e\u003cp\u003eMBK-01 demonstrated non-inferiority to fidaxomicin in the general population for CDI treatment. At 8 weeks post-treatment, recurrence was observed in 10.81% (4/37) of MBK-01 treated patients, compared to 22.50% (9/40) in the fidaxomicin group. The absolute risk difference was 11.69% (95% CI: \u0026minus;\u0026thinsp;7.7 to 30.7; p\u0026thinsp;=\u0026thinsp;0.013), confirming non-inferiority within the predefined margin of \u0026minus;\u0026thinsp;10%. However, superiority was not established. The number needed to treat (NNT) to prevent one recurrence was 8.55. These results are summarized in Table\u0026nbsp;2 and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn patients with primary CDI episodes, recurrence rates were similar between groups: 4.76% (1/21) in the MBK-01 group and 3.70% (1/27) in the fidaxomicin group, with an absolute risk difference of \u0026minus;\u0026thinsp;1.06% (95% CI: \u0026minus;\u0026thinsp;26.6 to 24.7). This confirms that MBK-01 was as effective as fidaxomicin in these cases (Table\u0026nbsp;2, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB)\u003c/p\u003e\u003cp\u003eFor recurrent CDI episodes, MBK-01 was significantly more effective. Recurrence occurred in 18.75% (3/16) of patients treated with MBK-01 compared to 61.54% (8/13) of those receiving fidaxomicin, with an absolute risk difference of 42.79% (95% CI: 2.6 to 71.8; p\u0026thinsp;=\u0026thinsp;0.003). Both non-inferiority and superiority were demonstrated. The odds ratio (OR) was 6.93, indicating that for each recurrence in the MBK-01 group, nearly seven recurrences occurred in the fidaxomicin group (Table\u0026nbsp;2, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC).\u003c/p\u003e\u003cp\u003eAmong patients without pretreatment with vancomycin or fidaxomicin, MBK-01 was also more effective, reducing recurrences by 20.00% compared to fidaxomicin (0% [0/17] vs. 20.00% [3/15]). The percentage risk difference was 20.00% (95% CI: \u0026minus;\u0026thinsp;4.8 to 48.6). Both non-inferiority and superiority were achieved (Table\u0026nbsp;2, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD).\u003c/p\u003e\u003cp\u003eWhen analyzing the overall time to recurrence, including all participants regardless of whether they experienced a recurrence, a trend was observed toward earlier and more frequent recurrences in the fidaxomicin group (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Among participants who experienced a recurrence, the mean time to recurrence was 31 days (SD\u0026thinsp;=\u0026thinsp;12 days) for fidaxomicin and 25 days (SD\u0026thinsp;=\u0026thinsp;25 days) for MBK-01. However, the greater variability in MBK-01 group prevents concluding due to the low number of recurrences observed. These findings are consistent with those seen in clinical practice and with other studies evaluating these treatments (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\n\u003ch3\u003eSafety Outcomes and treatment-related Adverse Events\u003c/h3\u003e\n\u003cp\u003eThe safety profile of MBK-01 was assessed throughout the study, focusing on treatment-emergent adverse events (AEs), serious adverse events (SAEs), and adverse events of special interest (AESIs). MBK-01, as a novel therapeutic agent, was generally well tolerated, with most reported adverse events being mild to moderate in severity.\u003c/p\u003e\u003cp\u003eAmong participants receiving MBK-01, the overall incidence of AEs was 46.35%. The most frequently reported events included diarrhea, increased C-reactive protein levels, vomiting and abdominal pain.\u003c/p\u003e\u003cp\u003eAESIs were reported with an incidence of 50.39% for MBK-01, with the most common events being increased C-reactive protein levels, vomiting and abdominal pain (4 events each). Diarrhea was the most prevalent AESI, reported in 26 cases.\u003c/p\u003e\u003cp\u003eA total of 11 SAEs were documented in the MBK-01 group, representing 68.75% of all reported SAEs. Although none of these events were deemed directly related to MBK-01, a detailed list is provided in supplementary materials (Table\u0026nbsp;3). Importantly, no treatment-related deaths were reported.\u003c/p\u003e\u003cp\u003eRegarding adverse events probably or definitely related to treatment, diarrhea was the only event observed in the MBK-01 group, affecting one participant. In the fidaxomicin-treated group, one subject experienced treatment-related diarrhea, while another participant experienced both flatulence and fatigue potentially related to the treatment.\u003c/p\u003e\u003cp\u003eFurthermore, no clinically significant changes in laboratory parameters, vital signs, or electrocardiogram readings were observed that could be attributed to MBK-01.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis phase III trial demonstrated that MBK-01 was non-inferior to fidaxomicin for the treatment of \u003cem\u003eClostridioides difficile\u003c/em\u003e infection (CDI) and superior in recurrent cases (rCDI). The results support MBK-01 as a potential therapeutic alternative, with the added advantage of avoiding antibiotic exposure. While recurrence free survival rates were comparable in primary CDI, MBK-01 showed a significantly lower recurrence rate in rCDI, suggesting that early microbiota-based intervention could enhance microbiota restoration and reduce recurrence risk, particularly in rCDI cases (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e). However, concerns remain regarding the safety of FMT, and further studies are needed to determine whether the absence of antibiotic exposure with MBK-01 translates into additional clinical benefits beyond recurrence prevention.\u003c/p\u003e\u003cp\u003eTo date, two microbiota-based therapies, SER-109 and RBX2660, have received regulatory approval in the USA for the prevention of CDI recurrence after standard antibiotic treatment. However, neither are indicated as a first-line treatment of the infection itself (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e). In addition, another investigational product based on Microbiota (VE3033) is being developed as a preventive measure following treatment with antibiotics (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e). In contrast, MBK-01, as demonstrated in this study, not only shows promise as an effective first-line treatment for primary CDI but also demonstrates superior efficacy in rCDI cases compared to fidaxomicin. Furthermore, MBK-01 was effective both with a very short course of vancomycin or fidaxomicin and even without the use of these antibiotics. This positions MBK-01 as a unique and innovative therapeutic option, addressing both the immediate and long-term needs of CDI management.\u003c/p\u003e\u003cp\u003eFidaxomicin and vancomycin are commonly used therapeutic alternatives for the treatment of CDI, especially in primary episodes. However, the growing concern over antibiotic resistance, particularly resistance to vancomycin and fidaxomicin, along with the rise of certain hypervirulent and multidrug-resistant (MDR) CD ribotypes, such as ribotypes 027 and 176, poses a significant challenge in CDI management (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e). A microbiota-based oral therapy has been shown to reduce antimicrobial resistance in rCDI patients compared to placebo (p\u0026thinsp;=\u0026thinsp;0.003) (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e). Since this study confirms the non-inferiority of MBK-01 to fidaxomicin, it is essential to emphasize the indirect benefits of reducing antibiotic use. In our study, recurrence rates were relatively low compared to some previous trials, which reported rates of 29% for FMT, 67% for fidaxomicin, and 81% for vancomycin in rCDI patients (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e). Earlier studies reported recurrence rates of 24.0% and 35.5% for vancomycin, while fidaxomicin-treated patients had a recurrence rate ranging from 16.3% to 26.4% for both primary and recurrent episodes (\u003cspan additionalcitationids=\"CR31\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e). In a randomized phase 2 trial involving patients with primary or recurrent CDI, recurrence rates at week 8 were 13.8% with high-dose oral VE303 (a defined bacterial consortium), 37% with a low-dose, and 45.5% with placebo (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e). However, a meta-analysis reported a 22% recurrence rate after the first FMT (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e). In contrast, MBK-01-treated patients in this study had a recurrence rate of 18.75%, significantly lower than fidaxomicin (61.54%) and below several previously published rates (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e). This suggests that FMT, and by extension MBK-01, offers a therapeutic alternative with superior efficacy compared to other standard antibiotics (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eOne of the most innovative aspects of this trial was the evaluation of FMT in primary CDI episodes. We reported non-inferior efficacy of MBK-01 compared to fidaxomicin in this subgroup, aligning with a prospective randomized trial where FMT by enema showed no statistical differences with metronidazole (56% vs 45% full primary response, p\u0026thinsp;=\u0026thinsp;1.00) in primary CDI (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). Moreover, 78% of the FMT-treated patients achieved an overall treatment response compared to 45% for metronidazole (p\u0026thinsp;=\u0026thinsp;0.20) (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). A recent randomized controlled trial (EarlyFMT) showed significantly higher CDI resolution rates at 8 weeks with FMT (90%) compared to placebo (33%; p\u0026thinsp;=\u0026thinsp;0.0003), leading to early trial termination for ethical reasons (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e). In another retrospective study, 59 patients with primary CDI were treated with two FMT infusions after pre-treatment with vancomycin and/or metronidazole for 10\u0026ndash;14 days. Four to eight weeks post-FMT, there was a significant reduction in abdominal pain (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), diarrhea, and bleeding (both p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). FMT demonstrated high efficacy, low recurrences, and no adverse events (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). However, as patients received 10\u0026ndash;14 days of antibiotic pre-treatment, FMT was primarily employed as a \"recurrence prevention\" strategy rather than as a standalone treatment for CDI. This context should be considered when interpreting the results.\u003c/p\u003e\u003cp\u003eFurthermore, it is not surprising that FMT shows greater effectiveness in primary episodes compared to secondary or tertiary episodes. A retrospective trial involving 96 patients showed that FMT following 10-day antibiotic pre-treatment was more effective in preventing recurrences in primary (5.25%) compared to secondary (15.15%) or tertiary (27.3%) severe episodes (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). However, despite antibiotic pre-treatment being used, in the study by Popa et al. (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e) as well as in the present one, it was not required to demonstrate non-inferiority of FMT. Moreover, none of the MBK-01-treated subjects with no antibiotic pre-treatment showed recurrences.\u003c/p\u003e\u003cp\u003eAdditionally, MBK-01 did not increase the frequency of AEs commonly associated with CDI or standard antibiotic treatment. None of the SAEs were probably or definitely related to either treatment, as most could be attributed to the participants\u0026acute; compromised clinical condition. A more detailed analysis would be necessary to evaluate the potential contribution of underlying comorbidities or concomitant medications. Despite these considerations, MBK-01 appears to be a safe and well-tolerated treatment, similar to other microbiome products (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eMBK-01 offers several advantages over both traditional FMT and fidaxomicin. Its standardized capsule formulation and single-dose administration eliminate the need for invasive delivery methods, improving patient compliance and accessibility. Moreover, MBK-01 has demonstrated efficacy without the need for prior antibiotic treatment, highlighting its potential as a standalone therapy for CDI. This streamlined approach not only reduces antibiotic use but also achieves outcomes at least comparable to more invasive FMT techniques, such as colonoscopy (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eOne of the main limitations of the study was the challenge of statistically comparing MBK-01 with fidaxomicin, given that fidaxomicin is highly effective treatment. This made it difficult to identify significant differences in superiority analyses. Additionally, the limited sample size and low study completion rates (below 50%) restrict the generalizability of the findings. These limitations were evident in the subgroup of patients without prior antibiotic treatment, where the small sample size made it difficult to detect significant differences between treatments. Although a robust intention-to-treat approach and subgroup analyses provided valuable insights, the open-label design introduces the risk of potential bias. In addition, most studies evaluating the efficacy of FMT in CDI focus on rCDI, limiting comparisons when discussing primary episodes.\u003c/p\u003e\u003cp\u003eAnother important consideration is that the study did not include severe CDI cases, which limits the extrapolation of findings to patients with more severe infections. Additionally, regarding long-term safety, a prospective study following 609 patients for up to 6.8 years found a low risk of infection transmission and no direct FMT-related long-term complications. Most reported new diagnoses (e.g., gastrointestinal issues, infections, weight gain) were deemed unrelated to FMT (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e). While these results support the long-term safety of FMT, further studies are needed to confirm these findings. Despite these limitations, the study demonstrated that reduced antibiotic use correlates with lower recurrence rates, regardless of the treatment employed.\u003c/p\u003e\u003cp\u003eThis study provides compelling evidence for the potential of MBK-01 to redefine CDI treatment paradigms, particularly by reducing antibiotic reliance. While current guidelines primarily recommend FMT for recurrent CDI cases, the observed efficacy of MBK-01 in primary CDI suggests it could be considered for broader use.\u003c/p\u003e\u003cp\u003eThe integration of MBK-01 into global clinical practice is a real possibility, especially given the rising concern of antibiotic resistance and the limited treatment options for CDI. Another key consideration is that the availability of MBK-01 could facilitate easier access to FMT in Europe while reducing variability in its composition compared to the current reliance on multiple \u0026ldquo;homemade\u0026rdquo; FMT preparations. These findings align with the global need for microbiota preserving therapies, offering a sustainable solution for CDI. In conclusion, MBK-01 is shown to be an effective therapy in CDI. In primary CDI episodes and when no antibiotic pre-treatment was used, MBK-01 demonstrated non-inferiority to fidaxomicin, potentially reducing the need for antibiotics. For rCDI, MBK-01 showed superior efficacy compared to fidaxomicin. Overall, MBK-01 represents an effective, safe, and easy-to-administer treatment for CDI.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eTransparency Declaration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflicts of interest related to this study. This statement is consistent with the individual conflict of interest disclosure forms submitted by each author by ICMJE guidelines.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study did not receive external funding. All expenses related to the development and execution of the clinical trial were covered by Mikrobiomik Healthcare Company S.L.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to express our sincere gratitude to all the hospitals and clinical centers that participated in the development and execution of this clinical trial. We are especially grateful to the Departments of Infectious Diseases, Microbiology, and Pharmacy for their invaluable contributions to patient recruitment, clinical data collection, and microbiological analyses.\u003c/p\u003e\n\u003cp\u003eWe are also deeply grateful to all the patients who participated in this study. Their willingness and trust were essential in making this research possible.\u003c/p\u003e\n\u003cp\u003eThe preliminary results of this study were presented at the SEIMC 2024 (Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica) annual congress by Dr. Elena Bereciartua.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Access\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDr. Javier Cobo Reinoso and Dr. Olaia Aurtenetxe Saez had full access to all the data in the study. Dr. Javier Cobo serves as the guarantor for the accuracy and integrity of the data presented.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJavier Cobo Reinoso and Olaia Aurtenetxe Saez contributed equally to the study design, data analysis, and drafting and critical revision of the manuscript. Other co-authors (as listed in the manuscript): contributed to patient recruitment, data collection, statistical analysis, and manuscript review. All authors have read and approved the final version of the manuscript and agree with its content.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors:\u0026nbsp;\u003c/strong\u003eJavier Cobo, M.D., Ph.D., Elena Bereciartua, M.D., Javier Crespo, M.D., Ph.D., Esther Saez de Adana, M.D., Alicia Rico, M.D., María Luisa Martín, M.D., Jose Luis Calleja, M.D., Ph.D., Fernando Cereto, M.D., Ph.D., Juan José Castón, M.D., Ph.D., Esperanza Merino, M.D., Ph.D., Alex Soriano, M.D., Ph.D., Daniel Carnevali, M.D., Jordi Guardiola, M.D., Patricia Muñoz, M.D., Ph.D., José Ramón Paño-Pardo, M.D., Ph.D., Olaia Aurtenetxe, Ph.D, Patricia del Río, Ph.D., Celia Morales, Ph.D., Juan Basterra, M.D.\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003ePolage CR, Solnick JV and Cohen SH. Nosocomial diarrhea: evaluation and treatment of causes other than Clostridium difficile. Clin Infect Dis. 2012;55 (7): 982-9.\u003c/li\u003e\n \u003cli\u003eDi Bella S, Sanson G, Monticelli J, et al. Clostridioides difficile infection: history, epidemiology, risk factors, prevention, clinical manifestations, treatment, and future options. \u003cem\u003eClin Microbiol Rev\u003c/em\u003e. 2024;37 (2): e0013523.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eWingen-Heimann SM, Davies K, Viprey VF, et al. Clostridioides difficile infection (CDI): A pan-European multicenter cost and resource utilization study, results from the Combatting Bacterial Resistance in Europe CDI (COMBACTE-CDI). \u003cem\u003eClin Microbiol Infect\u003c/em\u003e. 2023;29 (5): 651.e1-651.e8.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eMizusawa M, Carroll KC. Advances and required improvements in methods to diagnosing Clostridioides difficile infections in the healthcare setting. \u003cem\u003eExpert Rev Mol Diagn.\u003c/em\u003e 2021;21 (3):311-321.\u003c/li\u003e\n \u003cli\u003e\u0026nbsp;Louie TJ, Miller MA, Mullane KM, et al. Fidaxomicin versus vancomycin for Clostridium difficile infection. \u003cem\u003eN Engl J Med.\u003c/em\u003e 2011;364 (5):422-431.\u003c/li\u003e\n \u003cli\u003eCornely OA, Crook DW, Esposito R, et al. Fidaxomicin versus vancomycin for infection with Clostridium difficile in Europe, Canada, and the USA: a double-blind, non-inferiority, randomised controlled trial. \u003cem\u003eLancet Infect Dis\u003c/em\u003e. 2012;12 (4):281-9.\u003c/li\u003e\n \u003cli\u003eJohnson S, Lavergne V, Skinner AM, et al. Clinical Practice Guideline by the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA): 2021 Focused Update Guidelines on Management of Clostridioides difficile Infection in Adults. \u003cem\u003eClin Infect Dis\u003c/em\u003e. 2021;73 (5):e1029-e1044.\u003c/li\u003e\n \u003cli\u003evan Prehn J, Reigadas E, Vogelzang EH, et al. European Society of Clinical Microbiology and Infectious Diseases: 2021 update on the treatment guidance document for Clostridioides difficile infection in adults. \u003cem\u003eClin Microbiol Infect\u003c/em\u003e. 2021;27 Suppl 2:S1-S21.\u003c/li\u003e\n \u003cli\u003eBaunwall SMD, Lee MM, Eriksen MK, et al. Faecal microbiota transplantation for recurrent Clostridioides difficile infection: An updated systematic review and meta-analysis. \u003cem\u003eEClinicalMedicine.\u003c/em\u003e 2020;29-30:100642.\u003c/li\u003e\n \u003cli\u003eCheng YW, Alhaffar D, Saha S, et al. Fecal microbiota transplantation is safe and effective in patients with Clostridioides difficile infection and cirrhosis. \u003cem\u003eClin Gastroenterol Hepatol\u003c/em\u003e. 2021;19 (8):1627-1634.\u003c/li\u003e\n \u003cli\u003e\u0026nbsp;Mendelsohn RB, Kaltsas A, King S, et al. Fecal Microbiota Transplantation Is Safe for Clostridiodies difficile Infection in Patients with Solid Tumors Undergoing Chemotherapy. \u003cem\u003eDig Dis Sci\u003c/em\u003e. 2022;67 (6):2503-2509.\u003c/li\u003e\n \u003cli\u003eHvas CL, Dahl J\u0026oslash;rgensen SM, J\u0026oslash;rgensen SP, et al. Fecal microbiota transplantation is superior to fidaxomicin for treatment of recurrent Clostridium difficile infection. \u003cem\u003eGastroenterology.\u003c/em\u003e 2019;156 (5):1324-1332.e3.\u003c/li\u003e\n \u003cli\u003eCamacho-Ortiz A, Guti\u0026eacute;rrez-Delgado EM, Garcia-Mazcorro JF, et al. Randomized clinical trial to evaluate the effect of fecal microbiota transplant for initial Clostridium difficile infection in intestinal microbiome. \u003cem\u003ePLoS One.\u003c/em\u003e 2017;12 (12):e0189768.\u003c/li\u003e\n \u003cli\u003eJuul FE, Garborg K, Bretthauer M, et al. Fecal Microbiota Transplantation for Primary Clostridium difficile Infection. \u003cem\u003eN Engl J Med.\u003c/em\u003e 2018;378 (26):2535-2536.\u003c/li\u003e\n \u003cli\u003eRoshan N, Clancy AK, Borody TJ. Faecal Microbiota Transplantation is Effective for \u003cem\u003ethe Initial Treatment of Clostridium difficile Infection: A Retrospective Clinical Review. Infect Dis Ther\u003c/em\u003e. 2020;9 (4):935-942.\u003c/li\u003e\n \u003cli\u003ePopa D, Neamtu B, Mihalache M, et al. Fecal Microbiota Transplant in Severe and Non-Severe Clostridioides difficile Infection. Is There a Role of FMT in Primary Severe CDI? \u003cem\u003eJ Clin Med.\u003c/em\u003e 2021;10 (24):5822.\u003c/li\u003e\n \u003cli\u003eDeFilipp Z, Bloom PP, Torres Soto M, et al. Drug-Resistant E. coli Bacteremia Transmitted by Fecal Microbiota Transplant. \u003cem\u003eN Engl J Med\u003c/em\u003e. 2019;381 (21):2043-2050.\u003c/li\u003e\n \u003cli\u003eUS Food and Drug Administration. Safety alert regarding use of fecal microbiota for transplantation and additional safety protections pertaining to SARS-CoV-2 and COVID-19. 2020. (https://www.fda.gov/vaccines-blood-biologics/safety-availability-biologics/safety-alert-regarding-use-fecal-microbiota-transplantation-and-additional-safety-protections). Accessed 24 Sep 2024.\u003c/li\u003e\n \u003cli\u003eHocking L, Ianiro G, Leong RW, et al. Faecal microbiota transplantation for recurrent C. difficile infections: challenges and improvement opportunities for clinical practice and healthcare systems. \u003cem\u003eAliment Pharmacol Ther\u003c/em\u003e. 2023;57 (5):549-564.\u003c/li\u003e\n \u003cli\u003eMadoff SE, Urquiaga M, Alonso CD, Kelly CP. Prevention of recurrent Clostridioides difficile infection: A systematic review of randomized controlled trials. \u003cem\u003eAnaerobe.\u003c/em\u003e 2020;61:102098.\u003c/li\u003e\n \u003cli\u003eReigadas E, Bouza E, Olmedo M, et al. Faecal microbiota transplantation for recurrent Clostridioides difficile infection: experience with lyophilized oral capsules. \u003cem\u003eJ Hosp Infect\u003c/em\u003e. 2020;105 (2):319-324.\u003c/li\u003e\n \u003cli\u003eDebast SB, Bauer MP, Kuijper EJ; European Society of Clinical Microbiology and Infectious Diseases. European Society of Clinical Microbiology and Infectious Diseases: update of the treatment guidance document for Clostridium difficile infection. \u003cem\u003eClin Microbiol Infect\u003c/em\u003e. 2014;20 Suppl 2:1-26.\u003c/li\u003e\n \u003cli\u003eWei S, Bahl MI, Baunwall SMD, Dahlerup JF, Hvas CL, Licht TR. Gut microbiota differs between treatment outcomes early after fecal microbiota transplantation against recurrent Clostridioides difficile infection. \u003cem\u003eGut Microbes\u003c/em\u003e. 2022;14 (1):2084306.\u003c/li\u003e\n \u003cli\u003eFeuerstadt P, Louie TJ, Lashner B, Wang EL, et al. SER-109, an Oral Microbiome Therapy for Recurrent Clostridioides difficile Infection. N Engl J Med. 2022, 386:220-229\u003c/li\u003e\n \u003cli\u003eKhanna S, Assi M, Lee C, et al. Efficacy and Safety of RBX2660 in PUNCH CD3, a Phase III, Randomized, Double-Blind, Placebo-Controlled Trial with a Bayesian Primary Analysis for the Prevention of Recurrent Clostridioides difficile Infection [published correction appears in Drugs. 2022 Oct;82 (15):1539.\u003c/li\u003e\n \u003cli\u003eRao K, Micic D, Natarajan M, et al. Clostridium difficile ribotype 027: relationship to age, detectability of toxins A or B in stool with rapid testing, severe infection, and mortality. \u003cem\u003eClin Infect Dis.\u003c/em\u003e 2015;61 (2):233-241.\u003c/li\u003e\n \u003cli\u003eRedmond SN, Cadnum JL, Jencson AL, et al. Emergence and Spread of Clostridioides difficile Isolates With Reduced Fidaxomicin Susceptibility in an Acute Care Hospital. \u003cem\u003eClin Infect Dis\u003c/em\u003e. 2025; ciaf028.\u003c/li\u003e\n \u003cli\u003eStraub TJ, Lombardo MJ, Bryant JA, et al. Impact of a Purified Microbiome Therapeutic on Abundance of Antimicrobial Resistance Genes in Patients With Recurrent Clostridioides difficile Infection. \u003cem\u003eClin Infect Dis.\u003c/em\u003e 2024;78 (4):833-841.\u003c/li\u003e\n \u003cli\u003eHvas CL, Dahl J\u0026oslash;rgensen SM, J\u0026oslash;rgensen SP, et al. Fecal Microbiota Transplantation Is Superior to Fidaxomicin for Treatment of Recurrent Clostridium difficile Infection. Gastroenterology. 2019;156 (5):1324-1332.e3.\u003c/li\u003e\n \u003cli\u003eVardakas KZ, Polyzos KA, Patouni K, Rafailidis PI, Samonis G, Falagas ME. Treatment failure and recurrence of Clostridium difficile infection following treatment with vancomycin or metronidazole: a systematic review of the evidence. \u003cem\u003eInt J\u003c/em\u003e\u003cem\u003eAntimicrob Agents\u003c/em\u003e. 2012;40 (1):1-8.\u003c/li\u003e\n \u003cli\u003eCornely OA, Miller MA, Louie TJ, Crook DW, Gorbach SL. Treatment of first recurrence of Clostridium difficile infection: fidaxomicin versus vancomycin. \u003cem\u003eClin Infect Dis\u003c/em\u003e. 2012;55 Suppl 2 (Suppl 2):S154-61.\u003c/li\u003e\n \u003cli\u003eEscudero-S\u0026aacute;nchez, R., Valencia-Alijo, A., Cu\u0026eacute;llar Tovar, S. et al. Real-life experience with fidaxomicin in Clostridioides difficile infection: a multicenter cohort study on 244 episodes. Infection. 2021;49: 475\u0026ndash;482.\u003c/li\u003e\n \u003cli\u003eLouie T, Golan Y, Khanna S, et al. VE303, a Defined Bacterial Consortium, for Prevention of Recurrent Clostridioides difficile Infection: A Randomized Clinical Trial. \u003cem\u003eJAMA\u003c/em\u003e. 2023;329 (16):1356-1366.\u003c/li\u003e\n \u003cli\u003eTariq R, Syed T, Yadav D, et al. Outcomes of Fecal Microbiota Transplantation for C. difficile Infection in Inflammatory Bowel Disease: A Systematic Review and Meta-analysis. \u003cem\u003eJ Clin Gastroenterol\u003c/em\u003e. 2023;57 (3):285-293.\u003c/li\u003e\n \u003cli\u003eHota SS, Sales V, Tomlinson G, et al. Oral Vancomycin Followed by Fecal Transplantation Versus Tapering Oral Vancomycin Treatment for Recurrent Clostridium difficile Infection: An Open-Label, Randomized Controlled Trial. \u003cem\u003eClin Infect Dis.\u003c/em\u003e 2017;64 (3):265-271.\u003c/li\u003e\n \u003cli\u003ePomares Bascu\u0026ntilde;ana R\u0026Aacute;, Veses V, Sheth CC. Effectiveness of fecal microbiota transplant for the treatment of Clostridioides difficile diarrhea: a systematic review and meta-analysis. \u003cem\u003eLett Appl Microbiol\u003c/em\u003e. 2021;73 (2):149-158.\u003c/li\u003e\n \u003cli\u003eMinkoff NZ, Aslam S, Medina M, Tanner-Smith EE, Zackular JP, Acra S, Nicholson MR, Imdad A. Fecal microbiota transplantation for the treatment of recurrent Clostridioides difficile (Clostridium difficile). Cochrane Database Syst Rev. 2023;4 (4): CD013871.\u003c/li\u003e\n \u003cli\u003eBaunwall SMD, Ellegaard S, Mejlby M, et al. Faecal microbiota transplantation for first or second Clostridioides difficile infection (EarlyFMT): a randomized, double-blind, placebo-controlled trial. Lancet Gastroenterol Hepatol. 2022;7 (12):1083-1091.\u003c/li\u003e\n \u003cli\u003eSims MD, Khanna S, Feuerstadt P, et al. Safety and Tolerability of SER-109 as an Investigational Microbiome Therapeutic in Adults With Recurrent Clostridioides difficile Infection: A Phase 3, Open-Label, Single-Arm Trial. \u003cem\u003eJAMA Netw Open\u003c/em\u003e. 2023;6 (2):e2255758.\u003c/li\u003e\n \u003cli\u003eSaha S, Mara K, Pardi DS and Khanna S. Long-term safety of fecal microbiota transplantation for recurrent Clostridioides difficile infection. Gastroenterology. 2021;160 (6):1961\u0026ndash;1969.e3.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 3 are available in the Supplementary Files section\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":true,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-7712660/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7712660/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cu\u003eObjectives:\u003c/u\u003e \u003cem\u003eClostridioides difficile\u003c/em\u003e infection (ICD) is a major cause of nosocomial diarrhea, with high recurrence rates following standard antibiotic treatments. Fecal microbiota transplantation (FMT) has emerged as a promising therapy for recurrent CDI (rCDI), though its efficacy in primary CDI remains under investigation. This study evaluates the safety and efficacy of MBK-01, a novel oral FMT capsule, compared to fidaxomicin, the current standard of care, in both primary and rCDI.\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eMethods\u003c/u\u003e: In this randomized, open-label, multicenter phase III trial, patients with primary or rCDI were randomized to receive MBK01 (with or without a short period of prior antibiotic treatment) or fidaxomicin (200 mg/12h for 10 days). The primary endpoint was absence of recurrence at 8 weeks post-treatment. Secondary endpoints included time to recurrence and adverse events at 6 months. The study is registered with ClinicalTrials.gov (NCT05201079).\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eResults\u003c/u\u003e: 92 patients with CDI (45 in the MBK-01 group and 47 in the fidaxomicin group) were enrolled across 21 centers in Spain. MBK-01 demonstrated non-inferiority to fidaxomicin, with recurrence rate differences of 11.69% in the overall population (p=0.013), -1.06% in primary CDI cases (p=0.013), 42.79% in recurrent episodes (p=0.003), and 20% in participants without prior antibiotic treatment (p=0.008). Additionally, in rCDI, MBK-01 showed superiority compared to fidaxomicin (p=0.014). Notably, MBK-01 achieved 100% effectiveness in participants without antibiotic pre-treatment, versus 80% for fidaxomicin. The median time to recurrence in the overall population was similar. MBK-01 was associated with fewer treatment-related adverse events.\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eConclusions\u003c/u\u003e: MBK-01 represents a safe, effective, and less antibiotic-dependent option for CDI, particularly in recurrent cases. Its efficacy in primary CDI and favorable safety profile suggests that MBK-01 could serve as first-line therapy, potentially reducing antibiotic reliance and improving outcomes. These findings support broader use of microbiota-based therapies in the management of CDI.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number: \u003c/strong\u003eNCT05201079\u003c/p\u003e","manuscriptTitle":"FMT capsules (MBK-01) compared to fidaxomicin for the treatment of primary and recurrent Clostridioides difficile infection","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-30 00:08:14","doi":"10.21203/rs.3.rs-7712660/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"41dbcc62-61de-4482-b35a-bd207939b657","owner":[],"postedDate":"December 30th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-03T13:25:05+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-30 00:08:14","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7712660","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7712660","identity":"rs-7712660","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}