The Progression of Microbiome Therapeutics for the Management of Gastrointestinal Diseases and Beyond.

There has been an increased ability to investigate human microbiota through next generation sequencing and functional assessment. This advancement has rapidly expanded our ability to study and manipulate the gastrointestinal microbiome to mitigate disease. Fecal microbiota transplantation (FMT), a therapy which broadly transfers the entire intestinal ecosystem, has been explored as a potential therapeutic in a variety of gastrointestinal, hepatic and extraintestinal conditions. The field however continues to evolve with a movement towards precision microbiome therapeutics individualizing care for various disorders. This review will describe the use of FMT, microbiota restoration and precision microbiome therapeutics focusing in gastrointestinal and hepatic diseases.

Retrospective subgroup analysis of fecal microbiota, live-jslm (REBYOTA®) administered by colonoscopy under enforcement discretion for the prevention of recurrent Clostridioides difficile infection.

Background: Fecal microbiota, live-jslm (RBL; REBYOTA®), is the first Food and Drug Administration (FDA)-approved, single-dose, rectally administered, microbiota-based live biotherapeutic product for preventing Clostridioides difficile infection (CDI) recurrence. Alternative routes of administration are of clinical interest. Objectives: Evaluate the safety and efficacy of RBL administration via colonoscopy. Design: Retrospective analysis of electronic medical records of participants administered RBL via colonoscopy under FDA enforcement discretion. Methods: The number of participants with treatment and/or procedure-emergent adverse events (TEAEs) was evaluated. Treatment success and sustained clinical response, defined as the absence of CDI recurrence within 8 weeks and 6 months, respectively, were evaluated. Results: TEAEs were experienced by 75% (6/8) of participants; most were mild to moderate in severity, and none due to RBL or its administration. Most participants had treatment success (80%; 8/10); 75% (6/8) had sustained clinical response. Conclusion: Real-world safety and efficacy of RBL administered via colonoscopy were consistent with clinical trials of rectally administered RBL.

Clinical outcomes before and after prucalopride treatment: an observational study in patients with chronic idiopathic constipation in the USA.

INTRODUCTION: This real-world US-based claims study compared constipation-related symptoms and complications 6 months before and after prucalopride initiation in adults with chronic idiopathic constipation (CIC). METHODS: This observational, retrospective cohort analysis used the IBM MarketScan® Commercial Claims and Encounters and the Medicare Supplemental databases (January 2015-June 2020). Prucalopride-treated patients (≥18 years old) who had ≥1 constipation-related International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) diagnosis code during the baseline or study period were included. The proportions of patients with constipation-related symptoms (abdominal pain, abdominal distension [gaseous], incomplete defecation, and nausea) and constipation-related complications (anal fissure and fistula, intestinal obstruction, rectal prolapse, hemorrhoids, perianal venous thrombosis, peri-anal/peri-rectal abscess, and rectal bleeding) were examined. Constipation-related symptoms and complications were identified using ICD-10-CM, ICD-10-Procedure Coding System, or Current Procedural Terminology codes. Data were stratified by age (overall, 18-64 years, ≥65 years). RESULTS: This study included 690 patients: mean (standard deviation) patient age was 48.0 (14.7) years and 87.5% were women. The proportions of patients overall with constipation-related symptoms decreased 6 months after prucalopride initiation (abdominal pain [50.4% vs 33.3%, P<0.001]; abdominal distension [gaseous] [23.9% vs 13.3%, P<0.001]; and nausea [22.6% vs 17.7%, P<0.01]; no improvements observed for incomplete defecation). Similarly, the proportions of patients overall with constipation-related complications decreased 6 months after prucalopride initiation (intestinal obstruction [4.9% vs 2.0%, P<0.001]; hemorrhoids [10.7% vs 7.0%, P<0.05]; and rectal bleeding [4.1% vs 1.7%, P<0.05]). DISCUSSION: This study suggests that prucalopride may be associated with improved constipation-related symptoms and complications 6 months after treatment initiation.

Efficacy and Health-Related Quality of Life Impact of Fecal Microbiota, Live-jslm: A Post Hoc Analysis of PUNCH CD3 Patients at First Recurrence of Clostridioides difficile Infection.

INTRODUCTION: Clostridioides difficile infection (CDI) causes symptoms of varying severity and negatively impacts patients' health-related quality of life (HRQL). Despite antibiotic treatment, recurrence of CDI (rCDI) is common and imposes clinical and economic burdens on patients. Fecal microbiota, live-jslm (REBYOTA [RBL]) is newly approved in the USA for prevention of rCDI following antibiotic treatments. We analyzed efficacy and HRQL impact of RBL vs. placebo in patients at first rCDI using data from the phase 3 randomized, double-blind placebo-controlled clinical trial, PUNCH CD3. METHODS: This post hoc analysis included patients at first rCDI fromPUNCH CD3. Treatment success (i.e., absence of diarrhea within 8 weeks post-treatment) was analyzed adjusting for baseline patient characteristics. HRQL was measured using the Clostridioides difficile Quality of Life Survey (Cdiff32); absolute scores and change from baseline in total and domain (physical, mental, and social) scores were summarized and compared between arms. Analyses were conducted for the trial's blinded phase only. RESULTS: Among 86 eligible patients (32.8% of the overall trial population, RBL 53 [61.6%], placebo 33 [38.4%]), RBL-treated patients had significantly lower odds of recurrence (i.e., greater probability of treatment success) at week 8 vs. placebo (odds ratio 0.35 [95% confidence interval 0.13, 0.98]). Probability of treatment success at week 8 was 81% for RBL and 60% for placebo, representing 21% absolute and 35% relative increases for RBL (crude proportions 79.2% vs. 60.6%; relative risk 0.53, p = 0.06). Additionally, RBL was associated with significantly higher Cdiff32 total (change score difference 13.5 [standard deviation 5.7], p < 0.05) and mental domain (16.2 [6.0], p < 0.01) scores vs. placebo from baseline to week 8. CONCLUSION: Compared to placebo, RBL demonstrated a significantly higher treatment success in preventing further rCDI and enhanced HRQL among patients at first recurrence, establishing RBL as an effective treatment to prevent further recurrences in these patients. TRIAL REGISTRATION: ClinicalTrials.gov Identifier NCT03244644.

Fecal Microbiota, Live-jslm for the Prevention of Recurrent Clostridioides difficile Infection : Subgroup Analysis of PUNCH CD2 and PUNCH CD3.

GOALS: To assess fecal microbiota, live-jslm (REBYOTA, abbreviated as RBL, formerly RBX2660) efficacy and safety in participants grouped by recurrent Clostridioides difficile infection (rCDI) risk factors and treatment-related variables. BACKGROUND: RBL is the first microbiota-based live biotherapeutic approved by the US Food and Drug Administration for the prevention of rCDI in adults after antibiotic treatment for rCDI. STUDY: Treatment success rates across subgroups for PUNCH CD3 (NCT03244644) were estimated using a Bayesian hierarchical model, borrowing data from PUNCH CD2 (NCT02299570). Treatment-emergent adverse events were summarized for the double-blind treatment period within 8 weeks. RESULTS: Treatment differences between RBL and placebo at 8 weeks were similar to the total population for most subgroups. Treatment effect sizes were similar between CDI tests, higher for oral vancomycin courses >14 days versus ≤14 days and higher for antibiotic washout periods of 3 days versus ≤2 days. The largest reductions in the rate of rCDI with RBL versus placebo were observed for participants with a 3-day CDI antibiotic washout period and participants with ≥4 previous CDI episodes. Most RBL-treated participants experienced TEAEs that were mild or moderate in severity and related to preexisting conditions. CONCLUSION: This analysis provides further evidence of RBL efficacy and safety across subgroups, including those at high risk for rCDI.

Patient Perception of Route of Rectal Administration of Live Biotherapeutic Product for Recurrent Clostridioides difficile Infection.

Introduction: CDI is a recurrent disease that is treated with antibiotics, but patients commonly experience repeat infections with significant impacts on hospital budgets and patient health quality. Standard of care management includes the antibiotics, vancomycin and fidaxomicin, which frequently provide clinical response, but do not avoid recurrence of Clostridioides difficile infection (rCDI). These recurrent infections occur due to dysbiosis of the colonic microbiota. One adjunctive therapeutic approach is to restore the deficient gastrointestinal flora using fecal microbiota transplantation (FMT) or live biotherapeutic products (LBP) when given after standard of care antimicrobials, which have been successful in reducing repeat infections with success rates up to 88%. FMT or LBP can be given by various routes. Methods: Two groups of subjects aged ≥18 years with at least one previous CDI episode within the previous 36 months completed self-administered online surveys to assess the acceptability of an LBP administered rectally. Group 1 consisted of LBP-recipients who had received RBL (REBYOTA) rectally as part of the Phase III PUNCH CD3 clinical trial. Group 2 consisted of LBP-naïve subjects who volunteered to participate and had experienced CDI within the prior 36 months but had no history of receiving FMT or LBP therapy. Results: LBP-recipients considered rectal administration easy (96%) and quick (94%), while 98% of respondents considered the lack of need for bowel preparation appealing. Most LBP-recipients (96%) wished they had earlier access to RBL. Most LBP-naïve subjects (87%) were likely or somewhat likely to consider a rectally administered treatment and 80% preferred a treatment option that does not require bowel preparation. Many of these subjects (76%) expressed interest in finding out about new treatment options for rCDI. Discussion: LBP-recipients and LBP-naïve subjects alike felt that rectal delivery of microbiome therapy is not only acceptable but highly interesting as a treatment avenue.

First Clostridioides difficile Recurrence Is Highest Following Concomitant Antimicrobial Administration During and Within 30 Days of Treatment.

BACKGROUND: Clostridioides difficile infection (CDI) is an epidemic with the strongest risk factor being antibiotic usage. Patients who get CDI frequently require concomitant antibiotics for other indications around the time of their infection. AIMS: To assess the recurrence of CDI (rCDI) in patients receiving concomitant antibiotics at the same time or shortly thereafter treatment of CDI. METHODS: We retrospectively reviewed records for patients with their first inpatient CDI episode. Patients were grouped into those who didn't receive concomitant antibiotics (noABx), those receiving antibiotics at the same time as treatment of CDI (ABxDURING), those receiving antibiotics within 30-days of completion of CDI therapy (ABxAFTER) and those who received antibiotics both during and after CDI treatment (ABxDuringAfter). Our primary outcome was recurrence within 14-90 days; other outcomes included ICU stay at the time of diagnosis, 30-day ICU transfer, 30-day colectomy, and readmission. RESULTS: 457 patients had CDI during admission (mean age: 66.4 years, 51.9% female). 64.1% were exposed to concomitant antibiotics. Recurrence rates were 4.3%, 6.1%, 13.8% and 19.1%, for noABx, ABxDURING, ABxAFTER and ABxDuringAfter, respectively. Patients with ABxDuringAfter had the highest rates of rCDI when compared to noABx [OR 5.67, 95% CI (2.18-14.72)]. CONCLUSIONS: There is a high rate of utilization of non-CDI antibiotics during or shortly after completing CDI treatment with high rates of recurrence within 90-days. Concomitant antimicrobials alter the opportunity for the microbiota to re-grow and worsens dysbiosis leading to increases in recurrence. Concomitant antimicrobial stewardship remains important in patients being treated for CDI and shortly after treatment.

Effect of Fecal Microbiota, Live-Jslm (REBYOTA [RBL]) on Health-Related Quality of Life in Patients With Recurrent Clostridioides difficile Infection: Results From the PUNCH CD3 Clinical Trial.

Background: Recurrence of Clostridioides difficile infection (rCDI) is common, prolonging disease morbidity and leading to poor quality of life. We evaluated disease-specific health-related quality of life (HRQL) in patients with rCDI treated with fecal microbiota, live-jslm (REBYOTA [RBL]; Rebiotix) versus placebo. Methods: This was a secondary analysis of a randomized, double-blind, placebo-controlled phase 3 study (PUNCH CD3). The disease-specific Clostridioides difficile Quality of Life Survey (Cdiff32) was administered at baseline and at weeks 1, 4, and 8. Changes in Cdiff32 total and domain (physical, mental, social) scores from baseline to week 8 were compared between RBL and placebo and for responders and nonresponders. Results: Findings were analyzed in a total of 185 patients (RBL, n = 128 [69.2%]; placebo, n = 57 [30.8%]) with available Cdiff32 data. Patients from both arms showed significant improvements in Cdiff32 scores relative to baseline across all outcomes and at all time points (all P < .001); RBL-treated patients showed significantly greater improvements in mental domain than those receiving placebo. In adjusted analyses, RBL-treated patients showed greater improvements than placebo in total score and physical and mental domains (all P < .05). Similar improvement in mental domain was observed among responders, while nonresponders showed numerical improvements with RBL but not placebo. Conclusions: In a phase 3 double-blinded clinical trial, RBL-treated patients reported more substantial and sustained disease-specific HRQL improvements than placebo-treated patients. Clinical Trials Registration: ClinicalTrials.gov NCT03244644 (https://clinicaltrials.gov/ct2/show/NCT03244644).

Prevalence of Comorbid Factors in Patients With Recurrent Clostridioides difficile Infection in ECOSPOR III, a Randomized Trial of an Oral Microbiota-Based Therapeutic.

BACKGROUND: Although comorbidities are risk factors for recurrent Clostridioides difficile infection (rCDI), many clinical trials exclude patients with medical conditions such as malignancy or immunosuppression. In a phase 3, double-blind, placebo-controlled, randomized trial (ECOSPOR III), fecal microbiota spores, live (VOWST, Seres Therapeutics; hereafter "VOS," formerly SER-109), an oral microbiota therapeutic, significantly reduced the risk of rCDI at week 8. We evaluated the efficacy of VOS compared with placebo in patients with comorbidities and other risk factors for rCDI. METHODS: Adults with rCDI were randomized to receive VOS or placebo (4 capsules daily for 3 days) following standard-of-care antibiotics. In this post hoc analysis, the rate of rCDI through week 8 was assessed in VOS-treated participants compared with placebo for subgroups including (i) Charlson comorbidity index (CCI) score category (0, 1-2, 3-4, ≥5); (ii) baseline creatinine clearance (<30, 30-50, >50 to 80, or >80 mL/minute); (iii) number of CDI episodes, inclusive of the qualifying episode (3 and ≥4); (iv) exposure to non-CDI-targeted antibiotics after dosing; and (v) acid-suppressing medication use at baseline. RESULTS: Of 281 participants screened, 182 were randomized (59.9% female; mean age, 65.5 years). Comorbidities were common with a mean overall baseline age-adjusted CCI score of 4.1 (4.1 in the VOS arm and 4.2 in the placebo arm). Across all subgroups analyzed, VOS-treated participants had a lower relative risk of recurrence compared with placebo. CONCLUSIONS: In this post hoc analysis, VOS reduced the risk of rCDI compared with placebo, regardless of baseline characteristics, concomitant medications, or comorbidities.

Safety of fecal microbiota, live-jslm (REBYOTA™) in individuals with recurrent Clostridioides difficile infection: data from five prospective clinical trials.

Background: Microbiota-based treatments reduce the incidence of recurrent Clostridioides difficile infections (rCDIs), but prospectively collected safety data needed to broaden patient access and protect public health have been limited. Objectives: We provide cumulative safety data from five prospective clinical trials evaluating fecal microbiota, live-jslm (RBL) - the first microbiota-based live biotherapeutic product approved by the US Food and Drug Administration - for preventing rCDI in adults. Design: Integrated safety analysis includes three phase II trials (PUNCH CD, PUNCH CD2, PUNCH Open-Label) and two phase III trials (PUNCH CD3, PUNCH CD3-OLS) of RBL. Methods: Trial participants were at least 18 years of age with documented rCDI who completed standard-of-care antibiotic therapy before treatment with RBL. Assigned study treatment regimen was one or two doses of RBL (or placebo) administered rectally, depending on the trial design. In four of the five trials, participants with CDI recurrence within 8 weeks after RBL or placebo administration were eligible for treatment with open-label RBL. Treatment-emergent adverse events (TEAEs) were recorded for at least 6 months following last study treatment; in PUNCH CD2 and PUNCH Open-Label trials, TEAEs and serious TEAEs were collected through 12 and 24 months, respectively. Results: Among the five trials, 978 participants received at least one dose of RBL (assigned treatment or after recurrence) and 83 participants received placebo only. TEAEs were reported in 60.2% of Placebo Only participants and 66.4% of RBL Only participants. Only abdominal pain, nausea, and flatulence were significantly higher in the RBL Only group compared with the Placebo Only group. Most TEAEs were mild or moderate in severity and were most frequently related to preexisting conditions. There were no reported infections for which the causative pathogen was traced to RBL. Potentially life-threatening TEAEs were infrequent (3.0% of participants). Conclusion: Across five clinical trials, RBL was well tolerated in adults with rCDI. In aggregate, these data consistently demonstrated the safety of RBL.

Retrospective Analysis of the Safety and Efficacy of Fecal Microbiota, Live-jslm (REBYOTATM) Administered Under Enforcement Discretion to Patients With Clostridioides difficile Infection.

Background: Fecal microbiota, live-jslm (RBL; REBYOTA™), the first microbiota-based live biotherapeutic approved by the US Food and Drug Administration to prevent recurrent Clostridioides difficile infection (rCDI) in adults, has been evaluated in 5 prospective clinical trials. A retrospective analysis considered the safety and efficacy of RBL administered under US Food and Drug Administration enforcement discretion to patients with rCDI and broad eligibility criteria mimicking real-world practice. Methods: We retrospectively identified adults with rCDI treated with RBL under enforcement discretion between November 1, 2015, and September 30, 2019, across 5 study sites. CDI diagnosis was based on site-specific practice. The primary safety set (PSS) included all patients who were naïve to previous RBL treatment and had continuously comprehensive medical records for 6 months following treatment. Results: The primary treatment cohort had 94 patients; the PSS included 64 patients with common comorbidities receiving diverse chronic therapeutics. Most treatment-emergent adverse events were mild to moderate in severity and comparable between comorbidity subgroups and the overall population. There were no serious adverse events related to RBL or the administration procedure. In the PSS, 82.8% of RBL-treated patients responded at 8 weeks, of whom 88.7% had sustained response through 6 months. The number of RBL doses administered had no marked effect on outcome. Conclusions: Together with prospective clinical trial outcomes, these findings support the efficacy and safety of RBL to prevent rCDI, with diagnostics and comorbidities representative of real-world clinical practice.

Idiopathic myointimal hyperplasia of the mesenteric veins: A systematic review and individual patient data regression analysis.

BACKGROUND AND AIM: Idiopathic myointimal hyperplasia of the mesenteric veins (IMHMV) is an uncommon cause of colonic ischemia for which surgical treatment is typically curative. We describe clinical, radiologic, and endoscopic findings in IMHMV patients to provide clinicians with a framework for pre-surgical identification of this rare disease. METHODS: We performed a systematic review of seven databases for IMHMV cases and identified additional cases from Yale New Haven Hospital records. To identify features specifically associated with colonic ischemia due to IMHMV, we performed multivariate logistic regression analysis incorporating data from a large cohort of patients with biopsy-proven ischemic colitis. RESULTS: A total of 124 patients with IMHMV were identified (80% male, mean age 53 years, 56% Caucasian). Presenting symptoms were most commonly abdominal pain (86%) and diarrhea (68%). The most affected areas were the sigmoid colon (91%) and rectum (61%). Complications associated with diagnostic delay occurred in 29% of patients. Radiologic vascular abnormalities including non-opacification of the inferior mesenteric vein were observed in 35% of patients. Of the patients, 97% underwent curative surgical resection. Compared with non-IMHMV colonic ischemia, IMHMV was significantly associated with younger age, male sex, absence of rectal bleeding on presentation, rectal involvement, and mucosal ulcerations on endoscopy. CONCLUSION: IMHMV is a rare, underreported cause of colonic ischemia that predominantly involves the rectosigmoid. Our findings suggest younger age, rectal involvement, and absence of rectal bleeding as clinical features to help identify select patients presenting with colonic ischemia as having higher likelihood of IMHMV and therefore consideration of upfront surgical management.

The burden of CDI in the United States: a multifactorial challenge.

Clostridioides difficile infection (CDI) affects approximately 500,000 patients annually in the United States, of these around 30,000 will die. CDI carries significant burdens including clinical, social and economic. While healthcare-associated CDI has declined in recent years, community-associated CDI is on the rise. Many patients are also impacted by recurrent C. difficile infections (rCDI); up to 35% of index CDI will recur and of these up to 60% will further recur with multiple recurrences observed. The range of outcomes adversely affected by rCDI is significant and current standard of care does not alter these recurrence rates due to the damaged gut microbiome and subsequent dysbiosis. The clinical landscape of CDI is changing, we discuss the impact of CDI, rCDI, and the wide range of financial, social, and clinical outcomes by which treatments should be evaluated.

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.

Importance: A safe and effective treatment for recurrent Clostridioides difficile infection (CDI) is urgently needed. Antibiotics kill toxin-producing bacteria but do not repair the disrupted microbiome, which promotes spore germination and infection recurrence. Objectives: To evaluate the safety and rate of CDI recurrence after administration of investigational microbiome therapeutic SER-109 through 24 weeks. Design, Setting, and Participants: This phase 3, single-arm, open-label trial (ECOSPOR IV) was conducted at 72 US and Canadian outpatient sites from October 2017 to April 2022. Adults aged 18 years or older with recurrent CDI were enrolled in 2 cohorts: (1) rollover patients from the ECOSPOR III trial who had CDI recurrence diagnosed by toxin enzyme immunoassay (EIA) and (2) patients with at least 1 CDI recurrence (diagnosed by polymerase chain reaction [PCR] or toxin EIA), inclusive of their acute infection at study entry. Interventions: SER-109 given orally as 4 capsules daily for 3 days following symptom resolution after antibiotic treatment for CDI. Main Outcomes and Measures: The main outcomes were safety, measured as the rate of treatment-emergent adverse events (TEAEs) in all patients receiving any amount of SER-109, and cumulative rates of recurrent CDI (toxin-positive diarrhea requiring treatment) through week 24 in the intent-to-treat population. Results: Of 351 patients screened, 263 were enrolled (180 [68.4%] female; mean [SD] age, 64.0 [15.7] years); 29 were in cohort 1 and 234 in cohort 2. Seventy-seven patients (29.3%) were enrolled with their first CDI recurrence. Overall, 141 patients (53.6%) had TEAEs, which were mostly mild to moderate and gastrointestinal. There were 8 deaths (3.0%) and 33 patients (12.5%) with serious TEAEs; none were considered treatment related by the investigators. Overall, 23 patients (8.7%; 95% CI, 5.6%-12.8%) had recurrent CDI at week 8 (4 of 29 [13.8%; 95% CI, 3.9%-31.7%] in cohort 1 and 19 of 234 [8.1%; 95% CI, 5.0%-12.4%] in cohort 2), and recurrent CDI rates remained low through 24 weeks (36 patients [13.7%; 95% CI, 9.8%-18.4%]). At week 8, recurrent CDI rates in patients with a first recurrence were similarly low (5 of 77 [6.5%; 95% CI, 2.1%-14.5%]) as in patients with 2 or more recurrences (18 of 186 [9.7%; 95% CI, 5.8%-14.9%]). Analyses by select baseline characteristics showed consistently low recurrent CDI rates in patients younger than 65 years vs 65 years or older (5 of 126 [4.0%; 95% CI, 1.3%-9.0%] vs 18 of 137 [13.1%; 95% CI, 8.0%-20.0%]) and patients enrolled based on positive PCR results (3 of 69 [4.3%; 95% CI, 0.9%-12.2%]) vs those with positive toxin EIA results (20 of 192 [10.4%; 95% CI, 6.5%-15.6%]). Conclusions and Relevance: In this trial, oral SER-109 was well tolerated in a patient population with recurrent CDI and prevalent comorbidities. The rate of recurrent CDI was low regardless of the number of prior recurrences, demographics, or diagnostic approach, supporting the beneficial impact of SER-109 for patients with CDI. Trial Registration: ClinicalTrials.gov identifier: NCT03183141.

Microbiota-Based Live Biotherapeutic RBX2660 for the Reduction of Recurrent Clostridioides difficile Infection in Older Adults With Underlying Comorbidities.

Background: Advanced age and underlying comorbidities are associated with greater rates of recurrence in patients with Clostridioides difficile infection (CDI). Reducing the likelihood of recurrence through treatment with an antimicrobial followed by a microbiota replacement therapy can decrease the burden of this infection and improve patient outcomes. We report the efficacy and safety of RBX2660, a microbiota-based live biotherapeutic, in older adults with recurrent CDI, grouped by comorbidities. Methods: In this post hoc subgroup analysis of the PUNCH CD3 trial, we assessed outcomes in older adults (age ≥65 years) grouped by Charlson Comorbidity Index severity scores at screening (moderate [3-4] and severe [≥5]) and by the presence of underlying cardiac, renal, or gastrointestinal disorders. Results: RBX2660 treatment success rates in older adults with comorbidities were consistent across subgroups and similar to those in the total RBX2660-treated population. A greater percentage of RBX2660-treated older adults remained free of CDI recurrence through 8 weeks following treatment compared with placebo-treated participants in all but 2 subgroups assessed. Across all subgroups, most treatment-emergent adverse events (TEAEs) were mild or moderate in severity and related to a preexisting condition. None of the serious or life-threatening TEAEs that occurred were related to RBX2660 or its administration. Occurrence of TEAEs did not cluster in any subgroup. Conclusions: RBX2660 is efficacious and safe in older adults with recurrent CDI and underlying comorbidities.