CLB101TM Improves Gastrointestinal Symptom Burden in Overweight Adults: A Randomized, Double-Blind, Placebo-Controlled Study

Background. Anaerostipes caccae CLB101TM is a next-generation probiotic that directly produces butyrate and is hypothesized to reduce gastrointestinal symptoms by strengthening intestinal barrier integrity. Clinical evidence for A. caccae in symptomatic adult populations remains limited. Methods. Ninety-three adults were randomized 1:1 to CLB101TM ( n=47) or placebo (n=46) for 28 days. The primary outcome was safety and tolerability as assessed by the number, frequency, and severity of adverse events. Secondary outcomes were focused on exploring signals of efficacy, and included change in the Gastrointestinal Symptom Rating Scale (GSRS) composite score from baseline to Week 4. Five GSRS subcategories were additionally evaluated. Exploratory endpoints included daily self-reported GI symptoms, as well as stool and blood measures of intestinal barrier function. Results. 71 participants were evaluated for the GSRS (77.5% female, aged 42.1 SD 12 years, BMI mean 31.3 SD 3.6). No adverse events were reported in the placebo arm, while three self-limiting adverse events were associated with CLB101TM administration. CLB101TM reduced GI symptom burden versus placebo on the primary GSRS composite at Week 4 (mean change: -1.60 vs -0.90; MWU p=0.040). Two secondary subscales reached significance after FDR-BH correction: Reflux (mean change: -1.26 vs -0.30; FDR-adjusted p=0.024) and Abdominal Pain (mean change: -1.86 vs -0.83; FDR-adjusted p=0.024). Daily symptom diaries showed trends toward greater reductions in abdominal discomfort, bloating, and flatulence in the active arm at the end of study. This study population did not demonstrate signs of intestinal barrier dysfunction. Product adherence averaged 97.7%. Conclusions. CLB101TM was safe and tolerable and significantly improved overall GI symptom burden, reflux, and abdominal pain after four weeks of daily supplementation in overweight symptomatic adults. Trial Registration. The trial was approved by Sterling IRB (14583-NACraft) and registered with ClinicalTrials.gov (NCT07336615).