Development and Validation of a Novel Microbiome-Based Biomarker of Post-antibiotic Dysbiosis and Subsequent Restoration

Background: The human gut microbiota are important to health and wellness, and disrupted microbiota homeostasis, or “dysbiosis,” can cause or contribute to many gastrointestinal disease states. Dysbiosis can be caused by many factors, most notably antibiotic treatment. To correct dysbiosis and restore healthier microbiota, several investigational microbiota-based live biotherapeutic products (LBPs) are in formal clinical development. To better guide and refine LBP development and to better understand and manage the risks of antibiotic administration, biomarkers that distinguish post-antibiotic dysbiosis from healthy microbiota are needed. Here we report the development of a prototype Microbiome Health Index for post-Antibiotic dysbiosis (MHI-A).

Methods: MHI-A was developed and validated using longitudinal gut microbiome data from participants in clinical trials of RBX2660 and RBX7455 – investigational LBPs in development for reducing recurrent Clostridioides difficile infections (rCDI). The MHI-A algorithm relates the relative abundances of microbiome taxonomic classes that changed the most after RBX2660 or RBX7455 treatment, that strongly correlated with clinical response, and that reflect biological mechanisms believed important to rCDI. The diagnostic utility of MHI-A was reinforced using publicly available microbiome data from healthy or antibiotic-treated populations.

Results: MHI-A has high accuracy to distinguish post-antibiotic dysbiosis from healthy microbiota. MHI-A values were consistent across multiple healthy populations and were significantly shifted by antibiotic treatments known to alter microbiota compositions, shifted less by microbiota-sparing antibiotics. Clinical response to RBX2660 and RBX7455 correlated with a shift of MHI-A from dysbiotic to healthy values.

Conclusion: MHI-A is a promising biomarker of post-antibiotic dysbiosis and subsequent restoration. MHI-A may be useful for rank-ordering the microbiota-disrupting effects of antibiotics and as a pharmacodynamic measure of microbiota restoration.

1064. Treatment Success in Reducing Recurrent Clostridioides difficile Infection with Investigational Live Biotherapeutic RBX2660 Is Associated with Microbiota Restoration: Consistent Evidence from a Phase 3 Clinical Trial

Background

Several investigational microbiota-based live biotherapeutics are in clinical development for reducing recurrence of Clostridioides difficile infection (rCDI), including RBX2660 a liquid suspension of a broad consortium of microbiota, which includes Bacteridetes and Firmicutes. RBX2660 has been evaluated in >600 participants in 6 clinical trials. Here we report that RBX2660 induced significant shifts to the intestinal microbiota of treatment-responsive participants in PUNCH CD3—a Phase 3 randomized, double-blinded, placebo-controlled trial.

Methods

PUNCH CD3 participants received a single dose of RBX2660 or placebo between 24 to 72 hours after completing rCDI antibiotic treatment. Clinical response was the absence of CDI recurrence at eight weeks after treatment. Participants voluntarily submitted stool samples prior to blinded study treatment (baseline), 1, 4 and 8 weeks, 3 and 6 months after receiving study treatment. Samples were extracted and sequenced using shallow shotgun methods. Operational taxonomic unit (OTU) data were used to calculate relative taxonomic abundance, alpha diversity, and the Microbiome Health Index (MHI)—a biomarker of antibiotic-induced dysbiosis and restoration.

Results

Clinically, RBX2660 demonstrated superior efficacy versus placebo (70.4% versus 58.1%). From before to after treatment, RBX2660-treated clinical responders’ microbiome diversity shifted significantly (Mann-Whitney), and so did microbiome composition (Generalized Wald Test). Post-treatment changes were characterized by increased Bacteroidia and Clostridia and decreased Gammaproteobacteria and Bacilli, changes and were durable to at least 6 months. Repeated measures analysis confirmed that shifts were greater among RBX2660 responders compared to placebo responders (DMRepeat). The majority of responders’ MHI values shifted from a range common to antibiotic dysbiosis to a range common in healthy populations.

Figure 1

Left panel. Mean relative abundance taxonomic class level at timepoints for participants in PUNCH CD3 before and after RBX2660 treatment, and for doses of RBX2660 administered in PUNCH CD3. The four taxonomic classes that change most from before to after treatment are shown with the mean and confidence intervals based on fitting OTU data to a Dirichlet multinomial distribution. Right panel, MHI biomarker for the same time points and investigational product groups, shown as median (red) and individual samples. A previously calculated threshold of MHI = 7.2 is shown (dotted line), above which MHI values predict healthy, below which MHI values predict antibiotic-induced dysbiosis.

Conclusion

Among PUNCH CD3 clinical responders, RBX2660 significantly restored microbiota from less to more healthy compositions, and this restoration was durable to at least 6 months. These clinically-correlated microbiome shifts are highly consistent with results from multiple prior trials of RBX2660.

Disclosures

Ken Blount, PhD, Rebiotix Inc., a Ferring Company (Employee) Dana M. Walsh, PhD, Rebiotix (Employee)

1039. Rapid Restoration of Bile Acid Compositions After Treatment with RBX2660 for Recurrent Clostridioides difficile Infection—Results from the PUNCH CD3 Phase 3 Trial

Background

Microbiota-based treatments are increasingly evaluated as a strategy to reduce recurrence of Clostridioides difficile infection (rCDI), and their proposed mechanisms include restoration of the microbiota and microbiota-mediated functions, including bile acid metabolism. RBX2660—a broad-consortium investigational live biotherapeutic—has been evaluated in >600 participants in 6 clinical trials, with consistent reduction of rCDI recurrence. Here we report that fecal bile acid compositions were significantly restored in treatment-responsive participants in PUNCH CD3—a Phase 3 randomized, double-blinded, placebo-controlled trial of RBX2660.

Methods

PUNCH CD3 participants received a single dose of RBX2660 or placebo between 24 to 72 hours after completing rCDI antibiotic treatment. Clinical response was the absence of CDI recurrence at eight weeks after treatment. Participants voluntarily submitted stool samples prior to blinded study treatment (baseline), 1, 4 and 8 weeks, 3 and 6 months after receiving study treatment. A liquid chromatography tandem mass spectrometry method was developed to extract and quantify 33 bile acids from all participant fecal samples received up to the 8-week time point. Mean bile acid compositions were fit to a Dirichlet multinomial distribution and compared across time points and between RBX2660- and placebo-treated participants.

Results

Clinically, RBX2660 demonstrated superior efficacy versus placebo (70.4% versus 58.1%). RBX2660-treated clinical responders’ bile acid compositions shifted significantly from before to after treatment. Specifically, primary bile acids predominated before treatment, whereas secondary bile acids predominated after treatment (Figure 1A). These changes trended higher among RBX2660 responders compared to placebo responders. Importantly, median levels of lithocholic acid (LCA) and deoxycholic acid (DCA) showed large, significant increases after treatment (Figure 1B).

Conclusion

Among PUNCH CD3 clinical responders, RBX2660 significantly restored bile acids from less to more healthy compositions. These clinically correlated bile acid shifts are highly consistent with results from a prior trial of RBX2660.

Disclosures

Romeo Papazyan, PhD, Ferring Research Institute (Employee) Bryan Fuchs, PhD, Ferring Pharmaceuticals (Employee) Ken Blount, PhD, Rebiotix Inc., a Ferring Company (Employee)

129. Antimicrobial Resistance Genes Were Reduced Following Administration of Investigational Microbiota-Based Live Biotherapeutic RBX2660 to Individuals with Recurrent Clostridioides difficile Infection

Background

Intestinal colonization by antimicrobial resistant (AMR) pathogens is a known health and infection risk, and is common among individuals with recurrent Clostridioides difficile infections (rCDI). Accordingly, therapeutic approaches that decolonize the gut of AMR pathogens could be valuable to patients to reduce risk of associated illnesses. Herein, we assessed gut colonization with AMR bacteria before and after treatment with RBX2660—a microbiota-based investigational live biotherapeutic—in the PUNCH CD3 Phase 3 trial for reducing CDI recurrence.

Methods

rCDI participants enrolled in PUNCH CD3 received a blinded single dose of RBX2660 or placebo within 24 to 72 hours after completing antibiotic treatment for the most recent rCDI episode. Clinical response was the absence of CDI recurrence at eight weeks after treatment, and participants were asked to submit stool samples prior to RBX2660 or placebo treatment (baseline) and 1, 4 and 8 weeks, 3 and 6 months after study treatment. Samples were extracted and sequenced using a shallow shotgun method. The presence and number of AMR genes was determined for 175 participant samples and 116 RBX2660 samples using 90% K-mer sequence coverage based on the MEGARes database. AMR gene count data were collapsed into count columns to adjust for sparseness in the matrices and were analyzed using a Generalized Linear Mixed Model.

Results

Clinically, RBX2660 demonstrated superior efficacy versus placebo (70.4% and 58.1%, respectively), and the total AMR genes per participant decreased significantly from before to after treatment in RBX2660-treated responders (p< .05, Figure 1) and remained low to at least 6 months. Among genes that decreased in RBX2660 responders were clinically important extended-spectrum beta-lactamase (bla_TEM, bla_SHV, bla_CTX-M), vancomycin resistance (vanA, vanB), and fluoroquinolone resistance genes (gyrA, parC).

Total AMR genes per PUNCH CD3 participant among RBX2660-treated responders at the indicated time points and in the RBX2660 investigational product. The red lines indicate timepoint group medians.

Conclusion

In the PUNCH CD3 Phase 3 trial of RBX2660 for rCDI, AMR gene content decreased after RBX2660 treatment and remained low to at least 6 months, consistent with prior RBX2660 trials. This underscores the potential of microbiota-based biotherapeutics for decolonizing AMR bacteria from gut microbiota and thereby reducing AMR infection risks.

Disclosures

Heidi Hau, PhD, Rebiotix Inc. (Employee) Dana M. Walsh, PhD, Rebiotix (Employee) Ken Blount, PhD, Rebiotix Inc., a Ferring Company (Employee)

30. Antimicrobial Resistance Genes Are Reduced Following Administration of Investigational Microbiota-based Therapeutic RBX7455 to Individuals with Recurrent clostrioides Difficile Infection

Background

Antimicrobial resistance (AMR) is a challenge in individuals at risk for recurrent Clostrioides difficile infection (rCDI). Recognizing that AMR bacteria colonize the intestinal microbiota, therapeutic approaches that decolonize the gut of AMR bacteria would be valuable. Herein, we assessed the microbial resistome before and after treatment with RBX7455—a room temperature-stable, orally-administered investigational microbiota-based therapeutic—in a Phase 1 trial for reducing CDI recurrence.

Methods

This investigator-sponsored trial enrolled 30 rCDI patients in 3 open-label treatment groups (n=10 per group): 1) Four RBX7455 capsules BID for 4 days, 2) Four RBX7455 capsules BID for 2 days, 3) Two RBX7455 capsules BID for 2 days. RBX7455 administration began 48 hours after finishing CDI antibiotics. Participants were asked to submit stool samples at baseline, 1, 7, 28 and 56 days after treatment. These were extracted and sequenced using a shallow shotgun method. Relative taxonomic abundances at the class level and the presence of AMR genes were determined for 148 participant samples and 11 product samples using 90% K-mer sequence coverage based on the MEGARes database.

Results

Ninety percent of participants met the primary endpoint of no CDI recurrence through 8 weeks after treatment, and participant microbiome compositions became more similar to RBX7455 after treatment. The total AMR counts per participant decreased from before to after treatment (p< .05, mixed effects model), with the pattern of AMRs identified (resistome) becoming more like the RBX7455 resistome (Figure 1). Most notably, AMRs associated with multi-drug, fluoroquinolone, and betalactam resistance decreased from before to after treatment. There was no significant difference among the groups with respect to clinical response or changes in microbiome composition and AMR content.

Figure 1 Average total and per-class AMR gene counts in participant samples before and after RBX7455 treatment.

Conclusion

In a Phase 1 trial of RBX7455 for rCDI, AMR gene content decreased after treatment. This underscores the potential of microbiota-based therapies for decolonizing AMR bacteria from the gut microbiota. Continued clinical evaluation of RBX7455 is underway.

Disclosures

Dana Walsh, PhD, Rebiotix Inc. (Employee) Carlos Gonzalez, MS, BioRankings, LLC (Employee) Bill Shannon, PhD MBA, BioRankings, LLC (Employee) Ken Blount, PhD, Rebiotix Inc. (Employee)

29. Rapid Restoration of Bile Acid Compositions After Treatment with Investigational Microbiota-based Therapeutic RBX2660 for Recurrent clostrioides Difficile Infection

Background

Recurrent Clostrioides difficile infection (rCDI) is a public health threat associated with intestinal microbiome disruption (dysbiosis), which is postulated to increase CDI recurrence risk via disruption of bile acid(BA)-mediated resistance to C. difficile colonization. RBX2660 is an investigational microbiota-based therapeutic in clinical development for reducing rCDI recurrence. Herein, we assessed BA composition among participants in a Phase 2 trial of RBX2660 for rCDI.

Methods

In a double-blinded trial (PUNCH CD2), rCDI participants were randomized to receive RBX2660 or placebo. Primary efficacy was defined as absence of CDI recurrence at 8 weeks after the last study treatment. Participants were asked to provide stool samples before (baseline) and up to 24 months after treatment. A liquid chromatography tandem mass spectrometry method was developed to extract and quantify 36 BAs from a total of 167 participant stool samples from 47 participants. Participant-matched samples at baseline and 1, 4, and 8 weeks were compared with a linear mixed effects model.

Results

Primary BAs predominated at baseline but were significantly reduced (p&lt; .02) as early as 1 week after treatment and remained so to 24 months. Concurrently, secondary BAs, most notably deoxycholic acid (DCA) and lithocholic acid (LCA), were significantly increased (p&lt; .01) after treatment and remained so throughout. Moreover, increases in DCA and LCA were associated with treatment response (p=.05 and p&lt; .01, respectively), recognizing the limited sample size of treatment failures. Observed BA changes coincided with changes in taxonomic compositions—a shift from Gammaproteobacteria and Bacilli predominance before treatment to Clostridia and Bacteroidia predominance after treatment.

Figure 1: BA restoration of successfully-treated participants

Conclusion

In a trial of RBX2660 for rCDI, participant BA compositions significantly changed from before to after treatment, remained so for at least two years, and correlated with treatment outcome. The resulting predominance of secondary BAs coincided with microbiome compositional changes. Because secondary BA are thought to repress C. difficile colonization, these changes may partly explain how RBX2660 reduced CDI recurrence. Continued evaluation of RBX2660 for rCDI is underway.

Disclosures

Romeo Papazyan, PhD, Ferring Pharmaceuticals (Employee) Dana Walsh, PhD, Rebiotix Inc. (Employee) Steve Qi, PhD, Ferring Pharmaceuticals (Employee) Ken Blount, PhD, Rebiotix Inc. (Employee) Karthik Srinivasan, PhD, Ferring Pharmaceuticals (Employee) Bryan Fuchs, PhD, Ferring Pharmaceuticals (Employee)

RBX7455, a Non-frozen, Orally Administered Investigational Live Biotherapeutic, Is Safe, Effective, and Shifts Patients' Microbiomes in a Phase 1 Study for Recurrent Clostridioides difficile Infections

Background

Recurrent Clostridioides difficile infections (rCDI) are a global public health threat. To reduce rCDI, microbiota-restoring therapies are needed, particularly standardized, easy-to-administer formulations.

Methods

This phase I open-label trial assessed the safety, efficacy in preventing rCDI recurrence, and intestinal microbiome effects of RBX7455, a room temperature-stable, orally administered investigational live biotherapeutic. Adult participants with 1 or more prior episodes of rCDI received: 4 RBX7455 capsules twice daily for 4 days (group 1); 4 RBX7455 capsules twice daily for 2 days (group 2); or 2 RBX7455 capsules twice daily for 2 days (group 3). For all groups, the first dose was administered in clinic, with remaining doses self-administered at home. Adverse events were monitored during and for 6 months after treatment. Treatment success was defined as rCDI prevention through 8 weeks after treatment. Participants’ microbiome composition was assessed prior to and for 6 months after treatment.

Results

Nine of 10 group 1 patients (90%), 8 of 10 group 2 patients (80%), and 10 of 10 group 3 patients (100%) were recurrence-free at the 8-week endpoint with durability to 6 months. Seventy-five treatment-emergent adverse events were observed in 27 participants with no serious investigational product-related events. Prior to treatment, participants’ microbiomes were dissimilar from the RBX7455 composition with decreased Bacteroidia- and Clostridia-class bacteria, whereas after treatment, responders’ microbiomes showed increased Bacteroidia and Clostridia.

Conclusions

Three dosing regimens of RBX7455 were safe and effective at preventing rCDI. Responders’ microbiomes converged toward the composition of RBX7455. These results support its continued clinical evaluation.

Clinical Trials Registration

NCT02981316.

669. Twelve-Month Durability of Microbiota-Based Therapy RBX2660 for Prevention of Recurrent Clostridium difficile Infection

Background

Recurrent Clostridium difficile infections (rCDI) are a public health threat with insufficient treatment options at present. Two Phase 2 clinical studies have reported the efficacy of RBX2660, a standardized, stabilized microbiota-based drug, in preventing rCDI. For one of these trials, we report herein the durability of clinical response (lack of CDI recurrence) and microbiome restoration to 12 months after RBX2660 treatment.

Methods

Data were drawn from an interim analysis of a multicenter, open-label Phase 2 study in which participants with multi-recurrent rCDI received up to 2 doses of RBX2660 delivered via enema 7 days apart; this analysis includes data to 12 months after treatment, with follow-up ongoing. Efficacy was defined as the absence of CDI recurrence to 56 days after the last dose; and durability is defined as a continued lack of reported recurrence. Participant stool samples collected prior to and at 1, 7, 30, 60 days and 6 and 12 months after treatment were sequenced using a shallow shotgun method, with only treatment responders reported herein. Operational taxonomic unit (OTU) data were used to calculate relative abundance at the class level and Microbiome Health Indices.

Results

This study included 149 RBX2660-treated participants and 110 historical control patients, in the United States and Canada. As previously reported, the efficacy of RBX2660 in preventing rCDI (79.9%; 119/149) was higher than CDI-free rates in the historical control group (51.8%, 57/110; P < 0.001). Of 109 participants who had a 6-month follow-up, 97.2% (106/109) remained CDI-free, and no new CDI recurrences were reported at 12 months. Among treatment responders, the microbiome composition was restored after treatment to predominance by Bacteroidia- and Clostridia-class bacteria, and these compositions remained stable to 12 months after treatment among participants who provided samples.

Conclusion

RBX2660, a microbiota-based drug, was efficacious for preventing rCDI, with clinical and microbiome restoration durability to at least 12 months after treatment. The follow-up of efficacy, safety, and microbiome restoration are ongoing.

Disclosures

All authors: No reported disclosures.

670. VRE Clearance in Patients with Recurrent Clostridium difficile Infection Following Treatment with Microbiota-Based Drug RBX2660

Background

Vancomycin-resistant Enterococcus (VRE) infection is frequently associated with immunocompromised and critically ill patients. VRE carriers are at increased risk for infection due to VRE colonization and they pose a risk as a transmission source. VRE infection and Clostridium difficile infection (CDI) share common risk factors, including disruption of the intestinal microbiome. Thus, therapeutic approaches that decolonize VRE would be valuable. Herein, we report on stool VRE clearance in a cohort analysis from a Phase 2 open-label study of RBX2660, standardized microbiota-based drug, for recurrent CDI.

Methods

This prospective, multicenter, open-label Phase 2 study enrolled subjects with recurrent CDI. Participants received up to 2 doses of RBX2660 delivered via enema with doses 7 days apart. Patients were requested to voluntarily submit stool samples at baseline and at 7, 30 and 60 days, 6, 12, and 24 months after the last administration of RBX2660. Stool samples were tested for VRE using bile esculin azide agar with 6 µg/mL vancomycin and gram staining. Vancomycin resistance was confirmed via blood agar and etest.

Results

Stool samples were available for 143 patients. Twenty-one patients were VRE-positive at the first test (baseline or 7 day). Of the 19 VRE-positive patients that provided additional samples at later timepoints, 18 (94.7%) converted to negative as of the last available follow-up (30 or 60 days and 6, 12, or 24 months). The remaining patient remained positive at all follow-ups.

Conclusion

This cohort analysis of VRE-positive patients within an rCDI population provides additional support that microbiota-based formulations, such as RBX2660, may have additional benefit beyond reducing the recurrence of CDI. Additional study is needed to confirm the role of microbiome restoration on VRE clearance.

Disclosures

All authors: No reported disclosures

LB5. A Long-Time Coming: Final 2-year Analysis of Efficacy, Durability, and Microbiome Changes in a Controlled Open-Label Trial of Investigational Microbiota-Based Drug RBX2660 for Recurrent Clostridioides difficile Infections

Background

Recurrent Clostridioides difficile infection (rCDI) is an urgent public health threat associated with significant mortality and medical cost. Microbiota therapy is gaining acceptance as a strategy to reduce rCDI recurrence. We present the final 24-month analysis of clinical safety, efficacy, and microbiome restoration from a Phase 2 open-label trial of RBX2660 for prevention of CDI recurrence.

Methods

Participants with multi-recurrent CDI received <2 doses of RBX2660 delivered via enema 7 days apart in this multicenter, open-label Phase 2 study. Efficacy was defined as the absence of CDI recurrence through 56 days after the last dose and was compared with 8-week recurrence-free rates for a historical control cohort that received standard-of-care antibiotic therapy. Fisher exact test compared the proportion of treatment participants who were CDI-free by age and sex. Durability was defined as continued absence of CDI episodes beyond 8 weeks. Safety and durability assessments occurred at 3, 6, 12, and 24 months. Participant stool samples were collected prior to and for up to 720 days after treatment, and microbiome changes were assessed by shallow shotgun sequencing.

Results

The efficacy of RBX2660 to prevent rCDI at 8 weeks (78.9%; 112/142) was higher than the CDI-free rate in the historical control group (30.7%, 23/75; P < 0.0001). Age and sex did not impact efficacy. Among participants who achieved treatment success at 8 weeks and were evaluable for long-term durability (n = 95), 8 experienced a new CDI episode by the 24-month follow-up for an overall durability of 91.6%. The safety profile was consistent with previous reports for RBX2660. In total, 503 stool samples from 110 treatment responders were analyzed. Within 7 days of treatment, the relative abundance of Bacteroidia and Clostridia remained shifted higher than pre-treatment levels while Gammaproteobacteria and Bacilli declined sharply after treatment, and these changes persisted to at least 24 months.

Conclusion

RBX2660, a microbiota-based drug, was safe and efficacious for preventing rCDI with clinical durability to 24 months after treatment, independent of age or sex, and RBX2660 durability associated with durable microbiome shifts from pre-treatment to a healthier composition.

Disclosures

Robert Orenstein, DO, Rebiotix Inc. (Advisor or Review Panel member), Sarah Mische, PhD, Rebiotix Inc. (Employee), Ken Blount, PhD, Rebiotix Inc. (Employee), Lindy Bancke, PharmD, Rebiotix Inc. (Employee), Xin Su, MD, MSci, Rebiotix Inc. (Employee), Dana Walsh, PhD, Rebiotix Inc. (Employee), Adam Harvey, PhD, Rebiotix Inc. (Employee), Carlos Gonzalez, MS, Rebiotix Inc. (Consultant), Dale N. Gerding, MD, Rebiotix Inc. (Board Member).

1775. Microbiome-Based Classifiers Accurately Differentiate Infectious Diarrhea From Functional Gastrointestinal Disorders and Provide Population-Scale Confidence Measures of Fecal Microbiota Restoration in Recurrent C. DifficileInfection

Background

Fecal microbiota therapy is being actively pursued as treatment for recurrent C. difficile infection (rCDI), as well as for other GI disease indications associated with dysbiosis, for example, irritable bowel syndrome (IBS). RBX2660 is a microbiota-based drug designed to restore a healthier microbiome and has demonstrated clinical efficacy for preventing rCDI. Despite this and other treatment successes, our understanding of functional microbiota reconstitution at the population scale is still evolving, as is the ability to distinguish IBS from CDI recurrence. Herein we describe development of a Random Forest classifier for CDI diagnosis, and we evaluate microbiome restoration in participants of the Phase 2 trial of RBX2660.

Methods

Fecal 16S rDNA sequences from 2,129 subjects enrolled in diverse multi-center cohorts were analyzed (1,235 adults and 447 children with CDI, AAD, IBS, or controls). Technical variations due to different DNA extraction, primer region coverage, and sequencing platforms were addressed using closed-reference OTU picking with UCLUST. The RDP classifier and SILVA database assigned taxonomy for each OTU sequence. Stratified random sampling with 50 repeated tests of microbiota training sets was performed for supervised learning. Microbiota signatures of patients in the RBX2660 PUNCH CD2 trial were then assessed using classifiers built to predict CDI treatment outcomes and IBS misdiagnosis.

Results

Random Forest built the best classifiers accurately predicting 97.7% of CDI cases, and confidently distinguished CDI from IBS patients based on their microbiome signatures (figure). RBX2660 treatment significantly restored microbiota community composition in rCDI cases compared with placebo controls.

Conclusion

Random Forest classifiers built on a population-scale study of microbiota composition in patients with GI disease provide a highly accurate predictor of CDI cases versus potential IBS misdiagnosis in adults and children. RBX2660 significantly reduced disease classification scores in rCDI patients with a healthy-like microbiota reconstitution markedly accelerating after 30 days of treatment.

This study was funded by 1UO1 AI24290-01 and Rebiotix, Inc.

Disclosures

C. Jones, Rebiotix, Inc.: Employee, Salary. K. Blount, Rebiotix, Inc.: Employee, Salary. T. Savidge, Rebiotix: Grant Investigator, Research grant.

1966. Evaluating a Prototype Microbiome Health Index (MHI) as a Measure of Microbiome Restoration Using Data Derived From a Published Study of Fecal Microbiota Transplant (FMT) to Treat Recurrent Clostridium difficile Infections (rCDI)

Background

There are efforts to develop FDA-approved microbiota-based drugs to restore the microbiome, notably for recurrent Clostridium difficile infections (rCDI). Given the lack of established biomarkers for microbiome restoration, we are evaluating unidimensional Microbiome Health Indices (MHI™). We previously presented a prototype MHI for clinical trials of RBX2660—a standardized microbiota restoration therapy in Phase 3 clinical development. Herein we assessed MHI for a published study of fecal microbiota transplant (FMT) for treating rCDI.

Methods

The prototype MHI is based on the associations of Bacteroidia and Clostridia with colonization resistance, and Gammaproteobacteria and Bacilli with dysbiosis, and Receiver Operating Characteristic analysis of pooled RBX2660 trial data indicated that rCDI participants before treatment (baseline) are distinguished from the healthier RBX2660 profile with an odds ratio of 121 (AUC = 0.99, sensitivity = 0.96, specificity = 0.99, cutpoint = 8.2). MHI data for the published FMT cohort were calculated using publicly available data derived from pre- and post-treatment fecal samples (Khanna S, et al. Microbiome 2017 5:55), and this study included patients with or without a co-diagnosis of inflammatory bowel disease (IBD).

Results

At baseline, 92% of patients in the FMT cohort were below the MHI = 8.2 cutpoint, consistent with a rCDI diagnosis. Among FMT responders 7 days after treatment, 91% of patients had shifted to MHI>8.2, (P < 0.0001 compared with baseline). Likewise, a significant shift was observed from baseline to 30 days (P < 0.0001), with 83% having MHI > 8.2. There were insufficient patients to support a statistical comparison of IBD vs. no IBD, but MHIs trended lower at all time points among patients with IBD.

Conclusion

MHI parameters derived from RBX2660 trials were predictive of pre- and post-treatment states for a published cohort of FMT-treated rCDI patients, suggesting that this prototype MHI represents a useful dysbiosis measure beyond RBX2660 trials. Lower MHI among patients co-diagnosed with IBD suggests the potential utility of MHI beyond rCDI. Collectively our results continue to support the utility of MHI and its prospective evaluation in ongoing Phase 3 clinical trials.

Disclosures

K. Blount, Rebiotix, Inc.: Employee, Salary. C. Jones, Rebiotix, Inc.: Employee, Salary. E. Deych, Rebiotix, Inc.: Research Contractor, Consulting fee. B. Shannon, Rebiotix, Inc.: Research Contractor, Consulting fee.

1950. Prevention of Recurrent Clostridium difficile at Six Months Following Treatment With Microbiota-Based Therapy RBX2660: Durability Results From a Phase 2 Open-Label Study

Background

Methods

Results

Conclusion

Disclosures

Successful Response to Microbiota-Based Drug RBX2660 in Patients with Recurrent Clostridium Difficile Infection is Associated with More Pronounced Alterations in Microbiome Profile

Background

Recurrent Clostridium difficile infections (rCDI) are associated with decreased diversity and altered intestinal microbiome compared with healthy patients. RBX2660, a standardized microbiota-based drug, is designed to restore microbiome diversity and composition in patients’. The effect of RBX2660 on rCDI patient microbiomes was evaluated by comparing pre- and post-treatment samples from PUNCH CD 2—a randomized, double-blind, placebo-controlled study.

Methods

rCDIsubjects were randomized to receive blinded treatments of 2 doses of RBX2660 (Group A), 2 doses of placebo (Group B), or 1 dose each of RBX2660 and placebo (Group C), by enema 7 days apart. Subjects submitted stool samples at baseline, day 7, 30, and 60 after treatment. Stool samples from responders to RBX2660 treatment per protocol defined as the absence of CDI for 8 weeks after treatment were compared with non-responders.

Relative taxonomic abundances at the class level were determined using 16s rRNA sequencing analysis for 94 stool samples from 45 patients in Groups A and C. Relative abundance data were grouped longitudinally using Bray-Curtis dissimilarity index. Analyses were performed based on the Dirichlet-Multinomial distribution to compare group mean relative taxonomic abundances; Simpson and Shannon diversity indices were compared among groups longitudinally.

Results

Baseline patient microbiomes were similar across response groups. RBX2660 treatment shifted the relative microbiome densities with taxa-specific increase in Bacteroidia, Clostridia, and decrease in Gamma-proteobacteria abundance. A larger shift from baseline microbiome was seen in responders to RBX2600 compared with non-responders (Figure 1). Microbiome changes in responders were durable to 60 days. RBX2660 treatment increased Shannon and Simpson diversity at 7 days post-treatment in responders but not in non-responders (P &lt; 0.05).

Conclusion

RBX2660 treatment shifts patient intestinal microbiomes with greater alterations seen in those with a successful clinical outcome.

Funded by Rebiotix Inc., Roseville, MN.

Disclosures

S. Khanna, Rebiotix, Inc.: Scientific Advisor, Consulting fee; K. Blount, Rebiotix, Inc.: Employee, Salary; C. Jones, Rebiotix, Inc.: Employee, Salary; B. Shannon, Rebiotix, Inc.: Research Contractor, Consulting fee; S. Carter, Rebiotix, Inc.: Research Contractor, Consulting fee

How to build teams in the midst of change

In the process of reengineering, nurse managers were shifted to unit coordinator positions. Former managers now share responsibility for some bedside decisions with staff who previously turned to them for problem-solving. Some staff nurses interpreted the role change as an increased workload for them that included doing their manager's jobs. Managers were challenged to empower staff members who resisted this shift in roles.

Race and gender as components of the working self-concept

A sample of 78 U.S. students carried beepers for 1 week and reported in situ on their awareness of gender and race. The participants to whom gender and race were more important were more aware of those characteristics, and their awareness of gender and race was more variable across situations. Awareness was higher in public than in private settings; it was also higher during athletic than during academic involvement. The White participants were more aware of race when they were in the racial minority; the non-White participants were more aware of race when they were in the racial majority. All the participants were more aware of gender when they were in the gender minority.

Advanced practice nursing in pediatric acute care

This article explores various aspects of pediatric advanced practice nursing. After outlining the history and current practice of this field, use patterns of pediatric advanced practice nurses in acute care are discussed. Other topics covered include certification, economic issues, and visions for the future.

alpha-Conotoxin GI produces tetanic fade at the rat neuromuscular junction

The ability of the marine snail toxin, alpha-conotoxin GI, to produce blockade of singly evoked twitches and to produce tetanic and train-of-four fade has been determined in the isolated rat hemidiaphragm preparation. Results were compared to those obtained with a reversible (vecuronium) and an irreversible (alpha-bungarotoxin) nicotinic acetylcholine antagonist and have been interpreted in terms of relative effects on post- and prejunctional nicotinic acetylcholine receptors at the neuromuscular junction. alpha-Conotoxin GI (0.5-2 microM) produced a concentration-dependent, readily reversible, decrease in the peak amplitude of single twitches and 50 Hz tetani, and an increase in tetanic and train-of-four fade. alpha-Conotoxin GI was consistently 2-3-fold more potent than vecuronium with respect to all of the measured tension parameters. Both alpha-conotoxin GI and vecuronium were approximately 2-fold more potent in producing tetanic fade and in blocking tetanic contractions than in blocking single twitches. In contrast to both alpha-conotoxin GI and vecuronium, alpha-bungarotoxin (0.13 microM) reduced the peak amplitude of both single twitches and 50 Hz tetani to the same extent without the appearance of a large degree of tetanic or train-of-four fade. Based on a comparison of the in vitro time course of neuromuscular block and of the relative effects of vecuronium, alpha-conotoxin GI and alpha-bungarotoxin on twitches, tetani and trains-of-four, we conclude that alpha-conotoxin GI has both pre- and postjunctional activity at the neuromuscular junction. In this respect, alpha-conotoxin GI resembles the clinically used competitive neuromuscular blocking drugs rather than the irreversible snake alpha-neurotoxins.