Use of ribaxamase (SYN-004), a ß-lactamase, to prevent Clostridium difficile infection in ß-lactam-treated patients: a double-blind, phase 2b, randomised placebo-controlled trial.

BACKGROUND: Infections with Clostridium difficile are a health threat, yet no products are currently licensed for prevention of primary C difficile infections. Intravenous ß-lactam antibiotics are considered to confer a high risk of C difficile infection because of their biliary excretion into the gastrointestinal tract and disruption of the gut microbiome. ribaxamase (SYN-004) is an orally administered ß-lactamase that was designed to be given with intravenous ß-lactam antibiotics to degrade excess antibiotics in the upper gastrointestinal tract before they disrupt the gut microbiome and lead to C difficile infection. We therefore aimed to determine whether administration of ribaxamase could prevent C difficile infection in patients being treated with intravenous ceftriaxone for a lower respiratory tract infection, thereby supporting continued clinical development. METHODS: In this parallel-group, double-blind, multicentre, phase 2b, randomised placebo-controlled trial, we recruited patients who had been admitted to a hospital with a lower respiratory tract infection with a pneumonia index score of 90-130 and who were expected to be treated with ceftriaxone for at least 5 days. Patients were recruited from 54 clinical sites in the USA, Canada, Bulgaria, Hungary, Poland, Romania, and Serbia. We randomly assigned patients older than 50 years to groups (1:1) in blocks of four by use of an interactive web portal; these groups were assigned to receive either 150 mg ribaxamase or placebo four times per day during, and for 72 h after, treatment with ceftriaxone. All patients, clinical investigators, study staff, and sponsor personnel were masked to the study drug assignments. The primary endpoint was the incidence of C difficile infection, as diagnosed by the local laboratory, in patients who received at least one treatment dose, and this outcome was assessed during treatment and for 4 weeks after treatment. This study is registered with ClinicalTrials.gov, number NCT02563106. FINDINGS: Between Nov 16, 2015, and Nov 10, 2016, we screened 433 patients for inclusion in the study. Of these patients, 20 (5%) patients were excluded from the study (16 [4%] patients did not meet inclusion criteria; four [1%] patients because of dosing restrictions). We enrolled and randomly assigned 413 patients to groups, of whom 207 patients were assigned to receive ceftriaxone plus ribaxamase and 206 patients were assigned to receive ceftriaxone plus placebo. However, one (<1%) patient in the ribaxamase group withdrew consent and was not treated with ribaxamase. During the study and within the 4 weeks after antibiotic treatment, two (1·0%) patients in the ribaxamase group and seven (3·4%) patients in the placebo group were diagnosed with an infection with C difficile (risk reduction 2·4%, 95% CI -0·6 to 5·9; one-sided p=0·045). Adverse events were similar between groups but more deaths were reported in the ribaxamase group (11 deaths vs five deaths in the placebo group). This disparity was due to the higher incidence of deaths attributed to cardiac-associated causes in the ribaxamase group (six deaths vs one death in the placebo group). INTERPRETATION: In patients treated with intravenous ceftriaxone for lower respiratory tract infections, oral ribaxamase reduced the incidence of C difficile infections compared with placebo. The imbalance in deaths between the groups appeared to be related to the underlying health of the patients. Ribaxamase has the potential to prevent C difficile infection in patients treated with intravenous ß-lactam antibiotics, and our findings support continued clinical development of ribaxamase to prevent C difficile infection. FUNDING: Synthetic Biologics.

Development of a Modified-Release Formulation of Lovastatin Targeted to Intestinal Methanogens Implicated in Irritable Bowel Syndrome With Constipation.

There is growing evidence that methane production, predominantly by Methanobrevibacter smithii, in the intestines is a cause of constipation, pain, and bloating in irritable bowel syndrome with constipation (IBS-C). M smithii resides primarily in the large intestine but can also colonize the small intestine. In vitro studies found that the prodrug lactone form of lovastatin, found in cholesterol-lowering drugs, inhibited methane production in stool samples from patients with IBS-C. However, the cholesterol-lowering lovastatin ß-hydroxyacid was ineffective at inhibiting methane production in this system. A considerable amount of lovastatin is converted to hydroxyacid in the stomach and is absorbed. It was hypothesized that galenic innovations could protect lovastatin from the stomach and allow release in 2 strategic locations, the duodenum and the ileocecal region, to reach M smithii. The desired release profile was achieved by developing an oral dosage form containing lovastatin and coated with 2 different enteric polymers that enabled a pH-dependent "dual pulse" drug release. Combinations of the 2 coated tablets were encapsulated together to deliver the desired amount of lovastatin to the targeted intestinal locations. The capsules have been tested in vitro and in vivo and show promise in treating IBS-C.

The Oral ß-Lactamase SYN-004 (Ribaxamase) Degrades Ceftriaxone Excreted into the Intestine in Phase 2a Clinical Studies.

SYN-004 (ribaxamase) is a ß-lactamase designed to be orally administered concurrently with intravenous ß-lactam antibiotics, including most penicillins and cephalosporins. Ribaxamase's anticipated mechanism of action is to degrade excess ß-lactam antibiotic that is excreted into the small intestine. This enzymatic inactivation of excreted antibiotic is expected to protect the gut microbiome from disruption and thus prevent undesirable side effects, including secondary infections such as Clostridium difficile infections, as well as other antibiotic-associated diarrheas. In phase 1 clinical studies, ribaxamase was well tolerated compared to a placebo group and displayed negligible systemic absorption. The two phase 2a clinical studies described here were performed to confirm the mechanism of action of ribaxamase, degradation of ß-lactam antibiotics in the human intestine, and were therefore conducted in subjects with functioning ileostomies to allow serial sampling of their intestinal chyme. Ribaxamase fully degraded ceftriaxone to below the level of quantitation in the intestines of all subjects in both studies. Coadministration of oral ribaxamase with intravenous ceftriaxone was also well tolerated, and the plasma pharmacokinetics of ceftriaxone were unchanged by ribaxamase administration. Since ribaxamase is formulated as a pH-dependent, delayed-release formulation, the activity of ribaxamase in the presence of the proton pump inhibitor esomeprazole was examined in the second study; coadministration of these drugs did not adversely affect ribaxamase's ability to degrade ceftriaxone excreted into the intestine. These studies have confirmed the in vivo mechanism of action of ribaxamase, degradation of ß-lactam antibiotics in the human intestine (registered at ClinicalTrials.gov under NCT02419001 and NCT02473640).

Tolerability and Pharmacokinetics of SYN-004, an Orally Administered ß-Lactamase for the Prevention of Clostridium difficile-Associated Disease and Antibiotic-Associated Diarrhea, in Two Phase 1 Studies.

BACKGROUND: SYN-004 is an orally administered ß-lactamase enzyme, designed to be given concurrently with certain intravenous ß-lactam antibiotics like cephalosporins. SYN-004 is intended to degrade residual antibiotics excreted into the intestine as a result of hepatobiliary excretion and to prevent the disruption of the gut microbiome by these excess antibiotics. Preserving the gut microbiome is expected to prevent secondary infections by pathogens like Clostridium difficile and protect against other antibiotic-associated diarrheas. METHODS: Two, randomized, double blind, placebo-controlled Phase 1 clinical studies were conducted in normal healthy adult volunteers to assess the tolerability and systemic absorption of single and multiple doses of SYN-004. A single-ascending dose study investigated single oral doses of 75-750 mg SYN-004 and was conducted in 40 subjects (five cohorts of six active and two placebo subjects). A multiple-ascending dose study investigated doses of 75-300 mg SYN-004, administered every 6 h for 7 days and was conducted in 24 subjects (three cohorts of six active and two placebo subjects). The safety and tolerability of SYN-004 was assessed and serial plasma and serum samples were collected to assess the pharmacokinetics and potential immunogenicity of SYN-004. RESULTS: Minimal and mild adverse events were reported in ~30 % of the subjects who received active drug and placebo and no antidrug antibodies were detected in any subject. Analysis of serial plasma samples demonstrated negligible systemic bioavailability of SYN-004 with most plasma concentrations being below the lower limit of quantitation (0.8 ng/mL) for the assay. SYN-004 was well tolerated in the 48 subjects who received active drug, and adverse events in those subjects were comparable to the 16 subjects who received placebo, up to the maximum doses administered in each study. CONCLUSION: SYN-004 was well tolerated up to a single oral dose of 750 mg and multiple doses of 300 mg every 6 h for 7 days. The pharmacokinetic results support that SYN-004 remained localized in the intestine.