Ciraparantag reverses the anticoagulant activity of apixaban and rivaroxaban in healthy elderly subjects.

AIMS: Ciraparantag is a reversal agent for anticoagulants including direct oral anticoagulants. The aim was to evaluate the efficacy and safety of ciraparantag to reverse anticoagulation induced by apixaban or rivaroxaban in healthy elderly adults. METHODS AND RESULTS: Two randomized, placebo-controlled, dose-ranging trials conducted in healthy subjects aged 50-75 years. Subjects received apixaban (Study 1) 10 mg orally twice daily for 3.5 days or rivaroxaban (Study 2) 20 mg orally once daily for 3 days. At steady-state anticoagulation subjects were randomized 3:1 to a single intravenous dose of ciraparantag (Study 1: 30, 60, or 120 mg; Study 2: 30, 60, 120, or 180 mg) or placebo. Efficacy was based on correction of the whole blood clotting time (WBCT) at multiple timepoints over 24 h. Subjects and technicians performing WBCT testing were blinded to treatment. Complete reversal of WBCT within 1 h post-dose and sustained through 5 h (apixaban) or 6 h (rivaroxaban) was dose related and observed with apixaban in 67%, 100%, 100%, and 17% of subjects receiving ciraparantag 30 mg, 60 mg, 120 mg, or placebo, respectively; and with rivaroxaban in 58%, 75%, 67%, 100%, and 13% of subjects receiving ciraparantag 30 mg, 60 mg, 120 mg, 180 mg, or placebo, respectively. Adverse events related to ciraparantag were mild, transient hot flashes or flushing. CONCLUSIONS: Ciraparantag provides a dose-related reversal of anticoagulation induced by steady-state dosing of apixaban or rivaroxaban. Sustained reversal was achieved with 60 mg ciraparantag for apixaban and 180 mg ciraparantag for rivaroxaban. All doses of ciraparantag were well tolerated.

Ciraparantag, an anticoagulant reversal drug: mechanism of action, pharmacokinetics, and reversal of anticoagulants.

Ciraparantag, an anticoagulant reversal agent, is a small molecule specifically designed to bind noncovalently by charge-charge interaction to unfractionated heparin and low-molecular-weight heparin. It shows binding characteristics that are similar to those of direct oral anticoagulants (DOACs). A dynamic light-scattering methodology was used to demonstrate ciraparantag's binding to the heparins and DOACs and its lack of binding to a variety of proteins including coagulation factors and commonly used drugs. Ciraparantag reaches maximum concentration within minutes after IV administration with a half-life of 12 to 19 minutes. It is primarily hydrolyzed by serum peptidases into 2 metabolites, neither of which has substantial activity. Ciraparantag and its metabolites are recovered almost entirely in the urine. In animal models of bleeding (rat tail transection and liver laceration), a single IV dose of ciraparantag given at peak concentrations of the anticoagulant, but before the bleeding injury, significantly reduced the blood loss. Ciraparantag, given after the bleeding injury, also significantly reduced blood loss. It appears to have substantial ability to reduce blood loss in animal models in which a variety of anticoagulants are used and has potential as a useful DOAC reversal agent.

An Open-Label Study of the Impact of Hepatic Impairment on the Pharmacokinetics and Safety of Single Oral and Intravenous Doses of Omadacycline.

Omadacycline is a once-daily oral or intravenous (i.v.) aminomethylcycline antibiotic approved in the United States for the treatment of community-acquired bacterial pneumonia (CABP) and acute bacterial skin and skin structure infections (ABSSSI) in adults. Omadacycline pharmacokinetics were characterized in 18 patients with hepatic impairment and 12 matched healthy subjects. Patients with hepatic impairment received i.v. omadacycline at 100 mg (mild hepatic impairment) or 50 mg (moderate and severe hepatic impairment) and oral omadacycline at 300 mg (mild hepatic impairment) or 150 mg (moderate hepatic impairment); oral omadacycline was not evaluated in those with severe hepatic impairment. Safety monitoring included the collection of adverse events (AEs), performance of laboratory tests, determination of vital signs, and performance of electrocardiograms. Omadacycline exposures were similar in patients with hepatic impairment and healthy subjects following i.v. or oral administration, with the geometric mean ratios for the area under the concentration-time curve and the maximum drug concentration ranging from 0.79 to 1.42. Omadacycline was safe and well tolerated. Overall, 13/30 (43.3%) participants experienced an AE; those occurring in more than 1 participant included headache (13.3%), nausea (6.7%), infusion-site pain (6.7%), contusion (6.7%), and dizziness (6.7%), with no differences based on the degree of hepatic impairment or the route of administration. Asymptomatic increases in heart rate were observed; none was considered an AE. These findings suggest that no omadacycline dose adjustment is warranted in patients with hepatic impairment.

Maribavir for Preemptive Treatment of Cytomegalovirus Reactivation.

BACKGROUND: Maribavir is a benzimidazole riboside with activity against cytomegalovirus (CMV). The safety and efficacy of maribavir for preemptive treatment of CMV infection in transplant recipients is not known. METHODS: In a phase 2, open-label, maribavir dose-blinded trial, recipients of hematopoietic-cell or solid-organ transplants (≥18 years of age, with CMV reactivation [1000 to 100,000 DNA copies per milliliter]) were randomly assigned to receive maribavir at a dose of 400, 800, or 1200 mg twice daily or the standard dose of valganciclovir for no more than 12 weeks. The primary efficacy end point was the percentage of patients with a response to treatment, defined as confirmed undetectable CMV DNA in plasma, within 3 weeks and 6 weeks after the start of treatment. The primary safety end point was the incidence of adverse events that occurred or worsened during treatment. RESULTS: Of the 161 patients who underwent randomization, 159 received treatment, and 156 had postbaseline data available - 117 in the maribavir group and 39 in the valganciclovir group. The percentage of patients with postbaseline data available who had a response to treatment within 3 weeks was 62% among those who received maribavir and 56% among those who received valganciclovir. Within 6 weeks, 79% and 67% of patients, respectively, had a response (risk ratio, 1.20; 95% confidence interval, 0.95 to 1.51). The percentages of patients with a response to treatment were similar among the maribavir dose groups. Two patients who had a response to treatment had a recurrence of CMV infection within 6 weeks after starting maribavir at a dose of 800 mg twice daily; T409M resistance mutations in CMV UL97 protein kinase developed in both patients. The incidence of serious adverse events that occurred or worsened during treatment was higher in the maribavir group than in the valganciclovir group (52 of 119 patients [44%] vs. 13 of 40 [32%]). A greater percentage of patients in the maribavir group discontinued the trial medication because of an adverse event (27 of 119 [23%] vs. 5 of 40 [12%]). A higher incidence of gastrointestinal adverse events was reported with maribavir, and a higher incidence of neutropenia was reported with valganciclovir. CONCLUSIONS: Maribavir at a dose of at least 400 mg twice daily had efficacy similar to that of valganciclovir for clearing CMV viremia among recipients of hematopoietic-cell or solid-organ transplants. A higher incidence of gastrointestinal adverse events - notably dysgeusia - and a lower incidence of neutropenia were found in the maribavir group. (Funded by ViroPharma/Shire Development; EudraCT number, 2010-024247-32.).

Omadacycline for Acute Bacterial Skin and Skin-Structure Infections.

BACKGROUND: Acute bacterial skin and skin-structure infections are associated with substantial morbidity and health care costs. Omadacycline, an aminomethylcycline antibiotic that can be administered once daily either orally or intravenously, is active against pathogens that commonly cause such infections, including antibiotic-resistant strains. METHODS: In this double-blind trial, we randomly assigned adults with acute bacterial skin and skin-structure infections (in a 1:1 ratio) to receive omadacycline (100 mg given intravenously every 12 hours for two doses, then 100 mg given intravenously every 24 hours) or linezolid (600 mg given intravenously every 12 hours). A transition to oral omadacycline (300 mg every 24 hours) or oral linezolid (600 mg every 12 hours) was allowed after 3 days; the total treatment duration was 7 to 14 days. The primary end point was an early clinical response at 48 to 72 hours, defined as survival with a reduction in lesion size of at least 20% without rescue antibacterial therapy. A secondary end point was an investigator-assessed clinical response at the post-treatment evaluation 7 to 14 days after the last dose, with clinical response defined as survival with resolution or improvement in signs or symptoms of infection to the extent that further antibacterial therapy was unnecessary. For both end points, the noninferiority margin was 10 percentage points. RESULTS: In the modified intention-to-treat population, omadacycline (316 patients) was noninferior to linezolid (311 patients) with respect to early clinical response (rate of response, 84.8% and 85.5%, respectively; difference, -0.7 percentage points; 95% confidence interval [CI], -6.3 to 4.9). Omadacycline also was noninferior to linezolid with respect to investigator-assessed clinical response at the post-treatment evaluation in the modified intention-to-treat population (rate of response, 86.1% and 83.6%, respectively; difference, 2.5 percentage points; 95% CI, -3.2 to 8.2) and in the clinical per-protocol population (96.3% and 93.5%, respectively; difference, 2.8 percentage points; 95% CI, -1.0 to 6.9). In both groups, the efficacy of the trial drug was similar for methicillin-susceptible and methicillin-resistant Staphylococcus aureus infections. Adverse events were reported in 48.3% of the patients in the omadacycline group and in 45.7% of those in the linezolid group; the most frequent adverse events in both groups were gastrointestinal (in 18.0% and 15.8% of the patients in the respective groups). CONCLUSIONS: Omadacycline was noninferior to linezolid for the treatment of acute bacterial skin and skin-structure infections and had a similar safety profile. (Funded by Paratek Pharmaceuticals; OASIS-1 ClinicalTrials.gov number, NCT02378480 .).

Maribavir for Refractory or Resistant Cytomegalovirus Infections in Hematopoietic-cell or Solid-organ Transplant Recipients: A Randomized, Dose-ranging, Double-blind, Phase 2 Study.

BACKGROUND: Cytomegalovirus (CMV) infections that are refractory or resistant (RR) to available antivirals ([val]ganciclovir, foscarnet, cidofovir) are associated with higher mortality in transplant patients. Maribavir is active against RR CMV strains. METHODS: Hematopoietic-cell or solid-organ transplant recipients ≥12 years old with RR CMV infections and plasma CMV deoxyribonucleic acid (DNA) ≥1000 copies/mL were randomized (1:1:1) to twice-daily dose-blinded maribavir 400, 800, or 1200 mg for up to 24 weeks. The primary efficacy endpoint was the proportion of patients with confirmed undetectable plasma CMV DNA within 6 weeks of treatment. Safety analyses included the frequency and severity of treatment-emergent adverse events (TEAEs). RESULTS: From July 2012 to December 2014, 120 patients were randomized and treated (40 per dose group): 80/120 (67%) patients achieved undetectable CMV DNA within 6 weeks of treatment (95% confidence interval, 57-75%), with rates of 70%, 63%, and 68%, respectively, for maribavir 400, 800, and 1200 mg twice daily. Recurrent on-treatment CMV infections occurred in 25 patients; 13 developed mutations conferring maribavir resistance. Maribavir was discontinued due to adverse events in 41/120 (34%) patients, and 17/41 discontinued due to CMV infections. During the study, 32 (27%) patients died, 4 due to CMV disease. Dysgeusia was the most common TEAE (78/120; 65%) and led to maribavir discontinuation in 1 patient. Absolute neutrophil counts <1000/µL were noted in 12/106 (11%) evaluable patients, with rates similar across doses. CONCLUSIONS: Maribavir ≥400 mg twice daily was active against RR CMV infections in transplant recipients; no new safety signals were identified. CLINICAL TRIALS REGISTRATION: NCT01611974.

Safety and Pharmacokinetics of the Aminomethylcycline Antibiotic Omadacycline Administered to Healthy Subjects in Oral Multiple-Dose Regimens.

Omadacycline, a first-in-class aminomethylcycline antibiotic, is related to tetracyclines but is structurally modified to circumvent mechanisms of resistance to tetracyclines. Omadacycline demonstrates potent activity against a broad range of pathogens, including drug-resistant strains, and is in late-stage development for treatment of acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia. Previous studies support an intravenous-to-oral transition regimen with 300-mg once-daily oral dosing. This phase 1 study investigated the pharmacokinetics and safety/tolerability of multiple oral omadacycline doses higher than 300 mg. Using a 3-period crossover design, healthy adults were randomized to receive oral omadacycline at 300, 450, and 600 mg in variable sequence (n = 26) or placebo (n = 7) once daily for 5 consecutive days per period. In plasma, omadacycline maximum concentration and total exposure increased with increasing dose but were less than dose proportional. The kinetics of omadacycline plasma accumulation were similar between dose levels; exposure on day 5 was ∼50% higher than that on day 1. Omadacycline plasma concentrations on day 1 of 450-mg dosing were similar to those on day 5 of 300-mg dosing. All doses were generally well tolerated, but the 600-mg dose was associated with more gastrointestinal adverse events.

Pharmacokinetics and Safety of Omadacycline in Subjects with Impaired Renal Function.

Many antibiotics require dose adjustments in patients with renal impairment and/or in those undergoing hemodialysis. Omadacycline, the first aminomethylcycline antibiotic in late-stage clinical development, displays activity against a broad spectrum of bacterial pathogens, including drug-resistant strains. Data from completed phase 3 studies of omadacycline for the treatment of acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP) showed intravenous (i.v.) to once-daily oral omadacycline to be clinically effective and well tolerated. To determine if the dosing of omadacycline should be adjusted in patients with impaired renal function, a phase 1 study examining the pharmacokinetics (PK) and safety of i.v. omadacycline (100 mg) was conducted in subjects with end-stage renal disease (ESRD) on stable hemodialysis (n = 8) and in matched healthy subjects (n = 8). i.v. administration of omadacycline produced similar plasma concentration-time profiles in subjects with ESRD and healthy subjects. Further, in subjects with ESRD, similar values of the PK parameters were observed when omadacycline was administered i.v. after or before dialysis. The mean area under the concentration-time curve from time zero extrapolated to infinity in plasma was 10.30 µg · h/ml when omadacycline was administered to ESRD subjects after dialysis, 10.20 µg · h/ml when omadacycline was administered to ESRD subjects before dialysis, and 9.76 µg · h/ml when omadacycline was administered to healthy subjects. The mean maximum observed concentration of omadacycline in plasma in ESRD subjects was 1.88 µg/ml when it was administered after dialysis and 2.33 µg/ml when it was administered before dialysis, and in healthy subjects it was 1.92 µg/ml. The 100-mg i.v. dose of omadacycline was generally safe and well tolerated in both ESRD and healthy subjects. This study demonstrates that no dose adjustment is necessary for omadacycline in patients with impaired renal function or on days when patients are receiving hemodialysis.

Comparison of Omadacycline and Tigecycline Pharmacokinetics in the Plasma, Epithelial Lining Fluid, and Alveolar Cells of Healthy Adult Subjects.

The steady-state concentrations of omadacycline and tigecycline in the plasma, epithelial lining fluid (ELF), and alveolar cells (AC) of 58 healthy adult subjects were obtained. Subjects were administered either omadacycline at 100 mg intravenously (i.v.) every 12 h for two doses followed by 100 mg i.v. every 24 h for three doses or tigecycline at an initial dose of 100 mg i.v. followed by 50 mg i.v. every 12 h for six doses. A bronchoscopy and bronchoalveolar lavage were performed once in each subject following the start of the fifth dose of omadacycline at 0.5, 1, 2, 4, 8, 12, or 24 h and after the start of the seventh dose of tigecycline at 2, 4, 6, or 12 h. The value of the area under the concentration-time curve (AUC) from time zero to 24 h postdosing (AUC0-24) (based on mean concentrations) in ELF and the ratio of the ELF to total plasma omadacycline concentration based on AUC0-24 values were 17.23 mg · h/liter and 1.47, respectively. The AUC0-24 value in AC was 302.46 mg · h/liter, and the ratio of the AC to total plasma omadacycline concentration was 25.8. In comparison, the values of the AUC from time zero to 12 h postdosing (AUC0-12) based on the mean concentrations of tigecycline in ELF and AC were 3.16 and 38.50 mg · h/liter, respectively. The ratio of the ELF and AC to total plasma concentrations of tigecycline based on AUC0-12 values were 1.71 and 20.8, respectively. The pharmacokinetic advantages of higher and sustained concentrations of omadacycline compared to those of tigecycline in plasma, ELF, and AC suggest that omadacycline is a promising antibacterial agent for the treatment of lower respiratory tract bacterial infections caused by susceptible pathogens.

Clinical disposition, metabolism and in vitro drug-drug interaction properties of omadacycline.

1. Absorption, distribution, metabolism, transport and elimination properties of omadacycline, an aminomethylcycline antibiotic, were investigated in vitro and in a study in healthy male subjects. 2. Omadacycline was metabolically stable in human liver microsomes and hepatocytes and did not inhibit or induce any of the nine cytochrome P450 or five transporters tested. Omadacycline was a substrate of P-glycoprotein, but not of the other transporters. 3. Omadacycline metabolic stability was confirmed in six healthy male subjects who received a single 300 mg oral dose of [14C]-omadacycline (36.6 µCi). Absorption was rapid with peak radioactivity (∼610 ngEq/mL) between 1-4 h in plasma or blood. The AUClast of plasma radioactivity (only quantifiable to 8 h due to low radioactivity) was 3096 ngEq h/mL and apparent terminal half-life was 11.1 h. Unchanged omadacycline reached peak plasma concentrations (∼563 ng/mL) between 1-4 h. Apparent plasma half-life was 17.6 h with biphasic elimination. Plasma exposure (AUCinf) averaged 9418 ng h/mL, with high clearance (CL/F, 32.8 L/h) and volume of distribution (Vz/F 828 L). No plasma metabolites were observed. 4. Radioactivity recovery of the administered dose in excreta was complete (>95%); renal and fecal elimination were 14.4% and 81.1%, respectively. No metabolites were observed in urine or feces, only the omadacycline C4-epimer.

Effect of Food on the Bioavailability of Omadacycline in Healthy Participants.

Omadacycline is a first-in-class aminomethylcycline antibiotic being evaluated in phase 3 studies as oral and intravenous monotherapy for bacterial infections. This was a phase 1, randomized, open-label, 4-period, crossover study that evaluated the effect of food consumption on the bioavailability of omadacycline. Healthy participant were randomized to 1 of 4 sequences, which included the following predose conditions in different orders (A) ≥6-hour fast, (B) high-fat, nondairy meal 4 hours before dosing, (C) high-fat, nondairy meal 2 hours before dosing, and (D) high-fat meal containing dairy 2 hours before dosing. Participants received a single 300-mg oral dose of omadacycline during each treatment period; periods were separated by ≥5 days. Blood samples for pharmacokinetic (PK) analysis were collected over 24 hours after each dose, and safety assessments were performed during each treatment period. Least-squares mean and 90% confidence intervals were compared for fed state vs fasted state. Thirty-one participants were included in the PK analysis. Fasted AUC0-∞ , AUC0-t , and AUC0-24 were 10.2, 7.2, and 7.2 µg·h/mL, respectively, and Cmax was 0.6 µg/mL. Compared with a fasted dose, bioavailability was reduced by 15% to 17% by a nondairy meal 4 hours before dosing, 40% to 42% by a nondairy meal 2 hours before dosing, and 59% to 63% for a dairy meal 2 hours before dosing. Two participants experienced adverse events (mild nausea, mild somnolence). A 300-mg oral dose of omadacycline administered within 2 to 4 hours after food had reduced bioavailability compared with the fasted state. Oral omadacycline should be administered in a fasted state.

Pharmacokinetics, Distribution, Metabolism, and Excretion of Omadacycline following a Single Intravenous or Oral Dose of 14C-Omadacycline in Rats.

The absorption, distribution, metabolism, and excretion (ADME) of omadacycline, a first-in-class aminomethylcycline antibiotic with a broad spectrum of activity against Gram-positive, Gram-negative, anaerobic, and atypical bacteria, were evaluated in rats. Tissue distribution was investigated by quantitative whole-body autoradiography in male Long-Evans Hooded (LEH) rats. Following an intravenous (i.v.) dose of 5 mg/kg of body weight, radioactivity widely and rapidly distributed into most tissues. The highest tissue-to-blood concentration ratios (t/b) were observed in bone mineral, thyroid gland, and Harderian gland at 24 h post-i.v. dose. There was no evidence of stable accumulation in uveal tract tissue, suggesting the absence of a stable binding interaction with melanin. Following a 90 mg/kg oral dose in LEH rats, the highest t/b were observed in bone mineral, Harderian gland, liver, spleen, and salivary gland. The plasma protein binding levels were 26% in the rat and 15% to 21% in other species. Omadacycline plasma clearance was 1.2 liters/h/kg, and its half-life was 4.6 h; the steady-state volume of distribution (Vss) was 6.89 liters/kg. Major circulating components in plasma were intact omadacycline and its epimer. Consistent with observations in human, approximately 80% of the dose was excreted into the feces as unchanged omadacycline after i.v. administration. Fecal excretion was primarily the result of biliary excretion (∼40%) and direct gastrointestinal secretion (∼30%). However, urinary excretion (∼30%) was equally prominent after i.v. dosing.

Randomized, Open-Label Study of the Pharmacokinetics and Safety of Oral and Intravenous Administration of Omadacycline to Healthy Subjects.

Omadacycline is a first-in-class aminomethylcycline antibiotic with microbiological activity against Gram-positive and Gram-negative aerobes and anaerobes and atypical bacteria that is being developed for the treatment of acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP). The bioavailability of a phase 3 tablet formulation relative to that obtained via intravenous (i.v.) administration (and of other oral formulations relative to that of the phase 3 tablet) was investigated in an open-label, randomized, four-period, crossover study with healthy subjects age 18 to 50 years. Subjects received omadacycline at 100 mg i.v., 300 mg orally as two different tablet formulations with different dissolution profiles, and 300 mg as an oral solution. Plasma omadacycline concentrations were determined using a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Twenty of 24 subjects completed all treatment periods. The two tablet formulations produced equivalent total exposures. The phase 3 tablet produced an exposure equivalent to that of the 100-mg i.v. dose, with a geometric mean ratio (90% confidence intervals [CI]) for area under the concentration-time curve from 0 h to infinity [AUC∞]) of 1.00 (0.93, 1.07). The absolute bioavailability of the tablets was approximately 34.5%. Intersubject variability was consistent among the oral formulations (∼20 to 25%). Single oral and i.v. doses of omadacycline were well tolerated; three subjects experienced mild adverse events (dizziness, nausea, and vomiting) that resolved without intervention. A 300-mg dose of the tablet formulation of omadacycline intended for use in phase 3 studies produced a total exposure equivalent to that of a 100-mg i.v. dose.

Omadacycline: development of a novel aminomethylcycline antibiotic for treating drug-resistant bacterial infections.

Omadacycline is a first-in-class aminomethylcycline antibiotic that circumvents common tetracycline resistance mechanisms. In vitro omadacycline has potent activity against Gram-positive aerobic bacteria including methicillin-resistant Staphylococcus aureus, penicillin-resistant and multidrug-resistant Streptococcus pneumoniae, and vancomycin-resistant Enterococcus spp. It is also active against common Gram-negative aerobes, some anaerobes and atypical bacteria including Legionella spp. and Chlamydia spp. Ongoing Phase III clinical trials with omadacycline are investigating once daily doses of 100 mg intravenously followed by once-daily doses of 300 mg orally for the treatment of acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia. This paper provides an overview of the microbiology, nonclinical evaluations, clinical pharmacology and initial clinical experience with omadacycline.

Discovery, pharmacology, and clinical profile of omadacycline, a novel aminomethylcycline antibiotic.

Omadacycline is novel, aminomethyl tetracycline antibiotic being developed for oral and intravenous (IV) administration for the treatment of community-acquired bacterial infections. Omadacycline is characterized by an aminomethyl substituent at the C9 position of the core 6-member ring. Modifications at this position result in an improved spectrum of antimicrobial activity by overcoming resistance known to affect older generation tetracyclines via ribosomal protection proteins and efflux pump mechanisms. In vitro, omadacycline has activity against Gram-positive and Gram-negative aerobes, anaerobes, and atypical pathogens including Legionella and Chlamydia spp. Omadacycline offers once daily oral and IV dosing and a clinical tolerability and safety profile that compares favorably with contemporary antibiotics used across serious community-acquired infections where resistance has rendered many less effective. In studies in patients with complicated skin and skin structure infections, including those with MRSA infections, omadacycline exhibited an efficacy and tolerability profile that was comparable to linezolid. Ongoing and planned clinical studies are evaluating omadacycline as monotherapy for treating serious community-acquired bacterial infections including Acute Bacterial Skin and Skin Structure Infections (ABSSSI) and Community-Acquired Bacterial Pneumonia (CABP). This review provides an overview of the discovery, microbiology, nonclinical data, and available clinical safety and efficacy data for omadacycline, with reference to other contemporary tetracycline-derived antibiotics.

In Vitro and In Vivo Assessments of Cardiovascular Effects with Omadacycline.

Omadacycline is a first-in-class aminomethylcycline antibiotic with a broad spectrum of activity against Gram-positive and Gram-negative aerobes and anaerobes and atypical bacterial pathogens. A series of nonclinical studies, including mammalian pharmacologic receptor binding studies, human ether-a-go-go-related gene (hERG) channel binding studies, studies of the effects on ex vivo sinoatrial (SA) node activity, and studies of in vivo effects on cardiovascular function in the cynomolgus monkey, was undertaken to assess the cardiovascular risk potential. Omadacycline was found to bind almost exclusively to the muscarinic subtype 2 acetylcholine receptor (M2), and in the SA node model it antagonized the effect of a pan-muscarinic agonist (carbamylcholine) in a concentration-dependent manner. Omadacycline exhibited no effect on hERG channel activity at 100 µg/ml (179.5 µM), with a 25% inhibitory concentration of 166 µg/ml (298.0 µM). Omadacycline had no effect on QTc in conscious monkeys at doses up to 40 mg/kg of body weight. Overall, omadacycline appears to attenuate the parasympathetic influence on the heart rate but has a low potential to induce cardiac arrhythmia or to have clinically significant cardiovascular toxicity.

Administration of spores of nontoxigenic Clostridium difficile strain M3 for prevention of recurrent C. difficile infection: a randomized clinical trial.

IMPORTANCE: Clostridium difficile is the most common cause of health care-associated infection in US hospitals. Recurrence occurs in 25% to 30% of patients. OBJECTIVE: To determine the safety, fecal colonization, recurrence rate, and optimal dosing schedule of nontoxigenic C. difficile strain M3 (VP20621; NTCD-M3) for prevention of recurrent C. difficile infection (CDI). DESIGN, SETTING, AND PARTICIPANTS: Phase 2, randomized, double-blind, placebo-controlled, dose-ranging study conducted from June 2011 to June 2013 among 173 patients aged 18 years or older who were diagnosed as having CDI (first episode or first recurrence) and had successfully completed treatment with metronidazole, oral vancomycin, or both at 44 study centers in the United States, Canada, and Europe. INTERVENTIONS: Patients were randomly assigned to receive 1 of 4 treatments: oral liquid formulation of NTCD-M3, 10(4) spores/d for 7 days (n = 43), 10(7) spores/d for 7 days (n = 44), or 10(7) spores/d for 14 days (n = 42), or placebo for 14 days (n = 44). MAIN OUTCOMES AND MEASURES: The primary outcome was safety and tolerability of NTCD-M3 within 7 days of treatment. Exploratory secondary outcomes included fecal colonization with NTCD-M3 from end of study drug through week 6 and CDI recurrence from day 1 through week 6. RESULTS: Among 168 patients who started treatment, 157 completed treatment. One or more treatment-emergent adverse events were reported in 78% of patients receiving NTCD-M3 and 86% of patients receiving placebo. Diarrhea and abdominal pain were reported in 46% and 17% of patients receiving NTCD-M3 and 60% and 33% of placebo patients, respectively. Serious treatment-emergent adverse events were reported in 7% of patients receiving placebo and 3% of all patients who received NTCD-M3. Headache was reported in 10% of patients receiving NTCD-M3 and 2% of placebo patients. Fecal colonization occurred in 69% of NTCD-M3 patients: 71% with 10(7) spores/d and 63% with 10(4) spores/d. Recurrence of CDI occurred in 13 (30%) of 43 placebo patients and 14 (11%) of 125 NTCD-M3 patients (odds ratio [OR], 0.28; 95% CI, 0.11-0.69; P = .006); the lowest recurrence was in 2 (5%) of 43 patients receiving 10(7) spores/d for 7 days (OR, 0.1; 95% CI, 0.0-0.6; P = .01 vs placebo]). Recurrence occurred in 2 (2%) of 86 patients who were colonized vs 12 (31%) of 39 patients who received NTCD-M3 and were not colonized (OR, 0.01; 95% CI, 0.00-0.05; P < .001). CONCLUSIONS AND RELEVANCE: Among patients with CDI who clinically recovered following treatment with metronidazole or vancomycin, oral administration of spores of NTCD-M3 was well tolerated and appeared to be safe. Nontoxigenic C. difficile strain M3 colonized the gastrointestinal tract and significantly reduced CDI recurrence. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01259726.

Evaluation of an oral suspension of VP20621, spores of nontoxigenic Clostridium difficile strain M3, in healthy subjects.

VP20621, spores of nontoxigenic Clostridium difficile (NTCD) strain M3, is protective against challenge with toxigenic strains in hamsters. Human administration and colonization may prevent primary C. difficile infection (CDI) or recurrent CDI. Healthy adult subjects 18 to 45 years old or ≥60 years old received single or multiple doses of an oral suspension of VP20621 (10(4), 10(6), or 10(8) spores) or placebo. Group 4 (≥60 years old) received oral vancomycin for 5 days, followed by 14 days of VP20621 or placebo. Subjects were monitored for safety and followed through day 28. Stool was cultured for C. difficile before, during, and after VP20621 administration. Isolates were tested for toxin by enzyme immunoassay, and VP20621 was confirmed by molecular typing. After single escalating doses, no subjects had C. difficile-positive stool cultures. VP20621 was found in the stool of all subjects given 10(8) spores twice a day. Following vancomycin administration, VP20621 was detected in the stool of all subjects given 10(4), 10(6), or 10(8) spores daily beginning on day 2 to 6. Recovered isolates were toxin negative and confirmed to be VP20621. There were no serious adverse events, and no subjects prematurely discontinued study drugs. Following vancomycin administration, 2 placebo subjects became colonized with toxigenic C. difficile and 3 placebo subjects became colonized with VP20621. Persistent colonization with VP20621 was detected in stools on days 21 to 28 in 44% of subjects. VP20621 was well tolerated and able to colonize the gastrointestinal tracts of subjects pretreated with vancomycin. Further study of VP20621 to prevent CDI in patients is warranted.

Effects on maribavir susceptibility of cytomegalovirus UL97 kinase ATP binding region mutations detected after drug exposure in vitro and in vivo.

Resistance to the experimental human cytomegalovirus (CMV) UL97 kinase inhibitor maribavir has been mapped to UL97 mutations at codons 353, 397, 409 and 411, in the kinase ATP-binding region, and to mutations in the UL27 gene. We studied the maribavir susceptibility phenotypes of additional UL97 mutations observed in vitro and in clinical trials, and the effect of simultaneous mutation in both UL97 and UL27. In vitro selection under maribavir identified a new locus of UL97 mutation within the conserved kinase p-loop (L337M), which conferred low grade maribavir resistance (3.5-fold increased EC50) without ganciclovir cross-resistance. During maribavir Phase III CMV prevention clinical trials, three previously unknown UL97 sequence variants were detected in plasma samples after 27-98 days of drug exposure (I324V, S334G and S386L). These variants did not confer any drug resistance despite proximity to mutations that confer maribavir resistance. The UL27 resistance mutation R233S, when added to strains containing UL97 mutations L337M or V353A, doubled their maribavir EC50s. These results expand the range of UL97 maribavir-resistance mutations into another part of the kinase ATP-binding region, but offer no genotypic evidence that development of drug resistance affected the outcomes of Phase III maribavir clinical trials after drug exposure of up to 14 weeks. There is a potential for increased maribavir resistance in UL27-UL97 double mutants.