Susceptibility of Cutibacterium acnes to topical minocycline foam.

FMX101 4% minocycline foam (FMX101 4%) is a novel, topical minocycline formulation for treatment of acne vulgaris. We report that FMX101 4% had an MIC90 of 0.25 µg/ml and was ≥4-fold more active than comparator antimicrobials against a panel of 98 clinical Cutibacterium acnes isolates. The panel was diverse by clonal complex and sequence type, having 20 novel multi-locus sequence types including clonal complexes and sequence types associated with acne (CC1, CC3, and CC4; ST1 and ST3). Some isolates were phenotypically resistant to clindamycin (6.1%), erythromycin (14.3%), and tetracycline (2.0% intermediate resistance). Six isolates (6.4%) carried a mutation in the quinolone resistance-determining region of gyrA. With C. acnes, spontaneous resistance to FMX101 4% occurred at frequencies ranging from ≤5 × 10-9 to <1 × 10-8; mutations were identified in rpsJ, a gene encoding 30S ribosomal protein S10. No mutant exhibited a minocycline MIC above 0.5 µg/ml. No second-step mutation in previously isolated mutants or strains containing rpsJ ± 16S rRNA mutations was detected following minocycline challenge. Minocycline retained antibacterial activity against C. acnes over 15 multiple passages; thus, no selective growth advantage for minocycline-resistant mutants occurred under the experimental conditions. FMX101 4% has the potential to retain the favorable resistance profile of minocycline in diverse C. acnes isolates while providing the benefits of a topical formulation for treatment of acne vulgaris.

Evaluation of the In Vitro Activity of Eravacycline against a Broad Spectrum of Recent Clinical Anaerobic Isolates.

The novel fluorocycline antibiotic eravacycline is in development for use in the treatment of serious infections caused by susceptible and multidrug-resistant (MDR) aerobic and anaerobic Gram-negative and Gram-positive pathogens. Eravacycline and 11 comparator antibiotics were tested against recent anaerobic clinical isolates, including MDR Bacteroides spp. and Clostridium difficile Eravacycline was potent in vitro against all the isolates tested, including strains with tetracycline-specific resistance determinants and MDR anaerobic pathogens resistant to carbapenems and/or ß-lactam-ß-lactamase inhibitor combinations.

The Fluorocycline TP-271 Is Efficacious in Models of Aerosolized Francisella tularensis SCHU S4 Infection in BALB/c Mice and Cynomolgus Macaques.

TP-271 is a novel, fully synthetic fluorocycline in development for complicated bacterial respiratory infections. TP-271 was active in vitro against a panel of 29 Francisella tularensis isolates, showing MICs against 50% and 90% of isolates of 0.25 and 0.5 µg/ml, respectively. In a mouse model of inhalational tularemia, animals were exposed by aerosol to 91 to 283 50% lethal doses (LD50)/mouse of F. tularensis SCHU S4. Following 21 days of once-daily intraperitoneal dosing with TP-271 at 3, 6, 12, and 18 mg/kg of body weight/day, initiating at 24 h postchallenge, survival was 80%, 100%, 100%, and 100%, respectively. When treatment was initiated at 72 h postchallenge, survival was 89%, 100%, 100%, and 100% in the 3-, 6-, 12-, and 18-mg/kg/day TP-271 groups, respectively. No mice treated with the vehicle control survived. Surviving mice treated with TP-271 showed little to no relapse during 14 days posttreatment. In a nonhuman primate model of inhalational tularemia, cynomolgus macaques received an average aerosol exposure of 1,144 CFU of F. tularensis SCHU S4. Once-daily intravenous infusion with 1 or 3 mg/kg TP-271, or vehicle control, for 21 days was initiated within 6 h of confirmed fever. All animals treated with TP-271 survived to the end of the study, with no relapse during 14 days after the last treatment, whereas no vehicle control-treated animals survived. The protection and low relapse afforded by TP-271 treatment in these studies support continued investigation of TP-271 for use in the event of aerosolized exposure to F. tularensis.

The Fluorocycline TP-271 Is Efficacious in Models of Aerosolized Bacillus anthracis Infection in BALB/c Mice and Cynomolgus Macaques.

The fluorocycline TP-271 was evaluated in mouse and nonhuman primate (NHP) models of inhalational anthrax. BALB/c mice were exposed by nose-only aerosol to Bacillus anthracis Ames spores at a level of 18 to 88 lethal doses sufficient to kill 50% of exposed individuals (LD50). When 21 days of once-daily dosing was initiated at 24 h postchallenge (the postexposure prophylaxis [PEP] study), the rates of survival for the groups treated with TP-271 at 3, 6, 12, and 18 mg/kg of body weight were 90%, 95%, 95%, and 84%, respectively. When 21 days of dosing was initiated at 48 h postchallenge (the treatment [Tx] study), the rates of survival for the groups treated with TP-271 at 6, 12, and 18 mg/kg TP-271 were 100%, 91%, and 81%, respectively. No deaths of TP-271-treated mice occurred during the 39-day posttreatment observation period. In the NHP model, cynomolgus macaques received an average dose of 197 LD50 of B. anthracis Ames spore equivalents using a head-only inhalation exposure chamber, and once-daily treatment of 1 mg/kg TP-271 lasting for 14 or 21 days was initiated within 3 h of detection of protective antigen (PA) in the blood. No (0/8) animals in the vehicle control-treated group survived, whereas all 8 infected macaques treated for 21 days and 4 of 6 macaques in the 14-day treatment group survived to the end of the study (56 days postchallenge). All survivors developed toxin-neutralizing and anti-PA IgG antibodies, indicating an immunologic response. On the basis of the results obtained with the mouse and NHP models, TP-271 shows promise as a countermeasure for the treatment of inhalational anthrax.

In vitro susceptibility testing of eravacycline is unaffected by medium age and nonstandard assay parameters.

Eravacycline is a fluorocycline antibiotic in phase 3 clinical development for complicated intra-abdominal and urinary tract infections. To support its clinical development, a study was conducted to evaluate the effects of various susceptibility test parameters on the MIC values for aerobic bacteria. The results showed that eravacycline appears to be largely unaffected by medium age, medium additives, and other nonstandard assay conditions.

Eravacycline (TP-434) is active in vitro against biofilms formed by uropathogenic Escherichia coli.

Eravacycline (formerly TP-434) was evaluated in vitro against pre-established biofilms formed by a uropathogenic Escherichia coli strain. Biofilms were eradicated by 0.5 µg/ml eravacycline, which was within 2-fold of the MIC for planktonic cells. In contrast, colistin and meropenem disrupted biofilms at 32 and 2 µg/ml, respectively, concentrations well above their respective MICs of 0.5 and 0.03 µg/ml. Gentamicin and levofloxacin eradicated biofilms at concentrations within 2-fold of their MICs.

Eravacycline (TP-434) is efficacious in animal models of infection.

Eravacycline is a novel broad-spectrum fluorocycline antibiotic being developed for a wide range of serious infections. Eravacycline was efficacious in mouse septicemia models, demonstrating 50% protective dose (PD50) values of ≤ 1 mg/kg of body weight once a day (q.d.) against Staphylococcus aureus, including tetracycline-resistant isolates of methicillin-resistant S. aureus (MRSA), and Streptococcus pyogenes. The PD50 values against Escherichia coli isolates were 1.2 to 4.4 mg/kg q.d. In neutropenic mouse thigh infection models with methicillin-sensitive S. aureus (MSSA) and S. pyogenes, eravacycline produced 2 log10 reductions in CFU at single intravenous (i.v.) doses ranging from 0.2 to 9.5 mg/kg. In a neutropenic mouse lung infection model, eravacycline administered i.v. at 10 mg/kg twice a day (b.i.d.) reduced the level of tetracycline-resistant MRSA in the lung equivalent to that of linezolid given orally (p.o.) at 30 mg/kg b.i.d. At i.v. doses of 3 to 12 mg/kg b.i.d., eravacycline was more efficacious against tetracycline-resistant Streptococcus pneumoniae in a neutropenic lung infection model than linezolid p.o. at 30 mg/kg b.i.d. Eravacycline showed good efficacy at 2 to 10 mg/kg i.v. b.i.d., producing up to a 4.6 log10 CFU reduction in kidney bacterial burden in a model challenged with a uropathogenic E. coli isolate. Eravacycline was active in multiple murine models of infection against clinically important Gram-positive and Gram-negative pathogens.

Phase 2, randomized, double-blind study of the efficacy and safety of two dose regimens of eravacycline versus ertapenem for adult community-acquired complicated intra-abdominal infections.

Eravacycline is a novel fluorocycline, highly active against Gram-positive and Gram-negative pathogens in vitro, including those with tetracycline and multidrug resistance. This phase 2, randomized, double-blind study was conducted to evaluate the efficacy and safety of two dose regimens of eravacycline compared with ertapenem in adult hospitalized patients with complicated intra-abdominal infections (cIAIs). Patients with confirmed cIAI requiring surgical or percutaneous intervention and antibacterial therapy were randomized (2:2:1) to receive eravacycline at 1.5 mg/kg of body weight every 24 h (q24h), eravacycline at 1.0 mg/kg every 12 h (q12h), or ertapenem at 1 g (q24h) for a minimum of 4 days and a maximum of 14 days. The primary efficacy endpoint was the clinical response in microbiologically evaluable (ME) patients at the test-of-cure (TOC) visit 10 to 14 days after the last dose of study drug therapy. Overall, 53 patients received eravacycline at 1.5 mg/kg q24h, 56 received eravacycline at 1.0 mg/kg q12h, and 30 received ertapenem. For the ME population, the clinical success rate at the TOC visit was 92.9% (39/42) in the group receiving eravacycline at 1.5 mg/kg q24h, 100% (41/41) in the group receiving eravacycline at 1.0 mg/kg q12h, and 92.3% (24/26) in the ertapenem group. The incidences of treatment-emergent adverse events were 35.8%, 28.6%, and 26.7%, respectively. Incidence rates of nausea and vomiting were low in both eravacycline groups. Both dose regimens of eravacycline were as efficacious as the comparator, ertapenem, in patients with cIAI and were well tolerated. These results support the continued development of eravacycline for the treatment of serious infections, including those caused by drug-resistant Gram-negative pathogens. (This study has been registered at ClinicalTrials.gov under registration no. NCT01265784.).

Target- and resistance-based mechanistic studies with TP-434, a novel fluorocycline antibiotic.

TP-434 is a novel, broad-spectrum fluorocycline antibiotic with activity against bacteria expressing major antibiotic resistance mechanisms, including tetracycline-specific efflux and ribosomal protection. The mechanism of action of TP-434 was assessed using both cell-based and in vitro assays. In Escherichia coli cells expressing recombinant tetracycline resistance genes, the MIC of TP-434 (0.063 µg/ml) was unaffected by tet(M), tet(K), and tet(B) and increased to 0.25 and 4 µg/ml in the presence of tet(A) and tet(X), respectively. Tetracycline, in contrast, was significantly less potent (MIC ≥ 128 µg/ml) against E. coli cells when any of these resistance mechanisms were present. TP-434 showed potent inhibition in E. coli in vitro transcription/translation (50% inhibitory concentration [IC(50)] = 0.29 ± 0.09 µg/ml) and [(3)H]tetracycline ribosome-binding competition (IC(50) = 0.22 ± 0.07 µM) assays. The antibacterial potencies of TP-434 and all other tetracycline class antibiotics tested were reduced by 4- to 16-fold, compared to that of the wild-type control strain, against Propionibacterium acnes strains carrying a 16S rRNA mutation, G1058C, a modification that changes the conformation of the primary binding site of tetracycline in the ribosome. Taken together, the findings support the idea that TP-434, like other tetracyclines, binds the ribosome and inhibits protein synthesis and that this activity is largely unaffected by the common tetracycline resistance mechanisms.

Treatment with a novel topical nanoemulsion (NB-001) speeds time to healing of recurrent cold sores.

BACKGROUND: Current topical therapies for cold sores are only marginally beneficial due to poor skin penetration. We assessed the safety and efficacy of a novel topical antiviral nanoemulsion (NB-001) with high tissue bioavailability. OBJECTIVES: The primary endpoint was the time to lesion healing. METHODS: 482 subjects with recurrent cold sores were randomized to self-initiate treatment with either vehicle or NB-001 (0.1%, 0.3% or 0.5%) at the first signs or symptoms of a cold sore episode. Lotion was applied 5 times per day, approximately 3 to 4 hours apart, for 4 days. Time to lesion healing was correlated with NB-001 bioavailability determined in human cadaver skin. RESULTS: Subjects treated with 0.3% NB-001 showed a 1.3-day improvement in the mean time to healing compared to vehicle (P=0.006). This was consistent with human cadaver skin data indicating that the 0.3% nanoemulsion had the highest bioavailability, compared to 0.1% and 0.5% emulsions. No significant safety or dermal irritation concerns or systemic absorption were noted with any of the doses. CONCLUSIONS: Topical NB-001 (0.3%) was well tolerated and highly efficacious in shortening the time to healing of cold sores. The improvement in time to healing was similar to that reported for oral nucleoside analogues, but without systemic exposure. Topical agents for recurrent herpes labialis (cold sores) reduce healing time by one half day, compared to oral therapies that speed healing by a day or more. A topical antiviral nanoemulsion was well tolerated and improved cold sore healing time by over a day compared to vehicle control. Nanoemulsion (NB-001) could represent a more efficacious topical treatment for recurrent cold sores.

Efficacy, immunogenicity and stability of a novel intranasal nanoemulsion-adjuvanted influenza vaccine in a murine model.

Mutations of influenza virus increase concerns of worldwide epidemics resulting from the newly emergent strains. Current influenza vaccines are inefficient and require annual vaccinations. W805EC adjuvant is an oil-in-water emulsion composed of nanodroplets with an average diameter of approximately 400 nm. The nanoemulsion adjuvant has been used successfully to stimulate the immune response when mixed with several other antigens in animal models. In this study, W805EC nanoemulsion adjuvant activity was evaluated using nasal influenza vaccination in a murine model. Five to twenty percent W805EC adjuvant was used to inactivate influenza A/Puerto Rico/8/34/05 (H1N1). Mice immunized with the nanoemulsion adjuvanted influenza virus intranasally showed a robust specific humoral immune response as demonstrated using ELISA and HAI assays. Serum HAI titers were more than 104 following two vaccinations. Vaccinated mice were also protected against challenge with an LD80 of live influenza virus. Splenocytes from vaccinated mice were assayed for cytokine production following virus stimulation. The cytokine profile demonstrated a robust cellular immune response with enhanced Th1 and Th17 immunity that provided balanced immunity against both intracellular and extracellular forms of the virus. Additionally, the vaccine preparations showed minimal protein degradation but remained potent when stored at 4°C for up to three months. This work demonstrates that W805EC nanoemulsion adjuvant can effectively enhance the immunogenicity of influenza hemagglutinin antigen. The nanoemulsion adjuvant can result in antigen sparing and cross-protection. The potential exists for a nasally administered influenza vaccine that may require little or no refrigerated storage.

In vitro activities of the Rx-01 oxazolidinones against hospital and community pathogens.

Rx-01_423 and Rx-01_667 are two members of the family of oxazolidinones that were designed using a combination of computational and medicinal chemistry and conventional biological techniques. The compounds have a two- to eightfold-improved potency over linezolid against serious gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA), multidrug-resistant streptococci, and vancomycin-resistant enterococci. This enhanced potency extends to the coverage of linezolid-resistant gram-positive microbes, especially multidrug-resistant enterococci and pneumococci. Compounds from this series expand the spectrum compared with linezolid to include fastidious gram-negative organisms like Haemophilus influenzae and Moraxella catarrhalis. Like linezolid, the Rx-01 compounds are bacteriostatic against MRSA and enterococci but are generally bactericidal against S. pneumoniae and H. influenzae.

R chi-01, a new family of oxazolidinones that overcome ribosome-based linezolid resistance.

New and improved antibiotics are urgently needed to combat the ever-increasing number of multidrug-resistant bacteria. In this study, we characterized several members of a new oxazolidinone family, R chi-01. This antibiotic family is distinguished by having in vitro and in vivo activity against hospital-acquired, as well as community-acquired, pathogens. We compared the 50S ribosome binding affinity of this family to that of the only marketed oxazolidinone antibiotic, linezolid, using chloramphenicol and puromycin competition binding assays. The competition assays demonstrated that several members of the R chi-01 family displace, more effectively than linezolid, compounds known to bind to the ribosomal A site. We also monitored binding by assessing whether R chi-01 compounds protect U2585 (Escherichia coli numbering), a nucleotide that influences peptide bond formation and peptide release, from chemical modification by carbodiimide. The R chi-01 oxazolidinones were able to inhibit translation of ribosomes isolated from linezolid-resistant Staphylococcus aureus at submicromolar concentrations. This improved binding corresponds to greater antibacterial activity against linezolid-resistant enterococci. Consistent with their ribosomal A-site targeting and greater potency, the R chi-01 compounds promote nonsense suppression and frameshifting to a greater extent than linezolid. Importantly, the gain in potency does not impact prokaryotic specificity as, like linezolid, the members of the R chi-01 family show translation 50% inhibitory concentrations that are at least 100-fold higher for eukaryotic than for prokaryotic ribosomes. This new family of oxazolidinones distinguishes itself from linezolid by having greater intrinsic activity against linezolid-resistant isolates and may therefore offer clinicians an alternative to overcome linezolid resistance. A member of the R chi-01 family of compounds is currently undergoing clinical trials.

In-vitro activity of the novel fluorocycline eravacycline against carbapenem non-susceptible Acinetobacter baumannii.

The activity of eravacycline was compared with that of anti-Acinetobacter reference antimicrobials against carbapenem non-susceptible Acinetobacter baumannii isolates associated with an acquired OXA or up-regulation of the intrinsic OXA-51-like enzyme. Antimicrobial susceptibility testing was performed by broth microdilution of 286 non-duplicate, carbapenem non-susceptible A. baumannii isolates to eravacycline, amikacin colistin, doxycycline, imipenem, levofloxacin, meropenem, minocycline, sulbactam, tigecycline and tobramycin. Eravacycline showed greater activity than the comparators of the tetracycline class, levofloxacin, amikacin, tobramycin and colistin. The eravacycline MIC50/90 values were 0.5/1 mg/L and those for tigecycline, minocycline and doxycycline were 1/2, 4/8 and 32/ ≥ 64 mg/L, respectively. In conclusion, eravacycline was the most potent antibiotic of those tested against A. baumannii, including isolates that were resistant to sulbactam, imipenem/meropenem, levofloxacin and amikacin/tobramycin. Eravacycline has the potential to become a useful addition to the limited armamentarium of drugs that can be used to treat this problem pathogen.

In vitro activity of eravacycline against 2213 Gram-negative and 2424 Gram-positive bacterial pathogens isolated in Canadian hospital laboratories: CANWARD surveillance study 2014-2015.

Gram-negative (n=2213) and Gram-positive (n=2424) pathogens isolated from patients in 13 Canadian hospitals in 2014 and 2015 were tested for in vitro susceptibility to eravacycline and comparators using the Clinical and Laboratory Standards Institute broth microdilution method. The concentration of eravacycline inhibiting 90% of isolates (MIC90) ranged from 0.5 to 2µg/mL for 9 species of Enterobacteriaceae tested (n=2067). Eravacycline activity was largely unaffected by extended-spectrum ß-lactamase phenotypes in Escherichia coli (n=141) and Klebsiella pneumoniae (n=21). Eravacycline was active against Acinetobacter baumannii (n=28; MIC90, 0.5µg/mL) and Stenotrophomonas maltophilia (n=118; MIC90, 4µg/mL). Eravacycline MIC90 for staphylococci (n=1653), enterococci (n=289), and streptococci (n=482) ranged from 0.12 to 0.25, 0.06 to 0.12, and 0.015 to 0.06µg/mL, respectively. Eravacycline's potency was equivalent to or 2- to 4-fold greater than tigecycline against Enterobacteriaceae and Gram-positive cocci tested. Eravacycline demonstrates promising activity against recent clinical Gram-negative and Gram-positive bacteria, including multidrug-resistant pathogens.

Heterocyclyl tetracyclines. 2. 7-Methoxy-8-pyrrolidinyltetracyclines: discovery of TP-2758, a potent, orally efficacious antimicrobial against Gram-negative pathogens.

A convergent total synthesis platform led to the discovery of TP-2758 from a series of novel 7-methoxy-8-heterocyclyl tetracycline analogs. TP-2758 demonstrated high in vitro potency against key Gram-negative pathogens including extended spectrum ß-lactamases- and carbapenemase-producing Enterobacteriaceae and Acinetobacter spp. strains. This compound was efficacious when administered either intravenously or orally in multiple murine infection models and displayed a favorable preclinical pharmacological profile supporting its advancement into clinical development.

Improving on nature: antibiotics that target the ribosome.

Antibiotic resistance, along with the resolution of antibiotic-ribosomal subunit complexes at the atomic level, has provided new insights into modifications of clinically relevant antimicrobials that target the ribosome. Modifications to the aminoglycoside or negamycin scaffolds have been reported in the past, but few derivatives appear to be greatly improved compared to their parent compound. Computational and/or traditional screening efforts have yielded novel compounds that bind to the decoding site of the small (30S) ribosomal subunit; naphthyridones appear to bind only in the presence of poly(U) and tRNA(Phe), whereas quinolines bind in a similar manner to aminoglycosides. Streptogramin B analogs were designed that have an amide replacement of the labile ester bond. The resultant molecules were not substrates for the inactivating lyase, but were no longer inhibitors of translation. The synthesis of 16-membered macrolides that are modified at the C6 position with peptidyl moieties as well as conjugates of chloramphenicol to either nucleotide groups or pyrene have been described, but no antibacterial activity has been reported. X-ray crystal structures are now available that can be used to improve on natural or synthetic antibiotics that bind to either the 30S or the 50S ribosomal subunit.

Assessing the Efficacy and Safety of Eravacycline vs Ertapenem in Complicated Intra-abdominal Infections in the Investigating Gram-Negative Infections Treated With Eravacycline (IGNITE 1) Trial: A Randomized Clinical Trial.

Importance: Eravacycline is a novel, fully synthetic fluorocycline antibiotic of the tetracycline class with in vitro activity against clinically important gram-negative, gram-positive aerobic, and facultative bacteria including most of those resistant to cephalosporins, fluoroquinolones, ß-lactam/ß-lactamase inhibitors, multidrug resistant strains and carbapenem-resistant Enterobacteriaceae, and most anaerobic pathogens. Objective: To evaluate the efficacy and safety of eravacycline compared with ertapenem in adult hospitalized patients with complicated intra-abdominal infections (cIAIs). Design, Setting, and Participants: This was a phase III, randomized, double-blind, multicenter study that evaluated the efficacy and safety of eravacycline in comparison with ertapenem in patients with cIAI requiring surgical or percutaneous intervention. The test-of-cure evaluation was conducted 25 to 31 days after the first dose of the study drug and the follow-up visit was conducted 38 to 50 days after the first dose of the study drug. All patients recruited into this study were hospitalized. Five hundred forty-one patients were recruited for this study; 270 patients were randomized to receive eravacycline, and 271 patients were randomized to receive ertapenem. Patients had to meet all of the following criteria: hospitalized for cIAI requiring intervention; 18 years or older; evidence of systemic inflammatory response; pain caused by cIAI; able to provide informed consent; and diagnosis of cIAI with sonogram or radiographic imaging or visual confirmation. Analyses were done in intent-to-treat and evaluable populations. Interventions: Patients received eravacycline, 1.0 mg/kg every 12 hours, or ertapenem, 1.0 g every 24 hours, for a minimum of four 24-hour dosing cycles. Main Outcomes and Measures: Clinical outcome assessments were made at the end of treatment, test of cure, and follow-up visits and were classified as clinical cure, clinical failure, or indeterminate/missing. Results: In total, 541 patients were randomly assigned to treatment: 270 in the eravacycline group and 271 in the ertapenem group. The mean ages were 54.9 years and 55.4 years for the eravacycline and ertapenem groups, respectively. Most patients were white (263 of 270 patients [97.4%] in the eravacycline group and 260 of 271 patients [95.9%] in the ertapenem group). For the microbiological intent-to-treat population, the rates of clinical cure at the test-of-cure visit were 86.8% in the eravacycline group and 87.6% in the ertapenem group. The difference in clinical cure rates between the groups was -0.80% (95% CI, -7.1% to 5.5%), meeting the prespecified noninferiority margin and allowing for statistical noninferiority of eravacycline to ertapenem to be declared for this study. Both study drugs were well tolerated. Conclusions and Relevance: Overall, eravacycline demonstrated noninferiority to ertapenem for the treatment of patients with cIAI. Trial Registration: Clinicaltrials.gov Identifier: NCT01844856.