Efficacy and Safety of Tedizolid and Linezolid for the Treatment of Acute Bacterial Skin and Skin Structure Infections in Injection Drug Users: Analysis of Two Clinical Trials

Safety Evaluation of Contezolid (MRX-I) Versus Linezolid in Sprague-Dawley Rats

BACKGROUND & OBJECTIVES

Contezolid (MRX-I) is a novel ortho-fluorophenyl dihydropyridone developed by MicuRx Pharmaceuticals, Inc. It has been approved for the treatment of drug-resistant Gram-positive bacterial infections with relatively lower toxicity than other oxazolidinones such as linezolid. However, the toxicity profile has not yet been completely revealed. The aim of this study was to disclose the toxicity of contezolid in Sprague-Dawley (SD) rats and compare its toxicity profile with linezolid in a standard 4-week toxicity study.

METHODS

In this study, SD rats were orally administered with contezolid at doses of 20, 100, or 200/300 mg/kg/day for 28 consecutive days followed by a 28-day recovery period. Linezolid at doses of 100 or 200 mg/kg/day served as a comparator. Clinical observations, body weight, food consumption, hematology, clinical chemistry, urinalysis, and histopathological examinations were conducted.

RESULTS

All females in the 200 mg/kg/day linezolid group were subjected to unscheduled death due to myelosuppression within the first 2 weeks. No abnormalities were noted in the 200 mg/kg/day contezolid group, and the dose level was escalated to 300 mg/kg/day from day 15. Myelosuppression or myelosuppression-associated effects were comparable between the 300-mg/kg/day contezolid group and the 100-mg/kg/day linezolid group. The 'no observed adverse effect level' (NOAEL) of contezolid was determined to be 100 mg/kg/day (with an average AUC0-24 h of 268.4 μg*h/mL). At the same dose levels, the toxicity of contezolid was significantly lower than that of linezolid.

CONCLUSION

These findings demonstrate that contezolid exhibits a favorable safety profile compared with linezolid in this 4-week repeated-dose toxicity study in rats.

Optimizing Antibiotic Therapy for Intravenous Drug Users: A Narrative Review Unraveling Pharmacokinetics/Pharmacodynamics Challenges

Intravenous drug users (IVDUs) face heightened susceptibility to life-threatening gram-positive bacterial infections, particularly methicillin-resistant Staphylococcus aureus (MRSA). While the standard antibiotic dosing strategies for special patients, such as obese or critically ill individuals, are known to be inadequate, raising concerns about treatment efficacy, a similar sort of understanding has not been assessed for IVDUs yet. With this in mind, this review examines the pharmacokinetic/pharmacodynamic characteristics of antibiotics commonly used against gram-positive bacteria in IVDUs. Focusing on daptomycin, vancomycin, teicoplanin, aminoglycosides, and the novel lipoglycopeptide dalbavancin, the study reveals significant pharmacokinetic variations in IVDUs, suggesting the need for personalized dosing. Concomitant opioid substitution therapy and other factors, such as malnutrition, contribute to altered pharmacokinetics/pharmacodynamics, emphasizing the importance of targeted therapeutic drug monitoring. Overall, our study calls for increased awareness among clinicians regarding the unique pharmacokinetic/pharmacodynamic challenges in IVDUs and advocates for tailored antibiotic dosing strategies to enhance treatment outcomes in this marginalized population.

“A cross-sectional analysis of linezolid in combination with methadone or buprenorphine as a cause of serotonin toxicity.”

Background

Serotonin toxicity (also referred to as serotonin syndrome) results from medications that affect the neurotransmitter serotonin. The antibiotic linezolid and the opioids methadone and buprenorphine are all reported to cause serotonin toxicity, but the degree of risk with use of linezolid in combination with methadone or buprenorphine is unknown.

Methods

We conducted a retrospective cross-sectional analysis of adult patients hospitalized from November 2015 to October 2019 who were administered linezolid in combination with methadone and/or buprenorphine within 24 hours and a subgroup that received the combination for ≥3 days. Cases of serotonin toxicity were identified from the clinical notes in the electronic medical record and were classified as possible or definite based on the clinical record. The Hunter diagnostic criteria were retrospectively applied.

Results

There were 494 encounters in which linezolid was administered concurrently with methadone and buprenorphine. The mean patient age was 42.5 years, and 52.4% of encounters were of female patients. The mean duration of concurrent administration was 1.9 days. There were 106 encounters with a duration of concurrent administration ≥3 days (mean, 5.4 days). Two cases of possible serotonin toxicity and 0 cases of definite serotonin toxicity occurred; neither possible case met the Hunter criteria from the available information. Possible cases occurred in 0.40% of all encounters and 1.89% of encounters with ≥3 days of overlap (upper 1-sided 95% CI, 0.87% and 4.06%).

Conclusions

Serotonin toxicity occurring during the administration of linezolid in combination with methadone and/or buprenorphine occurred rarely among 494 hospital encounters, including 106 encounters with ≥3 days of overlap. Limitations include potential missed diagnoses of serotonin toxicity and short durations of overlap. Further study evaluating the short-term risk of this combination is needed.

Development and Validation of Stability-Indicating Assay Method for a Novel Oxazolidinone (PH-192) with Anticonvulsant Activity by Using UHPLC-QToF-MS

The treatment of seizure disorders with currently available pharmacotherapeutic agents is not optimal due to the failure of some patients to respond, coupled with occurrences of side effects. There is therefore a need for research into the development of new chemical entities as potential anticonvulsant agents, which are different structurally from the existing class of drugs. We recently identified a novel triazolyl-oxazolidinone derivative, PH-192, as a potential anticonvulsant agent. PH-192 demonstrated protection comparable to phenytoin against both chemically- and electrically-induced seizures in rodents with little or no central nervous system side effects. However, PH-192 did not exhibit protection beyond 30 min; therefore, we decide to investigate a stability-indicating assay of PH-192 in plasma and other solutions. A reliable and validated analytical method was developed to investigate the stability of PH-192 for 90 min in human plasma, acidic, basic, and oxidative conditions, using a Waters Acquity ultra high-performance liquid chromatography (UHPLC) system with a quaternary Solvent Manager (H-Class). A simple extraction method indicated that PH-192 was stable in human plasma after 90 min at 37 °C, with more than 90% successfully recovered. Moreover, stress stability studies were performed, and degradants were identified using LC-QToF-MS under acidic, basic, and oxidative simulated conditions.

Efficacy and Safety of Omadacycline Versus Linezolid in Acute Bacterial Skin and Skin Structure Infections in Persons Who Inject Drugs

Introduction

Acute bacterial skin and skin structure infections (ABSSSI) represent one of the most common reasons for emergency department visits, and are frequent complications of intravenous drug use in persons who inject drugs (PWID). This study examined the efficacy and safety of omadacycline, versus linezolid, in PWID and persons who do not inject drugs, in the Phase 3 Omadacycline in Acute Skin and Skin Structure Infection (OASIS-1, OASIS-2) studies.

Methods

Eligible participants were aged ≥ 18 years with qualifying skin infections: wound infection, cellulitis, erysipelas, or major abscess. The primary efficacy endpoint was early clinical response (ECR) in the modified intent-to-treat (mITT) population, defined as survival with ≥ 20% reduction in lesion size at 48–72 h after the first dose of omadacycline or linezolid. Key secondary endpoints included investigator-assessed clinical response at the post-treatment evaluation (PTE) in the mITT and clinical per-protocol populations, and clinical response at PTE in the micro-mITT population. Safety was assessed based on adverse events (AEs) and standard clinical laboratory tests. Efficacy endpoints of clinical response at ECR and PTE were analyzed for the mITT and clinically evaluable (CE) PTE populations.

Results

In total, 1380 patients (822 PWID, 558 non-PWID) were included in this secondary analysis. Wound infections were reported more frequently in the PWID subgroup (72.8%) at baseline; cellulitis or erysipelas (43.9%) and major abscess (37.4%) were the most frequently reported baseline infections in the non-PWID subgroup. Clinical success rates at ECR and PTE in the mITT population, and at PTE in the CE population, were high for patients receiving omadacycline or linezolid. Severe or serious treatment-emergent AEs (TEAEs), and TEAEs leading to discontinuation, were infrequent.

Conclusion

This subgroup analysis showed that omadacycline was effective and well tolerated, regardless of PWID status.

Potential role of new-generation antibiotics in acute bacterial skin and skin structure infections

PURPOSE OF REVIEW

To summarize the available results of primary analyses from high-quality randomized studies of either recently approved or possible future agents for the treatment of acute bacterial skin and skin structure infections (ABSSSI).

RECENT FINDINGS

In the last 2 decades, several novel agents have been approved for the treatment of ABSSSI, that are also active against methicillin-resistant Staphylococcus aureus (MRSA). In addition to already available agents, further molecules are in clinical development that could become available for treating ABSSSI in the forthcoming future.

SUMMARY

The current and future availability of several new-generation antibiotics will allow to modulate therapeutic choices not only on efficacy but also on other relevant factors such as the combination of the drug safety profile and the comorbidities of any given patient, the expected adherence to outpatient therapy, and the possibilities of early discharge or avoiding hospitalization by means of oral formulations, early switch from intravenous to oral therapy, or single-dose administration of long-acting intravenous agents. With the advent of new-generation antibiotics, all these factors are becoming increasingly essential for tailoring treatment to individual patients in line with the principles of personalized medicine, and for optimizing the use of healthcare resources.

A Phase 3, Randomized, Double-Blind Study Comparing Tedizolid Phosphate and Linezolid for Treatment of Ventilated Gram-Positive Hospital-Acquired or Ventilator-Associated Bacterial Pneumonia

BACKGROUND

Hospital-acquired bacterial pneumonia (HABP) and ventilator-associated bacterial pneumonia (VABP) are associated with high mortality rates. We evaluated the efficacy and safety of tedizolid (administered as tedizolid phosphate) for treatment of gram-positive ventilated HABP/VABP.

METHODS

In this randomized, noninferiority, double-blind, double-dummy, global phase 3 trial, patients were randomized 1:1 to receive intravenous tedizolid phosphate 200 mg once daily for 7 days or intravenous linezolid 600 mg every 12 hours for 10 days. Treatment was 14 days in patients with concurrent gram-positive bacteremia. The primary efficacy end points were day 28 all-cause mortality (ACM; noninferiority margin, 10%) and investigator-assessed clinical response at test of cure (TOC; noninferiority margin, 12.5%) in the intention-to-treat population.

RESULTS

Overall, 726 patients were randomized (tedizolid, n = 366; linezolid, n = 360). Baseline characteristics, including incidence of methicillin-resistant Staphylococcus aureus (31.3% overall), were well balanced. Tedizolid was noninferior to linezolid for day 28 ACM rate: 28.1% and 26.4%, respectively (difference, -1.8%; 95% confidence interval [CI]: -8.2 to 4.7). Noninferiority of tedizolid was not demonstrated for investigator-assessed clinical cure at TOC (tedizolid, 56.3% vs linezolid, 63.9%; difference, -7.6%; 97.5% CI: -15.7 to 0.5). In post hoc analyses, no single factor accounted for the difference in clinical response between treatment groups. Drug-related adverse events occurred in 8.1% and 11.9% of patients who received tedizolid and linezolid, respectively.

CONCLUSIONS

Tedizolid was noninferior to linezolid for day 28 ACM in the treatment of gram-positive ventilated HABP/VABP. Noninferiority of tedizolid for investigator-assessed clinical response at TOC was not demonstrated. Both drugs were well tolerated.

CLINICAL TRIALS REGISTRATION

NCT02019420.

Tedizolid (torezolid) for the treatment of complicated skin and skin structure infections

INTRODUCTION

Acute bacterial skin and skin structure infections (ABSSSI) are among the most frequent infectious diseases. Recently, several new antibiotics with activity against MRSA have been approved. Tedizolid, a second-generation oxazolidinone approved for ABSSSI offers theoretical advantages over first-generation oxazolidinones.

AREAS COVERED

A comprehensive online search of Medline, ClinicalTrials.gov, and conference presentations was made, selecting articles between January 2000 and April 2020. In this review, the authors discuss the chemical and microbiological properties of tedizolid, summarize its efficacy, safety, and potential role in the treatment of ABSSSI as well as the potential for future indications.

EXPERT OPINION

Tedizolid has proven to be non-inferior compared to linezolid for the treatment of ABSSSI in two registrational phase III clinical trials, being well tolerated. Tedizolid exhibits antibacterial activity against the most important ABSSSI pathogens (including multidrug-resistant strains of MRSA), as well as mycobacteria and Nocardia. It appears to have a safe profile, including decreased myelotoxicity and no significant drug interactions. Preliminary studies with longer duration of therapy seem to confirm these potential benefits. Overall, tedizolid expands the newly acquired armamentarium to treat ABSSSI. The role of tedizolid for other indications is under investigation and has yet to be determined.

Current role of oxazolidinones and lipoglycopeptides in skin and soft tissue infections

PURPOSE OF REVIEW

An increase of skin and soft tissue infections involving Staphylococcus aureus has been reported in community and hospital settings. Methicillin resistance in S. aureus is associated with treatment failure and increased mortality. Recently, new antimicrobials with enhanced activity against methicillin-resistant Staph. aureus have been approved for the treatment of skin and soft tissue infections. Among these, novel oxazolidinones and lipoglycopeptides represent options with favorable pharmacokinetic characteristics and safety profiles.

RECENT FINDINGS

Newly approved compounds include tedizolid, characterized by the availability of both oral and intravenous formulation and once daily administration and dalbavancin, a long-acting antimicrobial allowing for weekly administration. These new molecules present advantages, such as enhanced activity against multidrug-resistant Gram-positive bacteria and favorable safety profiles.

SUMMARY

We have reviewed the pharmacokinetic characteristics and the implications for use in skin and soft tissue infections of tedizolid and dalbavancin. Advantages associated with the use of these compounds include the possibility for early patient discharge, reduced hospital length of stay, and outpatient treatment, with potential impact on morbidity, mortality, and overall health-care costs.

Once-daily oral omadacycline versus twice-daily oral linezolid for acute bacterial skin and skin structure infections (OASIS-2): a phase 3, double-blind, multicentre, randomised, controlled, non-inferiority trial

BACKGROUND

Pathogen resistance and safety concerns limit oral antibiotic options for the treatment of acute bacterial skin and skin structure infections (ABSSSI). We aimed to compare the efficacy and safety of once-daily oral omadacycline, an aminomethylcycline antibiotic, versus twice-daily oral linezolid for treatment of ABSSSI.

METHODS

In this phase 3, double-blind, randomised, non-inferiority study, eligible adults with ABSSSI at 33 sites in the USA were randomly assigned (1:1) to receive omadacycline (450 mg orally every 24 h over the first 48 h then 300 mg orally every 24 h) or linezolid (600 mg orally every 12 h) for 7-14 days. Randomisation was done via an interactive response system using a computer-generated schedule, and stratified by type of infection (wound infection, cellulitis or erysipelas, or major abscess) and receipt (yes or no) of allowed previous antibacterial treatment. Investigators, funders, and patients were masked to treatment assignments. Primary endpoints were early clinical response, 48-72 h after first dose, in the modified intention-to-treat (mITT) population (randomised patients without solely Gram-negative ABSSSI pathogens at baseline), and investigator-assessed clinical response at post-treatment evaluation, 7-14 days after the last dose, in the mITT population and clinically evaluable population (ie, mITT patients who had a qualifying infection as per study-entry criteria, received study drug, did not receive a confounding antibiotic, and had an assessment of outcome during the protocol-defined window). The safety population included randomised patients who received any amount of study drug. We set a non-inferiority margin of 10%. This study is registered with ClinicalTrials.gov, NCT02877927, and is complete.

FINDINGS

Between Aug 11, 2016, and June 6, 2017, 861 participants were assessed for eligibility. 735 participants were randomly assigned, of whom 368 received omadacycline and 367 received linezolid. Omadacycline (315 [88%] of 360) was non-inferior to linezolid (297 [83%] of 360) for early clinical response (percentage-point difference 5·0, 95% CI -0·2 to 10·3) in the mITT population. For investigator-assessed clinical response at post-treatment evaluation, omadacycline was non-inferior to linezolid in the mITT (303 [84%] of 360 vs 291 [81%] of 360; percentage-point difference 3·3, 95% CI -2·2 to 9·0) and clinically evaluable (278 [98%] of 284 vs 279 [96%] of 292; 2·3, -0·5 to 5·8) populations. Mild to moderate nausea and vomiting were the most frequent treatment-emergent adverse events in omadacycline (111 [30%] of 368 and 62 [17%] of 368, respectively) and linezolid (28 [8%] of 367 and 11 [3%] of 367, respectively) groups.

INTERPRETATION

Once-daily oral omadacycline was non-inferior to twice-daily oral linezolid in adults with ABSSSI, and was safe and well tolerated. Oral-only omadacycline represents a new treatment option for ABSSSI, with potential for reduction in hospital admissions and cost savings.

FUNDING

Paratek Pharmaceuticals.

Tedizolid phosphate for the treatment of acute bacterial skin and skin-structure infections: an evidence-based review of its place in therapy

Introduction

Tedizolid phosphate is an oxazolidinone approved for the treatment of acute bacterial skin and skin-structure infections (ABSSSIs) and active against methicillin-resistant Staphylococcus aureus.

Aims

The objective of this article was to review the evidence for the efficacy and safety of tedizolid phosphate for the treatment of ABSSSI.

Evidence review

Approval of tedizolid phosphate for the treatment of ABSSSI was based on the results of two phase III randomized controlled trials, ESTABLISH-1 (NCT01170221) and ESTABLISH-2 (NCT01421511), comparing 6-day once-daily tedizolid vs 10-day twice-daily linezolid. In ESTABLISH-1, noninferiority was met with early clinical response rates of 79.5% and 79.4% in tedizolid and linezolid groups, respectively (difference 0.1%, 95% CI –6.1% to 6.2%, with a 10% noninferiority margin). In ESTABLISH-2, noninferiority was met with 85% and 83% rates of early clinical response in tedizolid and linezolid groups, respectively (difference 2.6%, 95% CI –3.0% to 8.2%). Pooled data from ESTABLISH-1 and ESTABLISH-2 indicated a lower frequency of thrombocytopenia in tedizolid-treated than in linezolid-treated patients.

Conclusion

Tedizolid offers the option of an intravenous to oral switch, allows once-daily administration, and presents lower risk of myelotoxicity when a 6-day course is used for the treatment of ABSSSI. Greater economic cost associated with this antibiotic could be offset by its shorter treatment duration and possibility of oral administration in routine clinical practice, although either sponsored or nonsponsored postmarketing observational experience remains essential for ultimately confirming the effectiveness and tolerability of tedizolid outside clinical trials.