In Vitro Activity and Potency of the Novel Oxazolidinone Contezolid (MRX-I) Tested against Gram-Positive Clinical Isolates from the United States and Europe

Pharmacotherapies for multidrug-resistant gram-positive infections: current options and beyond

INTRODUCTION

Infections due to multidrug-resistant organisms (MDRO) are a serious concern for public health with high morbidity and mortality. Though many antibiotics have been introduced to manage these infections, there are remaining concerns regarding the optimal management of Gram-positive MDROs.

AREAS COVERED

A literature search on the PubMed/Medline database was conducted. We applied no language and time limits for the search strategy. In this narrative review, we discuss the current options for managing Gram-positive MDROs as well as non-traditional antibacterial agents in development.

EXPERT OPINION

Despite their introduction more than 70 years ago, glycopeptides are still the cornerstone in treating Gram-positive infections: all registrative studies of new antibiotics have glycopeptides as control; these studies are designed as not inferior studies, therefore it is almost impossible to give recommendations other than the use of glycopeptides in the treatment of Gram-positive infections. The best evidence on treatments different from glycopeptides comes from post-hoc analysis and meta-analysis. Non-traditional antibacterial agents are being studied to aid in short and effective antibiotic therapies. The use of non-traditional antibacterial agents is not restricted to replacing traditional antibacterial agents with alternative therapies; instead, they should be used in combination with antibiotic therapies.

Advances in contezolid: novel oxazolidinone antibacterial in Gram-positive treatment

PURPOSE

The principal objective of this project was to review and thoroughly examine the chemical characteristics, pharmacological activity, and quantification methods associated with contezolid.

METHODS

The article was based on published and ongoing preclinical and clinical studies on the application of contezolid. These studies included experiments on the physicochemical properties of contezolid, in vitro antimicrobial research, in vivo antimicrobial research, and clinical trials in various phases. There were no date restrictions on these studies.

RESULTS

In June 2021, contezolid was approved for treating complicated skin and soft tissue infections. The structural modification of contezolid has resulted in better efficacy compared to linezolid. It inhibits bacterial growth by preventing the production of the functional 70S initiation complex required to translate bacterial proteins. The current evidence has indicated a substantial decline in myelosuppression and monoamine oxidase inhibition without impairing its antibacterial properties. Contezolid was found to have a more significant safety profile and to be metabolised by flavin monooxygenase 5, reducing the risk of harmful effects due to drug-drug interactions. Adjusting doses is unnecessary for patients with mild to moderate renal or hepatic insufficiency.

CONCLUSION

As an oral oxazolidinone antimicrobial agent, contezolid is effective against multi-drug resistant Gram-positive bacteria. The introduction of contezolid provided a new clinical option.

Sepsis and pneumonia caused by Enterococcus faecium following liver transplantation treated with contezolid as the first-line therapy

BACKGROUND

Enterococcus faecium (E. faecium) stands as a prominent pathogen contributing to Gram-positive bacterial infections in individuals who have undergone liver transplantation.

CASE PRESENTATION

A 66-year-old male with a three-year history of treated anxiety disorder was admitted to our hospital due to recurrent abdominal distension and oliguria. He was diagnosed with hepatic veno-occlusive disease (HVOD), hepatic failure, pneumonia, renal insufficiency and abdominal ascites. A liver transplantation procedure was performed, but the patient's infection index increased on the first day after surgery. Empirical antibiotic therapy with ceftriaxone and meropenem and preventive antifungal therapy were applied. Sputum culture, blood culture, ascites culture and bronchoalveolar lavage fluid (BALF) next-generation sequencing (NGS), revealed the presence of E. faecium. Given the application of various nephrotoxic immunosuppressive agents after liver transplantation, pre-existing renal insufficiency, severe bone marrow suppression, and a history of anxiety disorder treated with sertraline, contezolid was added for the treatment of the Gram-positive bacterial infection. Sixteen days after surgery, cultures from ascites and sputum yielded negative results for fungi and bacteria. Contezolid was subsequently discontinued without any reported adverse events during follow-up.

CONCLUSION

Treatment with contezolid as the first-line therapy for sepsis and pneumonia caused by E. faecium following liver transplantation has shown satisfactory efficacy and safety. Therefore, contezolid may hold great promise for managing this life-threatening condition.

Antibiotic Strategies for Severe Community-Acquired Pneumonia

Despite advancements in health systems and intensive care unit (ICU) care, along with the introduction of novel antibiotics and microbiologic techniques, mortality rates in severe community-acquired pneumonia (sCAP) patients have not shown significant improvement. Delayed admission to the ICU is a major risk factor for higher mortality. Apart from choosing the appropriate site of care, prompt and appropriate antibiotic therapy significantly affects the prognosis of sCAP. Treatment regimens involving ceftaroline or ceftobiprole are currently considered the best options for managing patients with sCAP. Additionally, several other molecules, such as delafloxacin, lefamulin, and omadacycline, hold promise as therapeutic strategies for sCAP. This review aims to provide a comprehensive summary of the key challenges in managing adults with severe CAP, focusing on essential aspects related to antibiotic treatment and investigating potential strategies to enhance clinical outcomes in sCAP patients.

Antistaphylococcal discovery pipeline; where are we now?

The serious spread of antibiotic-resistant Staphylococcal aureus strains is alarming. This is reflected by the measures governments and health-related bodies are offering to ease antibiotic drug development. Finding new active agents, preferably with novel mechanism of action, or even finding new targets for drug development are essential. In this review, we summarize the current status of novel antistaphylococcal agents undergoing clinical trials. We mainly discuss antistaphylococcal small molecules and peptides in the text with a special focus on their chemistry, while antistaphylococcal immunotherapy (antibodies) are mentioned in a summative table. This review shall serve as a summary that influences future synthetic efforts in the antistaphyloccocals development field.

Compassionate use of contezolid in a toddler with severe community-acquired pneumonia induced by staphylococcus aureus: a case report and follow-up

Background

Initial choices of antimicrobial therapy for most cases of community-acquired pneumonia (CAP) in children under 5 years of age are typically based on local epidemiology, risk factors assessment, and subsequent clinical parameters and positive cultures, which can lead to the underdiagnosis and underestimation of lung infections caused by uncommon pathogens. Contezolid, an orally administered oxazolidinone antibiotic, gained approval from the National Medical Products Administration (NMPA) of China in June 2021 for managing complicated skin and soft tissue infections (cSSTI) caused by staphylococcus aureus (SA), streptococcus pyogenes, or streptococcus agalactis. Owing to its enhanced safety profile and ongoing clinical progress, the scope of contezolid's clinical application continues to expand, benefiting a growing number of patients with Gram-positive bacterial infections.

Case summary

In this report, we present the first use of contezolid in a toddler with severe CAP caused by SA, aiming to avoid potential adverse drug reactions (ADRs) associated with vancomycin and linezolid.

Conclusion

Although contezolid has not been officially indicated for CAP, it has been shown to be effective and safe in the management of SA-induced severe CAP in this toddler, suggesting its potential as an alternative option in the dilemma, especially for patients who are susceptible or intolerant to ADRs associated with first-line anti-methicillin-resistant staphylococcus aureus (MRSA) antimicrobial agents.

Strategies for the Discovery of Oxazolidinone Antibacterial Agents: Development and Future Perspectives

Oxazolidinones represent a significant class of synthetic bacterial protein synthesis inhibitors that are primarily effective against Gram-positive bacteria. The commercial success of linezolid, the first FDA-approved oxazolidinone antibiotic, has motivated researchers to develop more potent oxazolidinones by employing various drug development strategies to fight against antimicrobial resistance, some of which have shown promising results. Thus, this Perspective aims to discuss the strategies employed in constructing oxazolidinone-based antibacterial agents and summarize recent advances in discovering oxazolidinone antibiotics to provide valuable insights for potentially developing next-generation oxazolidinone antibacterial agents or other pharmaceuticals.

Rare tuberculosis in recipients of allogeneic hematopoietic stem cell transplantation successfully treated with contezolid-a typical case report and literature review

Background

Tuberculosis (TB) is a rare but potentially devastating complication in hematopoietic stem cell transplantation (HSCT) recipients. Myelosuppression-related antibiotics should be used cautiously in patients with hematological malignancies, especially those undergoing bone marrow transplantation and receiving bone marrow suppression therapy. Although linezolid has become the recommended drug for severe TB, its hematological toxicity is still an obstacle to its clinical application. Contezolid is a new representative of oxazolidinones in clinical development, showing superior anti-infection efficacy, but there have been no reports on the treatment of post-HSCT TB.

Case presentation

We reported a patient with acute lymphoblastic leukemia suffered from pulmonary TB infection after HSCT. During anti-TB treatment, the patient had a poor response to linezolid-containing regimen, and developed side effects such as gingival bleeding and thrombocytopenia, so the administration was switched to contezolid. After 15 days of continuous treatment, the patient's platelet increased to 58×109/L, and he was discharged in stable condition. During subsequent anti-TB treatment with contezolid for more than 7 months, the platelets remained stable, and no hematological adverse reactions and no symptoms of peripheral neuropathy were observed. Moreover, repeat imaging showed that the bilateral lung lesions were significantly reduced, indicating a good outcome for the patient.

Conclusion

This was the first successful case of post-HSCT TB patients treated with contezolid-containing antibiotic management strategies, which exhibited remarkable efficacy and good safety in this deadly disease.

In vitro activities of contezolid (MRX-I) against drug-sensitive and drug-resistant Mycobacterium tuberculosis

A novel oxazolidinone for the treatment of Mycobacterium tuberculosis has been developed, but the activity of contezolid (MRX-I) still needs to be clarified. In this study, we isolated Mycobacterium tuberculosis from 48 clinical patients with pulmonary tuberculosis. Roche drug susceptibility tests identified drug-sensitive and 39 drug-resistant M. tuberculosis isolates. Drug susceptibility assays indicated that MRX-I exhibited anti-Mycobacterium tuberculosis activity against both drug-sensitive and drug-resistant isolates, with an advantage against drug-resistant isolates. The results also showed that the anti-Mycobacterium tuberculosis activity was comparable to that of linezolid. IMPORTANCE Currently, Mycobacterium tuberculosis has exhibited increased drug resistance, leading to ineffective drug treatment in many patients with tuberculosis. Among the anti-Mycobacterium tuberculosis drugs, oxazolidinones have been gradually developed. Contezolid (MRX-I) has been newly developed in China with advantages versus the first oxazolidinone antibiotic approved by the Food and Drug Administration for clinical use, but the anti-M. tuberculosis activity needs to be further clarified. In this study, in vitro activities of MRX-I against M. tuberculosis were tested. The drug susceptibility assays indicated that MRX-I exhibited anti-M. tuberculosis activity comparable to that of linezolid, with an advantage against drug-resistant isolates.

Use of Contezolid for the Treatment of Refractory Infective Endocarditis in a Patient with Chronic Renal Failure: Case Report

Infective endocarditis (IE) caused by methicillin-resistant Staphylococcus aureus (MRSA) is usually life threatening and difficult to treat. Contezolid is a newly approved oxazolidinone antimicrobial agent showing potent activity against MRSA. We successfully treated a case of refractory IE caused by MRSA with contezolid in a 41-year-old male patient. The patient was admitted due to recurrent fever and chills for more than 10 days. He had chronic renal failure for more than 10 years and under ongoing hemodialysis. The diagnosis of IE was confirmed by echocardiography and positive blood culture of MRSA. Antimicrobial therapy with vancomycin combined with moxifloxacin, and daptomycin combined with cefoperazone-sulbactam failed in the first 27 days. Moreover, the patient had to take oral anticoagulant after removal of tricuspid valve vegetation and tricuspid valve replacement. Contezolid 800 mg was added orally every 12 hours, to replace vancomycin, for its anti-MRSA activity and good safety profile. Temperature normalized after the contezolid add-on treatment for 15 days. No relapse of infection or drug-related adverse reaction was reported at 3-month follow-up since the diagnosis of IE. This successful experience serves as motivation for a well-designed clinical trial to confirm the utility of contezolid in managing IE.

Severe Community-Acquired Pneumonia Caused by Methicillin-Sensitive Staphylococcus aureus: Successfully Treated with Contezolid - A Case Report and Literature Review

Background

Staphylococcus aureus has been well recognized as an important cause of community-acquired pneumonia (CAP), with non-specific characteristics and poor prognosis. In severe CAP (SCAP) guidelines, β-lactam combined with macrolides or fluoroquinolones therapy was recommended, but the efficacy is not satisfactory due to the continued spread of antimicrobial resistance. Contezolid is a new representative of oxazolidinones in clinical development, but no relevant reports have been reported for the treatment of SCAP. This was the first report of a patient with Staphylococcus aureus SCAP who was successfully treated with contezolid combined with other antibiotics and rehabilitation exercise.

Case Presentation

A 44-year-old woman with high blood pressure and diabetes was admitted to our hospital owing to cough, sputum, wheezing for 2 weeks, and aggravation for 2 days. The bronchoscopic alveolar lavage and microorganism-Rapid On Site Evaluation (BAL-mROSE) was used to get pathological data, which were positive for Staphylococcus aureus, in line with blood cultures. During hospitalization, the patient received endotracheal intubation for assisted breathing and anti-infective therapy, including meropenem, linezolid, teicoplanin and tazocin successively. Finally, contezolid obtained excellent result, with platelet recovery to normal levels and significant improvement in pulmonary imaging. Meanwhile, the patient's swallowing disorder improved after continuous rehabilitation exercise. After discharge, she received contezolid consolidation therapy for 1 week and was free of complaints during the 30-day follow-up without any special treatment for SCAP.

Discussion

Treatment with contezolid combined with other antibiotics and rehabilitation exercise for SCAP has shown remarkable efficacy and good safety; hence, this regimen is a promising treatment strategy for this fatal disease.

Side-by-Side Profiling of Oxazolidinones to Estimate the Therapeutic Window against Mycobacterial Infections

New oxazolidinones are in clinical development for the treatment of tuberculosis and nontuberculous mycobacterial (NTM) infections, as a replacement for linezolid and tedizolid, which cause mitochondrial toxicity after prolonged treatment. Here, we carried out side-by-side measurements of mitochondrial protein synthesis inhibition and activity against clinically relevant mycobacterial pathogens of approved and novel oxazolidinones. We found a large range of selectivity indices suggesting TBI-223 and sutezolid as promising candidates against tuberculosis and NTM lung disease caused by Mycobacterium kansasii.

Contezolid, a novel oxazolidinone antibiotic, may improve drug-related thrombocytopenia in clinical antibacterial treatment

One of the major limitations in the clinical use of existing oxazolidinone antibiotics is their characteristic adverse reactions, in particular thrombocytopenia. In anti-infective treatment, if patients are suspected of having drug-induced thrombocytopenia, the first step is to immediately discontinue the offending drug. Even in patients with severe infections, the antibacterial drug may need to be changed or the antibacterial treatment may need to be discontinued because thrombocytopenia may have a more serious clinical prognosis. In addition, if the patient needs to continue antibacterial treatment after discharge, the lack of conditions for monitoring platelet levels may also pose hidden dangers to the patient. Contezolid is an orally administered oxazolidinone antibacterial agent approved by the National Medical Products Administration of China in 2021. We found that contezolid may have an improved safety profile with a significantly reduced potential for myelosuppression based on the results of our observational clinical study. In this article, we review the advantages of contezolid as a new oxazolidinone antibiotic and describe three typical clinical cases of patients who experienced drug-induced thrombocytopenia after using linezolid. The platelet levels of these different patients were all significantly improved to varying degrees after initiation of contezolid treatment.

The Novel Oxazolidinone TBI-223 Is Effective in Three Preclinical Mouse Models of Methicillin-Resistant Staphylococcus aureus Infection

Staphylococcus aureus is an important cause of various infections in humans, including bacteremia, skin and soft tissue infections, and infections associated with implanted medical devices. The emergence of hospital- and community-acquired methicillin-resistant Staphylococcus aureus (MRSA) underscores the urgent and unmet need to develop novel, safe, and effective antibiotics against these multidrug-resistant clinical isolates. Oxazolidinone antibiotics such as linezolid have excellent oral bioavailability and provide coverage against MRSA infections. However, their widespread and long-term use is often limited by adverse effects, especially myelosuppression. TBI-223 is a novel oxazolidinone with potentially reduced myelosuppression, compared to linezolid, but its efficacy against MRSA infections is unknown. Therefore, the preclinical efficacy of TBI-223 (80 and 160 mg/kg twice daily) was compared with that of linezolid (40 and 80 mg/kg twice daily) and sham treatment in mouse models of MRSA bacteremia, skin wound infection, and orthopedic-implant-associated infection. The dosage was selected based on mouse pharmacokinetic analysis of both linezolid and TBI-223, as well as measurement of the MICs. In all three models, TBI-223 and linezolid had comparable dose-dependent efficacies in reducing bacterial burden and disease severity, compared with sham-treated control mice. Taken together, these findings indicate that TBI-223 represents a novel oxazolidinone antibiotic that may provide an additional option against MRSA infections. Future studies in larger animal models and clinical trials are warranted to translate these findings to humans. IMPORTANCE Staphylococcus aureus is the predominant cause of bloodstream, skin, and bone infections in humans. Resistance to commonly used antibiotics is a growing concern, making it more difficult to treat staphylococcal infections. Use of the oxazolidinone antibiotic linezolid against resistant strains is hindered by high rates of adverse reactions during prolonged therapy. Here, a new oxazolidinone named TBI-223 was tested against S. aureus in three mouse models of infection, i.e., bloodstream infection, skin infection, and bone infection. We found that TBI-223 was as effective as linezolid in these three models. Previous data suggest that TBI-223 has a better safety profile than linezolid. Taken together, these findings indicate that this new agent may provide an additional option against MRSA infections. Future studies in larger animal models and clinical trials are warranted to translate these findings to humans.

Discovery of Antibacterial Contezolid Acefosamil: Innovative O-Acyl Phosphoramidate Prodrug for IV and Oral Therapies

New oral antibiotic contezolid (CZD) is effective against Gram-positive infections but unsuitable for intravenous (IV) administration due to its modest solubility. To address the medical need for an IV form of CZD, its isoxazol-3-yl phosphoramidate derivatives have been explored, and contezolid acefosamil (CZA, 8), the first representative of a novel O-acyl phosphoramidate prodrug class, has been identified. CZA exhibits high aqueous solubility (>200 mg/mL) and good hydrolytic stability at media pH suitable for IV administration. CZA rapidly converts into the active drug CZD in vivo. In a pharmacokinetic (PK) rat model, the exposure of active drug CZD after IV administration of the prodrug CZA was similar to or higher than that from the IV administration of CZD. The prodrug CZA is bioequivalent to or better than CZD in several preclinical infection models. CZA is likewise active upon its oral administration. To date, CZA has been evaluated in Phase 1 and Phase 2 clinical trials in the USA. It is advancing into further clinical studies including step-down therapy with in-hospital intravenous CZA administration followed by outpatient oral CZD treatment.

Discovery and Development of Antibacterial Agents: Fortuitous and Designed

Today, antibacterial drug resistance has turned into a significant public health issue. Repeated intake, suboptimal and/or unnecessary use of antibiotics, and, additionally, the transfer of resistance genes are the critical elements that make microorganisms resistant to conventional antibiotics. A substantial number of antibacterials that were successfully utilized earlier for prophylaxis and therapeutic purposes have been rendered inadequate due to this phenomenon. Therefore, the exploration of new molecules has become a continuous endeavour. Many such molecules are at various stages of investigation. A surprisingly high number of new molecules are currently in the stage of phase 3 clinical trials. A few new agents have been commercialized in the last decade. These include solithromycin, plazomicin, lefamulin, omadacycline, eravacycline, delafloxacin, zabofloxacin, finafloxacin, nemonoxacin, gepotidacin, zoliflodacin, cefiderocol, BAL30072, avycaz, zerbaxa, vabomere, relebactam, tedizolid, cadazolid, sutezolid, triclosan and afabiacin. This article aims to review the investigational and recently approved antibacterials with a focus on their structure, mechanisms of action/resistance, and spectrum of activity. Delving deep, their success or otherwise in various phases of clinical trials is also discussed while attributing the same to various causal factors.

In vitro Activity of Contezolid Against Methicillin-Resistant Staphylococcus aureus, Vancomycin-Resistant Enterococcus, and Strains With Linezolid Resistance Genes From China

Contezolid is a novel oxazolidinone, which exhibits potent activity against gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), and penicillin-resistant Streptococcus pneumoniae (PRSP). In this study, the in vitro activity of contezolid was compared with linezolid (LZD), tigecycline (TGC), teicoplanin (TEC), vancomycin (VA), daptomycin (DAP), and florfenicol (FFC) against MRSA and VRE strains isolated from China. Contezolid revealed considerable activity against MRSA and VRE isolates with MIC₉₀ values of 0.5 and 1.0 μg/mL, respectively. For VRE strains with different resistance genotypes, including vanA- and vanM-type strains, contezolid did not exhibit significantly differential antibacterial activity. Furthermore, the antimicrobial activity of contezolid is similar to or slightly better than that of linezolid against MRSA and VRE strains. Subsequently, the activity of contezolid was tested against strains carrying linezolid resistance genes, including Staphylococcus capitis carrying cfr gene and Enterococcus faecalis carrying optrA gene. The results showed that contezolid exhibited similar antimicrobial efficacy to linezolid against strains with linezolid resistance genes. In general, contezolid may have potential benefits to treat the infections caused by MRSA and VRE pathogens.

Contezolid: First Approval

Contezolid 康替唑胺 (Youxitai 优喜泰^®), an orally administered oxazolidinone antibacterial agent, is being developed by Shanghai MicuRx Pharmaceutical Co., Ltd. for the treatment of multidrug-resistant (MDR) Gram-positive bacterial infections, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci. In June 2021, it was approved by the National Medical Products Administration of China for the treatment of complicated skin and soft tissue infections (cSSTI), including, but not limited to, methicillin-susceptible S. aureus, MRSA, Streptococcus pyogenes and Streptococcus agalactiae. The recommended dosage of contezolid is 800 mg (i.e. two 400 mg tablets) every 12 h for 7–14 days. Contezolid is also undergoing clinical development for acute bacterial skin and skin structure infections (ABSSSI) in the USA, and for diabetic foot infections. This article summarizes the milestones in the development of contezolid leading to this first approval for the treatment of cSSTI.

Nonclinical Evaluation of Antibacterial Oxazolidinones Contezolid and Contezolid Acefosamil with Low Serotonergic Neurotoxicity

Linezolid, the principal oxazolidinone antibiotic for therapy of Gram-positive infections, is limited by its myelosuppression and monoamine oxidase (MAO) inhibition, with the latter manifested as serotonergic neurotoxicity. The oral oxazolidinone contezolid and its injectable prodrug contezolid acefosamil are developed to overcome the above limitations. Serotonergic profiles for contezolid in vitro and for orally administered contezolid acefosamil in rodents are reported. Contezolid exhibited 2- and 148-fold reduction over linezolid reversible inhibition of MAO-A and MAO-B human enzyme isoforms. In the mouse head-twitch model, contezolid acefosamil was devoid of neurotoxicity at supratherapeutic oral doses of 40, 80, and 120 mg/kg. In the rat tyramine challenge model, no significant increase in arterial blood pressure was observed for contezolid acefosamil up to 120 mg/kg oral dosing. In these tests, the comparator linezolid has elicited serotonergic responses. Thus, contezolid and contezolid acefosamil exhibited an attenuated propensity to induce MAO-related serotonergic neurotoxicity. The data support a continued clinical evaluation of these agents, with potential to expand oxazolidinone therapies to patient populations on concurrent selective serotonin reuptake inhibitor medications or where MAO inhibitors are contraindicated.