The Therapeutic Effect of Contezolid in Complex Intra-Abdominal Infections.

Purpose: In this paper, we observed the use of contezolid in patients with complex intra-abdominal infections in the intensive care unit of the Hepatobiliary Surgery department at the Chinese PLA General Hospital. Patients and Methods: The study collected data on complex intra-abdominal infections patients who received the antibiotic contezolid between January 2022 and April 2023. Results: Contezolid was administered to 12 patients, including 8 with severe acute pancreatitis, 3 with intra-abdominal infections following abdominal surgery, and 1 with complicated intra-abdominal infection after trauma. Gram-positive bacteria, such as Enterococcus faecium, Enterococcus casseliflavus, Staphylococcus capitis, and Staphylococcus haemo-lytica, were detected in 11 patients. All patients who received contezolid had previously been treated with other anti-Gram-positive agents, including linezolid for 9 patients, teicoplanin for 6 patients, and vancomycin for 3 patients. The treatment with contezolid began 20.0 (15.0, 34.5) days after admission and lasted for 8.0 (6.0, 10.0) days. At the end of the treatment, the patients' body temperature showed a significant decrease. After concomitant therapy, IL-6 levels decreased, and platelet count increased. Conclusion: Contezolid has shown potential in treating complex intra-abdominal infections caused by Gram-positive bacteria by reducing fever and inflammatory response.

Contezolid for the Treatment of Drug-Resistant Tuberculosis in China: A Clinical Case Series.

Background: Linezolid (LZD) is a cornerstone medication in the treatment of drug-resistant tuberculosis (DR-TB). However, it frequently triggers adverse effects such as bone marrow suppression, optic neuropathy, and peripheral neuropathy, all of which can impact treatment outcomes and prognosis. Contezolid (CZD), a novel oxazolidinone antibiotic, exhibits comparable antimicrobial efficacy against Mycobacterium tuberculosis as LZD, but with potentially enhanced safety profiles. Case Presentation: This report presents five cases (Cases 1-5) of LZD intolerance, wherein CZD served as an effective alternative treatment. In Cases 1-3, LZD administration resulted in bone marrow suppression, primarily manifested as anemia. Transitioning to CZD therapy led to a rise and stabilization of hemoglobin (HGB) levels in Cases 1-2, and a return to baseline values in Case 3. In Case 4, CZD treatment alleviated symptoms of LZD-induced peripheral neuritis, although complete resolution was not achieved, hinting at potential irreversibility of this type of peripheral neuropathy. In Case 5, direct CZD anti-TB therapy was initiated for recurrent leukopenia and neutropenia, resulting in no further severe myelosuppression and successful recovery. Conclusion: These case studies suggest that CZD could represent an effective and safe option for anti-TB therapy, especially for patients intolerant to LZD.

Successful Treatment of Intractable Tuberculous Peritonitis in a Woman with Chronic Kidney Allograft Dysfunction Using Contezolid Containing Regimen.

Tuberculosis(TB) is a serious infection that affects transplant recipients, particularly in high TB burden countries. Clinical presentation of these patients is atypical, and the care and management are frequently tricky as multi-drug interaction and intolerable adverse effects. Contezolid, a novel oxazolidinone antibacterial agent, had been demonstrated to be effective for TB in vitro and had been shown in some clinical cases with a more favorable safety profile than linezolid, the first-generation oxazolidinone, which had a commonly seen myelosuppression and neuropathy. Additionally, Contezolid has a unique metabolic mechanism that leads to less drug interaction. Here, we report a case of multi-system TB in a transplant recipient with chronic kidney allograft dysfunction. She was intolerant to most first and second-line anti-TB drugs and repeatedly developed ascites and nocturnal low-grade fever. She finally achieved good efficacy and safety results after enhanced anti-TB treatment with the addition of contezolid. Given the increased risk of TB in patients with organ transplantation and multi-drug interaction in patients with severe comorbidities, further clinical studies are needed to investigate the application and appropriate dosage of contezolid in patients with active TB.

Plasma Concentrations of Contezolid and Its Efficacy and Safety in Elderly Patients with Multidrug-Resistant Tuberculosis and Renal Insufficiency.

As a new generation of oxazolidinone antibacterial drugs, contezolid has been shown to have comparable or even stronger activity than linezolid and has a low risk of adverse reactions such as bone marrow suppression toxicity. However, there are currently very few clinical reports and pharmacokinetic data of contezolid on the anti-tuberculosis therapy. Therefore, we report a case study of the pharmacokinetic study of contezolid in elderly patients with renal insufficiency and tuberculosis. The patient's condition improved after receiving an anti-tuberculosis regimen containing contezolid, with significant absorption of pleural effusion and lung plaques and nodules reduced. During the treatment, the patients' platelet and white blood cell levels fluctuated within normal ranges, but hemoglobin levels significantly decreased and did not recover after discontinuation of contezolid. The trough concentration of contezolid and the concentration at 2, 4, 6, and 10 h after administration were 1.27µg/mL, 3.88µg/mL, 6.32µg/mL, 8.99µg/mL, and 3.14µg/mL, respectively. The plasma concentrations of bedaquiline and cycloserine during the treatment were also monitored. This study demonstrated the efficacy and safety of contezolid in the treatment of multidrug-resistant tuberculosis and analyzed its pharmacokinetic changes in elderly patients with renal insufficiency, providing a reference for the clinical use of contezolid.

New Oxazolidinones for Tuberculosis: Are Novel Treatments on the Horizon?

Multidrug-resistant tuberculosis (MDR-TB) is a global health concern. Standard treatment involves the use of linezolid, a repurposed oxazolidinone. It is associated with severe adverse effects, including myelosuppression and mitochondrial toxicity. As such, it is imperative to identify novel alternatives that are better tolerated but equally or more effective. Therefore, this review aims to identify and explore the novel alternative oxazolidinones to potentially replace linezolid in the management of TB. The keywords tuberculosis and oxazolidinones were searched in PubMed to identify eligible compounds. The individual drug compounds were then searched with the term tuberculosis to identify the relevant in vitro, in vivo and clinical studies. The search identified sutezolid, tedizolid, delpazolid, eperezolid, radezolid, contezolid, posizolid and TBI-223, in addition to linezolid. An additional search resulted in 32 preclinical and 21 clinical studies. All novel oxazolidinones except posizolid and eperezolid resulted in positive preclinical outcomes. Sutezolid and delpazolid completed early phase 2 clinical studies with better safety and equal or superior efficacy. Linezolid is expected to continue as the mainstay therapy, with renewed interest in drug monitoring. Sutezolid, tedizolid, delpazolid and TBI-223 displayed promising preliminary results. Further clinical studies would be required to assess the safety profiles and optimize the dosing regimens.

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.

Contezolid-Containing Regimen Successfully Treated Multiple Drug Resistance Mycobacterium Abscessus Complex Infection of Skin: A Case Report and Literature Review.

Background: In recent decades, there has been a substantial surge in the incidence of non-tuberculous Mycobacteria (NTM) infections. However, the diagnosis and management of NTM globally present significant challenges, particularly in cases involving Mycobacterium abscessus complex (MABC) infection where effective therapeutic options are limited. Case Presentation: We reported a 38-year-old female patient who was infected with MABC of skin due to "beauty needle" at a beauty salon, with mass on both cheeks, accompanied by redness, and pain, and some of them was ulcered and effused. Puncture pumping pus from bilateral cheek mass for many times, rinsed with "metronidazole", and oral "cephalosporin" treatment did not work. Therefore, she came to our hospital. MABC was detected in abscess paracentesis pus by nucleic acid mass spectrometry, and was proved by the cultured result of the pus. Thus, the patient was diagnosed as skin MABC infection, and anti-NTM treatment was taken. However, adverse reactions such as tinnitus, hepatotoxicity and neurovirulence occurred during the initial treatment. After adjusting to the contezolid-containing regimen, these adverse reactions improved. After nearly 6 months of treatment, the cheek mass was gradually reduced and the skin ruptures were gradually healed. Follow-up for 10 months showed that the patient's facial symptoms were significantly improved, and no drug-related adverse reactions happened. Conclusion: This was the first successful case of multiple drug resistance MABC infection of skin treated with contezolid-containing antibiotic management strategies, which exhibited remarkable efficacy and good safety in this intractable disease.

Population pharmacokinetic rationale for intravenous contezolid acefosamil followed by oral contezolid dosage regimens.

Contezolid is a novel oxazolidinone antibiotic with a promising safety profile. Oral contezolid and its intravenous (IV) prodrug contezolid acefosamil (CZA) are in development for treatment of diabetic foot and acute bacterial skin and skin structure infections (ABSSSI). The prodrug CZA is converted to active contezolid via intermediate MRX-1352. This study aimed to provide the pharmacokinetic rationale for safe, effective, and flexible dosage regimens with initial IV CZA followed by oral contezolid. We simultaneously modeled plasma concentrations from 110 healthy volunteers and 74 phase 2 patients with ABSSSI via population pharmacokinetics (using the importance sampling estimation algorithm), and optimized dosage regimens by Monte Carlo simulations. This included data on MRX-1352, contezolid, and its metabolite MRX-1320 from 66 healthy volunteers receiving intravenous CZA (150-2400 mg) for up to 28 days, and 74 patients receiving oral contezolid [800 mg every 12 h (q12h)] for 10 days. The apparent total clearance for 800 mg oral contezolid with food was 16.0 L/h (23.4% coefficient of variation) in healthy volunteers and 17.7 L/h (53.8%) in patients. CZA was rapidly converted to MRX-1352, which subsequently transformed to contezolid. The proposed dosage regimen used an IV CZA 2000 mg loading dose with 1000 mg IV CZA q12h as maintenance dose(s), followed by 800 mg oral contezolid q12h (with food). During each 24-h period, Monte Carlo simulations predicted this regimen to achieve consistent areas under the curve of 91.9 mg·h/L (range: 76.3-106 mg·h/L) under all scenarios. Thus, this regimen was predicted to reliably achieve efficacious contezolid exposures independent of timing of switch from IV CZA to oral contezolid.IMPORTANCEThis study provides the population pharmacokinetic rationale for the dosage regimen of the intravenous (IV) prodrug contezolid acefosamil (CZA) followed by oral contezolid. We developed the first integrated population model for the pharmacokinetics of the MRX-1352 intermediate prodrug, active contezolid, and its main metabolite MRX-1320 based on data from three clinical studies in healthy volunteers and phase 2 patients. The proposed regimen was predicted to reliably achieve efficacious contezolid exposures independent of timing of switch from IV CZA to oral contezolid.

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.

Preclinical toxicity evaluation of novel antibacterial contezolid acefosamil in rats and dogs.

Contezolid acefosamil (CZA) is an intravenous prodrug of oxazolidinone antibiotic contezolid (CZD). It is being developed to treat infections due to Gram-positive bacteria including multidrug-resistant pathogens, while addressing myelosuppression and neurotoxicity limitations associated with long-term use of this class of antibiotics. In vivo, CZA is rapidly deacylated into its first metabolite MRX-1352, which is then dephosphorylated to release active drug CZD. Four-week repeat-dose toxicity studies of intravenous CZA were conducted in Sprague-Dawley rats (40, 80, and 160/120 mg/kg/dose twice a day [BID]) and beagle dogs (25, 50, and 100/75 mg/kg/dose BID). The high doses administered to both rats and dogs were adjusted due to adverse effects including decreased body weight and food consumption. Additionally, a dose-dependent transient reduction in erythrocyte levels was recorded at the end of dosing phase. Importantly, no myelosuppressive reduction in platelet counts was observed, in contrast to the myelosuppression documented for standard-of-care oxazolidinone linezolid. The no-observed-adverse-effect level (NOAEL) of CZA was 80 and 25 mg/kg/dose BID in rats and dogs, respectively. Separately, 3-month neuropathological evaluation in Long-Evans rats (25, 37.5, and 50 mg/kg/dose, oral CZA, BID) demonstrated no neurotoxicity in the central, peripheral, and optical neurological systems. Toxicokinetic data from these studies revealed that CZD exposures at NOAELs were higher than or comparable with that for the intended clinical dose. These results confirm the favorable safety profile for CZA and support its clinical evaluation for long-term therapy of persistent Gram-positive infections, beyond the application for earlier oxazolidinones.

Case report: Successful treatment with contezolid in a patient with tuberculous meningitis who was intolerant to linezolid.

Tuberculous meningitis (TBM) is the most common form of central nervous system tuberculosis (TB) and the most severe form of extrapulmonary TB. It often presents with non-specific symptoms initially and has a high mortality and disability rate. With good central nervous system penetration, linezolid is recommended for treating drug-resistant, severe, or refractory tuberculous meningitis in China. Despite the benefits of linezolid on TBM treatment, the adverse effects of long-term therapy, such as myelosuppression, peripheral neuritis, and optic neuritis, are notable and can be severe and even life-threatening, leading to discontinuation and compromising treatment expectations. Contezolid is a novel oxazolidinone antibacterial agent approved by the National Medical Products Administration of China in 2021, which has a more favorable safety profile than linezolid in terms of myelosuppression and monoamine oxidase inhibition. Here we first report a case of TBM in a patient who was intolerant to antituberculosis treatment with linezolid and achieved good efficacy and safety results after the compassionate use of contezolid. Given the widespread use of linezolid in TB treatment and the potential risks for long-term use, multi-center prospective controlled clinical trials in TB and TBM patients are needed to investigate the appropriate use of contezolid further.

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.

Contezolid can replace linezolid in a novel combination with bedaquiline and pretomanid in a murine model of tuberculosis.

Contezolid is a new oxazolidinone with in vitro and in vivo activity against Mycobacterium tuberculosis comparable to that of linezolid. Pre-clinical and clinical safety studies suggest it may be less toxic than linezolid, making contezolid a potential candidate to replace linezolid in the treatment of drug-resistant tuberculosis. We evaluated the dose-ranging activity of contezolid, alone and in combination with bedaquiline and pretomanid, and compared it with linezolid at similar doses, in an established BALB/c mouse model of tuberculosis. Contezolid had an MIC of 1 µg/mL, similar to linezolid, and exhibited similar bactericidal activity in mice. Contezolid-resistant mutants selected in vitro had 32- to 64-fold increases in contezolid MIC and harbored mutations in the mce3R gene. These mutants did not display cross-resistance to linezolid. Our results indicate that contezolid has the potential to replace linezolid in regimens containing bedaquiline and pretomanid and likely other regimens.

A phase I study of the safety, tolerability, and pharmacokinetics of contezolid acefosamil after intravenous and oral administration in healthy Chinese subjects.

Contezolid acefosamil (also known as MRX-4), a prodrug of contezolid, is under development for treatment of multidrug-resistant Gram-positive bacterial infections. A phase I single ascending dose (SAD) and multiple-dose placebo-controlled study was conducted to assess the safety, tolerability, and pharmacokinetics (PK) of contezolid acefosamil in healthy Chinese subjects following intravenous (IV) and oral administration. Adverse events (AEs) and PK parameters were assessed appropriately. All subjects (n = 70) completed the trial. Overall, 67 cases of treatment-emergent adverse events (TEAEs) were observed in 49.1% (27 of 55) of the subjects receiving contezolid acefosamil. All TEAEs were mild in severity. No serious AEs or deaths were reported. After IV SAD (500-2,000 mg), the corresponding C max of the active drug contezolid increased from 1.95 ± 0.57 to 15.61 ± 4.88 mg/L, AUC0-inf from 40.25 ± 10.12 to 129.41 ± 38.30 h·mg/L, median T max from 2.00 to 2.75 h, and mean t 1/2 from 13.33 to 16.74 h. Plasma contezolid reached steady state on day 6 after multiple IV doses, with an accumulation ratio of 2.20-2.96. Oral SAD of 500 and 1,500 mg resulted in contezolid C max of 8.66 ± 2.60 and 37.10 ± 8.66 mg/L, AUC0-inf of 30.44 ± 7.33 and 162.36 ± 47.08 h·mg/L, and median T max of 2.50 and 2.98 h. Contezolid reached steady state on day 5 after multiple oral doses of 1,500 mg without significant accumulation. Contezolid C max and AUC0-inf increased with the dose of contezolid acefosamil. The good safety and PK profiles in this SAD and multiple-dose study can support further clinical development of contezolid acefosamil.

Clinical Utility of Contezolid-Containing Regimens in 25 Cases of Linezolid-Intolerable Tuberculosis Patients.

Objective: Linezolid is increasingly used in the treatment of multidrug-resistant (MDR) M. tuberculosis (TB) with good efficacy; however, its clinical use is limited by intolerable adverse events (AEs). This usually results in dose adjustment or even discontinuation. Contezolid is a new oxazolidinone antibiotic with in vitro antibacterial activity against MDR TB equivalent to linezolid, but its safety and efficacy in MDB TB treatment has not been established. Methods: We conducted a retrospective study on 25 TB patients who received both linezolid and contezolid in Beijing Chest Hospital from January 1, 2022, to January 31, 2023. All patients received linezolid-containing anti-TB regimen first and then switched to contezolid-containing regimens due to the intolerable linezolid-related AEs. Results: Most (68%, 17/25) of the patients were diagnosed with RR-TB or MDR-TB. A total of 30 AEs were reported in these patients. About 26.7% (8/30) of the AEs were Grade 3 (severe) in severity. After switching to contezolid-containing anti-TB regimens for at least 1 month, the linezolid-related AEs were resolved or improved in 90% of the cases. Clinical improvement was observed in all patients after treatment with contezolid-containing regimen, with negative results of sputum culture and/or smear for M. tuberculosis in 84% of the patients. Conclusion: Contezolid can be the first choice instead of linezolid to combine with other anti-TB drugs if necessary. Well-designed clinical trials are required to further confirm the safety and efficacy of contezolid in the treatment of TB patients.

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.

Antibacterial activity of the novel oxazolidinone contezolid (MRX-I) against Mycobacterium abscessus.

Objective: To evaluate contezolid (MRX-I) antibacterial activity against Mycobacterium abscessus in vitro and in vivo and to assess whether MRX-I treatment can prolong survival of infected zebrafish. Methods: MRX-I inhibitory activity against M. abscessus in vitro was assessed by injecting MRX-I into zebrafish infected with green fluorescent protein-labelled M. abscessus. Thereafter, infected zebrafish were treated with azithromycin (AZM), linezolid (LZD) or MRX-I then maximum tolerated concentrations (MTCs) of drugs were determined based on M. abscessus growth inhibition using one-way ANOVA. Linear trend analysis of CFU counts and fluorescence intensities (mean ± SE values) was performed to detect linear relationships between MRX-I, AZM and LZD concentrations and these parameters. Results: MRX-I anti-M. abscessus minimum inhibitory concentration (MIC) and MTC were 16 µg/mL and 15.6 µg/mL, respectively. MRX-I MTC-treated zebrafish fluorescence intensities were significantly lower than respective LZD group intensities (whole-body: 439040 ± 3647 vs. 509184 ± 23064, p < 0.01); head: 74147 ± 2175 vs. 95996 ± 8054, p < 0.05). As MRX-I concentration was increased from 0.488 µg/mL to 15.6 µg/mL, zebrafish whole-body, head and heart fluorescence intensities decreased. Statistically insignificant differences between the MRX-I MTC group survival rate (78.33%) vs. corresponding rates of the 62.5 µg/mL-treated AZM MTC group (88.33%, p > 0.05) and the 15.6 µg/mL-treated LZD MTC group (76.67%, p > 0.05) were observed. Conclusion: MRX-I effectively inhibited M. abscessus growth and prolonged zebrafish survival when administered to M. abscessus-infected zebrafish, thus demonstrating that MRX-I holds promise as a clinical treatment for human M. abscessus infections.

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.

Concentration of contezolid in cerebrospinal fluid and serum in a patient with tuberculous meningoencephalitis: A case report.

Central nervous system (CNS) tuberculosis (TB) is a devastating and often life-threatening disease caused by Mycobacterium tuberculosis. Contezolid, a new oxazolidinone, has demonstrated potent antimycobacterial activity in both in-vivo and in-vitro studies, with lower toxicity than linezolid. However, pharmacokinetic data are still not available for contezolid in the CNS of patients with CNS TB. This article reports the steady-state concentrations of contezolid in serum and cerebrospinal fluid (CSF) of a patient receiving contezolid as part of multi-drug treatment for tuberculous meningoencephalitis. At weeks 7 and 11 (7 h post-dose) after initiation of contezolid therapy, the serum concentrations of contezolid were 9.64 mg/L and 9.36 mg/L, respectively. In CSF, the observed concentrations of contezolid were 0.54 mg/L and 1.15 mg/L, respectively. The CSF:serum concentration ratios were 0.056 and 0.123 at weeks 7 and 11, respectively. The observed concentrations in CSF were above the minimum inhibitory concentration of contezolid against M. tuberculosis, and were close to the estimated serum unbound fraction of contezolid (10%), suggesting that unbound contezolid has high CSF permeability.