Systematic review of clofazimine for the treatment of drug-resistant tuberculosis

Assessing potential drug-drug interactions between clofazimine and other frequently used agents to treat drug-resistant tuberculosis

Clofazimine is included in drug regimens to treat rifampicin/drug-resistant tuberculosis (DR-TB), but there is little information about its interaction with other drugs in DR-TB regimens. We evaluated the pharmacokinetic interaction between clofazimine and isoniazid, linezolid, levofloxacin, and cycloserine, dosed as terizidone. Newly diagnosed adults with DR-TB at Klerksdorp/Tshepong Hospital, South Africa, were started on the then-standard treatment with clofazimine temporarily excluded for the initial 2 weeks. Pharmacokinetic sampling was done immediately before and 3 weeks after starting clofazimine, and drug concentrations were determined using validated liquid chromatography-tandem mass spectrometry assays. The data were interpreted with population pharmacokinetics in NONMEM v7.5.1 to explore the impact of clofazimine co-administration and other relevant covariates on the pharmacokinetics of isoniazid, linezolid, levofloxacin, and cycloserine. Clofazimine, isoniazid, linezolid, levofloxacin, and cycloserine data were available for 16, 27, 21, 21, and 6 participants, respectively. The median age and weight for the full cohort were 39 years and 52 kg, respectively. Clofazimine exposures were in the expected range, and its addition to the regimen did not significantly affect the pharmacokinetics of the other drugs except levofloxacin, for which it caused a 15% reduction in clearance. A posteriori power size calculations predicted that our sample sizes had 97%, 90%, and 87% power at P < 0.05 to detect a 30% change in clearance of isoniazid, linezolid, and cycloserine, respectively. Although clofazimine increased the area under the curve of levofloxacin by 19%, this is unlikely to be of great clinical significance, and the lack of interaction with other drugs tested is reassuring.

Molecular mechanisms of resistance and treatment efficacy of clofazimine and bedaquiline against Mycobacterium tuberculosis

Clofazimine (CFZ) and bedaquiline (BDQ) are currently used for the treatment of multidrug-resistant (MDR) Mycobacterium tuberculosis (Mtb) strains. In recent years, adding CFZ and BDQ to tuberculosis (TB) drug regimens against MDR Mtb strains has significantly improved treatment results, but these improvements are threatened by the emergence of MDR and extensively drug-resistant (XDR) Mtb strains. Recently, CFZ and BDQ have attracted much attention for their strong clinical efficacy, although very little is known about the mechanisms of action, drug susceptibility test (DST), resistance mechanisms, cross-resistance, and pharmacokinetics of these two drugs. In this current review, we provide recent updates on the mechanisms of action, DST, associated mutations with individual resistance and cross-resistance, clinical efficacy, and pharmacokinetics of CFZ and BDQ against Mtb strains. Presently, known mechanisms of resistance for CFZ and/or BDQ include mutations within the Rv0678, pepQ, Rv1979c, and atpE genes. The cross-resistance between CFZ and BDQ may reduce available MDR-/XDR-TB treatment options. The use of CFZ and BDQ for treatment in the setting of limited DST could allow further spread of drug resistance. The DST and resistance knowledge are urgently needed where CFZ and BDQ resistance do emerge. Therefore, an in-depth understanding of clinical efficacy, DST, cross-resistance, and pharmacokinetics for CFZ and BDQ against Mtb can provide new ideas for improving treatment outcomes, reducing mortality, preventing drug resistance, and TB transmission. Along with this, it will also help to develop rapid molecular diagnostic tools as well as novel therapeutic drugs for TB.

Micro-nanoemulsion and nanoparticle-assisted drug delivery against drug-resistant tuberculosis: recent developments

Tuberculosis (TB) is a major global health problem and the second most prevalent infectious killer after COVID-19. It is caused by Mycobacterium tuberculosis (Mtb) and has become increasingly challenging to treat due to drug resistance. The World Health Organization declared TB a global health emergency in 1993. Drug resistance in TB is driven by mutations in the bacterial genome that can be influenced by prolonged drug exposure and poor patient adherence. The development of drug-resistant forms of TB, such as multidrug resistant, extensively drug resistant, and totally drug resistant, poses significant therapeutic challenges. Researchers are exploring new drugs and novel drug delivery systems, such as nanotechnology-based therapies, to combat drug resistance. Nanodrug delivery offers targeted and precise drug delivery, improves treatment efficacy, and reduces adverse effects. Along with nanoscale drug delivery, a new generation of antibiotics with potent therapeutic efficacy, drug repurposing, and new treatment regimens (combinations) that can tackle the problem of drug resistance in a shorter duration could be promising therapies in clinical settings. However, the clinical translation of nanomedicines faces challenges such as safety, large-scale production, regulatory frameworks, and intellectual property issues. In this review, we present the current status, most recent findings, challenges, and limiting barriers to the use of emulsions and nanoparticles against drug-resistant TB.

Bedaquiline, Delamanid, Linezolid, Clofazimine, and Capreomycin MIC Distributions for Drug Resistance Mycobacterium tuberculosis in Shanghai, China

Background

New antituberculosis drugs have recently been approved for the treatment of multidrug-resistant tuberculosis TB (MDR-TB). We aimed to describe the distributions of bedaquiline, delamanid, linezolid, clofazimine, and capreomycin MIC values for M. tuberculosis.

Methods

M. tuberculosis clinical isolates were originally isolated from 2020 to 2021 from 1452 different pulmonary tuberculosis patients of the Shanghai Pulmonary Hospital in China. The drug susceptibility testing was performed using the Sensititre custom plates (SHTBMY) (TREK Diagnostic Systems, Thermo Fisher Scientific In., USA) consisting of a 96-well microtitre plate containing 4 (bedaquiline, delamanid, clofazimine, capreomycin) antimicrobial agents. MICs were determined for linezolid using a microdilution method.

Results

Based on the latest definitions, 156 (10.74%) were MDR-TB, 93 (6.40%) were pre-XDR-TB, and 27 (1.86%) were XDR-TB. The rate of BDQ resistance in cases of MDR-TB was 7.69%, while it was observed to be 10.75% in cases of pre-XDR-TB, and significantly higher at 37.04% in cases of XDR-TB. The lowest rate of drug resistance against M. tuberculosis was DLM (0.14%). For LZD, 11 (0.76%) clinical isolates were resistant, based on the CLSI breakpoint of 1μg/mL. The five strains with a MIC value of >32 for LZD resistance were XDR-TB isolates. Among all MDR, pre-XDR, and XDR isolates tested, LZD' MIC50 increased from 0.25 and 0.5 to 1μg/mL. The MIC90 value of LZD against XDR-TB isolates was 32μg/mL. For CFZ, six isolates with elevated MICs of ≥2μg/mL. CFZ's MIC50 and MIC90 values in all isolates were 0.12μg/mL and 0.25μg/mL, respectively.

Conclusion

The study findings indicate that BDQ, DLM, CFZ, and LZD may exhibited excellent in vitro activity against MDR-TB isolates. Detection of resistance to BDQ and LZD was alarming for XDR-TB isolates. It is necessary to perform universal drug sensitivity testing for M. tuberculosis, especially MDR-TB and XDR-TB patients.

Aryl hydrocarbon receptor is a tumor promoter in MYCN-amplified neuroblastoma cells through suppression of differentiation

Neuroblastoma is the most common extracranial solid tumor in children. MYCN amplification is detected in almost half of high-risk cases and is associated with poorly differentiated tumors, poor patient prognosis and poor response to therapy, including retinoids. We identify the aryl hydrocarbon receptor (AhR) as a transcription factor promoting the growth and suppressing the differentiation of MYCN-amplified neuroblastoma. A neuroblastoma specific AhR transcriptional signature reveals an inverse correlation of AhR activity with patients' outcome, suggesting AhR activity is critical for disease progression. AhR modulates chromatin structures, reducing accessibility to regions responsive to retinoic acid. Genetic and pharmacological inhibition of AhR results in induction of differentiation. Importantly, AhR antagonism with clofazimine synergizes with retinoic acid in inducing differentiation both in vitro and in vivo. Thus, we propose AhR as a target for MYCN-amplified neuroblastoma and that its antagonism, combined with current standard-of-care, may result in a more durable response in patients.

SARS-CoV-2 Syncytium under the Radar: Molecular Insights of the Spike-Induced Syncytia and Potential Strategies to Limit SARS-CoV-2 Replication

SARS-CoV-2 infection induces non-physiological syncytia when its spike fusogenic protein on the surface of the host cells interacts with the ACE2 receptor on adjacent cells. Spike-induced syncytia are beneficial for virus replication, transmission, and immune evasion, and contribute to the progression of COVID-19. In this review, we highlight the properties of viral fusion proteins, mainly the SARS-CoV-2 spike, and the involvement of the host factors in the fusion process. We also highlight the possible use of anti-fusogenic factors as an antiviral for the development of therapeutics against newly emerging SARS-CoV-2 variants and how the fusogenic property of the spike could be exploited for biomedical applications.

First report of Mycobacteria avium complex (Mycobacteria intracellulare) in a cat from Southeast Asia

Case summary

A 3-year-old castrated male domestic shorthaired cat, with indoor-outdoor access, was presented for chronic, progressive multinodular to generalised subcutaneous nodules covering much of its body. Previous medical treatment with doxycycline had been unhelpful. Fine-needle aspiration of the nodules revealed intra- and extracellular multibacillary negative staining rods in pyogranulomatous inflammation. Bacterial culture and susceptibility studies isolated Mycobacterium intracellulare, with zimine as the drug of choice for treatment. Initial triple therapy with rifampicin, azithromycin and pradofloxacin was ineffective, and was changed to triple therapy with clofazimine, clarithromycin and doxycycline once drug susceptibility was known, which was given for 3 months, after which long-term therapy with clofazimine and clarithromycin was continued.

Relevance and novel information

Slow growing M intracellulare, a member of the Mycobacterium avium complex (MAC), has never been reported to cause disease in cats from Singapore and, by extension, Southeast Asia. The infection in this patient resulted in subcutaneous nodules, which started on the face, then spread to the feet and much of the rest of its body. This is in contrast to that commonly reported for infection with M avium, which is also a member of MAC, and may not only present with similar signs in cats, but also progress to systemic spread. Susceptibility studies suggest clofazimine as the drug of choice when treating this infection, and this case supports its use as empirical therapy for veterinarians treating this disease in this region while awaiting culture and sensitivity results.

Treatment outcomes of multidrug-resistant tuberculosis patients receiving ambulatory treatment in Shenzhen, China: a retrospective cohort study

Background

WHO recommended multidrug-resistant tuberculosis (MDR-TB) should be treated mainly under ambulatory model, but outcome of ambulatory treatment of MDR-TB in China was little known.

Methods

The clinical data of 261 MDR-TB patients treated as outpatients in Shenzhen, China during 2010-2015 were collected and analyzed retrospectively.

Results

Of 261 MDR-TB patients receiving ambulatory treatment, 71.1% (186/261) achieved treatment success (cured or completed treatment), 0.4% (1/261) died during treatment, 11.5% (30/261) had treatment failure or relapse, 8.0% (21/261) were lost to follow-up, and 8.8% (23/261) were transferred out. The culture conversion rate at 6 months was 85.0%. Although 91.6% (239/261) of patients experienced at least one adverse event (AE), only 2% of AEs caused permanent discontinuation of one or more drugs. Multivariate analysis showed that previous TB treatment, regimens containing capreomycin and resistance to FQs were associated with poor outcomes, while experiencing three or more AEs was associated with good outcomes.

Conclusion

Good treatment success rates and early culture conversions were achieved with entirely ambulatory treatment of MDR-TB patients in Shenzhen, supporting WHO recommendations. Advantageous aspects of the local TB control program, including accessible and affordable second-line drugs, patient support, active monitoring and proper management of AEs and well-implemented DOT likely contributed to treatment success rates.

Encapsulation of Clofazimine by Cyclodextran: Preparation, Characterization, and In Vitro Release Properties

This study aimed to evaluate and compare the efficacy of cyclodextrans (CIs) and cyclodextrins (CDs) in improving the water solubility of a poorly water-soluble drug, clofazimine (CFZ). Among the evaluated CIs and CDs, CI-9 exhibited the highest percentage of drug inclusion and the highest solubility. Additionally, CI-9 showed the highest encapsulation efficiency, with a CFZ:CI-9 molar ratio of 0.2:1. SEM analysis indicated successful formation of inclusion complexes CFZ/CI and CFZ/CD, accounting for the rapid dissolution rate of the inclusion complex. Moreover, CFZ in CFZ/CI-9 demonstrated the highest drug release ratio, reaching up to 97%. CFZ/CI complexes were found to be an effective means of protecting the activity of CFZ against various environmental stresses, particularly UV irradiation, compared to free CFZ and CFZ/CD complexes. Overall, the findings provide valuable insights into designing novel drug delivery systems based on the inclusion complexes of CIs and CDs. However, further studies are needed to investigate the effects of these factors on the release properties and pharmacokinetics of encapsulated drugs in vivo, in order to ensure the safety and efficacy of these inclusion complexes. In conclusion, CI-9 is a promising candidate for drug delivery systems, and CFZ/CI complexes could be a potential formulation strategy for the development of stable and effective drug products.

Clofazimine Inhalation Suspension Demonstrates Promising Toxicokinetics in Canines for Treating Pulmonary Nontuberculous Mycobacteria Infection

Pulmonary nontuberculous mycobacteria (NTM) infection is recognized as a major global health concern due to its rising prevalence worldwide. As an opportunistic pathogen with increasing antibiotics resistance, prolonged systemic dosing with multiple antibiotics remains the primary treatment paradigm. These prolonged treatments, administered predominantly by oral or parenteral routes, often lead to systemic toxicity. A novel inhaled formulation of clofazimine may finally resolve issues of toxicity, thereby providing for improved NTM therapy. Clofazimine inhalation suspension was evaluated in canines to determine toxicity over 28 days of once-a-day dosing. The good laboratory practice (GLP) repeat dosing study evaluated low, mid, and high dosing (2.72 mg/kg and 2.95 mg/kg; 5.45 mg/kg and 5.91 mg/kg; and 10.87 mg/kg and 10.07 mg/kg, average male versus female dosing) of nebulized clofazimine over 30, 60, and 120 min using a jet nebulizer. Toxicokinetic analyses were performed on study days 29, 56, and 84. All three dose levels showed significant residual drug in lung tissue, demonstrating impressive lung loading and long lung residence. Drug concentrations in the lung remained well above the average NTM MIC at all time points, with measurable clofazimine levels at 28 and 56 days postdosing. In contrast, plasma levels of clofazimine were consistently measurable only through 14 days postdosing, with measurements below the limit of quantitation at 56 days postdosing. Clofazimine inhalation suspension may provide an effective therapy for the treatment of NTM infections through direct delivery of antibiotic to the lungs, overcoming the systemic toxicity seen in oral clofazimine treatment for NTM.

Vanoxerine kills mycobacteria through membrane depolarization and efflux inhibition

Mycobacterium tuberculosis is a deadly pathogen, currently the leading cause of death worldwide from a single infectious agent through tuberculosis infections. If the End TB 2030 strategy is to be achieved, additional drugs need to be identified and made available to supplement the current treatment regimen. In addition, drug resistance is a growing issue, leading to significantly lower treatment success rates, necessitating further drug development. Vanoxerine (GBR12909), a dopamine re-uptake inhibitor, was recently identified as having anti-mycobacterial activity during a drug repurposing screening effort. However, its effects on mycobacteria were not well characterized. Herein, we report vanoxerine as a disruptor of the membrane electric potential, inhibiting mycobacterial efflux and growth. Vanoxerine had an undetectable level of resistance, highlighting the lack of a protein target. This study suggests a mechanism of action for vanoxerine, which will allow for its continued development or use as a tool compound.

Clofazimine as a comparator for preclinical efficacy evaluations of experimental therapeutics against pulmonary M. abscessus infection in mice

Mycobacteroides abscessus (Mab, also known as Mycobacterium abscessus) can cause chronic pulmonary disease in the setting of structural lung conditions. Current treatment recommendations require at least one year of daily therapy with repurposed antibiotics. Yet these therapies are often ineffective and associated with significant adverse events. To address this challenge, research efforts are underway to develop new antibiotics and regimens. During the preclinical phase of treatment development, experimental agents require testing and comparison alongside positive controls that are known agents with clinical history. As there are no FDA approved treatments for this indication, here, we have considered repurposed antibiotics currently included in the recommendation for treating Mab disease as candidates for selection of an ideal standard comparator that can serve as a positive control in preclinical studies. Clofazimine meets the criteria for an ideal positive control as it can be administered via the least invasive route, requires only once-daily dosing, is well tolerated, and is widely available in high purity from independent sources. Using a mouse model of pulmonary Mab disease, we assessed for ideal dosages of clofazimine in C3HeB/FeJ and BALB/c mice in a six-week treatment window. Clofazimine, 25 mg/kg, once daily, produced desired reduction in Mab burden in the lungs of C3HeB/FeJ and BALB/c mice. Based on these findings, we conclude that clofazimine meets the criteria for a positive control comparator in mice for use in preclinical efficacy assessments of agents for treatment of Mab pulmonary disease. Although not included in the current standard-of-care for treating Mab disease, rifabutin, 20 mg/kg, also produced desired reduction in Mab lung burden in C3HeB/FeJ mice but not in BALB/c mice. IMPORTANCE: Mycobacteroides abscessus can cause life-threatening infections in patients with chronic lung conditions. New treatments are needed as cure rate using existing drugs is low. During pre-clinical phase of treatment development, it is important to compare the efficacy of the experimental drug against existing ones with known history. Here, we demonstrate that clofazimine, one of the antibiotics repurposed for treating Mab disease, can serve as a positive control comparator for efficacy assessments of experimental drugs and regimens to treat M. abscessus disease in mice.

The role of polyamine metabolism in remodeling immune responses and blocking therapy within the tumor immune microenvironment

The study of metabolism provides important information for understanding the biological basis of cancer cells and the defects of cancer treatment. Disorders of polyamine metabolism is a common metabolic change in cancer. With the deepening of understanding of polyamine metabolism, including molecular functions and changes in cancer, polyamine metabolism as a new anti-cancer strategy has become the focus of attention. There are many kinds of polyamine biosynthesis inhibitors and transport inhibitors, but not many drugs have been put into clinical application. Recent evidence shows that polyamine metabolism plays essential roles in remodeling the tumor immune microenvironment (TIME), particularly treatment of DFMO, an inhibitor of ODC, alters the immune cell population in the tumor microenvironment. Tumor immunosuppression is a major problem in cancer treatment. More and more studies have shown that the immunosuppressive effect of polyamines can help cancer cells to evade immune surveillance and promote tumor development and progression. Therefore, targeting polyamine metabolic pathways is expected to become a new avenue for immunotherapy for cancer.

Progressive Host-Directed Strategies to Potentiate BCG Vaccination Against Tuberculosis

The pursuit to improve the TB control program comprising one approved vaccine, M. bovis Bacille Calmette-Guerin (BCG) has directed researchers to explore progressive approaches to halt the eternal TB pandemic. Mycobacterium tuberculosis (M.tb) was first identified as the causative agent of TB in 1882 by Dr. Robert Koch. However, TB has plagued living beings since ancient times and continues to endure as an eternal scourge ravaging even with existing chemoprophylaxis and preventive therapy. We have scientifically come a long way since then, but despite accessibility to the standard antimycobacterial antibiotics and prophylactic vaccine, almost one-fourth of humankind is infected latently with M.tb. Existing therapeutics fail to control TB, due to the upsurge of drug-resistant strains and increasing incidents of co-infections in immune-compromised individuals. Unresponsiveness to established antibiotics leaves patients with no therapeutic possibilities. Hence the search for an efficacious TB immunization strategy is a global health priority. Researchers are paving the course for efficient vaccination strategies with the radically advanced operation of core principles of protective immune responses against M.tb. In this review; we have reassessed the progression of the TB vaccination program comprising BCG immunization in children and potential stratagems to reinforce BCG-induced protection in adults.

Adapting Clofazimine for Treatment of Cutaneous Tuberculosis by Using Self-Double-Emulsifying Drug Delivery Systems

Although chemotherapeutic treatment regimens are currently available, and considerable effort has been lavished on the development of new drugs for the treatment of tuberculosis (TB), the disease remains deeply intractable and widespread. This is due not only to the nature of the life cycle and extraordinarily disseminated habitat of the causative pathogen, principally Mycobacterium tuberculosis (Mtb), in humans and the multi-drug resistance of Mtb to current drugs, but especially also to the difficulty of enabling universal treatment of individuals, immunocompromised or otherwise, in widely differing socio-economic environments. For the purpose of globally eliminating TB by 2035, the World Health Organization (WHO) introduced the "End-TB" initiative by employing interventions focusing on high impact, integrated and patient-centered approaches, such as individualized therapy. However, the extraordinary shortfall in stipulated aims, for example in actual treatment and in TB preventative treatments during the period 2018-2022, latterly and greatly exacerbated by the COVID-19 pandemic, means that even greater pressure is now placed on enhancing our scientific understanding of the disease, repurposing or repositioning old drugs and developing new drugs as well as evolving innovative treatment methods. In the specific context of multidrug resistant Mtb, it is furthermore noted that the incidence of extra-pulmonary TB (EPTB) has significantly increased. This review focusses on the potential of utilizing self-double-emulsifying drug delivery systems (SDEDDSs) as topical drug delivery systems for the dermal route of administration to aid in treatment of cutaneous TB (CTB) and other mycobacterial infections as a prelude to evaluating related systems for more effective treatment of CTB and other mycobacterial infections at large. As a starting point, we consider here the possibility of adapting the highly lipophilic riminophenazine clofazimine, with its potential for treatment of multi-drug resistant TB, for this purpose. Additionally, recently reported synergism achieved by adding clofazimine to first-line TB regimens signifies the need to consider clofazimine. Thus, the biological effects and pharmacology of clofazimine are reviewed. The potential of plant-based oils acting as emulsifiers, skin penetration enhancers as well as these materials behaving as anti-microbial components for transporting the incorporated drug are also discussed.

Single-Cell Proteomics and Tumor RNAseq Identify Novel Pathways Associated With Clofazimine Sensitivity in PI- and IMiD- Resistant Myeloma, and Putative Stem-Like Cells

Multiple myeloma (MM) is an incurable plasma cell malignancy with dose-limiting toxicities and inter-individual variation in response/resistance to the standard-of-care/primary drugs, proteasome inhibitors (PIs), and immunomodulatory derivatives (IMiDs). Although newer therapeutic options are potentially highly efficacious, their costs outweigh the effectiveness. Previously, we have established that clofazimine (CLF) activates peroxisome proliferator-activated receptor-γ, synergizes with primary therapies, and targets cancer stem-like cells (CSCs) in drug-resistant chronic myeloid leukemia (CML) patients. In this study, we used a panel of human myeloma cell lines as in vitro model systems representing drug-sensitive, innate/refractory, and clonally-derived acquired/relapsed PI- and cereblon (CRBN)-negative IMiD-resistant myeloma and bone marrow-derived CD138+ primary myeloma cells obtained from patients as ex vivo models to demonstrate that CLF shows significant cytotoxicity against drug-resistant myeloma as single-agent and in combination with PIs and IMiDs. Next, using genome-wide transcriptome analysis (RNA-sequencing), single-cell proteomics (CyTOF; Cytometry by time-of-flight), and ingenuity pathway analysis (IPA), we identified novel pathways associated with CLF efficacy, including induction of ER stress, autophagy, mitochondrial dysfunction, oxidative phosphorylation, enhancement of downstream cascade of p65-NFkB-IRF4-Myc downregulation, and ROS-dependent apoptotic cell death in myeloma. Further, we also showed that CLF is effective in killing rare refractory subclones like side populations that have been referred to as myeloma stem-like cells. Since CLF is an FDA-approved drug and also on WHO's list of safe and effective essential medicines, it has strong potential to be rapidly re-purposed as a safe and cost-effective anti-myeloma drug.

Screening for inhibitors against SARS-CoV-2 and its variants

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to evolve, generating new variants that pose a threat to global health; therefore, it is imperative to obtain safe and broad-spectrum antivirals against SARS-CoV-2 and its variants. To this end, we screened compounds for their ability to inhibit viral entry, which is a critical step in virus infection. Twenty compounds that have been previously reported to inhibit SARS-CoV-2 replication were tested by using pseudoviruses containing the spike protein from the original strain (SARS-CoV-2-WH01). The cytotoxicity of these compounds was determined. Furthermore, we identified six compounds with strong antagonistic activity against the WH01 pseudovirus, and low cytotoxicity was identified. These compounds were then evaluated for their efficacy against pseudoviruses expressing the spike protein from B.1.617.2 (Delta) and B.1.1.529 (Omicron), the two most prevalent circulating strains. These assays demonstrated that two phenothiazine compounds, trifluoperazine 2HCl and thioridazine HCl, inhibit the infection of Delta and Omicron pseudoviruses. Finally, we discovered that these two compounds were highly effective against authentic SARS-CoV-2 viruses, including the WH01, Delta, and Omicron strains. Our study identified potential broad-spectrum SARS-CoV-2 inhibitors and provided insights into the development of novel therapeutics.

Recent advances in developing small-molecule inhibitors against SARS-CoV-2

The COVID-19 pandemic caused by the novel SARS-CoV-2 virus has caused havoc across the entire world. Even though several COVID-19 vaccines are currently in distribution worldwide, with others in the pipeline, treatment modalities lag behind. Accordingly, researchers have been working hard to understand the nature of the virus, its mutant strains, and the pathogenesis of the disease in order to uncover possible drug targets and effective therapeutic agents. As the research continues, we now know the genome structure, epidemiological and clinical features, and pathogenic mechanism of SARS-CoV-2. Here, we summarized the potential therapeutic targets involved in the life cycle of the virus. On the basis of these targets, small-molecule prophylactic and therapeutic agents have been or are being developed for prevention and treatment of SARS-CoV-2 infection.

Investigation of Clofazimine Resistance and Genetic Mutations in Drug-Resistant Mycobacterium tuberculosis Isolates

Recently, as clofazimine (CFZ) showed a good therapeutic effect in treating multi-drug-resistant tuberculosis (MDR-TB), the anti-tuberculosis activity and resistance were re-focused. Here, we investigated the CFZ resistance and genetic mutations of drug-resistant Mycobacterium tuberculosis (DR-Mtb) isolates to improve the diagnosis and treatment of drug-resistant TB patients. The minimal inhibitory concentration (MIC) of CFZ was examined by resazurin microtiter assay (REMA) with two reference strains and 122 clinical isolates from Korea. The cause of CFZ resistance was investigated in relation to the therapeutic history of patients. Mutations of Rv0678, Rv1979c and pepQ of CFZ resistant isolates were analyzed by PCR and DNA sequencing. The rate of CFZ resistance with MIC > 1 mg/L was 4.1% in drug-resistant Mtb isolates. The cause of CFZ resistance was not related to treatment with CFZ or bedaquiline. A CFZ susceptibility test should be conducted regardless of dugs use history. The four novel mutation sites were identified in the Rv0678 and pepQ genes related to CFZ resistance in this study.

Application of Next Generation Sequencing for Diagnosis and Clinical Management of Drug-Resistant Tuberculosis: Updates on Recent Developments in the Field

The World Health Organization’s End TB Strategy prioritizes universal access to an early diagnosis and comprehensive drug susceptibility testing (DST) for all individuals with tuberculosis (TB) as a key component of integrated, patient-centered TB care. Next generation whole genome sequencing (WGS) and its associated technology has demonstrated exceptional potential for reliable and comprehensive resistance prediction for Mycobacterium tuberculosis isolates, allowing for accurate clinical decisions. This review presents a descriptive analysis of research describing the potential of WGS to accelerate delivery of individualized care, recent advances in sputum-based WGS technology and the role of targeted sequencing for resistance detection. We provide an update on recent research describing the mechanisms of resistance to new and repurposed drugs and the dynamics of mixed infections and its potential implication on TB diagnosis and treatment. Whilst the studies reviewed here have greatly improved our understanding of recent advances in this arena, it highlights significant challenges that remain. The wide-spread introduction of new drugs in the absence of standardized DST has led to rapid emergence of drug resistance. This review highlights apparent gaps in our knowledge of the mechanisms contributing to resistance for these new drugs and challenges that limit the clinical utility of next generation sequencing techniques. It is recommended that a combination of genotypic and phenotypic techniques is warranted to monitor treatment response, curb emerging resistance and further dissemination of drug resistance.

Characterization of Clofazimine as a Potential Substrate of Drug Transporter

In this study, we explored clofazimine (CFZ) as a potential substrate of uptake and efflux transporters that might be involved in CFZ disposition, using transporter gene overexpressing cell lines in vitro. The intracellular concentrations of CFZ were significantly increased in the presence of selective inhibitors of P-gp and BCRP, which include verapamil, cyclosporine-A, PSC-833, quinidine, Ko143, and daunorubicin. In a bidirectional transport assay using transwell cultures of cell lines overexpressing P-gp and BCRP, the mean efflux ratios of CFZ were found to be 4.17 ± 0.63 and 3.37 ± 1.2, respectively. The K_m and maximum rate of uptake (V_max) were estimated to be 223.3 ± 14.73 μM and 548.8 ± 87.15 pmol/min/mg protein for P-gp and 381.9 ± 25.07 μM and 5.8 ± 1.22 pmol/min/mg protein for BCRP, respectively. Among the uptake transporters screened, the CFZ uptake rate was increased 1.93 and 3.09-fold in HEK293 cell lines overexpressing OAT1 and OAT3, respectively, compared to the control cell lines, but no significant uptake was observed in cell lines overexpressing OCT1, OCT2, OATP1B1, OATP1B3, OATP2B1, or NTCP. Both OAT1- and OAT3-mediated uptake was inhibited by the selective inhibitors diclofenac, probenecid, and butanesulfonic acid. The K_m and V_max values of CFZ were estimated to be 0.63 ± 0.15 μM and 8.23 ± 1.03 pmol/min/mg protein, respectively, for OAT1 and 0.47 ± 0.1 μM and 17.81 ± 2.19 pmol/min/mg protein, respectively, for OAT3. These findings suggest that CFZ is a novel substrate of BCRP, OAT1, and OAT3 and a known substrate of P-gp in vitro.

Pyrazine and Phenazine Heterocycles: Platforms for Total Synthesis and Drug Discovery

There are numerous pyrazine and phenazine compounds that demonstrate biological activities relevant to the treatment of disease. In this review, we discuss pyrazine and phenazine agents that have shown potential therapeutic value, including several clinically used agents. In addition, we cover some basic science related to pyrazine and phenazine heterocycles, which possess interesting reactivity profiles that have been on display in numerous cases of innovative total synthesis approaches, synthetic methodologies, drug discovery efforts, and medicinal chemistry programs. The majority of this review is focused on presenting instructive total synthesis and medicinal chemistry efforts of select pyrazine and phenazine compounds, and we believe these incredible heterocycles offer promise in medicine.

MDR Tuberculosis Treatment

Multidrug-resistant (MDR) tuberculosis (TB), resistant to isoniazid and rifampicin, continues to be one of the most important threats to controlling the TB epidemic. Over the last few years, there have been promising pharmacological advances in the paradigm of MDR TB treatment: new and repurposed drugs have shown excellent bactericidal and sterilizing activity against Mycobacterium tuberculosis and several all-oral short regimens to treat MDR TB have shown promising results. The purpose of this comprehensive review is to summarize the most important drugs currently used to treat MDR TB, the recommended regimens to treat MDR TB, and we also summarize new insights into the treatment of patients with MDR TB.

The pharmacotherapeutic management of pulmonary tuberculosis: an update of the state-of-the-art

INTRODUCTION

Pulmonary tuberculosis (TB) remains an important global health challenge of the 21st century, and the emerging resistance against anti-TB drugs is still a growing concern. And while there was a significant cumulative reduction in the incidence of TB between 2015 and 2019, 2.8% of all TB cases in 2019 were reported to be drug resistant.

AREA COVERED

This review provides the reader with an update on pharmacotherapy for patients with TB susceptible or resistant to drug therapy. The authors also include promising investigational drugs herein. Finally, the authors share with the reader their expert opinions on the current state of the art and their future perspectives.

EXPERT OPINION

The current pharmacotherapeutic management aims to enhance favorable treatment outcomes and reduce treatment-related adverse events. One approach is to use shorter and all-oral regimens for eligible patients. Traditional longer regimens for most patients are also optimized to lower incidence of treatment failure and serious adverse events.

Prevalence of Mycobacterium tuberculosis resistant to bedaquiline and delamanid in China

OBJECTIVES

The new antituberculous drugs delamanid and bedaquiline form the last line of defence against drug-resistant tuberculosis (TB). Understanding the background prevalence of resistance to new drugs can help predict the lifetime of these drugs' effectiveness and inform regimen design.

METHODS

Mycobacterium tuberculosis without prior exposure to novel anti-TB drugs were analysed retrospectively. Drug susceptibility testing for bedaquiline, delamanid, linezolid, clofazimine and widely used first- and second-line anti-TB drugs was performed. All TB isolates with resistance to new or repurposed drugs were subjected to whole-genome sequencing to explore the molecular characteristics of resistance and to perform phylogenetic analysis.

RESULTS

Overall, resistance to delamanid, bedaquiline, linezolid and clofazimine was observed in 0.7% (11/1603), 0.4% (6/1603), 0.4% (7/1603) and 0.4% (6/1603) of TB isolates, respectively. Moreover, 1.0% (1/102), 2.9% (3/102), 3.9% (4/102) and 1.0% (1/102) of multidrug-resistant TB (MDR-TB) were resistant to bedaquiline, delamanid, linezolid and clofazimine, respectively. Whereas 22.2% (2/9) of extensively-drug resistant tuberculosis (XDR-TB) isolates were resistant to both delamanid and linezolid, and none was resistant to bedaquiline or clofazimine. Phylogenetic analysis showed that recent transmission occurred in two XDR-TB with additional resistance to delamanid and linezolid. None known gene mutation associated with delamanid resistance was detected. All four isolates with cross-resistance to bedaquiline and clofazimine had a detected gene mutation in Rv0678. Three of five strains with linezolid resistance had a detected gene mutation in rplC.

CONCLUSION

Detection of resistance to new anti-TB drugs emphasises the pressing need for intensive surveillance for such resistance before their wide usage.

Clofazimine as a Treatment for Multidrug-Resistant Tuberculosis: A Review

Multidrug-resistant tuberculosis (MDR-TB) is an infectious disease caused by Mycobacterium tuberculosis which is resistant to at least isoniazid and rifampicin. This disease is a worldwide threat and complicates the control of tuberculosis (TB). Long treatment duration, a combination of several drugs, and the adverse effects of these drugs are the factors that play a role in the poor outcomes of MDR-TB patients. There have been many studies with repurposed drugs to improve MDR-TB outcomes, including clofazimine. Clofazimine recently moved from group 5 to group B of drugs that are used to treat MDR-TB. This drug belongs to the riminophenazine class, which has lipophilic characteristics and was previously discovered to treat TB and approved for leprosy. This review discusses the role of clofazimine as a treatment component in patients with MDR-TB, and the drug’s properties. In addition, we discuss the efficacy, safety, and tolerability of clofazimine for treating MDR-TB. This study concludes that the clofazimine-containing regimen has better efficacy compared with the standard one and is also well-tolerated. Clofazimine has the potential to shorten the duration of MDR-TB treatment.

Clofazimine broadly inhibits coronaviruses including SARS-CoV-2

The COVID-19 pandemic is the third outbreak this century of a zoonotic disease caused by a coronavirus, following the emergence of severe acute respiratory syndrome (SARS) in 2003¹ and Middle East respiratory syndrome (MERS) in 2012². Treatment options for coronaviruses are limited. Here we show that clofazimine-an anti-leprosy drug with a favourable safety profile³-possesses inhibitory activity against several coronaviruses, and can antagonize the replication of SARS-CoV-2 and MERS-CoV in a range of in vitro systems. We found that this molecule, which has been approved by the US Food and Drug Administration, inhibits cell fusion mediated by the viral spike glycoprotein, as well as activity of the viral helicase. Prophylactic or therapeutic administration of clofazimine in a hamster model of SARS-CoV-2 pathogenesis led to reduced viral loads in the lung and viral shedding in faeces, and also alleviated the inflammation associated with viral infection. Combinations of clofazimine and remdesivir exhibited antiviral synergy in vitro and in vivo, and restricted viral shedding from the upper respiratory tract. Clofazimine, which is orally bioavailable and comparatively cheap to manufacture, is an attractive clinical candidate for the treatment of outpatients and-when combined with remdesivir-in therapy for hospitalized patients with COVID-19, particularly in contexts in which costs are an important factor or specialized medical facilities are limited. Our data provide evidence that clofazimine may have a role in the control of the current pandemic of COVID-19 and-possibly more importantly-in dealing with coronavirus diseases that may emerge in the future.

A Review of Clinical Pharmacokinetic and Pharmacodynamic Relationships and Clinical Implications for Drugs Used to Treat Multi-drug Resistant Tuberculosis

Multidrug-resistant tuberculosis (MDR-TB) is becoming a global health crisis. The World Health Organization has released new guidelines for the use of tuberculosis-active drugs for the treatment of patients with MDR-TB. Despite documented activity against tuberculosis isolates, doses and exposure targets are yet to be optimized. Our objective was therefore to review the clinical pharmacokinetic and pharmacodynamic literature pertaining to drugs recommended to treat MDR-TB and to identify target areas for future research. To date, published research is limited but studies were identified that evaluated the pharmacokinetics and pharmacodynamics of these drugs. Exposure targets were assessed and summarized for each drug. Exposure-based targets (e.g., area under the concentration curve/minimum inhibitory concentration) appear to be most commonly associated with predicting drug efficacy. Dose variation studies based on these targets were largely inconclusive. Future research should focus on determining the risks and benefits of dose optimization to meet exposure targets and improve patient outcomes. The role of therapeutic drug monitoring also remains yet to be confirmed, both from a clinical perspective as well as a resource allocation perspective in regions where MDR-TB is active.

Drug Delivery Systems on Leprosy Therapy: Moving Towards Eradication?

Leprosy disease remains an important public health issue as it is still endemic in several countries. Mycobacterium leprae, the causative agent of leprosy, presents tropism for cells of the reticuloendothelial and peripheral nervous system. Current multidrug therapy consists of clofazimine, dapsone and rifampicin. Despite significant improvements in leprosy treatment, in most programs, successful completion of the therapy is still sub-optimal. Drug resistance has emerged in some countries. This review discusses the status of leprosy disease worldwide, providing information regarding infectious agents, clinical manifestations, diagnosis, actual treatment and future perspectives and strategies on targets for an efficient targeted delivery therapy.

Physicochemical properties and Mycobacterium tuberculosis transporters: keys to efficacious antitubercular drugs?

Securing novel, safe, and effective medicines to treat Mycobacterium tuberculosis remains an elusive goal, particularly influenced by the largely impervious Mtb envelope that limits exposure and thus efficacy of inhibitors at their cellular and periplasmic targets. The impact of physicochemical properties on pharmacokinetic parameters that govern oral absorption and exposure at sites of infection is considered alongside how these properties influence penetration of the Mtb envelope, with the likely influence of transporter proteins. The findings are discussed to benchmark current drugs and the emerging pipeline, whilst considering tactics for future rational and targeted design strategies, based around emerging data on Mtb transporters and their structures and functions.

Clofazimine is a broad-spectrum coronavirus inhibitor that antagonizes SARS-CoV-2 replication in primary human cell culture and hamsters

COVID-19 pandemic is the third zoonotic coronavirus (CoV) outbreak of the century after severe acute respiratory syndrome (SARS) in 2003 and Middle East respiratory syndrome (MERS) since 2012. Treatment options for CoVs are largely lacking. Here, we show that clofazimine, an anti-leprosy drug with a favorable safety and pharmacokinetics profile, possesses pan-coronaviral inhibitory activity, and can antagonize SARS-CoV-2 replication in multiple in vitro systems, including the human embryonic stem cell-derived cardiomyocytes and ex vivo lung cultures. The FDA-approved molecule was found to inhibit multiple steps of viral replication, suggesting multiple underlying antiviral mechanisms. In a hamster model of SARS-CoV-2 pathogenesis, prophylactic or therapeutic administration of clofazimine significantly reduced viral load in the lung and fecal viral shedding, and also prevented cytokine storm associated with viral infection. Additionally, clofazimine exhibited synergy when administered with remdesivir. Since clofazimine is orally bioavailable and has a comparatively low manufacturing cost, it is an attractive clinical candidate for outpatient treatment and remdesivir-based combinatorial therapy for hospitalized COVID-19 patients, particularly in developing countries. Taken together, our data provide evidence that clofazimine may have a role in the control of the current pandemic SARS-CoV-2, endemic MERS-CoV in the Middle East, and, possibly most importantly, emerging CoVs of the future.

Adverse drug reactions & drug interactions in MDR-TB patients

Multiple drugs taken for long duration in tuberculosis (TB) treatment, especially drug resistant TB (DR-TB), may produce adverse drug reactions (ADRs). Although any anti-TB drug can cause ADRs, but these are more common with drugs used for treatment of DR-TB. However, most of ADRs with these drugs are mild or moderate and can be managed if adequate supervision and monitoring is done. However, few ADRs can be severe or potentially life-threatening and may require removal of the offending drug(s). TB patients having comorbidities and on treatment for them may experience drug interaction with anti TB drugs and may require dose modification or change of drug. For a good TB treatment outcome patient's compliance should be ensured, and adverse events and drug interactions should be appropriately addressed by the clinicians. This article outlines the majority of the possible ADRs to anti-TB drugs used for management of DR-TB and their common drug interactions with practical recommendations to identify the possible drug(s) responsible and the most adequate management in each situation.

Novel Administration of Clofazimine for the Treatment of Mycobacterium avium Infection

Clofazimine has demonstrated in vitro activity against many nontuberculous mycobacteria. We present the case of a woman with cystic fibrosis who developed disseminated macrolide-resistant Mycobacterium avium infection following lung transplantation treated in part with clofazimine. We describe the novel administration of clofazimine via gastrostomy tube.

Drug Effect of Clofazimine on Persisters Explains an Unexpected Increase in Bacterial Load in Patients

Antituberculosis (anti-TB) drug development is dependent on informative trials to secure the development of new antibiotics and combination regimens. Clofazimine (CLO) and pyrazinamide (PZA) are important components of recommended standard multidrug treatments of TB. Paradoxically, in a phase IIa trial aiming to define the early bactericidal activity (EBA) of CLO and PZA monotherapy over the first 14 days of treatment, no significant drug effect was demonstrated for the two drugs using traditional statistical analysis.

Antituberculosis (anti-TB) drug development is dependent on informative trials to secure the development of new antibiotics and combination regimens. Clofazimine (CLO) and pyrazinamide (PZA) are important components of recommended standard multidrug treatments of TB. Paradoxically, in a phase IIa trial aiming to define the early bactericidal activity (EBA) of CLO and PZA monotherapy over the first 14 days of treatment, no significant drug effect was demonstrated for the two drugs using traditional statistical analysis. Using a model-based analysis, we characterized the statistically significant exposure-response relationships for both drugs that could explain the original findings of an increase in the numbers of CFU with CLO treatment and no effect with PZA. Sensitive analyses are crucial for exploring drug effects in early clinical trials to make the right decisions for advancement to further development. We propose that this quantitative semimechanistic approach provides a rational framework for analyzing phase IIa EBA studies and can accelerate anti-TB drug development.

Drug-associated adverse events in the treatment of multidrug-resistant tuberculosis: an individual patient data meta-analysis

BACKGROUND

Treatment of multidrug-resistant tuberculosis requires long-term therapy with a combination of multiple second-line drugs. These drugs are associated with numerous adverse events that can cause severe morbidity, such as deafness, and in some instances can lead to death. Our aim was to estimate the absolute and relative frequency of adverse events associated with different tuberculosis drugs to provide useful information for clinicians and tuberculosis programmes in selecting optimal treatment regimens.

METHODS

We did a meta-analysis using individual-level patient data that were obtained from studies that reported adverse events that resulted in permanent discontinuation of anti-tuberculosis medications. We used a database created for our previous meta-analysis of multidrug-resistant tuberculosis treatment and outcomes, for which we did a systematic review of literature published between Jan 1, 2009, and Aug 31, 2015 (updated April 15, 2016), and requested individual patient-level information from authors. We also considered for this analysis studies contributing patient-level data in response to a public call made by WHO in 2018. Meta-analysis for proportions and arm-based network meta-analysis were done to estimate the incidence of adverse events for each tuberculosis drug.

FINDINGS

58 studies were identified, including 50 studies from the updated individual patient data meta-analysis for multidrug-resistant tuberculosis treatment. 35 of these studies, with 9178 patients, were included in our analysis. Using meta-analysis of proportions, drugs with low risks of adverse event occurrence leading to permanent discontinuation included levofloxacin (1·3% [95% CI 0·3-5·0]), moxifloxacin (2·9% [1·6-5·0]), bedaquiline (1·7% [0·7-4·2]), and clofazimine (1·6% [0·5-5·3]). Relatively high incidence of adverse events leading to permanent discontinuation was seen with three second-line injectable drugs (amikacin: 10·2% [6·3-16·0]; kanamycin: 7·5% [4·6-11·9]; capreomycin: 8·2% [6·3-10·7]), aminosalicylic acid (11·6% [7·1-18·3]), and linezolid (14·1% [9·9-19·6]). Risk of bias in selection of studies was judged to be low because there were no important differences between included and excluded studies. Variability between studies was significant for most outcomes analysed.

INTERPRETATION

Fluoroquinolones, clofazimine, and bedaquiline had the lowest incidence of adverse events leading to permanent drug discontinuation, whereas second-line injectable drugs, aminosalicylic acid, and linezolid had the highest incidence. These results suggest that close monitoring of adverse events is important for patients being treated for multidrug-resistant tuberculosis. Our results also underscore the urgent need for safer and better-tolerated drugs to reduce morbidity from treatment itself for patients with multidrug-resistant tuberculosis.

FUNDING

Canadian Institutes of Health Research, Centers for Disease Control and Prevention (USA), American Thoracic Society, European Respiratory Society, and Infectious Diseases Society of America.

Treatment of Drug-Resistant Tuberculosis. An Official ATS/CDC/ERS/IDSA Clinical Practice Guideline

Background: The American Thoracic Society, U.S. Centers for Disease Control and Prevention, European Respiratory Society, and Infectious Diseases Society of America jointly sponsored this new practice guideline on the treatment of drug-resistant tuberculosis (DR-TB). The document includes recommendations on the treatment of multidrug-resistant TB (MDR-TB) as well as isoniazid-resistant but rifampin-susceptible TB.Methods: Published systematic reviews, meta-analyses, and a new individual patient data meta-analysis from 12,030 patients, in 50 studies, across 25 countries with confirmed pulmonary rifampin-resistant TB were used for this guideline. Meta-analytic approaches included propensity score matching to reduce confounding. Each recommendation was discussed by an expert committee, screened for conflicts of interest, according to the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology.Results: Twenty-one Population, Intervention, Comparator, and Outcomes questions were addressed, generating 25 GRADE-based recommendations. Certainty in the evidence was judged to be very low, because the data came from observational studies with significant loss to follow-up and imbalance in background regimens between comparator groups. Good practices in the management of MDR-TB are described. On the basis of the evidence review, a clinical strategy tool for building a treatment regimen for MDR-TB is also provided.Conclusions: New recommendations are made for the choice and number of drugs in a regimen, the duration of intensive and continuation phases, and the role of injectable drugs for MDR-TB. On the basis of these recommendations, an effective all-oral regimen for MDR-TB can be assembled. Recommendations are also provided on the role of surgery in treatment of MDR-TB and for treatment of contacts exposed to MDR-TB and treatment of isoniazid-resistant TB.

Identification and Repurposing of Trisubstituted Harmine Derivatives as Novel Inhibitors of Mycobacterium tuberculosis Phosphoserine Phosphatase

Mycobacterium tuberculosis is still the deadliest bacterial pathogen worldwide and the increasing number of multidrug-resistant tuberculosis cases further complicates this global health issue. M. tuberculosis phosphoserine phosphatase SerB2 is a promising target for drug design. Besides being a key essential metabolic enzyme of the pathogen's serine pathway, it appears to be involved in immune evasion mechanisms. In this work, a malachite green-based phosphatase assay has been used to screen 122 compounds from an internal chemolibrary. Trisubstituted harmine derivatives were found among the best hits that inhibited SerB2 activity. Synthesis of an original compound helped to discuss a brief structure activity relationship evaluation. Kinetics experiments showed that the most potent derivatives inhibit the phosphatase in a parabolic competitive fashion with apparent inhibition constants ( K i ) values in the micromolar range. Their interaction modes with the enzyme were investigated through induced fit docking experiments, leading to results consistent with the experimental data. Cellular assays showed that the selected compounds also inhibited M. tuberculosis growth in vitro. Those promising results may provide a basis for the development of new antimycobacterial agents targeting SerB2.

Leprosy drug clofazimine activates peroxisome proliferator-activated receptor-γ and synergizes with imatinib to inhibit chronic myeloid leukemia cells

Leukemia stem cells contribute to drug-resistance and relapse in chronic myeloid leukemia (CML) and BCR-ABL1 inhibitor monotherapy fails to eliminate these cells, thereby necessitating alternate therapeutic strategies for patients CML. The peroxisome proliferator-activated receptor-γ (PPARγ) agonist pioglitazone downregulates signal transducer and activator of transcription 5 (STAT5) and in combination with imatinib induces complete molecular response in imatinib-refractory patients by eroding leukemia stem cells. Thiazolidinediones such as pioglitazone are, however, associated with severe side effects. To identify alternate therapeutic strategies for CML we screened Food and Drug Administration-approved drugs in K562 cells and identified the leprosy drug clofazimine as an inhibitor of viability of these cells. Here we show that clofazimine induced apoptosis of blood mononuclear cells derived from patients with CML, with a particularly robust effect in imatinib-resistant cells. Clofazimine also induced apoptosis of CD34⁺38^- progenitors and quiescent CD34⁺ cells from CML patients but not of hematopoietic progenitor cells from healthy donors. Mechanistic evaluation revealed that clofazimine, via physical interaction with PPARγ, induced nuclear factor kB-p65 proteasomal degradation, which led to sequential myeloblastoma oncoprotein and peroxiredoxin 1 downregulation and concomitant induction of reactive oxygen species-mediated apoptosis. Clofazimine also suppressed STAT5 expression and consequently downregulated stem cell maintenance factors hypoxia-inducible factor-1α and -2α and Cbp/P300 interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 (CITED2). Combining imatinib with clofazimine caused a far superior synergy than that with pioglitazone, with clofazimine reducing the half maximal inhibitory concentration (IC₅₀) of imatinib by >4 logs and remarkably eroding quiescent CD34⁺ cells. In a K562 xenograft study clofazimine and imatinib co-treatment showed more robust efficacy than the individual treatments. We propose clinical evaluation of clofazimine in imatinib-refractory CML.

Inhaled Antibiotics for Mycobacterial Lung Disease

Mycobacterial lung diseases are an increasing global health concern. Tuberculosis and nontuberculous mycobacteria differ in disease severity, epidemiology, and treatment strategies, but there are also a number of similarities. Pathophysiology and disease progression appear to be relatively similar between these two clinical diagnoses, and as a result these difficult to treat pulmonary infections often require similarly extensive treatment durations of multiple systemic drugs. In an effort to improve treatment outcomes for all mycobacterial lung diseases, a significant body of research has investigated the use of inhaled antibiotics. This review discusses previous research into inhaled development programs, as well as ongoing research of inhaled therapies for both nontuberculous mycobacterial lung disease, and tuberculosis. Due to the similarities between the causative agents, this review will also discuss the potential cross-fertilization of development programs between these similar-yet-different diseases. Finally, we will discuss some of the perceived difficulties in developing a clinically utilized inhaled antibiotic for mycobacterial diseases, and potential arguments in favor of the approach.

Multidrug-resistant tuberculosis infection and disease in children: a review of new and repurposed drugs

The World Health Organization estimates that 10 million new cases of tuberculosis (TB) occurred worldwide in 2017, of which 600,000 were rifampicin or multidrug-resistant (RR/MDR) TB. Modelling estimates suggest that 32,000 new cases of MDR-TB occur in children annually, but only a fraction of these are correctly diagnosed and treated. Accurately diagnosing TB in children, who usually have paucibacillary disease, and implementing effective TB prevention and treatment programmes in resource-limited settings remain major challenges. In light of the underappreciated RR/MDR-TB burden in children, and the lack of paediatric data on newer drugs for TB prevention and treatment, we present an overview of new and repurposed TB drugs, describing the available evidence for safety and efficacy in children to assist clinical care and decision-making.

Photoacoustic imaging of clofazimine hydrochloride nanoparticle accumulation in cancerous vs normal prostates

Prostate cancer was the most common form and had the second highest death rate of male cancer in the United States in 2015. Current diagnosis techniques, such as prostate-specific antigen tests, transrectal ultrasound scans, and biopsies, are often inconclusive, and in the latter case, invasive. Here, we explore the use of clofazimine hydrochloride nanoparticles (CFZ-HCl NPs), a repurposed formulation from an FDA-approved antimycobacterial agent, as a photoacoustic contrast agent for the evaluation of prostate cancer due to its macrophage-targeting capabilities and high optical absorbance at 495 nm. Using a transgenic adenocarcinoma of the mouse prostate (TRAMP) mouse model, our results indicate a preferential accumulation of intravenously injected CFZ-HCl NPs in cancerous prostates over normal prostates. Differences in accumulation of CFZ-HCl NPs between cancerous and normal prostates were determined using a two-wavelength unmixing technique via ex vivo photoacoustic imaging. Thus, intravenous injection of CFZ-HCl NPs leads to differences in the interactions of the particles with cancerous vs normal prostates, while allowing for photoacoustic detection and analysis of prostate cancer. These findings could lead to the development of a new noninvasive technique for the detection and monitoring of prostate cancer progression in an animal model that can potentially be translated to human patients.

Identifying Regimens Containing TBI-166, a New Drug Candidate against Mycobacterium tuberculosis In Vitro and In Vivo

TBI-166, derived from riminophenazine analogues, is under development in a phase I clinical trial in China. TBI-166 showed more potent anti-tuberculosis (anti-TB) activity than did clofazimine in in vitro and animal experiments. To identify potent regimens containing TBI-166 in TB chemotherapy, TBI-166 was assessed for pharmacological interactions in vitro and in vivo with several anti-TB drugs, including isoniazid (INH), rifampin (RFP), bedaquiline (BDQ), pretomanid (PMD), linezolid (LZD), and pyrazinamide (PZA). Using an in vitro checkerboard method, we found that TBI-166 did not show antagonism or synergy with the tested drugs. The interaction relationship between TBI-166 and each drug was indifferent. In in vivo experiments, aerosol infection models with BALB/c and C3HeB/FeJNju mice were established, testing drugs were administered either individually or combined in treatments containing TBI-166 and one, two, or three other drugs, and the bactericidal activities were determined after 4- and 8-week therapeutic treatments. In BALB/c mice, five TBI-166-containing regimens-TBI-166+BDQ, TBI-166+PZA, TBI-166+BDQ+LZD, TBI-166+BDQ+PMD, and TBI-166+BDQ+PMD+LZD-showed significantly more potent efficacy after 4 weeks of treatment compared to the control regimen, INH+RFP+PZA. At the end of an 8-week treatment, lung log CFU counts decreased to undetectable levels in mice treated with each of the five regimens. The rank order of the potency of the five regimens was as follows: TBI-166+BDQ+LZD > TBI-166+BDQ > TBI-166+PZA > TBI-166+BDQ+PMD+LZD > TBI-166+BDQ+PMD. In C3HeB/FeJNju mice, TBI-166+BDQ+LZD was also the most effective of the TBI-166-containing regimens. In conclusion, five potent chemotherapy regimens that included TBI-166 were identified. The TBI-166+BDQ+LZD regimen is recommended for further testing in a TBI-166 phase IIb clinical trial.

Synthesis and Characterization of a Biomimetic Formulation of Clofazimine Hydrochloride Microcrystals for Parenteral Administration

Clofazimine (CFZ) is a broad spectrum antimycobacterial agent recommended by the World Health Organization as a first line treatment for leprosy and second line treatment for multidrug resistant tuberculosis. Oral administration of CFZ leads to a red skin pigmentation side effect. Since CFZ is a weakly basic, red phenazine dye, the skin pigmentation side effect results from lipophilic partitioning of the circulating, free base (neutral) form of CFZ into the skin. Here, we developed a stable and biocompatible formulation of CFZ-HCl microcrystals that mimics the predominant form of the drug that bioaccumulates in macrophages, following long term oral CFZ administration. In mice, intravenous injection of these biomimetic CFZ-HCl microcrystals led to visible drug accumulation in macrophages of the reticuloendothelial system with minimal skin accumulation or pigmentation. In fact, no skin pigmentation was observed when the total amount of CFZ-HCl administered was equivalent to the total oral dose leading to maximal skin pigmentation. Thus, parenteral (injected or inhaled) biomimetic formulations of CFZ-HCl could be instrumental to avoid the pigmentation side effect of oral CFZ therapy.

Optimized Background Regimen for Treatment of Active Tuberculosis with the Next-Generation Benzothiazinone Macozinone (PBTZ169)

The efficacy of the standardized four-drug regimen (comprising isoniazid, rifampin, pyrazinamide, and ethambutol) for the treatment of tuberculosis (TB) is menaced by the emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis Intensive efforts have been made to develop new antibiotics or to repurpose old drugs, and several of these are currently being evaluated in clinical trials for their antitubercular activity. Among the new candidate drugs is macozinone (MCZ), the piperazine-containing benzothiazinone PBTZ169, which is currently being evaluated in phase I/II clinical trials. Here, we determined the in vitro and in vivo activity of MCZ in combination with a range of anti-TB drugs in order to design a new regimen against active TB. Two-drug combinations with MCZ were tested against M. tuberculosis using checkerboard and CFU enumeration after drug exposure assays. MCZ was observed to have no interactions with all first- and second-line anti-TB drugs. At the MIC of each drug, MCZ with either bedaquiline (BDQ), clofazimine (CLO), delamanid (DMD), or sutezolid (STZ) reduced the bacterial burden by 2 logs compared to that achieved with the drugs alone, indicating synergism. MCZ also displayed synergism with clomiphene (CLM), a potential inhibitor of the undecaprenyl pyrophosphate synthase (UppS) in mycobacteria. For all the other drugs tested in combination with MCZ, no synergistic activity was observed. Neither antagonism nor increased cytotoxicity was found for most combinations, suggesting that MCZ could be added to different TB treatment regimens without any significant adverse effects.

Inhibition of the aryl hydrocarbon receptor/polyamine biosynthesis axis suppresses multiple myeloma

Polyamine inhibition for cancer therapy is, conceptually, an attractive approach but has yet to meet success in the clinical setting. The aryl hydrocarbon receptor (AHR) is the central transcriptional regulator of the xenobiotic response. Our study revealed that AHR also positively regulates intracellular polyamine production via direct transcriptional activation of 2 genes, ODC1 and AZIN1, which are involved in polyamine biosynthesis and control, respectively. In patients with multiple myeloma (MM), AHR levels were inversely correlated with survival, suggesting that AHR inhibition may be beneficial for the treatment of this disease. We identified clofazimine (CLF), an FDA-approved anti-leprosy drug, as a potent AHR antagonist and a suppressor of polyamine biosynthesis. Experiments in a transgenic model of MM (Vk*Myc mice) and in immunocompromised mice bearing MM cell xenografts revealed high efficacy of CLF comparable to that of bortezomib, a first-in-class proteasome inhibitor used for the treatment of MM. This study identifies a previously unrecognized regulatory axis between AHR and polyamine metabolism and reveals CLF as an inhibitor of AHR and a potentially clinically relevant anti-MM agent.

Challenging the Drug-Likeness Dogma for New Drug Discovery in Tuberculosis

The emergence of multi- and extensively drug resistant tuberculosis worldwide poses a great threat to human health and highlight the need to discover and develop new, effective and inexpensive antituberculosis agents. High-throughput screening assays against well-validated drug targets and structure based drug design have been employed to discover new lead compounds. However, the great majority fail to demonstrate any antimycobacterial activity when tested against Mycobacterium tuberculosis in whole-cell screening assays. This is mainly due to some of the intrinsic properties of the bacilli, such as the extremely low permeability of its cell wall, slow growth, drug resistance, drug tolerance, and persistence. In this sense, understanding the pathways involved in M. tuberculosis drug tolerance, persistence, and pathogenesis, may reveal new approaches for drug development. Moreover, the need for compounds presenting a novel mode of action is of utmost importance due to the emergence of resistance not only to the currently used antituberculosis agents, but also to those in the pipeline. Cheminformatics studies have shown that drugs endowed with antituberculosis activity have the peculiarity of being more lipophilic than many other antibacterials, likely because this leads to improved cell penetration through the extremely waxy mycobacterial cell wall. Moreover, the interaction of the lipophilic moiety with the membrane alters its stability and functional integrity due to the disruption of the proton motive force, resulting in cell death. When a ligand-based medicinal chemistry campaign is ongoing, it is always difficult to predict whether a chemical modification or a functional group would be suitable for improving the activity. Nevertheless, in the “instruction manual” of medicinal chemists, certain functional groups or certain physicochemical characteristics (i.e., high lipophilicity) are considered red flags to look out for in order to safeguard drug-likeness and avoid attritions in the drug discovery process. In this review, we describe how antituberculosis compounds challenge established rules such as the Lipinski's “rule of five” and how medicinal chemistry for antituberculosis compounds must be thought beyond such dogmatic schemes.