Antibiotic Adjuvant 4-Hexylresorcinol Enhances the Efficiency of Antituberculosis Drugs.

We studied the possibility of using 4-hexylresorcinol to increase the efficiency of anti-mycobacterial chemotherapy. In an in vitro experiment, 4-hexylresorcinol increased the efficiency of rifampicin, kanamycin, and isoniazid against Mycobacterium smegmatis by 3-5 times. Experiments in sanitation of BALB/c mice infected with M. smegmatis showed the best efficacy of the isoniazid and 4-hexylresorcinol combination in comparison with isoniazid monotherapy. The growth-inhibiting activity of the combination of antibiotic rifabutin with 4-hexylresorcinol was shown on 6 strains of M. tuberculosis. A 2-fold decrease in the minimum inhibitory concentration of this antibiotic in the presence of half-minimum inhibitory concentration of 4-hexylresorcinol was demonstrated for monoresistant strain M. tuberculosis 5360/42Hr. On the mouse model of experimental tuberculosis caused by M. tuberculosis H37Rv, a 5-fold decrease in lung contamination and more rapid complete cure were achieved in animals treated with the combination of rifabutin and 4-hexylresorcinol in comparison with rifabutin monotherapy.

Molecular characterization of rifabutin-resistance in refractory Helicobacter pylori infection in Taiwan.

OBJECTIVES: To explore the molecular characteristics of rpoB, encoding ß-subunit of DNA-directed RNA polymerase, and unravel the link to rifabutin-resistance in patients with refractory Helicobacter pylori infection. METHODS: From January 2018-March 2021, a total of 1590 patients were screened for eligibility to participate in the study. Patients with refractory H. pylori infection were confirmed by using the (13C)-urea breath assay. All enrolled patients underwent esophagogastroduodenoscopy, and biopsies were taken for H. pylori culture and antibacterial susceptibility testing. Sequence analysis of rpoB was conducted for all rifabutin-resistant isolates. RESULTS: In total, 70 patients were diagnosed with refractory H. pylori infection, and 39 isolates were successfully cultured. Amongst, 10 isolates were identified as rifabutin-resistance and nine isolates exhibited at least one amino acid substitution in RpoB. Isolates with a minimal inhibitory concentration >32 mg/l displayed a higher number of mutational changes in RpoB than the others. Additionally, more amino acid substitutions in RpoB correlated with developing a higher minimal inhibitory concentration for H. pylori rifabutin-resistance. CONCLUSION: Our findings highlight the relationship between rifabutin-resistance in refractory H. pylori infection and specific mutations in RpoB, which will aid the clinical selection of appropriate antibacterial agents with better therapeutic effects.

The differences in drug disposition gene induction by rifampicin and rifabutin are unlikely due to different effects on important pregnane X receptor (NR1I2) splice variants.

Rifampicin and rifabutin can activate the pregnane X receptor (PXR, NR1I2), thereby inducing pharmacokinetically important genes/proteins and reducing exposure to co-administered drugs. Because induction effects vary considerably between these antibiotics, differences could be due to unequal rifamycin-induced activation or tissue expression of the three major NR1I2 splice variants, PXR.1 (NM_003889), PXR.2 (NM_022002), and PXR.3 (NM_033013). Consequently, PXR activation (PXR reporter gene assays) and mRNA expression levels of total NR1I2, PXR.1, PXR.2, and PXR.3 were investigated by polymerase chain reaction in colon and liver samples from eleven surgical patients, in LS180 cells, and primary human hepatocytes. Compared to the colon, total NR1I2 mRNA expression was higher in the liver. Both tissues showed similar expression levels of PXR.1 and PXR.3, respectively. PXR.2 was not quantifiable in the colon samples. Rifampicin and rifabutin similarly enhanced PXR.1 and PXR.2 activity when transfected into LS180 cells, while PXR.3 could not be activated. In LS180 cells, rifampicin (10 µM) reduced total NR1I2 and PXR.3 expression 2-fold after 24 h, while rifabutin (10 µM) increased total NR1I2, PXR.1, PXR.2, and PXR.3 mRNA by approx. 50% after 96-h exposure. In primary human hepatocytes, rifampicin (10 µM) suppressed total NR1I2, PXR.1, and PXR.3 after 48-h exposure, and rifabutin (10 µM) had no significant impact on total NR1I2 or any of the splice variants studied. In conclusion, both antibiotics activated the studied PXR splice variants similarly but modified their expression differently. While rifampicin can suppress mRNA of PXR forms, rifabutin rather increases their expression levels.

Rifabutin but not rifampicin can partly out-balance P-glycoprotein induction by concurrent P-glycoprotein inhibition through high affinity binding to the inhibitory site.

Physiology-based pharmacokinetic modeling suggests that rifabutin can out-balance P-glycoprotein (P-gp) induction by concurrent P-gp inhibition. However, clinical or experimental evidence for this Janus-faced rifabutin effect is missing. Consequently, LS180 cells were exposed to a moderately (2 µM) and strongly (10 µM) P-gp-inducing concentration of rifampicin or rifabutin for 6 days. Cellular accumulation of the fluorescent P-gp substrate rhodamine 123 was evaluated using flow cytometry, either without (induction only) or with adding rifamycin drug to the cells during the rhodamine 123 efflux phase (induction + potential inhibition). Rhodamine 123 accumulation was decreased similarly by both drugs after 6-day exposure (2 µM: 55% residual fluorescence compared to non-induced cells, P < 0.01; 10 µM: 30% residual fluorescence compared to non-induced cells, P < 0.001), indicating P-gp induction. Rhodamine 123 influx transporters mRNA expressions were not affected, excluding off-target effects. Acute re-exposure to rifabutin, however, considerably re-increased rhodamine 123 accumulation (2 µM induction: re-increase by 55%, P < 0.01; 10 µM induction: 49% re-increase, P < 0.001), suggesting P-gp inhibition. In contrast, rifampicin only had weak effects (2 µM induction: no re-increase; 10 µM induction: 16% re-increase; P < 0.05). Molecular docking analysis eventually revealed that rifabutin has a higher binding affinity to the inhibitor binding site of P-gp than rifampicin (ΔG (kcal/mol) = -11.5 vs -5.3). Together, this study demonstrates that rifabutin can at least partly mask P-gp induction by P-gp inhibition, mediated by high affinity binding to the inhibitory site of P-gp.

[In vitro Activity of Rifabutin and Clofazimine to Macrolide-Resistant Mycobacterium abscessus Complex Clinical Isolates]. / Rifabutin ve Klofaziminin Makrolidlere Dirençli Mycobacterium abscessus Kompleks Klinik Izolatlarina In vitro Etkinligi.

Mycobacterium abscessus complex (MABSC) is one of the most resistant bacteria against antimicrobial agents. The number of agents that can be used by oral route, such as macrolides, is limited in antimicrobial therapy. In recent years, rifabutin and clofazimine have gained importance as they can be administered by oral route and have shown synergistic effects with macrolides and aminoglycosides. The aim of this study was to determine the in vitro activity of rifabutin and clofazimine against clinical isolates of MABSC resistant to macrolides. A total of 48 MABSC isolates obtained from respiratory tract and other clinical samples in the Tuberculosis Laboratories of the Faculty of Medicine of Manisa Celal Bayar and Ege Universities were included in the study. Subspecies differentiation and aminoglycoside and macrolide resistance of the isolates were determined by GenoType NTM-DR test. Rifabutin and clofazimine susceptibilities were determined by standard broth microdilution method. Of the MABSC isolates 42 were identified as M.abscessus subsp. abscessus, three as M.abscessus subsp. bolletii and three as M.abscessus subsp. massiliense. None of the isolates exhibited rrs and rrl mutations indicating acquired macrolide resistance and aminoglycoside resistance. However, the erm(41) T28 genotype which is associated with inducible macrolide resistance was detected in 41 (85%) of the strains. All M.abscessus subsp. massiliense isolates were found to be genotypically susceptible to macrolides. The minimum inhibitory concentration (MIC) range values for rifabutin were 0.0625 to 32 µg/mL, while for clofazimine, the range was 0.0625 to 1 µg/mL. Rifabutin MIC values were significantly higher (mean 5.98 µg/mL vs 0.5 µg/mL, p= 0.026) in the isolates with macrolide resistance. There was no correlation between macrolide resistance and clofazimine MIC values (mean 0.25 µg/mL vs. 0.214 µg/mL, p= 0.758). The MIC50 and MIC90 values for rifabutin were 1 and 8 µg/mL, respectively, while for clofazimine they were 0.25 and 0.5 µg/mL. Macrolide resistance was found to be higher in isolates with rifabutin MIC values above the MIC50 value (p= 0.045). In conclusion, the determination of higher rifabutin MIC values in isolates resistant to macrolides suggested that susceptibility testing should be performed before adding rifabutin to the treatment regimen. The low MIC values of clofazimine in all strains indicated that it may be used as a first choice in the combination therapy. However, further studies using a larger number of clinical isolates and applying genotypic and phenotypic susceptibility tests are needed to determine threshold MIC values to assist clinicians in making treatment decisions.

Successful Anticoagulation With Warfarin After Switching From Rifampin to Rifabutin.

PURPOSE: A case of a patient receiving warfarin for pulmonary embolism (PE) concomitantly with rifampin for treatment of active pulmonary tuberculosis (PTB) is presented. A successful clinical intervention whereby the patient achieved therapeutic anticoagulation after switching to an alternative rifamycin antibacterial, rifabutin, is described. SUMMARY: The drug-drug interaction between warfarin and rifampin is well known and documented. However, to our knowledge, no case reports of the interaction between warfarin and rifabutin have been published, and literature describing this interaction is lacking. We describe the case of a 27-year-old African American female referred to a pharmacist-managed anticoagulation clinic for treatment of PE with warfarin. The patient was also being treated for active tuberculosis with rifampin, isoniazid, pyrazinamide, and ethambutol. Warfarin was initiated and over the course of 1 month was continuously increased to a total weekly dose (TWD) of 140 mg without ever achieving the target international normalized ratio (INR) of 2 to 3. In an attempt to reach the target INR, rifampin was switched to rifabutin to minimize the drug-drug interaction with warfarin. Six days after this switch, the target INR was achieved with a lower warfarin TWD of 115 mg. Rifabutin interacts with warfarin to a lesser degree than rifampin and may be considered as an alternative in patients taking warfarin who require treatment with a rifamycin. CONCLUSION: For patients in whom therapeutic anticoagulation with warfarin has been difficult, the use of rifabutin may be considered in place of rifampin when the concomitant use of a rifamycin is required.

ADP-ribosylation-resistant rifabutin analogs show improved bactericidal activity against drug-tolerant M. abscessus in caseum surrogate.

Necrotic lesions and cavities filled with caseum are a hallmark of mycobacterial pulmonary disease. Bronchocavitary Mycobacterium abscessus disease is associated with poor treatment outcomes. In caseum surrogate, M. abscessus entered an extended stationary phase showing tolerance to killing by most current antibiotics, suggesting that caseum persisters contribute to the poor performance of available treatments. Novel ADP-ribosylation-resistant rifabutin analogs exhibited bactericidal activity against these M. abscessus persisters at concentrations achievable by rifamycins in caseum.

Respirable konjac glucomannan microparticles as antitubercular drug carriers: Effects of in vitro and in vivo interactions.

Pulmonary delivery of drugs is potentially beneficial in the context of lung disease, maximising drug concentrations in the site of action. A recent work proposed spray-dried konjac glucomannan (KGM) microparticles as antitubercular drug (isoniazid and rifabutin) carriers to treat pulmonary tuberculosis. The present work explores in vitro and in vivo effects of these microparticles, focusing on the ability for macrophage uptake, the exhibited antibacterial activity and safety issues. Efficient uptake of KGM microparticles by macrophages was demonstrated in vitro, while the antitubercular activity of the model drugs against Mycobacterium bovis was not affected by microencapsulation in KGM microparticles. Despite the good indications provided by the developed system, KGM is not yet approved for pulmonary applications, which is a limiting characteristic. To reinforce the available data on the performance of the material, safety parameters were evaluated both in vitro and in vivo, showing promising results. No significant cell toxicity was observed at concentrations considered realistic for lung delivery approaches (up to 125 µg/mL) when lung epithelial cells and macrophages were exposed to KGM microparticles (both drug-loaded and unloaded). Finally, no signs of systemic or lung inflammatory response were detected in mice after receiving 10 administrations of unloaded KGM microparticles.

Comprehensive in vitro analysis evaluating the variable drug-drug interaction risk of rifampicin compared to rifabutin.

Compared to rifampicin (600 mg/day), standard doses of rifabutin (300 mg/day) have a lower risk of drug-drug interactions due to induction of cytochrome P450 3A4 (CYP3A4) or P-glycoprotein (Pgp/ABCB1) mediated by the pregnane X receptor (PXR). However, clinical comparisons with equal rifamycin doses or in vitro experiments respecting actual intracellular concentrations are lacking. Thus, the genuine pharmacological differences and the potential molecular mechanisms of the discordant perpetrator effects are unknown. Consequently, the cellular uptake kinetics (mass spectrometry), PXR activation (luciferase reporter gene assays), and impact on CYP3A4 and Pgp/ABCB1 expression and activity (polymerase chain reaction, enzymatic assays, flow cytometry) were evaluated in LS180 cells after treatment with different rifampicin or rifabutin concentrations for variable exposure times and eventually normalized to actual intracellular concentrations. In addition, inhibitory effects on CYP3A4 and Pgp activities were investigated. While rifampicin is poorly taken up by LS180 cells, it strongly activates PXR and leads to enhanced expression and activity of CYP3A4 and Pgp. In contrast, rifabutin is a significantly less potent and less efficient PXR activator and gene inducer, despite sixfold to eightfold higher intracellular accumulation. Finally, rifabutin is a potent inhibitor of Pgp (IC50 = 0.3 µM) compared to rifampicin (IC50 = 12.9 µM). Together, rifampicin and rifabutin significantly differ by their effects on the regulation and function of CYP3A4 and Pgp, even when controlled for intracellular concentrations. Rifabutin's concurrent Pgp inhibitory action might partly compensate the inducing effects, explaining its weaker clinical perpetrator characteristics.

Management of Drug Interactions with Inducers: Onset and Disappearance of Induction on Cytochrome P450 3A4 and Uridine Diphosphate Glucuronosyltransferase 1A1 Substrates.

BACKGROUND: People living with HIV may present co-morbidities requiring the initiation and subsequently the discontinuation of medications with inducing properties. The time to reach maximal enzyme induction and to return to baseline enzyme levels has not been thoroughly characterized. OBJECTIVE: The aim of this study was to evaluate the onset and disappearance of dolutegravir [uridine diphosphate glucuronosyltransferase (UGT) 1A1 and cytochrome P450 (CYP) 3A4 substrate] and raltegravir (UGT1A1 substrate) induction with strong and moderate inducers using physiologically based pharmacokinetic (PBPK) modeling. METHODS: The predictive performance of the PBPK model to simulate dolutegravir and raltegravir pharmacokinetics and to reproduce the strength of induction was verified using clinical drug-drug interaction studies (steady-state induction) and switch studies (residual induction). The model was considered verified when the predictions were within 2-fold of the observed data. One hundred virtual individuals (50% female) were generated to simulate the unstudied scenarios. The results were used to calculate the fold-change in CYP3A4 and UGT1A1 enzyme levels upon initiation and discontinuation of strong (rifampicin) or moderate (efavirenz or rifabutin) inducers. RESULTS: The time for reaching maximal induction and subsequent disappearance of CYP3A4 induction was 14 days for rifampicin and efavirenz but 7 days for rifabutin. The distinct timelines for the moderate inducers relate to their different half-lives and plasma concentrations. The induction and de-induction processes were more rapid for UGT1A1. CONCLUSIONS: Our simulations support the common practice of maintaining the adjusted dosage of a drug for another 2 weeks after stopping an inducer. Furthermore, our simulations suggest that an inducer should be administered for at least 14 days before conducting interaction studies to reach maximal induction.

Cascade Transformation of the Ansamycin Benzoquinone Core into Benzoxazole Influencing Anticancer Activity and Selectivity.

The metal-free cascade transformation of geldanamycin benzoquinone core is proposed at relatively mild conditions. This approach yields new benzoxazole ansamycin antibiotics and enables their functionalization in an atom-economic manner, irrespective of the type of amine used. The analysis of the heterocyclization course reveals the dependence of its rate on the nature of the para-substituent within the benzylamine moiety (EDG/EWG) and the strength of the base. The reduction of the ansamycin core enables an increase in anticancer potency and selectivity.

Design and in vitro assessment of chitosan nanocapsules for the pulmonary delivery of rifabutin.

Tuberculosis (TB) is a life-threatening disease and a main cause of death worldwide. It mainly affects the lungs, and it is attributed to the infection with Mycobacterium tuberculosis (MTB). Current treatments consist of the oral administration of combinations of antibiotics including rifabutin, in high doses and for long periods of time. These therapeutic regimens are associated with many side effects and high rates of drug resistance. To overcome these problems, this study aims at developing a nanosystem for the improved delivery of antibiotics, with potential application in pulmonary delivery. Chitosan-based nanomaterials are widely used in biomedical applications, due to their biodegradability and biocompatibility, as well as their potential antimicrobial effects and lack of toxicity. In addition, this polymer is particularly attractive for mucosal delivery due to its bioadhesive properties. Therefore, the structure of the proposed nanocarrier consists of a chitosan shell and a lipid core with a combination of different oils and surfactants to allow optimal association of the hydrophobic drug rifabutin. These nanocapsules were characterized in terms of size, polydispersity index, surface charge, morphology, encapsulation efficiency and biological stability. The release kinetics of the drug-loaded nanostructures was evaluated in simulated lung media. Moreover, in vitro studies in different cell models (A549 and Raw 264.7 cells) demonstrated the safety of the nanocapsules as well as their efficient internalization. An antimicrobial susceptibility test was performed to evaluate the efficacy of the rifabutin-loaded nanocapsules against Mycobacterium phlei. This study indicated complete inhibition for antibiotic concentrations within the expected susceptibility range of Mycobacterium (≤ 0.25-16 mg/L).

Defining the minimum inhibitory concentration of 22 rifamycins in iron limited, physiologic medium against Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae clinical isolates.

Recently, we reported rifabutin hyper-activity against Acinetobacter baumannii. We sought to characterize if any additional rifamycins (n = 22) would also display hyper-activity when tested in iron-limited media against A. baumannii, K. pneumoniae, and E. coli. MICs were determined against representative clinical isolates using the iron-limited media RPMI-1640. Only rifabutin was hyperactive against A. baumannii.

Using Dynamic Oral Dosing of Rifapentine and Rifabutin to Simulate Exposure Profiles of Long-Acting Formulations in a Mouse Model of Tuberculosis Preventive Therapy.

Administration of tuberculosis preventive therapy (TPT) to individuals with latent tuberculosis infection is an important facet of global tuberculosis control. The use of long-acting injectable (LAI) drug formulations may simplify and shorten regimens for this indication. Rifapentine and rifabutin have antituberculosis activity and physiochemical properties suitable for LAI formulation, but there are limited data available for determining the target exposure profiles required for efficacy in TPT regimens. The objective of this study was to determine exposure-activity profiles of rifapentine and rifabutin to inform development of LAI formulations for TPT. We used a validated paucibacillary mouse model of TPT in combination with dynamic oral dosing of both drugs to simulate and understand exposure-activity relationships to inform posology for future LAI formulations. This work identified several LAI-like exposure profiles of rifapentine and rifabutin that, if achieved by LAI formulations, could be efficacious as TPT regimens and thus can serve as experimentally determined targets for novel LAI formulations of these drugs. We present novel methodology to understand the exposure-response relationship and inform the value proposition for investment in development of LAI formulations that have utility beyond latent tuberculosis infection.

In Vitro Synergistic Effects of Omadacycline with Other Antimicrobial Agents against Mycobacterium abscessus.

The clinical importance of Mycobacterium abscessus species (MABS) infections has been increasing. However, the standard treatment regimens recommended in the current guidelines often result in unfavorable outcomes. Therefore, we investigated the in vitro activity of omadacycline (OMC), a novel tetracycline, against MABS to explore its potential as a novel therapeutic option. The drug susceptibilities of 40 Mycobacterium abscessus subsp. abscessus (Mab) clinical strains obtained from the sputum of 40 patients from January 2005 to May 2014 were investigated. The MIC results for OMC, amikacin (AMK), clarithromycin (CLR), clofazimine (CLO), imipenem (IPM), rifabutin (RFB), and tedizolid (TZD) alone and their combined effects (with OMC) were examined using the checkerboard method. Additionally, we studied the differences in the effectiveness of the antibiotic combinations based on the colony morphotype of Mab. The MIC50 and MIC90 of OMC alone were 2 and 4 µg/mL, respectively. The combinations of OMC with AMK, CLR, CLO, IPM, RFB, and TZD showed synergy against 17.5%, 75.8%, 25.0%, 21.1%, 76.9%, and 34.4% of the strains, respectively. Additionally, OMC combined with CLO (47.1% versus 9.5%, P = 0.023) or TZD (60.0% versus 12.5%, P = 0.009) showed significantly higher synergy against strains with rough morphotypes than those with smooth morphotypes. In conclusion, the checkerboard analyses revealed that the synergistic effects of OMC were observed most frequently with RFB, followed by CLR, TZD, CLO, IPM, and AMK. Furthermore, OMC tended to be more effective against rough-morphotype Mab strains.

CRISPR Interference-Based Inhibition of MAB_0055c Expression Alters Drug Sensitivity in Mycobacterium abscessus.

There is an unmet medical need for effective treatments against Mycobacterium abscessus infections. Although advanced molecular genetic tools to validate drug targets and resistance of M. abscessus exist, the practical design and construction of plasmids are relatively laborious and time-consuming. Thus, for this purpose, we used CRISPR interference (CRISPRi) combined with catalytically deactivated Cas9 to inhibit the gene expression of a predicted LysR-type transcriptional regulator gene, MAB_0055c, in M. abscessus and evaluated its contribution to the development of drug resistance. Our results showed that silencing the MAB_0055c gene lead to increased rifamycin susceptibility depending on the hydroquinone moiety. These results demonstrate that CRISPRi is an excellent approach for studying drug resistance in M. abscessus. IMPORTANCE In this study, we utilized CRISPR interference (CRISPRi) to specifically target the MAB_0055c gene in M. abscessus, a bacterium that causes difficult-to-treat infections. The study found that silencing the gene lead to increased rifabutin and rifalazil susceptibility. This study is the first to establish a link between the predicted LysR-type transcriptional regulator gene and antibiotic resistance in mycobacteria. These findings underscore the potential of using CRISPRi as a tool for elucidating resistance mechanisms, essential drug targets, and drug mechanisms of action, which could pave the way for more effective treatments for M. abscessus infections. The results of this study could have important implications for the development of new therapeutic options for this challenging-to-treat bacterial infection.

A Phase 1, Open-Label, Fixed-Sequence, Drug-Drug Interaction Study of Zanubrutinib with Rifabutin in Healthy Volunteers.

Zanubrutinib is a second-generation Bruton tyrosine kinase inhibitor that is primarily metabolized by CYP3A enzymes. Previous drug-drug interaction (DDI) studies have demonstrated that co-administration of zanubrutinib with rifampin, a strong CYP3A inducer, reduces zanubrutinib plasma concentrations, potentially impacting activity. The impact of the co-administration of zanubrutinib with less potent CYP3A inducers is unclear. This phase 1, open-label, fixed-sequence DDI study evaluated the pharmacokinetics, safety, and tolerability of zanubrutinib when co-administered with steady-state rifabutin, a known CYP3A inducer less potent than rifampin, in 13 healthy male volunteers (NCT04470908). Co-administration of zanubrutinib with rifabutin resulted in a less than 2-fold reduction of zanubrutinib exposures. Overall, zanubrutinib was well tolerated. The results of this study provide useful information for the evaluation of the DDI between rifabutin and zanubrutinib. In conjunction with safety and efficacy data from other clinical studies, these results will be taken into consideration to determine the appropriate dose recommendation of zanubrutinib when co-administered with CYP3A inducers.

Nagimycins A and B, Antibacterial Ansamycin-Related Macrolactams from Streptomyces sp. NA07423.

Chemical investigation of Streptomyces sp. NA07423 led to the discovery of two unreported macrolactams, nagimycins A (1) and B (2). Their structures were elucidated by NMR, HRESIMS, X-ray crystallography, and comparison of experimental and theoretical ECD spectra. The nagimycins have a unique butenolide moiety rarely found in ansamycin antibiotics. Genome analysis revealed the putative biosynthetic gene cluster for nagimycins, and a likely biosynthetic pathway was proposed. Notably, compounds 1 and 2 exhibited potent antibacterial activity against two pathogenic Xanthomonas bacteria.

A ready-to-use dry powder formulation based on protamine nanocarriers for pulmonary drug delivery.

The use of oral antibiotic therapy for the treatment of respiratory diseases as tuberculosis has promoted the appearance of side effects as well as resistance to these treatments. The low solubility, high metabolism, and degradation of drugs as rifabutin, have led to the use of combined and prolonged therapies, which difficult patient compliance. In this work, we develop inhalable formulations from biomaterials such as protamine to improve the therapeutic effect. Rifabutin-loaded protamine nanocapsules (NCs) were prepared by solvent displacement method and were physico-chemically characterized and evaluated for their dissolution, permeability, stability, cytotoxicity, hemocompatibility, internalization, and aerodynamic characteristics after a spray-drying procedure. Protamine NCs presented a size of around 200 nm, positive surface charge, and drug association up to 54%. They were stable as suspension under storage, as well as in biological media and as a dry powder after lyophilization in the presence of mannitol. Nanocapsules showed a good safety profile and cellular uptake with no tolerogenic effect on macrophages and showed good compatibility with red blood cells. Moreover, the aerodynamic evaluation showed a fine particle fraction deposition up to 30% and a mass median aerodynamic diameter of about 5 µm, suitable for the pulmonary delivery of therapeutics.