Impact of Drug-Polymer Miscibility on Enthalpy Relaxation of Irbesartan Amorphous Solid Dispersions

Purpose

Drug-polymer miscibility has been proposed to play a critical role in physical stability of amorphous solid dispersions (ASDs). The purpose of the current work was to investigate the role of drug-polymer miscibility on molecular mobility, measured as enthalpy relaxation (ER) of amorphous irbesartan (IBS) in ASDs.

Methods

Two polymers, i.e. polyvinylpyrrolidone K30 (PVP K30) and hydroxypropyl methylcellulose acetate succinate (HPMCAS), were used to generate ASDs with 10% w/w of the polymer. Drug-polymer miscibility was determined using melting point depression (MPD) method. Molecular mobility was assessed from ER studies at a common degree of undercooling (DOU) (T_g???13.0°C?±?0.5°C).

Results

IBS exhibited higher miscibility in PVP K30 as compared to HPMCAS at temperature?>?140°C. However, extrapolation of miscibility data to storage temperature (62°C) using Flory-Huggins (F-H) theory revealed a reversal of the trend. Miscibility of IBS was found to be higher in HPMCAS (2.6%) than PVP K30 (1.3%) at 62°C. Stretched relaxation time (τ^β) of 17.4365 h and 7.0886 h was obtained for IBS-HPMCAS and IBS-PVP K30 ASDs, respectively.

Conclusion

Miscibility of drug-polymer at storage temperature explained the behavior of the molecular mobility, while miscibility near the melting point provided a reverse trend. Results suggest that drug-polymer miscibility determined at temperatures higher than the storage temperature should be viewed cautiously.

     

Physical Stability of Amorphous Solid Dispersions: a Physicochemical Perspective with Thermodynamic,Kinetic and Environmental Aspects

Purpose

Amorphous solid dispersions (ASDs) have been widely used in the pharmaceutical industry for solubility enhancementof poorly water-soluble drugs. The physical stability, however, remainsone of the most challenging issues for the formulation development.Many factors can affect the physical stability via different mechanisms, and therefore an in-depth understanding on these factors isrequired.

Methods

In this review, we intend to summarize the physical stability of ASDsfrom a physicochemical perspective whereby factors that can influence the physical stability areclassified into thermodynamic, kinetic and environmental aspects.

Results

The drug-polymer miscibility and solubility are consideredas the main thermodynamicfactors which may determine the spontaneity of the occurrence of the physical instabilityof ASDs. Glass-transition temperature,molecular mobility, manufacturing process,physical stabilityof amorphous drugs, and drug-polymerinteractionsareconsideredas the kinetic factors which areassociated with the kinetic stability of ASDs on aging. Storage conditions including temperature and humidity could significantly affect the thermodynamicand kineticstabilityof ASDs.

Conclusion

When designing amorphous solid dispersions, it isrecommended that these thermodynamic, kinetic and environmental aspects should be completely investigatedand compared to establish rationale formulations for amorphous solid dispersions with high physical stability.

     

Influence of Low-Molecular-Weight Excipients on the Phase Behavior of PVPVA64 Amorphous Solid Dispersions

Purpose

The oral bioavailability of poorly water-soluble active pharmaceutical ingredients (APIs) can be improved by the preparation of amorphous solid dispersions (ASDs) where the API is dissolved in polymeric excipients. Desired properties of such ASDs like storage stability, dissolution behavior, and processability can be optimized by additional excipients. In this work, the influence of so-called low-molecular-weight excipients (LMWEs) on the phase behavior of ASDs was investigated.

Method

Binary ASDs of an amorphous API, naproxen (NAP) or acetaminophen (APAP), embedded in poly-(vinylpyrrolidone-co-vinyl acetate) (PVPVA64) were chosen as reference systems. Polyethylene glycol 1500 (PEG1500), D-α-tocopherol polyethylene glycol 1000 succinate (TPGS1000), propylene glycol monocaprylate type II (Capryol? 90), and propylene glycol monolaurate type I (Lauroglycol? FCC) were used as LMWEs. The API solubility in the excipients and the glass-transition temperature of the ASDs were modeled using the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) and the Kwei equation, respectively, and compared to corresponding experimental data.

Results

The API solubility curves in ternary systems with 90/10 wt%/wt% PVPVA64/LMWE ratios were very close to those in pure PVPVA64. However, the glass-transition temperatures of API/PVPVA64/LMWE ASDs were much lower than those of API/PVPVA64 ASDs. These effects were determined experimentally and agreed with the predictions using the PC-SAFT and Kwei models.

Conclusion

The impact of the LMWEs on the thermodynamic stability of the ASDs is quite small while the kinetic stability is significantly decreased even by small LMWE amounts. PC-SAFT and the Kwei equation are suitable tools for predicting the influence of LMWEs on the ASD phase behavior.

     

Leaching of Lopinavir Amorphous Solid Dispersions in Acidic Media

Purpose

Amorphous solid dispersions (ASDs) formulated with acid-insoluble (enteric) polymers form suspensions in acidic media where the polymer is largely insoluble. However, a small amount of drug can dissolve and a supersaturated solution may be generated. The goal of this study was to gain insight into the leaching mechanisms of both drug and polymer from the suspended particles, studying the impact of solution additives such as surfactants.

Methods

ASDs were prepared by spray drying lopinavir (LPV) with an enteric polymer, either hydroxypropylmethylcellulose acetate succinate (HPMCAS) or hydroxypropylmethylcellulose phthalate (HPMCP). Four surfactants and a suspending agent were added to the liquid media to evaluate the effect of these excipients on leaching. pH 3 and pH 5 buffers were used to investigate the effect of pH.

Results

The extent of drug leaching from the amorphous formulation was proportional to the crystalline solubility of the drug in the same medium. All surfactants promoted solubilization of LPV with the exception of poloxamer and sodium dodecyl sulfate-HPMCP combinations. A small amount of polymer ionization significantly enhanced LPV leaching in solutions containing an ionic surfactant.

Conclusions

The mechanism of enhanced leaching appeared to be solubilization, with the apparent supersaturation remaining the same for systems containing the same polymer.

     

Dissolution Performance of High Drug Loading Celecoxib Amorphous Solid Dispersions Formulated with Polymer Combinations

Purpose

The aims of this study were twofold. First, to evaluate the effectiveness of selected polymers in inhibiting solution crystallization of celecoxib. Second, to compare the release rate and crystallization tendency of celecoxib amorphous solid dispersions (ASDs) formulated with a single polymer, or binary polymer combinations.

Methods

The effectiveness of polymers, polyvinylpyrrolidone (PVP), hydroxypropylmethyl cellulose (HPMC) or HPMC acetate succinate (HPMCAS), in maintaining supersaturation of celecoxib solutions was evaluated by performing nucleation induction time measurements. Crystallization kinetics of ASD suspensions were monitored using Raman spectroscopy. Dissolution experiments were carried out under non-sink conditions.

Results

Pure amorphous celecoxib crystallized rapidly through both matrix and solution pathways. Matrix and solution crystallization was inhibited when celecoxib was molecularly mixed with a polymer, resulting in release of the drug to form supersaturated solutions. Cellulosic polymers were more effective than PVP in maintaining supersaturation. Combining a cellulosic polymer and PVP enabled improved drug release and stability to crystallization.

Conclusions

Inclusion of an effective solution crystallization inhibitor as a minor component in ternary dispersions resulted in prolonged supersaturation following dissolution. This study shows the feasibility of formulation strategies for ASDs where a major polymer component is used to achieve one key property e.g. release, while a minor polymer component is added to prevent crystallization.

     

Solid-State NMR Investigation of Drug-Excipient Interactions and Phase Behavior in Indomethacin-Eudragit E Amorphous Solid Dispersions

Purpose

To investigate the nature of drug-excipient interactions between indomethacin (IMC) and methacrylate copolymer Eudragit® E (EE) in the amorphous state, and evaluate the effects on formulation and stability of these amorphous systems.

Methods

Amorphous solid dispersions containing IMC and EE were spray dried with drug loadings from 20% to 90%. PXRD was used to confirm the amorphous nature of the dispersions, and DSC was used to measure glass transition temperatures (T_g). ¹³C and ¹⁵N solid-state NMR was utilized to investigate changes in local structure and protonation state, while ¹H T₁ and T_1ρ relaxation measurements were used to probe miscibility and phase behavior of the dispersions.

Results

T_g values for IMC-EE solid dispersions showed significant positive deviations from predicted values in the drug loading range of 40–90%, indicating a relatively strong drug-excipient interaction. ¹⁵N solid-state NMR exhibited a change in protonation state of the EE basic amine, with two distinct populations for the EE amine at ?360.7 ppm (unprotonated) and ?344.4 ppm (protonated). Additionally, ¹H relaxation measurements showed phase separation at high drug load, indicating an amorphous ionic complex and free IMC-rich phase. PXRD data showed all ASDs up to 90% drug load remained physically stable after 2 years.

Conclusions

¹⁵N solid-state NMR experiments show a change in protonation state of EE, indicating that an ionic complex indeed forms between IMC and EE in amorphous solid dispersions. Phase behavior was determined to exhibit nanoscale phase separation at high drug load between the amorphous ionic complex and excess free IMC.

     

Polymer/Amorphous Salt Solid Dispersions of Ciprofloxacin

Purpose

To improve the pharmaceutical properties of amorphous ciprofloxacin (CIP) succinate salts via formulation as polymer/amorphous salt solid dispersions (ASSDs).

Methods

ASSDs consisting of an amorphous CIP/succinic acid 1:1 or 2:1 salt dispersed in PVP or Soluplus were produced by spray drying and ball milling. The solid state characteristics, miscibility, stability, solubility and passive transmembrane permeability of the ASSDs were then examined.

Results

The ASSDs had higher glass transition and crystallization temperatures than the corresponding amorphous succinate salts, and were also more stable during long-term stability studies. The results of inverse gas chromatography and thermal analysis indicated that the salts and polymers form a miscible mixture. The solubility of the pure drug in water and biorelevant media was significantly increased by all of the formulations. The permeability of the ASSDs did not differ significantly from that of the amorphous CIP succinate salts, however all samples were less permeable than the pure crystalline drug.

Conclusions

The formulation of amorphous CIP succinate salts as ASSDs with polymer improved their long-term stability, but did not significantly affect their solubility or permeability.

     

Population Pharmacokinetic Modeling of Etoposide Free Concentrations in Solid Tumor

Purpose

This study aimed to determine free etoposide (ETO) concentrations in two regions of Walker-256 (W256) solid tumor using microdialysis and to establish a population pharmacokinetic (popPK) model to describe simultaneously free tumor and total plasma concentrations.

Methods

W256 tumor-bearing Wistar rats received ETO 10 or 20 mg/kg i.v. bolus. Free ETO concentrations were sampled from central and peripheral regions of the tumor via CMA/20 probes for up to 7 h, whereas blood samples were collected via carotid artery cannulation. Total plasma and free tumor concentration-time profiles were analyzed by non-compartmental approach using WinNonlin® v. 5.3. PopPK modeling was conducted using MONOLIX v.4.3.3.

Results

ETO penetration was higher in the periphery (61?±?15% and 61?±?29%) than in tumor center (34?±?6% and 28?±?11%) following 10 and 20 mg/kg doses, respectively (ANOVA, α?=?0.05). A 4-compartment model fitted ETO concentration-time profiles in all sampling compartments.

Conclusions

The popPK model allowed the simultaneous fitting of plasma and tumor concentrations and a better understanding of ETO distribution in solid tumors. ETO plasma concentrations are not a good surrogate for tumoral exposure, emphasizing the importance of knowing intratumoral concentrations to predict drug response.

     

Characterization of Heterogeneity and Spatial Distribution of Phases in Complex Solid Dispersions by Thermal Analysis by Structural Characterization and X-ray Micro Computed Tomography

Purpose

This study investigated the effect of drug-excipient miscibility on the heterogeneity and spatial distribution of phase separation in pharmaceutical solid dispersions at a micron-scale using two novel and complementary characterization techniques, thermal analysis by structural characterization (TASC) and X-ray micro-computed tomography (XμCT) in conjunction with conventional characterization methods.

Method

Complex dispersions containing felodipine, TPGS, PEG and PEO were prepared using hot melt extrusion-injection moulding. The phase separation behavior of the samples was characterized using TASC and XμCT in conjunction with conventional thermal, microscopic and spectroscopic techniques. The in vitro drug release study was performed to demonstrate the impact of phase separation on dissolution of the dispersions.

Results

The conventional characterization results indicated the phase separating nature of the carrier materials in the patches and the presence of crystalline drug in the patches with the highest drug loading (30% w/w). TASC and XμCT where used to provide insight into the spatial configuration of the separate phases. TASC enabled assessment of the increased heterogeneity of the dispersions with increasing the drug loading. XμCT allowed the visualization of the accumulation of phase separated (crystalline) drug clusters at the interface of air pockets in the patches with highest drug loading which led to poor dissolution performance. Semi-quantitative assessment of the phase separated drug clusters in the patches were attempted using XμCT.

Conclusion

TASC and XμCT can provide unique information regarding the phase separation behavior of solid dispersions which can be closely associated with important product quality indicators such as heterogeneity and microstructure.

     

The Effort of Health Management for Workers in Y Combined Cycle Power Plant in Korea

Objective

This study promotes health management activities in Y combined cycle power plants in Korea, focusing on occupational health activities, such as preventing cardiovascular disease and musculoskeletal disorders and managing work environment measurements.

Methods

The results of the present study were collected from the company’s internal documents and reports in Y combined cycle power plant.

Results

Diverse results for workplace activities are summarized. Furthermore, this study discusses attempts to reduce potential safety risks and to improve workers’ health conditions at the Y combined cycle power plants in Korea.

Conclusion

The Y combined cycle plant discussed seeks to prevent accidents to improve workers’ health; thus, specific efforts related to onsite health and expected results for workers are evaluated.

     

Assistance for Predicting Deposition of Tranilast Dry Powder in Pulmonary Airways by Computational Fluid Dynamics

Purpose

Computational fluid dynamics (CFD) simulation was performed to predict deposition behavior of the dry powder inhaler (DPI) formulation in a pulmonary airway model. A synergistic study on CFD simulation and sample preparation with highly branched cyclic dextrin (HBCD) as an excipient matrix for dry powder inhaler formulations of tranilast (TL) were performed.

Methods

The crystal form of TL in spray-dried particles was characterized by powder X-ray diffraction and fluorescence spectroscopy. The aerodynamic performance of DPI formulations was assessed using the Andersen cascade impactor. CFD simulations could simulate the movement of fluids by resolving the mathematic equations governing the movement following Navier-Stokes equations. Particle behavior and deposition from CFD analysis compared with experimental data.

Results

Spray-dried particles (SDPs) of TL/HBCD showed characteristic diffraction peaks differing from untreated TL crystalline in powder X-ray diffraction. The polymorphic transition of TL was also observed in a fluorescence spectrum. Cascade impactor evaluation on SDPs of TL/HBCD at a 40% ethanol ratio demonstrated high inhalation performance with a fine particle fraction of 33%, while SDPs prepared at a 30% ethanol ratio were lower than that of the others. Regarding the cause of this difference, CFD analysis revealed that high inhalation performance was related to the true density and particle size of SDPs. The change in true density of TL associated with polymorphic transition would affect the inhalation performance.

Conclusion

The results on CFD simulations made a prediction about the particle behavior or deposition in pulmonary airways.

     

Continuous Single-Step Wet Granulation with Integrated in-Barrel-Drying

Purpose

It was investigated if continuous wet granulation and drying could be combined in a twin-screw granulator with the aim to provide (pre-)dried granules in a single-step process, i.e. in-barrel-drying.

Methods

To have a consistent and robust material propulsion mechanism, a twin-screw granulator was divided into two compartments. One compartment was operated at lower temperature to granulate and to pre-heat the material, while another compartment was operated at very high temperature to evaporate the granulation liquid as rapidly as possible. Design of experiments was used to investigate the in-barrel-drying process in detail. The process was further investigated for twin-screw wet granulation with API suspension feed, and compared against traditional fluidised-bed drying. Granule and compact properties were evaluated to study the process impact on the product quality.

Results

In-barrel-drying was demonstrated as feasible and yielded completely dried and granulated material at specific settings. The evaporation zone temperature and the processed mass of water were identified as key parameters to balance the evaporation capacity of the process and the material throughput. Granules and compacts showed an acceptable product quality.

Conclusions

In-barrel-drying can be used to condense the wet granulation and drying process steps into one piece of equipment, thereby limiting or even omitting downstream drying process steps.

     

Estimating Maximal <Emphasis Type="BoldItalic">In Vitro</Emphasis> Skin Permeation Flux from Studies Using Non-sink Receptor Phase Conditions

Purpose

This study explored the impact of non-sink receptor conditions on the in vitro skin permeation test (IVPT) and sought to estimate equivalent sink condition IVPT data.

Methods

Simulated diffusion model and experimental IVPT data were generated for ethyl salicylate across human epidermal membranes in Franz diffusion cells using six different receptor phases, with a 10 fold variation in ethyl salicylate solubility.

Results

Both simulated and experimental IVPT – time profiles were markedly affected by receptor phase solubility and receptor sampling rates. Similar sink condition equivalent estimated maximum fluxes were obtained by nonlinear regression and adjustment of linear regression estimates of steady state flux for relative saturation of the receptor phase over time for the four receptor phases in which the ethyl salicylate was relatively soluble. The markedly lower steady - state fluxes found for the other two phases in which ethyl salicylate was less soluble was attributed to an aqueous solution boundary layer effect.

Conclusions

Non-sink receptor phase IVPT data can be used to derive equivalent sink receptor phase IVPT data provided the receptor phase solubility and hydrodynamics are sufficient to minimise the impact of aqueous diffusion layers on IVPT data.

     

Intravenous Poison Hemlock Injection Resulting in Prolonged Respiratory Failure and Encephalopathy

Background

Poison hemlock (Conium maculatum) is a common plant with a significant toxicity. Data on this toxicity is sparse as there have been few case reports and never a documented poisoning after intravenous injection.

Objectives

We present a case of intravenous poison hemlock injection encountered in the emergency department.

Case Report

We describe a 30-year-old male who presented to the emergency department after a brief cardiac arrest after injecting poison hemlock. The patient had return of spontaneous circulation in the emergency department but had prolonged muscular weakness and encephalopathy later requiring tracheostomy.

Conclusion

Intravenous injection of poison hemlock alkaloids can result in significant toxicity, including cardiopulmonary arrest, prolonged weakness, and encephalopathy.

     

Increasing the Bile Acid Sequestration Performance of Cationic Hydrogels by Using an Advanced/Controlled Polymerization Technique

Purpose

To investigate the influence of the polymerization technique and the content of hydroxyl groups on the performance of new bile acid sequestrants based on PAMPMTA-co-PHEA (PAMPTMA: poly((3-acrylamidopropyl)trimethylammonium chloride); PHEA: poly(2-hydroxyethyl acrylate)) hydrogels.

Methods

PAMPMTA-co-PHEA hydrogels were prepared using either free radical polymerization or supplemental activator and reducing agent atom transfer radical polymerization. The chemical structure and composition of the hydrogels was confirmed by both FTIR and ssNMR. The binding of sodium cholate as the model bile salt was evaluated in simulated intestinal fluid using HPLC. The degradation of the polymers was evaluated in vitro in solutions mimicking the gastrointestinal tract environment.

Results

The binding showed that an increase of the amount of HEA in the hydrogel lead to a decrease of the binding capacity. In addition, it was demonstrated for the first time that the hydrogels produced by SARA ATRP presented a higher binding capacity than similar ones produced by FRP. Finally, it was observed that copolymers of PAMPTMA-co-PHEA showed no sign of degradation in solutions mimicking both the stomach and the intestine environment.

Conclusions

The use of an advanced polymerization technique, such as the SARA ATRP, could be beneficial for the preparation of BAS with enhanced performance.

     

Exploring Molecular Speciation and Crystallization Mechanism of Amorphous 2-Phenylamino Nicotinic Acid

Purpose

Molecular understanding of phase stability and transition of the amorphous state helps in formulation and manufacturing of poorly-soluble drugs. Crystallization of a model compound, 2-phenylamino nicotinic acid (2PNA), from the amorphous state was studied using solid-state analytical methods. Our previous report suggests that 2PNA molecules mainly develop intermolecular –COOH???pyridine N (acid-pyridine) interactions in the amorphous state. In the current study, the molecular speciation is explored with regard to the phase transition from the amorphous to the crystalline state.

Methods

Using spectroscopic techniques, the molecular interactions and structural evolvement during the recrystallization from the glassy state were investigated.

Results

The results unveiled that the structurally heterogeneous amorphous state contains acid-pyridine aggregates – either as hydrogen-bonded neutral molecules or as zwitterions – as well as a population of carboxylic acid dimers. Phase transition from the amorphous state results in crystal structures composed of carboxylic acid dimer (acid-acid) synthon or acid-pyridine chains depending on the crystallization conditions employed.

Conclusions

The study underlines the structural evolvement, as well as its impact on the metastability, of amorphous samples from local, supramolecular assemblies to long-range intermolecular ordering through crystallization.

     

Hollow Microparticles as a Superior Delivery System over Solid Microparticles for the Encapsulation of Peptides

Purpose

Peptides are gaining significant interests as therapeutic agents due to their high targeting specificity and potency. However, their low bioavailability and short half-lives limit their massive potential as therapeutics. The use of dense, solid particles of biodegradable polymer as a universal carrier for peptides also has its challenges, such as inefficient peptide release and low bioactivity. In this paper, it was established that hollow microparticles (h-MPs) instead of solid microparticles (s-MPs), as peptide carriers, could improve the release efficiency, while better preserving their bioactivity.

Methods

Glucagon like Peptide-1 (GLP-1) was encapsulated as a model peptide. Mass loss, average molecular weight changes, intraparticle pH, polymer-peptide interaction and release studies, together with bioactivity assessment of the peptide for s-MPs and h-MPs were systematically analyzed and evaluated for efficacy.

Results

The intraparticle pH of s-MPs was as low as 2.64 whereas the pH of h-MPs was 4.99 by day 7. Consequently, 93% of the peptide extracted from h-MPs was still bioactive while only 58% of the peptide extracted from s-MPs was bioactive. Likewise, the cumulative release of GLP-1 by day 14 from h-MPs showed a cumulative amount of 88?±?8% as compared to 33?±?6% for s-MPs.

Conclusions

The cumulative release of peptide can be significantly improved, and the bioactivity can be better preserved by simply using h-MPs instead of s-MPs as carriers.

     

Hyaluronidase Enzyme-responsive Targeted Nanoparticles for Effective Delivery of 5-Fluorouracil in Colon Cancer

Purpose

In this study, we have successfully prepared the hyaluronic acid (HA)-conjugated mesoporous silica nanoparticles loaded with 5-fluorouracil (5-FU) to increase the anticancer efficacy in colon cancers.

Methods

The particles were nanosized and perfectly spherical. In vitro release kinetics clearly showed the enzyme-sensitive release of 5-FU from HA-conjugated 5-FU loaded mesoporous silica nanoparticles (HA/FMSN).

Results

The presence of HA on the surface of nanoparticles targeted the CD44 receptors overexpressed in the colon cancer cells In vitro cell viability and apoptosis assay clearly showed the superior anticancer effect of HA/FMSN in HT29 colon cancer cells. HA/FMSN exhibited a remarkably higher 43% of cells in early apoptosis phase and 55% of cells in late apoptosis phase indicating the superior anticancer effect of HA/FMSN. HA/FMSN exhibited a significant reduction in the tumor burden compared to that of any group. HA/FMSN was 3-fold more effective than free drug and 2-fold more effective than -FU loaded mesoporous silica nanoparticles (FMSN).

Conclusions

Overall, results suggest that the novel delivery strategy could hold enormous potential in colon cancer targeting.

     

Preparation and Preclinical Evaluation of Inhalable Particles Containing Rapamycin and Anti-Tuberculosis Agents for Induction of Autophagy

Purpose

Mycobacterium tuberculosis (Mtb) inhibits host defense mechanisms, including autophagy. We investigated particles containing rapamycin (RAP) alone or in combination with isoniazid (INH) and rifabutin (RFB) for: targeting lung macrophages on inhalation; inducing autophagy; and killing macrophage-resident Mtb and/or augmenting anti-tuberculosis (TB) drugs.

Methods

PLGA and drugs were spray-dried. Pharmacokinetics, partial biodistribution (LC-MS/MS) and efficacy (colony forming units, qPCR, acid fast staining, histopathology) in mice following dry powder inhalation were evaluated.

Results

Aerodynamic diameters of formulations were 0.7–4.7 μm. Inhaled particles reached deep lungs and were phagocytosed by alveolar macrophages, yielding AUC0-48 of 102 compared to 0.1 μg/ml?×?h obtained with equivalent intravenous dose. RAP particles induced more autophagy in Mtb-infected macrophages than solutions. Inhaled particles containing RAP alone in daily, alternate-day and weekly dosing regimens reduced bacterial burden in lungs and spleens, inducing autophagy and phagosome-lysosome fusion. Inhalation of particles containing RAP with INH and RFB cleared the lungs and spleens of culturable bacteria.

Conclusions

Targeting a potent autophagy-inducing agent to airway and lung macrophages alone is feasible, but not sufficient to eliminate Mtb. Combination of macrophage-targeted inhaled RAP with classical anti-TB drugs contributes to restoring tissue architecture and killing Mtb.