Development of a Stable Respiratory Syncytial Virus Pre-Fusion Protein Powder Suitable for a Core-Shell Implant with a Delayed Release in Mice: A Proof of Concept Study.

Currently, there is an increasing interest to apply pre-fusion (pre-F) protein of respiratory syncytial virus (RSV) as antigen for the development of a subunit vaccine. A pre-F-containing powder would increase the flexibility regarding the route of administration. For instance, a pre-F-containing powder could be incorporated into a single-injection system releasing a primer, and after a lag time, a booster. The most challenging aspect, obtaining the booster after a lag time, may be achieved by incorporating the powder into a core encapsulated by a nonporous poly(dl-lactic-co-glycolic acid) (PLGA) shell. We intended to develop a stable freeze-dried pre-F-containing powder. Furthermore, we investigated whether incorporation of this powder into the core-shell implant was feasible and whether this system would induce a delayed RSV virus-neutralizing antibody (VNA) response in mice. The developed pre-F-containing powder, consisting of pre-F in a matrix of inulin, HEPES, sodium chloride, and Tween 80, was stable during freeze-drying and storage for at least 28 days at 60 °C. Incorporation of this powder into the core-shell implant was feasible and the core-shell production process did not affect the stability of pre-F. An in vitro release study showed that pre-F was incompletely released from the core-shell implant after a lag time of 4 weeks. The incomplete release may be the result of pre-F instability within the core-shell implant during the lag time and requires further research. Mice subcutaneously immunized with a pre-F-containing core-shell implant showed a delayed RSV VNA response that corresponded with pre-F release from the core-shell implant after a lag time of approximately 4 weeks. Moreover, pre-F-containing core-shell implants were able to boost RSV VNA titers of primed mice after a lag time of 4 weeks. These findings could contribute to the development of a single-injection pre-F-based vaccine containing a primer and a booster.

The mechanism behind the biphasic pulsatile drug release from physically mixed poly(dl-lactic(-co-glycolic) acid)-based compacts.

Successful immunization often requires a primer, and after a certain lag time, a booster administration of the antigen. To improve the vaccinees' comfort and compliance, a single-injection vaccine formulation with a biphasic pulsatile release would be preferable. Previous work has shown that such a release profile can be obtained with compacts prepared from physical mixtures of various poly(dl-lactic(-co-glycolic) acid) types (Murakami et al., 2000). However, the mechanism behind this release profile is not fully understood. In the present study, the mechanism that leads to this biphasic pulsatile release was investigated by studying the effect of the glass transition temperature (Tg) of the polymer, the temperature of compaction, the compression force, the temperature of the release medium, and the molecular weight of the incorporated drug on the release behavior. Compaction resulted in a porous compact. Once immersed into release medium with a temperature above the Tg of the polymer, the drug was released by diffusion through the pores. Simultaneously, the polymer underwent a transition from the glassy state into the rubbery state. The pores were gradually closed by viscous flow of the polymer and further release was inhibited. After a certain period of time, the polymer matrix ruptured, possibly due to a build-up in osmotic pressure, resulting in a pulsatile release of the remaining amount of drug. The compression force and the molecular weight of the incorporated drug did not influence the release profile. Understanding this mechanism could contribute to further develop single-injection vaccines.

Ovalbumin-containing core-shell implants suitable to obtain a delayed IgG1 antibody response in support of a biphasic pulsatile release profile in mice.

A single-injection vaccine formulation that provides for both a prime and a boost immunization would have various advantages over a multiple-injection regime. For such a vaccine formulation, it is essential that the booster dose is released after a certain, preferably adjustable, lag time. In this study we investigated whether a core-shell based implant, containing ovalbumin as core material and poly(DL-lactic-co-glycolic acid) of various monomer ratios as shell material can be used to obtain such a booster release. An in vitro release study showed that the lag time after which the ovalbumin was released from the core-shell implant increased with increasing lactic to glycolic acid ratio of the polymer and ranged from 3-6 weeks. Fluorescence spectroscopy showed minimal differences between native ovalbumin and ovalbumin from core-shell implants that were incubated until just before the observed in vitro release. In addition, mice immunized with a subcutaneous inserted core-shell implant containing ovalbumin showed an ovalbumin-specific IgG1 antibody response after a lag time of 4 or 6-8 weeks. Moreover, delayed release of ovalbumin caused higher IgG1 antibody titers than conventional subcutaneous vaccination with ovalbumin dissolved in PBS. Collectively, these findings could contribute to the further development of a single-injection vaccine, making multiple injections of the vaccine superfluous.

2,4-Diaminoquinazolines as Dual Toll-like Receptor (TLR) 7/8 Modulators for the Treatment of Hepatitis B Virus.

A novel series of 2,4-diaminoquinazolines was identified as potent dual Toll-like receptor (TLR) 7 and 8 agonists with reduced off-target activity. The stereochemistry of the amino alcohol was found to influence the TLR7/8 selectivity with the ( R) isomer resulting in selective TLR8 agonism. Lead optimization toward a dual agonist afforded ( S)-3-((2-amino-8-fluoroquinazolin-4-yl)amino)hexanol 31 as a potent analog, being structurally different from previously described dual agonists ( McGowan J. Med. Chem. 2016 , 59 , 7936 ). Pharmacokinetic and pharmacodynamic (PK/PD) studies revealed the desired high first pass profile aimed at limiting systemic cytokine activation. In vivo pharmacodynamic studies with lead compound 31 demonstrated production of cytokines consistent with TLR7/8 activation in mice and cynomolgus monkeys and ex vivo inhibition of hepatitis B virus (HBV).

Sustained release of the candidate antiretroviral peptides T-1249 and JNJ54310516-AFP from a rod insert vaginal ring.

Administration of biomacromolecular drugs in effective quantities from conventional vaginal rings is hampered by poor drug permeability in the polymers from which rings are commonly constructed. Here, we report the formulation development and testing of rod insert rings for sustained release of the candidate antiretroviral peptides T-1249 and JNJ54310516-AFP (JNJ peptide), both of which have potential as HIV microbicides. Rod inserts were prepared comprising antiviral peptides T-1249 or JNJ peptide in combination with a hydrophilic excipient (sodium chloride, sodium glutamate, lactose or zinc acetate) dispersed at different loadings within a medical grade silicone elastomer. The inserts were tested for weight change and swelling when immersed in simulated vaginal fluid (SVF). Dye migration into the inserts was also assessed visually over 28 days. In vitro release of T-1249 and JNJ peptide from rings containing various insert types was tested. Weight change and degree of swelling of rods immersed in SVF was dependent on the type and concentration of excipient present. The rods displayed the following rank order in terms of weight change: sodium glutamate > zinc acetate ≈ sodium chloride > lactose. The weight change and degree of swelling of the inserts did not correlate with the level of dye uptake observed. In vitro release of T-1249 was improved through addition of lactose, sodium chloride and sodium glutamate, while release of JNJ peptide was improved through addition of sodium chloride or sodium glutamate. Sustained release of hydrophobic peptides can be achieved using a rod insert ring design formulated to include a hydrophilic excipient. Release rates were dependent upon the type of excipient used. The degree of release improvement with different inserts partially reflects their ability to imbibe surrounding fluid and swell in aqueous environments.

The influence of spray-drying parameters on phase behavior, drug distribution, and in vitro release of injectable microspheres for sustained release.

For ternary solid dispersions, it is indispensable to characterize their structure, phase behavior, and the spatial distribution of the dispersed drug as this might influence the release profile and/or stability of these formulations. This study shows how formulation (feed concentration) and process (feed rate, inlet air temperature, and atomizing air pressure) parameters can influence the characteristics of ternary spray-dried solid dispersions. The microspheres considered here consist of a poly(lactic-co-glycolic acid) (PLGA) surface layer and an underlying polyvinylpyrrolidone (PVP) phase. A poorly soluble active pharmaceutical ingredient (API) was molecularly dispersed in this matrix. Differences were observed in component miscibility, phase heterogeneity, particle size, morphology, as well as API surface coverage for selected spray-drying parameters. Observed differences are likely because of changes in the droplet generation, evaporation, and thus particle formation processes. However, varying particle characteristics did not influence the drug release of the formulations studied, indicating the robustness of this approach to produce particles of consistent drug release characteristics. This is likely because of the fact that the release is dominated by diffusion from the PVP layer through pores in the PLGA surface layer and that observed differences in the latter have no influence on the release.

Influence of formulation composition and process on the characteristics and in vitro release from PLGA-based sustained release injectables.

Understanding and controlling the in vitro release behavior of a formulation is a first step toward rationalized selection of a solubility enhancing formulation strategy with a desired release profile in vivo. Therefore six model formulations, representing three different formulation strategies, were physicochemically analyzed and their in vitro release was determined. Solid dispersions based on a PLGA/PVP matrix were compared to solid dispersions in a pure PLGA matrix. Additionally these solid dispersion strategies were compared to the strategy of particle size reduction by means of an API microsuspension. Depending on composition and manufacturing method, formulations varied in particle size, porosity, phase behavior, surface coverage and physical state of the API. This resulted in observed differences in their in vitro release profile. For the various formulation strategies tested both a porous PLGA-based formulation and PLGA/PVP-based formulations, resulted in vitro in sustained release of the poorly soluble API with over 50% of drug released after 24h. For PLGA-based formulations the porosity was identified as a critical parameter influencing in vitro drug release. For the PLGA/PVP-based formulations the release rate can be tailored by the amount of PLGA present. Particle size reduction resulted in immediate total drug release.

Combination of (M)DSC and surface analysis to study the phase behaviour and drug distribution of ternary solid dispersions.

PURPOSE: Miscibility of the different compounds that make up a solid dispersion based formulation play a crucial role in the drug release profile and physical stability of the solid dispersion as it defines the phase behaviour of the dispersion. The standard technique to obtain information on phase behaviour of a sample is (modulated) differential scanning calorimetry ((M)DSC). However, for ternary mixtures (M)DSC alone is not sufficient to characterize their phase behaviour and to gain insight into the distribution of the active pharmaceutical ingredient (API) in a two-phased polymeric matrix. METHODS: MDSC was combined with complementary surface analysis techniques, specifically time-of-flight secondary ion mass spectrometry (ToF-SIMS) and atomic force microscopy (AFM). Three spray-dried model formulations with varying API/PLGA/PVP ratios were analyzed. RESULTS: MDSC, TOF-SIMS and AFM provided insights into differences in drug distribution via the observed surface coverage for 3 differently composed ternary solid dispersions. CONCLUSIONS: Combining MDSC and surface analysis rendered additional insights in the composition of mixed phases in complex systems, like ternary solid dispersions.

In vivo evaluation of different formulation strategies for sustained release injectables of a poorly soluble HIV protease inhibitor.

At present no scientific rationale exists for selecting a particular enabling strategy to formulate a poorly water-soluble drug, although this is crucial as it will influence the in vivo performance of the resulting formulation. This study provides an insight into this complicated decision making process for a poorly soluble human immunodeficiency virus (HIV) protease inhibitor based upon in vivo test results. A formulation strategy based on the molecular dispersion of this active pharmaceutical ingredient (API) into a biphasic matrix consisting of water-insoluble poly(lactic-co-glycolic acid) (PLGA) and water-soluble polyvinylpyrrolidone (PVP) was evaluated. The long-term in vivo performance of this strategy was compared to that of other solubility enhancing approaches by evaluating exposure of the API in male Beagle dogs. Solid dispersions, based on a PLGA/PVP matrix, were compared to solid dispersions in a pure PLGA matrix. Additionally these solid dispersion strategies were compared to the strategy of particle size reduction by means of an API microsuspension. The in vivo performance of the various formulations over a period of 28days after intramuscular injection was evaluated by the observed initial burst release, plasma concentration-time profiles, time at which maximum plasma levels were reached and the estimated bioavailability. Compared to the other formulation strategies assessed, it was concluded that the addition of PVP in a PLGA matrix resulted in vivo in a more sustained release as well as a higher amount of drug released from the polymeric matrix. This was explained based on the structure of these binary PLGA/PVP matrices where the pore network originating from rapidly dissolving PVP plays a key role. Moreover, the results suggest that the API release from this type of formulation could be delayed by increasing the amount of PLGA in the formulation.

Discovery and early development of TMC647055, a non-nucleoside inhibitor of the hepatitis C virus NS5B polymerase.

Structure-based macrocyclization of a 6-carboxylic acid indole chemotype has yielded potent and selective finger-loop inhibitors of the hepatitis C virus (HCV) NS5B polymerase. Lead optimization in conjunction with in vivo evaluation in rats identified several compounds showing (i) nanomolar potency in HCV replicon cells, (ii) limited toxicity and off-target activities, and (iii) encouraging preclinical pharmacokinetic profiles characterized by high liver distribution. This effort culminated in the identification of TMC647055 (10a), a nonzwitterionic 17-membered-ring macrocycle characterized by high affinity, long polymerase residence time, and broad genotypic coverage. In vitro results of the combination of 10a with the HCV protease inhibitor TMC435 (simeprevir) supported an evaluation of this combination in patients with regard to virus suppression and resistance emergence. In a phase 1b trial with HCV genotype 1-infected patients, 10a was considered to be safe and well-tolerated and demonstrated potent antiviral activity, which was further enhanced in a combination study with TMC435.

Surface characteristics of spray-dried microspheres consisting of PLGA and PVP: relating the influence of heat and humidity to the thermal characteristics of these polymers.

In view of the increasing interest in injectable controlled release formulations for the treatment of chronic diseases, injectable polymeric microspheres consisting of a surface layer of poly(lactic-co-glycolic acid) (PLGA) and an underlying polyvinylpyrrolidone (PVP) layer were previously developed. The present study focuses on the influence of heat and humidity on the surface characteristics of these spray-dried PLGA/PVP microspheres. The response of the polymeric matrix to these factors will provide an insight into the expected release behavior and stability of the formulation. This should result in the development of a drug matrix with desired and tunable characteristics in terms of physicochemical stability and drug release profile, relevant in a later stage of research. Glass transition temperatures (Tgs) and miscibility behavior were analyzed by modulated differential scanning calorimetry (MDSC). Scanning electron microscopy (SEM) provided insight in particle morphology. Atomic force microscopy (AFM) was used to study the nanoscale topography and phase behavior of the samples. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) were utilized for surface chemical analysis and quantification respectively. It could be concluded that the surface characteristics (chemical composition, phase behavior, and topography) of spray-dried PVP/PLGA microparticles were affected by exposure to heat and humidity. When exposed to these conditions, a surface rearrangement occurs whereby an increase of PVP at the surface is observed, coupled with a decrease in PLGA. This phenomenon can be explained based upon the relative thermal characteristics and consequent molecular mobility of the two polymers.

Design and synthesis of HIV-1 protease inhibitors for a long-acting injectable drug application.

The design and synthesis of novel HIV-1 protease inhibitors (PIs) (1-22), which display high potency against HIV-1 wild-type and multi-PI-resistant HIV-mutant clinical isolates, is described. Lead optimization was initiated from compound 1, a Phe-Phe hydroxyethylene peptidomimetic PI, and was directed towards the discovery of new PIs suitable for a long-acting (LA) injectable drug application. Introducing a heterocyclic 6-methoxy-3-pyridinyl or a 6-(dimethylamino)-3-pyridinyl moiety (R(3)) at the para-position of the P1' benzyl fragment generated compounds with antiviral potency in the low single digit nanomolar range. Halogenation or alkylation of the metabolic hot spots on the various aromatic rings resulted in PIs with high stability against degradation in human liver microsomes and low plasma clearance in rats. Replacing the chromanolamine moiety (R(1)) in the P2 protease binding site by a cyclopentanolamine or a cyclohexanolamine derivative provided a series of high clearance PIs (16-22) with EC(50)s on wild-type HIV-1 in the range of 0.8-1.8 nM. PIs 18 and 22, formulated as nanosuspensions, showed gradual but sustained and complete release from the injection site over two months in rats, and were therefore identified as interesting candidates for a LA injectable drug application for treating HIV/AIDS.

TMC647055, a potent nonnucleoside hepatitis C virus NS5B polymerase inhibitor with cross-genotypic coverage.

Hepatitis C virus (HCV) infection is a major global health burden and is associated with an increased risk of liver cirrhosis and hepatocellular carcinoma. There remains an unmet medical need for efficacious and safe direct antivirals with complementary modes of action for combination in treatment regimens to deliver a high cure rate with a short duration of treatment for HCV patients. Here we report the in vitro inhibitory activity, mode of action, binding kinetics, and resistance profile of TMC647055, a novel and potent nonnucleoside inhibitor of the HCV NS5B RNA-dependent RNA polymerase. In vitro combination studies with an HCV NS3/4A protease inhibitor demonstrated potent suppression of HCV RNA replication, confirming the potential for combination of these two classes in the treatment of chronic HCV infection. TMC647055 is a potent nonnucleoside NS5B polymerase inhibitor of HCV replication with a promising in vitro biochemical, kinetic, and virological profile that is currently undergoing clinical evaluation.

Humanized mice recapitulate key features of HIV-1 infection: a novel concept using long-acting anti-retroviral drugs for treating HIV-1.

BACKGROUND: Humanized mice generate a lymphoid system of human origin subsequent to transplantation of human CD34+ cells and thus are highly susceptible to HIV infection. Here we examined the efficacy of antiretroviral treatment (ART) when added to food pellets, and of long-acting (LA) antiretroviral compounds, either as monotherapy or in combination. These studies shall be inspiring for establishing a gold standard of ART, which is easy to administer and well supported by the mice, and for subsequent studies such as latency. Furthermore, they should disclose whether viral breakthrough and emergence of resistance occurs similar as in HIV-infected patients when ART is insufficient. METHODS/PRINCIPAL FINDINGS: NOD/shi-scid/γ(c)null (NOG) mice were used in all experimentations. We first performed pharmacokinetic studies of the drugs used, either added to food pellets (AZT, TDF, 3TC, RTV) or in a LA formulation that permitted once weekly subcutaneous administration (TMC278: non-nucleoside reverse transcriptase inhibitor, TMC181: protease inhibitor). A combination of 3TC, TDF and TMC278-LA or 3TC, TDF, TMC278-LA and TMC181-LA suppressed the viral load to undetectable levels in 15/19 (79%) and 14/14 (100%) mice, respectively. In successfully treated mice, subsequent monotherapy with TMC278-LA resulted in viral breakthrough; in contrast, the two LA compounds together prevented viral breakthrough. Resistance mutations matched the mutations most commonly observed in HIV patients failing therapy. Importantly, viral rebound after interruption of ART, presence of HIV DNA in successfully treated mice and in vitro reactivation of early HIV transcripts point to an existing latent HIV reservoir. CONCLUSIONS/SIGNIFICANCE: This report is a unique description of multiple aspects of HIV infection in humanized mice that comprised efficacy testing of various treatment regimens, including LA compounds, resistance mutation analysis as well as viral rebound after treatment interruption. Humanized mice will be highly valuable for exploring the antiviral potency of new compounds or compounds targeting the latent HIV reservoir.

Finger loop inhibitors of the HCV NS5b polymerase. Part II. Optimization of tetracyclic indole-based macrocycle leading to the discovery of TMC647055.

Optimization of a novel series of macrocyclic indole-based inhibitors of the HCV NS5b polymerase targeting the finger loop domain led to the discovery of lead compounds exhibiting improved potency in cellular assays and superior pharmacokinetic profile. Further lead optimization performed on the most promising unsaturated-bridged subseries provided the clinical candidate 27-cyclohexyl-12,13,16,17-tetrahydro-22-methoxy-11,17-dimethyl-10,10-dioxide-2,19-methano-3,7:4,1-dimetheno-1H,11H-14,10,2,9,11,17-benzoxathiatetraazacyclo docosine-8,18(9H,15H)-dione, TMC647055 (compound 18a). This non-zwitterionic 17-membered ring macrocycle combines nanomolar cellular potency (EC(50) of 82 nM) with minimal associated cell toxicity (CC(50)>20 µM) and promising pharmacokinetic profiles in rats and dogs. TMC647055 is currently being evaluated in the clinic.

Finger-loop inhibitors of the HCV NS5b polymerase. Part 1: Discovery and optimization of novel 1,6- and 2,6-macrocyclic indole series.

Novel conformationaly constrained 1,6- and 2,6-macrocyclic HCV NS5b polymerase inhibitors, in which either the nitrogen or the phenyl ring in the C2 position of the central indole core is tethered to an acylsulfamide acid bioisostere, have been designed and tested for their anti-HCV potency. This transformational route toward non-zwitterionic finger loop-directed inhibitors led to the discovery of derivatives with improved cell potency and pharmacokinetic profile.

Nanoscale surface characterization and miscibility study of a spray-dried injectable polymeric matrix consisting of poly(lactic-co-glycolic acid) and polyvinylpyrrolidone.

Injectable controlled-release formulations are of increasing interest for the treatment of chronic diseases. This study aims to develop and characterize a polymeric matrix for intramuscular or subcutaneous injection, consisting of two biocompatible polymers, particularly suitable for formulating poorly soluble drugs. For this matrix, the water-insoluble polymer poly(lactic-co-glycolic acid) (PLGA) is combined with the water-soluble polymer polyvinylpyrrolidone (PVP). Microparticles of these two polymers were prepared by spray drying. The phase behavior of the samples was studied by means of modulated differential scanning calorimetry and the results showed that phase separation occurred in the bulk sample through evidence of two mixed amorphous phases, namely, a PLGA-rich phase and a PVP-rich phase. Characterization of the samples by scanning electron microscopy demonstrated that the spray-dried particles were hollow with a thin shell. Because of the importance in relation to stability and drug release, information about the surface of the microparticles was collected by different complementary surface analysis techniques. Atomic force microscopy gathered information about the morphology and phase behavior of the microparticle surface. Time-of-flight secondary ion mass spectrometry analysis of the particles revealed that the surface consisted mainly of the PLGA-rich phase. This was confirmed by X-ray photoelectron spectroscopy at an increased sampling depth (≈ 10 nm). Nanothermal analysis proved to be an innovative way to thermally detect the presence of the PLGA-dominated surface layer and the underlying PVP phase. Taken together, this information provides a rational basis for predicting the likely drug release behavior this formulation will display.

Structure-based design of a benzodiazepine scaffold yields a potent allosteric inhibitor of hepatitis C NS5B RNA polymerase.

HCV NS5B polymerase, an essential and virus-specific enzyme, is an important target for drug discovery. Using structure-based design, we optimized a 1,5-benzodiazepine NS5B polymerase inhibitor chemotype into a new sulfone-containing scaffold. The design yielded potent inhibitor (S)-4c (K(D) = 0.79 nM), which has approximately 20-fold greater affinity for NS5B than its carbonyl analogue (R)-2c.

1,5-Benzodiazepine inhibitors of HCV NS5B polymerase.

Optimization through parallel synthesis of a novel series of hepatitis C virus (HCV) NS5B polymerase inhibitors led to the identification of (R)-11-(4-benzyloxy-2-fluorophenyl)-6-hydroxy-3,3-dimethyl-10-(6-methylpyridine-2-carbonyl)-2,3,4,5,10,11-hexahydro-dibenzo[b,e][1,4]diazepin-1-one 11zc and (R)-11-(4-benzyloxy-2-fluorophenyl)-6-hydroxy-3,3-dimethyl-10-(2,5-dimethyloxazol-4-carbonyl)-2,3,4,5,10,11-hexahydro-dibenzo[b,e][1,4]diazepin-1-one 11zk as potent (replicon EC(50)=400nM and 270nM, respectively) and selective (CC(50)>20muM) inhibitors of HCV replication. These data warrant further lead-optimization efforts.