New Insights into Using Lipid Based Suspensions for 'Brick Dust' Molecules: Case Study of Nilotinib

Dynamic changes in the distribution equilibrium of drugs in microemulsions associated with drug absorption facilitate the absorption improvement for drugs with low water-solubility by self-microemulsifying drug delivery system (SMEDDS)

Mechanisms for absorption improvement of drugs with low water-solubility by self-microemulsifying drug delivery system (SMEDDS) are still controversial except for solubility improvement. We attempted to clarify the mechanisms by utilizing model drugs classified as biopharmaceutics classification system class II. In the in-vitro transport study for microemulsions (MEs) formed from SMEDDS, the permeation clearance (CLperm,freeSMEDDS) calculated based on free drug concentrations in MEs, was significantly larger than the CLpermsoln for aqueous solution. However, pretreatment of intestinal mucosa with drug-free MEs did not change CLpermsoln so much. The contribution of endocytosis to drug absorption from MEs was negligible. Instead, our novel egg phosphatidylcholine-monolayer-chloroform partition study revealed that drugs were continuously released from ME droplets, and that the distribution equilibrium of drugs in ME dynamically shifted from ME droplets to aqueous phase associated with their partitioning into chloroform phase (i.e. drug absorption). CLperm,freeSMEDDS did not reflect the continuous drug release or the much larger amount of drugs available for absorption than revealed as free concentrations and thereby overestimated the permeation clearance. The absorption improvement by SMEDDS could be attributed to the dynamic changes in the distribution equilibrium of drugs in MEs associated with drug absorption, i.e., the continuous drug release from ME droplets.

Hydrophobic deep eutectic solvent (HDES) as oil phase in lipid-based drug formulations

There is increasing pharmaceutical interest in deep eutectic solvents not only as a green alternative to organic solvents in drug manufacturing, but also as liquid formulation for drug delivery. The present work introduces a hydrophobic deep eutectic solvent (HDES) to the field of lipid-based formulations (LBF). Phase behavior of a mixture with 2:1 M ratio of decanoic- to dodecanoic acid was studied experimentally and described by thermodynamic modelling. Venetoclax was selected as a hydrophobic model drug and studied by atomistic molecular dynamics simulations of the mixtures. As a result, valuable molecular insights were gained into the interaction networks between the different components. Moreover, experimentally the HDES showed greatly enhanced drug solubilization compared to conventional glyceride-based vehicles, but aqueous dispersion behavior was limited. Hence surfactants were studied for their ability to improve aqueous dispersion and addition of Tween 80 resulted in lowest droplet sizes and high in vitro drug release. In conclusion, the combination of HDES with surfactant(s) provides a novel LBF with high pharmaceutical potential. However, the components must be finely balanced to keep the integrity of the solubilizing HDES, while enabling sufficient dispersion and drug release.

Scalable lipid droplet microarray fabrication, validation, and screening

High throughput screening of small molecules and natural products is costly, requiring significant amounts of time, reagents, and operating space. Although microarrays have proven effective in the miniaturization of screening for certain biochemical assays, such as nucleic acid hybridization or antibody binding, they are not widely used for drug discovery in cell culture due to the need for cells to internalize lipophilic drug candidates. Lipid droplet microarrays are a promising solution to this problem as they are capable of delivering lipophilic drugs to cells at dosages comparable to solution delivery. However, the scalablility of the array fabrication, assay validation, and screening steps has limited the utility of this approach. Here we take several new steps to scale up the process for lipid droplet array fabrication, assay validation in cell culture, and drug screening. A nanointaglio printing process has been adapted for use with a printing press. The arrays are stabilized for immersion into aqueous solution using a vapor coating process. In addition to delivery of lipophilic compounds, we found that we are also able to encapsulate and deliver a water-soluble compound in this way. The arrays can be functionalized by extracellular matrix proteins such as collagen prior to cell culture as the mechanism for uptake is based on direct contact with the lipid delivery vehicles rather than diffusion of the drug out of the microarray spots. We demonstrate this method for delivery to 3 different cell types and the screening of 92 natural product extracts on a microarray covering an area of less than 0.1 cm2. The arrays are suitable for miniaturized screening, for instance in high biosafety level facilities where space is limited and for applications where cell numbers are limited, such as in functional precision medicine.

Combination of co-amorphization with SNEDDS outperforms Ofev® in the oral absorption of nintedanib

Nintedanib (NTD), approved for the treatment of idiopathic pulmonary fibrosis and advanced non-small cell lung cancer, is one of brick dusts with high melting point. Although NTD has been marketed as Ofev®, a soft capsule of NTD ethanesulfonate (NTD-ESA) suspended in oil components, the oral bioavailability is quite low and highly variable. To improve the oral absorption behavior of NTD, we prepared SNEDDS formulation containing NTD-(+)-10-camphorsulfonic acid (CSA) complex with 2% HPMCP-50. CSA disrupted the high crystallinity of NTD-ESA and the formed complex, NTD-CSA, was found to be amorphous by DSC and XRPD. NTD-CSA provided solubilities in various vehicles much higher than NTD-ESA. Under the gastric luminal condition, NTD-CSA SNEDDS with or without 2% HPMCP-50 and NTD-CSA powder indicated very good dissolution of NTD from early time periods, while NTD was gradually dissolved until around 60 min from NTD-ESA and Ofev®. Under the small intestinal luminal condition, in contrast, both NTD-CSA SNEDDS formulations almost completely dissolved NTD throughout the experiments, while Ofev®, NTD-CSA, and NTD-ESA exhibited a very poor dissolution of NTD. In the in vivo absorption study, NTD-CSA SNEDDS with 2% HPMCP-50 significantly improved NTD absorption and reduced the inter-individual variation in oral absorption behavior compared with Ofev®.

Enabling superior drug loading in lipid-based formulations with lipophilic salts for a brick dust molecule: Exploration of lipophilic counterions and in vitro-in vivo evaluation

Lipid-based formulations (LbFs) are an extensively used approach for oral delivery of poorly soluble drug compounds in the form of lipid suspension and lipid solution. However, the high target dose and inadequate lipid solubility limit the potential of brick dust molecules to be formulated as LbFs. Thus, the complexation of such molecules with a lipophilic counterion can be a plausible approach to improve the solubility in lipid-based solutions via reducing drug crystallinity and polar surface area. The study aimed to enhance drug loading in lipid solution for Nilotinib (Nil) through complexation or salt formation with different lipophilic counterions. We synthesized different lipophilic salts/ complexes via metathesis reactions and confirmed their formation by 1H NMR and FTIR. Docusate-based lipophilic salt showed improved solubility in medium-chain triglycerides (∼7 to 7.5-fold) and long-chain triglycerides (∼30 to 35-fold) based lipids compared to unformulated crystalline Nil. The increased lipid solubility could be attributed to the reduction in drug crystallinity which was further confirmed by the PXRD and DSC. Prototype LbFs were prepared to evaluate drug loading and their physicochemical characteristics. The findings suggested that structural features of counterion including chain length and lipophilicity affect the drug loading in LbF. In addition, physical stability testing of formulations was performed, inferring that aliphatic sulfate-based LbFs were stable with no sign of drug precipitation or salt disproportionation. An in vitro lipolysis-permeation study revealed that the primary driver of absorptive flux is the solubilization of the drug and reduced amount of lipid. Further, the in vivo characterization was conducted to measure the influence of increased drug load on oral bioavailability. Overall, the results revealed enhanced absorption of lipophilic salt-based LbF over unformulated crystalline Nil and conventional LbF (drug load equivalent to equilibrium solubility) which supports the idea that lipophilic salt-based LbF enhances drug loading, and supersaturation-mediated drug solubilization, unlocking the full potential of LbF.

Utilization of Lipophilic Salt and Phospholipid Complex in Lipid-Based Formulations to Modulate Drug Loading and Oral Bioavailability of Pazopanib

Pazopanib hydrochloride (PAZ) displays strong intermolecular interaction in its crystal lattice structure, limiting its solubility and dissolution. The development of lipid-based formulations (LbFs) resulted in reduced PAZ loading due to solid-state mediated low liposolubility. This study aims to enhance our understanding of PAZ crystallinity by synthesizing a lipophilic salt and phospholipid complex and investigating its impact on the drug loading in LbFs. The synthesized pazopanib lipophilic salt and phospholipid complex were extensively characterized. The solid form of pazopanib docusate (PAZ-DOC) and pazopanib phospholipid complex (PAZ-PLC) indicates a reduction in characteristic diffraction peaks of crystalline PAZ. The lipid formulations were prepared using synthesized PAZ-DOC and PAZ-PLC, where PAZ-DOC demonstrated six fold higher drug solubility than the commercial salt form and twice that of the PAZ-PLC due to differences in the crystallinity. Further, the impact of salt and complex formation was assessed on the aqueous drug solubilization using lipolysis and multimedia dissolution experiments. Moreover, the LbFs showed notably faster dissolution compared to the crystalline PAZ and marketed tablet. In terms of in vivo pharmacokinetics, the PAZ-DOC LbF exhibited a remarkable 11-fold increase in AUC value compared to the crystalline PAZ and a 2.5-fold increase compared to Votrient®. Similarly, PAZ-PLC LbF showed an approximately nine fold increase in drug exposure compared to the crystalline PAZ, and a 2.2-fold increase compared to Votrient®. These findings suggest that disrupting the crystallinity of drugs and incorporating them into LbF could be advantageous for enhancing drug loading and overcoming limitations related to drug absorption.

Developing an in vitro lipolysis model for real-time analysis of drug concentrations during digestion of lipid-based formulations

Understanding the effect of digestion on oral lipid-based drug formulations is a critical step in assessing the impact of the digestive process in the intestine on intraluminal drug concentrations. The classical pH-stat in vitro lipolysis technique has traditionally been applied, however, there is a need to explore the establishment of higher throughput small-scale methods. This study explores the use of alternative lipases with the aim of selecting digestion conditions that permit in-line UV detection for the determination of real-time drug concentrations. A range of immobilised and pre-dissolved lipases were assessed for digestion of lipid-based formulations and compared to digestion with the classical source of lipase, porcine pancreatin. Palatase® 20000 L, a purified liquid lipase, displayed comparable digestion kinetics to porcine pancreatin and drug concentration determined during digestion of a fenofibrate lipid-based formulation were similar between methods. In-line UV analysis using the MicroDISS ProfilerTM demonstrated that drug concentration could be monitored during one hour of dispersion and three hours of digestion for both a medium- and long-chain lipid-based formulations with corresponding results to that obtained from the classical lipolysis method. This method offers opportunities exploring the real-time dynamic drug concentration during dispersion and digestion of lipid-based formulations in a small-scale setup avoiding artifacts as a result of extensive sample preparation.

Early evaluation of opportunities in oral delivery of PROTACs to overcome their molecular challenges

PROteolysis TArgeting Chimeras (PROTACs) offer new opportunities in modern medicine by targeting proteins that are intractable to classic inhibitors. Heterobifunctional in nature, PROTACs are small molecules that offer a unique mechanism of protein degradation by hijacking the ubiquitin-mediated protein degradation pathway, known as the ubiquitin-proteasome system. Herein, we present an analysis on the structural characteristics of this novel chemical modality. Furthermore, we review and discuss the formulation opportunities to overcome the oral delivery challenges of PROTACs in drug discovery.

When it is too much: Identifying butamben excess on the surface of pharmaceutical preformulation samples by Raman mapping

Butamben is a topical local anesthetic which formulation in lipid-based drug delivery systems (DDS) is challenging due to its affinity for hydrophilic excipients. This means that a medium polarity excipient is preferred for the development of a stable nanostructured lipid carrier (NLC) formulation. In turn, in NLC, the type and number of excipients will determine the active pharmaceutical ingredient (API) solubility and the maximum drug upload. To solve this dilemma and get the best formulation, a throughout screening study to evaluate API solubilization in different excipients was carried out. Subsequently, excipients with different solubilization capacities were selected for microscopic evaluation by Raman mapping, and in turn analysis of the distributional homogeneity index (DHI) and standard deviation of the histograms allowed solving the posed question. Design of experiments (DoE) was employed to understand better the interactions between the excipients; linear and higher-order models were obtained with R2 above of 0.8824. Even though DHI is a good parameter to be used as response, an API concentration higher than 30% (w/w) provided a homogeneous surface in case of good miscibility and, in this case, this parameter needs to be employed with an inspection and/or evaluation of other parameters. A curve of concentration vs. mean scores of images proved to be an alternative to identify the saturation/limit of linear range.

Lipid based formulations as supersaturating oral delivery systems: From current to future industrial applications

Lipid-based formulations, in particular supersaturated lipid-based formulations, are important delivery approaches when formulating challenging compounds, as especially low water-soluble compounds profit from delivery in a pre-dissolved state. In this article, the classification of lipid-based formulation is described, followed by a detailed discussion of different supersaturated lipid-based formulations and the recent advances reported in the literature. The supersaturated lipid-based formulations discussed include both the in situ forming supersaturated systems as well as the thermally induced supersaturated lipid-based formulations. The in situ forming drug supersaturation by lipid-based formulations has been widely employed and numerous clinically available products are on the market. There are some scientific gaps in the field, but in general there is a good understanding of the mechanisms driving the success of these systems. For thermally induced supersaturation, the technology is not yet fully understood and developed, hence more research is required in this field to explore the formulations beyond preclinical studies and initial clinical trials.

Enhanced biopharmaceutical performance of brick dust molecule nilotinib via stabilized amorphous nanosuspension using a facile acid-base neutralization approach

"Brick dust" compounds have high lattice energy as manifested by the poor aqueous solubility and suboptimal bioavailability. Nilotinib being a weakly basic brick dust molecule exhibits erratic and limited absorption during gastrointestinal transit, attributed to pre-absorptive factors like pH-dependent solubility, poor dissolution kinetics, and post-absorptive factors including P-gp-mediated drug efflux. In our study, these problems are addressed holistically by the successful fabrication of amorphous nanosuspension by an acid-base neutralization approach. The nanosuspension was obtained via rapid precipitation of nilotinib in an amorphous form and the generated in situ sodium chloride salt assisted in stabilizing the drug-loaded nanosuspension in a cage of salt and micellar stabilizer. Soluplus® and hypromellose acetate succinate (HPMCAS) were employed as a novel combination of stabilizers. Systematic optimization was carried out by employing the I-optimal method using Design Expert® software with a concentration of HPMCAS and Soluplus® as independent variables and evaluating them for responses viz particle size, polydispersity index (PDI), and zeta potential. The resultant nanosuspension showed a mean particle size of 130.5 ± 1.22 nm with a PDI value of 0.27 ± 0.01, and a zeta potential of - 5.21 ± 0.91 mV. The nanosuspension was further characterized for morphology, dissolution, and in vivo pharmacokinetics study. X-ray powder diffraction study of the nano-formulation displayed a halo pattern revealing the amorphous form. Stability studies showed that the nanosuspension remained stable at 40 °C ± 2 °C and 75% RH ± 5% RH for a period of three months. In vitro drug release and solubility study showed threefold and 36-fold enhancement in dissolution and solubility of the nanosuspension. Furthermore, an in vivo pharmacokinetic study in Sprague-Dawley rats following oral administration displayed a 1.46-fold enhancement in the relative bioavailability of the nanosuspension in contrast to neat nilotinib.

Leveraging the use of in vitro and computational methods to support the development of enabling oral drug products: An InPharma commentary

Due to the strong tendency towards poorly soluble drugs in modern development pipelines, enabling drug formulations such as amorphous solid dispersions, cyclodextrins, co-crystals and lipid-based formulations are frequently applied to solubilize or generate supersaturation in gastrointestinal fluids, thus enhancing oral drug absorption. Although many innovative in vitro and in silico tools have been introduced in recent years to aid development of enabling formulations, significant knowledge gaps still exist with respect to how best to implement them. As a result, the development strategy for enabling formulations varies considerably within the industry and many elements of empiricism remain. The InPharma network aims to advance a mechanistic, animal-free approach to the assessment of drug developability. This commentary focuses current status and next steps that will be taken in InPharma to identify and fully utilize 'best practice' in vitro and in silico tools for use in physiologically based biopharmaceutic models.

Serum and lymph pharmacokinetics of nilotinib delivered by yeast glucan particles per os

Nilotinib is a selective tyrosine-kinase inhibitor approved for the treatment of chronic myeloid leukemia. It is poorly soluble in aqueous media and has a low oral bioavailability. Nilotinib encapsulation into yeast glucan particles (GPs) was investigated in this work as a means of increasing bioavailability. The amorphization of nilotinib in GPs resulted in an increased dissolution rate, which was confirmed by in vitro experiments using biorelevant dissolution media. Simultaneously, GPs containing nilotinib were effectively taken up by macrophages, which was quantified in vitro on cell cultures. The overall oral bioavailability in a rat model was approximately 39 % for nilotinib delivered in a reference formulation (Tasigna) and was almost doubled when delivered in GPs. The contribution of glucan particles to the lymphatic transport of nilotinib was quantified. When delivered by GPs, cumulative nilotinib absorption via the lymphatic system increased by a factor of 10.8 compared to the reference, but still represented arelative bioavailability of only 1.12 %. The cumulative uptake of GPs in the lymph was found to be 0.54 mg after a single dose of 50 mg. Yeast glucan particles can therefore serve as a drug delivery vehicle with a dual function: dissolution rate enhancement by amorphization, and, to asmaller extent, lymphatic delivery due to macrophage uptake.

Formation of a Stable Co-Amorphous System for a Brick Dust Molecule by Utilizing Sodium Taurocholate with High Glass Transition Temperature

Brick dust molecules are usually poorly soluble in water and lipoidal components, making it difficult to formulate them in dosage forms that provide efficient pharmacological effects. A co-amorphous system is an effective strategy to resolve these issues. However, their glass transition temperatures (Tg) are relatively lower than those of polymeric amorphous solid dispersions, suggesting the instability of the co-amorphous system. This study aimed to formulate a stable co-amorphous system for brick dust molecules by utilizing sodium taurocholate (NaTC) with a higher Tg. A novel neuropeptide Y5 receptor antagonist (AntiY5R) and NaTC with Tg of 155 °C were used as the brick dust model and coformer, respectively. Ball milling formed a co-amorphous system for AntiY5R and NaTC (AntiY5R-NaTC) at various molar ratios. Deviation from the theoretical Tg value and peak shifts in Fourier-transform infrared spectroscopy indicated intermolecular interactions between AntiY5R and NaTC. AntiY5R-NaTC at equal molar ratios resulting in an 8.5-fold increase in AntiY5R solubility over its crystalline form. The co-amorphous system remained amorphous for 1 month at 25 °C and 40 °C. These results suggest that the co-amorphous system formed by utilizing NaTC as a coformer could stably maintain the amorphous state and enhance the solubility of brick dust molecules.

Intrinsic lipolysis rate for systematic design of lipid-based formulations

Lipid-based formulations (LBFs) are used by the pharmaceutical industry in oral delivery systems for both poorly water-soluble drugs and biologics. Digestibility is key for the performance of LBFs and in vitro lipolysis is commonly used to compare the digestibility of LBFs. Results from in vitro lipolysis experiments depend highly on the experimental conditions and formulation characteristics, such as droplet size (which defines the surface area available for digestion) and interfacial structure. This study introduced the intrinsic lipolysis rate (ILR) as a surface area-independent approach to compare lipid digestibility. Pure acylglycerol nanoemulsions, stabilized with polysorbate 80 at low concentration, were formulated and digested according to a standardized pH-stat lipolysis protocol. A methodology originally developed to calculate the intrinsic dissolution rate of poorly water-soluble drugs was adapted for the rapid calculation of ILR from lipolysis data. The impact of surfactant concentration on the apparent lipolysis rate and lipid structure on ILR was systematically investigated. The surfactant polysorbate 80 inhibited lipolysis of tricaprylin nanoemulsions in a concentration-dependent manner. Coarse-grained molecular dynamics simulations supported these experimental observations. In the absence of bile and phospholipids, tricaprylin was shielded from lipase at 0.25% polysorbate 80. In contrast, the inclusion of bile salt and phospholipid increased the surfactant-free area and improved the colloidal presentation of the lipids to the enzyme, especially at 0.125% polysorbate 80. At a constant and low surfactant content, acylglycerol digestibility increased with decreasing acyl chain length, decreased esterification, and increasing unsaturation. The calculated ILR of pure acylglycerols was successfully used to accurately predict the IRL of binary lipid mixtures. The ILR measurements hold great promise as an efficient method supporting pharmaceutical formulation scientists in the design of LBFs with specific digestion profiles.

A Customized Screening Tool Approach for the Development of a Self-Nanoemulsifying Drug Delivery System (SNEDDS)

The present study focused on establishing a novel, (pre-)screening approach that enables the development of promising performing self-nanoemulsifying drug delivery systems (SNEDDSs) with a limited number of experiments. The strategic approach was based on first identifying appropriate excipients (oils/lipids, surfactants, and co-solvents) providing a high saturation solubility for lipophilic model compounds with poor aqueous solubility. Excipients meeting these requirements were selected for SNEDDS development, and a special triangular mixture design was applied for determining excipient ratios for the SNEDDS formulations. Celecoxib and fenofibrate were used as model drugs. Formulations were studied applying a specific combination of in vitro characterization methods. Specifications for a promising SNEDDS formulation were self-imposed: a very small droplet size (< 50 nm), a narrow size distribution of these droplets (PDI < 0.15) and a high transmittance following SNEDDS dispersion in water (> 99% in comparison with purified water). Excipients that provided a nanoemulsion after dispersion were combined, and ratios were optimized using a customized mapping method in a triangular mixture design. The best performing formulations were finally studied for their in vitro release performance. Results of the study demonstrate the efficiency of the customized screening tool approach. Since it enables successful SNEDDS development in a short time with manageable resources, this novel screening tool approach could play an important role in future SNEDDS development.

Pharmaceutical Lauryl Sulfate Salts: Prevalence, Formation Rules, and Formulation Implications

The anionic surfactant sodium lauryl sulfate (SLS) is known to deteriorate the dissolution of some drugs by forming poorly soluble lauryl sulfate (LS) salts. However, because of the perception of its infrequent occurrence, this phenomenon is usually not investigated in drug development until unexpected dissolution slowdown is encountered. This work demonstrates the prevalence of this phenomenon, where 14 out of 18 compounds with diverse chemical structures, including salts of basic drugs, a quaternary ammonium salt, organic bases, and zwitterionic molecules, precipitated from a solution when mixed with SLS. Although no precipitation was observed for the other 4 compounds, their FTIR spectra suggested 3 of them had intermolecular interactions with SLS when dried from a solution. These results, along with the 5 other examples reported in the literature, demonstrate the prevalence of this phenomenon. The occurrence of precipitation is thermodynamically driven by the relative difference between the ion product in solution (Q) and the solubility product of the lauryl sulfate salt (K_sp). SLS, as a surfactant, also affects precipitation kinetics by influencing the interfacial tension of nuclei of the insoluble salt. When a potential issue associated with the LS salt is identified, effective mitigation strategies should be proactively designed and implemented to alleviate its possible negative impact on drug dissolution.

Lipophilic Salts and Lipid-Based Formulations for Bridging the Food Effect Gap of Venetoclax

Lipid based formulations (LBF) have shown to overcome food dependent bioavailability for some poorly water-soluble drugs. However, the utility of LBFs can be limited by low dose loading due to a low drug solubility in LBF vehicles. This study investigated the solubility and drug loading increases in LBFs using lipophilic counterions to form lipophilic salts of venetoclax. Venetoclax docusate was formed from venetoclax free base and verified by ¹H NMR. Formation of stable venetoclax-fatty acid associations with either oleic acid or decanoic acid were attempted, however, the molecular associations were less consistent based on ¹H NMR. Venetoclax docusate displayed a up to 6.2-fold higher solubility in self-emulsifying drug delivery systems (SEDDS) when compared to the venetoclax free base solubility resulting in a higher dose loading. A subsequent bioavailability study in landrace pigs demonstrated a 2.5-fold higher bioavailability for the lipophilic salt containing long chain SEDDS compared to the commercially available solid dispersion Venclyxto® in the fasted state. The bioavailability of all lipophilic salt SEDDS in the fasted state was similar to Venclyxto® in the fed state. This study confirmed that lipophilic drug salts increase the dose loading in LBFs and showed that lipophilic salt-SEDDS combinations may be able to overcome bioavailability limitations of drugs with low inherent dose loading in lipid vehicles. Furthermore, the present study demonstrated the utility of a LBF approach, in combination with lipophilic salts, to overcome food dependent variable oral bioavailability of drugs.

Supersaturation and Solubilization upon In Vitro Digestion of Fenofibrate Type I Lipid Formulations: Effect of Droplet Size, Surfactant Concentration and Lipid Type

Lipid-based formulations (LBF) enhance oral drug absorption by promoting drug solubilization and supersaturation. The aim of the study was to determine the effect of the lipid carrier type, drop size and surfactant concentration on the rate of fenofibrate release in a bicarbonate-based in vitro digestion model. The effect of the lipid carrier was studied by preparing type I LBF with drop size ≈ 2 µm, based on medium-chain triglycerides (MCT), sunflower oil (SFO), coconut oil (CNO) and cocoa butter (CB). The drop size and surfactant concentration effects were assessed by studying MCT and SFO-based formulations with a drop size between 400 nm and 14 µm and surfactant concentrations of 1 or 10%. A filtration through a 200 nm filter followed by HPLC analysis was used to determine the aqueous fenofibrate, whereas lipid digestion was followed by gas chromatography. Shorter-chain triglycerides were key in promoting a faster drug release. The fenofibrate release from long-chain triglyceride formulations (SFO, CNO and CB) was governed by solubilization and was enhanced at a smaller droplet size and higher surfactant concentration. In contrast, supersaturation was observed after the digestion of MCT emulsions. In this case, a smaller drop size and higher surfactant had negative effects: lower peak fenofibrate concentrations and a faster onset of precipitation were observed. The study provides new mechanistic insights on drug solubilization and supersaturation after LBF digestion, and may support the development of new in silico prediction models.

In Silico, In Vitro, and In Vivo Evaluation of Precipitation Inhibitors in Supersaturated Lipid-Based Formulations of Venetoclax

The concept of using precipitation inhibitors (PIs) to sustain supersaturation is well established for amorphous formulations but less in the case of lipid-based formulations (LBF). This study applied a systematic in silico–in vitro–in vivo approach to assess the merits of incorporating PIs in supersaturated LBFs (sLBF) using the model drug venetoclax. sLBFs containing hydroxypropyl methylcellulose (HPMC), hydroxypropyl methylcellulose acetate succinate (HPMCAS), polyvinylpyrrolidone (PVP), PVP-co-vinyl acetate (PVP/VA), Pluronic F108, and Eudragit EPO were assessed in silico calculating a drug–excipient mixing enthalpy, in vitro using a PI solvent shift test, and finally, bioavailability was assessed in vivo in landrace pigs. The estimation of pure interaction enthalpies of the drug and the excipient was deemed useful in determining the most promising PIs for venetoclax. The sLBF alone (i.e., no PI present) displayed a high initial drug concentration in the aqueous phase during in vitro screening. sLBF with Pluronic F108 displayed the highest venetoclax concentration in the aqueous phase and sLBF with Eudragit EPO the lowest. In vivo, the sLBF alone showed the highest bioavailability of 26.3 ± 14.2%. Interestingly, a trend toward a decreasing bioavailability was observed for sLBF containing PIs, with PVP/VA being significantly lower compared to sLBF alone. In conclusion, the ability of a sLBF to generate supersaturated concentrations of venetoclax in vitro was translated into increased absorption in vivo. While in silico and in vitro PI screening suggested benefits in terms of prolonged supersaturation, the addition of a PI did not increase in vivo bioavailability. The findings of this study are of particular relevance to pre-clinical drug development, where the high in vivo exposure of venetoclax was achieved using a sLBF approach, and despite the perceived risk of drug precipitation from a sLBF, including a PI may not be merited in all cases.

Novel Biphasic Lipolysis Method To Predict in Vivo Performance of Lipid-Based Formulations

The absence of an intestinal absorption sink is a significant weakness of standard in vitro lipolysis methods, potentially leading to poor prediction of in vivo performance and an overestimation of drug precipitation. In addition, the majority of the described lipolysis methods only attempt to simulate intestinal conditions, thus overlooking any supersaturation or precipitation of ionizable drugs as they transition from the acidic gastric environment to the more neutral conditions of the intestine. The aim of this study was to develop a novel lipolysis method incorporating a two-stage gastric-to-intestinal transition and an absorptive compartment to reliably predict in vivo performance of lipid-based formulations (LBFs). Drug absorption was mimicked by in situ quantification of drug partitioning into a decanol layer. The method was used to characterize LBFs from four studies described in the literature, involving three model drugs (i.e., nilotinib, fenofibrate, and danazol) where in vivo bioavailability data have previously been reported. The results from the novel biphasic lipolysis method were compared to those of the standard pH-stat method in terms of reliability for predicting the in vivo performance. For three of the studies, the novel biphasic lipolysis method more reliably predicted the in vivo bioavailability compared to the standard pH-stat method. In contrast, the standard pH-stat method was found to produce more predictive results for one study involving a series of LBFs composed of the soybean oil, glyceryl monolinoleate (Maisine CC), Kolliphor EL, and ethanol. This result was surprising and could reflect that increasing concentrations of ethanol (as a cosolvent) in the formulations may have resulted in greater partitioning of the drug into the decanol absorptive compartment. In addition to the improved predictivity for most of the investigated systems, this biphasic lipolysis method also uses in situ analysis and avoids time- and resource-intensive sample analysis steps, thereby facilitating a higher throughput capacity and biorelevant approach for characterization of LBFs.

Exploring the Impact of Surfactant Type and Digestion: Highly Digestible Surfactants Improve Oral Bioavailability of Nilotinib

The scientific rationale for selection of the surfactant type during oral formulation development requires an in-depth understanding of the interplay between surfactant characteristics and biopharmaceutical factors. Currently, however, there is a lack of comprehensive knowledge of how surfactant properties, such as hydrophilic-lipophilic balance (HLB), digestibility, and fatty acid (FA) chain length, translate into in vivo performance. In the present study, the relationship between surfactant properties, in vitro characteristics, and in vivo bioavailability was systematically evaluated. An in vitro lipolysis model was used to study the digestibility of a variety of nonionic surfactants. Eight surfactants and one surfactant mixture were selected for further analysis using the model poorly water-soluble drug nilotinib. In vitro lipolysis of all nilotinib formulations was performed, followed by an in vivo pharmacokinetic evaluation in rats. The in vitro lipolysis studies showed that medium-chain FA-based surfactants were more readily digested compared to long-chain surfactants. The in vivo study demonstrated that a Tween 20 formulation significantly enhanced the absolute bioavailability of nilotinib up to 5.2-fold relative to an aqueous suspension. In general, surfactants that were highly digestible in vitro tended to display higher bioavailability of nilotinib in vivo. The bioavailability may additionally be related to the FA chain length of digestible surfactants with an improved exposure in the case of medium-chain FA-based surfactants. There was no apparent relationship between the HLB value of surfactants and the in vivo bioavailability of nilotinib. The impact of this study's findings suggests that when designing surfactant-based formulations to enhance oral bioavailability of the poorly water-soluble drug nilotinib, highly digestible, medium chain-based surfactants are preferred. Additionally, for low-permeability drugs such as nilotinib, which is subject to efflux by intestinal P-glycoprotein, the biopharmaceutical effects of surfactants merit further consideration.

Supersaturated Lipid-Based Formulations to Enhance the Oral Bioavailability of Venetoclax

Increasing numbers of beyond Rule-of-Five drugs are emerging from discovery pipelines, generating a need for bio-enabling formulation approaches, such as lipid-based formulations (LBF), to ensure maximal in vivo exposure. However, many drug candidates display insufficient lipid solubility, leading to dose-loading limitations in LBFs. The aim of this study was to explore the potential of supersaturated LBFs (sLBF) for the beyond Rule-of-Five drug venetoclax. Temperature-induced sLBFs of venetoclax were obtained in olive oil, Captex^® 1000, Peceol^® and Capmul MCM^®, respectively. A Peceol^®-based sLBF displayed the highest drug loading and was therefore evaluated further. In vitro lipolysis demonstrated that the Peceol^®-based sLBF was able to generate higher venetoclax concentrations in the aqueous phase compared to a Peceol^®-based suspension and an aqueous suspension. A subsequent bioavailability study in pigs demonstrated for sLBF a 3.8-fold and 2.1-fold higher bioavailability compared to the drug powder and Peceol^®-based suspension, respectively. In conclusion, sLBF is a promising bio-enabling formulation approach to enhance in vivo exposure of beyond Rule-of-Five drugs, such as venetoclax. The in vitro lipolysis results correctly predicted a higher exposure of the sLBF in vivo. The findings of this study are of particular relevance to pre-clinical drug development, where maximum exposure is required.

Chase Dosing of Lipid Formulations to Enhance Oral Bioavailability of Nilotinib in Rats

PURPOSE

Lipid-based formulations (LBF) have shown oral bioavailability enhancement of lipophilic drugs, but not necessarily in the case of hydrophobic drugs. This study explored the potential of lipid vehicles to improve the bioavailability of the hydrophobic drug nilotinib comparing a chase dosing approach and lipid suspensions.

METHODS

Nilotinib in vivo bioavailability in rats was determined after administering an aqueous suspension chase dosed with blank olive oil, Captex 1000, Peceol or Capmul MCM, respectively. Absolute bioavailability was determined (relative to an intravenous formulation). Pharmacokinetic parameters were compared to lipid suspensions.

RESULTS

Compared to the lipid suspensions, the chase dosed lipids showed a 2- to 7-fold higher bioavailability. Both long chain chase dosed excipients also significantly increased the bioavailability up to 2-fold compared to the aqueous suspension. Deconvolution of the pharmacokinetic data indicated that chase dosing of nilotinib resulted in prolonged absorption compared to the aqueous suspension.

CONCLUSION

Chase dosed LBF enhanced the in vivo bioavailability of nilotinib. Long chain lipids showed superior performance compared to medium chain lipids. Chase dosing appeared to prolong the absorption phase of the drug. Therefore, chase dosing of LBF is favourable compared to lipid suspensions for 'brick dust' molecules such as nilotinib. Graphical Abstract The potential of bio-enabling lipid vehicles, administered via chase dosing and lipid suspensions, has been evaluated as an approach to enhance oral bioavailability of nilotinib.

Supersaturated-Silica Lipid Hybrids Improve in Vitro Solubilization of Abiraterone Acetate

PURPOSE

Abiraterone acetate (AbA) is a poorly water-soluble drug with an oral bioavailability of <10% and a significant pharmaceutical food effect. We aimed to develop a more efficient oral solid-state lipid-based formulation for AbA using a supersaturated silica-lipid hybrid (super-SLH) approach to achieve high drug loading, improve in vitro solubilization and mitigate the food effect, while gaining a mechanistic insight into how super-SLH are digested and release drug.

METHODS

The influence of super-SLH saturation level and lipid type on the physicochemical properties and in vitro solubilization during lipolysis of the formulations was investigated and compared to the commercial product, Zytiga.

RESULTS

Super-SLH achieved significantly greater levels of AbA solubilization compared to Zytiga. Solubilization was influenced by the AbA saturation level, which determined the solid state of AbA and the relative amount of lipid, and the lipid utilized, which determined its degree of digestion and the affinity of the lipid and digestion products to the silica. A fine balance existed between achieving high drug loads using supersaturation and improving performance using the lipid-based formulation approach. The non-supersaturated SLH prepared with Capmul PG8 mitigated the 3-fold in vitro food effect.

CONCLUSION

SLH and super-SLH improve in vitro solubilization of AbA, remove the food effect and demonstrate potential to improve oral bioavailability in vivo. Graphical Abstract Abiraterone acetate was formulated as silica-lipid hybrids and demonstrated enhanced in vitro solubilization in comparison to pure abiraterone acetate and commercial product, Zytiga.