Unlocking the full potential of lipid-based formulations using lipophilic salt/ionic liquid forms

Rationalizing Counterion Selection for the Development of Lipophilic Salts: A Case Study with Venetoclax

The use of lipid-based formulations (LBFs) can be hindered by low dose loading due to solubility limitations of candidate drugs in lipid vehicles. Formation of lipophilic salts through pairing these drugs with a lipophilic counterion has been demonstrated as a potential means to enhance dose loading in LBFs. This study investigated the screening of appropriate counterions to form lipophilic salts of the BCS class IV drug venetoclax. The physical properties, lipid solubility, and in vitro performance of the salts were analyzed. This study illustrated the versatility of alkyl sulfates and sulfonates as suitable counterions in lipophilic salt synthesis with up to ∼9-fold higher solubility in medium- and long-chain LBFs when compared to that of the free base form of venetoclax. All salts formulated as LBFs displayed superior in vitro performance when compared to the free base form of the drug due to the higher initial drug loadings in LBFs and increased affinity for colloidal species. Further, in vitro studies confirmed that venetoclax lipophilic salt forms using alkyl chain counterions demonstrated comparable in vitro performance to venetoclax docusate, thus reducing the potential for laxative effects related to docusate administration. High levels of the initial dose loading of venetoclax lipophilic salts were retained in a molecularly dispersed state during dispersion and digestion of the formulation, while also demonstrating increased levels of saturation in biorelevant media. The findings of this study suggest that alkyl chain sulfates and sulfonates can act as a suitable alternative counterion to docusate, facilitating the selection of counterions that can unlock the potential to formulate venetoclax as an LBF.

Are nature's strategies the solutions to the rational design of low-melting, lipophilic ionic liquids?

Ionic liquids (ILs) have emerged as a new class of materials, displaying a unique capability to self-assemble into micelles, liposomes, liquid crystals, and microemulsions. Despite evident interest, advancements in the controlled formation of amphiphilic ILs remain in the early stages. Taking inspiration from nature, we introduced the concept of lipid-like (or lipid-inspired) ILs more than a decade ago, aiming to create very low-melting, highly lipophilic ILs that are potentially bio-innocuous - a combination of attributes that is frequently antithetical but highly desirable from several application-specific standpoints. Lipid-like ILs are a subclass of functional organic liquid salts that include a range of lipidic side chains such as saturated, unsaturated, linear, branched, and thioether while retaining melting points below room temperature. It was observed in several homologous series of [Cnmim] ILs that elongation of N-appended alkyl chains to greater than seven carbons leads to a substantial increase in melting point (Tm) - which is the most characteristic feature of ILs. Accordingly, it is challenging to develop ILs with low Tm values while preserving their hydrophobicity and self-organizing properties. We found that two alternative Tm depressive approaches are useful. One of these is the replacement of the double bonds with thioether moieties in the alkyl chains, as detailed in several published papers detailing the chemistry of these ILs. Employing thiol-ene and thiol-yne click reactions is a facile, robust, and orthogonal method to overcome the challenges associated with the synthesis of alkyl thioether-functionalized ILs. The second approach involves replacing the double bonds with the cisoid cyclopropyl motif, mimicking the strategy used by certain organisms to modulate cell membrane fluidity. This discovery has the potential to greatly impact the utilization of lipid-like ILs in various applications, including gene delivery, lubricants, heat transfer fluids, and haloalkane separations, among others. This feature article presents a concise, historical overview, highlighting key findings from our work while offering speculation about the future trajectory of this de novo class of soft organic-ion materials.

Ionic liquids as the effective technology for enhancing transdermal drug delivery: Design principles, roles, mechanisms, and future challenges

Ionic liquids (ILs) have been proven to be an effective technology for enhancing drug transdermal absorption. However, due to the unique structural components of ILs, the design of efficient ILs and elucidation of action mechanisms remain to be explored. In this review, basic design principles of ideal ILs for transdermal drug delivery system (TDDS) are discussed considering melting point, skin permeability, and toxicity, which depend on the molar ratios, types, functional groups of ions and inter-ionic interactions. Secondly, the contributions of ILs to the development of TDDS through different roles are described: as novel skin penetration enhancers for enhancing transdermal absorption of drugs; as novel solvents for improving the solubility of drugs in carriers; as novel active pharmaceutical ingredients (API-ILs) for regulating skin permeability, solubility, release, and pharmacokinetic behaviors of drugs; and as novel polymers for the development of smart medical materials. Moreover, diverse action mechanisms, mainly including the interactions among ILs, drugs, polymers, and skin components, are summarized. Finally, future challenges related to ILs are discussed, including underlying quantitative structure-activity relationships, complex interaction forces between anions, drugs, polymers and skin microenvironment, long-term stability, and in vivo safety issues. In summary, this article will promote the development of TDDS based on ILs.

Oral Self-Nanoemulsifying System Containing Ionic Liquid of BX795 Is Effective against Genital HSV-2 Infection in Mice

BX795 is an emerging drug candidate that has shown a lot of promise as a next-generation non-nucleoside antiviral agent for the topical treatment of herpes simplex virus type-1 (HSV-1) and herpes simplex virus type-2 (HSV-2) infections. Our studies indicated that BX795 has limited oral bioavailability, which could be attributed to its low and pH-dependent solubility. Lipid-based formulations such as self-nanoemulsifying systems (SNESs) can improve the solubility and oral bioavailability of BX795, but the poor lipid solubility of BX795 further limits the development of SNES. To improve the loading of BX795 into SNES, we evaluated the ability of various bulky and biocompatible anions to transform BX795 into an ionic liquid (IL) with higher lipid solubility. Our studies showed that sodium lauryl sulfate and docusate sodium were able to transform BX795 into IL. Compared to pure BX795, the developed BX795 ILs showed differential in vitro cytocompatibility to HeLa cells but exhibited similar in vitro antiviral activity against HSV-2. Interestingly, BX795 docusate (BX795-Doc), an IL of BX795 with ∼135-fold higher lipid solubility than pure BX795, could be successfully incorporated into an SNES, and the developed BX795-Doc-SNES could readily form nanoemulsions of size ≤200 nm irrespective of the pH of the buffer used for dilution. Our in vitro studies showed that BX795-Doc-SNES retained the inherent antiviral activity against HSV-2 and showed similar in vitro cytocompatibility, indicating the availability of BX795 from the SNES in vitro. Finally, orally delivered SNES containing BX795-Doc showed a significant reduction in HSV-2 infection in mice compared to the untreated control. Thus, the transformation of BX795 into IL and the subsequent incorporation of the BX795 IL into the SNES are an effective strategy to improve oral therapy of genital herpes infection.

Biodegradable Cationic and Ionizable Cationic Lipids: A Roadmap for Safer Pharmaceutical Excipients

Cationic and ionizable cationic lipids are broadly applied as auxiliary agents, but their use is associated with adverse effects. If these excipients are rapidly degraded to endogenously occurring metabolites such as amino acids and fatty acids, their toxic potential can be minimized. So far, synthesized and evaluated biodegradable cationic and ionizable cationic lipids already showed promising results in terms of functionality and safety. Within this review, an overview about the different types of such biodegradable lipids, the available building blocks, their synthesis and cleavage by endogenous enzymes is provided. Moreover, the relationship between the structure of the lipids and their toxicity is described. Their application in drug delivery systems is critically discussed and placed in context with the lead compounds used in mRNA vaccines. Moreover, their use as preservatives is reviewed, guidance for their design is provided, and an outlook on future developments is given.

Combining Isolation-Free and Co-processing Manufacturing Approaches to Access Room Temperature Ionic Liquid Forms of APIs

The addition of non-active components at the point of active pharmaceutical ingredient (API) isolation by means of co-processing is an attractive approach for improving the material properties of APIs. Simultaneously, there is increased interest in the pharmaceutical industry in continuous manufacturing processes. These often consist of liquid feeds which maintain materials in solution and mean that solids handling is avoided until the final step. Such techniques enable new forms of APIs to be used in final dosage forms which have been overlooked due to unfavourable material properties. API-based ionic liquids (API-ILs) are an example of a class of compounds that exhibit exceptional solubility and stability qualities at the cost of their physical characteristics. API-ILs could benefit from isolation-free manufacturing in combination with co-processing approaches to circumvent handling issues and make them viable routes to formulating poorly soluble APIs. However, API-ILs are most commonly synthesised via a batch reaction that produces an insoluble solid by-product. To avoid this, an ion exchange resin protocol was developed to enable the API-IL to be synthesised and purified in a single step, and also produce it in a liquid effluent that can be integrated with other unit operations. Confined agitated bed crystallisation and spray drying are examples of processes that have been adapted to produce or consume liquid feeds and were combined with the ion exchange process to incorporate the API-IL synthesis into isolation-free frameworks and continuous manufacturing streams. This combination of isolation-free and co-processing techniques paves the way towards end-to-end continuous manufacturing of API-IL drug products.

Fast-Fed Variability: Insights into Drug Delivery, Molecular Manifestations, and Regulatory Aspects

Among various drug administration routes, oral drug delivery is preferred and is considered patient-friendly; hence, most of the marketed drugs are available as conventional tablets or capsules. In such cases, the administration of drugs with or without food has tremendous importance on the bioavailability of the drugs. The presence of food may increase (positive effect) or decrease (negative effect) the bioavailability of the drug. Such a positive or negative effect is undesirable since it makes dosage estimation difficult in several diseases. This may lead to an increased propensity for adverse effects of drugs when a positive food effect is perceived. However, a negative food effect may lead to therapeutic insufficiency for patients suffering from life-threatening disorders. This review emphasizes the causes of food effects, formulation strategies to overcome the fast-fed variability, and the regulatory aspects of drugs with food effects, which may open new avenues for researchers to design products that may help to eliminate fast-fed variability.

7,8-Dihydroxyflavone and Neuropsychiatric Disorders: A Translational Perspective from the Mechanism to Drug Development

7,8-Dihydroxyflavone (7,8-DHF) is a kind of natural flavonoid with the potential to cross the blood-brain barrier. 7,8-DHF effectively mimics the effect of brain-derived neurotrophic factor (BDNF) in the brain to selectively activate tyrosine kinase receptor B (TrkB) and downstream signaling pathways, thus playing a neuroprotective role. The preclinical effects of 7,8-DHF have been widely investigated in neuropsychiatric disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), depression, and memory impairment. Besides the effect on TrkB, 7,8-DHF could also function through fighting against oxidative stress, cooperating with estrogen receptors, or regulating intestinal flora. This review focuses on the recent experimental studies on depression, neurodegenerative diseases, and learning and memory functions. Additionally, the structural modification and preparation of 7,8-DHF were also concluded and proposed, hoping to provide a reference for the follow-up research and clinical drug development of 7,8-DHF in the field of neuropsychiatric disorders.

Study and Computational Modeling of Fatty Acid Effects on Drug Solubility in Lipid-Based Systems

Lipid-based systems have many advantages in formulation of poorly water-soluble drugs but issues of a limited solvent capacity are often encountered in development. One of the possible solubilization approaches of especially basic drugs could be the addition of fatty acids to oils but currently, a systematic study is lacking. Therefore, the present work investigated apparently neutral and basic drugs in medium chain triglycerides (MCT) alone and with added either caproic acid (C6), caprylic acid (C8), capric acid (C10) or oleic acid (C18:1) at different levels (5 - 20%, w/w). A miniaturized solubility assay was used together with X-ray diffraction to analyze the residual solid and finally, solubility data were modeled using the conductor-like screening model for real solvents (COSMO-RS). Some drug bases had an MCT solubility of only a few mg/ml or less but addition of fatty acids provided in some formulations exceptional drug loading of up to about 20% (w/w). The solubility changes were in general more pronounced the shorter the chain length was and the longest oleic acid even displayed a negative effect in mixtures of celecoxib and fenofibrate. The COSMO-RS prediction accuracy was highly specific for the given compounds with root mean square errors (RMSE) ranging from an excellent 0.07 to a highest value of 1.12. The latter was obtained with the strongest model base pimozide for which a new solid form was found in some samples. In conclusion, targeting specific molecular interactions with the solute combined with mechanistic modeling provides new tools to advance lipid-based drug delivery.

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.

Docusate-Based Ionic Liquids of Anthelmintic Benzimidazoles Show Improved Pharmaceutical Processability, Lipid Solubility, and in Vitro Activity against Cryptococcus neoformans

As the existing therapeutic modalities for the treatment of cryptococcal meningitis (CM) have suboptimal efficacy, repurposing existing drugs for the treatment of CM is of great interest. The FDA-approved anthelmintic benzimidazoles, albendazole, mebendazole, and flubendazole, have demonstrated potent but variable in vitro activity against Cryptococcus neoformans, the predominant fungal species responsible for CM. We performed molecular docking studies to ascertain the interaction of albendazole, mebendazole, and flubendazole with a C. neoformans β-tubulin structure, which revealed differential binding interactions and explained the different in vitro efficacies reported previously and observed in this investigation. Despite their promising in vitro efficacy, the repurposing of anthelmintic benzimidazoles for oral CM therapy is significantly hampered due to their high crystallinity, poor pharmaceutical processability, low and pH-dependent solubility, and drug precipitation upon entering the intestine, all of which result in low and variable oral bioavailability. Here, we demonstrate that the anthelmintic benzimidazoles can be transformed into partially amorphous low-melting ionic liquids (ILs) with a simple metathesis reaction using amphiphilic sodium docusate as a counterion. In vitro efficacy studies on a laboratory reference and a clinical isolate of C. neoformans showed 2- to 4-fold lower IC₉₀ values for docusate-based ILs compared to the pure anthelmintic benzimidazoles. Furthermore, using a C. neoformans strain with green fluorescent protein (GFP)-tagged β-tubulin and albendazole and its docusate IL as model candidates, we showed that the benzimidazoles and their ILs reduce the viability of C. neoformans by interfering with its microtubule assembly. Unlike pure anthelmintic benzimidazoles, the docusate-based ILs showed excellent solubility in organic solvents and >30-fold higher solubility in bioavailability-enhancing lipid vehicles. Finally, the docusate ILs were successfully incorporated into SoluPlus, a self-assembling biodegradable polymer, which upon dilution with water formed polymeric micelles with a size of <100 nm. Thus, the development of docusate-based ILs represents an effective approach to improve the physicochemical properties and potency of anthelmintic benzimidazoles to facilitate their repurposing and preclinical development for CM therapy.

The Potential of Macroporous Silica-Nanocrystalline Cellulose Combination for Formulating Dry Emulsion Systems with Improved Flow Properties: A DoE Study

The objective of this study was to explore the possible use of a new combination of two excipients, i.e., nanocrystalline cellulose (NCC) and macroporous silica (MS), as matrix materials for the compounding of dry emulsion systems and the effects these two excipients have on the characteristics of dry emulsion powders produced by the spray drying process. A previously developed liquid O/W nanoemulsion, comprised of simvastatin, 1-oleoyl-rac-glycerol, Miglyol 812 and Tween 20, was employed. In order to comprehend the effects that these two matrix formers have on the spray drying process and on dry emulsion powder characteristics, alone and in combination, a DoE (Design of Experiment) approach was used. The physicochemical properties of dry emulsion samples were characterised by atomic force microscopy, scanning electron microscopy, mercury intrusion porosimetry, energy-dispersive X-ray spectroscopy and laser diffraction analysis. Additionally, total release and dissolution experiments were performed to assess drug release from multiple formulations. It was found that the macroporous silica matrix drastically improved flow properties of dry emulsion powders; however, it partially trapped the oil—drug mixture inside the pores and hindered complete release. NCC showed its potential to reduce oil entrapment in MS, but because of its rod-shaped particles deposited on the MS surface, powder flowability was deteriorated.

Lipophilic Salts and Lipid-Based Formulations: Enhancing the Oral Delivery of Octreotide

PURPOSE

Successful oral peptide delivery faces two major hurdles: low enzymatic stability in the gastro-intestinal lumen and poor intestinal membrane permeability. While lipid-based formulations (LBF) have the potential to overcome these barriers, effective formulation of peptides remains challenging. Lipophilic salt (LS) technology can increase the apparent lipophilicity of peptides, making them more suitable for LBF.

METHODS

As a model therapeutic peptide, octreotide (OCT) was converted to the docusate LS (OCT.DoS₂), and compared to the commercial acetate salt (OCT.OAc₂) in oral absorption studies and related in vitro studies, including parallel artificial membrane permeability assay (PAMPA), Caco-2, in situ intestine perfusion, and simulated digestion in vitro models. The in vivo oral absorption of OCT.DoS₂ and OCT.OAc₂ formulated in self-emulsifying drug delivery systems (SEDDS) was studied in rats.

RESULTS

LS formulation improved the solubility and loading of OCT in LBF excipients and OCT.DoS₂ in combination with SEDDS showed higher OCT absorption than the acetate comparator in the in vivo studies in rats. The Caco-2 and in situ intestine perfusion models indicated no increases in permeability for OCT.DoS₂. However, the in vitro digestion studies showed reduced enzymatic degradation of OCT.DoS₂ when formulated in the SEDDS formulations. Further in vitro dissociation and release studies suggest that the enhanced bioavailability of OCT from SEDDS-incorporating OCT.DoS₂ is likely a result of higher partitioning into and prolonged retention within lipid colloid structures.

CONCLUSION

The combination of LS and LBF enhanced the in vivo oral absorption of OCT primarily via the protective effect of LBF sheltering the peptide from gastrointestinal degradation.

Development of a novel cannabinoid-loaded microemulsion towards an improved stability and transdermal delivery

The aim of this study was to develop a stable microemulsion (ME) for transdermal delivery of tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA). The lipid-based vehicles were selected by screening cannabinoid solubility and the emulsifying ability of surfactants. Pseudo-ternary phase diagrams were constructed by formulation of cannabinoids with Capryol® 90 as oil phase, Tween® 80, Solutol® HS15, Procetyl® AWS, and Cremophor® RH40 as surfactants, ethanol as cosurfactant, and distilled water as the aqueous phase. A significant improvement in transmembrane flux (J_ss), permeability coefficient (K_p), and enhancement ratio (E_R) was found in one system compared to other formulations. This ME consisted of 1.0% (w/w) of cannabinoids, 5% (w/w) of Capryol® 90, 44% (w/w) S_mix (2:1, Procetyl® AWS and Ethanol) and 50.0% (w/w) of distilled water. Additionally, the effects of pH on the permeation of the cannabinoids were investigated. Based on the pH value THCA and CBDA-loaded ME exhibited the highest permeation at pH 5.17 and pH 5.25. After storing the pH-adjusted P2 ME and the optimized P2 ME for 180 days at 4℃ and 25℃, the content of cannabinoids was over 95%. Consequently, the cannabinoid-loaded ME system is a promising option for solubilizing and stabilizing lipophilic drugs like cannabinoids and utilize them for transdermal delivery.

Current challenges and future perspectives in oral absorption research: An opinion of the UNGAP network

Although oral drug delivery is the preferred administration route and has been used for centuries, modern drug discovery and development pipelines challenge conventional formulation approaches and highlight the insufficient mechanistic understanding of processes critical to oral drug absorption. This review presents the opinion of UNGAP scientists on four key themes across the oral absorption landscape: (1) specific patient populations, (2) regional differences in the gastrointestinal tract, (3) advanced formulations and (4) food-drug interactions. The differences of oral absorption in pediatric and geriatric populations, the specific issues in colonic absorption, the formulation approaches for poorly water-soluble (small molecules) and poorly permeable (peptides, RNA etc.) drugs, as well as the vast realm of food effects, are some of the topics discussed in detail. The identified controversies and gaps in the current understanding of gastrointestinal absorption-related processes are used to create a roadmap for the future of oral drug absorption research.

Synthesis and Characterization of Lipophilic Salts of Metformin to Improve Its Repurposing for Cancer Therapy

Epidemiological evidence has accentuated the repurposing of metformin hydrochloride for cancer treatment. However, the extreme hydrophilicity and poor permeability of metformin hydrochloride are responsible for its poor anticancer activity in vitro and in vivo. Here, we report the synthesis and characterization of several lipophilic metformin salts containing bulky anionic permeation enhancers such as caprate, laurate, oleate, cholate, and docusate as counterions. Of various counterions tested, only docusate was able to significantly improve the lipophilicity and lipid solubility of metformin. To evaluate the impact of the association of anionic permeation enhancers with metformin, we checked the in vitro anticancer activity of various lipophilic salts of metformin using drug-sensitive (MYCN-2) and drug-resistant (SK-N-Be2c) neuroblastoma cells as model cancer cells. Metformin hydrochloride showed a very low potency (IC50 ≈ >100 mM) against MYCN-2 and SK-N-Be2c cells. Anionic permeation enhancers showed a considerably higher activity (IC50 ≈ 125 μM to 1.6 mM) against MYCN-2 and SK-N-Be2c cells than metformin. The association of metformin with most of the bulky anionic agents negatively impacted the anticancer activity against MYCN-2 and SK-N-Be2c cells. However, metformin docusate showed 700- to 4300-fold improvement in anticancer potency compared to metformin hydrochloride and four- to five-fold higher in vitro anticancer activity compared to sodium docusate, indicating a synergistic association between metformin and docusate. A similar trend was observed when we tested the in vitro activity of metformin docusate, sodium docusate, and metformin hydrochloride against hepatocellular carcinoma (HepG2) and triple-negative breast cancer (MDA-MB-231) cells.

Self-Nano-Emulsifying Drug-Delivery Systems: From the Development to the Current Applications and Challenges in Oral Drug Delivery

Approximately one third of newly discovered drug molecules show insufficient water solubility and therefore low oral bio-availability. Self-nano-emulsifying drug-delivery systems (SNEDDSs) are one of the emerging strategies developed to tackle the issues associated with their oral delivery. SNEDDSs are composed of an oil phase, surfactant, and cosurfactant or cosolvent. SNEDDSs characteristics, their ability to dissolve a drug, and in vivo considerations are determinant factors in the choice of SNEDDSs excipients. A SNEDDS formulation can be optimized through phase diagram approach or statistical design of experiments. The characterization of SNEDDSs includes multiple orthogonal methods required to fully control SNEDDS manufacture, stability, and biological fate. Encapsulating a drug in SNEDDSs can lead to increased solubilization, stability in the gastro-intestinal tract, and absorption, resulting in enhanced bio-availability. The transformation of liquid SNEDDSs into solid dosage forms has been shown to increase the stability and patient compliance. Supersaturated, mucus-permeating, and targeted SNEDDSs can be developed to increase efficacy and patient compliance. Self-emulsification approach has been successful in oral drug delivery. The present review gives an insight of SNEDDSs for the oral administration of both lipophilic and hydrophilic compounds from the experimental bench to marketed products.

Impact of bile salts and a medium chain fatty acid on the physical properties of self-emulsifying drug delivery systems

The aim of this study was the evaluation of the influence of bile salts and fatty acids, important components of intestinal fluids, on physical characteristics of self-emulsifying drug delivery systems (SEDDS) such as size, polydispersity (PDI), zeta potential (Zp), turbidity (T%), cloud point temperature (CPT) and drug release. At this purpose, nonionic (ni-SEDDS) and cationic (c-SEDDS) were emulsified in aqueous media containing increasing concentrations of bile salts (BS) and decanoate (Dec). Zp of ni-SEDDS and c-SEDDS became highly negative at 15 mM BS and Dec. Size of ni-SEDDS decreased of 112 nm and of 76 nm at 15 mM BS and Dec, respectively. Size of c-SEDDS decreased of 53 nm at 15 mM BS, but it was not affected by 15 mM Dec. PDI and T% of ni- and c-SEDDS were lowered as well. CPT of ni-SEDDS increased from 70 °C to 97 °C and 84 °C at 15 mM BS and Dec. CPT of c-SEDDS decreased from above 100 °C to 80 °C and to 85 °C at 1.5 mM BS and at 5 mM Dec, respectively. Generally, BS had a more pronounced effect on SEDDS Zp, size, PDI, T %, and CPT than Dec. The release of the model drug quinine was accelerated by BS and Dec. As BS and fatty acids affect the physical characteristics and drug release behavior of SEDDS, their impact should be addressed during the development process.

Effect of excipients on oral absorption process according to the different gastrointestinal segments

INTRODUCTION

Excipients are necessary to develop oral dosage forms of any Active Pharmaceutical Ingredient (API). Traditionally, excipients have been considered inactive and inert substances, but, over the years, numerous studies have contradicted this belief. This review focuses on the effect of excipients on the physiological variables affecting oral absorption along the different segments of the gastrointestinal tract. The effect of excipients on the segmental absorption variables are illustrated with examples to help understand the complexity of predicting their in vivo effects.

AREAS COVERED

The effects of excipients on disintegration, solubility and dissolution, transit time, and absorption are analyzed in the context of the different gastrointestinal segments and the physiological factors affecting release and membrane permeation. The experimental techniques used to study excipient effects and their human predictive ability are reviewed.

EXPERT OPINION

The observed effects of excipient in oral absorption process have been characterized in the past, mainly in vitro (i.e. in dissolution studies, in vitro cell culture methods or in situ animal studies). Unfortunately, a clear link with their effects in vivo, i.e. their impact on Cmax or AUC, which need a mechanistic approach is still missing. The information compiled in this review leads to the conclusion that the effect of excipients in API oral absorption and bioavailability is undeniable and shows the need of implementing standardized and reproducible preclinical tools coupled with mechanistic and predictive physiological-based models to improve the current empirical retrospective approach.

Discovery of a CNS penetrant small molecule SMN2 splicing modulator with improved tolerability for spinal muscular atrophy

Spinal muscular atrophy (SMA) is a motor neuron disease, typically resulting from loss-of-function mutations in the survival motor neuron 1 (SMN1) gene. Nusinersen/SPINRAZA, a splice-switching oligonucleotide that modulates SMN2 (a paralog of SMN1) splicing and consequently increases SMN protein levels, has a therapeutic effect for SMA. Previously reported small-molecule SMN2 splicing modulators such as risdiplam/EVRYSDI and its analog SMN-C3 modulate not only the splicing of SMN2 but also that of secondary splice targets, including forkhead box protein M1 (FOXM1). Through screening SMA patient-derived fibroblasts, a novel small molecule, designated TEC-1, was identified that selectively modulates SMN2 splicing over three secondary splice targets. TEC-1 did not strongly affect the splicing of FOXM1, and unlike risdiplam, did not induce micronucleus formation. In addition, TEC-1 showed higher selectively on galactosylceramidase and huntingtin gene expression compared to previously reported compounds (e.g., SMN-C3) due to off-target effects on cryptic exon inclusion and nonsense-mediated mRNA decay. Moreover, TEC-1 significantly ameliorated the disease phenotype in an SMA murine model in vivo. Thus, TEC-1 may have promising therapeutic potential for SMA, and our study demonstrates the feasibility of RNA-targeting small-molecule drug development with an improved tolerability profile.

In Vitro Evaluation of Self-Nano-Emulsifying Drug Delivery Systems (SNEDDS) Containing Room Temperature Ionic Liquids (RTILs) for the Oral Delivery of Amphotericin B

Amphotericin B (AmpB), one of the most commonly used agents in the treatment of severe fungal infections and life-threatening parasitic diseases such as visceral Leishmaniasis, has a negligible oral bioavailability, primarily due to a low solubility and permeability. To develop an oral formulation, medium chain triglycerides and nonionic surfactants in a self-nano-emulsifying drug delivery system (SNEDDS) containing AmpB were combined with room temperature ionic liquids (RTILs) of imidazolium. The presence of ionic liquids significantly enhanced the solubility of AmpB, exhibited a low toxicity and increased the transport of AmpB across Caco-2 cell monolayers. The combination of RTILs with a lipid formulation might be a promising strategy to improve the oral bioavailability of AmpB.

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.

Hydrophobic ion pairing (HIP) of (poly)peptide drugs: Benefits and drawbacks of different preparation methods

In order to incorporate hydrophilic macromolecular drugs into lipid-based formulations (LBF), HIP has shown great potential. In this study, different HIP methods were compared with each other. Hydrophobic complexes were formed between bovine serum albumin (BSA) and either dodecyl sulfate, cetyl trimethylammonium or 1,2-dipalmitoyl-sn-glycero-3-phosphate applying the organic solvent-free method, Bligh-Dyer method and biphasic metathesis reaction either with ethyl acetate or chloroform as organic phase. Complex formation efficiency was determined. Hydrophobicity of the obtained complexes was characterized by their apparent partition coefficient between 1-butanol and water. The highest complex formation efficiency was achieved with the Bligh-Dyer method, followed by the organic solvent-free method and the biphasic metathesis reaction. When applying the organic solvent-free method, complex formation efficiency was hampered at higher surfactant concentrations due to the formation of micelles. Furthermore, this method could only be applied for water-soluble compounds. On the contrary, the Bligh-Dyer method was robust towards high surfactant concentrations. Moreover, it enables the use of water-insoluble compounds. The rank order Bligh-Dyer method > organic solvent-free method > biphasic metathesis reaction was confirmed by the log D. According to these results, the Bligh-Dyer method appears advantageous for HIP. However, the organic-solvent free method is an adequate alternative for water-soluble compounds.

Oral formulation strategies to improve the bioavailability and mitigate the food effect of abiraterone acetate

Abiraterone acetate, marketed as Zytiga®, is an antiandrogen medication used in the treatment of prostate cancer. Abiraterone acetate is a BCS Class IV compound associated with several oral delivery challenges. Its low solubility and high lipophilicity lead to poor oral bioavailability (<10%) and a dramatic positive food effect (5-10-fold). Hence, a large dose of abiraterone acetate (1000 mg per day) is prescribed to patients who must fast for at least 1 h before and 2 h after administration. The recent expiry of Zytiga®s' patent has led to the emergence of publications describing improved oral formulation strategies for abiraterone acetate. This review aims to discuss the characteristics of abiraterone acetate that lead to its unfavorable oral delivery, examine the oral formulation strategies that have been applied, and to describe potential alternative oral formulation strategies that have been used for other BCS Class IV drugs, to determine the most valuable strategies to develop novel and improved alternatives to the current commercial product. Specific emphasis of this review is placed on enabling oral formulation strategies that can improve solubilization and bioavailability, reduce the clinical dose and remove the pharmaceutical food effect to ultimately provide prostate cancer patients with a more efficient formulation with greater patient compliance.

API ionic liquids: probing the effect of counterion structure on physical form and lipid solubility

Structure/property relationship of API IL counterions and salt physicochemical properties are investigated, the results highlight the complex interplay involved.

Ionic Liquid Forms of the Antimalarial Lumefantrine in Combination with LFCS Type IIIB Lipid-Based Formulations Preferentially Increase Lipid Solubility, In Vitro Solubilization Behavior and In Vivo Exposure

Lipid based formulations (LBFs) are commonly employed to enhance the absorption of highly lipophilic, poorly water-soluble drugs. However, the utility of LBFs can be limited by low drug solubility in the formulation. Isolation of ionizable drugs as low melting, lipophilic salts or ionic liquids (ILs) provides one means to enhance drug solubility in LBFs. However, whether different ILs benefit from formulation in different LBFs is largely unknown. In the current studies, lumefantrine was isolated as a number of different lipophilic salt/ionic liquid forms and performance was assessed after formulation in a range of LBFs. The solubility of lumefantrine in LBF was enhanced 2- to 80-fold by isolation as the lumefantrine docusate IL when compared to lumefantrine free base. The increase in drug loading subsequently enhanced concentrations in the aqueous phase of model intestinal fluids during in vitro dispersion and digestion testing of the LBF. To assess in vivo performance, the systemic exposure of lumefantrine docusate after administration in Type II-MCF, IIIB-MCF, IIIB-LCF, and IV formulations was evaluated after oral administration to rats. In vivo exposure was compared to control lipid and aqueous suspension formulations of lumefantrine free base. Lumefantrine docusate in the Type IIIB-LCF showed significantly higher plasma exposure compared to all other formulations (up to 35-fold higher). The data suggest that isolation of a lipid-soluble IL, coupled with an appropriate formulation, is a viable means to increase drug dose in an oral formulation and to enhance exposure of lumefantrine in vivo.