Improving the drug load and in vitro performance of supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS) using polymeric precipitation inhibitors

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.

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.

Functionalized calcium carbonate (FCC) as a novel carrier to solidify supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS)

Functionalized calcium carbonate (FCC), a novel pharmaceutical excipient, has shown promising properties in the field of oral drug delivery. The current study aimed at evaluating the feasibility of FCC as a carrier for the solidification of self-nanoemulsifying drug delivery systems (SNEDDS) containing the poorly water-soluble model drug carvedilol (CRV). Conventional, subsaturated SNEDDS (80 %-SNEDDSliquid) and supersaturated SNEDDS (200 %-SNEDDSliquid) were loaded onto FCC via physical adsorption at three ratios; 2.5:1, 3.0:1 and 3.5:1 (w/w) of FCC:SNEDDSliquid, respectively, generating free-flowing powders (SNEDDSFCC) with drug loading ranging from 0.8 % to 2.6 % (w/w) CRV. The emulsification of SNEDDSFCC in a USP II dissolution setup (in purified water) was characterized using dynamic light scattering, resulting in similar droplet sizes and PDIs as observed for their liquid counterparts. The morphology and physical state of the obtained SNEDDSFCC were characterized using scanning electron microscopy and differential scanning calorimetry. The physical stability and drug release upon dispersion were assessed as a function of storage time. The 200 %-SNEDDSliquid were physically stable for 6 days, however, solidification using FCC stabilized the supersaturated concentrations of CRV for a test period of up to 10 weeks (solidification ratios 3.0:1 and 3.5:1 (FCC:SNEDDSliquid)). SNEDDSFCC achieved an improved rate and extent of drug release upon dispersion compared to the crystalline CRV in tap water (pH 7.5), however, to a lesser extent than their liquid counterparts. After 8 weeks of storage (25 °C at dry conditions), FCC was still able to rapidly release the SNEDDSliquid and demonstrated the same rate and extent of drug release as freshly prepared samples. The solidification of 200 %-SNEDDSliquid in presence of FCC greatly improved the drug loading and showed an enhanced drug release profile compared to the conventional systems. In conclusion, FCC showed potential as a carrier for solidification of SNEDDS and for the development of novel supersaturated solid SNEDDS for the oral delivery of poorly water-soluble drugs.

Evidence of Strong Guest-Host Interactions in Simvastatin Loaded in Mesoporous Silica MCM-41

A rational design of drug delivery systems requires in-depth knowledge not only of the drug itself, in terms of physical state and molecular mobility, but also of how it is distributed among a carrier and its interactions with the host matrix. In this context, this work reports the behavior of simvastatin (SIM) loaded in mesoporous silica MCM-41 matrix (average pore diameter ~3.5 nm) accessed by a set of experimental techniques, evidencing that it exists in an amorphous state (X-ray diffraction, ssNMR, ATR-FTIR, and DSC). The most significant fraction of SIM molecules corresponds to a high thermal resistant population, as shown by thermogravimetry, and which interacts strongly with the MCM silanol groups, as revealed by ATR-FTIR analysis. These findings are supported by Molecular Dynamics (MD) simulations predicting that SIM molecules anchor to the inner pore wall through multiple hydrogen bonds. This anchored molecular fraction lacks a calorimetric and dielectric signature corresponding to a dynamically rigid population. Furthermore, differential scanning calorimetry showed a weak glass transition that is shifted to lower temperatures compared to bulk amorphous SIM. This accelerated molecular population is coherent with an in-pore fraction of molecules distinct from bulklike SIM, as highlighted by MD simulations. MCM-41 loading proved to be a suitable strategy for a long-term stabilization (at least three years) of simvastatin in the amorphous form, whose unanchored population releases at a much higher rate compared to the crystalline drug dissolution. Oppositely, the surface-attached molecules are kept entrapped inside pores even after long-term release assays.

Supersaturation and Precipitation Applicated in Drug Delivery Systems: Development Strategies and Evaluation Approaches

Supersaturation is a promising strategy to improve gastrointestinal absorption of poorly water-soluble drugs. Supersaturation is a metastable state and therefore dissolved drugs often quickly precipitate again. Precipitation inhibitors can prolong the metastable state. Supersaturating drug delivery systems (SDDS) are commonly formulated with precipitation inhibitors, hence the supersaturation is effectively prolonged for absorption, leading to improved bioavailability. This review summarizes the theory of and systemic insight into supersaturation, with the emphasis on biopharmaceutical aspects. Supersaturation research has developed from the generation of supersaturation (pH-shift, prodrug and SDDS) and the inhibition of precipitation (the mechanism of precipitation, the character of precipitation inhibitors and screening precipitation inhibitors). Then, the evaluation approaches to SDDS are discussed, including in vitro, in vivo and in silico studies and in vitro-in vivo correlations. In vitro aspects involve biorelevant medium, biomimetic apparatus and characterization instruments; in vivo aspects involve oral absorption, intestinal perfusion and intestinal content aspiration and in silico aspects involve molecular dynamics simulation and pharmacokinetic simulation. More physiological data of in vitro studies should be taken into account to simulate the in vivo environment. The supersaturation theory should be further completed, especially with regard to physiological conditions.

Combining lipid based drug delivery and amorphous solid dispersions for improved oral drug absorption of a poorly water-soluble drug

Two widely applied enabling drug delivery approaches, self-nanoemulsifying drug delivery systems (SNEDDS) and amorphous solid dispersions (ASD), were combined, with the aim of enhancing physical stability, solubilization and absorption of the model drug ritonavir. Ritonavir was loaded at a concentration above its saturation solubility (S_eq) in the SNEDDS (superSNEDDS, 250% of S_eq). An ASD of ritonavir with polyvinylpyrrolidone-vinyl acetate copolymers (Kollidon® VA64) was prepared by ball milling. Relevant control formulations, which include conventional SNEDDS (90% of S_eq), superSNEDDS with a physical mix of Kollidon® VA64 and ritonavir (superSNEDDS+PM) and an aqueous suspension of ritonavir were used. A pharmacokinetic (PK) study in rats was performed to assess the relative bioavailability of ritonavir after oral administration. This was followed by evaluating the formulations in a novel two-step in vitro lipolysis model simulating rat gastric and intestinal conditions. The addition of a ritonavir containing ASD to superSNEDDS increased the degree of supersaturation from 250% to 275% S_eq in the superSNEDDS and the physical stability (absence of drug recrystallization) of the system from 48 h to 1 month under ambient conditions. The PK study in rats displayed significantly higher C_max and AUC_0-7h (3-fold increase) and faster T_max for superSNEDDS+ASD compared to the conventional SNEDDS whilst containing 3 times less lipid than the latter. Furthermore, superSNEDDS+ASD were able to keep the drug solubilised during in vitro lipolysis to the same degree as the conventional SNEDDS. These findings suggest that dissolving an ASD in a superSNEDDS can contribute to the development of novel oral delivery systems with increased bioavailability for poorly water-soluble drugs.

In Vitro Evaluation of a Solid Supersaturated Self Nanoemulsifying Drug Delivery System (Super-SNEDDS) of Aprepitant for Enhanced Solubility

Aprepitant (APR) belongs to Class II of the Biopharmaceutical Classification System (BCS) because of its low aqueous solubility. The objective of the current work is to develop self-nanoemulsifying drug delivery systems (SNEDDS) of APR to enhance its aqueous solubility. Preformulation studies involving screening of excipients for solubility and emulsification efficiency were carried out. Pseudo ternary phase diagrams were constructed with blends of oil (Imwitor^® 988), cosolvent (Transcutol^® P), and various surfactants (Kolliphor^® RH40, Kolliphor^® ELP, Kolliphor^® HS15). The prepared SNEDDS were characterized for droplet size and nanoemulsion stability after dilution. Supersaturated SNEDDS (super-SNEDDS) were prepared to increase the quantity of loaded APR into the formulations. HPMC, PVP, PVP/VA, and Soluplus^® were used as polymeric precipitation inhibitors (PPI). PPIs were added to the formulations at 5% and 10% by weight. The influence of the PPIs on drug precipitation was investigated. In vitro lipolysis test was carried out to simulate digestion of formulations in the gastrointestinal tract. Optimized super-SNEDDS were formulated into free-flowing granules by adsorption on the porous carriers such as Neusilin^® US2. In vitro dissolution studies of solid super-SNEDDS formulation revealed an increased dissolution rate of the drug due to enhanced solubility. Consequently, a formulation to improve the solubility and potentially bioavailability of the drug was developed.

Comparison of Three Different Aqueous Microenvironments for Enhancing Oral Bioavailability of Sildenafil: Solid Self-Nanoemulsifying Drug Delivery System, Amorphous Microspheres and Crystalline Microspheres

Background

The purpose of this study was to screen various drug delivery systems for improving the aqueous solubility and oral bioavailability of sildenafil. Three representative techniques, solid self-nanoemulsifying drug delivery systems (SNEDDS), amorphous microspheres and crystalline microspheres, were compared.

Methods

Both microspheres systems contained sildenafil:Labrasol:PVP at a weight ratio of 1:1:6. The amorphous microspheres were manufactured using ethanol, while crystalline microspheres were generated using distilled water. Liquid SNEDDS was composed of sildenafil:Labrasol:Transcutol HP:Captex 300 in the ratio of 1:70:15:15 (w:w:w:w). The solidification process in SNEDDS was performed using HDK N20 Pharma as a solid carrier.

Results

The amorphous microspheres appeared spherical with significantly decreased particle size compared to the drug powder. The crystalline microspheres exhibited a rough surface with no major particle-size difference compared with sildenafil powder, indicating that the hydrophilic excipients adhered to the sildenafil crystal. Solid SNEDDS presented a smooth surface, assuming that the oily liquid was adsorbed to the porous solid carrier. According to the physicochemical evaluation, the crystalline state maintained in crystalline microspheres, whereas the crystal state changed to amorphous state in other formulations. Amorphous microspheres, crystalline microspheres and solid SNEDDS produced about 79, 55, 82-fold increased solubility, compared to drug powder. Moreover, the prepared formulations provided a higher dissolution rate (%) and plasma concentration than did the drug powder (performance order; solid SNEDDS ≥ amorphous microspheres ≥ crystalline microspheres > drug powder). Among the formulations, solid SNEDDS demonstrated the highest improvement in oral bioavailability (AUC; 1508.78 ± 343.95 h·ng/mL).

Conclusion

Therefore, solid SNEDDS could be recommended as an oral dosage form for enhancing the oral bioavailability of sildenafil.

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.

A Hyaluronic Acid Functionalized Self-Nano-Emulsifying Drug Delivery System (SNEDDS) for Enhancement in Ciprofloxacin Targeted Delivery against Intracellular Infection

Ciprofloxacin (CIP), a potent anti-bacterial agent of the fluroquinolone family, shows poor solubility and permeability, thus leading to the development of intracellular pathogens induced multi-drug resistance and biofilms formation. To synergistically improve the biopharmaceutical parameters of CIP, a hyaluronic acid (FDA approved biocompatible polymer) functionalized self-nano emulsifying drug delivery system (HA-CIP-SNEDDS) was designed in the present study. SNEDDS formulations were tested via solubility, droplet size, zeta potential, a polydispersity index, thermodynamic stability, surface morphology, solid-state characterization, drug loading/release, cellular uptake, and biocompatibility. The final (HA-CIP-SNEDDS) formulation exhibited a mean droplet size of 50 nm with the 0.3 poly dispersity index and negative zeta potential (-11.4 mV). HA-based SNEDDS containing CIP showed an improved ability to permeate goat intestinal mucus. After 4 h, CIP-SNEDDS showed a 2-fold and HA-CIP-SNEDDS showed a 4-fold permeation enhancement as compared to the free CIP. Moreover, 80% drug release of HA-CIP-SNEDDS was demonstrated to be superior and sustained for 72 h in comparison to free CIP. However, anti-biofilm activity of HA-CIP-SNEDDS against Salmonella typhi was higher than CIP-SNEDDS and free CIP. HA-CIP-SNEDDS exhibited increased biocompatibility and improved oral pharmacokinetics as compared to free CIP. Taken together, HA-CIP-SNEDDS formulation seems to be a promising agent against Salmonella typhi with a strong targeting potential.

Exploring precipitation inhibitors to improve in vivo absorption of cinnarizine from supersaturated lipid-based drug delivery systems

Supersaturated lipid-based drug delivery systems are increasingly being explored as a bio-enabling formulation approach, particularly in preclinical evaluation of poorlywater-soluble drugs. While increasing the drug load through thermally-induced supersaturation resulted in enhanced in vivo exposure for some drugs, for others, such as cinnarizine, supersaturated lipid-based systems have not been found beneficial to increase the in vivo bioavailability. We hypothesized that incorporation of precipitation inhibitors to reduce drug precipitation may address this limitation. Therefore, pharmacokinetic profiles of cinnarizine supersaturated lipid-based drug delivery systems with or without precipitation inhibitors were compared. Five precipitation inhibitors were selected for investigation based on a high throughput screening of twenty-one excipients. In vivo results showed that addition of 5% precipitation inhibitors to long chain monoglyceride (LCM) or medium chain monoglyceride (MCM) formulations showed a general trend of increases in cinnarizine bioavailability, albeit only statistically significantly increased for Poloxamer 407 + LCM system (i.e. 2.7-fold increase in AUC_0-24h compared to LCM without precipitation inhibitors). It appeared that precipitation inhibitors mitigated the risk of in vivo precipitation of cinnarizine from sLBDDS and overall, bioavailability was comparable to that previously reported for cinnarizine after dosing of non-supersaturated lipid systems. In summary, for drugs which are prone to precipitation from supersaturated lipid-based drug delivery systems, such as cinnarizine, inclusion of precipitation inhibitors mitigates this risk and provides the opportunity to maximize exposure which is ideally suited in early efficacy and toxicology evaluation.

Mechanisms of drug solubilization by polar lipids in biorelevant media

Despite the widespread use of lipid excipients in both academic research and oral formulation development, rational selection guidelines are still missing. In the current study, we aimed to establish a link between the molecular structure of commonly used polar lipids and drug solubilization in biorelevant media. The solubilization of fenofibrate by 13 phospholipids, 11 fatty acids and 2 monoglycerides was studied by an in vitro model of the upper GI tract. The main trends were verified with progesterone and danazol. It was revealed that to alter drug solubilization in biorelevant media, the polar lipids must form mixed colloidal aggregates with the bile. Such aggregates are formed when: (1) the polar lipid is used at a sufficiently high concentration (relative to its mixed critical micellar concentration) and (2) its hydrophobic chain has a melting temperature (T_m) < 37 °C. When these two conditions are met, the increased polar lipid chain length increases the drug solubilization capacity. Hence, long chain (C18) unsaturated polar lipids show best drug solubilization, due to the combination of long chain length and low T_m. Polar lipids with T_m significantly higher than 37 °C (e.g. C16 and C18 saturated compounds) do not impact drug solubilization in biorelevant media, due to limited association in mixed colloidal aggregates. The hydrophilic head group also has a dramatic impact on the drug solubilization enhancement, with polar lipids performance decreasing in the order [choline phospholipids] > [monoglycerides] > [fatty acids]. As both the acyl chain and head group types are structural features of the polar lipids, and not of the solubilized drugs, the described trends in drug solubilization should hold true for a variety of hydrophobic molecules.

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.

Effects of different physicochemical characteristics and supersaturation principle of solidified SNEDDS and surface-modified microspheres on the bioavailability of carvedilol

In this study, a solidified self-nanoemulsifying drug delivery system (solidified SNEDDS) and surface-modified microspheres were developed for enhancing the oral bioavailability of carvedilol. Based on the aqueous solubility test, liquid SNEDDS was composed of Peceol™ (oil), Tween® 80 (surfactant), and Labrasol® (co-surfactant) at a weight ratio of 25/50/25, generating the smallest nanoemulsion droplet size. Then, carvedilol was added to liquid SNEDDS and spray-dried with Aerosil® to fabricate the solidified SNEDDS. Surface-modified microspheres were manufactured using copovidone (polymer) and Tween® 80 (surfactant) according to aqueous solubility test results. The proper ratio of copovidone and Tween® 80 was determined based on the solubility and dissolution test. Both prepared formulations and carvedilol powder were compared using four different criteria: physicochemical characteristics, solubility, dissolution, and oral bioavailability. For solidified SNEDDS, carvedilol was encapsulated in liquid SNEDDS and absorbed to the Aerosil® surface, leading to the conversion from a crystalline to an amorphous state. However, the drug maintained its crystal form in the surface-modified microspheres. Round and even-sized particles were attached to the rough surfaces of drug, suggesting that hydrophilic carriers adhered to the hydrophobic drug. All formulations significantly improved drug solubility, dissolution, plasma concentrations, C_max, and AUC compared to carvedilol powder. The parameters were ranked in the following order: solidified SNEDDS > surface-modified microspheres > carvedilol powder. As a result, different solubility-increasing mechanisms provided differences in performance. For carvedilol, the formation of a nano-emulsion in solidified SNEDDS resulted in an efficient supersaturated state, leading to improved solubility (~6.1 fold), dissolution (~1.8 fold), and oral bioavailability (~1.4 fold) that was superior to the hydrophilic microenvironment in surface-modified microspheres.

Nanocomposite systems for precise oral delivery of drugs and biologics

Oral delivery is considered the favoured route of administration for both local and systemic delivery of active molecules. Formulation of drugs in conventional systems and nanoparticles has provided opportunities for targeting the gastrointestinal (GI) tract, increasing drug solubility and bioavailability. Despite the achievements of these delivery approaches, the development of a product with the ability of delivering drug molecules at a specific site and according to patients' needs remains a challenging endeavour. The complexity of the physicochemical properties of colloidal systems, their stability in different regions of the gastrointestinal tract, and interaction with the restrictive biological barriers hampered their success for oral precise medicine. To overcome these issues, nanoparticles have been combined with polymers to create hybrid nanosystems, namely nanocomposites. They offer enormous possibilities of structural and mechanical modifications to both nanoparticles and polymeric matrixes to generate systems with new properties, functions, and applications for oral delivery. In this review, nanocomposites' physicochemical and functional properties intended to target specific regions of the GI tract-oral cavity, stomach, small bowel, and colon-are analysed. In parallel, it is provided an insight in the nanocomposite solutions for oral delivery intended for systemic and local absorption, together with a focus on inflammatory bowel diseases (IBDs). Additional difficulties in managing IBD related to the alteration in the physiology of the intestine are described. Finally, future perspectives and opportunities for advancement in this field are discussed.

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.