Bioavailability enhancement of a BCS IV compound via an amorphous combination product containing ritonavir

Development and evaluation of ultradeformable vesicles loaded transdermal film of boswellic acid

Background

Boswellic acid (BA), a phytoconstituent obtained from Boswellia serrata, suffers from several limitations after oral administration such as poor systemic absorption, high first-pass metabolism and high frequency of dose requirement, which creates a need to develop an alternative route for drug administration via novel drug delivery formulation. The present research work aims at developing ultradeformable vesicular carriers (transferosomes) for transdermal delivery of boswellic acid to effectively deliver the drug into deeper layers of the skin reaching the target site and thus improving its systemic bioavailability. Ultradeformable vesicles were prepared by thin-film hydration technique, and the formulation was optimized using 32 full factorial design where the amount of lecithin (mg) and concentration of surfactant (%) were considered as independent variables. The formulated boswellic acid-loaded vesicles were incorporated into transdermal film via solvent evaporation technique using the blend of polymers such as starch and HPMC K4M.

Results

The BA-loaded transferosomes were optimized based on vesicle size (nm) and drug entrapment efficiency (%EE), and the results were found to be 205.4 ± 1.215 nm and 86.39 ± 0.019%, respectively. Transmission electron microscopy (TEM) of optimized batch showed spherical shape of vesicles with identified lamellarity, surface charge of vesicles with high negative value − 15.2 mV that suggests electrostatic repulsion between vesicles, while the formulation showed good deformability index of 11.31 ± 0.032% due to use of Tween 80 as surfactant. In vitro permeation study demonstrated sustained release pattern of 96.53 ± 0.023% up to 24 h. Also, the in vitro drug diffusion study was carried out for transfersomal transdermal film which exhibited enhanced permeation and sustained retention of drug up to 94.71 ± 0.019% for 24 h.

Conclusion

Accordingly, the research work suggested that the transferosomes provided an efficient nanosized carriers for enhanced permeation of boswellic acid into deeper layers of skin and could successfully exhibit its therapeutic effect.

On the usefulness of four in vitro methods in assessing the intraluminal performance of poorly soluble, ionisable compounds in the fasted state

A small-scale two-stage biphasic system, a small-scale two-stage dissolution-permeation system, the Erweka mini-paddle apparatus, and the BioGIT system were evaluated for their usefulness in assessing the intraluminal performance of two low solubility drugs in the fasted state, one with weakly acidic properties (tested in a salt form, diclofenac potassium) and one with weakly alkaline properties [ritonavir, tested as an amorphous solid dispersion (ASD) formulation].

In all in vitro methods, an immediate-release tablet and a powder formulation of diclofenac potassium were both rapidly dissolved in Level II biorelevant media simulating the conditions in the upper small intestine. Physiologically based biopharmaceutics (PBB) modelling for the tablet formulation resulted in a successful simulation of the average plasma profile in adults, whereas for the powder formulation modelling indicated that gastric emptying and transport through the intestinal epithelium limit the absorption rates.

Detailed information on the behaviour of the ritonavir ASD formulation under both simulated gastric and upper small intestinal conditions were crucial for understanding the luminal performance. PBB modelling showed that the dissolution and precipitation parameters, estimated from the Erweka mini-paddle apparatus data and the small-scale two-stage biphasic system data, respectively, were necessary to adequately simulate the average plasma profile after administration of the ritonavir ASD formulation. Simulation of the gastrointestinal transfer process from the stomach to the small intestine was necessary to evaluate the effects of hypochlorhydric conditions on the luminal performance of the ritonavir ASD formulation.

Based on this study, the selection of the appropriate in vitro method for evaluating the intraluminal performance of ionisable lipophilic drugs depends on the characteristics of the drug substance. The results suggest that for (salts of) acidic drugs (e.g., diclofenac potassium) it is only an issue of availability and ease of operation of the apparatus. For weakly alkaline substances (e.g., ritonavir), the results indicate that the dynamic dissolution process needs to be simulated, with the type of requested information (e.g., dissolution parameters, precipitation parameters, luminal concentrations) being key for selecting the most appropriate method. Regardless of the ionisation characteristics, early in the drug development process the use of small-scale systems may be inevitable, due to the limited quantities of drug substance available.

Considerations for the selection of co-formers in the preparation of co-amorphous formulations

Co-amorphous drug delivery systems are evolving as a credible alternative to amorphous solid dispersions technology. In Co-amorphous systems (CAMs), a drug is stabilized in amorphous form using small molecular weight compounds called as co-formers. A wide variety of small molecular weight co-formers have been leveraged in the preparation of CAMs. The stability and supersaturation potential of prepared co-amorphous phases largely depend on the type of co-former employed in the CAMs. However, the rationality behind the co-former selection in co-amorphous systems is poorly understood and scarcely compiled in the literature. There are various facets to the rational selection of co-former for CAMs. In this context, the present review compiles various factors affecting the co-former selection. The factors have been broadly classified under Thermodynamic, Kinetic and Pharmacokinetic-Pharmacologically relevant parameters. In particular, the importance of Glass transition, Miscibility, Liquid-Liquid phase separation (LLPS), Crystallization inhibition has been deliberated in detail.

Thermally Conductive Excipient Expands KinetiSol® Processing Capabilities

We report for the first time that incorporation of a thermally conductive excipient (TCE) modifies the thermal conductivity of the ternary drug-polymer-TCE compositions such that high-energy mixing can occur for prolonged periods at a selected steady-state temperature during the KinetiSol process. In this study, candurin, a TCE, is incorporated within a composition that is processed by high-energy mixing from the KinetiSol process to increase the thermal conductivity of the ternary composition. The improved thermal conductivity promotes heat transfer and enables the high-energy mixing applied during the KinetiSol process to be continued for prolonged time intervals at a selected steady-state temperature, instead of undergoing a continued increase in temperature when the TCE is not present in the composition. The addition of candurin does not impact the molecular structure and mixing of the drug and polymer in ASDs from solid-state NMR characterizations. Compositions with candurin achieved a steady-state processing temperature with + 5°C of the target temperature, and these compositions demonstrated the ability to mix for prolonged time periods while maintaining within this steady-state temperature range, thus enabling the formation of an ASD at a temperature that the drug does not chemically degrade. This study demonstrated that inclusion of the TCE modified the composition's thermal conductivity to efficiently dissipate heat to achieve a selected steady-state temperature during the KinetiSol process, thus providing prolonged mixing times at a lower temperature for dissolving the drug into the polymer to achieve an ASD without sacrificing product performance.

Development and characterization of bacterial nanocellulose loaded with Boswellia serrata extract containing nanoemulsions as natural dressing for skin diseases

The combination of the anti-inflammatory lipophilic Boswellia serrata extract with the natural hydropolymer bacterial nanocellulose (BNC) for the treatment of skin diseases is counteracted by their different hydro/lipophilicity. To overcome the hydrophilicity of the BNC, the water in its network was exchanged by single and double nanoemulsions. Incorporation of the Boswellia serrata extract in the nanoemulsions formed particles of about 115 to 150 nm with negative zeta potential and storage stability over 30 days at temperatures between 4 and 32 °C. Their loading into the BNC did not change the preferential characteristics of the nanocellulose like water absorption and retention, softness, and pressure stability in a relevant way. Loaded BNC could be sterilized by an electron-beam procedure. A biphasic drug release profile of lead compounds was observed by Franz cell diffusion test. The biocompatibility of the loaded BNC was confirmed ex ovo by a shell-less hen's egg test. Tape stripping experiments using porcine skin determined a dependency of the drug penetration into skin on the type of nanoemulsion, single vs. repeated applications and the incubation time. In conclusion, the hydrophilicity of BNC could be overcome using nanoemulsions which offers the possibility for the anti-inflammatory skin treatment with Boswellia serrata extract.

Harnessing the therapeutic potential of anticancer drugs through amorphous solid dispersions

The treatment of cancer is still a major challenge. But tremendous progress in anticancer drug discovery and development has occurred in the last few decades. However, this progress has resulted in few effective oncology products due to challenges associated with anticancer drug delivery. Oral administration is the most preferred route for anticancer drug delivery, but the majority of anticancer drugs currently in product pipelines and the majority of those that have been commercially approved have inherently poor water solubility, and this cannot be mitigated without compromising their potency and stability. The poor water solubility of anticancer drugs, in conjunction with other factors, leads to suboptimal pharmacokinetic performance. Thus, these drugs have limited efficacy and safety when administered orally. The amorphous solid dispersion (ASD) is a promising formulation technology that primarily enhances the aqueous solubility of poorly water-soluble drugs. In this review, we discuss the challenges associated with the oral administration of anticancer drugs and the use of ASD technology in alleviating these challenges. We emphasize the ability of ASDs to improve not only the pharmacokinetics of poorly water-soluble anticancer drugs, but also their efficacy and safety. The goal of this paper is to rationalize the application of ASD technology in the formulation of anticancer drugs, thereby creating superior oncology products that lead to improved therapeutic outcomes.

New derivatives of 11-keto-β-boswellic acid (KBA) induce apoptosis in breast and prostate cancers cells

A series of new 11-keto-β-boswellic acid were partially-synthesized by modifying the hydroxyl and carboxylic acid functional groups of ring A. The structures of the new analogs were confirmed by detailed spectral data analysis. Compounds 4, 5 and 9 exhibited potent anti-cancer results against two human tumor cancer cell lines having IC₅₀ value of MCF-7 (breast) and LNCaP (prostate): 123.6, 9.6 and 88.94 μM and 9.6, 44.12 and 12.03 μM, respectively. Additionally, a maximum nuclear fragmentation was observed for 4 (78.44%) in AKBA treated cells after 24 hr followed by 5 and 9 with (74.25 and 66.9% respectively). This study suggests that the presence of hydrazone functionality (4 and 9) has effectively improved the potency of AKBA. Interestingly, compound 5 with a lost carboxylic acid group of ring A showed comparable potent activity. Highly selective AKBA requires further modification to improve its bioavailability and solubility inside the cancer cells.

Ex-vivo intestinal absorption study of boswellic acid, cyclodextrin complexes and poloxamer solid dispersions using everted gut sac technique

Acetyl- Keto-β-boswellic acid (AKBA) is a pentacyclic triterpenic acid found in gum resin of Boswellia serrata. Even though it is shown to have anti-inflammatory activity, its bioavailability gets limited due to its poor aqueous solubility and permeability. The present study, hence, deals in enhancement of the intestinal absorption of AKBA from total boswellic acid fraction (TA fraction) using cyclodextrin (CD) and poloxamer solid dispersion (PXM SDs) formulations. Absorption studies were performed using the everted gut sac model prepared from rat jejunum. The glucose uptake assay was performed to show viability of gut sac tissue. The apparent permeability (P_app) value of AKBA from TA fraction was 1.08 ± 0.17 × 10^-6 which was found to be increased by 10-14 fold with CD complex and SD formulations. The intestinal absorption studies showed highest absorption of AKBA from HP-β-CD complex and PXM 407 SD as compared to that from TA fraction. From this study, it can be concluded that HP-β-CD and PXM 407 effectively enhanced intestinal absorption through improved solubility, highlighting their role as efficient drug delivery agents and bioavailability enhancers.

Homogeneity of amorphous solid dispersions - an example with KinetiSol®

KinetiSol^® is a high-shear, fusion-based technology capable of producing stable amorphous solid dispersions (ASDs) without the assistance of solvent. KinetiSol^® has proven successful with multiple challenging BCS class II and IV drugs, where drug properties like thermal instability or lack of appreciable solubility in volatile solvents make hot melt extrusion or spray drying unfeasible. However, there is a necessity to characterize the ASDs like those made by the KinetiSol^® process, in order to better understand whether KinetiSol^® is capable of homogeneously dispersing drug throughout a carrier in a short (<40 s) processing time. Our study utilized the high melting point, BCS class II drug, meloxicam, in order to evaluate the degree of homogeneity of 1, 5, and 10% w/w KinetiSol^®-processed samples. Powder blend homogeneity and content uniformity were evaluated, and all samples demonstrated a meloxicam concentration % relative standard deviation of ≤2.0%. SEM/EDS was utilized to map elemental distribution of the processed samples, which confirmed KinetiSol^®-processed materials were homogeneous at a 25 µm² area. Utilizing Raman spectroscopy, we were able to verify the amorphous content of the processed samples. Finally, we utilized ssNMR ¹H spin-lattice relaxation measurement to evaluate the molecular miscibility of meloxicam with the polymer at 1% w/w drug load, for the first time, and determined the processed sample was highly miscible at ∼200 nm scale. In conclusion, we determined the KinetiSol^® process is capable of producing ASDs that are homogeneously and molecularly well-dispersed drug-in-polymer at drug concentrations as low as 1% w/w.

Generation of a Weakly Acidic Amorphous Solid Dispersion of the Weak Base Ritonavir with Equivalent In Vitro and In Vivo Performance to Norvir Tablet

Ritonavir is an anti-viral compound that has also been employed extensively as a CYP3A4 and P-glycoprotein (Pgp) inhibitor to boost the pharmacokinetic performance of compounds that undergo first pass metabolism. For use in combination products, there is a desire to minimize the mass contribution of the ritonavir system to reduce patient pill burden in these combination products. In this study, KinetiSol® processing was utilized to produce an amorphous solid dispersion of ritonavir at two times the drug load of the commercially available form of ritonavir, and the composition was subsequently developed into a tablet dosage form. The amorphous intermediate was demonstrated to be amorphous by X-ray powder diffraction and ¹³C solid-state nuclear magnetic resonance and an intimately mixed single-phase system by modulated differential scanning calorimetry and ¹H T₁/¹H T_1ρ solid-state nuclear magnetic resonance relaxation. In vitro transmembrane flux analysis showed similar permeation rates for the KinetiSol-made tablet and the reference tablet dosage form, Norvir®. In vivo pharmacokinetic comparison between the two dosage forms resulted in equivalent exposure with approximately 20% Cmax reduction for the KinetiSol tablet. These performance gains were realized with a concurrent reduction in dosage form mass of 45%.

Expanding the Application and Formulation Space of Amorphous Solid Dispersions with KinetiSol®: a Review

Due to the high number of poorly soluble drugs in the development pipeline, novel processes for delivery of these challenging molecules are increasingly in demand. One such emerging method is KinetiSol, which utilizes high shear to produce amorphous solid dispersions. The process has been shown to be amenable to difficult to process active pharmaceutical ingredients with high melting points, poor organic solubility, or sensitivity to heat degradation. Additionally, the process enables classes of polymers not conventionally processable due to their high molecular weight and/or poor organic solubility. Beyond these advantages, the KinetiSol process shows promise with other applications, such as the production of amorphous mucoadhesive dispersions for delivery of compounds that would also benefit from permeability enhancement.

Advances in Polymer Design for Enhancing Oral Drug Solubility and Delivery

Synthetic polymers have enabled amorphous solid dispersions (ASDs) to emerge as an oral delivery strategy for overcoming poor drug solubility in aqueous environments. Modern ASD products noninvasively treat a range of chronic diseases (for example, hepatitis C, cystic fibrosis, and HIV). In such formulations, polymeric carriers generate and maintain drug supersaturation upon dissolution, increasing the apparent drug solubility to enhance gastrointestinal barrier absorption and oral bioavailability. In this Review, we outline several approaches in designing polymeric excipients to drive interactions with active pharmaceutical ingredients (APIs) in spray-dried ASDs, highlighting polymer-drug formulation guidelines from industrial and academic perspectives. Special attention is given to new commercial and specialized polymer design strategies that can solubilize highly hydrophobic APIs and suppress the propensity for rapid drug recrystallization. These molecularly customized excipients and hierarchical excipient assemblies are promising toward informing early-stage drug-discovery development and reformulating existing API candidates into potentially lifesaving oral medicines for our growing global population.