Hydrolysis of Cellulose Acetate Phthalate and Hydroxypropyl Methylcellulose Phthalate in Amorphous Solid Dispersions.

The preparation of amorphous solid dispersions (ASDs) represents a promising strategy for addressing the solubility limitations of poorly soluble drugs, facilitating enhanced oral absorption. Acidic polymers such as cellulose acetate phthalate (CAP) and hydroxypropyl methylcellulose phthalate (HPMCP) have emerged as effective carriers for ASDs. Although the hydrolytic degradation of these polymers has been documented, its impact on the stability of ASDs has not been systematically investigated. This research aimed to explore the potential hydrolysis of CAP and HPMCP and how it influences the stability of ASDs containing ketoconazole (KTZ), at drug loadings of 10 % and 50 %. Our study utilized thermal analysis, infrared spectroscopy, and evaluations of physical and chemical stability. The results revealed that although KTZ remained physically stable in all ASDs over 60 days under various stability conditions, the emergence of crystalline phthalic acid (PA), a byproduct of polymer hydrolysis, was observed at elevated temperatures and relative humidity levels. The acidic microenvironment fostered by the release of PA further catalyzed drug chemical degradation. This study underscores the susceptibility of CAP and HPMCP to hydrolytic degradation, highlighting the inherent risk of PA-induced drug degradation, particularly for acid-labile compounds. These insights into the understanding of polymer hydrolysis in ASDs pave the way for the development of targeted approaches to safeguard drug stability and optimize pharmaceutical formulations for enhanced bioavailability, efficacy, and safety.

Solvent-Casted Films to Assist Polymer Selection for Amorphous Solid Dispersions During Preclinical Studies: In-vitro and In-vivo Exploration.

PURPOSE: The use of two solvent-casted film methods to select optimal polymer compositions for amorphous solid dispersions prepared to support preclinical pharmacokinetic and toxicology studies is described. METHODS: Evaporation of solvent from cover slips by using nitrogen flow, and solvent removal from vials by using rotary evaporation were employed. The films prepared on cover slips were evaluated under the microscope to determine crystallinity. The methods were validated by scaling up corresponding SDDs, evaluating SDD's dissolution, and comparing those results to the dissolution of drug-polymer films. Subsequently, SDD suspensions were prepared and dosed orally to rats to determine pharmacokinetic parameters. This was done by using three compounds from our pipeline and evaluating multiple polymers. RESULTS: The dissolution of generated films showed good agreement with the dissolution of spray dried dispersions when the films were fully amorphous (Compound A and B). In contrast, there was disagreement between film and SDD dissolution when the films had crystallized (Compound C). The in vivo exposure results indicated that the polymer choice based on the film screening methods would have been accurate for drug-polymer films that were amorphous (Compound A and B). Two additional case studies (Compound D and E) are presented, showing good agreement between in vivo and in vitro results. CONCLUSION: This study established the ability of two film casting screening methods to predict the in vitro and in vivo performance of corresponding SDDs, provided that the films are fully amorphous.

Utilization of In Vitro, In Vivo and In Silico Tools to Evaluate the pH-Dependent Absorption of a BCS Class II Compound and Identify a pH-Effect Mitigating Strategy.

PURPOSE: To describe a stepwise approach to evaluate the pH effect for a weakly basic drug by in vitro, in vivo and in silico techniques and identify a viable mitigation strategy that addresses the risk. METHODS: Clinical studies included assessment of the pH effect with famotidine. In vitro dissolution was evaluated in various biorelevant media and in a pH-shift test. PK studies in dogs were conducted under pentagastrin or famotidine pre-treatment and GastroPlus was employed to model human and dog PK data and simulate the performance in human. RESULTS: Clinical data indicated considerable pH dependent absorption of the drug when dosed in the presence of H2-antagonists. In vitro dissolution and in vivo dog data confirmed that the observed pH effect was due to reduced dissolution rate and lower solubility at increased gastric and intestinal pH. A salt form was identified to overcome the effect by providing fast dissolution and prolonged supersaturation. GastroPlus simulations predicted a mitigation of the pH effect by the salt. CONCLUSIONS: The drug exhibited a strong pH-effect in humans. The in vitro, in vivo and modeling approach provides a systematic workflow to evaluate the risk of a new drug and identify a strategy able to mitigate the risk.

Discovery of ((4-(5-(Cyclopropylcarbamoyl)-2-methylphenylamino)-5-methylpyrrolo[1,2-f][1,2,4]triazine-6-carbonyl)(propyl)carbamoyloxy)methyl-2-(4-(phosphonooxy)phenyl)acetate (BMS-751324), a Clinical Prodrug of p38α MAP Kinase Inhibitor.

In search for prodrugs to address the issue of pH-dependent solubility and exposure associated with 1 (BMS-582949), a previously disclosed phase II clinical p38α MAP kinase inhibitor, a structurally novel clinical prodrug, 2 (BMS-751324), featuring a carbamoylmethylene linked promoiety containing hydroxyphenyl acetic acid (HPA) derived ester and phosphate functionalities, was identified. Prodrug 2 was not only stable but also water-soluble under both acidic and neutral conditions. It was effectively bioconverted into parent drug 1 in vivo by alkaline phosphatase and esterase in a stepwise manner, providing higher exposure of 1 compared to its direct administration, especially within higher dose ranges. In a rat LPS-induced TNFα pharmacodynamic model and a rat adjuvant arthritis model, 2 demonstrated similar efficacy to 1. Most importantly, it was shown in clinical studies that prodrug 2 was indeed effective in addressing the pH-dependent absorption issue associated with 1.

Preclinical pharmacokinetics and in vitro metabolism of BMS-605339: a novel HCV NS3 protease inhibitor.

BMS-605339 is a potent HCV NS3 protease inhibitor that suppresses hepatitis C virus replication and was under investigation as an oral agent for the treatment of this disease. In vitro and in vivo studies were conducted in mouse, rat, dog, and monkey to characterize the pharmacokinetics and metabolism of this compound. BMS-605339 was predicted to be a moderate clearance compound in the human, based on human microsomal and hepatocyte data. Nearly all metabolism of BMS-605339 was oxidative; CYP3A4 is likely to play a key role in the metabolic clearance of this compound. Moderate to high Caco-2 permeability was observed for this compound, with the potential for P-glycoprotein involvement. The oral bioavailability of BMS-605339 was variable and dose dependent, suggesting low absorption, possibly because of transporter involvement. BMS-605339 possesses low intrinsic aqueous solubility and, in both rat and dog, administration of an aqueous suspension suggested that BMS-605339 absorption is likely solubility limited. Liver exposure of BMS-605339 was consistently higher than plasma exposure in all species tested (mouse, rat, and dog), indicating the potential for active uptake into hepatocytes. The overall preclinical pharmacokinetic profile supported the selection and development of BMS-605339 as a clinical candidate.

Discovery and early clinical evaluation of BMS-605339, a potent and orally efficacious tripeptidic acylsulfonamide NS3 protease inhibitor for the treatment of hepatitis C virus infection.

The discovery of BMS-605339 (35), a tripeptidic inhibitor of the NS3/4A enzyme, is described. This compound incorporates a cyclopropylacylsulfonamide moiety that was designed to improve the potency of carboxylic acid prototypes through the introduction of favorable nonbonding interactions within the S1' site of the protease. The identification of 35 was enabled through the optimization and balance of critical properties including potency and pharmacokinetics (PK). This was achieved through modulation of the P2* subsite of the inhibitor which identified the isoquinoline ring system as a key template for improving PK properties with further optimization achieved through functionalization. A methoxy moiety at the C6 position of this isoquinoline ring system proved to be optimal with respect to potency and PK, thus providing the clinical compound 35 which demonstrated antiviral activity in HCV-infected patients.

Assessing the risk of pH-dependent absorption for new molecular entities: a novel in vitro dissolution test, physicochemical analysis, and risk assessment strategy.

Weak base therapeutic agents can show reduced absorption or large pharmacokinetic variability when coadministered with pH-modifying agents, or in achlorhydria disease states, due to reduced dissolution rate and/or solubility at high gastric pH. This is often referred to as pH-effect. The goal of this study was to understand why some drugs exhibit a stronger pH-effect than others. To study this, an API-sparing, two-stage, in vitro microdissolution test was developed to generate drug dissolution, supersaturation, and precipitation kinetic data under conditions that mimic the dynamic pH changes in the gastrointestinal tract. In vitro dissolution was assessed for a chemically diverse set of compounds under high pH and low pH, analogous to elevated and normal gastric pH conditions observed in pH-modifier cotreated and untreated subjects, respectively. Represented as a ratio between the conditions, the in vitro pH-effect correlated linearly with clinical pH-effect based on the Cmax ratio and in a non-linear relationship based on AUC ratio. Additionally, several in silico approaches that use the in vitro dissolution data were found to be reasonably predictive of the clinical pH-effect. To explore the hypothesis that physicochemical properties are predictors of clinical pH-effect, statistical correlation analyses were conducted using linear sequential feature selection and partial least-squares regression. Physicochemical parameters did not show statistically significant linear correlations to clinical pH-effect for this data set, which highlights the complexity and poorly understood nature of the interplay between parameters. Finally, a strategy is proposed for implementation early in clinical development, to systematically assess the risk of clinical pH-effect for new molecular entities that integrates physicochemical analysis and in vitro, in vivo and in silico methods.

Synthesis and evaluation of carbamoylmethylene linked prodrugs of BMS-582949, a clinical p38α inhibitor.

A series of carbamoylmethylene linked prodrugs of 1 (BMS-582949), a clinical p38α inhibitor, were synthesized and evaluated. Though the phosphoryloxymethylene carbamates (3, 4, and 5) and α-aminoacyloxymethylene carbamates (22, 23, and 26) were found unstable at neutral pH values, fumaric acid derived acyloxymethylene carbamates (2, 28, and 31) were highly stable under both acidic and neutral conditions. Prodrugs 2 and 31 were also highly soluble at both acidic and neutral pH values. At a solution dose of 14.2mpk (equivalent to 10mpk of 1), 2 gave essentially the same exposure of 1 compared to dosing 10mpk of 1 itself. At a suspension dose of 142mpk (equivalent to 100mpk of 1), 2 demonstrated that it could overcome the solubility issue associated with 1 and provide a much higher exposure of 1. To our knowledge, the unique type of prodrugs like 2, 28, and 31 was not reported in the past and could represent a novel prodrug approach for secondary amides, a class of molecules frequently identified as drug candidates.

Utilization of in vitro Caco-2 permeability and liver microsomal half-life screens in discovering BMS-488043, a novel HIV-1 attachment inhibitor with improved pharmacokinetic properties.

Optimizing pharmacokinetic properties to improve oral exposure is a common theme in modern drug discovery. In the present work, in vitro Caco-2 permeability and microsomal half-life screens were utilized in an effort to guide the structure-activity relationship in order to improve the pharmacokinetic properties of novel HIV-1 attachment inhibitors. The relevance of the in vitro screens to in vivo pharmacokinetic properties was first demonstrated with a number of program compounds at the early stage of lead optimization. The Caco-2 permeability, tested at 200 microM, was quantitatively predictive of in vivo oral absorption, with complete absorption occurring at a Caco-2 permeability of 100 nm/s or higher. The liver microsomal half-life screen, conducted at 1 microM substrate concentration, can readily differentiate low-, intermediate-, and high-clearance compounds in rats, with a nearly 1:1 correlation in 12 out of 13 program compounds tested. Among the >100 compounds evaluated, BMS-488043 emerged as a lead, exhibiting a Caco-2 permeability of 178 nm/s and a microsomal half-life predictive of a low clearance (4 mL/min/kg) in humans. These in vitro characteristics translated well to the in vivo setting. The oral bioavailability of BMS-488043 in rats, dogs, and monkeys was 90%, 57%, and 60%, respectively. The clearance was low in all three species tested, with a terminal half-life ranging from 2.4 to 4.7 h. Furthermore, the oral exposure of BMS-488043 was significantly improved (6- to 12-fold in rats and monkeys) compared to the prototype compound BMS-378806 that had a suboptimal Caco-2 permeability (51 nm/s) and microsomal half-life. More importantly, the improvements in preclinical pharmacokinetics translated well to humans, leading to a >15-fold increase in the human oral exposure of BMS-488043 than BMS-378806 and enabling a clinical proof-of-concept for this novel class of anti-HIV agents. The current studies demonstrated the valuable role of in vitro ADME screens in improving oral pharmacokinetics at the lead optimization stage.

Discovery pharmaceutics--challenges and opportunities.

Most pharmaceutical companies are now evaluating compounds for druglike properties early in the discovery process. The data generated at these early stages allow upfront identification of potential development challenges and thus selection of the best candidates for lead nomination. Most often, lead nomination candidates are selected based on pharmacological and toxicological data. However, many drugs in development suffer from poor biopharmaceutical properties due to suboptimal physiochemical parameters. The poor biopharmaceutical properties often lead to extended timelines and a higher cost of developing the compounds. To avoid these problems and choose the best compounds from a biopharmaceutical perspective, physicochemical parameters such as solubility, lipophilicity, and stability need to be evaluated as early as possible. Furthermore, the preformulation approaches used to evaluate the compounds for their pharmacokinetic and toxicological properties need to be optimized. This minireview summarizes some of the parameters and approaches that can be used to evaluate compounds in the early stages of drug discovery.