Diagnosing solubility limitations – the example of hydrate formation

Solubility is regarded as one of the key challenges in many drug discovery projects. Thus, it is essential to support lead finding and optimization efforts with appropriate solubility data. In silico solubility prediction remains challenging and therefore a screening assay is used as a first filter, followed by selected follow-up assays to reveal what causes the low solubility of a specific compound or chemotype. Results from diagnosing the underlying reason for solubility limitation are discussed. As lipophilicity and crystal lattice forces are regarded as main contributors to limiting solubility, changes in solid state are important to be recognized. Solubility limitation by various factors will be presented and the impact of the solid-state is exemplified by compounds that are able to form hydrates

Diagnosing solubility limitations – the example of hydrate formation (revised)

Solubility is regarded as one of the key challenges in many drug discovery projects. Thus, it is essential to support lead finding and optimization efforts with appropriate solubility data. In silico solubility prediction remains challenging and therefore a screening assay is used as a first filter, followed by selected follow-up assays to reveal what causes the low solubility of a specific compound or chemotype. Results from diagnosing the underlying reason for solubility limitation are discussed. As lipophilicity and crystal lattice forces are regarded as main contributors to limiting solubility, changes in solid state are important to be recognized. Solubility limitation by various factors will be presented and the impact of the solid-state is exemplified by compounds that are able to form hydrates

Modulation of oral bioavailability and metabolism for closely related cyclic hexapeptides

Recently, a variety of studies concerned with the permeability and oral bioavailability of cyclic peptides have been reported. In particular, strategies aiming at modifying peptides to maintain or to enhance solubility while enabling permeability constitute a significant challenge, but are of high interest to ensure a smooth drug discovery process. Current methodologies include N-methylation, matching of hydrogen bonding acceptors and donors across the macrocycle, and additional masking of polarity. In this study, we investigate further the pivotal effects of shielding on permeability and studied the metabolism of the corresponding peptides in more detail by comparing peptide concentrations in the portal versus the jugular vein in rats. Interestingly, minor changes in one particular side chain impact permeability and also liver metabolism

Design and Development of a Cyclic Decapeptide Scaffold with Suitable Properties for Bioavailability and Oral Exposure

Permeability and oral bioavailability of macrocyclic peptides still represents a difficult challenge in drug discovery. Despite their recognised potential as therapeutics, their use is still restricted to extra-cellular targets and i.v. administration. Indeed, macrocyclic peptides generally suffer from limited proteolytic stability, high clearance and poor membrane permeability leading to the absence of systemic exposure after oral administration. In order to overcome these limitations, we started to investigate the development of a general cyclic decapeptide scaffold that possesses ideal features for cell permeability and oral exposure. Based on a hairpin structure, the scaffold design aimed to reduce the overall polarity of the compound thereby limiting the energetic cost of NH desolvation and the entropy penalty during cell penetration. The results of this study demonstrate the importance of rigidity for the -turn design regarding clearance. In order to stabilize the scaffold in the desired β-hairpin conformation to favour permeability, the introduction of D-proline at the i+1 turn position also proved to be beneficial in limiting clearance. As a result, cyclopeptide decamers with unprecedented high values for oral bioavailability and exposure are reported herein. NMR conformation and dynamic analysis confirmed for selected examples the rigidity of the scaffold and the presence of trans-annular hydrogen bonds in polar and apolar environments. Furthermore, we showed that the excellent bioavalability value obtained for one compound was supported by a favourable entropy for the transition from a polar to an apolar environment

An orally bioavailable Syk inhibitor with activity in a rat PK/PD model

Design and optimization of benzo and pyridothiazoles and isothiazoles are reported leading to the discovery of the potent, orally bioavailable Syk inhibitor 5, which was found to be active in a rat PK/PD model. Compound 5 showed acceptable overall kinase selectivity. But in addition to Syk it also inhibited Aurora kinase in enzymatic and cellular settings leading to findings in the micronucleus assay. As a consequence, compound 5 was not further pursued

Pyridyl-Ala modified cyclic hexapeptides: in-vitro and in-vivo profiling for oral bioavailability

We and others have been aiming at modifications to maintain or to enhance solubility while enabling permeability for cyclic hexapeptides. Especially, the 2-pyridyl-Ala modification was investigated, since in this case, the pyridyl-nitrogen is able to form an H-bond to the NH of the same residue. The hypothesis of a backbone side-chain interaction was demonstrated by NMR experiments, and further results obtained on a variety of pyridyl-Ala derivatives, studied systematically in the context of permeability, are presented in this contribution. Thus, this study sheds some more light on the pyridyl-Ala modification, which had been reported earlier. In addition to the in-vitro profiling, the extent of oral bioavailability was assessed in rats. In principle, the pyridyl-Ala residue can be considered as an amino acid supporting oral uptake

On the importance of metabolic stability to achieve high oral exposures for cyclic peptides

Following up on a previous publication in which we reported a high liver first pass effect in rats for the cyclic peptide (1) [Ala-Leu-NMe-D-Leu-NMe-Leu-Leu-D-Pro], we decided to investigate the type of metabolites formed and to suggest solutions to this problem. As a result of a bile duct cannulation study in rats and subsequent derivatization of this peptide by an isolated Cyp-enzyme, several hydroxylated variants were identified. Cyclopropyl-Ala (Cpa) residues as surrogates for Leu alleviated metabolism at these particular side chains. Significant progress was achieved, when in addition the D-Pro residue was exchanged by 4,4 difluoro-D-Pro (DiF-D-Pro). Albeit the Ala was kept constant in this process, in the corresponding in-vivo studies in rats, peptide (6) [Ala-Cpa-NMe-D-Cpa-NMe-Cpa-Cpa-4,4 difluro-D-Pro] exhibited M exposures at 3mg/kg and an absolute oral bioavailability of > 90%. Thus, we conclude the Cpa- and DiF-D-Pro residues are metabolically stable isosteres for Leu, and D-Pro respectively

Discovery of a Dihydroisoquinolinone Derivative (NVP-CGM097): A Highly Potent and Selective MDM2 Inhibitor Undergoing Phase 1 Clinical Trials in p53wt Tumors

As a result of our efforts to discover novel p53:MDM2 protein–protein interaction inhibitors useful for treating cancer, the potent and selective MDM2 inhibitor NVP-CGM097 (<b>1</b>) with an excellent in vivo profile was selected as a clinical candidate and is currently in phase 1 clinical development. This article provides an overview of the discovery of this new clinical p53:MDM2 inhibitor. The following aspects are addressed: mechanism of action, scientific rationale, binding mode, medicinal chemistry, pharmacokinetic and pharmacodynamic properties, and in vivo pharmacology/toxicology in preclinical species

Discovery of BGJ398 (3-(2,6-Dichloro-3,5-dimethoxy-phenyl)-1-{6-[4-(4-ethyl-piperazin-1-yl)-phenylamino]-pyrimidin-4-yl}-1-methyl-urea), A Potent and Selective Inhibitor of the Fibroblast Growth Factor Receptor Family of Receptor Tyrosine Kinase

A novel series of aryl pyrimidin-4-yl ureas has been optimized to afford potent and selective inhibitors of the fibroblast growth factor receptor tyrosine kinases 1, 2 and 3, by rationally designing the substitution pattern of the aryl ring. On the basis of its in vitro profile, compound 2h was selected for in vivo evaluation and showed significant antitumor activity in RT112 bladder cancer xenografts models overexpressing wild-type FGFR3. These results support the potential therapeutic use of 2h as a new anticancer agent

Current approaches for predicting human PK for small molecule development candidates: Findings from the IQ Human PK Prediction Working Group Survey

Accurate prediction of human clearance (CL) and volume of distribution at steady state (Vd,ss) for small molecule drug candidates is an essential component of assessing likely efficacious dose and clinical safety margins. In 2021, the IQ Consortium Human PK Prediction Working Group undertook a survey of IQ member companies to understand the current PK prediction methods being used to estimate these parameters across the pharmaceutical industry. The survey revealed a heterogeneity in approaches being used across the industry (e.g., use of allometric approaches, differing incorporation of binding terms, and inconsistent use of empirical correction factors for in vitro-in vivo extrapolation, IVIVE), which could lead to different PK predictions with the same input data. Member companies expressed an interest in improving human PK predictions by identifying the most appropriate compound-class specific methods, as determined by physiochemical properties and knowledge of CL pathways. Furthermore, there was consensus that increased understanding of the uncertainty inherent to the compound class-dependent prediction would be invaluable in aiding communication of human PK and dose uncertainty at the time of candidate nomination for development. The human PK Prediction Working Group is utilizing these survey findings to help interrogate clinical IV datasets from across the IQ consortium member companies to understand PK prediction accuracy and uncertainty from preclinical datasets