Physicochemical parameters (solubility and lipophilicity) are used as first indicators of the “drug-likeness” of the compound, with respect to absorption from the intestine. Information of these properties is also valuable when planning optimum conditions for other in vitro ADME assays.

Evaluation of binding and unbound fraction of the drug in various matrices (i.e. plasma, brain, red blood cells) is in a key role when it comes to distribution of the compound across biological membranes and its availability for metabolic processes. These are important parameters when scaling the processes between various species and predicting in vivo processes based on in vitro assays such as hepatic clearance or CYP-inhibition potential.

Our services cover evaluation of physicochemical parameters in buffers or in biorelevant media, as well as evaluation of unbound fraction in biological matrices essential for ADME properties.

Lipophilicity (logD/P)

Lipophilicity (logD or logP) is measured using a “shake-flask” –method. The study compound is incubated in a two-phase system under shaking, and samples collected from both phases after equilibration are analysed with LC/PDA/MS.

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Solubility

The solubility of a study compound is determined using either the traditional “shake-flask” –method (thermodynamic solubility) or by spiking DMSO-stock solution into buffer-system (“kinetic” solubility) to minimise the consumption of the study compound. The samples will be filtrated and analysed by LC/PDA/MS.

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Plasma Protein Binding

Degree of binding of a study compound in plasma is elucidated using rapid equilbrium dialysis (RED) or ultrafiltration, followed by analysis of the samples by LC/MS/MS. Also TRANSIL high-sensitivity binding –assay can be used to measure binding, if the binding is too high to be measured using the traditional methods or if the compound has high non-specific binding (e.g. low recovery) in traditional assays.

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Red Blood Cell Binding

The study compound is incubated in fresh whole blood and plasma. The blood is centrifuged to separate plasma and the ratio of the study compound observed in plasma in comparison to reference plasma sample will be used to calculate red blood cell binding (and blood/plasma partitioning ratio).

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Tissue Binding

Degree of binding of study compound in tissues is elucidated using rapid equilibrium dialysis (RED) or ultrafiltration in tissue homogenate, followed by analysis of the samples by LC/MS/MS.

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Microsome / Hepatocyte Binding

Degree of binding of the study compound in microsomes or hepatocytes is elucidated using rapid equilibrium dialysis (RED) or ultrafiltration, followed by analysis of the samples by LC/MS/MS.

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