A variety of in vitro assays can be conducted to improve the ADME (Absorption, Distribution, Metabolism,Excretion) profile of a lead compound or drug candidate. Nextar offers absorption studies performed on artificial membranes for the prediction of intestinal absorption, protein binding studies of compounds and their stability in plasma or serum, in vitro metabolism assays using liver microsomes to characterize the metabolic stability and metabolic fate of our costumers' compounds. The loss of the parent compound is monitored as well as the formation of metabolites for the prediction of bioavailability, clearance, half -life and identifying the nature of metabolites applying LC-MS/MS techniques. Specific Cytochrome P450 profile screening is performed using single human recombinant CYP isozymes (Supersomes TM). Pharmacokinetic analysis of bioanalytical data from preclinical or clinical studies is also carried out using validated WinNinLin ® software.
The following specific services are provided:
Permeability studies of drugs through PAMPA membranes
Determination of the intestinal permeability is a key parameter for the selection of compounds for drug discovery. The parallel artificial membrane permeability assay (PAMPA) represents a fast screening in vitro tool which allows the prediction of in vivo drug permeability by measuring passive transport properties of compounds through PAMPA membranes.
The degree of binding of a compound to plasma or serum proteins can provide important information about its efficacy and its potential for drug-drug interactions. Nextar determines the plasma protein binding (PPB) for various species (rat, rabbit, dog, pig, monkey, human) by ultrafiltration or equilibrium dialysis based on compound characteristics.
Drug stability in plasma or serum
The stability of small molecules and peptides in plasma is an important parameter which can strongly influence the in vivo efficacy of a test compound. Drug candidates are exposed in plasma to enzymatic processes (proteinases, esterases), they can undergo intramolecular rearrangement or bind irreversibly (covalently) to proteins. Thus the investigation of plasma stability should be performed early in drug discovery. Nextar performs quick assays for stability of test compounds in animal and human plasma or serum.
In-vitro metabolic stability
In order to identify whether a new compound is metabolized by cytochrome P-450 enzymes, the metabolic stability of the drug is tested using rat, rabbit, pig, dog, monkey and human liver microsomes. Nextar conducts in vitro tests for phase I or phase II metabolites (glucoronidation). Calculation of in-vitro half-life and intrinsic clearance is performed.
In- vitro cross species comparison of drug metabolic profile
The purpose of this assay offered by Nextar is to define the most appropriate species for toxicological studies. According to ICH guidance the animal species which produce all human in-vitro metabolites is the most appropriate for assessment of potential human risk in toxicology studies. The analysis generates proposed structure of putative metabolites, and comparison of the metabolites obtained across species (rat, rabbit, dog, pig, monkey, human).
Cytochrome P450 profiling with human SupersomesTM
CYP450 profiling of new chemical entities is an important parameter in the lead optimization process because it provides information on the involvement of the different human hepatic CYP isoenzymes in the metabolism of a test compound. By using single human CYP recombinant isozymes (SupersomesTM, BD Gentest, USA) potential isoenzyme related differences in the rate of metabolism of the test compound can be detected. This assay offered by Nextar gives initial evaluation of the specific CYP's involved in the metabolism of a new drug candidate. The available CYPs are:1A1, 1A2, 1B1, 1E1, 2A6, 2B6, 2C8, 2C9, 3A4, 4A11, 2C19, 2D6.
Nextar performs data analysis of bioanalytical results from pharmacokinetic and toxicokinetic studies using validated WinNonLin® software. The analysis may be carried out by non-compartmental or compartmental modeling and generates PK parameters including area under the curve (AUC), half-life (t1/2), clearance (CL), volume of distribution (Vss), etc. Allometric scaling of PK parameters from animal studies to human is also provided.