General Biological Technologies
The EPDD service has well-established capabilities for developing cell lines and assays via transient or stable cell transfections and for adapting assays for use in HTS.
Assay endpoints can include but are not limited to receptor binding in 96-well format, receptor activation via calcium mobilization, β-arrestin recruitment, GTP-γ-S binding, cAMP generation, membrane potential, high-content assays for receptor internalization or nuclear translocation, and medium throughput electrophysiology. RTI also has excellent behavioral pharmacology capabilities.
The identification of hit or lead compounds for a macromolecular target is the first step toward preclinical drug discovery. The chosen discovery path is highly dependent on the number of previously identified leads, the types of leads available (peptides or small molecules), or both.
A library of compounds can be screened at the target of interest to identify hits. The EPDD has the ability to screen compound libraries in 96- and 384-well based assays. It currently has a 25,000-compound, hand-selected, high-diversity library that can be screened through all new targets.
Computational methods can also be used. These include computing conformational libraries and physiochemical properties for several known ligands in “bioactive” conformations. Virtual screening of commercial or proprietary libraries can be conducted on >16 million ligands. When the target receptor/protein structure is known, both ligandbased (3D-pharmacophore) and structure-based design approaches may be jointly applied.
In vitro ADMET Battery
Once suitable leads are discovered, EDPP can conduct iterative studies to evaluate drug-like properties using a battery of in vitro tests. These typically include determination of solubility, stability in biological fluids, gut and blood–brain barrier (BBB) permeability, hepatic toxicity, hepatic metabolism, and hERG inhibition.
This battery typically leads to the identification of compounds with favorable drug-like properties. Upon identification of suitable advanced leads, in vivo assessment of pharmacokinetics is undertaken. Finally, we have developed novel computational approaches to structure-based metabolism and toxicity prediction that complement confirmatory in vitro probes.
In Vivo Pharmacokinetics
Snapshot model. A compound’s ability to cross the BBB and have an appropriate elimination half-life (t1/2) is an important drug-candidate selection criterion. Our strategy employs a first-pass “snapshot” PK analysis in a limited number of animals to broadly determine BBB penetration and t1/2 in plasma and brain.
Detailed PK study. The concentration over time of the test substance in blood (or serum, plasma, or brain) and select tissues is evaluated using non-compartmental methods. Depending on the stage of development, intravenous or oral administration is used.