Following the selection of a clinical drug candidate, AMRI’s DMPK experts will help you successfully initiate and complete your preclinical investigational new drug (IND)-enabling program with our support services, which include fully validated IND-enabling study designs with appropriate positive and negative controls. We conduct these studies under Good Documentation Practices and provide full submission-ready reports for your IND application.
In Vitro DMPK Studies
We offer several types of in vitro DMPK studies related to drug-drug interactions (DDI) and metabolism for inclusion in IND submissions. Our study offerings, which often lend insight into the design of future clinical studies, include:
Cytochrome P-450 (CYP) Inhibition
Inhibition of cytochrome P-450 (CYP)-mediated metabolism is a common form of metabolism-based drug-drug interactions. The drug candidate (perpetrator) may inhibit a particular CYP isoform, and the inhibition may reduce the metabolism of co-medications (victims) cleared by the same isoform. This will result in increased exposure to the co-medications, possibly to toxic levels.
The test drug is co-incubated with CYP-selective probe substrates and human liver microsomes, and inhibition of the CYPs is assessed by measuring formation of metabolites of probe substrates by LC/MS/MS analysis. Inhibition is expressed as an IC50 value for CYPs 1A2, 2B6, 2C8, 2C9, 2C19, 2D6 and 3A4.
Another form of DDI, CYP induction occurs when a test drug increases the expression of CYP enzymes in the liver. This can result in increased metabolism of co-medications, resulting in decreased exposure and possibly loss of efficacy.
Human hepatocyte cultures from three separate donors are exposed to the test drug for two days, and after washing out the test drug, CYP-selective probe substrates are incubated with the cells. Determination of increased CYP activities is assessed by measuring formation of metabolites of probe CYP substrates by LC/MS/MS analysis. Induction is expressed as a fold induction value for CYPs 1A2, 2B6 and 3A4.
CYP Reaction Phenotyping
CYP reaction phenotyping involves the identification of CYP isoforms responsible for the metabolism of a drug candidate, allowing predictions of co-medications (perpetrators) that might alter the metabolism of the drug candidate (victim) by inhibition or induction of a particular CYP isoform.
Two enzyme systems are used: individual recombinant human CYP (rhCYP) enzymes and human liver microsomes. The test drug is incubated with each rhCYP isoform, and the ability of the CYPs to metabolize the test drug is analyzed by loss of parent drug and formation of metabolites. Using human liver microsomes, the test drug is incubated in the absence and presence of isoform-specific chemical inhibitors, which allows identification of CYP isoforms that metabolize the test drug, as determined by loss of parent drug and formation of metabolites. The CYP isoforms evaluated are CYPs 1A2, 2B6, 2C8, 2C9, 2C19, 2D6 and 3A4.
Comparison of Metabolic Pathways Between Humans and Laboratory Animal Species
In vitro metabolite profiling of a test drug using hepatocyte suspensions from human, rat (and/or mouse), dog and monkey is frequently included in IND submissions. This information may be used to guide the selection of the appropriate rodent and non-rodent species in toxicology studies by determining which laboratory animal species will be exposed to the same set of metabolites as humans will be in clinical studies. The test drug is incubated with human and animal hepatocytes, and incubations are submitted for ion trap LC/MS/MS analysis to provide each species’ metabolite profile.