SafetySuite Testing Sequence

Metabolite Identification^1,2,3
In vitro incubation samples (microsomes,S9 or hepatocytes)
In vivo samples (plasma, bile, urine, etc.)

CYP Phenotyping^1,3
CYP-specific chemical inhibitors incubated with human liver microsomes
Human recombinant CYP enzymes

CYP Inhibition^1,3
Selective probe substrates incubated with human liver microsomes

CYP Induction^1,3
Freshly isolated or cryopreserved cultured human hepatocytes

¹ FDA Draft Guidance, Feb. 2012 – Guidance for Industry Drug Interaction Studies-Study Design Data Analysis, and Implications for Dosing and Labeling Recommendations
² FDA Guidance, Feb. 2008 – Guidance for Industry Safety Testing of Drug Metabolites
³ EMA Guidelines, April 2010 – Guideline on the Investigation of Drug Interactions (Draft)

Efflux Transporters^1,2,3
Bidirectional transport using polarized cell monolayers
Uptake into inside-out vesicles from BSEP-overexpressing cells

Uptake Transporters^1,2,3
Bidirectional transport using polarized cell monolayers
Uptake in transporter-overexpressing cells vs. control

¹ FDA Draft Guidance, Feb. 2012-Guidance for Industry Drug Interaction Studies-Study Design Data Analysis, and Implications for Dosing and Labeling Recommendations
² The International Transporter Consortium  White Paper, March 2010. Membrane Transporters in Drug Development. Nature Rev Drug Disc 2010 March; 9(3):215-236
³ EMA Guidelines, April 2010 – Guideline on the Investigation of Drug Interactions (Draft)

The 2006 FDA draft guidance only states that P-gp is important to consider.  Why should I assess interactions with other transporters?
In February 2012, the FDA issued a new draft guidance on drug interaction studies, which recommends evaluating not only P-gp, but also BCRP, OATP1B1, OATP1B3, OAT1, OAT3, and OCT2. These additional efflux as well as hepatic and renal uptake transporters have been identified as playing a major role in the distribution and disposition of many drugs. The updated recommendations reflect the current state of the science in the drug transporter field, which has evolved substantially in the past six years.

Which CYP isoforms are the most important for assessment?
The new FDA draft guidance recommends routine assessment of investigational drugs as substrates of CYPs 1A2, 2B6, 2C8, 2C9, 2C19, 2D6, and 3A4. If in vitro studies suggest that a drug is not a substrate for any of these CYPs, other CYPs and non-CYP enzymes (including Phase II enzymes such as UGTs) should be investigated. We recommend evaluation of investigational drugs as inhibitors of the same seven major CYPs, although the draft guidance is vague on this point. The guidance recommends evaluation of new drug candidates as inducers of CYPs 1A2, 2B6, and 3A4 to cover all of the major molecular pathways of CYP induction.

Why should I determine a KI and kinact value?
In addition to the fact that both the 2010 EMA guidance and the 2012 FDA draft guidance require these values for identifying time-dependent CYP inhibitors and for designing or waiving clinical DDI studies, K_I and k_inact values enable precise prediction of the impact of a time-dependent inhibitor on the PK of substrates of the inhibited enzyme.

Absorption Systems’ test systems encompass a wide range of services in drug metabolism, pharmacokinetics, transporters, and bioanalysis during the preclinical stage of drug development.

We have extensive experience with new drugs in the late preclinical stage of development, where the focus is on demonstrating safety and efficacy in various preclinical models, sufficient to convince the FDA or other drug regulatory body to allow a clinical trial to proceed.

Our teams are led by Ph.D. scientists who bring institutional knowledge from best-in-class organizations and collectively provide consultative guidance to support your programs.

We are an extension of your team and have substantial experience with FDA audits across all areas.