Toxicokinetic (TK) Analysis, GLP Tox Study Bioanalysis by PhDs at 20+ Year, FDA-Inspected Lab

In-vivo toxicology studies are required before FIH (First In Human) dosing and are usually performed under GLP conditions using detailed protocols. A general scheme used in the industry for preclinical studies of lead compounds before the commencement of clinical trials is as follows: Acute (single-dose) toxicity dose ranging study, maximum tolerated dose (MTD) study, Repeat-dose toxicity – 2 to 14 weeks (daily dosing, required by regulators in two species, one rodent and one non-rodent), carcinogenicity – up to 2 years of dosing in rodents for chronic treatments, genotoxicity- in vivo mouse micronucleus test, mutagenicity – in vitro AMES test, cardiovascular risk by hERG inhibition, chromosome aberration, and in-vivo respiratory and cardiovascular safety pharmacology studies, as applicable. The majority of these GLP toxicity studies follow regulatory guidance with quality oversight and are performed as toxicology services by CROs.

Toxicokinetic (TK) study is simply a pharmacokinetic study of the drug when administered at quantities higher than the therapeutic dose to evaluate potentially toxic levels of the drug. Thus, Toxicokinetics is the appropriate term for studying the systemic kinetics of all substances at exposure levels ranging from therapy to toxicity. During a GLP toxicity study by FDA standards, the body reaches the maximum tolerated dose (MTD), the dose level yielding the drug’s exposure to the point of toxicity, or the maximum feasible dose (MFD), the highest dose level that can be administered based on physicochemical limitations. Understanding the dosage and systemic exposure of the drug during toxicology studies is essential as this aspect defines the difference in medicine being therapeutic vs. toxic. This difference explains the drug’s therapeutic index, representing the safety margins between therapy (minimum efficacious dose) and toxicity (maximum tolerated dose or maximum feasible dose). The same drug given in a small quantity may start healing at the site of action. But, when administered at a high dose, it can even be fatal for the human body.

The necessity for toxicokinetic analysis lies in the study’s ability to provide insights on molecules’ systemic exposure related to adverse effects. This aspect is an incredibly important consideration for the cardiovascular system, the central nervous system, and respiratory assessments. Furthermore, acute single dose toxicity studies carried under this analysis assist in predicting the duration and rate of exposure at the time of one dosing interval and whether systemic accumulation occurs following multiple drug administrations in repeated dose toxicity studies. This benchmark information provides the right dose levels for later stages of the compound development.

Overall, the data obtained from toxicokinetic studies assess the toxic responses of various drug compounds. This study’s result becomes the basis for knowing the right starting dose of a new drug that is safe for the human body. Moreover, the analysis may provide insights into how certain medications can diversely affect people of different ages, genders, and ethnicities.

The toxicokinetic process mathematically models the four dispositional factors that act on a compound in a biological system referred to as ADME. They include uptake of the drug into the systemic circulation, or absorption (A), distribution (D) from the bloodstream to cells and tissues within the body, conversion to new entities by biotransformation or metabolism (M), and excretion (E) of the compound and its biotransformation products. Toxicity is often associated with the conversion of the drug compound to more reactive metabolites. We perform toxicokinetic analysis by assessing systemic exposures via bioanalysis of active pharmaceutical ingredients and metabolites, followed by toxicokinetic analysis using the in-vivo time vs. concentration results. Toxicology studies allow determination of i) No observed effect level (NOEL) – the highest dose or exposure that produces no effect, ii) No observed adverse effect level (NOAEL) – the highest dose or exposure that has manageable toxicity, and iii) Therapeutic index (margin of safety) – the range encompassing minimum efficacious dosage to the maximum tolerated dose.

Predictive safety runs in silico and in vitro before animals are ever dosed: structure-based mutagenicity prediction, then microsome, hepatocyte, hERG and Ames assays that flag mechanisms early and reduce animal use. In vivo toxicology remains the decisive tier: MTD and acute studies, repeat-dose GLP toxicology in two species, and genetic and reproductive packages as the program requires. The in-life work runs at tox facilities; the toxicokinetic bioanalysis that turns those studies into exposure evidence runs here.

Nonclinical toxicology and safety pharmacology tests assess a drug’s potential for adverse and undesired effects in animal models before initial testing in humans. The terms nonclinical and preclinical are often used interchangeably since nonclinical tests are evaluated before the inception of clinical trials on novel drug entities.

We must obtain nonclinical GLP toxicology data for all lead candidates before filing the Investigational new drug application (IND). In-vitro toxicology studies in drug development test mechanisms such as metabolic reactivity, inhibition, induction, mutagenicity, and cytotoxicity. Study results from these assays alert scientists to potential problems or limitations. We perform in-vivo acute and chronic toxicology studies in drug development to optimize and characterize lead discovery candidates. Furthermore, novel techniques including toxicometabonomics, toxicoproteomics, and toxicogenomics can provide higher throughput approaches to identify in-vivo toxic responses soon after dosing or aid in selecting specific endogenous biomarkers for both clinical toxicological analysis and preclinical detection of potential toxicities.

Toxicity testing starts with IACUC approval at the facility running the animals. Acute single-dose studies observe effects for about 14 days after one administration; repeat-dose studies in rodents establish maximum tolerated dose, target tissues and safety pharmacology before nonclinical development. The in-life dosing runs at your tox facility or one of our partners; the samples ship here, where the TK bioanalysis, exposure analysis and reporting happen. That split is deliberate, and the page above explains why sponsors prefer it.

TK analysis is the subdivision of PK to test the relationship between systemic drug exposure and its toxicity in various species. Pharmacokinetic studies determine the systemic exposure of drug administration to living organisms over time after dosing. Toxicokinetic studies are generally carried out with higher doses as compared to pharmacokinetic studies. The objective of toxicokinetic studies is to quantify a compound’s pharmacokinetics in toxicological study species at toxicological doses. TK exposures may increase non-linearly with dosage due to absorption differences, metabolic saturation, or metabolic alterations resulting from the test article’s chronic usage. TK analyses are often used additionally to investigate drug accumulation with repeated dosing, gender differences, and quantitation of known drug metabolites or pharmacodynamic or toxicodynamic biomarkers.

Pharmacokinetics (PK) encompasses the analysis and description of a drug’s disposition in the body, with a mathematical description of all dispositional processes (ADME – Absorption, Distribution, Metabolism, and Elimination). Toxicokinetic (TK) analysis applies PK principles to the disposition of toxicants and their metabolites related to the time course of toxic or adverse events. PK or TK parameters are determined for the majority of studies using non-compartmental analysis (NCA).

CDER’s SEND (Standard for Exchange of Nonclinical Data) allows for data transfer to the FDA and other national regulatory agencies in a harmonized format allowing for more efficient and standardized regulatory review readable by Janus Nonclinical software. SEND mirrors the Study Data Tabulation Model (SDTM) used for clinical trial results. At present, tox studies fitting in the electronic Common Technical Document format (eCTD) modules 4.2.1.3 (Safety Pharmacology), 4.2.3.1 (Single Dose Toxicity), 4.2.3.2 (Repeat-Dose Toxicity), and 4.2.3.4 (Carcinogenicity) with study start dates on or after March 15, 2019 for NDA/BLA submissions and on or after March 15, 2020 for commercial IND submissions require data submission following the SENDIG 3.1 (SEND Implementation Guide version 3.1). New data standards will be needed for any studies started 24 months after the publication of a Federal Register Notice (FRN) announcing FDA support of the standard and placement on the FDA Data Standards Catalog. The FDA Office of Computational Science (OCS) currently offers a KickStart Program to assist applicants and reviewers in the SEND standard and data transfers to Janus Nonclinical.

No, and that is the point of this page. Dosing and in-life observation run at your tox facility, or we get the in-life study quoted through partner facilities if you need one. The TK bioanalysis runs here, independently, which gives your program a second set of eyes on the exposure data instead of one vendor grading its own work. Samples ship directly from the tox facility with chain of custody documented the day they land.

About two weeks for a complete study set. TK samples arrive as one batch when dosing ends, so the study runs as a study rather than dribbling through a queue, and the exposure data reaches your study director while the report is still being written, not after.