Drug Safety

Problem: Understanding the Mechanism of Toxicity

In pre-clinical safety assessment, compounds in early development often show signs of toxicity during animal tests.  The challenge is two fold: 1) identifying the mechanism of the toxicity, and 2) identifying biomarkers which can be developed into targeted assays.

Solution: Biochemical Biomarker Discovery

Metabolon's comprehensive biochemical profiling service analyzes a broad range of biochemicals, both indigenous and drug metabolites.  Using a global, non-targeted approach to biomarker discovery, chances are greatly increased that a relevant biomarker will be uncovered.  In many cases, several biomarkers are found which permit the selection of the optimal marker (e.g. a marker which shows early toxicity.)

Case Study: Toxicity for Fenofibrate, a PPAR-alpha Agonist

Objective
Understand the mechanism of toxicity of fenofibrate relative to a lead compound and identify markers associated with cell proliferation.

Methods
Rats in groups of six were treated with fenofibrate (300/mg/kg/day) and a vehicle.  Plasma samples were collected at day 2 (24 samples) and day 14 (24 samples).  Urine samples were collected over 24 hours on dry ice from day 2-3 (24 samples) and day 14-15 (24 samples).

Results
Based on biochemical profiling, there were a number of significant changes in biochemistry.  The table below shows a portion of those changes at day 2 and day 14 (only one of eight tables is shown).  Green indicates increases in the biochemical, compared to the control, and red indicates a decrease.

The overall changes included:

• an acceleration of fatty acid ß-oxidation (decrease in plasma free fatty acid concentrations)
• strong down-regulation of citric acid cycle
• significant increase in plasma cholesterol, and
• an increase in plasma bile acids, indicative of comprised liver function.

Metabolite and pathway-specific changes included:

• significant increases of cholic acid, taruocholic acid and glycocholic acid in plasma were observed, indicative of liver malfunction
• increases of 2-deoxycytidine and cytidine, two major nucleosides in rat plasma which indicated liver malfunction
• increases in allantoin were observed indicating oxidative stress and toxicity
• the increases of urine, beta-hydroxyphenyl-lactic acid (HPLA) and estriol, a main estrogen, were observed, indicating cell proliferation
• up-regulation of kynurenine pathway, which is associated with many diseases, kidney, and liver malfunction
• increase in 3-methyl-L-histidine was seen and has been widely used as an index for muscle proteolysis and protein degradation in humans and animals.  The increased level of methylhistidine is consistent with muscle myopathy observed with fenofibrate treatment in the literature.