Determine whether a toxic metabolite is formed.

A comparison of treatments in HRN™ and control mice enables determination of whether a toxic metabolite of the compound is formed due to hepatic drug metabolism. An example of this is shown below, which shows the consequences following the administration (i.p.) of a single large dose (300mg/Kg) of acetaminophen (paracetamol) to HRN™ and control mice. In normal mice (green symbols), acetaminophen is metabolised in the liver to generate a toxic metabolite that induces liver damage which results in large (90%) drop in hepatic glutathione levels within 1 hour after administration (bottom panel), and a subsequent large rise in serum alanine aminotransferase (ALT) levels, indicative of extensive (fatal) liver damage (top panel). A similar treatment of HRN™ mice fails to induce a similar change in hepatic glutathione levels or rise in serum ALT, demonstrating a complete lack of toxic metabolite generation.

Effect of high dose acetaminophen administration (300mg/Kg i.p) in Normal and HRN mice. Serum alanine aminotransferase (top panel) and hepatic glutathione (bottom panel) levels in adult male HRN™ and control mice following a single intraperitoneal administration of 300mg/Kg acetaminophen.

This feature of the HRN™ mouse can be usefully employed to demonstrate whether a toxic metabolite of a compound is generated through hepatic CYP metabolism. In addition the HRN™ can also be used to elucidate whether the parent compound or an active metabolite is responsible for pharmacological efficacy, and hence determine whether the compound is actually a pro-drug. This can greatly assist the optimisation of the compound and has important implications for the intellectual property position.