Analytical method validation for biomarkers as a drug development tool: points to consider.

Biomarkers are an important drug developmental tool. Assessment of quantitative analytical methods of biomarkers is not included in any regulatory documents in Japan. Use of biomarkers in clinical evaluations and supporting the post-marketing evaluation of drug efficacy and/or adverse reactions requires assessment and full validation of analytical methods for these biomarkers.

An iminium ion metabolite hampers the production of the pharmacologically active metabolite of a multikinase inhibitor KW-2449 in primates: irreversible inhibition of aldehyde oxidase and covalent binding with endogenous proteins.

We previously reported that KW-2449, (E)-1-{4-[2-(1H-Indazol-3-yl)vinyl]benzoyl}piperazine, a novel multikinase inhibitor developed for the treatment of leukemia patients, was oxidized to an iminium ion intermediate by monoamine oxidase B (MAO-B) and then converted to its oxo-piperazine form (M1) by aldehyde oxidase (AO). However, it was found that the significant decrease in the pharmacologically active metabolite M1 following repeated administration of KW-2449 in primates might hamper the effectiveness of the drug. The mechanism underlying this phenomenon was investigated and it was found that the AO activity was inhibited in a time-dependent manner in vitro under the co-incubation of KW-2449 and MAO-B, while neither KW-2449 nor M1 strongly inhibited MAO-B or AO activity.

Monoamine oxidase B oxidizes a novel multikinase inhibitor KW-2449 to its iminium ion and aldehyde oxidase further converts it to the oxo-piperazine form in human.

(E)-1-{4-[2-(1H-Indazol-3-yl)vinyl]benzoyl}piperazine (KW-2449) is a novel multikinase inhibitor. During our clinical study, we found that KW-2449 is mainly metabolized to its oxo-piperazine form (M1). An inhibition study suggested that monoamine oxidase-B (MAO-B) oxidizes KW-2449 to an iminium (intermediate) and aldehyde oxidase (AO) then metabolizes the intermediate to M1.

Design and synthesis of piperidine farnesyltransferase inhibitors with reduced glucuronidation potential.

The design and synthesis of a novel piperidine series of farnesyltransferase (FTase) inhibitors with reduced potential for metabolic glucuronidation are described. The various substitution and exchange of the phenyl group at the C-2 position of the previously described 2-(4-hydroxy)phenyl-3-nitropiperidine 1a (FTase IC(50)=5.4nM) resulted in metabolically stable compounds with potent FTase inhibition (14a IC(50)=4.

Determination of the anticancer drug KW-2170, a pyrazoloacridone derivative, and its metabolites in human and dog plasma by high-performance liquid chromatography using an electrochemical detector.

KW-2170, 5-(3-aminopropyl) amino-7,10-dihydroxy-2-(2-hydroxethyl)-aminoethyl-6H-pyrazolo [4,5,1-de] acridin-6-one dihydroxychloride, is a novel anticancer agent under clinical development. We have established a highly sensitive method which can simultaneously quantitate KW-2170 and its two metabolites, a carboxylic (M1) and hydroxylated (M2) derivative involving the 5-position, in human and dog plasma. KW-2170 and its metabolites were extracted from plasma using a weak cation-exchange cartridge and then determined by HPLC using an electrochemical detector (ED).