Pharmacokinetics and anti-tumor activity of AY002 with high affinity to EGFR-TK

Objectives Epidermal growth factor receptor tyrosine kinase (EGFR-TK) is an attractive target for tumor diagnosis and therapy because of its abundant expression on various types of tumor cells. We have developed anilinopyrimidine derivatives as EGFR-TK imaging probes and found that AY002, {3-[6-(3-iodophenylamino)-pyrimidin-4-ylamino]-phenyl}-amide, significantly inhibited cell proliferation and phosphorylation of EGFR-TK. Here, we evaluated therapeutic effect of AY002 and its pharmacokinetics by SPECT imaging.

Methods Affinities of AY002 and gefitinib were evaluated by surface plasmon resonance (SPR). Biotinylated EGFR-TK was immobilized on a sensor chip. Interactions between AY002 or gefitinib and EGFR-TK were analyzed using One-Shot Kinetics approach. Therapeutic analysis, biodistribution and SPECT/CT imaging studies were carried out using A431 bearing nude mice. For the therapeutic study, AY002 (100 mg/kg or 250 mg/kg) was administered to the mice 5 days a week for two weeks.

Results SPR revealed that AY002 has high affinity to EGFR (Kd = 15.5 nM). The Kd of gefitinib was 1.12 nM. In the therapeutic study, AY002 moderately suppressed the tumor growth. The biodistribution and SPECT/CT studies demonstrated that high uptake of ¹²⁵I-AY002 was observed in the liver (22.5 %ID/g) and the gallbladder (1.6 %ID) at 10 min after i.v. injection. The intestinal uptake drastically increased to 32.3 %ID/g at 1 h though the liver uptake was cleared, indicating rapid hepatobiliary excretion. The biodistribution and SPECT/CT studies via p.o. administration indicated ¹²⁵I-AY002 was slightly absorbed via the intestine and rapidly excreted in the gallbladder.

Conclusions Our studies revealed that the pharmacokinetics of AY002 was rapidly excreted via hepatobiliary system. Although AY002 had potent antiproliferative activity compared to gefitinib in in vitro, this rapid excretion would result in the moderate suppression of tumor growth.