Evaluation of Chemical, Physical, and Biologic Properties of Tumor-Targeting Radioiodinated Quinazolinone Derivative

Abstract

Our group is developing a novel technology, enzyme-mediated cancer imaging and therapy (EMCIT), that aims to entrap radioiodinated compounds within solid tumors for noninvasive tumor detection and therapy. In this approach, a water-soluble, radioiodinated prodrug is hydrolyzed in vivo to a highly water-insoluble compound by an enzyme overexpressed extracellularly by tumor cells. We have synthesized and characterized the water-soluble prodrug, 2-(2'-phosphoryloxyphenyl)-6-[(125)I]iodo-4-(3H)-quinazolinone [(125)I]5, which is readily hydrolyzed by alkaline phosphatase, an enzyme expressed by many tumor cell lines, to a water-insoluble drug, 2-(2'-hydroxyphenyl)-6-[(125)I]iodo-4-(3H)-quinazolinone [(125)I]1. In the course of our study, we discovered that ammonium 2-(2'-phosphoryloxyphenyl)-6-tributylstannyl-4-(3H)-quinazolinone, an intermediate in the radioiodination of the prodrug, exists as two isomers (3 and 4) whose radioiodination leads, respectively, to [(125)I]6 and [(125)I]5. These prodrugs have different in vitro and in vivo biologic activities. Compound 6 is not hydrolyzed by alkaline phosphatase (ALP), whereas 5 is highly soluble (mg/mL) in aqueous solution and is rapidly dephosphorylated in the presence of ALP to 1, a water-insoluble molecule (ng/mL). Mouse biodistribution studies indicate that [(125)I]6 has high uptake in kidney and liver and [(125)I]5 has very low uptake in all normal organs. Compounds 3 and 6 are converted, respectively, to 4 and 5 after incubation in DMSO. The stability of 5 in human serum is high. The minimum ALP concentration needed to hydrolyze 5 is much greater than the ALP level in the blood of patients with cancer, and the latter should not affect the pharmacokinetics of the compound. Incubation of 5 with viable human and mouse tumor-cell lines--but not with normal human cells and mouse tissues--leads to its hydrolysis and the formation of large crystals of 1. We expect that 5 will also be hydrolyzed in vivo by tumor cells that express phosphatase activity extracellularly and anticipate the specific precipitation of radioiodinated 1 within tumor cell clusters. This should lead to high tumor-to-normal-tissue ratios and enable imaging (SPECT/PET) and radionuclide therapy of solid tumors.

Computational Modeling and Experimental Evaluation of a Novel Prodrug for Targeting the Extracellular Space of Prostate Tumors

“…These studies also indicated that (a) IQ 2-P is a highly water-soluble molecule (mg/mL) that is stable in human serum and readily dephosphorylated by ALP to the water-insoluble IQ 2-OH derivative; (b) the in vitro incubation of 127 IQ 2-P / 125 IQ 2-P derivatives with several ALP-expressing human and mouse tumor cell lines results in the efficient and rapid formation of the corresponding water-insoluble derivatives 127 IQ 2-OH / 125 IQ 2-OH ; and (c) the intratumoral injection of 125 IQ 2-P into ALP-expressing solid human tumors grown in rats leads to the efficient hydrolysis of the compound and the retention of f70% of the injected radioactivity, whereas similar injection into normal tissues (e.g., muscle) leads to little measurable hydrolysis (f1%) and lack of retention of radioactivity at injected sites. In addition, we observed that the pharmacokinetic properties of IQ 2-P in mice were not consistent (5). Subsequently, we recognized that the synthesis of its stannylated quinazolinone precursor (SnQ 2-P ) produces a mixture of two compounds, SnQ 2-P and SnQ 2-P(I) (f1:1 ratio), whose radioiodination leads to the formation of 125 IQ 2-P and its cyclic isoform 125 IQ 2-P(I) , respectively.…”

“…Furthermore, it has been shown that pure 125 IQ 2-P can be prepared following an overnight incubation of the tin precursor mixture in DMSO and that, on its i.v. injection into mice, there is minimal retention (<0.4% injected dose per gram) of radioactivity in all normal tissues (5).…”

“…Toward these objectives, we present a novel approach, Enzyme-Mediated Cancer Imaging and Therapy (EMCIT; refs. [1][2][3][4][5], which potentially enables the active entrapment of a radioisotopically labeled compound within the extracellular spaces of primary prostate tumors and their metastases (Fig. 1).…”

“…The prototype for this approach was first developed for alkaline phosphatase (ALP; EC 3.1.3.1), a hydrolase with monophosphoesteric activity that is overexpressed on the plasma membranes of many tumor cell types (1,2,6,7). A suitable substrate, the prodrug ammonium 2-(2 ¶-phosphoryloxyphenyl)-6-iodo-4-(3H)-quinazolinone ( 127 IQ 2-P ), and its radioiodinated analogue ( 125 IQ 2-P ) were synthesized, purified, and characterized (1,5), and their ALP-mediated hydrolysis to the water-insoluble, fluorescent 2-(2 ¶-hydroxyphenyl)-6-iodo-4-(3H)-quinazolinone derivatives ( 127 IQ 2-OH and 125 IQ 2-OH ) was shown (1,3,5). These studies also indicated that (a) IQ 2-P is a highly water-soluble molecule (mg/mL) that is stable in human serum and readily dephosphorylated by ALP to the water-insoluble IQ 2-OH derivative; (b) the in vitro incubation of 127 IQ 2-P / 125 IQ 2-P derivatives with several ALP-expressing human and mouse tumor cell lines results in the efficient and rapid formation of the corresponding water-insoluble derivatives 127 IQ 2-OH / 125 IQ 2-OH ; and (c) the intratumoral injection of 125 IQ 2-P into ALP-expressing solid human tumors grown in rats leads to the efficient hydrolysis of the compound and the retention of f70% of the injected radioactivity, whereas similar injection into normal tissues (e.g., muscle) leads to little measurable hydrolysis (f1%) and lack of retention of radioactivity at injected sites.…”

Antipsychotic Potential of Quinazoline ErbB1 Inhibitors in a Schizophrenia Model Established With Neonatal Hippocampal Lesioning

“…We confirmed the position of the cannula after completion of the behavioral tests. The ErbB1 inhibitors, PD153035 [4-(3-bromophenylamine)-6,7-dimethoxy-quinazoline; Calbiochem, San Diego, CA, USA], ZD1839 [gefitinib, 4-(3-chloro-4-fluorophenylamine)-7-methoxy-6(3-(4-morpholinyl)-quinazoline; AstraZeneca Pharmaceuticals, Osaka], and OSI-774 (erlotinib, 4-(3-ethynylphenylamine)-6,7-bis (2-methoxyethoxy)-quinazoline; OSI Pharmaceuticals, Melville, NY, USA] were dissolved in 100% DMSO, diluted with saline, and added to an osmotic minipump (35). The effective doses were determined in another animal model for schizophrenia (M. Mizuno, unpublished data).…”