Direct radioiodination of metabolic 8-hydroxy-quinolyl-glucuronide, as a potential anti-cancer drug

New transient receptor potential vanilloid subfamily member 1 positron emission tomography radioligands: synthesis, radiolabeling, and preclinical evaluation

The transient receptor potential vanilloid subfamily member 1 (TRPV1) cation channel is known to be involved in pain nociception and neurogenic inflammation, and accumulating evidence suggests that it plays an important role in several central nervous system (CNS)-related disorders. TRPV1-specific positron emission tomography (PET) radioligands can serve as powerful tools in TRPV1-related (pre)clinical research and drug design. We have synthesized several potent TRPV1 antagonists and accompanying precursors for radiolabeling with carbon-11 or fluorine-18. The cinnamic acid derivative [(11)C]DVV24 and the aminoquinazoline [(18)F]DVV54 were successfully synthesized, and their biological behavior was studied. In addition, the in vivo behavior of a (123)I-labeled analogue of iodo-resiniferatoxin (I-RTX), a well-known TRPV1 antagonist, was evaluated. The binding affinities of DVV24 and DVV54 for human TRPV1 were 163 ± 28 and 171 ± 48 nM, respectively. [(11)C]DVV24, but not [(18)F]DVV54 or (123)I-RTX, showed retention in the trigeminal nerve, known to abundantly express TRPV1. Nevertheless, it appears that ligands with higher binding affinities will be required to allow in vivo imaging of TRPV1 via PET.

A correlative study between 99mTc-ESTCPTA and 99mTc-MIBI in rats

Tissue distribution of the 99mTc labeled derivative of the estrogen compound 3,17-alpha-estradiolyl propyl 1,4,8,11-tetraazacyclotetradecanyl-l-(4-methylbenzoic acid) ester (ESTCPTA), which has an 3,17-alpha-estradiolyl propinol coupled to l-(4-methylbenzoic acid)1,4,8,11-tetraazacyclotetradecane (CPTA), was compared to 99mTc-MIBI (methoxyisobutyl isonitrile) in female Albino Wistar rats. Tissues of interest included lung, liver, heart, kidneys, spleen, stomach, intestines, pancreas, muscle, blood, breast, ovary, fat, and uterus. 99mTc-ESTCPTA uptake by the uterus and ovary, as ER-rich tissues, was highly selective. Maximum uptakes for 99mTc-MIBI and 99mTc-ESTCPTA are 90 min in breast, ovary and uterus. The pancreas also showed significant receptor saturated and unsaturated ratios for 99mTc-ESTCPTA. Results are sufficiently encouraging to generate further evaluation of these and related compounds as possible estrogen receptor based tumor imaging and therapeutic agents in estrogen-rich tissues.

Self-radioiodination of iodogen

Iodogen (1,3,4,6-tetrachloro-3alpha,6alpha-diphenylglucoluril) is commonly used for the radioiodination of proteins as an oxidative agent. The oxidative character of iodogen is not clear, but the two carbonyl groups in its structure probably have an essential role in its oxidizing character. In this study, the self-radioiodination of iodogen has been examined. It was observed that about 10-20% of the initial iodine radioactivity was consumed for the self-radioiodination of iodogen itself. On the other hand, the radioiodinated iodogen removed by ethyl alcohol from the iodogen-coated tubes showed clearly that no thyroid uptake was observed and that it was rapidly cleared out from the whole body of a rabbit administered with the radioiodinated iodogen by injection via the ear vein.

Synthesis and cytotoxicity evaluation of some 8-hydroxyquinoline derivatives

Interest in Mannich bases of 8-hydroxyquinoline stems from reports of their high potency against human cancer cells. In the search for potential anticancer drug candidates, Mannich bases of 8-hydroxyquinoline (7-pyrrolidinomethyl-8-hydroxyquinoline, 7-morpholinomethyl-8-hydroxyquinoline, 7-piperidinomethyl-8-hydroxyquinoline and 7-diethylaminomethyl-8-hydroxyquinoline) were synthesised by reaction with various secondary amines and formaldehyde. They were prepared as hydrochlorides. The cytotoxic activity of 7-pyrrolidinomethyl-8-hydroxyquinoline, 7-morpholinomethyl-8-hydroxyquinoline and 7-diethylaminomethyl-8-hydroxyquinoline compounds in the National Cancer Institute in-vitro cancer cell line panel was determined. It was found that they exhibited substantial cytotoxic activity against leukaemia. The log concentration of 7-pyrrolidinomethyl-8-hydroxyquinoline, 7-morpholinomethyl-8-hydroxyquinoline and 7-diethylaminomethyl-8-hydroxyquinoline that inhibited 50% of 60 cell lines' growth were -4.81 M, -5.09 M and -5.35 M, respectively. Compound 7-pyrrolidinomethyl-8-hydroxyquinoline was selected for further in-vivo testing. The electrophysiological effect of 7-pyrrolidinomethyl-8-hydroxyquinoline also was tested in human myeloma cells (RPMI 8226). The outward current was voltage dependent, activating at -40 mV and believed to be the voltage-activated K+ current I(K(V)). 7-Pyrrolidinomethyl-8-hydroxyquinoline (1-30 microM) caused the inhibition of I(K(V)) in a concentration-dependent manner. The IC50 value of 7-pyrrolidinomethyl-8-hydroxyquinoline-induced inhibition of I(K(V)) is 23 microM. The GI50 value of 7-pyrrolidinomethyl-8-hydroxyquinoline-induced inhibition of cell growth is 14 microM. The results suggest that at least part of the cytotoxicity effect of 7-pyrrolidinomethyl-8-hydroxyquinoline on myeloma cells could be related to blockade of voltage-activated K+ channels.

Synthesis and iodine-125 labelling of glucuronide compounds for combined chemo- and radiotherapy of cancer

Some types of cancer cells have high levels of beta-glucuronidase activity. This enzyme is able to deglucuronidate a variety of glucuronide derivatives on the cell membrane. Either O- or N-glucuronides can be selectively incorporated into the cancer cells. If the aglycone is cytotoxic, the glucuronide can potentially be used as a selective anti-cancer drug in cancers with high levels of beta-glucuronidase activity. Nevertheless, in vitro studies carried out by various investigators have shown that the cytotoxicities of several glucuronides in cancer cells are not sufficiently high for their use as effective anti-cancer drugs. For this reason, we have synthesized glucuronide compounds radiolabelled with iodine-125 combining the radiotoxicity of this Auger electron emitter with the chemotoxicity of the aglycone portion of the glucuronide.