Preparation of 125I-celecoxib with high purity as a possible tumor agent

Extraction, purification and radioiodination of Khellin as cancer theranostic agent

Khellin was successfully extracted from Ammi visnaga fruits with a recovery percent of 96.15%. Next radio-iodination of Khellin was successfully achieved with a high yield. The biodistribution study of [131I]iodo-khellin in tumour bearing mice revealed that khellin preferentially localization at tumour tissue. Target prediction study for [131I]iodo-khellin revealed that PI3K and VEGFR are potential targets for iodo-khellin with good affinity. The results of this study potentiate [131I]iodo-khellin as a good theranostic agent for tumour imaging and therapy.

Deuteration versus ethylation - strategies to improve the metabolic fate of an 18F-labeled celecoxib derivative

The inducible isoenzyme cyclooxygenase-2 (COX-2) is closely associated with chemo-/radioresistance and poor prognosis of solid tumors. Therefore, COX-2 represents an attractive target for functional characterization of tumors by positron emission tomography (PET). In this study, the celecoxib derivative 3-([¹⁸F]fluoromethyl)-1-[4-(methylsulfonyl)phenyl]-5-(p-tolyl)-1H-pyrazole ([¹⁸F]5a) was chosen as a lead compound having a reported high COX-2 inhibitory potency and a potentially low carbonic anhydrase binding tendency. The respective deuterated analog [D₂,¹⁸F]5a and the fluoroethyl-substituted derivative [¹⁸F]5b were selected to study the influence of these modifications with respect to COX inhibition potency in vitro and metabolic stability of the radiolabeled tracers in vivo. COX-2 inhibitory potency was found to be influenced by elongation of the side chain but, as expected, not by deuteration. An automated radiosynthesis comprising ¹⁸F-fluorination and purification under comparable conditions provided the radiotracers [¹⁸F]5a,b and [D₂,¹⁸F]5a in good radiochemical yields (RCY) and high radiochemical purity (RCP). Biodistribution and PET studies comparing all three compounds revealed bone accumulation of ¹⁸F-activity to be lowest for the ethyl derivative [¹⁸F]5b. However, the deuterated analog [D₂,¹⁸F]5a turned out to be the most stable compound of the three derivatives studied here. Time-dependent degradation of [¹⁸F]5a,b and [D₂,¹⁸F]5a after incubation in murine liver microsomes was in accordance with the data on metabolism in vivo. Furthermore, metabolites were identified based on UPLC-MS/MS.

The aim of this study is to investigate the influence of deuteration and elongation on an ¹⁸F-labeled COX-2 inhibitor with focus on metabolic stability to develop suitable COX-2 targeting radiotracers.

Radioiodination and in vivo assessment of the potential of newly synthesized pyrrolizine-5-carboxamides derivative in tumor model

Recently, pyrrolizine derivatives have been reported to possess numerous anticancer activities. In a previous study, (EZ)-6-((4-chlorobenzylidene)-amino)-7-cyano-N-(p-tolyl)-2,3-dihydro-1H-pyrrolizine carboxamide (EZPCA) compound was synthesized and the cytotoxic activity of EZPCA toward COX-2 enzyme (overexpressed in cancer cells) was reported. In order to assess the suitability of this compound as a promising pilot structure for in vivo applications, EZPCA was radiolabeled with radioiodine-131 (¹³¹I) and various factors affecting radiolabeling process were studied. Quality control studies of [¹³¹I]iodo-EZPCA were performed using paper chromatography and HPLC was used as a co-chromatographic technique for confirming the radiochemical yield. Biodistribution studies of [¹³¹I]iodo-EZPCA were undertaken in normal and tumor bearing mice. The radiochemical yield percentage of [¹³¹I]iodo-EZPCA was 94.20 ± 0.12%. The biodistribution results showed evident tumor uptake of [¹³¹I]iodo-EZPCA with promising target/non-target (T/NT) ratios. As a conclusion, these data suggest that [¹³¹I]iodo-EZPCA had high binding efficiency, high tumor uptake and sufficient stability to be used be used in diagnostic studies.

Rational design and synthesis of new tetralin-sulfonamide derivatives as potent anti-diabetics and DPP-4 inhibitors: 2D & 3D QSAR, in vivo radiolabeling and bio distribution studies

Type 2 diabetes (T2D) is a severe disease and it is one of the most raising problems worldwide. This study deals with design, synthesis and in vivo determination of a new set of tetralin-sulfonamide derivatives as anti-diabetic and dipeptidyl peptidase-IV (DPP-4) inhibiting agents. Most of the new compounds exhibited significant hypoglycemic effect alongside with DPP-4 suppression potency considering sitagliptin as a reference drug. The most promising compounds 4, 15 showed 2.80 nM DPP-4 IC₅₀ with 20-40 folds selectivity over DPP-8 and DPP-9. 2D and 3D QSAR models were performed using auto QSAR of Schrödinger, QuaSAR of MOE and 3D Field-based QSAR of Schrödinger, respectively. The experimental results revealed that the alignment-independent descriptors, electrostatic and steric field descriptors were significantly correlated with the antidiabetic activity of the new derivatives. In addition, the new compounds were docked in the active site of DPP-4 in reference to sitagliptin to rationalize the binding modes of the compounds with the amino acid residues of the enzyme. Furthermore, ¹³¹I-compound 4 complex was selected to evaluate the pharmacokinetic behavioral profile of compound 4 and its body organs uptakes alongside its elimination pathway as a representative example for the rest of the analogues. The bio distribution pattern of the tracer proved the selective accumulation of ¹³¹I-substrate in the pancreas and rapid clearance from most of the body organs.

Radioiodination and biological evaluation of nizatidine as a new highly selective radiotracer for peptic ulcer disorder detection

Nizatidine has been labeled using [¹²⁵ I] with chloramine-T as oxidizing agent. Factors such as the amount of oxidizing agent, amount of substrate, pH, reaction temperature, and reaction time have been systematically studied to optimize the iodination. Biodistribution studies indicate the suitability of radioiodinated nizatidine as a novel tracer to image stomach ulcer. Radioiodinated nizatidine may be considered a highly selective radiotracer for peptic ulcer imaging.

Radioiodinated famotidine as a new highly selective radiotracer for peptic ulcer disorder detection, diagnostic nuclear imaging and biodistribution

Famotidine was labeled with iodine-125 to obtain 125I-famotidine (125I-fam) as an agent for ulcer imaging. The radiochemical yield of 125I-famotidine reached approximately 98.5 ± 0.23% at optimum conditions of pH, oxidizing agent, reaction time and the amount of substrate. 125I-fam was stable for 48 h. Different chromatographic techniques were used to determine the radiochemical yield and purity. Intravenous biodistribution studies of 125I-fam revealed high concentration in the stomach ulcer, reaching about 65.9 ± 0.28% of the total injected dose at 30 min post injection. This concentration of 125I-fam in stomach ulcer makes this agent promising for stomach ulcer imaging.

Radiolabeled COX-2 inhibitors for non-invasive visualization of COX-2 expression and activity--a critical update

Cyclooxygenase-2 (COX-2) is a key player in inflammation. Its overexpression is directly associated with various inflammatory diseases and, additionally, with several processes of carcinogenesis. The development of new selective COX-2 inhibitors (COXIBs) for use in cancer treatment is in the focus of the medicinal chemistry research field. For this purpose, a set of methods is available to determine COX-2 expression and activity in vitro and ex vivo but it is still a problem to functionally characterize COX-2 in vivo. This review focusses on imaging agents targeting COX-2 which have been developed for positron emission tomography (PET) and single photon emission computed tomography (SPECT) since 2005. The literature reveals that different radiochemical methods are available to synthesize COXIBs radiolabeled with fluorine-18, carbon-11, and isotopes of radioiodine. Unfortunately, most of the compounds tested did not show sufficient stability in vivo due to de[¹⁸F]fluorination or de[¹¹C]methylation or they failed to bind specifically in the target region. So, suitable stability in vivo, matching lipophilicity for the target compartment and both high affinity and selectivity for COX-2 were identified as prominent criteria for radiotracer development. Up to now, it is not clear what approach and which model is the most suited to evaluate COX-2 targeting imaging agents in vivo. However, for proof of principle it has been shown that some radiolabeled compounds can bind specifically in COX-2 overexpressing tissue which gives hope for future work in this field.

Chromatographic techniques in analysis of cyclooxygenase-2 inhibitors in drugs and biological samples

Non-steroidal anti-inflammatory drugs, as a therapeutic class, are among the most often used active pharmaceutical ingredients in heath care in the world. They are mostly available without prescription and often used for treatment of fever and pain. An extensive research of the literature published in analytical and pharmaceutical chemistry journals has been conducted and the chromatographic methods which were used for the purity, stability and pharmacokinetic studies of the cyclooxygenase-2 inhibitors, in formulations and biological materials have been reviewed. The methodology for the analysis of selected drugs is very well documented and many examples are available in the literature. The common use of chromatographic techniques with various detection attachments provide possibility for monitoring of drugs in therapy.