Gauri Shukla

Synthesis of Specific SPECT-Radiopharmaceutical for Tumor Imaging Based on Methionine: 99mTc-DTPA-bis(methionine)

Methionine-diethylenetriaminepentaaceticacid-methionine [DTPA-bis(Met)] was synthesized by covalently conjugating two molecules of methionine (Met) to DTPA and was labeled with (99m)Tc in high radiochemical purity and specific activity (166-296 MBq/micromol). Kinetic analysis showed K(m) of 12.95 +/- 3.8 nM and a maximal transport rate velocity (V(max)) of 80.35 +/- 0.42 pmol microg protein(-1) min(-1) of (99m)Tc-DTPA-bis(Met) in U-87MG cells. DTPA-bis(Met) had dissociation constants (K(d)) of 0.067 and 0.077 nM in U-87MG and BMG, respectively. (35)S-methionine efflux was trans-stimulated by (99m)Tc-labeled DTPA conjugate demonstrating concentrative transport. The blood kinetic studies showed fast clearance with t(1/2) (F) = 36 +/- 0.5 min and t(1/2) (S) = 5 h 55 min +/- 0.85 min. U-87MG and BMG tumors saturated at approximately 2000 +/- 280 nmol/kg of (99m)Tc-DTPA-bis(Met). Initial rate of transport of (99m)Tc-DTPA-bis(Met) in U-87MG tumor was found to be 4.68 x 10(-4) micromol/kg/min. The tumor (BMG cell line, malignant glioma) grafted in athymic mice were readily identifiable in the gamma images. Semiquantitative analysis from region of interest (ROI) placed over areas counting average counts per pixel with maximum radiotracer uptake on the tumor was found to be 11.05 +/- 3.99 and compared ROI with muscle (0.55 +/- 0.13). The tumor-to-contralateral muscle tissue ratio of (99m)Tc-DTPA-bis(Met) was found to be 23 +/- 3.3. Biodistribution revealed significant tumor uptake and good contrast in the U-87MG, BMG, and EAT tumor-bearing mice. In clinical trials, the sensitivity, specificity, and positive predictive values were found to be 87.8%, 92.8%, and 96.6%, respectively. (99m)Tc-DTPA-bis(Met) showed excellent tumor targeting and has promising utility as a SPECT-radiopharmaceutical for imaging methionine-dependent human tumors and to quantify the ratio of MET(+)/HCY(-).

99mTc‐DTPA‐Amino Acids Conjugate as Specific SPECT Pharmaceuticals for Tumor Imaging

99mTc‐Diethylene triamine pentaacetic acid‐bis (amide) conjugates have been synthesized and evaluated as a potential radiopharmaceutical for tumor imaging. The compounds were synthesized by the condensation reaction of DTPA bis(anhydride) with different l‐amino acids (methyl tryptophan, and 5‐hydroxy tryptophan) and were characterized on the basis of IR, NMR, and Mass spectroscopy. 99mTc‐labeled compounds were found stable for about 24 h under physiological conditions with more than 95% radiolabeling yield. Blood kinetic studies of all these complexes showed a bi‐exponential pattern as well as quick wash out from the blood circulation. The biological t1/2(F) and t1/2(S) were found to be 20 ± 0.001 min for DTPA‐(Me‐Trp)2 and 18 ± 0.001 min for DTPA‐(5HT)2 and t1/2 (slow) 5 h 45 min ± 0.001, 5 h 30 ± 0.001 min for DTPA‐(Me‐Trp)2, and DTPA‐(5HT)2, respectively. Imaging and biodistribution studies were performed in mice bearing Ehrlich ascites tumor (EAT) tumors in right thigh. Radioconjugate derived from l‐5‐hydroxytryptophan exhibited remarkable localization at tumor site; whereas radiotracer derived from l‐methyl tryptophan shows relatively less accumulation at the tumor site. Tumor‐to‐muscles ratios were 5.07 ± 0.001, and 4.2 ± 0.001 at 1 and 4 h for 99mTc‐DTPA‐(Me trp)2 and 4.97 ± 0.001 and 5.8 ± 0.001 at 1 and 4 h after postinjection for 99mTc‐DTPA‐(5HT)2, respectively. The preliminary results with these amino acid based ligands are encouraging to carrying out further in vivo experiments for targeted tumor imaging.

Effect of a Novel Series of Benzothiazolo-Quinazolones on Epidermal Growth Factor Receptor (EGFR) and Biological Evaluations

A newly designed benzothiazolo‐quinazolone series was synthesized by an aromatic amine and potassium thiocyanate in the presence of bromine in glacial acetic acid, and the final product was obtained by subsequent reaction with 5‐arylamido/imidoalkyl‐2‐chlorobenzoic acid in the presence of potassium carbonate and further cyclization with sulphuric acid. A preliminary radiolabelling study with technetium shows a promising potential for further in vivo evaluation. Anti‐bacterial, anti‐viral and anti‐tumor activities were evaluated for biological properties. Lead compounds are able to block epidermal growth factor receptor (EGFR) in human breast adenocarcinoma cell line, MCF‐7.

Quantitative Structure–Property Relationship (Correlation Analysis) of Phosphonic Acid-Based Chelates in Design of MRI Contrast Agent

Nuclear magnetic resonance imaging is a very useful tool in modern medical diagnostics, especially when gadolinium (III)‐based contrast agents are administered to the patient with the aim of increasing the image contrast between normal and diseased tissues. With the use of soft modelling techniques such as quantitative structure–activity relationship/quantitative structure–property relationship after a suitable description of their molecular structure, we have studied a series of phosphonic acid for designing new MRI contrast agent. Quantitative structure–property relationship studies with multiple linear regression analysis were applied to find correlation between different calculated molecular descriptors of the phosphonic acid‐based chelating agent and their stability constants. The final quantitative structure–property relationship mathematical models were found as – quantitative structure–property relationship Model for phosphonic acid series (Model 1) − log KML = {5.00243(±0.7102)}− MR {0.0263(±0.540)}n = 12 l r l = 0.942 s = 0.183 F = 99.165 quantitative structure–property relationship Model for phosphonic acid series (Model 2) − log KML = {5.06280(±0.3418)}− MR {0.0252(± .198)}n = 12 l r l = 0.956 s = 0.186 F = 99.256.

Synthesis and Biological Evaluation of 99mTc-DTPA-bis(His) as a Potential Probe for Tumor Imaging with SPECT

(99m)Tc-DTPA-bis(His) conjugate has been synthesized and evaluated as a potential radiopharmaceutical for tumor imaging. The compound was synthesized by the covalent coupling of DTPA bis(anhydride) with L-histidine and was characterized on the basis of infrared, nuclear magnetic resonance, and mass spectroscopy. (99m)Tc-labeled compound was found stable for about 24 hour under physiologic conditions with a more than 96% radiolabeling yield. A blood kinetic study of this complex showed a biexponential pattern as well as quick washout from the blood circulation. The biologic t(1/2)(F) and t(1/2)(S) was found to be 45 +/- 0.041 minutes and 6.5 hours +/- 0.039 minutes, respectively. Imaging and biodistribution studies were performed in mice bearing Ehrlich ascites tumor (EAT) tumors in the right thigh. The EAT tumors in the mice were readily visible in the gamma-images and showed major accumulation of the radiotracer in the kidney. Biodistribution studies revealed a high accumulation at the tumor site. Tumor-to-muscle ratios were 5.07 +/- 0.08 and 4.2 +/- 0.01 at 1 and 4 hours, respectively. The receptor binding of the (99m)Tc-DTPA-bis(His) by an established human tumor cell line (U87-MG) showed K(D) = 1.08 nM. The preliminary studies of the (99m)Tc-DTPA-bis(His) are encouraging to carrying out further in vivo experiments for targeted tumor imaging.

99mTc-methionine scintimammography in the evaluation of breast cancer.

ObjectiveThe diagnostic utility of a 11C-methionine scan has been established in breast cancer. We were able to radiolabel methionine with 99mTc at our institute. Thus, we undertook clinical trials to determine the role of 99mTc-methionine scans in the detection of breast cancer. MethodsScintimammography was performed in 47 female (median age 44 years, range 28–68 years) patients having palpable breast masses. All of them underwent ultrasound, mammography, fine-needle aspiration cytology, and 99mTc-methionine scintimammography before surgery. The final diagnosis was made after histopathological examination. 99mTc-methionine scintimammography was done after injecting 555 MBq of radiotracer intravenously. The results of scintimammography were compared with histopathology. ResultsThe histopathological findings were malignant in 33 (70%) and benign in 14 (30%) cases. Scintimammography showed true-positive findings in 29 patients out of 33 cases of breast cancer. True-negative findings were found in 13 out of 14 patients having benign breast lesions. The sensitivity, specificity, and positive predictive value were found to be 87.8, 92.8, and 96.6% respectively. Conclusion99mTc-methionine imaging can provide useful information with reasonably high sensitivity and specificity in evaluating patients having breast masses.

Synthesis and assessment of 99mTc chelate-conjugated alendronate for development of specific radiopharmaceuticals.

Indole-based alendronate (AI) was derived from the condensation reaction of indole 3-carboxaldehyde with sodium alendronate (ALN) and was characterized by various spectroscopic methods (e.g., ultraviolet, fourier-transform-infrared, and liquid chromatography mass spectrometry). The AI was labeled with (99m)Tc and radiochemical purity was above 97%, which was ascertained by instant thin-layer chromatography, using different solvent conditions, with a specific activity 2-5 mCi/mg. The receptor ligand assay on human bone cell line Soas-2 showed K(D) = 0.55 nM. The derivative (AI) was stable, which was determined under physiologic conditions up to 24 hours The blood kinetic study showed a biexponential pattern as well as quick wash-out from the circulation with varying biologic t(1/2)(F) and t(1/2)(S). Excellent-quality radio images were recorded of bone, showing a rapid clearance of background activity, at an early visualization at 1.5 hours. The excretory pathway of the derivative was through the kidneys, which was evidenced by biodistribution studies. Thus, the newly synthesized derivative can be considered as a specific bone-seeking agent.

Polyethylene glycol conjugates of methotrexate and melphalan: synthesis, radiolabeling and biologic studies.

Polyethylene glycols (PEGs) are potential drug carriers for humanizing the therapeutic index of anti-cancer agents. In this paper, we report on the modification of the anticancer drugs, methotrexate (MTX) and melphalan (L-PAM), covalently linked to PEGs for drug delivery. Conjugates of MTX and L-PAM were analyzed through different spectroscopic techniques. Both conjugates were labeled with (99m)Tc by the classical way, using reducing agents at a physiologic pH. Blood kinetic data revealed the biphasic pattern of clearance. Evaluation of the in vitro cytotoxicity of the drug polymer conjugates on the U87MG human glioma cell line revealed that the conjugates showed enhanced dose-dependent cytotoxicity.