(153)Sm-EDTMP for pain relief of bone metastases from prostate and breast cancer and other malignancies.

BACKGROUND AND AIMS: Approximately 85% of patients with cancer suffer severe metastatic bone pain for which radionuclide therapy has been employed for pain palliation. We undertook this study to evaluate the pain relief effect of (153)Sm-EDTMP in Mexican patients with severe and painful bone metastases from mainly prostate, breast, and renal cancer and other malignancies. METHODS: Patients (277) with intense sustained pain caused by bone metastases were referred to the Nuclear Medicine Department of the Oncology Hospital of the Mexican Social Security Institute. The patients had to have acceptable physical conditions, a previous positive (99m)Tc-MDP scan and blood values within normal range. (153)Sm-EDTMP was prepared at the Instituto Nacional de Investigaciones Nucleares (ININ) and 37 MBq/kg of body weight was injected intravenously. Pain palliation was evaluated with a visual analogue scale (VAS) and a verbal rating scale (VRS) before treatment and 3 and 12 weeks after treatment was started. RESULTS: The age interval of the patients was 24-92 years with a mean age of 64 ± 12 years. Mean values for hemoglobin, leukocyte and platelet counts did not statistically differ at zero time, 3 and 12 weeks after treatment. Pain intensity and relief assessment were statistically different: 9.1 ± 0.61 units initially; 4.2 ± 1.3 units 3 weeks later (54%) and after 12 weeks the pain diminished to 2.4 ± 1.4 units (74%) in the pain relief score scales. CONCLUSIONS: (153)Sm-EDTMP was readily available, safe and well tolerated. We conclude that (153)Sm-EDTMP was an adequate palliative agent and was the best option for our Mexican patients to relieve their severe metastatic bone pain.

¹5³Sm-HM for arthritic knee pain. Estimated dosimetry.

Osteoarthritis is the most common type of arthropathy and after cardiovascular diseases is the most disabling disease in developing countries. The dosimetry for the clinical application of 153-samarium-hydroxymacroaggregates (¹5³Sm-HM) for radiation synovectomy (RSV) and palliative treatment for arthritic pain, as far as we know, has not been reported. The aim of this research was to estimate the radiation dose necessary for synovial ablation and pain palliation with minimum risk to the patient. ¹5³Sm-HM (370 MBq) was administered intra-articularly in a patient with severe knee pain and hindered motility. Regions of interest drawn on sequential, conjugated, anterior and posterior scintigraphy images were used to obtain the respective activity. The data was entered into a knee joint histological-geometric model designed with micrometric dimensions to represent the synovial cell layers. The Monte Carlo code was used to calculate the absorbed dose in each of the 12 model-cells representing the distance from the synovial liquid to the cartilage or bone. The absorbed dose in the synovial cavity was 114 Gy which is sufficient energy for RSV. The treated patient referred little pain and higher motility with no adverse reactions. ¹5³Sm-HM is a potentially valid radiopharmaceutical for RSV, which effectively palliates knee pain.

99mTc-N2S2-Tat (49-57)-bombesin internalized in nuclei of prostate and breast cancer cells: kinetics, dosimetry and effect on cellular proliferation.

BACKGROUND: The gastrin-releasing peptide receptor (GRP-r) is overexpressed in prostate and breast cancers. technetium-99m-bombesin (Tc-BN) has been reported as a radiopharmaceutical with specific cell GRP-r binding. The HIV Tat (49-57)-derived peptide has been used to deliver a large variety of molecules to cell nuclei. A new hybrid radiopharmaceutical of type Tc-N2S2-Tat(49-57)-Lys-BN (Tc-Tat-BN) internalized in cancer cell nuclei could act as an effective system of targeted radiotherapy using Auger and internal conversion electron emissions near DNA. AIM: The aim of this study was to assess the in-vitro nucleus internalization kinetics of Tc-Tat-BN in GRP r-positive cancer cells and to evaluate the subcellular-level radiation-absorbed dose associated with the observed effect on cancer cell DNA proliferation. METHODS: Tc-Tat-BN in-vitro internalization kinetics were evaluated in human prostate cancer PC-3 cells and breast carcinoma cell lines MCF7 and MDA-MB231. Nuclei from cells were isolated using a nuclear extraction kit. Total disintegration in each subcellular compartment was calculated by the integration of experimental time-activity kinetic curves. Nucleus internalization was corroborated by confocal microscopy images using immunofluorescently labelled Tat-BN. The PENELOPE code was used to simulate and calculate the absorbed dose by the contribution of Auger and internal conversion electrons in the cytoplasm and nucleus using geometric models built from immunofluorescent cell images. A cell proliferation kit was used to evaluate DNA concentration after cancer cell incubation with Tc-Tat-BN. RESULTS: The results showed that 59.7, 61.2 and 41.5% of total disintegration per unit of Tc-Tat-BN activity (1 Bq) bound to the cell occurred in the nucleus of PC-3, MCF7 and MDA-MB231, respectively. The Tc-Tat-BN absorbed doses delivered to nuclei were 0.142 mGy/decay (PC-3), 0.434 mGy/decay (MCF7) and 0.276 mGy/decay (MDA-MB231). Tc-Tat-BN produced a significant decrease in PC-3 (52.98%), MCF7 (45.71%) and MDA-MB231 (35.80%) cellular proliferation with respect to untreated cells. CONCLUSION: The hybrid radiopharmaceutical could be potentially useful as a therapeutic agent for prostate and breast cancers.

Clinical trial of specific imaging of infections.

OBJECTIVE: For several decades Ga citrate, technetium-99m ((99m)Tc) or (111)In-labelled leukocytes have been used for imaging the inflammatory process. Unfortunately, these radiopharmaceuticals are not infection-specific markers. In preclinical settings, radiolabelled antimicrobial peptides (AMPs), such as UBI 29-41 seem to be highly infection-specific and even high doses of these peptides have shown neither toxicity nor side effects in animals. METHODS: In this study we present data of a recent clinical trial carried out with the (99m)Tc labelled antimicrobial peptide UBI 29-41 ((99m)Tc-UBI 29-41) regarding its sensitivity, specificity, and accuracy in detecting various types of infections in 148 patients. The outcome of the trial with (99m)Tc-UBI 29-41 is compared with that of five other trials. RESULTS: Preparation of (99m)Tc-UBI 29-41 as a kit formulation is an easy, rapid, and reproducible process, and the tracer is very well tolerated by patients. The radiopharmaceutical has proven to be very stable and after injection into patients the biodistribution (renal clearance) and dosimetry seem to be favourable over other infection imaging radiopharmaceuticals. In this preliminary human study, patients with fever of unknown origin, osteomyelitis, diabetic foot, prosthesis infection, septic arthritis, or bacteraemia were successfully imaged with (99m)Tc-UBI 29-41 scintigraphy. CONCLUSION: (99m)Tc-UBI 29-41 is a promising agent for the specific detection of infections in humans because of its high sensitivity (96.3%), specificity (94.1%), and accuracy (95.3%) with high positive predictive (95.1%) and negative predictive values (95.5%).

Design, preparation, in vitro and in vivo evaluation of (99m)Tc-N2S2-Tat(49-57)-bombesin: a target-specific hybrid radiopharmaceutical.

The gastrin-releasing peptide receptor (GRP-r) is over-expressed in various human tumors. Recently, (99m)Tc-EDDA/HYNIC-Lys(3)-bombesin ((99m)Tc-BN) was reported as a radiopharmaceutical with specific cell GRP-r binding and images in breast cancer patients demonstrated distinct radioactivity accumulation in malignant tissue. The HIV Tat-derived peptide has been used to deliver a large variety of cargoes into cells. Therefore, a new hybrid radiopharmaceutical of type (99m)Tc-N(2)S(2)-Tat(49-57)-Lys(3)-bombesin ((99m)Tc-Tat-BN) would increase cell uptake. The aim of this research was to prepare and assess in vitro and in vivo uptake kinetics in cancer cells of (99m)Tc-Tat-BN and to compare its cellular internalization with that of (99m)Tc-BN. Structures of N(2)S(2)-Tat-BN and Tc(O)N(2)S(2)-Tat-BN were calculated by an MM procedure. (99m)Tc-Tat-BN was synthesized and stability studies carried out by HPLC and ITLC-SG analyses in serum and cysteine solutions. In vitro internalization was tested using human prostate cancer PC-3 cells and breast carcinoma cell lines MDA-MB231 and MCF7. Biodistribution was determined in PC-3 tumor-bearing nude mice. Results showed a minimum energy of 271 kcal/mol for N(2)S(2)-Tat-BN and 300 kcal/mol for Tc(O)N(2)S(2)-Tat-BN. (99m)Tc-Tat-BN radiochemical purity was >90%. In vitro studies demonstrated stability in serum and cysteine solutions, specific cell receptor binding and internalization in three cell lines was significantly higher than that of (99m)Tc-BN (p<0.05). The tumor-to-muscle radioactivity ratio was 8.5 for (99m)Tc-Tat-BN and 7 for (99m)Tc-BN. Therefore, this hybrid is potentially useful in breast and prostate cancer imaging.

Targeted imaging of gastrin-releasing peptide receptors with 99mTc-EDDA/HYNIC-[Lys3]-bombesin: biokinetics and dosimetry in women.

BACKGROUND: The gastrin-releasing peptide receptor (GRP-R) is expressed in several normal human tissues and is overexpressed in various human tumors including breast, prostate, small-cell lung cancer and pancreatic cancer. Recently, 99mTc-EDDA/HYNIC-[Lys]-bombesin (99mTc-HYNIC-BN) was reported as a radiopharmaceutical with high stability in human serum, specific cell GRP-R binding and rapid cell internalization. AIM: The aim of this study was to determine the biokinetics and dosimetry of 99mTc-HYNIC-BN and the feasibility of using this radiopharmaceutical to image GRP-R in four early breast cancer patients and seven healthy women. METHODS: Whole-body images were acquired at 20, 90, 180 min, and 24 h after 99mTc-HYNIC-BN administration. The same regions of interest were drawn around source organs on each time frame and regions of interest were converted to activity (conjugate view counting method). The image sequence was used to extrapolate 99mTc-HYNIC-BN time-activity curves in each organ to calculate the total number of disintegrations (N) that occurred in the source regions. N data were the input for the OLINDA/EXM code to calculate internal radiation dose estimates. RESULTS: 99mTc-HYNIC-BN had a rapid blood clearance with mainly renal excretion. No statistically significant differences (P>0.05) in the radiation-absorbed doses among cancer patients and healthy women were observed. The average equivalent doses (n=11) were 24.8+/-8.8 mSv (kidneys), 7.3+/-1.8 mSv (lungs), 6.5+/-4.0 mSv (breast), 2.0+/-0.3 mSv (pancreas), 1.6+/-0.3 mSv (liver), 1.2+/-0.2 mSv (ovaries), and 1.0+/-0.2 mSv (red marrow). The effective dose was 3.3+/-0.6 mSv. The images showed well-differentiated concentration of 99mTc-HYNIC-BN in cancer mammary tissue. CONCLUSION: All the absorbed doses were comparable with those known for most of the 99mTc studies. 99mTc-HYNIC-BN shows high tumor uptake in breasts with malignant tumors so it is a promising imaging radiopharmaceutical to target site-specific early breast cancer. The results obtained warrant a further clinical study to determine specificity/sensibility of 99mTc-HYNIC-BN.

Pharmacokinetics and dosimetry of 188 Re-pharmaceuticals.

The main objective of this review is to apportion current and new insight into the biodistribution, radiopharmacokinetics, dosimetry and cell targeting of rhenium-188 labeled radiopharmaceuticals used as therapeutic drugs. The emphasis lies on the generator obtained rhenium-188, its physical, therapeutic, dosimetric and coordinated compounds. Its use in radioimmunotherapy for lymphoma and other hematological diseases with monoclonal antibodies is discussed. Radiolabeled peptides to target cell receptors are an important field in nuclear medicine and in some research facilities are already being used, especially, somatostatin, bombesin and other peptides. Small molecules labeled with 188 Re are promising as therapeutic drugs. A review about some of the non-specific targeting molecules with therapeutic or pain palliation effect such as phosphonates, lipiodol, microparticles and other interesting molecules is included. Research on the labeling of biomolecules with the versatile rhenium-188 has contributed to the development of therapeutics with favorable pharmacokinetic and dosimetric properties for cancer treatment.

Biokinetics and dosimetry of 188Re-anti-CD20 in patients with non-Hodgkin's lymphoma: preliminary experience.

BACKGROUND: Radioimmunotherapy is a molecular targeting treatment for high-risk leukemia and lymphoma. Rhenium-188-labeled anti-CD66 monoclonal antibody has been used successfully in patients with high-risk acute myeloid leukemia or myelodysplastic syndrome. Our aim was to establish the biokinetics of (188)Re-anti-CD20 in patients and to evaluate its dosimetry as a target-specific radiopharmaceutical for non-Hodgkin's lymphoma (NHL) radioimmunotherapy. METHODS: Whole-body images were acquired at various times after administration of (188)Re-anti-CD20, obtained from instant freeze-dried kit formulations with radiochemical purity >95%. Regions of interest (ROIs) were drawn around source organs in each time frame. The cpm of each ROI was converted to activity using the conjugate view counting method. The image sequence was used to extrapolate time-activity curves in each organ to calculate the total number of disintegrations (N) that occurred in the source regions. N data were the input for the OLINDA/EXM code to calculate internal radiation dose estimates. RESULTS: Dosimetric studies indicated that after administration of 4.87-8.72 GBq of (188)Re-anti-CD20, the absorbed dose to total body would be 0.75 Gy, which corresponds with the recommended dose for NHL therapies. CONCLUSIONS: The calculated absorbed doses of (188)Re-anti-CD20 indicate that it may be used in radioimmunotherapy. Therefore, these preliminary data justify a full assessment of the safety, toxicity, and efficacy of (188)Re-anti-CD20 in a clinical study.

Preparation and evaluation of 99mTc-EDDA/HYNIC-[Lys 3]-bombesin for imaging gastrin-releasing peptide receptor-positive tumours.

BACKGROUND: Bombesin is a peptide that was initially isolated from frog skin and which belongs to a large group of neuropeptides with many biological functions. The human equivalent is gastrin-releasing peptide (GRP), whose receptors are over-expressed in a variety of malignant tumours. AIM: To prepare a HYNIC-[Lys 3]-bombesin analogue that could be easily labelled with 99mTc from lyophilized kit formulations and to evaluate its potential as an imaging agent for GRP receptor-positive tumours. METHODS: HYNIC was conjugated to the epsilon-amino group of Lys 3 residue at the N-terminal region of bombesin via succinimidyl-N-Boc-HYNIC at pH 9.0. 99mTc labelling was performed by addition of sodium pertechnetate solution and 0.2 M phosphate buffer pH 7.0 to a lyophilized formulation. Stability studies were carried out by reversed phase HPLC and ITLC-SG analyses in serum and cysteine solutions. In-vitro internalization was tested using human prostate cancer PC-3 cells with blocked and non-blocked receptors. Biodistribution and tumour uptake were determined in PC-3 tumour-bearing nude mice. RESULTS: 99mTc-EDDA/HYNIC-[Lys 3]-bombesin was obtained with radiochemical purities >93% and high specific activity ( approximately 0.1 GBq.nmol). Results of in-vitro studies demonstrated a high stability in serum and cysteine solutions, specific cell receptor binding and rapid internalization. Biodistribution data showed a rapid blood clearance, with predominantly renal excretion and specific binding towards GRP receptor-positive tissues such as pancreas and PC-3 tumours. CONCLUSION: 99mTc-EDDA/HYNIC-[Lys 3]-bombesin obtained from lyophilized kit formulations has promising characteristics for the diagnosis of malignant tumours that over-express the GRP receptor.

Biokinetics and dosimetry in patients of 99mTc-EDDA/HYNIC-Tyr3-octreotide prepared from lyophilized kits.

99mTc-EDDA/HYNIC-Tyr3-octreotide (99mTc-HYNIC-TOC) has shown high in vitro and in vivo stability, rapid background clearance and rapid detection of somatostatin receptor-positive tumors. The aim of this study was to establish a biokinetic model for 99mTc-HYNIC-TOC prepared from lyophilized kits, and to evaluate its dosimetry as a tumor imaging agent in patients with histologically confirmed neuroendocrine tumors. Whole-body images from eight patients were acquired at 5, 60, 90, 180 min and 24 h after 99mTc-HYNIC-TOC administration obtained from instant freeze-dried kit formulations with radiochemical purities >95%. Regions of interest (ROIs) were drawn around source organs on each time frame. The same set of ROIs was used for all eight scans and the count per minute (cpm) of each ROI was converted to activity using the conjugate view counting method. The image sequence was used to extrapolate 99mTc-HYNIC-TOC time-activity curves in each organ, to adjust a biokinetic model using the SAAM software, and to calculate the total number of disintegrations (N) that occurred in the source regions. N data were the input for the OLINDA/EXM code to calculate internal radiation dose estimates. Images showed an average tumor/blood (heart) ratio of 4.3+/-0.7 in receptor-positive tumors at 1 h. The mean radiation absorbed dose calculated for a study using 740 MBq was 24, 21.5, 5.5 and 1.0 mSv for spleen, kidneys, liver and bone marrow respectively and the effective dose was 4.4 mSv.

Bombesina y bombesinas radiomarcadas: estado actual / Bombesin and radiolabeled bombesin: current status

El péptido bombesina (BN), de 14 amino ácidos, se aisló de la piel de los batracios y forma parte de un amplio grupo de neuropéptidos con diversas funciones biológicas. El homólogo equivalente en los mamíferos es el péptido liberador de la gastrina (GRP) y sus receptores (GRP-r) se expresan abundantemente en la membrana de las células tumorales, estimulando su crecimiento. La unión BN-GRP-r es una fuerte unión altamente específica por lo cual la BN marcada con radionucleidos se ha utilizado en medicina nuclear para la localización de tumores malignos de cáncer de mama y próstata principalmente. Las modificaciones en la cadena peptídica y el marcado se llevan a cabo en la región de extremo-N inicial, quedando el extremo C-terminal con su especificidad y acción biológica intactas. Se presentan varios análogos de BN radiactivos y la estructura de uno nuevo formado por un conjugado EDDA/HYNIC-BBN que fácilmente se une al 99mTc. Las expectativas para utilizar radiofármacos de BN marcados con emisores beta-negativos en radiopéptidoterapia son grandes y prometedoras.

An efficient, reproducible and fast preparation of 188Re-anti-CD20 for the treatment of non-Hodgkin's lymphoma.

BACKGROUND: Therapies using Y-anti-CD20 or I-anti-CD20 have demonstrated their efficacy in patients with B-cell non-Hodgkin's lymphoma. Re is a radionuclide useful for radioimmunotherapy. AIM: To develop a procedure for efficient labelling of anti-CD20 with Re from lyophilized formulations to achieve high radiochemical yield, high specific activity and preservation of the molecular recognition after a simple kit reconstitution without further purification. METHODS: Re-anti-CD20 was prepared by a direct labelling method using sodium tartrate as a weak competing ligand. Different lyophilized formulations were prepared to optimize tartrate and stannous chloride concentration, pH and reaction time. To evaluate the biological recognition a comparative study of the in-vitro binding of Re-anti-CD20, I-anti-CD20 (positive control) and Re-anti-CEA (negative control) to normal B lymphocytes was performed. Biodistribution studies in normal mice were accomplished to assess the in-vivo Re-anti-CD20 complex stability. RESULTS: Re labelled anti-CD20 was obtained with high radiochemical purities (>97%) and high specific activity (0.5-0.7 GBq . mg) 1-1.5 h after addition of sodium perrhenate solution to a kit containing 4.4 muM anti-CD20, 4 mM anhydrous stannous chloride, and 140 mM dihydrate sodium tartrate at pH 4. The binding of Re-anti-CD20 to cells was in the same range as I-anti-CD20 (>80%) and was significantly different to cell binding of Re-anti-CEA (<10%). No evidence of free Re release was found at 2, 4 and 24 h after Re-anti-CD20 administration in mice. Lyophilized kits showed high stability during the storage at 4 degrees C for 6 months. CONCLUSIONS: Optimal reaction conditions were defined enabling high radiochemical purities of Re-anti-CD20 to be obtained routinely and therefore potentially useful in the treatment of non-Hodgkin's lymphoma.

Cytotoxic and genotoxic effect of the [166Dy]Dy/166Ho-EDTMP in vivo generator system in mice.

Multiple myeloma and other hematological malignancies have been treated by myeloablative radiotherapy/chemotherapy and subsequent stem cell transplantation. [(166)Dy]Dy/(166)Ho-ethylenediaminetetramethylene phosphonate (EDTMP) forms a stable in vivo generator system with selective skeletal uptake in mice; therefore, it could work as a potential and improved agent for marrow ablation. Induced bone marrow cytotoxicity and genotoxicity are determined by the reduction of reticulocytes (RET) and elevation of micronucleated reticulocyte (MN-RET) in peripheral blood and ablation by bone marrow histological studies. The aim of this study was to determine the bone marrow cytotoxic and genotoxic effect of the [(166)Dy]Dy/(166)Ho-EDTMP in vivo generator system in mice and to evaluate by histopathology its myeloablative potential. Enriched (166)Dy(2)O(3) was irradiated and [(166)Dy]DyCl(3) was added to EDTMP in phosphate buffer (pH 8.0) in a molar ratio of 1:1.75. QC was determined by TLC. Dy-EDTMP complex was prepared the same way with nonirradiated dysprosium oxide. A group of BALB/c mice were intraperitoneally injected with the radiopharmaceutical and two groups of control animals were injected with the cold complex and with 0.9% sodium chloride, respectively. A blood sample was taken at the beginning of the experiments and every 48 h for 12 days postinjection. The animals were sacrificed, organs of interest taken out and the radioactivity determined. The femur was used for histological studies. Flow cytometry analysis was used to quantify the frequency of RET and MN-RET in the blood samples. The MCNP4B Monte Carlo computer code was used for dosimetry calculations. Radiochemical purity was 99% and the mean specific activity was 1.3 MBq/mg. The RET and MN-RET frequency were statistically different in the treatment at the end of the 12-day period demonstrating cytotoxicity and genotoxicity induced by the in vivo generator system. The histology studies show that there was complete, or almost complete, acellularity, which means significant suppression of the bone marrow activity. Bone marrow absorbed dose was 18-23 Gy. [(166)Dy]Dy/(166)Ho-EDTMP induces cytotoxicity, genotoxicity and severe myelosuppression in mice. Potentially, it is a good agent for use in humans.

Biokinetics of (99m)Tc-UBI 29-41 in humans.

Antimicrobial peptides have been proposed as new agents to distinguish between bacterial infections and sterile inflammatory processes. (99m)Tc-UBI labeled by a direct method has shown high in vitro and in vivo stability, specific uptake at the site of infection, rapid background clearance, minimal accumulation in non-target tissues and rapid detection of infection sites in mice. The aim of this study was to establish a (99m)Tc-UBI biokinetic model and evaluate its feasibility as an infection imaging agent in humans. Whole-body images from 6 children with suspected bone infection were acquired at 1, 30, 120, 240 min and 24 h after (99m)Tc-UBI administration. Regions of interest (ROIs) were drawn around source organs (heart, liver, kidneys and bladder) on each time frame. The same set of ROIs was used for all 6 scans and the cpm of each ROI were converted to activity using the conjugate view counting method. Counts were corrected by physical decay and by the background correction factor derived from preclinical phantom studies. The image sequence was used to extrapolate (99m)Tc-UBI time-activity curves in each organ and calculate the cumulated activity (A). Urine samples were used to obtain the cumulative percent of injected activity (% I.A.) versus time renal elimination. The absorbed dose in organs was evaluated according to the general equation described in the MIRD formalism. In addition, (67)Ga-citrate images were obtained from all the patients and used as a control. Biokinetic data showed a fast blood clearance with a mean residence time of 0.52 h. Approximately 85% of the injected activity was eliminated by renal clearance 24 h after (99m)Tc-UBI administration. Images showed minimal accumulation in non-target tissues with an average target/non-target ratio of 2.18 +/- 0.74 in positive lesions at 2 h. All infection positive(99m)Tc-UBI images were in agreement with those obtained with (67)Ga-citrate. The mean radiation absorbed dose calculated was 0.13 mGy/MBq for kidneys and the effective dose was 4.34 x 10(-3)mSv/MBq.

In vitro and in vivo assessment of 99mTc-UBI specificity for bacteria.

Technetium-99m labeled ubiquicidin peptide 29-41 ((99m)Tc-UBI) is a cationic human antimicrobial peptide fragment that has been shown to bind bacteria in vitro and accumulates at sites of infection in experimental animals. To help determine if (99m)Tc-UBI is bound to the bacterial cell envelope by a simple nonspecific electrostatic interaction, a comparative study of the in vitro binding of (99m)Tc-UBI and two different (99m)Tc labeled cationic peptides ((99m)Tc-Tat-1-Scr and (99m)Tc-Tat-2-Scr) to bacteria and to two tumor cell line (LS174T and ACHN) was performed. The in vivo specificity of (99m)Tc-UBI for infection in mice was also evaluated using dual labels in the same animal and comparing the target/non-target ratio for (67)Ga-citrate and (99m)Tc-UBI at sites of induced infection and sterile inflammation. Under conditions of this study, the in vitro binding of (99m)Tc-UBI, (99m)Tc-Tat-1-Scr and (99m)Tc-Tat-2-Scr to S. aureus was 35, 78 and 87% respectively. While the binding of (99m)Tc-Tat-1-Scr and (99m)Tc-Tat-2-Scr was 37 and 33% to colon tumor cells (LS174T) and 39 and 41% to renal tumor cells (ACHN) respectively, the binding of (99m)Tc-UBI to both cell types was much lower at less than 4%. In vivo studies revealed that there is a significant difference (p < 0.05) in the radioactive accumulation of (99m)Tc-UBI between the sites of infection and inflammation compared to (67)Ga-citrate. Thus, (99m)Tc-UBI showed an average infection/inflammation ratio of 2.08 +/- 0.49 compared to 1.14 +/- 0.45 for (67)Ga-citrate. In conclusion, the in vitro and in vivo results provide evidence that a specific mechanism is responsible of the (99m)Tc-UBI bacterial intracellular accumulation.

Lys and Arg in UBI: a specific site for a stable Tc-99m complex?

The aim of this study was to help establish if ubiquicidin peptide 29-41 fragment (UBI) contains a specific site for 99mTc labeling by a new direct method under alkaline conditions. Since this peptide does not have cysteine residues, it is possible that neighboring arginine and lysine in the peptide amino acid sequence (Thr-Gly-Arg-Ala-Lys-Arg-Arg-Met-Gln-Tyr-Asn-Arg-Arg) could be a specific coordination site to form a stable 99mTc-UBI complex. Following direct labeling, the in vitro stability of 99mTc-UBI was compared to UBI radiolabeled by one indirect method using HYNIC/tricine and HYNIC/tricine/EDDA. Radiochemical purity of 99mTc-UBI averaged 97% compared to 88% for 99mTc-HYNIC-UBI/tricine and 98% for 99mTc-HYNIC-UBI/tricine/EDDA. Both 99mTc-HYNIC-UBI (tricine or EDDA) and 99mTc-UBI showed stability in human serum and solutions of cysteine. 99mTc-UBI radiochemical purity 24 h after dilution in 0.9% NaCl was greater than 90% at pH 9 and greater than 95% at pH 6.5. Under one set of experimental conditions, in vitro binding to bacteria of 99mTc-UBI was 35% and identical to that of 99mTc-HYNIC-UBI/tricine and 99mTc-HYNIC-UBI/tricine/EDDA at 32% and 31% respectively. The biodistribution of 99mTc-UBI in mice showed a rapid renal clearance. To help identify the site(s) of 99mTc binding following direct labeling, molecular mechanics and quantum-mechanical calculations were performed which showed that the amine groups of Arg(7) and Lys are the most probable site. The calculations show that these groups can form a square pyramid with two water molecules for the Tc cation (dxysp(3)). It will be necessary to isolate and characterize the 99Tc(V)(O)-UBI.(H2O)n complex to confirm these results.

Uptake of 153Sm-DTPA-bis-biotin and 99mTc-DTPA-bis-biotin in rat as-30D-hepatoma cells.

Labeled biotin has been used mainly for pretargeted therapy, an approach for increasing the amount of radioactivity delivered to a cancer cell. The aim of this investigation was to prepare (153)Sm-DTPA-bis-biotin and (99m)Tc-DTPA-bis-biotin in order to study their in vitro and in vivo uptake in rat AS-30D hepatoma cells found in ascites and in implanted tumor. DTPA-bis-biotin (pH 8) was (153)Sm labeled with (153)SmCl(3) and (99m)Tc-DTPA-bis-biotin was prepared via SnCl(2) reduction. Radiochemical purity was >98% in both cases. AS-30D hepatoma cells were obtained from ascites of a rat with hepatoma and were propagated in the peritoneum cavity of normal rats. In vitro ascites cell (153)Sm-DTPA-bis-biotin uptake was compared with (153)SmCl(3) cell uptake. The ratio cell (153)Sm-DTPA-bis-biotin/(153) SmCl(3) was 39.6 and when avidin was added it increased to 50. The ratio (99m)Tc-DTPA-bis-biotin/TcO(4)Na was 8.7. Concentration of (153)Sm-DTPA-bis-biotin in tumor 2, 3 and 24 h after administration, was 5, 15 and 3 times higher than in normal muscle (T/nT). Biodistribution in a 0.083-24 h time period showed that (153)Sm-DTPA-bis-biotin was taken up only by ascites tumor cells and hepatoma cells. Two and 3 h ratio ascites/liver (As/Lv) was 6.4 and 6.0. For (99m)Tc-DTPA-bis-biotin 2 and 3 h T/nT was 15.7 and 4.7 and 2 h As/Lv was 1.4. In conclusion, both radiopharmaceuticals show high uptake in rat AS-30D hepatoma cells in ascites and in implanted tumor. Since lung, thyroid, kidney, liver or pancreas carcinomas are ascites producing cancers (153)Sm-DTPA-bis-biotin would be an adequate therapeutic radiopharmaceutical for these patients whose life quality would be enhanced with control of ascites, and a reduction of the primary tumor and its metastases.

Estudios radiofarmacocinéticos y gammagráficos para cálculos de dosimetría personalizada / Radiopharmacokinetic and scanning studies for estimating personalized internal dosimetry

La dosis absorbida determina el riesgo/beneficio que recibe el paciente a quien se le administra un radiofármaco y se calcula con modelos biológicos y matemáticos. El biológico relaciona los datos experimentales de sangre y orina para obtener la actividad acumulada y el valor del tiempo de residencia promedio t. Con el modelo matemático MIRD, se obtiene, a partir de t, el cálculo de la dosis absorbida utilizando el programa de computación MIRDOSE3.En la Unidad de Radiofarmacia del Departamento de Medicina Nuclear del INCMNSZ se desarrollaron, caracterizaron y probaron en animales dos radiofármacos osteotrópicos originales: 99mTc-ABP y 188Re-ABP. Además, con el primero se obtuvieron valores radiofarmacocinéticos, en 10 sujetos normales, por medio de muestras seriadas de sangre y orina durante 24 h y por medio de regiones de interés (RDI) trazadas sobre gammagramas óseos seriados. Los valores obtenidos para por ciento de eliminación en orina y por ciento de captación en hueso se utilizaron para el cálculo de la dosis absorbida con 99mTc-ABP y para el cálculo extrapolado con 188Re-ABP como fundamento para calcular la actividad a usar en el tratamiento terapéutico.El 99mTc-ABP se eliminó por orina para mujeres 63.2 ñ 7.3 por ciento de la actividad administrada en 24 h y para hombres 70 ñ 11 por ciento. La actividad remanente en hueso fue para mujeres 36.8 ñ 7.3 por ciento y para hombres 30 ñ 11 por ciento. Se delimitaron RDIs sobre las imágenes gammagráficas y al integrar las cpm/pixel/RDI sobre riñón en función del tiempo se obtuvo el tiempo de residencia t = 0.52 h. Con la ecuación =1.443 (T½) A0 se calculó la actividad acumulada en hueso 2358 ñ 469 MBq h en mujeres y 1923 ñ 707 MBq h para hombres; t = 3.19 ñ 0.63 h (mujeres) y 2.6 ñ 0.95 h en hueso para los hombres. La dosis absorbida para cuerpo entero en mujeres fue 0.0020 ñ 0.0004 mGy/MBq y 0.0013 ñ 0.0005 mGy/MBq para los hombres. La dosis absorbida en médula ósea fue 0.0063 ñ 0.0013 mGy/MBq en las mujeres y 0.0041 ñ 0.0015 mGy/MBq en hombres. El 188Re es un emisor de radiaciones beta negativa y considerando que el 188Re-ABP se comporta igual al radiofármaco de tecnecio-99m, la dosis efectiva a las mujeres sería 0.0936 mSv/MBq y 0.0608 mSv/MBq para los hombres. Estas características y las características radionuclídicas del 188Re serían las apropiadas para utilizar 188Re-ABP como un buen agente paliativo del dolor producido por las metástasis óseas.

Radiopharmacokinetics, renal clearance and dosimetry of 99m Tc-MAG3

Background. Technetium-99m-mercaptoacetyltriglycine (99-mTc-MAG3) is a radiopharmaceutical for tubular function and can be prepared with 99-mtechnetium and the ligand Bz-MAG3 (Instituto Nacional de Investigaciones Nucleares, Mexico City). No radiopharmacokinetic parameters have been found for the healty adult Mexican population with 99mTc-MAG3, prepared with the nationally produced or imported Bz-MAG3 kit. Methods. The radiopharmacokinetic parametrs and the clearance of 99mTc-Mag3 in seven healthy Mexican volunteers were determined by the single-and multi-sample methods. Computer programs were used for the calculations. Results. Using several plasma samples from 0.43 min and the BIEXP program, it was show that 99mTc-MAG3 follows a two-compartment model of distribution, with an apparent volumen in the central compartment Vdcc = 6.7 + 1.0 1, T½Ó = 0.07 + 0.02 h-1, T½ ß = 0.49 + 0.15 h-1, mean residence time MRT = 0.60 + 0.17 h and clearance = 208 57 (ml/min)/1.73 m². In comparison, the clearance value with a single sample drawn 43 min post-injection and calculated with Tauxe's formula was 193 ñ 59 (ml/min)/m². Conclusions. The 15 ml difference between the two methods is neither statistically different (p= 0.11) nor important for routine clinical studies. The single-sample method is recommendad because it is reliable and can be done at the same time that dynamic renal scan is aquiered. Estimated absorbed radiation dose was calvulated for several organs

El 99mTc-alendronato como nueva opción en la gammagrafía ósea / 99mTc-Alendronate as an option in bone scanning

Objetivo. Comparar la calidad de las imágenes de gammagrafía ósea obtenidas con un radiofármaco nuevo, el 99mTc-ABP, con aquéllas obtenidas con el 99mTc-MDP. Material y métodos. Fue un estudio comparativo en un mismo sujeto. Se estudiaron 9 voluntarios sanos (5 mujeres y 4 hombres) de 23 a 39 años de edad. A todos se les inyectaron 740 MBq de los radiofármacos Tc-ABP y Tc-MDP con un intervalo de 72 horas entre uno y otro. Dos horas después de cada inyección se les realizó un gammagrama óseo de cuerpo entero con una cámara de centello MultiSpect 2 y se determinaron los parámetros radiofarmacocinéticos. Tres médicos nucleares evaluaron por separado la calidad de las imágenes mediante el trazado de regiones de interés (RDI) sobre vértebras, costillas, esternón, fémur, articulaciones y cráneo. Se obtuvieron relaciones hueso/músculo con RDI sobre diferentes huesos. Los resultados se compararon etadísticamente con las pruebas de kappa y de Wilcoxon. Resultados. La concordancia sobre la calidad de las imágenes de los dos radiofármacos por los tres observadores fue moderada (kappa 0.4). La relación fémur/músculo mostró una distribución normal y no manifestó diferencias significativas entre radiofármacos. Conclusiones. La calidad de las imágenes con ambas preparaciones fue similar. Recomendamos utilizar al 99mTc-ABP en la gammagrafía ósea debido a la menor exposición a radiación del paciente