A 89Zr-labeled lipoplex nanosystem for image-guided gene delivery: design, evaluation of stability and in vivo behavior.

BACKGROUND: With the advances in radiopharmaceutical research, the development of image-guided therapy has become a major interest. While the development of theranostic nanotherapeutics is frequently associated with cancer chemotherapy, phototherapy and radiotherapy, there is little information available on the in vivo monitoring of gene delivery systems and the application of image-guided approach in gene therapy. The goal of this work was to determine the in vivo behavior of DNA delivery nanosystems - based on cationic gemini surfactants - designed for image-guided gene therapy. We tested the feasibility of monitoring tumor accumulation of gene delivery nanoparticles by positron emission tomography. METHODS: To be able to conjugate radiotracers to the nanoparticles, a deferoxamine-modified gemini surfactant was synthesized, DNA-containing lipoplex nanoparticles were formulated, and radiolabeled with Zirconium-89 (89Zr). The pharmacokinetics and biodistribution of 89Zr labeled surfactant and 89Zr labeled nanoparticles were monitored in mice by microPET/CT imaging and ex vivo gamma counting. RESULTS: Modification of the nanoparticles with deferoxamine did not alter their physicochemical properties. The radiolabeled nanoparticles (labeling efficiency of 95±3%) were stable in PBS and serum. The biological half-life of the 89Zr labeled nanoparticles was significantly higher compared to 89Zr labeled surfactant. As expected, the nanoparticles had significantly higher liver accumulation than the radiolabeled surfactant alone and lower kidney accumulation. Tumor uptake was detected at 2 hours post injection and decreased throughout the 3-day monitoring. CONCLUSION: We propose that radiolabeling DNA delivery lipoplex nanosystems is a promising approach for the design and optimization of image-guided nanomedicines, especially in the context of cancer gene therapy.

Pharmacokinetics of single dose radium-223 dichloride (BAY 88-8223) in Japanese patients with castration-resistant prostate cancer and bone metastases.

OBJECTIVE: This open-label, non-randomized, phase I study examined the pharmacokinetics (PK) and radiation dosimetry of a single dose of radium-223 in Japanese patients with castration-resistant prostate cancer (CRPC) and bone metastases. METHODS: Six male Japanese patients (mean age 72.5 years, range 65-79 years) with histologically or cytologically confirmed stage IV adenocarcinoma of the prostate were recruited. A single IV dose of radium-223 was delivered intravenously (IV) via slow bolus over a 2-5 min period: Cohort 1 received 50 kBq/kg and Cohort 2 received 100 kBq/kg. RESULTS: Following IV injection, radium-223 was rapidly eliminated from the blood in a multi-phasic manner. The fraction of the injected activity of radium-223 retained in the whole body 24 h following injection was 85 %. Biodistribution results showed initial bone uptake was 52 % (range 41-57 %). The maximum activity of radium-223 in the bone was observed within 2 h of dosing. Activity of radium-223 passed through the small intestine within 24 h. No activity was detected in other organs. The major radiation dose from radium-223 was found in osteogenic cells; calculated absorbed doses in osteogenic cells and in the red marrow were 0.76 Gy/MBq and 0.09 Gy/MBq, respectively. CONCLUSIONS: In Japanese patients with CRPC and bone metastases, radium-223 (IV) achieved maximum activity in the bone rapidly and passed through the intestine within 24 h, without signs of activity in other organs. The PK profile and absorbed radiation dose in organs and tissues in Japanese patients were similar to data from non-Japanese patients. Trial registration identification: NCT01565746.

An investigation into the upward transport of uranium-series radionuclides in soils and uptake by plants.

The upward migration of radionuclides in the (238)U decay series in soils and their uptake by plants is of interest in various contexts, including the geological disposal of radioactive waste and the remediation of former sites of uranium mining and milling. In order to investigate the likely patterns of behaviour of (238)U-series radionuclides being transported upward through the soil column, a detailed soil-plant model originally developed for studying the behaviour of (79)Se in soil-plant systems has been adapted to make it applicable to the (238)U series. By undertaking a reference case simulation and a series of sensitivity studies, it has been found that a wide variety of behaviour can be exhibited by radionuclides in the (238)U decay chain in soils, even when the source term is limited to being a constant flux of either (238)U or (226)Ra. Hydrological conditions are a primary factor, both in respect of the overall advective flow deeper in the soil, which controls the rate of upward migration, and in the influence of seasonally changing flow directions closer to the soil surface, which can result in the accumulation of radionuclides at specific depths irrespective of changes in sorption between the oxic and anoxic regions of the soil. However, such changes in sorption can also be significant in controlling the degree of accumulation that occurs. This importance of seasonally varying factors in controlling radionuclide transport in soils even in very long-term simulations is a strong argument against the use of annually averaged parameters in long-term assessment models. With a water table that was simulated to fluctuate seasonally from a substantial depth in soil to the surface soil layer, the timing of such variations in relation to the period of plant growth was found to have a major impact on the degree of uptake of radionuclides by plant roots. In long-term safety assessment studies it has sometimes been the practice to model the transport of (226)Ra in soil, but to assume that both (210)Pb and (210)Po can be treated as being present in secular equilibrium with the (226)Ra. This simplification is not always appropriate. Where geochemical conditions are such that the (226)Ra migrates upward in the soil column faster than (210)Pb and (210)Po, disequilibrium is not a significant issue, as the (226)Ra supports (210)Pb and (210)Po at concentrations somewhat below those estimated on the basis of assumed secular equilibrium. However, for low, but realistic, values of the distribution coefficients for (210)Pb and (210)Po and high, but realistic, distribution coefficients for (226)Ra, the (210)Pb and (210)Po can reach the surface soil in high concentrations that are not locally supported by (226)Ra. This means that models based on the assumption of secular equilibrium should not be employed without a careful consideration of the hydrological and hydrochemical situation of interest.

Radium Ra 223 dichloride in castration-resistant prostate cancer.

Radium Ra 223 dichloride (Xofigo®, formerly Alpharadin) is one of the representative α-particle-emitting isotopes that delivers radiation with a higher biological effect to a more localized area. Preclinical studies in mouse, rat and canine models have demonstrated that radium Ra 223 dichloride has a definite skeletal affinity and antitumor effect with a relatively low toxicity on bone marrow. More recently, in a large randomized phase III trial (ALSYMPCA), patients with bone metastasis and castration-resistant prostate cancer (CRPC) received six cycles of 50 kBq/kg of radium Ra 223 dichloride in 4-week intervals. In these men, radium Ra 223 dichloride improved the median overall survival by 3.6 months when compared to the placebo group. Collectively, these results suggest that radium Ra 223 dichloride is a promising candidate for managing bone metastases in patients with CRPC.

Toxicity of irradiated advanced heavy water reactor fuels.

The good neutron economy and online refueling capability of the CANDU® heavy water moderated reactor (HWR) enable it to use many different fuels such as low enriched uranium (LEU), plutonium, or thorium, in addition to its traditional natural uranium (NU) fuel. The toxicity and radiological protection methods for these proposed fuels, unlike those for NU, are not well established. This study uses software to compare the fuel composition and toxicity of irradiated NU fuel against those of two irradiated advanced HWR fuel bundles as a function of post-irradiation time. The first bundle investigated is a CANFLEX® low void reactor fuel (LVRF), of which only the dysprosium-poisoned central element, and not the outer 42 LEU elements, is specifically analyzed. The second bundle investigated is a heterogeneous high-burnup (LEU,Th)O(2) fuelled bundle, whose two components (LEU in the outer 35 elements and thorium in the central eight elements) are analyzed separately. The LVRF central element was estimated to have a much lower toxicity than that of NU at all times after shutdown. Both the high burnup LEU and the thorium fuel had similar toxicity to NU at shutdown, but due to the creation of such inhalation hazards as (238)Pu, (240)Pu, (242)Am, (242)Cm, and (244)Cm (in high burnup LEU), and (232)U and (228)Th (in irradiated thorium), the toxicity of these fuels was almost double that of irradiated NU after 2,700 d of cooling. New urine bioassay methods for higher actinoids and the analysis of thorium in fecal samples are recommended to assess the internal dose from these two fuels.

Dosimetric calculations for uranium miners for epidemiological studies.

Epidemiological studies on uranium miners are being carried out to quantify the risk of cancer based on organ dose calculations. Mathematical models have been applied to calculate the annual absorbed doses to regions of the lung, red bone marrow, liver, kidney and stomach for each individual miner arising from exposure to radon gas, radon progeny and long-lived radionuclides (LLR) present in the uranium ore dust and to external gamma radiation. The methodology and dosimetric models used to calculate these organ doses are described and the resulting doses for unit exposure to each source (radon gas, radon progeny and LLR) are presented. The results of dosimetric calculations for a typical German miner are also given. For this miner, the absorbed dose to the central regions of the lung is dominated by the dose arising from exposure to radon progeny, whereas the absorbed dose to the red bone marrow is dominated by the external gamma dose. The uncertainties in the absorbed dose to regions of the lung arising from unit exposure to radon progeny are also discussed. These dose estimates are being used in epidemiological studies of cancer in uranium miners.

Pharmacokinetic, tissue distribution and excretion of ginsenoside-Rd in rodents.

Ginsenoside-Rd (GS-Rd) is one of the major active components of Panax ginseng, and was shown to have the protective effects against several insults. However, we still lack some basic knowledge of GS-Rd, including its pharmacokinetic, tissue distribution and excretion in vivo in experimental animal, such as mice and rats. In this study, HPLC and radioactive tracer assays were performed to determine pharmacokinetic, tissue distribution and excretion of GS-Rd in rodents. After intravascular administration with 20, 50 or 150 mg/kg GS-Rd, the dynamic changes of GS-Rd concentrations in plasma were consistent with a two-compartment model while the concentration of ³H-labeled GS-Rd was rapidly reached the peak in plasma, and distributed to various tissues, among which the highest concentration was observed in the lung.

Continuing pursuit for ideal systemic anticancer radiotherapeutics.

Cancer is one of the major causes of death for non-transmissible chronic diseases worldwide. Conventional treatments including surgery, chemotherapy and external beam radiotherapy are generally far from curative. Complementary therapies are attempted for achieving more successful treatment response. Systemic targeted radiotherapy (STR) is a radiotherapeutic modality based on systemic administration of radioactive agents for selectively delivering high doses of energy to destroy cancer cells. For this purpose, diverse tumour-target specific agents including monoclonal antibodies (MoAb), MoAb fragments and peptides have been tested and some of them have already got FDA approval for clinical use. However, MoAbs and their tailored analogues have shown non-homogeneous tumour distribution, limited diffusion, insufficient intratumoral accumulation and retention, unwanted uptake in normal tissues and scarcity of identified cancer antigens for generating new MoAbs. Similarly, peptides have also exhibited retention in normal organs, lacks of favourable membrane permeability or drug cell internalization and short-term residence in cancer cells. Recently, a new category of target-specific agent with strong affinity for necrosis has emerged as an excellent option for developing targeted radiotherapeutic agents to be used after necrosis-inducing treatments (NITs). The combination of their high, specific and long-term accumulation and retention at necrotic sites with the crossfire effect of ionizing particle-emitters allows irradiating adjacent residual viable tumour cells during a prolonged period of time. It may considerably enhance the therapeutic response and open a new horizon for improved cancer treatability or curability.

Preparation and biodistribution of 188Re-labeled folate conjugated human serum albumin magnetic cisplatin nanoparticles (188Re-folate-CDDP/HSA MNPs) in vivo.

BACKGROUND: The purpose of this study was to develop intraperitoneal hyperthermic therapy based on magnetic fluid hyperthermia, nanoparticle-wrapped cisplatin chemotherapy, and magnetic particles of albumin. In addition, to combine the multiple-killing effects of hyperthermal targeting therapy, chemotherapy, and radiotherapy, the albumin-nanoparticle surfaces were linked with radionuclide (188)Re-labeled folic acid ligand ((188)Re-folate-CDDP/HSA). METHODS: Human serum albumin was labeled with (188)Re using the pre-tin method. Reaction time and optimal conditions of labeling were investigated. The particles were intravenously injected into mice, which were sacrificed at different time points. Radioactivity per gram of tissue of percent injected dose (% ID/g) was measured in vital organs. The biodistribution of (188)Re-folate-CDDP/HAS magnetic nanoparticles was assessed. RESULTS: Optimal conditions for (188)Re-labeled folate-conjugated albumin combined with cisplatin magnetic nanoparticles were: 0.1 mL of sodium gluconate solution (0.3 mol/L), 0.1 mL of concentrated hydrochloric acid with dissolved stannous chloride (10 mg/mL), 0.04 mL of acetic acid buffer solution (pH 5, 0.2 mol/L), 30 mg of folate-conjugated albumin combined with cisplatin magnetic nanoparticles, and (188)ReO(4) eluent (0.1 mL). The rate of (188)Re-folate-CDDP-HSA magnetic nanoparticle formation exceeded 90%, and radiochemical purity exceeded 95%. The overall labeling rate was 83% in calf serum at 37°C. The major uptake tissues were the liver, kidney, intestine, and tumor after the (188)Re-folate-CDDP/HSA magnetic nanoparticles were injected into nude mice. Uptake of (188)Re-folate-CDDP/HSA magnetic nanoparticles increased gradually after injection, peaked at 8 hours with a value of 8.83 ± 1.71, and slowly decreased over 24 hours in vivo. CONCLUSION: These results indicate that (188)Re-folate-CDDP/HSA magnetic nanoparticles can be used in radionuclide-targeted cancer therapy. Surface-modified albumin nanoparticles with folic acid ligand-labeled radionuclide ((188)Re) were successfully prepared, laying the foundation for a triple-killing effect of thermotherapy, chemotherapy, and radiation therapy.

Preclinical animal research on therapy dosimetry with dual isotopes.

Preclinical research into radionuclide therapies based on radiation dosimetry will enable the use of any LET-equivalent radionuclide. Radiation dose and dose rate have significant influence on dose effects in the tumour depending on its radiation sensitivity, possibilities for repair of sublethal damage, and repopulation during or after the therapy. Models for radiation response of preclinical tumour models after peptide receptor radionuclide therapy based on the linear quadratic model are presented. The accuracy of the radiation dose is very important for observation of dose-effects. Uncertainties in the radiation dose estimation arise from incomplete assay of the kinetics, low accuracy in volume measurements and absorbed dose S-values for stylized models instead of the actual animal geometry. Normal dose uncertainties in the order of 20% might easily make the difference between seeing a dose-effect or missing it altogether. This is true for the theoretical case of a homogeneous tumour type behaving in vivo in the same way as its cells do in vitro. Heterogeneity of tumours induces variations in clonogenic cell density, radiation sensitivity, repopulation capacity and repair kinetics. The influence of these aspects are analysed within the linear quadratic model for tumour response to radionuclide therapy. Preclinical tumour models tend to be less heterogenic than the clinical conditions they should represent. The results of various preclinical radionuclide therapy experiments for peptide receptor radionuclide therapy are compared to the outcome of theoretical models and the influence of increased heterogeneity is analysed when the results of preclinical research is transferred to the clinic. When the radiation dose and radiobiology of the tumour response is known well enough it may be possible to leave the current phenomenological approach in preclinical radionuclide therapy and start basing these experiments on radiation dose. Then the use of a gamma ray-emitting radionuclides for a chemically comparable beta-particle-emitting paired isotope for therapy evaluation would be feasible.

Preparation and pre-clinical study of 177Lu-labelled hydroxyapatite for application in radiation synovectomy of small joints.

AIM: We present in this paper, the preparation and pre-clinical study of 177Lu-labelled hydroxyapatite for the application in radiation synovectomy of small sized joints. METHODS: 177Lu is an adequate radionuclide for therapy, having ability of simultaneously showing therapeutic effects and depicting images. Both hydroxyapatite particulates and 177Lu were prepared indigenously. RESULTS AND CONCLUSION: Analysis of the gamma ray spectrum showed the radionuclide purity of 177Lu more than 99%. HA particles were synthesized and characterized by FTIR-ATR and X-ray diffractometry. XRD-Pattern generated by the product indicated that the chief inorganic phase of the sample is hydroxyapatite crystal. FTIR spectrum of HA powder calcined at 800°C for 1h showed all the bands that can be assigned to phosphate and hydroxyl groups in an apatite environment. Ca/P ratio was determined by ICP-OES. The Ca/P ratio of 1.68 determined for HA was about 0.6% above the stoichiometric ratio of 1.67. Particle size distribution pattern was obtained with the help of laser particle size analyzer and results showed that more than 80% of the particles bear the size in the range ideal for radiosynovectomy. 177Lu-labelled hydroxyapatite particulates were prepared with high radiochemical purity and yield. >95% labeling yield was achieved at pH 7. Labeled specie remained stable up to 18 days. In vitro stability >99% remained up to >one half life of 177Lu. Bio-evaluation of the 177Lu-HA particles was carried out by injecting approximate activities of 10 and 5 MBq (in 0.1 mL suspension) as intra-articular injection in the right knee joints of rabbit 1 and 2 respectively. Retention of activity was studied using images of the injected joints with the help of a gamma camera at various intervals. In all images no activity was visible in any organ other than knee joints. The retention of the 177Lu activity was followed for 772 hours (30.01 days). Leakage of activity was also assessed indirectly by estimating the residing time of radiopharmaceutical in the synovium. Half life of 177Lu-HA residing time in the knees was estimated to be 154 hours and 158 hours for rabbit-1 and rabbit-2 respectively. No significant extra articular leakage of the injected activity was observed over a period of one month post injection. Pre-clinical study of 177Lu-labelled hydroxyapatite indicated its potential for application in radiation synovectomy of small joints.

Preparation of 177Lu-labeled oxine in lipiodol as a possible agent for therapy of hepatocellular carcinoma: a preliminary animal study.

Hepatocellular carcinoma (HCC) is one of the most prevalent forms of cancer with high morbidity. (131)I-lipiodol is used clinically and has been found to be effective for the treatment of HCC. However, this preparation has its limitations, including compromised yield and stability of exchange labeling and unnecessary dose burden from gamma emissions. In the present study, (177)Lu-oxine in lipiodol was considered as a possible alternative for radioiodinated lipiodol. Oxine or 8-hydroxyquinoline was labeled with (177)Lu obtained by neutron irradiation of natural lutetium. Under optimized conditions, the radiolabeled complex was obtained with yields >98% and adequate in vitro stability. (177)Lu-oxine dispersed in lipiodol showed appreciable uptake into rat liver cells (normal and HCC-induced) in vitro. (177)Lu-oxine-lipiodol showed initial localization in the liver, but subsequent leakage of radioactivity with deposition in the skeletal tissue was seen. The studies suggest that (177)Lu-oxine dispersed in lipiodol might not be suitable for treatment of HCC.

Ensayos in-vitro e in-vivo del péptido marcado 177Lu-DOTA-Sustancia P y evaluación de los cálculos dosimétricos en la etapa preclínica / Tests in-vitro and in vivo of 177Lu-DOTA-SP labeled peptide and evaluation of the dosimetric calculations in the preclinical stage

Introducción: El péptido Sustancia P (SP) es el ligando principal de los receptores de neurokininas tipo 1, los cuales se encuentran sobreexpresados en los gliomas malignos. Método: Se obtuvo 177Lu-DOTA-SP con elevada pureza radioquímica. Se realizaron biodistribuciones en ratones normales a diferentes tiempos. Se calcularon las dosis absorbidas para los diferentes órganos del ratón (cGy/uCi). Utilizando los métodos de escalación por tiempo (A) y extrapolación directa (B), se obtuvieron las dosis en los diferentes órganos humanos. Se calcularon las máximas dosis tolerables en función de los órganos críticos (mCi/kg). Resultados: La máxima actividad tolerable que puede ser inyectada sin producir toxicidad en riñones es 11,2 mCi/kg (hombre adulto) y 11,4 mCi/kg (mujer adulta) según el método A y de 47,2 mCi/kg y 56,2 mCi/kg, respectivamente según el método B. Conclusiones: Hasta el momento se pudo obtener 177Lu-DOTA-SP con Ae= 0,05mCi/ ug de péptido. La misma puede aumentarse utilizando el 177LuCl3 de mayor actividad específica.

Introduction: Substance P (SP) is the main ligand of neurokin type 1 receptors, which are consistently overexpressed in malignant gliomas. Method: 177Lu-DOTA-SP was obtained with high radiochemical purity. Biodistribution in normal mice at different times, were done. Absorbed doses were calculated for different mice organs (cGy/uCi). Absorbed doses in human organs were calculated using two different methods, time scaling (A) and data extrapolation (B). Maximum tolerated doses were calculated according to critical organs (mCi/kg). Results: Maximum tolerated dose that can be injected without kidney toxicity is 11,2 mCi/kg (adult man) and 11,4 mCi/kg (adult woman) according to method A and 47,2 mCi/kg, 56,2 mCi/kg, respectively according to method B. Conclusion: So far, 177Lu-DOTA-SP was achieved with a specific activity (S.a) of 0,05 mCi/ ug of peptide. This S.a can be increased using 177LuCl3 of higher specific activity.

Radioimmunotherapy prevents local recurrence of colonic cancer in an experimental model.

BACKGROUND: Radioimmunotherapy (RIT) is suitable for the treatment of microscopic residual disease and might therefore have an adjuvant role after colonic cancer surgery. METHODS: An anastomosis was constructed in male Wag/Rij rats after intraluminal injection of 2 x 10(6) CC531 tumour cells. The biodistribution of (111)In-labelled MG1 monoclonal antibody was assessed after intraperitoneal administration. The therapeutic efficacy of (177)Lu-labelled MG1 (74 MBq per rat), administered on the day of surgery (D0, n = 13) or 5 days later (D5, n = 13), was compared with that of carrier only (n = 13). The primary endpoint was perianastomotic tumour growth 28 days after surgery. RESULTS: (111)In-labelled MG1 preferentially accumulated in perianastomotic CC531 tumours. RIT resulted in a transient reduction in bodyweight in both treatment groups compared with controls, but there were no other signs of clinical discomfort. No macroscopic or microscopic perianastomotic tumour growth was found in eight of 11 animals in the D0 group and 11 of 13 in the D5 group, whereas 11 of 13 controls had macroscopic tumour (P = 0.011 and P = 0.001 respectively). CONCLUSION: This study suggests that RIT may be an effective adjuvant treatment for preventing local recurrence after resection of colonic cancer.

Aluminum bioavailability from tea infusion.

The objective was to estimate oral Al bioavailability from tea infusion in the rat, using the tracer (26)Al. (26)Al citrate was injected into tea leaves. An infusion was prepared from the dried leaves and given intra-gastrically to rats which received concurrent intravenous (27)Al infusion. Oral Al bioavailability (F) was calculated from the area under the (26)Al, compared to (27)Al, serum concentration x time curves. Bioavailability from tea averaged 0.37%; not significantly different from water (F=0.3%), or basic sodium aluminum phosphate (SALP) in cheese (F=0.1-0.3%), but greater than acidic SALP in a biscuit (F=0.1%). Time to maximum serum (26)Al concentration was 1.25, 1.5, 8 and 4.8h, respectively. These results of oral Al bioavailability x daily consumption by the human suggest tea can provide a significant amount of the Al that reaches systemic circulation. This can allow distribution to its target organs of toxicity, the central nervous, skeletal and hematopoietic systems. Further testing of the hypothesis that Al contributes to Alzheimer's disease may be more warranted with studies focusing on total average daily food intake, including tea and other foods containing appreciable Al, than drinking water.

Enteric oxalate secretion is not directly mediated by the human CFTR chloride channel.

The secretion of the oxalate anion by intestinal epithelia is a functionally significant component of oxalate homeostasis and hence a relevant factor in the etiology and management of calcium oxalate urolithiasis. To test the hypothesis that human cystic fibrosis transmembrane conductance regulator (hCFTR) can directly mediate the efflux of the oxalate anion, we compared cAMP-stimulated 36Cl-, 14C-oxalate, and 35SO(4)2- efflux from Xenopus oocytes expressing hCFTR with water-injected control oocytes. hCFTR-expressing oocytes exhibited a large, reversible cAMP-dependent increase in whole cell conductance measured using a two-electrode voltage clamp and a 13-fold increase in rate of cAMP-stimulated 36Cl- efflux. In contrast, the rate constants of oxalate and sulfate efflux were low and unaffected by cAMP in either control or hCFTR-expressing oocytes. We conclude that the human CFTR gene product does not directly mediate oxalate efflux in secretory epithelia and hence is not directly involved in oxalate homeostasis in humans.

Patient-specific radiation dosimetry for radionuclide therapy of liver tumors with intrahepatic artery rhenium-188 lipiodol.

A clinically practical algorithm has been developed for the treatment of liver cancer by the administration of rhenium-188 ((188)Re)-labeled lipiodol via the hepatic artery. This algorithm is based on the "maximum tolerated-activity" paradigm for radionuclide therapy. A small "scout" activity of (188)Re-labeled lipiodol is administered to the patient before the actual therapeutic administration. At approximately 3 hours after administration, the activities in the normal liver, liver tumors, lungs, and total body are measured by gamma camera imaging using the conjugate-view method, with first-order corrections for attenuation (using a (188)Re transmission scan) and scatter (using the "dual-window" method). At the same time, peripheral blood samples are counted, and the activity concentrations in whole blood are calculated. The blood activity concentrations are then converted to red marrow activity concentrations and then total red marrow activity using anatomic data from Standard Man anthropomorphic models. Next, the cumulated activities in the normal liver, liver tumors, lungs, red marrow, and total body are calculated using the measured activities in the respective source regions and conservatively assuming elimination of activity only by physical decay in situ. The absorbed doses to the therapy-limiting normal tissues, liver, lung, and red marrow, are then calculated using the Medical Internal Radiation Dose Committee schema, adjusting the pertinent S factors for differences in total body and organ masses between the patient and the anthropomorphic model and including the dose contribution from the liver tumors. Finally, based on maximum tolerated absorbed doses of 3,000, 1,200, and 150 rad (cGy) to liver, lung, and red marrow, the respective absorbed doses per unit administered activity are used to calculate the therapy activity. Although not required for treatment planning, tumor absorbed dose may also be estimated. This algorithm has been automated using an Excel (Microsoft, Redmond, WA) spreadsheet.

Brief overview of preclinical and clinical studies in the development of intraperitoneal radioimmunotherapy for ovarian cancer.

Due to the generally slow and incomplete transit of i.p. infused agents into the circulation, treating disease confined to the peritoneal cavity with chemotherapy, biologics, and/or radionuclides provides a pharmacologic advantage. A higher i.p. concentration can be achieved than could be tolerated by systemic administration. An advantage of i.p. versus i.v. administration for localization of radiolabeled antibodies to small peritoneal surface disease has been shown in animal model and human biopsy studies (1, 2). A recent phase III Gynecologic Oncology Group chemotherapy trial has confirmed a survival advantage for i.p. delivery among women undergoing initial therapy for advanced ovarian cancer (3). Although the therapy was more difficult to tolerate such that 60% of patients randomized to the i.p. arm did not complete the entire regimen, there was a 16-month survival advantage. I.p. radionuclide therapy has been used in treatment of ovarian cancer for more than three decades, but side effects have been problematic in non-tumor-targeted 32P therapy (4). Efforts to improve specificity have used a number of antigens expressed on ovarian cancer cells as targets for selective delivery of radionuclide-conjugates. Mouse models and cell culture have been prominent for preclinical study of agents and strategies in the development of i.p. targeted radionuclide therapy for ovarian cancer. Animal studies, which have directed clinical trials, have shown clear improvement in survival with various modifications including combination chemotherapy, pretargeting, and combination of antibodies over simply delivery of a radiolabeled antibody via i.p. route.

Preparation and biological evaluation of 111In-, 177Lu- and 90Y-labeled DOTA analogues conjugated to B72.3.

Three 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid (DOTA) analogues were evaluated for relative in vivo stability when radiolabeled with (111)In, (90)Y and (177)Lu and conjugated to the monoclonal antibody B72.3. The DOTA analogues evaluated were "NHS-DOTA" [N-hydroxysuccinimdyl (NHS) group activating one carboxylate], "Arm-DOTA" (also known as MeO-DOTA; with a p-NCS, o-MeO-benzyl moiety on the methylene group of one acetic acid arm) and "Back-DOTA" (with a p-NCS-benzyl moiety on a backbone methylene group of the macrocycle). The B72.3 was conjugated to the DOTA analogues to increase the retention time of the radioloabeled conjugates in vivo in mice. The serum stability of the various radiometalated DOTA conjugates showed them to have good stability out to 168 h (all >95% except (111)In-NHS-DOTA-B72.3, which was 91% stable). Hydroxyapatite stability for the (111)In and (177)Lu DOTA-conjugates was >95% at 168 h, while the (90)Y DOTA-conjugates were somewhat less stable (between 90% and 95% at 168 h). The biodistribution studies of the radiometalated DOTA-conjugates showed that no significant differences were observed for the (111)In and (177)Lu analogues; however, the (90)Y analogues showed lower stabilities, as evidenced by their increased bone uptake relative to the other two [2-20% injected dose per gram (% ID/g) for (90)Y and 2-8% ID/g for (111)In and (177)Lu]. The lower stability of the (90)Y analogues could be due to the higher beta energy of (90)Y and/or to the larger ionic radius of Y(3+). Based on the bone uptake observed, the (177)Lu-NHS-DOTA-B72.3 had slightly lower stability than the (177)Lu-Arm-DOTA-B72.3 and (177)Lu-Back-DOTA-B72.3, but not significantly at all time points. For (90)Y, the analogue showing the lowest stability based on bone uptake was (90)Y-Arm-DOTA-B72.3, perhaps because of the metal's larger ionic radius and potential steric interactions minimizing effective complexation. The (111)In analogues all showed similar biological distributions at the various time points. This study suggests that care must be taken when evaluating (90)Y-labeled antibodies and in using NHS-DOTA-antibody conjugates with (177)Lu. All evaluations should be extended to time points relevant to the half-life of the radiometal and the therapy applications.