Impurity profiling of N,N'-ethylenebis-l-cysteine diethyl ester (Bicisate).

A HPLC-UV-CAD method with a HILIC column for impurity profiling of the 99mTc chelating agent bicisate has been developed and evaluated. Bicisate and its impurities were separated by means of isocratic elution on a zwitterionic stationary phase using a mixture of 7.5mmol/L trifluoroacetic acid and acetonitrile (47.5:52.5 V/V) as the mobile phase. Five different bicisate batches of a manufacturer were tested using the method. In addition LC-MS experiments were conducted in order to identify the impurities. The predominant impurities found were the oxidation product (disulfide), the monoester of ethylene dicysteine and an unknown compound with an m/z of 293 in ESI positive mode. A new degradation product of bicisate, bicisate lactam, was identified during sample solution stability assessment.

Pretargeted PET Imaging Using a Bioorthogonal 18F-Labeled trans-Cyclooctene in an Ovarian Carcinoma Model.

In cancer research, pretargeted positron emission tomography (PET) imaging has emerged as an effective two-step approach that combines the excellent target affinity and selectivity of antibodies with the advantages of using short-lived radionuclides such as fluorine-18. One possible approach is based on the bioorthogonal inverse-electron-demand Diels-Alder (IEDDA) reaction between tetrazines and trans-cyclooctene (TCO) derivatives. Here, we report the first successful use of an 18F-labeled small TCO compound, [18F]1 recently developed in our laboratory, to perform pretargeted immuno-PET imaging. The study was performed in an ovarian carcinoma mouse model, using a trastuzumab-tetrazine conjugate.

Synthesis and preclinical evaluation of [11C]MA-PB-1 for in vivo imaging of brain monoacylglycerol lipase (MAGL).

MAGL is a potential therapeutic target for oncological and psychiatric diseases. Our objective was to develop a PET tracer for in vivo quantification of MAGL. We report [11C]MA-PB-1 as an irreversible MAGL inhibitor PET tracer. The in vitro inhibitory activity, ex vivo distribution, brain kinetics and specificity of [11C]MA-PB-1 binding were studied. Ex vivo biodistribution and microPET showed good brain uptake which could be blocked by pretreatment with both MA-PB-1 and a structurally non-related MAGL inhibitor MJN110. These initial results suggest that [11C]MA-PB-1 is a suitable tracer for in vivo imaging of MAGL.

Micro-flow photosynthesis of new dienophiles for inverse-electron-demand Diels-Alder reactions. Potential applications for pretargeted in vivo PET imaging.

Pretargeted PET imaging has emerged as an effective two-step in vivo approach that combines the superior affinity and selectivity of antibodies with the rapid pharmacokinetics and favorable dosimetry of smaller molecules radiolabeled with short-lived radionuclides. This approach can be based on the bioorthogonal inverse-electron-demand Diels-Alder (IEDDA) reaction between tetrazines and trans-cyclooctene (TCO) derivatives. We aimed to develop new [18F]TCO-dienophiles with high reactivity for IEDDA reactions, and favorable in vivo stability and pharmacokinetics. New dienophiles were synthesized using an innovative micro-flow photochemistry process, and their reaction kinetics with a tetrazine were determined. In vivo stability and biodistribution of the most promising 18F-radiolabeled-TCO-derivative ([18F]3) was investigated, and its potential for in vivo pretargeted PET imaging was assessed in tumor-bearing mice. We demonstrated that [18F]3 is a suitable dienophile for IEDDA reactions and for pretargeting applications.

[18F]JNJ42259152 binding to phosphodiesterase 10A, a key regulator of medium spiny neuron excitability, is altered in the presence of cyclic AMP.

Phosphodiesterase 10A (PDE10A) is a key regulator of medium spiny neuron excitability. Therefore, it plays an important role in the regulation of motor, reward, and cognitive processes. Despite the interest in PDE10A as a drug and positron emission tomography (PET) imaging target, little is known about the regulation of PDE10A enzymatic activity. This study aimed to further investigate the role of cAMP in the regulation of PDE10A activity and PDE10A PET imaging. Using [18 F]JNJ42259152 as radioligand, we investigated alterations in PDE10A binding secondary to changes in cAMP levels. An in vitro striatum homogenate binding assay was developed to determine KD and Bmax of [18 F]JNJ42259152. Homogenate binding was assessed after addition of increasing concentrations of exogenous cAMP (1, 10, and 100 µM). Rats were treated using JNJ49137530 and rolipram to induce in vivo alterations of cAMP. The effect of the induced cAMP alterations on PDE10A binding was assessed by comparing [18 F]JNJ42259152 microPET studies after treatment to microPET studies acquired at baseline conditions prior to treatment. In vitro binding affinity of [18 F]JNJ42259152 was higher in the presence of cAMP compared to baseline conditions (KD  = 3.17 ± 0.91 nM with 10 µM cAMP vs. KD  = 6.62 ± 0.7 nM at baseline). Inhibition of PDE4 using rolipram significantly increased [18 F]JNJ42259152 binding (BPND  = 2.61 ± 0.50 vs. 1.91 ± 0.36 at baseline). Administration of the PDE2 inhibitor JNJ49137530 significantly increased PDE10A binding potential (BPND  = 2.74 ± 0.22 vs. 2.05 ± 0.16 at baseline). Our data indicate an important role for cAMP in the regulation of PDE10A activity. Additionally, our data show a profound interaction between several PDEs in striatum.

Dynamic 68Ga-DOTATOC PET/CT and static image in NET patients. Correlation of parameters during PRRT.

PURPOSE: To investigate the relationship between the dynamic parameters (Ki) and static image-derived parameters of 68Ga-DOTATOC-PET, to determine which static parameter best reflects underlying somatostatin-receptor-expression (SSR) levels on neuroendocrine tumours (NETs). PATIENTS, METHODS: 20 patients with metastasized NETs underwent a dynamic and static 68Ga-DOTATOC-PET before PRRT and at 7 and 40 weeks after the first administration of 90Y-DOTATOC (in total 4 cycles were planned); 175 lesions were defined and analyzed on the dynamic as well as static scans. Quantitative analysis was performed using the software PMOD. One to five target lesions per patient were chosen and delineated manually on the baseline dynamic scan and further, on the corresponding static 68Ga-DOTATOC-PET and the dynamic and static 68Ga-DOTATOC-PET at the other time-points; SUVmax and SUVmean of the lesions was assessed on the other six scans. The input function was retrieved from the abdominal aorta on the images. Further on, Ki was calculated using the Patlak-Plot. At last, 5 reference regions for normalization of SUVtumour were delineated on the static scans resulting in 5 ratios (SUVratio). RESULTS: SUVmax and SUVmean of the tumoural lesions on the dynamic 68Ga-DOTATOC-PET had a very strong correlation with the corresponding parameters in the static scan (R²: 0.94 and 0.95 respectively). SUVmax, SUVmean and Ki of the lesions showed a good linear correlation; the SUVratios correlated poorly with Ki. A significantly better correlation was noticed between Ki and SUVtumour(max and mean) (p < 0.0001). CONCLUSIONS: As the dynamic parameter Ki correlates best with the absolute SUVtumour, SUVtumour best reflects underlying SSR-levels in NETs.

Individualized dosimetry-based activity reduction of 9°Y-DOTATOC prevents severe and rapid kidney function deterioration from peptide receptor radionuclide therapy.

PURPOSE: Assessment of kidney function evolution after (90)Y-DOTATOC peptide receptor radionuclide therapy (PRRT) with capped activity administration based on a 37-Gy threshold of biological effective dose (BED) to the kidney. METHODS: In a prospective phase II study, patients with metastasized neuroendocrine tumours were evaluated for therapy using 185 MBq (111)In-pentetreotide with amino acid coinfusion. Planar whole-body images were acquired at four time-points after injection and kidney volumes were measured using CT/MRI. BED to the kidneys was estimated using an extended BED formula and biexponential renal clearance. Based on published BED dose-toxicity relationships, we allowed a maximal kidney BED of 37 Gy; if the calculated BED exceeded 37 Gy, treatment activity was reduced accordingly. Kidney function was assessed at baseline and at 18 months, predominantly using (51)Cr-EDTA. The rate of renal function decline was expressed as annual glomerular filtration rate loss (aGFRL). RESULTS: Only 22 of 50 patients reached the 18-months time-point, with most missing patients having died due to disease progression. In the 22 patients who reached 18 months, no rapid kidney function deterioration was observed over the 18 months, aGFRL >33% was not seen, and only three patients showed an increase of one toxicity grade and one patient an increase of two grades. No significant correlations between kidney volume (p = 0.35), baseline GFR (p = 0.18), risk factors for renal function loss (p = 0.74) and aGFRL were observed. Among the 28 patients who did not reach 18 months, one developed grade 4 kidney toxicity at 15 months after PRRT. CONCLUSION: Prospective dosimetry using a 37 Gy BED as the threshold for kidney toxicity is a good guide for (90)Y-DOTATOC PRRT and is associated with a low risk of rapid renal function deterioration and evolution to severe nephrotoxicity.

Development and biological evaluation of 99mTc-sulfonamide derivatives for in vivo visualization of CA IX as surrogate tumor hypoxia markers.

In vivo visualization of tumor hypoxia related markers, such as the endogenous transmembrane protein CA IX may lead to novel therapeutic and diagnostic applications in the management of solid tumors. In this study 4-(2-aminoethyl)benzene sulfonamide (AEBS, K(i) = 33 nM for CA IX) has been conjugated with bis(aminoethanethiol) (BAT) and mercaptoacetyldiglycine (MAG2) tetradendate ligands and the conjugates radiolabelled with (99m)Tc, to obtain anionic and neutral (99m)Tc-labeled sulfonamide derivatives, respectively. The corresponding rhenium analogues were also prepared and showed good inhibitory activities against hCA IX (K(i) = 59-66 nM). In addition, a second generation bis AEBS was conjugated with MAG2 and labeled with (99m)Tc, and the obtained diastereomers were also evaluated in targeting CA IX. Biodistribution studies in mice bearing HT-29 colorectal xenografts revealed a maximum tumor uptake of <0.5% ID/g at 0.5 h p.i for all the tracers. In vivo radiometabolite analysis indicated that at 1 h p.i. MAG2 tetradendate ligands were more stable in plasma (>50% intact) compared to the neutral complex (28% intact). This preliminary data suggest that negatively charged (99m)Tc-labeled sulfonamide derivatives with modest lipophilicity and longer circulation time could be promising markers to target CA IX.

Targetability and biodistribution of radioiodinated hypericin: comparison between microdosing and carrier-added preparations.

OBJECTIVES: To study the effect of co-injecting unlabelled hypericin (Hyp) on biodistribution, necrosis uptake and tumour retention of iodine-123 or iodine-131 labelled hypericin ((123/131)I-Hyp), a necrosis avid agent for an anticancer radiotherapy. METHODS: (123/131)I-Hyp was prepared with Iodogen as oxidant and formulated in 0.6 µg/kg no-carrier-added (NCA) or 0.25 mg/kg unlabelled Hyp carrier-added (CA) forms using dimethyl sulfoxide/polyethylene glycol-400/propylene glycol/water (25/25/25/25% v/v/v/v), as solvent mixture. Comparisons on biodistribution and necrosis uptake of NCA and CA(123)I-Hyp were conducted on rats (n=24) of reperfused liver infarction (RPLI) in 48h p.i. Tumour retention of CA(131)I-Hyp was assessed in severe combined immunodeficiency (SCID) mice with fibrosarcoma (RIF-1) tumours (n=25) over 40 days. To cause intratumour necrosis, mice were pre-treated with a vascular disrupting agent CA4P at 10mg/kg. Tissue-gamma counting (TGC), autoradiography and histology were performed. RESULTS: TGC revealed no significant difference in organ biodistribution between RPLI-rats injected with NCA and CA(123)I-Hyp, except in intestines, liver, lungs and stomach (P<0.05). Both preparations showed hepatobiliary excretion since intestines and faeces retained the most radioactivity. NCA and CA(123)I-Hyp exhibited high avidity and selectivity for hepatic infarction. From the day after injection onward, CA(123)I-Hyp showed greater target accumulation (7-11%ID/g) than (123)I-Hyp alone (~4%ID/g; P<0.05). In RIF-1-SCID mice receiving CA(131)I-Hyp, prolonged high retention in tumour necrosis was detected over 40 days p. i. TGC findings were confirmed by histological and autoradiographic analysis. CONCLUSIONS: The study demonstrated the co-injection of unlabelled Hyp affected necrosis uptake but almost no biodistribution of radioiodinated Hyp. Long-term high retention into tumour necrosis characterizes the carrier-added (131)I-Hyp.

Radioiodinated hypericin: its biodistribution, necrosis avidity and therapeutic efficacy are influenced by formulation.

PURPOSE: To study whether formulation influences biodistribution, necrosis avidity and tumoricidal effects of the radioiodinated hypericin, a necrosis avid agent for a dual-targeting anticancer radiotherapy. METHODS: Iodine-123- and 131-labeled hypericin ((123)I-Hyp and (131)I-Hyp) were prepared with Iodogen as oxidant, and formulated in dimethyl sulfoxide (DMSO)/PEG400 (polyethylene glycol 400)/water (25/60/15, v/v/v) or DMSO/saline (20:80, v/v). The formulations with excessive Hyp were optically characterized. Biodistribution, necrosis avidity and tumoricidal effects were studied in rats (n = 42) without and with reperfused liver infarction and implanted rhabdomyosarcomas (R1). To induce tumor necrosis, R1-rats were pre-treated with a vascular disrupting agent. Magnetic resonance imaging, tissue-gamma counting, autoradiography and histology were used. RESULTS: The two formulations differed significantly in fluorescence and precipitation. (123)I-Hyp/Hyp in DMSO/PEG400/water exhibited high uptake in necrosis but lower concentration in the lung, spleen and liver (p < 0.01). Tumor volumes of 0.9 ± 0.3 cm(3) with high radioactivity (3.1 ± 0.3% ID/g) were detected 6 days post-treatment. By contrast, (131)I-Hyp/Hypin DMSO/saline showed low uptake in necrosis but high retention in the spleen and liver (p < 0.01). Tumor volumes reached 2.6 ± 0.7 cm(3) with low tracer accumulation (0.1 ± 0.04%ID/g). CONCLUSIONS: The formulation of radioiodinated hypericin/hypericin appears crucial for its physical property, biodistribution, necrosis avidity and tumoricidal effects.

Biodistribution and radiation dosimetry of radioiodinated hypericin as a cancer therapeutic.

Iodine-131­labeled monoiodohypericin (131I­Hyp) is a necrosis avid compound used as a complementary anticancer agent. Herein, the biodistribution in rats with re-perfused partial liver infarction (RPLI) was used to estimate its human internal radiation dosimetry. Iodine-123­labeled monoiodohypericin (123I-Hyp) as a safer surrogate for 131I-Hyp was prepared with iodogen as oxidant. Determination of radiochemical yield and purification was performed by high performance liquid chromatography (HPLC). To control aggregation, the formulation was macroscopically and microscopically examined. Biodistribution of 123I-Hyp was studied in RPLI rats (n=18) at 4, 24 and 48 h post-injection. Tissue gamma counting (TGC), autoradiography and histology were performed. Dosimetry of 131I-Hyp in hepatic necrosis and in normal human organs was estimated using biodistribution data of 123I-Hyp, the Organ Level Internal Dose Assessment/Exponential Modeling (OLINDA/EXM®), a sphere model and male and female phantoms. A radiochemical yield of 95% was achieved in labeling of 123I-Hyp with a radiochemical purity of 99% after HPLC purification. In the Hyp added formulation, no macroscopic but minimal microscopic aggregation was observed. By TGC, selective accumulation in hepatic infarction and low uptake in viable liver of 123I­Hyp/Hyp were detected, as confirmed by autoradiography and histology. Significantly higher doses of 131I-Hyp were delivered to necrotic (276­93,600 mGy/MBq) than to viable (4.2 mGy/MBq) liver (P<0.05). In normal organs, 123I­Hyp was eliminated within 24 h except for relatively high levels in the lungs and thyroid. Hepatobiliary elimination was a major pathway of 123I-Hyp causing high activity in the intestines. For both genders, dosimetry showed the longest residence time of 131I-Hyp in the remainder, followed by the lungs, intestines and thyroid. The highest absorbed radiation dose was seen in necrotic tissues and the shortest residence times and lowest absorbed radiation dose were found in the brain. 131I-Hyp selectively delivers higher radiation dose to necrosis compared with the rest of the body. Among normal organs, thyroids, lungs and intestines receive considerable radiation dose, which deserves cautious attention in developing this anticancer approach.

Influence of time delay on the estimated lung shunt fraction on 99mTc-labeled MAA scintigraphy for 90Y microsphere treatment planning.

90Y-microspheres therapy is used to treat selected patients with primary or metastatic liver tumors in a safe and effective way. As a preparation for 90Y-microspheres treatment, a 99mTc-macroaggregated albumin (99mTc-MAA) simulation procedure is essential to evaluate particle shunting to the lung or gastrointestinal tract. We investigated the effect of interval between injection of 99mTc-MAA and time of scanning on the lung shunt fraction (LSF). In 4 patients with secondary hepatic malignancies who underwent repeated whole-body scintigraphy up to 5 hours after injection of 99mTc-MAA, a marked change in LSF was observed. It appears that tracer degradation leads to an important overestimation of LSF at later time points. An overestimation of LSF can lead to dose reduction or canceling of the planned 90Y-microspheres treatment. It is concluded that the interval between injection and scanning should be kept as short as possible.

Improved clearance of radioiodinated hypericin as a targeted anticancer agent by using a duodenal drainage catheter in rats.

We sought to reduce the radioactive intestinal waste after intravenous injection of necrosis avid iodine-131-labeled hypericin in dual-targeting anticancer radiotherapy and to study its pharmacokinetics in rats using a newly designed catheter. Iodine-123-labeled hypericin was prepared with iodogen as oxidant and characterized by high-performance liquid chromatography and mass spectrometry. After iodine-123-labeled hypericin administration, duodenal juice was collected via a catheter from groups of rats (n = 5) at intervals of 0-4, 4-8 or 20-24 h. The content was assessed by gamma-counting. The biodistribution and pharmacokinetics of iodine-123-labeled hypericin were investigated in rats without (n = 5) and with continuous catheterization (n = 5) for 9 h. After labeling, a high radiochemical yield was obtained with iodine-123-labeled hypericin (>95%), as confirmed by high-performance liquid chromatography and mass spectrometry. In the duodenal aspirate from animals with intermittent catheterization during 24 h, radioactivity accounted for 46% of the total with two peaks at 3 h and 8 h, suggesting enterohepatic circulation. Rats with 9 h of catheterization exhibited one peak representing 20% of the radioactivity. Major metabolites appeared to be conjugated iodine-123-labeled hypericin forms. In rats without and with catheter, iodine-123-labeled hypericin showed exponential elimination from plasma with no significant dehalogenation. Delayed iodine-123-labeled hypericin excretion, a higher maximum concentration (Cmax), larger area under concentration-time curve [AUC(0-∞)] and a longer mean residence time were observed in non-catheterized animals (P < 0.05). The catheterized group exhibited lower urinary excretion than non-catheterized group (P < 0.05). Rats with a catheter showed lower radioactivity (P = 0.01) in the small intestines than those without a catheter (1.82 ± 0.41 versus 18.95 ± 4.32 percentage of the injected dose). After iodine-123-labeled hypericin administration, the radioactivity excreted into bile was efficiently removed from the body via a duodenal catheter. Radiation overexposure due to the prolonged elimination of iodine-131-labeled hypericin can be prevented using this approach.

Synthesis and biological evaluation of 68Ga-bis-DOTA-PA as a potential agent for positron emission tomography imaging of necrosis.

INTRODUCTION: Necrosis is a form of cell death that occurs in a variety of pathological conditions but can also be the result of therapy in cancer treatment. A radiotracer that could image necrotic cell death using PET could therefore be a useful tool to provide relevant information on the disease activity or therapeutic efficacy and assist in diagnosis and therapy management of several disorders. Pamoic acid derivatives have previously been reported to show a selective uptake in tissue undergoing cellular death via necrosis. In this study 4,4'-methylene-bis(2-hydroxy-3-naphthoic hydrazide) (pamoic acid bis-hydrazide) was conjugated to the macrocyclic ligand DOTA and labeled with the generator produced positron emitter (68)Ga. The resulting complex ((68)Ga-bis-DOTA-PA; (68)Ga-3) was evaluated as a potential radiotracer for imaging tissues undergoing cellular death via necrosis. METHODS: Bis-DOTA-PA was synthesized and labeled with (68)Ga. Biodistribution of (68)Ga-3 and analysis of plasma were studied in normal NMRI mice. Binding of the complex to necrotic tissue was first evaluated by in vitro autoradiography. Further evaluation of the uptake in necrotic tissue was performed in two different models of necrosis using microPET imaging in correlation with ex vivo autoradiography, biodistribution studies and histochemical staining. A biodistribution study in a mouse model of hepatic apoptosis was performed to study the selectivity of the uptake of (68)Ga-bis-DOTA-PA in necrotic tissue. RESULTS: (68)Ga-3 was obtained with a decay-corrected radiochemical yield of 51.8% ± 5.4% and a specific activity of about 12 GBq/µmol. In normal mice, the complex was slowly cleared from blood, mainly through the renal pathway, and showed high in vivo stability. (68)Ga-bis-DOTA-PA displayed high and selective uptake in necrotic tissue and allowed imaging of necrotic tissue using microPET. CONCLUSION: (68)Ga-3 was synthesized and characterized. In vitro, in vivo and ex vivo studies showed that the complex displays high and selective uptake in tissue undergoing cellular death via necrosis.

Synthesis and biological evaluation of 68Ga labeled bis-DOTA-3,3'-(benzylidene)-bis-(1H-indole-2-carbohydrazide) as a PET tracer for in vivo visualization of necrosis.

The aim of the present study was to develop a (68)Ga labeled bis-DOTA derivative of benzylidene-bis-indole and compare the in vivo stability and biodistribution with that of the previously reported bis-DTPA derivate for in vivo imaging of necrosis using PET. Uptake of the tracer was evaluated in a mouse model of Fas-mediated hepatic apoptosis in correlation with histochemical stainings. The novel (68)Ga labeled tracer showed an improved in vivo stability and could therefore be used for selective non-invasive imaging of necrotic cell death using PET.

Whole-body biodistribution and radiation dosimetry of the cannabinoid type 2 receptor ligand [11C]-NE40 in healthy subjects.

PURPOSE: The type 2 cannabinoid receptor (CB2R) is part of the human endocannabinoid system and is involved in central and peripheral inflammatory processes. In vivo imaging of the CB2R would allow study of several (neuro)inflammatory disorders. In this study we have investigated the safety and tolerability of [11C]-NE40, a CB2R positron emission tomography (PET) ligand, in healthy human male subjects and determined its biodistribution and radiation dosimetry. PROCEDURE: Six healthy male subjects (age 20-65 years) underwent a dynamic series of nine whole-body PET/CT scans for up to 140 min, after injection of an average bolus of 286 MBq of [11C]-NE40. Organ absorbed and total effective doses were calculated through OLINDA. RESULTS: [11C]-NE40 showed high initial uptake in the spleen and a predominant hepatobiliary excretion. In the brain, rapid uptake and swift washout were seen. Organ absorbed doses were largest for the small intestine and liver, with 15.6 and 11.5 µGy/MBq, respectively. The mean effective dose was 3.64±0.81 µSv/MBq. There were no changes with aging observed. No adverse events were encountered. CONCLUSIONS: This first-in-man study of [11C]-NE40 showed an expected biodistribution compatible with lymphoid tissue uptake and appropriate fast brain kinetics in the healthy human brain, underscoring the potential of this tracer for further application in central and peripheral inflammation imaging. The effective dose is within the typical expected range for 11C ligands.

Small Molecule Sequential Dual-Targeting Theragnostic Strategy (SMSDTTS): from Preclinical Experiments towards Possible Clinical Anticancer Applications.

Hitting the evasive tumor cells proves challenging in targeted cancer therapies. A general and unconventional anticancer approach namely small molecule sequential dual-targeting theragnostic strategy (SMSDTTS) has recently been introduced with the aims to target and debulk the tumor mass, wipe out the residual tumor cells, and meanwhile enable cancer detectability. This dual targeting approach works in two steps for systemic delivery of two naturally derived drugs. First, an anti-tubulin vascular disrupting agent, e.g., combretastatin A4 phosphate (CA4P), is injected to selectively cut off tumor blood supply and to cause massive necrosis, which nevertheless always leaves peripheral tumor residues. Secondly, a necrosis-avid radiopharmaceutical, namely (131)I-hypericin ((131)I-Hyp), is administered the next day, which accumulates in intratumoral necrosis and irradiates the residual cancer cells with beta particles. Theoretically, this complementary targeted approach may biologically and radioactively ablate solid tumors and reduce the risk of local recurrence, remote metastases, and thus cancer mortality. Meanwhile, the emitted gamma rays facilitate radio-scintigraphy to detect tumors and follow up the therapy, hence a simultaneous theragnostic approach. SMSDTTS has now shown promise from multicenter animal experiments and may demonstrate unique anticancer efficacy in upcoming preliminary clinical trials. In this short review article, information about the two involved agents, the rationale of SMSDTTS, its preclinical antitumor efficacy, multifocal targetability, simultaneous theragnostic property, and toxicities of the dose regimens are summarized. Meanwhile, possible drawbacks, practical challenges and future improvement with SMSDTTS are discussed, which hopefully may help to push forward this strategy from preclinical experiments towards possible clinical applications.

Sequential systemic administrations of combretastatin A4 Phosphate and radioiodinated hypericin exert synergistic targeted theranostic effects with prolonged survival on SCID mice carrying bifocal tumor xenografts.

OBJECTIVES: Based on the soil-to-seeds principle, we explored the small-molecular sequential dual-targeting theranostic strategy (SMSDTTS) for prolonged survival and imaging detectability in a xenograft tumor model. MATERIALS AND METHODS: Thirty severe combined immunodeficiency (SCID) mice bearing bilateral radiation-induced fibrosarcoma-1 (RIF-1) subcutaneously were divided into group A of SMSDTTS with sequential intravenous injections of combretastatin A4 phosphate (CA4P) and (131)I-iodohypericin ((131)I-Hyp) at a 24 h interval; group B of single targeting control with CA4P and vehicle of (131)I-Hyp; and group C of vehicle control (10 mice per group). Tumoricidal events were monitored by in vivo magnetic resonance imaging (MRI) and planar gamma scintiscan, and validated by ex vivo autoradiography and histopathology. Besides, 9 mice received sequential intravenous injections of CA4P and (131)I-Hyp were subjected to biodistribution analysis at 24, 72 and 120 h. RESULTS: Gamma counting revealed fast clearance of (131)I-Hyp from normal organs but intense accumulation in necrotic tumor over 120 h. After only one treatment, significantly prolonged survival (p<0.001) was found in group A compared to group B and C with median survival of 33, 22, and 21 days respectively. Tumor volume on day 15 was 2.0 ± 0.89, 5.66 ± 1.66, and 5.02 ± 1.0 cm(3) with tumor doubling time 7.8 ± 2.8, 4.4 ± 0.67, and 4.5 ± 0.5 days respectively. SMSDTTS treated tumors were visualized as hot spots on gamma scintiscans, and necrosis over tumor ratio remained consistently high on MRI, autoradiography and histology. CONCLUSION: The synergistic antitumor effects, multifocal targetability, simultaneous theranostic property, and good tolerance of the SMSDTTS were evident in this experiment, which warrants further development for preclinical and clinical applications.

Diverse responses to vascular disrupting agent combretastatin a4 phosphate: a comparative study in rats with hepatic and subcutaneous tumor allografts using MRI biomarkers, microangiography, and histopathology.

OBJECTIVE: Differently located tumors of the same origin may exhibit diverse responses to the same therapeutics. To test this hypothesis, we compared the responses of rodent hepatic and subcutaneous engrafts of rhabdomyosarcoma-1 (R1) to a vascular disrupting agent Combretastatin A4 phosphate (CA4P). METHODS: Twelve WAG/Rij rats, each bearing three R1 implanted in the right and left hepatic lobes and subcutaneously in the thoracic region, received CA4P intravenously at 5 mg/kg (n = 6) or solvent (n = 6). Therapeutic responses were compared interindividually and intraindividually among tumors of different sites till 48 hours after injection using in vivo MRI, postmortem digital microangiography, and histopathology. RESULTS: MRI revealed that the subcutaneous tumors (STs) significantly increased in volume than hepatic tumors (HTs) 48 hours after CA4P (P < .05). Relative to vehicle controls and treated group at baseline, necrosis ratio, apparent diffusion coefficient, and enhancement ratio changed slightly with the STs but significantly with HTs (P < .05) after CA4P treatment. Vessel density derived from microangiography was significantly lower in STs compared to HTs without CA4P treatment. CA4P treatment resulted in decreased vessel density in HTs, while it did not affect vessel density in STs. MRI and microangiography outcomes were supported by histopathologic findings. CONCLUSIONS: MRI and microangiography allowed quantitative comparison of therapeutic responses to CA4P in rats with multifocal tumors. The discovered diverse effects of the same drug on tumors of the same origin but different locations emphasize the presence of cancer heterogeneity and the importance of individualization of drug delivery.

A safety study on single intravenous dose of tetrachloro-diphenyl glycoluril [iodogen] dissolved in dimethyl sulphoxide (DMSO).

1. Iodogen (tetrachloro-diphenyl glycoluril) dissolved in DMSO (dimethyl sulphoxide) appears indispensable in radioiodination of hypericin for a new anticancer strategy. We studied the safety of intravenously administered iodogen/DMSO in mice (n = 132). 2. Median lethal dose (LD50) of iodogen/DMSO was determined with doses of 40.0, 50.0, 55.0, 60.0, 65.0 and 70.0 mg/kg. Next, toxicity of iodogen/DMSO at 30.0 mg/kg was evaluated using saline and DMSO as controls. Changes in behaviour, body weight and serum biochemistry were evaluated. Histopathology of lungs, heart, liver and kidney was performed. 3. LD50 values of iodogen/DMSO were 59.5 mg/kg (95% confidence limits (CI): 54.1-65.4 mg/kg) and 61.0 mg/kg (95%CI: 56.2-66.2 mg/kg) for female and male mice, respectively. Similar to that of control groups, no animal deaths were encountered after iodogen/DMSO administration at 30.0 mg/kg. Body weights over 24 h were not altered in all groups, but significantly higher in iodogen/DMSO and DMSO groups (p < 0.05) 14 d post-injection. Blood urea nitrogen and alkaline phosphatase increased (p < 0.05) in iodogen/DMSO group without clinical symptoms. No pathologies were found by gross and microscopic inspection. 4. A single dose of iodogen/DMSO up to 30.0 mg/kg, over 3000 times the dose in potential human applications, appears safe, with an LD50 doubling that dose in mice.