Biodistribution and predictive hepatic gene expression of intravenous iron sucrose

INTRODUCTION

We have examined iron biodistribution and hepatic gene expression in rats following administration of the generic Iron Sucrose Azad (ISA) or the reference iron sucrose drug Venofer®.

METHODS

ISA and Venofer® were administered intravenously to normal, non-anemic, male rats at 15 mg/kg (a supra-therapeutic dose-level). To evaluate biodistribution, tissue iron levels were determined over 28 days for plasma, liver, spleen, bone marrow, heart, kidney, lung and stomach using a validated ICP-MS method. Hepatic gene expression was evaluated by microarray analysis of mRNA from samples taken 24 h after drug administration.

RESULTS

Iron concentration/time profiles for plasma and tissues were quantitatively similar for ISA and Venofer. Following administration, circulating iron levels briefly exceeded transferrin binding capacity and there was a transient increase in hepatic iron. Bone marrow iron levels remained elevated throughout the study. No increases in tissue iron levels were observed in the heart, stomach or lungs. Spleen iron levels increased over the course of the study in treated and control rats. Small, transient increases were recorded in the kidneys of treated rats. The effects of ISA and Venofer® on hepatic gene transcription were similar. Principal components analysis showed that there was no systematic effect of either treatment on transcriptional profiles. Only a small number of genes showed significant modulation of expression. No transcriptional pattern matches with toxicity pathways were found in the ToxFX database for either treatment. No modulation of key genes in apoptosis, inflammation or oxidative stress pathways was detected.

DISCUSSION

These findings demonstrated that the biodistribution of administered iron is essentially similar for Iron Sucrose Azad and Venofer®, that iron sucrose partitions predominantly into the liver, spleen and bone marrow, and that hepatic gene expression studies did not provide any evidence of toxicity in animals treated at a supra-therapeutic dose-level.

Human serum albumin isoforms: genetic and molecular aspects and functional consequences

BACKGROUND

At present, 67 different genetic variants of human serum albumin and proalbumin have been molecularly characterized at the protein and/or gene level.

SCOPE OF REVIEW

This review summarizes present knowledge about genetic and molecular aspects, functional consequences and potential uses of the variants.

MAJOR CONCLUSIONS

The frequency of bisalbuminemia in the general population is probably about 1:1000, but it can be much higher in isolated populations. Mutations are often due to hypermutable CpG dinucleotides, and in addition to single-amino acid substitutions, glycosylated variants and C-terminally modified alloalbumins have been found. Some mutants show altered stability in vivo and/or in vitro. High-affinity binding of Ni(++) and Cu(++) is blocked, or almost so, by amino acid changes at the N-terminus. In contrast, substitution of Leu90 and Arg242 leads to strong binding of triiodothyronine and l-thyroxine, respectively, resulting in two clinically important syndromes. Variants often have modified plasma half-lives and organ uptakes when studied in mice.

GENERAL SIGNIFICANCE

Because alloalbumins do not seem to be associated with disease, they can be used as markers of migration and provide a model for study of neutral molecular evolution. They can also give valuable molecular information about albumins binding sites, antioxidant and enzymatic properties, as well as stability. Mutants with increased affinity for endogenous or exogenous ligands could be therapeutically relevant as antidotes, both for in vivo and extracorporeal treatment. Variants with modified biodistribution could be used for drug targeting. In most cases, the desired function can be further elaborated by producing site-directed, recombinant mutants. This article is part of a Special Issue entitled Serum Albumin.

Biodistribution of photosensitizer-magnetic nanoparticle chelate complex in rabbits with VX2 metastatic hepatic carcinoma

AIM: To observe the biodistribution of photosensitizer-magnetic nanoparticle chelate complex (PMNCC) in rabbits with VX2 metastatic hepatic carcinoma.

METHODS: After PNMCC was successfully prepared, a rabbit model of VX2 metastatic hepatic carcinoma was developed. PMNCC was administered via the ear vein on the 16th, 18th and 20th day after induction of metastatic carcinoma, and tumor-bearing rabbits were sacrificed on the 22nd day. Tissue specimens were obtained and the biodistribution of PMNCC was observed by Prussian blue staining, atomic absorption spectroscopy (AAS) and transmission electron microscopy (TEM).

RESULTS: Prussian blue staining and TEM analysis showed that the amount of PMNCC in tumor tissue was significantly higher than those in the liver, spleen, or kidney. The mean relative iron concentration detected by atomic absorption spectroscopy in tumor tissue was 9.09 mg/L ± 2.31 mg/L, significantly higher than those in other organs (all P < 0.01).

CONCLUSION: PMNCC was mainly distributed in tumor tissue in rabbits with VX2 metastatic hepatic carcinoma, and PMNCC has the ability to carry magnetic nanoparticles into tumor cells.

Production and Quality Control of [(67)Ga]-DOTA-trastuzumab for Radioimmunoscintigraphy

Breast cancer radioimmunoscintigraphy targeting HER2/neu expression is a growing field of work in nuclear medicine research. In this study, trastuzumab was successively labeled with [(67)Ga] GaCl3 after conjugation with DOTA-NHS-ester. The conjugates were purified by molecular filtration, the average number of DOTA conjugated per mAb was calculated and total concentration was determined by spectrophotometric method. DOTA-Trastuzumab was labeled with (67)Ga. Radiochemical purity, integrity of protein after radiolabeling and stability of (67)Ga-DOTA-Trastuzumab were determined followed by biodistribution studies in wild-type rats (30 ± 5.5 μCi, 2, 4 and 24 h p.i.). The radioimmunoconjugate was prepared with a radiochemical purity of higher than 95% (RTLC). The average chelate to antibody ratio (c/a) for the conjugate used in this study was 5.8:1. The final compound was stable in presence of PBS at 37ºC and room temperature. The sample was showed to have similar patterns of migration in the gel electrophoresis similar to the native protein. The accumulation of the radiolabeled antibody in liver, spleen, kidney, heart and other tissues demonstrates. (67)Ga-DOTA-Trastuzumab was prepared as a surrogate for important clinically applicable radionuclides used in SPECT and PET including In-111 and Cu-64 as a model of radiolabeling. It is also a potential compound for molecular imaging of SPECT for diagnosis and treatment studies and follow-up of HER2 expression in oncology.

Radiosynthesis and Quality Control of [(67)Ga]-3,4-dimethoxylated Porphyrin Complex as a Possible Imaging agent

Radiolabeled porphyrins are potential tumor avid radiopharmaceuticals because of their impersonation in the human body, ability to complex various radionuclides, water solubility, low toxicity etc. In this work a radiogallium porphyrin complex has been developed. [(67)Ga] labeled 5,10,15,20-tetrakis(3,4-dimethoxyphenyl) porphyrin ([(67)Ga]-TDMPP) was prepared using freshly prepared [(67)Ga]GaCl3 and 5,10,15,20-tetrakis(3,4-dimethoxyphenyl) porphyrin (H2TDMPP) for 60 min at 100°C. Stability of the complex was checked in final formulation and human serum for 24 h, followed by biodistribution and imaging studies in wild type rats up to 24 h. The radiocomplex was obtained with radiochemical purity >99% (ITLC) and >98% (HPLC), specific activity: 12-15 GBq/mmol. The partition coefficient was determined (log P=1.63). A detailed comparative pharmacokinetic study performed for (67)Ga cation and [(67)Ga]-TDMPP. The complex was mostly washed out from the circulation through kidneys. Myocardial uptake was significantly observed by SPECT and biodistribution studies. Knee and shoulder joints demonstrated significant activity uptake in 2h post injection. Higher water solubility of the complex due to ionic nature of the complex is an advantage for rapid wash-out of the complex from the system, the complex has significant joint uptake compared to other radiolabeled porphyrins which the mechanisms are explained.

Biodistribution properties of cleistanthin A and cleistanthin B using magnetic resonance imaging in a normal and tumoric animal model

Aim:

To determine the biodistribution properties of cleistanthin A and cleistanthin B in rodents using magnetic resonance imaging (MRI).

Materials and Methods:

Cleistanthins A and B, constituents of Cleistanthus collinus Roxb., were labelled with gadolinium (Gd³⁺) directly and injected into normal and tumoric nude mice. The tissue signal intensity was measured using MRI to perform a noninvasive kinetic assay. Wistar rats were used for determination of the grayscale intensity to observe the distribution patterns of of cleistanthins A and B.

Results:

Cleistanthin A is kinetically more attractive to the gastrointestinal tract than is cleistanthin B, which gets accumulated in muscular tissues of mice in greater concentrations compared with cleistanthin A. Cleistanthin B but not cleistanthin A showed tumoric affinity and exhibited a tumor kinetic attraction in tumoric mice. In rats, cleistanthin A showed greater grayscale intensities in the brain, liver, and skeletal muscles in immediate post contrast MRI images, whereas the gadolinium tagged cleistanthin B showed higher grayscale intensities in the cardiac muscle and skeletal muscles in delayed post contrast MRI images.

Conclusions:

Cleistanthin A is more pharmacokinetically attractive to the gastrointestinal tract than cleistanthin B.

Modeling the time dependent distribution of a new (153)Sm complex for targeted radiotherapy purpose

BACKGROUND

For radioimmunotherapy purposes, a chemical complex with high absorption in cancer tumor is required. New chemicals are to be examined for their concentration in tumor and healthy organs. These are labeled with β-emitting radioisotopes to irradiate the tumor while deposited inside it.

AIM

To study the capability of recently developed chemical complex in targeting cancer tumor and investigate the distribution of (153)Sm-TPTTC in rat organs as function of time.

MATERIALS AND METHODS

The chemical complex - [Tris(1,10-phenanthroline)Samarium(III)] trithiocyanate was prepared and labeled with (153)Sm radioisotope. The labeled complex was injected to a population of tumor bearing mice. In 2, 4, 24, 48, 96 h after injection the animals were sacrificed and the concentration of Samarium complex was measured in various organs such as blood, heart, intestine, colon, liver, spleen, kidney, sternum and bone.

RESULTS

The concentration of the radiopharmaceutical in various organs was measured at different times. The temporal behavior of biodistribution of (153)Sm-TPTTC was modeled and drawn as function of time.

CONCLUSION

It is shown that (153)Sm-TPTTC is concentrated in tumor tissue and liver much more than in other organs. The variation of pharmaceutical concentration in all organs is described with summation of eight exponential terms and it approximates our experimental data with precision better than 2%.

Development of a (68)Ga-Fluorinated Porphyrin Complex as a Possible PET Imaging Agent

AIM

Due to the interesting pharmacologic properties of porphyrins, the idea of developing a possible tumor imaging agent using PET by incorporating (68)Ga into a suitable porphyrin ligand was investigated.

METHODS

(68)Ga-labeled 5,10,15,20-tetrakis(pentafluoro-13 phenyl) porphyrin ((68)Ga-TFPP) was prepared using freshly eluted [(68)Ga]GaCl3 obtained from a 68Ge/68Ga generator developed in-house and 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (H2TFPP) for 60 min at 100°C.

RESULTS

The complex was prepared with high radiochemical purity (>99% ITLC, >99% HPLC, specific activity: 13-14 GBq/mmol). Stability of the complex was checked in the final formulation and in human serum for 5 h. The partition coefficient was calculated for the compound (log P = 0.62). The biodistribution of the labeled compound in vital organs of Swiss mice bearing fibrosarcoma tumors was studied using scarification studies and SPECT imaging up to 1 h. The complex was mostly washed out from the circulation through kidneys and liver. The tumor-to-muscle ratio 1 h post injection was 5.13.

CONCLUSION

The radiolabeled porphyrin complex demonstrated potential for further imaging studies in other tumor models.

Production, Quality Control and Pharmacokinetic Studies of (177)Lu-EDTMP for Human Bone Pain Palliation Therapy Trials

Developing new bone pain palliation agents is a mandate in handling end-stage cancer patients around the world. Possibly, Lu-177 ethylenediaminetetramethylene phosphonic acid ((177)Lu-EDTMP) is a therapeutic agent which can be widely used in bone palliation therapy. In this study, (177)Lu-EDTMP complex was prepared successfully using synthesized EDTMP ligand and (177)LuCl3. Lu-177 chloride was obtained by thermal neutron irradiation (4 × 10(13) n.cm(-2)s(-1)) of natural Lu2O3 samples. Radiochemical purity of (177)Lu-EDTMP was determined by ITLC (more than 99%). Stability studies of the final preparations in the presence of human serum were performed. The biodistribution of (177)Lu-EDTMP and (177)LuCl3 in wild-type rats was studied by SPECT imaging. A comparative accumulation study for (177)Lu-EDTMP and (177)LuCl3 was performed for vital organs up to 7 days. The complex was obtained in high radiochemical purity (more than 99%). The complex was stable in vitro in presence of human serum as well as final formulation. Significant bone uptake (> 70%) was observed for the radiopharmaceutical. Due to better physical properties of Lu-177 compared to Sm-153 and acceptable biodistribution results of the compound, (177)Lu-EDTMP seemed to be an interesting new candidate for clinical trials for bone pain palliation therapy.

Preparation and biodistribution studies of a radiogallium-acetylacetonate bis (thiosemicarbazone) complex in tumor-bearing rodents

Various radiometal complexes have been developed for tumor imaging, especially Ga-68 tracer. In the present study, the development of a radiogallium bis-thiosemicarbazone complex has been reported. [(67)Ga] acetylacetonate bis(thiosemicarbazone) complex ([(67)Ga] AATS) was prepared starting [(67)Ga]Gallium acetate and freshly prepared acetylacetonate bis (thiosemicarbazone) (AATS) in 30 min at 90°C. The partition co-efficient and the stability of the tracer were determined in final solution (25°C) and the presence of human serum (37°C) up to 24 h. The biodistribution of the labeled compound in wild-type and fibrosarcoma-bearing rodents were determined up to 72 h. The radiolabled Ga complex was prepared in high radiochemical purity (> 97%, HPLC) followed by initial biodistribution data with the significant tumor accumulation of the tracer in 2 h which is far higher than free Ga-67 cation while the compound wash-out is significantly faster. Above-mentioned pharmacokinetic properties suggest an interesting radiogallium complex while prepared by the PET Ga radioisotope, (68)Ga, in accordance with the physical half life, for use in fibrosarcoma tumors, and possibly other malignancies.

Development of ga-67 maltolate complex as an imaging agent

Due to the antitumor activity of Gallium MAL complex, as well as recent findings on new targeted biomolecules in malignant cells through this complex, the development of radiolabeled gallium complex for future imaging studies was targeted. Ga-67 labeled 3-hydroxy-2-methyl-4H-pyran-4-onate (Ga-67 MAL) was prepared using freshly prepared Ga-67 chloride and 3-hydroxy-2-methyl-4H-pyran-4-onate in a sodium salt form in 25 min at 40° C. The stability of the complex was checked in final formulation and human serum for 24 h followed by the administration in Swiss mice for biodistribution studies. The complex was prepared in high radiochemical purity (> 97% ITLC, > 98% HPLC) and specific activity of 13-14 GBq/mmol and was stable in the presence of serum for 48 h. The partition coefficient was calculated for the compound (log p = 0.40). A detailed comparative pharmacokinetic study was performed for Ga-67 cation and Ga-67-MAL. The complex is more rapidly washed out from the circulation through kidneys and liver compared to Ga-67 cation and can be an interesting tumor imaging agent due to the fact that the cold compound is undergoing clinical trials as a safe and potential therapeutic agent for cancer.

A simple protocol for preparation of a liposomal vesicle with encapsulated plasmid DNA that mediate high accumulation and reporter gene activity in tumor tissue

The systemic delivery of gene therapeutics by non-viral methods has proven difficult. Transfection systems that are performing well in vitro have been reported to have disadvantageous properties such as rapid clearance and short circulation time often resulting in poor transfection efficiency when applied in vivo. Large unilaminary vesicles (LUV) with encapsulated nucleic acids designated stabilized-plasmid-lipo-particle (SPLP) have showed promising results in terms of systemic stability and accumulation in tumor tissue due to the enhanced permeability and retention effect (EPR). We have developed a simple protocol for the research-scale preparation of SPLPs from commercially available reagents with high amounts of encapsulated plasmid DNA. The SPLPs show properties of promising accumulation in tumor tissue in comparison to other organs when intravenously injected into xenograft tumor-bearing nude mice. Although transcriptionally targeted suicide gene therapy was not achieved, the SPLPs were capable of mediating reporter gene transfection in subcutaneous flank tumors originating from human small cell lung cancer.

Development of (166)Ho-phytate Complex for Radiosynovectomy

BACKGROUND

(66)Ho-chloride was obtained by bombardment of natural Ho(NO3)3 dissolved in acidic media using thermal neutron flux (4-5 × 10(13) n.cm(-2).s(-1)).

METHODS

(166)Ho-holmium chloride (185 MBq) was used successfully for preparation of (166)Ho-phytate complex with high radiochemical purity (>99.9 %, ITLC, MeOH: H2O: acetic acid, 4: 4: 2, as mobile phase). The complex stability and viscosity were checked in the final solution up to 2 days. The prepared complex solution (60 μCi/100 μl) was injected intraarticularly to male rat knee joints. Leakage of radioactivity from the injection site and its distribution in organs were investigated up to 2 days.

RESULTS

Approximately all of the injected dose had remained in the injection site 2 days after injection.

CONCLUSION

The complex was proved to be a feasible agent for cavital radiotherapy in oncology and rheumatology.

Preparation and quality control of the [sm]-samarium maltolate complex as a lanthanide mobilization product in rats

Development of lanthanide detoxification agents and protocols is of great importance in management of overdoses. Due to safety of maltol as a detoxifying agent in metal overloads, it can be used as a lanthanide detoxifying agent. In order to demonstrate the biodistribution of final complex, [¹⁵³Sm]-samarium maltolate was prepared using Sm-153 chloride (radiochemical purity >99.9%; ITLC and specific activity). The stability of the labeled compound was determined in the final solution up to 24h as well as the partition coefficient. Biodistribution studies of Sm-153 chloride, [¹⁵³Sm]-samarium maltolate were carried out in wild-type rats comparing the critical organ uptakes. Comparative study for Sm³⁺ cation and the labeled compound was conducted up to 48 h, demonstrating a more rapid wash out for the labeled compound. The effective and biological half lives of 2.3 h and 2.46h were calculated for the complex. The data suggest the detoxification property of maltol formulation for lanthanide overdoses.