Orally administered DTPA penta-ethyl ester for the decorporation of inhaled (241)Am

Enhanced thorium decorporation and mitigation of toxicity through combined use of Liv52® and diethylenetriamine pentaacetate

Thorium-232 (Th-232) is a promising fuel for advanced nuclear reactors. However, in case of internal human exposure to Th, there is currently no effective modality for its removal from liver and skeleton or for mitigating its effect. The FDA-approved agent, diethylenetriaminepentaacetate (DTPA), can remove Th and other actinides from blood circulation only. For the first time, a rationally-selected polyherbal hepatoprotective i.e. Liv52® (L52S), was evaluated in-combination with DTPA for its Th decorporation ability in Swiss mice. Inductively-coupled plasma mass spectroscopic analysis showed that oral administration of L52S in conjunction with DTPA significantly decreased Th burden from liver (20 %) and skeleton (33 %) as well as enhanced Th excretion (∼2.5 folds) through urine in comparison to DTPA or L52S alone. The combinatorial therapy was found to be complementary in-action, ameliorating Th-induced tissue damage in liver, spleen, and bone more effectively than monotherapy. Furthermore, markers of liver function (alanine transaminase) and liver inflammation and fibrosis (NF-κB & keratin) further validated the beneficial effect of L52S. The human consumption of L52S for various liver disorders further supports its clinical application for Th decorporation and mitigation of its health effects.

Enhancing oral bioavailability of Ca-DTPA by self double emulsifying drug delivery system (SDEDDS)

OBJECTIVE

BCS class III drug (highly soluble, poorly permeable) possesses low oral bioavailability. The research work highlights the utility of self-double emulsifying drug delivery system (SDEDDS) which are stable isotropic mixture of w/o primary emulsion and hydrophilic surfactants for improving oral bioavailability of Ca-DTPA (Calcium diethylenetriamine pentaacetate). Upon oral administration, SDEDDS rapidly emulsifies into w/o/w double emulsions in the aqueous gastrointestinal environment, with hydrophilic drugs entrapped inside oil reservoirs.

METHODS

SDEDDS formulation was successfully developed using excipients, that is, medium chain triglycerides, oleic acid, phospholipids, Span 80, Tween 80 using double emulsification technique.

RESULTS

The optimized formulation F4 (Aq. phase: 11.6%w,w; MCT & oleic acid: 70.9%w/w; Span 80:17.5%w/w; Lecithin:16%w/w and Tween 80 (10%w/w)) appeared bright yellow liquid which upon dilution appeared milky white within 2 min, droplet size (501.7 nm), pdi value (0.044), zeta potential (-52 mV), entrapment efficiency (79.6 ± 1.63), viscosity (72.2 ± 1.8 mpA.s), significant high cumulative in vitro drug permeation (CDP) and 2.17-fold increase in apparent permeability coefficient. Pharmacokinetic studies in rats showed 1.17-fold increases in AUC of F4 and comparatively higher plasma levels (Cmax) compared with pure drug administered orally. The Absolute (OF4, OD) and Relative bioavailability was found to be 14.52%, 12.35%, and 117.47%, respectively.

CONCLUSION

The present studies have clearly demonstrated that SDEDDS could readily form w/o/w double emulsions in vivo with enhanced in vitro and in vivo oral bioavailability. Therefore, considerable augmentation in the rate and extent of oral drug absorption ratified the better performance of the SDEDDS in enhancing the bioavailability of Ca-DTPA.

Self-Aggregated Nanoscale Metal-Organic Framework for Targeted Pulmonary Decorporation of Uranium

The limited availability of effective agents for removing actinides from the lungs significantly restricts the effectiveness of medical treatments for nuclear emergencies. Inhalation is the primary route of internal contamination in 44.3% of actinide-related accidents, leading to the accumulation of radionuclides in the lungs and resulting in infections and potential tumor formation (tumorigenesis). This study focuses on the synthesis of a nanometal-organic framework (nMOF) material called ZIF-71-COOH, which is achieved by post-synthetic carboxyl functionalization of ZIF-71. The material demonstrates high and selective adsorption of uranyl, while also exhibiting increased particle size (≈2100 nm) when it aggregates in the blood, enabling passive targeting of the lungs through mechanical filtration. This unique property facilitates the rapid enrichment and selective recognition of uranyl, making nano ZIF-71-COOH highly effective in removing uranyl from the lungs. The findings of this study highlight the potential of self-aggregated nMOFs as a promising drug delivery system for targeted uranium decorporation in the lungs.

Aerosolization of Zn-DTPA Decorporation Agent Using Jet and Ultrasonic Nebulizers

BACKGROUND

Chelating agents such as diethylenetriamine pentaacetic acid (DTPA) can be used as a decorporation drug in the zinc (Zn) form to treat internal radioactive contamination after exposure to plutonium or americium in a nuclear accident. Although Zn-DTPA is normally administered intravenously, inhalation of Zn-DTPA in aerosol form is a better route for direct delivery to the lungs. This work investigates the feasibility of synthesizing Zn-DTPA from three common chemicals and aerosolizing it using a jet or ultrasonic nebulizer.

METHODS

The particle size distribution (PSD) of this decorporation agent at different concentrations were tested in vitro using two different methods: inertial impaction and aerodynamic time of flight. The particles were generated using either a jet nebulizer or an ultrasonic nebulizer. Two parameters, namely the mass median aerodynamic diameter and the geometric standard deviation, were assessed to determine the PSD of the generated aerosols. These parameters were obtained for different concentrations of Zn-DTPA using both nebulizers.

RESULTS AND CONCLUSIONS

Zn-DTPA was successfully synthesized for decorporation purposes. Aerosol particles within the inhalable range were successfully generated by both nebulizers from four different concentrations of Zn-DTPA. It was found that the medication concentration did not affect the PSD of Zn-DTPA. The ultrasonic nebulizer was observed to produce a slightly larger aerosol particle size and required slightly longer treatment periods to deliver an effective dose to the lungs when compared with the jet nebulizer. Both nebulizers can be sustainably run to administer the agent for effective decorporation treatment of a large population after any major nuclear accident.

Interspecies Differences in the Metabolism of a Multiester Prodrug by Carboxylesterases

The pentaethyl ester prodrug of the chelating agent diethylene triamine pentaacetic acid (DTPA) referred to as C2E5 is being developed as an orally bioavailable radionuclide decorporation agent. The predicted human efficacy obtained in these experimental animals is confounded by interspecies variations of metabolism. Therefore, in the present study, carboxylesterase-mediated metabolism of [(14)C]-C2E5 was compared in the S9 intestinal and hepatic fractions of human, dog, and rat and their respective plasma. Intestinal hydrolysis of C2E5, resulting in the formation of the tetraethyl ester of DTPA (C2E4), was only detected in human and rat. The primary metabolite in human and dog hepatic fractions was C2E4, whereas the predominant species identified in rat hepatic fractions was the triethyl ester (C2E3). Hepatic hydrolysis of C2E5 causes the formation of C2E4 in human, dog, and rat and C2E3 in rat only. Minimal C2E5 hydrolysis was observed in human and dog plasma, whereas in rat plasma C2E5 converted to C2E3 rapidly, followed by slower further metabolism. Both recombinant CES1 and CES2 play roles in C2E5 metabolism. Together, these data suggest that dogs may be the most appropriate species for predicting human C2E5 metabolism, whereas rats might be useful for clarifying the potential toxicity of C2E5 metabolites.

Novel drug delivery systems for actinides (uranium and plutonium) decontamination agents

The possibility of accidents in the nuclear industry or of nuclear terrorist attacks makes the development of new decontamination strategies crucial. Among radionuclides, actinides such as uranium and plutonium and their different isotopes are considered as the most dangerous contaminants, plutonium displaying mostly a radiological toxicity whereas uranium exhibits mainly a chemical toxicity. Contamination occurs through ingestion, skin or lung exposure with subsequent absorption and distribution of the radionuclides to different tissues where they induce damaging effects. Different chelating agents have been synthesized but their efficacy is limited by their low tissue specificity and high toxicity. For these reasons, several groups have developed smart delivery systems to increase the local concentration of the chelating agent or to improve its biodistribution. The aim of this review is to highlight these strategies.

Orally administered DTPA di-ethyl ester for decorporation of (241)Am in dogs: Assessment of safety and efficacy in an inhalation-contamination model

PURPOSE

Currently two injectable products of diethylenetriaminepentaacetic acid (DTPA) are U.S. Food and Drug Administration (FDA)-approved for decorporation of (241)Am; however, an oral product is considered more amenable in a mass casualty situation. The di-ethyl ester of DTPA, named C2E2, is being developed as an oral drug for treatment of internal radionuclide contamination.

MATERIALS AND METHODS

Single-dose decorporation efficacy of C2E2 administered 24-h post contamination was determined in beagle dogs using a (241)Am nitrate inhalation contamination model. Single and multiple dose toxicity studies in beagle dogs were performed as part of an initial safety assessment program. In addition, the genotoxic potential of C2E2 was evaluated by the in vitro bacterial reverse mutation Ames test, mammalian cell chromosome aberration cytogenetic assay and an in vivo micronucleus test.

RESULTS

Oral administration of C2E2 significantly increased (241)Am elimination over untreated controls and significantly reduced the retention of (241)Am in tissues, especially liver, kidney, lung and bone. Daily dosing of 200 mg/kg/day for 10 days was well tolerated in dogs. C2E2 was found to be neither mutagenic or clastogenic.

CONCLUSIONS

The di-ethyl ester of DTPA (C2E2) was shown to effectively enhance the elimination of (241)Am after oral administration in a dog inhalation-contamination model and was well tolerated in toxicity studies.