Biodistribution and predictive hepatic gene expression of intravenous iron sucrose

Putting square pegs in round holes: why traditional pharmacokinetic principles cannot universally be applied to iron-carbohydrate complexes

Intravenous iron-carbohydrate complexes are nanomedicines that are commonly used to treat iron deficiency and iron deficiency anemia of various etiologies. Many challenges remain regarding these complex drugs in the context of fully understanding their pharmacokinetic parameters. Firstly, the measurement of the intact iron nanoparticles versus endogenous iron concentration fundamentally limits the availability of data for computational modeling. Secondly, the models need to include several parameters to describe the iron metabolism which is not completely defined and those identified (e.g. ferritin) exhibit considerable interpatient variability. Additionally, modeling is further complicated by the lack of traditional receptor/enzyme interactions. The known parameters of bioavailability, distribution, metabolism, and excretion for iron-carbohydrate nanomedicines will be reviewed and future challenges that currently prevent the direct application of physiologically-based pharmacokinetic or other computational modeling techniques will be discussed.

Tissue biodistribution of intravenous iron-carbohydrate nanomedicines differs between preparations with varying physicochemical characteristics in an anemic rat model

Intravenously administered iron-carbohydrate preparations are a structurally heterogenous class of nanomedicines. Iron biodistribution to target tissues is greatly affected by the physicochemical characteristics of these nanoparticles. Some regulatory agencies have recommended performing studies in animal models for biodistribution characterization and bioequivalence evaluation. In the present work, a systematic comparison of iron exposure, tissue biodistribution and pharmacodynamics of four intravenous iron-carbohydrates in anemic CD rats was conducted. A pilot study was performed to establish the anemic rat model, followed by a control study to evaluate the pharmacokinetics (serum iron, biodistribution) and pharmacodynamics (hematological parameters) in healthy and anemic controls and anemic rats receiving ferric carboxymaltose (FCM). The same parameters were then evaluated in a comparative study in anemic rats receiving FCM, iron sucrose (IS), iron isomaltoside 1000 (IIM), and iron dextran (ID). Despite similar serum iron profiles observed across the investigated nanomedicines, tissue iron biodistribution varied markedly between the individual intravenous iron-carbohydrate complexes. Tissue iron repletion differences were also confirmed by histopathology. These results suggest that employing serum iron profiles as a surrogate for tissue biodistribution may be erroneous. The variability observed in tissue biodistribution may indicate different pharmacodynamic profiles and warrants further study.

Nonclinical regulatory immunotoxicity testing of nanomedicinal products: Proposed strategy and possible pitfalls

Various nanomedicinal products (NMPs) have been reported to induce an adverse immune response, which may be related to their tendency to accumulate in or target cells of the immune system. Therefore, before their market authorization, NMPs should be thoroughly evaluated for their immunotoxic potential. Nonclinical regulatory immunotoxicity testing of nonbiological medicinal products, including NMPs, is currently performed by following the guideline S8 “Immunotoxicity Studies for Human Pharmaceuticals” of the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH). However, this guideline does not cover all the immunotoxicity endpoints reported for NMPs in the literature, such as complement activation related pseudo allergy, hypersensitivity and immunosuppression. In addition, ICH‐S8 does not provide any nanospecific testing considerations, which is important given their tendency to interfere with many commonly used toxicity assays. We therefore propose a nonclinical regulatory immunotoxicity assessment strategy, which considers the immunotoxicity endpoints currently missing in the ICH‐S8. We also list the known pitfalls related to the testing of NMPs and how to tackle them. Next to defining the relevant physicochemical and pharmacokinetic properties of the NMP and its intended use, the proposed strategy includes an in vitro assay battery addressing various relevant immunotoxicity endpoints. A weight of evidence evaluation of this information can be used to shape the type and design of further in vivo investigations. The final outcome of the immunotoxicity assessment can be included in the overall risk assessment of the NMP and provide alerts for relevant endpoints to address during clinical investigation.

This article is categorized under:

Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine

Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials

In vitro and in vivo DFO-chelatable labile iron release profiles among commercially available intravenous iron nanoparticle formulations

Intravenous (IV) iron formulations are complex colloidal suspensions of iron oxide nanoparticles. Small changes in formulation can allow more labile iron to be released after injection causing toxicity. Thus, bioequivalence (BE) evaluation of generic IV iron formulations remains challenging. We evaluated labile iron release in vitro and in vivo using a high performance liquid chromatography chelatable iron assay to develop a relational model to support BE. In vitro labile iron release and in vivo labile iron pharmacokinetics were evaluated for Venofer^®, Ferrlecit^®, generic sodium ferric gluconate complex, InFeD^®, Feraheme^® and a pre-clinical formulation GE121333. Labile iron release profiles were studied in vitro in 150 mM saline and a biorelevant matrix (rat serum) at 0.952 mgFe/mL. In vivo plasma labile iron concentration-time profiles (t0-240 min) were studied in rats after a 40 mgFe/kg IV dose. In vitro labile iron release in saline was significantly higher compared to rat serum, especially with InFeD^®. An in vitro release constant (iKr) was calculated which correlated well with maximal plasma concentrations in the in vivo rat PK model (R² = 0.711). These data suggest an in vitro to in vivo correlation model of labile iron release kinetics could be applied to BE. Other generic IV iron formulations need to be studied to validate this model.

Evaluation of the suitability of a Sprague Dawley rat model to assess intravenous iron preparations

The aim of the study was to examine the reproducibility of a rat model to assess the preclinical similarity in safety profiles and tissue accumulation of iron products. Accordingly, the effect of several doses of intravenously administered Venofer® and of Ferrlecit® on blood parameters, and on kidney and particularly liver toxicity were examined in non-anemic Sprague Dawley rats. The different analysis showed neither a clear treatment nor a dose effect after multiple injections. The parameters measured in this rat strain showed some iron induced adverse effects, but these could not be correlated to treatment specific differences. The findings presented in this paper indicate the difficulty to define a useful preclinical model to evaluate iron-based nano-colloidal preparations.

The Use of Magnetic Resonance Imaging for Non-Invasive Assessment of Venofer® Biodistribution in Rats

PURPOSE

The aim of this study was to determine the potential of magnetic resonance imaging to evaluate the biodistribution of exogenous iron within 24 h after one single injection of Venofer® (iron sucrose).

METHODS

Venofer® was evaluated in vitro for its ability to generate contrast in MR images. Subsequently, iron disposition was assessed in rats with MRI, in vivo up to 3 h and post mortem at 24 h after injection of Venofer®, at doses of 10- and 40 mg/kg body weight (n = 2 × 4), or saline (n = 4).

RESULTS

Within 10-20 min after injection of Venofer®, transverse relaxation rates (R₂) clearly increased, representative of a local increase in iron concentration, in liver, spleen and kidney, including the kidney medulla and cortex. In liver and spleen R₂ values remained elevated up to 3 h post injection, while the initial R₂ increase in the kidney was followed by gradual decrease towards baseline levels. Bone marrow and muscle tissue did not show significant increases in R₂ values. Whole-body post mortem MRI showed most prominent iron accumulation in the liver and spleen at 24 h post injection, which corroborated the in vivo results.

CONCLUSIONS

MR imaging is a powerful imaging modality for non-invasive assessment of iron distribution in organs. It is recommended to use this whole-body imaging approach complementary to other techniques that allow quantification of iron disposition at a (sub)cellular level.

Comparative Evaluation of U.S. Brand and Generic Intravenous Sodium Ferric Gluconate Complex in Sucrose Injection: Biodistribution after Intravenous Dosing in Rats

Relative biodistribution of FDA-approved innovator and generic sodium ferric gluconate (SFG) drug products was investigated to identify differences in tissue distribution of iron after intravenous dosing to rats. Three equal cohorts of 42 male Sprague-Dawley rats were created with each cohort receiving one of three treatments: (1) the innovator SFG product dosed intravenously at a concentration of 40 mg/kg; (2) the generic SFG product dosed intravenously at a concentration of 40 mg/kg; (3) saline dosed intravenously at equivalent volume to SFG products. Sampling time points were 15 min, 1 h, 8 h, 1 week, two weeks, four weeks, and six weeks post-treatment. Six rats from each group were sacrificed at each time point. Serum, femoral bone marrow, lungs, brain, heart, kidneys, liver, and spleen were harvested and evaluated for total iron concentration by ICP-MS. The ICP-MS analytical method was validated with linearity, range, accuracy, and precision. Results were determined for mean iron concentrations (µg/g) and mean total iron (whole tissue) content (µg/tissue) for each tissue of all groups at each time point. A percent of total distribution to each tissue was calculated for both products. At any given time point, the overall percent iron concentration distribution did not vary between the two SFG drugs by more than 7% in any tissue. Overall, this study demonstrated similar tissue biodistribution for the two SFG products in the examined tissues.

Iron sucrose: assessing the similarity between the originator drug and its intended copies

Iron sucrose (IS) is a complex nanocolloidal intravenous suspension used in the treatment of iron-deficiency anemia. Follow-on IS products (iron sucrose similars (ISSs)) have obtained marketing authorization by the generic pathway, implying that identical copies of IS may be manufactured. However, recent prospective and retrospective clinical studies showed discrepancies in clinical outcomes, which might be related to differences in physicochemical properties. The aim of this work is to measure and compare the physicochemical properties of IS and three ISSs available in the market using innovative analytical procedures. The comprehensive elucidation of size, size distribution, morphology, and stability of these complex drugs revealed very significant differences between the products. This study serves to provide the basis to define critical quality attributes that may be linked to differences in clinical outcome and thus may contribute to an adequate regulatory approach for IS and its follow-on products.

Complexity of intravenous iron nanoparticle formulations: implications for bioequivalence evaluation

Intravenous iron formulations are a class of complex drugs that are commonly used to treat a wide variety of disease states associated with iron deficiency and anemia. Venofer® (iron-sucrose) is one of the most frequently used formulations, with more than 90% of dialysis patients in the United States receiving this formulation. Emerging data from global markets outside the United States, where many iron-sucrose similars or copies are available, have shown that these formulations may have safety and efficacy profiles that differ from the reference listed drug. This may be attributable to uncharacterized differences in physicochemical characteristics and/or differences in labile iron release. As bioequivalence evaluation guidance evolves, clinicians should be educated on these potential clinical issues before a switch to the generic formulation is made in the clinical setting.

Bioavailability and stability of intravenous iron sucrose originator versus generic iron sucrose AZAD

CONTEXT

Severe iron deficiency requires intravenous iron supplementation to replenish iron stores. Intravenous iron sucrose has been used for decades for the treatment of anemia. New generic iron sucrose products are now marketed for the use in several countries and there is an ongoing discussion about the safety and efficacy of iron sucrose similars.

OBJECTIVE

In this study, we compared the iron sucrose originator Venofer® and the generic iron sucrose AZAD (ISA) regarding bioavailability, toxicity and stability in human THP-1 cells and HepG2 cells.

METHODS

The bioavailability of Venofer® and ISA was investigated in both cell types by a ferrozin-based assay. The release of incorporated iron was assayed by atomic absorption spectroscopy. Ferritin content was measured by enzyme-linked immunosorbent assay (ELISA). HepG2 cells were used to investigate the intracellular labile iron pool (LIP), which was measured by the fluorescent calcein assay. The amount of redox-active iron within the iron formulations was assayed using fluorescent dichlorofluorescein.

RESULTS

We found no significant differences in all parameters between Venofer® and ISA in regard of bioavailability, toxicity and stability in vitro.

DISCUSSION

ISA shows identical physico-chemical features and identical bioavailability in vitro. This study is a profound basis for future clinical tests with generic iron sucrose compounds.