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

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.

The clinical relevance of detectable plasma iron species in iron overload states and subsequent to intravenous iron-carbohydrate administration

Many disorders of iron homeostasis (e.g., iron overload) are associated with the dynamic kinetic profiles of multiple non-transferrin bound iron (NTBI) species, chronic exposure to which is associated with deleterious end-organ effects. Here we discuss the chemical nature of NTBI species, challenges with measuring NTBI in plasma, and the clinical relevance of NTBI exposure based on source (iron overload disorder vs. intravenous iron-carbohydrate complex administration). NTBI is not a single entity but consists of multiple, often poorly characterized species, some of which are kinetically non-exchangeable while others are relatively exchangeable. Prolonged presence of plasma NTBI is associated with excessive tissue iron accumulation in susceptible tissues, with consequences, such as endocrinopathy and heart failure. In contrast, intravenous iron-carbohydrate nanomedicines administration leads only to transient NTBI appearance and lacks evidence for association with adverse clinical outcomes. Assays to measure plasma NTBI are typically technically complex and remain chiefly a research tool. There have been two general approaches to estimating NTBI: capture assays and redox-activity assays. Early assays could not avoid capturing some iron from transferrin, thus overestimating NTBI. By contrast, some later assays may have promoted the donation of NTBI species to transferrin during the assay procedure, potentially underestimating NTBI levels. The levels of transferrin saturation at which NTBI species have been detectable have varied between different methodologies and between patient populations studied.

Regulatory Science Approach in Pharmaceutical Development of Follow-On Versions of Non-Biological Complex Drug Products

Scientific and technological breakthroughs in the field of Nanotechnology have been a driving force throughout the development and approval of Non-Biological Complex Drugs (NBCDs). However, the fast-growing expansion of NBCDs and the emergence of their follow-on versions have brought with them several scientific, technological, and regulatory challenges. The definition of NBCDs is still not officially recognized by the regulatory authorities, and there is no dedicated regulatory pathway addressing the particular features of NBCDs and their follow-on versions. The lack of clear and consistent regulatory guidance documents in this field, as well as, the inconsistency across different regulatory agencies, impact negatively on the acceptance and enormous potential of these drug products. Patient access to high-quality NBCDs follow-on versions may be compromised by regulatory uncertainty resulting from the use of different regulatory approaches across the globe, as well as within the same class of products. Accordingly, there is a real need to develop a specific regulatory pathway compliant with the complexity of NBCDs and their follow-on versions or, alternatively, make better use of available regulatory pathways. The main goal of the review is to deeply investigate and provide a critical overview of the regulatory landscape of NBCDs and follow-on versions currently adopted by the regulatory authorities. The dissemination of knowledge and discussion in this field can contribute to clarifying regulations, policies, and regulatory approaches to complex generics, thereby filling regulatory and scientific gaps in the establishment of therapeutic equivalence.

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.

Evaluation of the Physicochemical Properties of the Iron Nanoparticle Drug Products: Brand and Generic Sodium Ferric Gluconate

Complex iron nanoparticle-based drugs are one of the oldest and most frequently administered classes of nanomedicines. In the US, there are seven FDA-approved iron nanoparticle reference drug products, of which one also has an approved generic drug product (i.e., sodium ferric gluconate (SFG)). These products are indicated for the treatment of iron deficiency anemia and are administered intravenously. On the molecular level, iron nanomedicines are colloids composed of an iron oxide core with a carbohydrate coating. This formulation makes nanomedicines more complex than conventional small molecule drugs. As such, these products are often referred to as nonbiological complex drugs (e.g., by the nonbiological complex drugs (NBCD) working group) or complex drug products (e.g., by the FDA). Herein, we report a comprehensive study of the physiochemical properties of the iron nanoparticle product SFG. SFG is the single drug for which both an innovator (Ferrlecit) and generic product are available in the US, allowing for comparative studies to be performed. Measurements focused on the iron core of SFG included optical spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), X-ray powder diffraction (XRPD), ⁵⁷Fe Mössbauer spectroscopy, and X-ray absorbance spectroscopy (XAS). The analysis revealed similar ferric-iron-oxide structures. Measurements focused on the carbohydrate shell comprised of the gluconate ligands included forced acid degradation, dynamic light scattering (DLS), analytical ultracentrifugation (AUC), and gel permeation chromatography (GPC). Such analysis revealed differences in composition for the innovator versus the generic SFG. These studies have the potential to contribute to future quality assessment of iron complex products and will inform on a pharmacokinetic study of two therapeutically equivalent iron gluconate products.