Purpose: Iron supplementation for the treatment of Anemia: To treat iron deficiency anemia, patients are prescribed iron supplements to replenish the body’s diminished iron supply. Iron supplementation can be administered either orally or intravenously. However, some iron anemia associated diseases, such as chronic kidney disease (CKD) associated iron anemia, are only receptive to intravenous (IV) therapies.
In the US, the FDA has approved six reference and one generic IV iron formulations to treat CKD associated iron-deficiency anemia. These formulations are all colloidal iron nanoparticles and classed as complex drug products. The product for which both an innovator and generic are available in the US is sodium ferric gluconate (SFG) (brand - Ferrlecit, generic - Sodium Ferric Gluconate). These formulations function by delivering iron to a protein in the plasma called transferrin. Transferrin delivers iron to cells to be used for cellular processes. If too much iron is released to blood plasma, transferrin becomes saturated with iron, and the remaining iron is delivered non-specifically to the cells resulting in toxicity.
Compared to conventional small molecule drugs, an extensive functional regulatory standard for generic nanoparticle drug approval has yet to be fully established. Given the complex nature of nanotechnology, the regulatory agencies may require analysis of nanoparticle-based drug products using the state-of-the-art tools. It is important to understand which in vitro measures are in vivo predictive during generic drug approval. To attempt to fill these gaps, we have conducted a comprehensive suite of physicochemical measures, for brand and generic SFG, beyond those currently required by regulatory agencies. This approach will (1) identify key in vitro measures to correlate with the in vivo data that we obtain from our ongoing clinical trial and (2) inform regulatory agencies of additional in vitro measures that may contribute to the formation of a more product specific guidances.
Methods: Particle size: Particle size was determined by dynamic light scattering (DLS) where corner scattering of undiluted SFG samples were measured in quartz cuvettes at 22° C, 90° angle, using on a DLS Photocorrelation Spectrometer (PhotoCor Corp inc.) with helium neon laser. Data processed DynaLS software.
Acid Stability: Acid stability was determined via forced acid degradation. Samples were diluted to 10 mg Fe/ L in 0.9% NaCl, 0.24 M HCl in screw-capped quartz cuvettes. Full absorbance scans (220 - 800 nm) were taken on a Lambda 25 spectrometer from 0 to 22 hrs every 2 hours. The absorbances at 287 nm were plotted against time and the first order decay half-life was calculated.
Molecular Weight Distribution: Brand and generic SFG samples were diluted 40 times with mobile phase solution (aqueous solution of sodium azide (0.02 w/v %) and 0.01% brand SFG at pH 7.0). Pullulan polysaccharide standards (21 kDa to 805 kDa) were used to generate a standard calibration curve. Gel permutation chromatography was performed on a 300 × 7.8 mm Toso Haas TSK Gel G40000SWXL column (spherical silica with a particle size of 8 μm and a pore size of 25 nm) and samples were analyzed using a refractive index detector.
Mineral Identity: X-Ray measurements of non-pulverized dried solutions were performed with an XRD 3000TT using Copper-radiation (1.54178 A, 40kV, 30mV) in Bragg Bretana configuration (automatic divergence slit, angular rate 0.18°/min).
Iron Core Oxidation State: Fresh SFG samples were diluted with a 50% (v/v) solution of glycerol and flash frozen in liquid nitrogen prior to analysis via EPR. The samples were obtained on a Bruker EMX EPR spectrometer. The EPR parameters were as follows: temperature: 12 K, microwave frequency: 9.43 GHz, microwave power: 20 mW, modulation amplitude 10 G, sweep time: 41.9 s.
Total Iron: Total Iron content was determined by diluting SFG samples to 20 and 40 mg Fe/ L in water. Samples were then digested in 6% HNO3 and heated overnight at 80°C. Iron concentration was measured via Inductively coupled plasma mass spectrometry (Agilent 7700).
Results: Differences in particle size, molecular weight distribution (Table 1), and acid stability (Figure 1) were identified. Data collected for other measures, including total iron content, mineral identify, and iron oxidation state do not show differences.
Conclusion: Our results show several physiochemical property differences (particle size, molecular weight distribution, and acid stability) between brand and generic sodium ferric gluconate. Whether or not these differences in physicochemical characterization has any impact on in vivo pharmacokinetics of various iron species will assessed by the ongoing clinical study comparing total iron, transferrin-bound iron, protein-bound iron and labile iron between brand and generic SFG in healthy volunteers.
Marc Taraban– Research Assistant Professor, University of Maryland School of Pharmacy
Heather Neu– Postdoctoral Fellow, University of Maryland, School of Pharmacy, Baltimore, Maryland
Peter Langguth– Professor, Johannes Gutenberg University Mainz, Mainz, Rheinland-Pfalz
James Polli– Professor and Ralph F. Shangraw/Noxell Endowed Chair in Industrial Pharmacy and Pharmaceutics, University of Maryland School of Pharmacy, Maryland
Sarah Michel– Professor, University of Maryland School of Pharmacy