Ferumoxytol is an iron-based agent approved for the treatment of anemia in patients with renal failure or during pregnancy. In recent years, including at UW-Madison, it is increasingly used (off-label) as a positive blood pool CA due to its favorable MRI properties (shortening T1 and T2 relaxation times) and long intravascular half-life of 14-15 h. This makes it well-suited for cardiovascular imaging, such as magnetic resonance angiography (MRA) and 4D-flow MRI. Ferumoxytol also has many other potential research applications, like cerebral neoplasms, liver lesions, cancer staging, lymph node detection and inflammation. Furthermore, it is commonly used as an off-label alternative to gadolinium-based CA’s in patients with contraindications to gadolinium. Moreover, it has drawn increasing interest for this application due to growing concerns regarding the safety of gadolinium-based contrast agents (GBCA).
Until recently ferumoxytol was only available through AMAG Pharmaceutical as Feraheme®. Last year, Sandoz released their own generic version of ferumoxytol. The Sandoz agent is expected to be less expensive, while being pharmacologically equivalent. Thus, switching to the Sandoz ferumoxytol agent could lead to potential cost savings. However, it is unknown whether the magnetic properties, in terms of T1 and T2/T2* relaxivity, are equal across both agents. While the MRI properties of Feraheme (AMAG) have been published by our group there are no publications in the literature documenting the MRI properties of the Sandoz agent. We have contacted the Sandoz scientific representatives and they have no MRI data on the Sandoz formulation of ferumoxytol.
Additionally, the optimal dose of ferumoxytol is not well understood. In a recent review of 3215 patients’ doses varied between 1-11 mg/kg and no severe adverse reactions were reported. At our facility, the typical dose of ferumoxytol for MR is 3-5 mg/kg, based on anecdotal experience and one study comparing 2 vs 4mg/kg suggest that a dose of 4mg/kg of ferumoxytol is superior for abdominal MRA. However, 2mg/kg of ferumoxytol also demonstrated good qualitative imaging scores as an alternative to the higher dose. A recent study by Stoumpos et al. found an improvement in signal with AMAG ferumoxytol doses up to 3 mg/kg with no significant benefit (or even loss in signal) with higher doses of contrast in abdominal MRA. Their study did not consider different flip angles, however.
Hence, the primary aim of this study is to compare the magnetic properties of both ferumoxytol agents (AMAG Pharmaceuticals vs. Sandoz) and the secondary aim is to establish the optimal dose of both ferumoxytol agents for typical applications.