Developmental toxicity study of mangafodipir trisodium injection (MnDPDP) in New Zealand white rabbits

Composition-Tunable Ultrasmall Manganese Ferrite Nanoparticles: Insights into their In Vivo T1 Contrast Efficacy

The development of a highly efficient, low-toxicity, ultrasmall ferrite nanoparticle-based T₁ contrast agent for high-resolution magnetic resonance imaging (MRI) is highly desirable. However, the correlations between the chemical compositions, in vitro T₁ relaxivities, in vivo nano-bio interactions and toxicities remain unclear, which has been a challenge in optimizing the in vivo T₁ contrast efficacy.

Methods: Ultrasmall (3 nm) manganese ferrite nanoparticles (Mn_xFe_3-xO₄) with different doping concentrations of the manganese ions (x = 0.32, 0.37, 0.75, 1, 1.23 and 1.57) were used as a model system to investigate the composition-dependence of the in vivo T₁ contrast efficacy. The efficacy of liver-specific contrast-enhanced MRI was assessed through systematic multiple factor analysis, which included the in vitro T₁ relaxivity, in vivo MRI contrast enhancement, pharmacokinetic profiles (blood half-life time, biodistribution) and biosafety evaluations (in vitro cytotoxicity testing, in vivo blood routine examination, in vivo blood biochemistry testing and H&E staining to examine the liver).

Results: With increasing Mn doping, the T₁ relaxivities initially increased to their highest value of 10.35 mM^-1s^-1, which was obtained for Mn_0.75Fe_2.25O₄, and then the values decreased to 7.64 m M^-1s^-1, which was obtained for the Mn_1.57Fe_1.43O₄ nanoparticles. Nearly linear increases in the in vivo MRI signals (ΔSNR) and biodistributions (accumulation in the liver) of the Mn_xFe_3-xO₄ nanoparticles were observed for increasing levels of Mn doping. However, both the in vitro and in vivo biosafety evaluations suggested that Mn_xFe_3-xO₄ nanoparticles with high Mn-doping levels (x > 1) can induce significant toxicity.

Conclusion: The systematic multiple factor assessment indicated that the Mn_xFe_3-xO₄ (x = 0.75-1) nanoparticles were the optimal T₁ contrast agents with higher in vivo efficacies for liver-specific MRI than those of the other compositions of the Mn_xFe_3-xO₄ nanoparticles. Our work provides insight into the optimization of ultrasmall ferrite nanoparticle-based T₁ contrast agents by tuning their compositions and promotes the translation of these ultrasmall ferrite nanoparticles for clinical use of high-performance contrast-enhanced MRI.

Is omphalocele a non-specific malformation in New Zealand White rabbits?

We evaluated the incidence of omphalocele, a malformation that occurs sporadically in many studies. We assembled data on external malformations using all treatment groups from every study published in three major journals over the past 35 years using New Zealand White rabbits. Fifty-eight papers were included: 4905 litters and 36,977 fetuses. Omphalocele was reported in 43% and was among the most common defects, occurring at a rate of 1.10% (litter) and 0.16% (fetus). The defect did not appear to be treatment-related, although it may have been in two studies, based on rate and dose-responsiveness. Removing these two studies from the analysis, the defect was still prevalent (0.77% litter, 0.11% fetal incidence). Three studies evaluated the effects of food restriction and omphalocele was observed with food restriction in two of them, suggesting that decreased maternal weight gain or food consumption may be causal. Otherwise, it appears to be spontaneous and common.

Carcinogenicity, mutagenicity and teratogenicity of manganese compounds

Manganese, an essential trace element, is one of the most used metals in the industry. Recently, several new manganese compounds have been introduced as fungicide, as antiknock agent in petrol and as contrasting agent in nuclear magnetic resonance tomography. Manganese displays a somewhat unique behaviour with regard to its toxicity. It is relatively non-toxic to the adult organism except to the brain where it causes Parkinson-like symptoms when inhaled even at moderate amounts over longer periods of time. Relatively high doses of manganese affect DNA replication and repair in bacteria and causes mutations in microorganism and mammalian cells although the Ames test does not appear to be particularly responsive to manganese. In mammalian cells, manganese causes DNA damage and chromosome aberrations. Information on organic manganese derivatives is still insufficient. Large amounts of manganese affect fertility in mammals and are toxic to the embryo and foetus. The fungicide MANEB and the contrasting agent MnDPDP also can be embryotoxic, but the latter only at doses much higher than those clinically employed. Information on the anti-knock agent MMT is inadequate. On the other hand, manganese deficiency can also affect fertility and be teratogenic. Information on cancer due to manganese is scanty but the results available do not indicate that inorganic manganese is carcinogenic. More information is desirable with regard to the organic manganese derivatives. It may surprise that an agent that causes mutations is not also carcinogenic. The experience with manganese shows that conclusions with regard to carcinogenicity of an agent based on the observation of mutations are subject to uncertainties. Altogether, it appears that, because of the very high doses at which positive effects have been found, manganese would not represent a significant carcinogenic risk to the population and workers. Care must, however, be exercised with respect to central-nervous symptoms after chronic exposure and with respect to effects on the embryo. Pregnant women should not be exposed to manganese at the work place.

Safety and efficacy of mangafodipir trisodium (MnDPDP) injection for hepatic MRI in adults: results of the U.S. multicenter phase III clinical trials (safety)

The short-term safety of mangafodipir trisodium (MnDPDP) injection was studied in 546 adults with known or suspected focal liver lesions. An initial contrast-enhanced computed tomography examination was followed by unenhanced magnetic resonance imaging (MRI), injection of MnDPDP (5 micromol/kg), and enhanced MRI. Adverse events were reported for 23% of the patients; most were mild to moderate in intensity, did not require treatment, and were not drug related. The most commonly reported adverse events were nausea (7%) and headache (4%). The incidence of serious adverse events was low (nine events in six patients) and not drug related. Injection-associated discomfort was reported for 69% of the patients, and the most commonly reported discomforts included heat (49%) and flushing (33%). Changes in laboratory values and vital signs were generally transient, were not clinically significant, and did not require treatment. There were no clinically significant short-term risks from exposure to MnDPDP.