Toxicological safety evaluation of gadobutrol.

OBJECTIVES: Gadobutrol (Gadovist/Gadavist, Bayer Pharma AG, Berlin, Germany) is a nonionic, macrocyclic, gadolinium-based contrast agent for magnetic resonance imaging of the central nervous system as well as liver and kidneys and for contrast enhancement in magnetic resonance angiography. For risk assessment of the single diagnostic use in humans, the toxicity of this compound was evaluated with a series of preclinical studies. MATERIALS AND METHODS: Preclinical studies into acute, repeated-dose, reproductive, and developmental toxicity as well as genotoxicity, local tolerance, contact-sensitizing potential, and antigenicity were performed. RESULTS: In rodents, lethality was observed after a single intravenous administration of 20 mmol/kg, representing doses at least 2 orders of magnitude higher than the standard single diagnostic dose in humans (0.1 mmol/kg). The no observed adverse effect levels after repeated (daily) administrations over the course of 4 weeks exceeded the single diagnostic dose in humans by a factor of 12 in rats and 10 in dogs (calculated on the basis of body weight), and no unexpected organ toxicity was observed. The most salient finding of repeated dosing in both rats and dogs was vacuolization of renal tubular epithelium without concomitant effect on kidney function, which represents a well-known finding for this class of compounds. Gadobutrol was not teratogenic in rats, rabbits, and monkeys even when given repeatedly during organogenesis at maximum dose levels tested, being 25 to 100 times (based on body weight) above the diagnostic dose in humans. No indications of potential genotoxic, contact allergenic, or immunotoxic effects were observed. In local tolerance testing, gadobutrol was well tolerated after intravenous administration. CONCLUSIONS: Gadobutrol was well tolerated with high safety margins between the single diagnostic dose of 0.1 mmol/kg in humans and the doses showing effects in animal studies.

A review of preclinical safety data for magnevist (gadopentetate dimeglumine) in the context of nephrogenic systemic fibrosis.

OBJECTIVES: Magnevist (gadopentetate dimeglumine, Bayer Healthcare, Bayer) is a gadolinium-based contrast agent (GBCA) for magnetic resonance imaging approved for clinical use in various indications since 1988. A possible association between the administration of GBCAs to patients with severe kidney impairment, and a condition first identified in 2000 and later described as "nephrogenic systemic fibrosis" (NSF), was published in early 2006. In the light of this reported association and the published histologic findings of certain NSF patients, Bayer, with support of external experts, reassessed the preclinical safety data from in vivo studies in healthy rats and dogs that were conducted with Magnevist during the drug development process in the mid-80s. These studies, which were performed according to standard regulatory requirements as defined in pertinent guidelines and which were conducted before the reported association between GBCAs and NSF, were not specifically designed to detect NSF-like lesions. Instead, the intention of this reassessment was to analyze whether the acquired knowledge on NSF would lead to a revised interpretation of the original preclinical data. MATERIALS AND METHODS: Studies on repeat-dose toxicity of Magnevist performed in the mid-80s with healthy rats and dogs were re-evaluated, with special emphasis on the retrospective analysis of morphologic findings which have come to be considered potentially suggestive of NSF. In particular, histologic slides of the skin of repeat-dose toxicity studies were re-examined by Bayer pathologists, with a special focus on the occurrence of morphologic lesions that have subsequently been identified as consistent with NSF. In addition, slides from selected studies were also subjected to a blinded external peer review by an independent international Pathology Working Group. RESULTS: A review of the preclinical data from the repeated-dose toxicity studies provided no evidence for toxicological effects after administration of Magnevist, which could be construed as suggestive of or consistent with NSF. More specifically, histopathology peer reviews of skin samples from repeated-dose toxicity studies with rats and dogs revealed no signs of skin lesions even after repeated high-dose administration to rats of 5.0 mmol Gd/kg of Magnevist (50 times the standard diagnostic dose). CONCLUSIONS: No findings were observed in any of the preclinical studies with Magnevist in healthy rats and dogs which could be characterized as similar to the types of morphologic lesions that have subsequently been identified as consistent with NSF. This preclinical assessment is in contrast to the reported clinical evidence of rare NSF cases in patients with severe kidney impairment after Magnevist administration. The differences between the preclinical models and their predictive limitations with regard to the clinical situation of renally impaired patients are discussed.

Preclinical safety evaluation of Gd-EOB-DTPA (Primovist).

OBJECTIVES: Gadoxetic acid [gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid (Gd-EOB-DTPA); Primovist] is a liver specific contrast agent for magnetic resonance imaging. For risk assessment of the single diagnostic use the toxicity of this compound was assessed. MATERIALS AND METHODS: Studies into acute, repeated-dose, reproductive and developmental toxicity, and local tolerance, contact sensitizing, and genotoxic potential were performed. RESULTS: Lethality was observed after a single intravenous administration at doses 2 orders of magnitude higher than the clinical dose. The no observed adverse effect levels after repeated administration markedly exceeds the single diagnostic dose in humans and no unexpected organ toxicity was observed. No indications of reproductive and developmental toxicity, potential contact allergenic, and genotoxic effects were observed. Gd-EOB-DTPA was well tolerated after intravenous administration. CONCLUSIONS: Gd-EOB-DTPA was well tolerated with high safety margins between the single diagnostic dose and the doses showing adverse effects in animal studies.