Pharmacotherapeutic group: Paramagnetic contrast media, ATC code: V08C A09
Mechanism of action
The contrast-enhancing effect is mediated by gadobutrol, the non-ionic complex consisting of gadolinium (III) and the macrocyclic ligand dihydroxy-hydroxymethylpropyl-tetraazacyclododecane-triacetic acid (butrol).
Pharmacodynamic effects
The relaxivity of gadobutrol, measured in vitro in human blood/plasma at physiological conditions and at clinically relevant field strengths (1.5 and 3.0 T), is in the range of 3.47 – 4.97 L/mmol/sec.
In clinical doses, the pronounced relaxivity of gadobutrol leads to a shortening of the relaxation times of protons in tissue water.
The stability of the gadobutrol complex has been studied in vitro at physiological conditions (in native human serum, at pH 7.4 and 37°C) over the time period of 15 days. The amounts of released gadolinium ions from gadobutrol were below the limit of quantification of 0.1 mol% of total gadolinium demonstrating the high complex stability of gadobutrol under the tested conditions.
Clinical efficacy
In a pivotal phase III liver study average sensitivity in combined pre and post-contrast MRI for gadobutrol-treated patients was 79 % and specificity was 81 % for lesion detection and classification of suspected malignant liver lesions (patient-based analysis).
In a pivotal phase III kidney study average sensitivity was 91 % (patient-based analysis) and 85 % (lesion-based analysis) for classification of malignant and benign renal lesions. Average specificity in a patient-based analysis was 52 % and in a lesion-based analysis 82 %.
The increase of sensitivity from pre-contrast to combined pre and post-contrast MRI for gadobutrol-treated patients was 33 % in the liver study (patient-based analysis) and 18 % in the kidney study (patient-based analysis as well as lesion-based analysis). The increase in specificity from pre-contrast to combined pre and post-contrast MRI was 9 % in the liver study (patient-based analysis) while there was no increase in specificity in the kidney study (patient-based analysis as well as lesion-based analysis).
All results are average results obtained in blinded reader studies.
In a study designed as an intra-individual, crossover comparison, gadobutrol was compared to gadoterate meglumine (both at 0.1 mmol/kg) in the visualization of cerebral neoplastic enhancing lesions in 132 patients.
The primary efficacy endpoint was the overall preference for either gadobutrol or gadoterate meglumine by the median blinded reader. Superiority of gadobutrol was demonstrated by a p-value of 0.0004. In detail, a preference of gadobutrol was given for 42 patients (32 %) compared to an overall preference for gadoterate meglumine for 16 patients (12 %). For 74 patients (56 %) no preference for one or the other contrast agent was given.
For the secondary variables lesion-to-brain ratio was found to be statistically significantly higher for gadobutrol (p < 0.0003). Percent of enhancement was higher with gadobutrol compared to gadoterate meglumine, with a statistically significant difference for the blinded reader (p < 0.0003).
Contrast-to-noise ratio, showed a higher mean value following gadobutrol (129) compared to gadoterate meglumine (98). The difference was not statistically significant.
In a study designed as an intra-individual, crossover comparison, gadobutrol at a reduced dose of 0.075 mmol/kg was compared to gadoterate meglumine at its standard dose of 0.1 mmol/kg for contrast enhanced MRI of the CNS in 141 patients with enhancing CNS lesions on gadoterate meglumine enhanced MRI. The primary variables included lesion contrast enhancement, lesion morphology, and lesion border delineation. Images were analysed by three independent blinded readers. Noninferiority to gadoterate meglumine for the degree of improvement over unenhanced imaging was demonstrated for all three primary variables (at least 80% of effect retained) based on the average reader. The mean number of lesions detected by gadobutrol (2.14) and gadoterate (2.06) were similar.
Paediatric population
Two single dose phase I/III studies in 138 paediatric subjects scheduled for CE-MRI of CNS, liver and kidneys or CE-MRA and in 44 subjects aged 0 -< 2 years (including term neonates) scheduled to undergo routine CE-MRI of any body region have been performed. Diagnostic efficacy and an increase in diagnostic confidence was demonstrated for all parameters evaluated in the studies and there was no difference among the paediatric age groups and when compared to adults. Gadobutrol was well tolerated in these studies with the same safety profile of gadobutrol as in adults.
Clinical Safety
The type and frequency of adverse reactions following the administration of gadobutrol in various indications was evaluated in a large international prospective non-interventional trial (GARDIAN). The safety population encompassed 23,708 patients of all age groups including children (n = 1,142; 4.8%) and elderly (n = 4,330; 18.3% between the ages of 65 and < 80 and n = 526; 2.2% of ≥ 80 years of age). Median age was 51.9 years.
Two hundred and two patients (0.9 %) reported overall 251 adverse events (AEs), and 170 (0.7%) reported 215 events categorized as adverse drug reactions (ADRs), the majority (97.7%) of which were mild or moderate in intensity.
Most commonly documented ADRs were nausea (0.3 %), vomiting (0.1 %) and dizziness (0.1 %). ADR rates were 0.9 % in females and 0.6 % in males. There were no differences in ADR rates according to the dose of gadobutrol. Four of the 170 patients with ADRs (0.02 %) experienced a serious adverse event, with one event (Anaphylactic shock) leading to fatal outcome.
In the paediatric population AEs were reported in 8 of the 1,142 (0.7%) children. In six children these AEs were classified as ADRs (0.5%).
Renal impairment
In a prospective pharmacoepidemiologic study (GRIP) to assess the magnitude of potential risk for development of NSF in renally impaired patients, 908 patients with varying degrees of renal impairment received gadobutrol at the standard approved dose for CE-MRI.
All patients, including 234 with severe renal impairment (eGFR <30 mL/min/1.73 m2) who had not received other GBCAs were followed over the course of two years for signs and symptoms of NSF. No patient enrolled in the study developed NSF.