Gadobutrol Injection for MRI of the Central Nervous System Approved for Use in the US

A magnetic resonance imaging (MRI) contrast agent called gadobutrol is formulated at a 1.0 molar concentration (mol/L) and was shown to provide a higher concentration (lower volume) compared to other contrast agents used for central nervous system (CNS) imaging.

Bayer HealthCare Pharmaceuticals, Inc. (Wayne, NJ, USA) announced that the Peripheral and Central Nervous System Drugs Advisory Committee to the US Food and Drug Administration (FDA; Silver Spring, MD, USA) voted unanimously that clinical trial and postmarketing data for gadobutrol injection, a macrocyclic 1.0 molar gadolinium-based contrast agent (GBCA), support approval of the product for proposed use in diagnostic MRI in adults and children (two years of age and older) to detect and visualize areas with disrupted blood brain barrier and/or abnormal vascularity of the CNS.

In addition to the vote for approval, Committee members concurred by a vote of 15 to 1 that gadobutrol should be labeled without a nephrogenic systemic fibrosis (NSF) contraindication in the at-risk population. NSF is a very rare but serious disease that affects a small percentage of patients with severe renal impairment who undergo contrast-enhanced MRI. All marketed GBCAs have a boxed warning about the potential for NSF in patients with chronic severe kidney disease or acute kidney injury.

The Bayer announcement further stated that Bayer appreciated the Committee's discussion and suggestions around risk minimization for inadvertent dose misadministration, and would continue to work with the FDA as it finalizes its review of gadobutrol. "Bayer is pleased that the Advisory Committee recognized the totality of the clinical and postmarketing data presented,” said Pamela A. Cyrus, MD, vice president and head of US Medical Affairs, Bayer HealthCare Pharmaceuticals. "If approved by the FDA, Bayer believes that gadobutrol will provide healthcare providers with an additional new option for CNS imaging in the United States.”

Data presented at the January 31, 2011, Advisory Committee meeting included results from two adequate and well-controlled phase 3 studies that confirmed the efficacy and safety of gadobutrol injection in contrast enhanced MRI of the CNS. Prospectively defined primary and secondary endpoints were met in the two studies. The first phase 3 study compared the efficacy of combined gadobutrol-enhanced images plus unenhanced images to unenhanced images alone. The second phase 3 study used a crossover design with an active control, gadoteridol, to also compare the efficacy of the combined gadobutrol-enhanced plus unenhanced images to unenhanced images alone, as well as to confirm noninferiority of combined gadobutrol imaging versus combined gadoteridol imaging.

The results of the first phase 3 study showed that gadobutrol-enhanced images compared to unenhanced images were superior in diagnostic performance and superior for the visualization variables, contrast enhancement, border delineation, and internal morphology. The findings for comparison of unenhanced images compared to gadobutrol-enhanced images were consistent across both phase 3 trials. In the second phase 3 study comparing gadobutrol-enhanced images to images enhanced with the approved contrast agent gadoteridol, gadobutrol was confirmed to be noninferior to gadoteridol with respect to visualization variables, contrast enhancement, border delineation, and internal morphology, as well as the number of lesions detected.

The most common adverse drug reactions observed in phase 2-4 trials for gadobutrol were generally consistent with those of other gadolinium based contrast agents. Across the studies (n = 4549), the most common adverse events (AEs) associated with gadobutrol were: headache (1.5%), nausea (1.2%), injection site reactions (0.6%), dysgeusia (0.5%), feeling hot (0.5%), dizziness (0.4%), vomiting (0.4%), rash (0.3%), pruritis (0.2%), erythema (0.2%), dyspnea (0.2%), and parasthesia (0.1%). During the entire clinical development program of gadobutrol, only isolated reports of serious adverse events were recorded. Overall, serious AEs (including fatal) were observed in 17 (0.4%) of 4,549 patients. One of the 17 serious AEs reported in the gadobutrol group was considered drug-related by the investigator (crystals in urine one day after injection).

The New Drug Application (NDA) for gadobutrol was submitted to the FDA on May 14, 2010. The Advisory Committee's recommendations are not binding, but FDA reviewers will consider the panel's recommendation in its final assessment of the NDA.

Bayer HealthCare Pharmaceuticals, Inc. is the US-based pharmaceuticals operation of Bayer HealthCare LLC, a division of Bayer, AG (Leverkusen, Germany).

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