Phase I clinical trials of MRX-115: A new ultrasound contrast agent

RATIONALE AND OBJECTIVES. Stabilized microbubbles are under development as contrast agents for medical ultrasound. The authors report the results of Phase I clinical trials of a new ultrasound contrast agent based on lipid- encapsulated perfluorocarbon gas microbubbles. METHODS. Lipids encapsulating perfluoropropane gas (Aerosomes® MRX-115, ImaRx Pharmaceutical Corp., Tucson, AZ) were evaluated in Phase I clinical trials. Two separate studies were performed. The first was a single escalating-dose study (n = 30 subjects), and the second was a multiple-dose study (n = 18 subjects) with rechallenge in several subjects (n = 4) after 21 days. Echocardiographic examinations were performed before and after contrast agent for each test drug administration for both studies, with the exception of the rechallenge group. Doses tested in the single-dose study ranged from 0.005 mL/kg to 0.100 mL/kg body weight. In the multiple-dose study, five doses of 0.005 mL/kg to 0.030 mL/kg (0.025-0.150 mL/kg total dose) were evaluated. Studies were single-masked, placebo-controlled, and safety assessment and adverse events were monitored. RESULTS. All doses in both studies were well tolerated with no treatment-related changes in safety measures for either study. Left ventricular cavity and myocardial enhancement were seen with all doses of MRX-115. CONCLUSIONS. MRX-115 is a promising new intravascular ultrasound contrast agent that was safe and well tolerated at the doses evaluated in these studies.