Novel cationic lipid compound (1)

The present invention relates to lipid compounds that can be used alone or in combination with other lipid components such as neutral lipids, spot lipids, steroids and/or analogs thereof, and/or polymer-conjugated lipids to form lipid nanoparticles for the delivery of therapeutic and/or prophylactic agents. In some examples, lipid nanoparticles are used to deliver nucleic acids, such as messenger RNA and/or antisense RNA. Methods of using such lipid nanoparticles to treat and/or prevent various diseases are also provided. In one embodiment, there is provided a compound having the structure of the following formula (I): or a salt thereof or an isomer thereof or an N-oxide thereof, where X is as defined herein, and a pharmaceutical composition comprising one or more of the compounds of the foregoing structural formula (I) and a therapeutic and/or prophylactic agent. In some embodiments, the pharmaceutical composition further includes one or more components selected from the group consisting of neutral lipids, c