Insiders CANNOT trade stock on information that is not released to the public. Just because they know the offering is coming and the public doesn't they can not act on that information. Also insiders can only trade at certain times usually the middle month of the quarter. This is because the first month of the quarter we are still waiting for the last quarter's results and the insider know them and have an idea what the PPS will do when the news is released. In the last month of the quarter they have a good idea if that quarter is going to be a good one as it comes to a close. They don't just trade in the middle month only but it is the safest time for them and they stay close to that time period.