In 2007, motivated by concerns that pharmaceutical companies were not sharing negative data about what had been learned in clinical trials, Congress established enhanced reporting requirements.
A series of articles published in January 2012 in the British Medical Journal demonstrates that data reporting remains deeply problematic, especially for industry-sponsored trials. (The articles can be found here and are very much worth reading).
A posting Sept. 26 in the Federal Register indicates that the Secretary of HHS has delegated authority to to oversee the reporting process to the FDA. Whether this signals improved monitoring of clinical trial data submissions remains to be seen. One can only hope.