I am still not entirely sure this is not an elaborate joke.
The purpose of the NCI Predoctoral to Postdoctoral Fellow Transition Award (F99/K00) is to encourage and retain outstanding graduate students who have demonstrated potential and interest in pursuing careers as independent cancer researchers. The award will facilitate the transition of talented graduate students into successful cancer research postdoctoral appointments, and provide opportunities for career development activities relevant to their long-term career goals of becoming independent cancer researchers.
The need for a transition mechanism that graduate students can apply for is really unclear to me.
Note: These are open to non-citizens on the appropriate visa. This is unlike the NRSA pre- and post-doc fellowships.