Yes it is possible and only about 20 MD schools do it. You would transfer after your 2nd year. However, it is nearly impossible and you have to have a good reason like your mom is dying and you want to be close to her, not just because you want to be an MD.
If you want to be an MD, go to an MD school. Don't be a prick and try to transfer out of a DO school just because you want to be an MD. Go to the caribbean if you want an MD.