I have written elsewhere (Journal of Law, Medicine, and Ethics, 2007) on the ethics of phase 0 studies, and a recent cluster of new articles on their ethics was published in the journal Clinical Cancer Research. In general, I have tended to support such studies as a way of reducing risk and uncertainty in phase 1 studies.
But the August issue of Nature Medicine contains a small news report describing ongoing controversies about whether such studies accurately predict drug behavior at higher doses. One company that is marketing itself as a supplier of equipment for phase 0 studies claims such studies are highly predictive, but according to the report, chemists and others question their validity, and fault the company for not releasing "specific criteria" they use to support their claim that phase 0 studies are predictive.
The upshot seems to be: 1- buyer beware on phase 0 studies, and 2- companies that pursue phase 0 studies should publish results (few probably do-- they contain sensitive proprietary information) so that policy makers and others can evaluate their value. (photo credit: e-chan photo of Kusama Yayoi artwork, 2008)