It's highly unethical to subject dying patients to a possibly toxic drug with the lame excuse "their lives weren't worth much anyways".
Besides, doing a Phase One study on sick people cannot possibly give you any useful indication on safe dosages and side effects: if a patient complains of, say, headaches, is it due to their illness, or is it a side effect of the drug being tested ?
The confounding factors are certain to drown the signal.