Ann: PAT-DX1 Crosses Blood Brain Barrier to Reduce Tumour Size, page-87

Cell penetrating antibodies have been around for a long time (more than 20 years), but nobody seems to have been able to make then into a viable therapeutic. The basic problem is the antibodies have to undergo endocytosis via the clathrin or caveolar systems and escape degradation (the fate of most large proteins endocytosed). It is not well understood how this occurs. People have tried to use other delivery systems like liposomes, but that introduces another variable.

Getting across the blood brain barrier is also not easy as you need specific transport of the antibody into the brain. Even targeting cancer cell surface receptors with an antibody is difficult because so many cancers have a poor blood supply and lymph drainage so it is hard to get the antibody to the cancer via passive diffusion. As Barbie would say "cancer is hard, lets go shopping".

All of this doesn't mean that what they have is not going to work (it is quite an interesting idea), but they are trying to solve multiple problems at once. I would like to reserve judgement until I see the scientific work behind this announcement.