A New York scientist's 7-year attempt to patent a human–animal chimera has failed because the hybrid could be too human. Stuart Newman of New York Medical College and his collaborator Jeremy Rifkin claim a victory nonetheless because they never intended to make the animal anyway. Rather, as opponents of patents on living organisms, they simply wanted to find out whether such an invention would be patentable and prevent others from profiting from similar inventions.

Newman's application described a technique for combining human embryo cells with embryonic cells from another animal to create a chimera with many potential medical applications. “Back in 1997, we made claims for the chimera's intended use that at the time seemed quite wild but are much more feasible today.” For example, given the current prohibitive legislation concerning the use of human embryos for medical research, one likely use of this technology would be to enable the study of stem-cell therapies for neurodegenerative disorders. The chimeras could also be used to generate bone marrow and neuronal stem cells for reparative transplantation. Indeed, studies with a sheep–goat hybrid have already shown that transplanted cells from the chimeric animal had reduced ability to provoke immunorejection in the recipient animal. Newman notes that tissues from a human hybrid that have become more 'humanized' might be more effective for transplantation. He also proposed that if the chimeras can be grown to full-term, they could be used to facilitate drug toxicity testing: “The prohibitions on doing drug testing and cardiovascular stress experiments would be much less than they currently are for experiments on humans and so the technology could be useful to drug companies,” he says.

The [US patent] office still lacks a criterion for determining how human a genetically engineered organism is.

The crucial bone of contention for the US Patent and Trademark Office (USPTO), however, was exactly how human the hybrid would be, and the office still lacks a criterion for determining how human a genetically engineered organism is. “But if you could genetically engineer the chimera so that the human component will be a known percentage of the organism then the USPTO might be better satisfied,” says Newman. “I don't think that the rejection of this patent will impede research in the field. I do hope, however, that it stimulates legislative guidelines. With commercial incentive alone it is only a matter of time before such an organism is made.”