eGenesis, a startup co-founded by George Church, has announced that it is now testing genetically modified pig organs on primates to see if they are safe for human use. If successful, this practice could solve the current shortage of human organs for transplantation. While the company is not disclosing which organs are being studied or the monkey species involved, they have declared that the pig organs are the most highly engineered ever created by surgeons.

In recent years, steps have been made towards this goal of successful xenotransplantation. National Institutes of Health researchers have sustained pig hearts inside baboons for two years, alongside the creatures’ own heart. Last year it was also reported that several monkeys were able to survive for around half a year after their hearts were swapped with a pig’s.

In all cases, the organs were genetically engineered to prevent immediate human rejection, offset immune attacks and stop blood clots.

Key problems still remain before human testing can begin. Primate results haven’t been consistent, and it is yet to be disclosed under what conditions regulators will consent to human tests. Despite Church’s announcement in 2017 that “we hope to do transplants to humans within a year”, greater consistency in pig-to-monkey transplant results is needed, and it is yet unknown why some animals survive for months after a transplant and others die quickly.