Xenotransplantation is still just around the corner. But maybe it won't always be...

 Xenotransplantation, e.g.. transplanting pig kidneys into humans, sometimes seems like it is just around the corner and always will be.  But a recent review in the journal Xenotransplantation suggests that we might see clinical trials in the almost foreseeable future:

Recent progress and remaining hurdles toward clinical xenotransplantation  

by Raphael P.H. Meier, Alban Longchamp, Muhammad Mohiuddin, Oriol Manuel, Georgios Vrakas, Daniel G. Maluf, Leo H. Buhler, Yannick D. Muller, Manuel Pascual

First published: 23 March 2021 https://doi.org/10.1111/xen.12681

"Background: Xenotransplantation has made tremendous progress over the last decade.

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Results: Life sustaining genetically modified kidney xenografts can now last for approximately 500 days and orthotopic heart xenografts for 200 days in non-human primates. Anti-swine specific antibody screening, preemptive desensitization protocols, complement inhibition and targeted immunosuppression are currently being adapted to xenotransplantation with the hope to achieve better control of antibody-mediated rejection (AMR) and improve xenograft longevity. These newest advances could probably facilitate future clinical trials, a significant step for the medical community, given that dialysis remains difficult for many patients and can have prohibitive costs. Performing a successful pig-to-human clinical kidney xenograft, that could last for more than a year after transplant, seems feasible but it still has significant potential hurdles to overcome. The risk/benefit balance is progressively reaching an acceptable equilibrium for future human recipients, e.g. those with a life expectancy inferior to two years. The ultimate question at this stage would be to determine if a “proof of concept” in humans is desirable, or whether further experimental/pre-clinical advances are still needed to demonstrate longer xenograft survival in non-human primates."

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In Greek mythology, a chimera is an animal with a lion's head, a goat's body, and a serpent's tail. In medicine the term has been adopted to mean a person who has cells with two different genetic origins (so twins may come to share some of their twin's cells in the placenta).  Here's the picture from the cover of the journal  in which the above article appears: