**3. First attempts at human xenotransplantation with primate organs**

During 1963–1964, Reemstma carried out a series of transplants into 13 human patients using chimpanzee kidneys, with one patient surviving 9 months after transplant surgery [9]. The need for these experiments was driven in part by the desperate human organ shortage and lack of alternatives. Cadaveric organs often proved insufficient in quality, and volunteer human kidney donation, high risk at the time, was untenable for ethical and legal reasons. Although chronic dialysis had been demonstrated by the early 1960s, it was not widely available for patient treatment [10]. Therefore, despite the risks, xenotransplantation was considered a potentially viable solution.

Reemstma was not alone in exploring xenotransplantation as a means to overcome critical organ shortages. Hume attempted transplanting a chimpanzee kidney into a human, but the organ failed to show renal function [11]. Hardy and team focused on heart, observing survival for only 2 hours after transplanting a chimpanzee heart into a human patient [12]. Starzl carried out a series of transplants in human patients with baboon kidney [13] and livers, with variable results [14]. These seminal attempts at xenotransplantation showed that although surgical techniques and immunosuppressive drug treatments had greatly improved, they were insufficient to address the multitude of challenges in overcoming the xenorejection response. Indeed, it was nearly a generation later before Bailey used a baboon heart for transplantation into an infant, who survived several weeks after receiving the organ [15].
