The First 500 Kidneys Rescued Using Subnormothermic Acellular Perfusion (SNAP) at a Centralized Facility

Background: Despite successful international programs, renal subnormothermic acellular perfusion (SNAP) has yet to be adopted in the US. Barriers to adoption include resource availability and broad utilization of hypothermic machine perfusion (HMP). Unlike static cold storage or HMP, SNAP provides functional allograft assessment (Table 1), while supporting cellular metabolism, reducing oxidative stress, and delivering nutrients and therapeutics, which can improve function and prolong safe out-of-body times.
Methods: To overcome obstacles to utilizing renal SNAP in the US, the first dedicated center to rescue hard-to-place (HTP) kidneys was constructed at the Purdue University Research Park in West Lafayette, Indiana, in late 2022. Organized as a public benefit company, this center was designed to provide SNAP as an assessment and repair center (ARC) offering a second look at HTP kidneys not available through current preservation methods. Pre-clinical testing was performed for over a year, with more than 100 abattoir swine and 200 human research kidneys. Published clinical SNAP protocols were compared side-by-side for perfusate composition, equipment setup and perfusion protocols. The SNAP protocol included the validated acellular perfusate described by Minor et al. and the hardware described by Hosgood et. al. Central IRB approval was granted by WCG in March 2024, to begin the first multi-center clinical SNAP rescue study in the US (“OPTIMAL,” NCT06263023).
Results: From April 20th, 2024, to March 30th, 2026, 555 HTP kidneys were transported to the centralized ARC with the intent for SNAP preservation, assessment, and subsequent transplantation. Median CIT prior to arrival was 25.25 hours (max 57 hrs). 500 (90%) of these kidneys were transplanted after successful NMP by 30 transplant centers, with the first graft rescued on April 20th, 2024. Characteristics of HTP kidneys transplanted after NMP can be found in Table 2.
Discussion: NMP can reduce kidney discard rates by providing objective functional organ assessment. Moreover, NMP allows for extended preservation time, enabling improved logistical planning and broader sharing of donor kidneys. By encouraging the utilization of marginal kidneys, a centralized NMP center is a feasible model to increase transplantation rates of HTP kidneys.