UNIVERSAL POST-THAW VIABILITY TESTING OF ALLOGENEIC HEMATOPOIETIC STEM CELL (HPC) COLLECTIONS SHOWS INCREASED RISK OF NON-ENGRAFTMENT AND DELAYED PLATELET ENGRAFTMENT IN PRODUCTS WITH DECREASED POST-THAW VIABLE CD34 (vCD34) YIELD

• Published in: Cytotherapy (Oxford, England) England), 2024-06, Vol.26 (6), p.S102-S103
• Main Authors: Vozniuk, D., Pattarkine, R.S., Ntrivalas, E., Secka, O., Dontsova, M., Vladimirov, A., Feuer, E., Yang, C., Kehn, D., Johnson, A., Wafa, F., Levin, J., Zhu, J., Veliaj, J., Sa, B., Thomsen, M., Elterman, D., Kolovrat, A., Borge, P.D., Roshal, M., Maryamchik, E.
• Format: Article
• Language: English
• Subjects: Engraftment; Hematopoietic Stem Cells; Post-thaw viability
• ISSN: 1465-3249; 1477-2566
• DOI: 10.1016/j.jcyt.2024.03.194

Cryopreservation is associated with loss of viable hematopoietic stem cells. Universal post-thaw viability (PTV) monitoring can help identify collections with a significant drop in viable CD34. However, such programs are not widely established, and there is dearth of information about the expected range of findings, the factors associated with decreased PTV, or the impact of PTV testing on clinical outcomes. The aim of our study was to establish the expected range of PTV in allogeneic collections, to examine the association between PTV and engraftment, and to identify factors associated with PTV drop. We conducted PTV analysis on 227 consecutive allogeneic HPC collections processed at our laboratory between May 2022 and September 2023. Concordance between PTV in cryobags vs cryovials was validated. QC vials of cryopreserved products were thawed 24-72 hours after freezing, and PTV of CD34+ and CD45+ cells assessed. Total vCD34 were calculated as: total nucleated cell count x CD45 viability x % viable CD34 cells among viable CD45 cells. Patient dosing was based on post-thaw values. Median CD34 viability dropped from 99% [99;100] fresh to 80% [69;88] post-thaw, and 55 out of 227 (24%) products had > 35% drop total vCD34. Recovery of vCD34 followed bell-shaped distribution, suggesting involvement of multiple independent factors. Products with >35% drop in vCD34 yield were associated with non-engraftment for both neutrophils (Fisher p=0.013, OR 23.6 & 95% CI 1.20-464.2), and platelets (Fisher p=0.004, OR 16.2 & 95% CI 1.8-142.5). Engrafted patients had a median vCD34 change of -22% [-34;-9], compared to -41% [-72;-32] for those who failed to engraft. Post-thaw vCD34 dose was significantly associated with delayed platelet engraftment (t-test p=0.027), but not ANC engraftment (t-test p=0.59). Patients who achieved platelet engraftment within 30 days received on average 6.25x10^6 vCD34/kg (SD 2.02), while patients who failed to do so received 5.38x10^6 vCD34/kg (SD 2.42). Products cryopreserved > 36 hours from collection were at a higher risk of experiencing >35% drop in vCD34. (Fisher p = 0.011, OR 2.16, CI 1.16 – 3.99). The universal post-thaw viability program has the potential to identify HPC products at risk for non-engraftment and delayed engraftment. Decreasing time to cryopreservation to < 36 hours may improve vCD34.