Hematopoietic Stem/Progenitor Cells and Engineering: 20-YEAR HEMATOPOIETIC PROGENITOR CELL STABILITY – THE MAYO CLINIC EXPERIENCE

ABSTRACT

Background & Aim: Hematopoietic progenitor cells (HPCs) are infused for hematopoietic reconstitution in the setting of malignancy and inherited or acquired hematological deficiencies. Given the global COVID-19 pandemic, the recommendation was made to cryopreserve all allogeneic HPCs to protect recipients by allowing for subclinical cases of infection to present prior to infusion. As such, consideration of HPC stability programs (SP) and their rigor has risen. The goal of a SP is to prove the rigor of a transplant program’s cryopreservation and storage standard operating procedures so that sufficient HPC viability and potency are maintained for engraftment. SPs are also required by accreditation agencies such as AABB and FACT. Many HPC SP have validated product expirations out to 10 years. Here we share our SP to 20 years with ongoing validation for 30-year expiration. Methods, Results & Conclusion: Program Design: Current testing frequency of our SP is within the first year, and then at three-year intervals (3, 6, 9, 12, 15, 19, 21). Our rolling SP includes 2 additional (Figure Presented) Fig. 1.Current vs proposed HPC product testing and cryopreseveration schema. samples tested at 0, 5, & 9 years, then at 3-year intervals (12, 15, 19, 21, 24, 27, 30). SP samples are collected from donors requiring additional days to reach their goal but are in excess at the conclusion of collection (e.g., Day 1 collection 4.5e6 CD34+ cells/Kg, goal 5e6 CD34+ cells/ Kg). Samples are collected on a quarterly basis with ten 1mL cryovials being drawn (Figure 1). CD3+ and CD34+ viabilities are tested after cryopreservation with an acceptable threshold set at ≥75% for both. Conclusion: We are validating our SP up to 20 years with intention to validate to 30 years. Thus far, our SP reveals product age has no to low correlation with engraftment, suggesting maintenance of potency over time in a cryopreservative of 10% DMSO, 10% plasma, and 30% PlasmaLyte-A with a final cell concentration of ≤3×108 NC/mL (Figure 2). Successful engraftment has been seen in all recipients. Transplant programs should modify testing frequency, acceptance criteria, and product expiration to meet individual need while working towards standardization in the field. Given the frequency of DLIs and 2nd/3rd transplants at the Mayo Clinic, a 30-year SP reflects the need of our transplant program.(Figure Presented)Fig. 2 . ANC and platelet engraftment dates for ≥10-year-old HPC products