UC San Diego Health San Diego, California, United States
Background/Case Studies: Donor lymphocyte infusions (DLI) are an adjunct therapy used after allogeneic hematopoietic cell transplantation (HCT) to reinforce engraftment and graft-versus-leukemia effects. In cases where the donor may not be available to re-donate, the collected product is cryopreserved in DLI doses (cDLI).
When the recipient’s weight or disease status changes, the cDLI dose may no longer align with the desired dose. Moreover, recent changes to clinical guidelines have lowered many DLI doses. To utilize cDLI products and adapt them to new dosing algorithms, we developed a procedure to thaw, dilute, and dose (TDD) cryopreserved apheresis (cAPH) products based on our process for thawing and diluting cord blood units (CBU).
Study
Design/Methods: To adapt the CBU thaw and dilute procedure for DLI TDD, we developed standardized dosing calculations. All cases of DLI that required re-dosing involved using a significantly smaller amount of the cAPH. To achieve the intended cell dose (CD3+ cells/kg), lab staff determined the volume needed from the original cAPH, the volume of diluent, and the final volume for infusion. cAPH products are thawed and diluted with Dextran40 and 20% human albumin in a 1:4 ratio. A 5-minute rest period occurs for cells to equilibrate to a portion of the diluent before full dilution.
We also established an expiration time for the thawed product in order to ensure adequate viability of the cells after minimal manipulation. To assess stability and cell viability over 8 hours, a cAPH product was thawed and diluted, and calculated dose volumes were placed in 9 syringes. Post-thaw testing performed at Time 0 and every subsequent hour for 8 hours included white blood cell (WBC) counts, trypan blue viability, and flow cytometry (CD45, CD34, CD3).
To verify the accuracy of the dosing calculations, 10 previous TDD DLI products for patients were examined to ensure the actual dose was within 10% of the intended dose.
Results/Findings: WBC counts were unchanged from Time 0 to 8 hours, and all viabilities were ≥80%; even increasing with time from thaw (Table 1). Among patient products, 9/10 were within 10% of the intended dose (CD3+ cells/kg) and one showed a 10.4% difference from intended. All sterility cultures from previous thaw and dose infusions were negative for growth. Conclusions: This study demonstrated the ability to use existing cAPH products to provide DLIs that are stable, viable, and contain accurate doses tailored to new clinical targets. The products are viable for at least 8 hours, which in our health system will allow for routine transport and delivery for outpatient DLI infusions. This process enables older products to be adapted to new clinical and logistical needs.
