Resolving the daratumumab interference with blood compatibility testing

Abstract

BACKGROUND Daratumumab (DARA), a promising novel therapy for multiple myeloma, is an IgG1κ monoclonal antibody that recognizes CD38 on myeloma cells. During routine compatibility testing, we observed that the plasma of five of five DARA‐treated patients demonstrated a positive antibody screen and panreactivity on red blood cell (RBC) panel testing. We hypothesized that the observed panreactivity reflected DARA binding to CD38 on reagent RBCs, and we investigated methods to prevent this binding. STUDY DESIGN AND METHODS DARA binding to CD38+ or CD38– HL60 cells was assessed by flow cytometry. To remove cell surface CD38, cells were incubated with dithiothreitol (DTT) or trypsin. Soluble CD38 or anti‐DARA was used to neutralize DARA in solution. Routine blood bank serologic methods were used to test samples from DARA‐treated patients and normal plasma samples spiked with DARA and/or alloantibodies. RESULTS Normal plasma samples spiked with DARA (0.1‐10 µg/mL) and incubated with reagent RBCs recapitulated the interference observed with samples from DARA‐treated patients. Flow cytometry experiments confirmed DARA binding to CD38+ HL60 cells, but not to CD38– controls. DTT treatment of CD38+ HL60 cells reduced DARA binding by 92% by denaturing cell surface CD38. Treating DARA‐containing plasma with soluble CD38 or anti‐DARA idiotype also inhibited DARA binding. CONCLUSION DARA causes panreactivity in vitro by binding to CD38 on reagent RBCs. Treating reagent RBCs with DTT is a robust method to negate the DARA interference, enabling the safe provision of blood to DARA‐treated patients. Because DTT denatures Kell antigens, K– units are provided to these patients.

TTI-621 (SIRPαFc): A CD47-Blocking Innate Immune Checkpoint Inhibitor with Broad Antitumor Activity and Minimal Erythrocyte Binding

“…Second, minimal erythrocyte binding permits the use of an IgG1-based fusion protein, and thus maximizes macrophage phagocytosis of tumor cells, without concern for opsonizing red blood cells and targeting them for destruction. Third, CD47-targeting agents that bind erythrocytes may interfere with transfusion typing and cross-matching tests, as seen with other agents that bind erythrocytes (35,36). Finally, TTI-621 is likely to have a superior pharmacokinetic profile compared with anti-CD47 mAbs by avoiding the significant antigen sink created by dense cell surface expression of CD47 on erythrocytes, enabling more comprehensive engagement of tumor-expressed CD47.…”

Phase 1/2 study of daratumumab, lenalidomide, and dexamethasone for relapsed multiple myeloma

“…Daratumumab can cause panreactivity in blood crossmatching assays as a result of the drug's affinity to CD38 on red blood cells. 24,25 A range of methods have been successfully deployed to overcome this interference, including phenotyping patients before the first daratumumab dose, incubating red blood cells with dithiothreitol, using antidaratumumab idiotype antibodies, and genotyping. 26 No hemolysis was observed in any patient who received blood transfusions.…”

Clinical efficacy of daratumumab monotherapy in patients with heavily pretreated relapsed or refractory multiple myeloma

“…It has previously been reported that daratumumab binds to CD38 expressed on the surface of red blood cells. 14,15 Although this additional activity may interfere with blood typing and cross-matching, no AEs related to hemolysis were reported.…”