International Validation of a Dithiothreitol (DTT)-Based Method to Resolve the Daratumumab Interference with Blood Compatibility Testing

Abstract

Introduction Daratumumab (DARA), an IgG1k human monoclonal antibody (Ab) against CD38, is a promising novel therapy for multiple myeloma. However, direct binding of DARA to endogenous CD38 on reagent red blood cells (RBCs) interferes with routine blood bank serologic testing. We recently showed that treating reagent RBCs with DTT eliminates the DARA interference by denaturing cell surface CD38, allowing the safe transfusion of patients on DARA.1 This multicenter international study was aimed at validating the DTT method for use by blood banks worldwide. Methods Participating blood banks received two plasma sample unknowns. Sample 1 was spiked with DARA alone (5 mcg/mL). Sample 2 was spiked with DARA plus a clinically significant RBC Ab (anti-D (Rh immune globulin) or monoclonal anti-Fya or anti-s). Sites were instructed to first perform an Ab screen using their usual method (tube, gel, or solid phase), then to repeat the Ab screen using DTT-treated RBCs (gel or tube). If the Ab screen remained positive with DTT-treated RBCs (Sample 2), sites were to identify the unknown Ab using a DTT-treated RBC panel (gel or tube.) The primary outcome measure was the proportion of sites able to successfully identify the unknown Ab in the presence of DARA. Qualitative data were collected by online survey. Results Paired plasma sample unknowns were shipped to 25 study sites in North America, South America, Europe, Asia, and Australia/New Zealand. Data were received from 23 sites to date (Table). For the initial Ab screen, 10 sites used tube testing, 7 sites used gel, and 6 sites used solid phase. All sites observed DARA interference with the Ab screen (false positive agglutination reactions). All sites reported no DARA interference using DTT-treated RBCs. For Ab identification (Sample 2), 13 sites used tube testing and 10 sites used gel. 23/23 sites (100%) were able to correctly identify the unknown Ab using the DTT method. The Abs identified were: anti-Fya (9/9), anti-s (8/8), and anti-D (6/6). Feedback on the DTT method was mainly positive, with 86% of sites that responded to the survey indicating that they planned to use the DTT method to manage clinical samples from DARA-treated patients. Conclusion DARA consistently interferes with all three Ab screening methods currently used by blood banks (tube, gel, and solid phase.) Using DTT-treated RBCs, 23/23 (100%) of blood bank laboratories from around the world were able to identify a clinically significant Ab initially masked by the presence of DARA. The DTT method is robust, reproducible, and can be implemented by blood banks globally to help provide safe blood products to patients on DARA. As DTT denatures Kell antigens, K- RBC units should be provided when using the DTT method. 1. Chapuy CI, Nicholson RT, Aguad MD, et al. Resolving the daratumumab interference with blood compatibility testing. Transfusion. 2015;55(6pt2):1545-1554. Disclosures Unger: Janssen: Employment. Doshi:Janssen: Employment. Kaufman:Janssen: Consultancy, Research Funding.

Papain‐treated panels are a simple method for the identification of alloantibodies in multiple myeloma patients treated with anti‐CD38‐based therapies

“…MM patients often require blood transfusions, posing a potential problem in the future. Other groups have suggested treating RBCs with DTT or using cord blood cell panels (Schmidt et al, ) to overcome this issue, and the DTT method was recently validated by an international collaborative group (Chapuy et al, ). However, both methods are time‐consuming and are unable to identify all possible antibodies.…”

Practical approaches and costs for provisioning safe transfusions during anti‐CD38 therapy

“…After Food and Drug Administration approval of the first anti‐CD38 daratumumab (Darzalex, Janssen Biotech), blood banks of all sizes began to grapple with anti‐CD38 testing interference. Several strategies were suggested to mitigate the drug effect including thiol‐ or trypsin‐treating RBCs, antibody screens with cord cells, antigen‐matched RBC transfusions guided by patient phenotyping or genotyping, and neutralizing the antibody with either soluble CD38 or anti‐daratumumab . However, limited availability of the latter two novel reagents and the complexity of testing options have precluded any one particular strategy emerging as standard of care .…”

Extending shelf life of dithiothreitol‐treated panel RBCs to 28 days

“…DTT treatment of panel RBCs abolishes DARA interference in IAT . Preparation of DTT‐treated panel RBCs can hamper timely provision of compatible RBCs in emergencies.…”

“…DARA causes variable non‐specific or panreactive results, potentially masking clinically significant alloantibodies. To circumvent the interference of DARA, panel RBCs can be treated with dithiothreitol (DTT) . However, treatment of panel RBCs with DTT is not selective and also destroys other RBC antigens, for example, of the Kell system or Lutheran system.…”