# A rabbit anti-human CD38 antibody for eliminating daratumumab and isatuximab interference in immunohematology testing

## TL;DR

A new rabbit antibody helps eliminate interference from cancer drugs in blood tests, improving transfusion safety for multiple myeloma patients.

## Contribution

A novel rabbit anti-human CD38 monoclonal antibody was developed to block therapeutic antibody interference in immunohematology testing.

## Key findings

- The rabbit anti-human CD38 antibody D2 effectively blocks DARA- and ISA-induced pan-agglutination in IAT.
- D2 preserves clinically significant RBC antigens and detects irregular antibodies in patient samples.
- D2 is stable and suitable for routine use in transfusion laboratories.

## Abstract

Anti-CD38 antibodies such as daratumumab (DARA) and isatuximab (ISA), used in multiple myeloma (MM) therapy, bind to CD38 on red blood cells (RBCs), leading to pan-agglutination in indirect antiglobulin tests (IATs) and interfering with pretransfusion testing. Given the frequent need for transfusions in MM patients with anemia, resolving this interference is clinically essential. While dithiothreitol (DTT) is commonly used, it compromises clinically important RBC antigens. To address this limitation, a novel approach was developed using a recombinant rabbit anti-human CD38 IgG monoclonal antibody, D2, to treat RBCs. Rabbits were immunized with hCD38-His. Antigen-specific B cells were isolated via flow cytometry and subsequently sequenced to obtain the antibody genes. After cloning and expression, a rabbit mAb named D2 was selected for its ability to bind the CD38 on human RBCs and block the binding of therapeutic anti-CD38 antibodies without affecting other RBC blood group antigens. Incubation of 1 μL of packed RBCs with 3 μL of 1 mg/mL D2 for 10 minutes at room temperature eliminated DARA- or ISA-induced pan-agglutination in the IAT while preserving the detection of clinically significant irregular antibodies. Its efficacy was confirmed using samples from 48 DARA- or ISA-treated patients. D2 is stable, easy to use, and suitable for routine application in transfusion laboratories to resolve anti-CD38-induced interference in pretransfusion testing.

CD38 masking mechanism and antibody generation workflow. (A) Mechanism by which rabbit anti-human CD38 monoclonal antibody masks CD38 on red blood cells, preventing therapeutic antibody binding and allowing detection of irregular antibodies. (B) Workflow for generation of rabbit antihuman CD38 polyclonal and monoclonal antibodies.Illustration visualizing two experimental workflows: Panel A shows detection of anti-CD38 antibodies using indirect antiglobulin testing (IAT), with and without pretreatment using anti-human CD38 rabbit monoclonal antibody, resulting in agglutination or no agglutination. Panel B outlines production and testing of anti-human CD38 rabbit antibodies, showing steps from rabbit immunization and B cell isolation to ELISA, flow cytometry, and microcolumn gel card assays.

CD38 masking mechanism and antibody generation workflow. (A) Mechanism by which rabbit anti-human CD38 monoclonal antibody masks CD38 on red blood cells, preventing therapeutic antibody binding and allowing detection of irregular antibodies. (B) Workflow for generation of rabbit antihuman CD38 polyclonal and monoclonal antibodies.