Interference of BCMA CAR-T cell detection with teclistamab. (A) Schematic overview of BCMA CAR-T cell detection. (B-D) BCMA CAR-T cell detection by flow cytometry of 5 samples of patients with MM (B) at the time of leukapheresis and (C) 12 to 14 days after BCMA CAR-T cell treatment (Ide-cel). Furthermore, samples from 5 patients pretreated with teclistamab were analyzed (D) at the time of leukapheresis. Dashed lines indicate cutoff values for defining CAR-positive T cells. (E) (Top) schematic overview of BCMA CAR DNA, including the location of forward (fwd) and reverse (rev) primers. (E) (Bottom) gel electrophoresis of quantitative PCR amplified BCMA CAR DNA products from samples of patients with MM, taken at the time of leukapheresis (LP); 14 days after CAR-T cell administration (Ide-cel) (14 days) and at leukapheresis with teclistamab pretreatment (LP + tec.). Human Growth Hormone 1 (hGH1) served as the reference gene and aqua dest. (a.d.) as the negative control. Shown is 1 experiment out of 5. The gel image was adjusted for contrast and brightness, with no nonlinear adjustments. (F) Schematic overview of the recognition of teclistamab binding to CD3 T cells using BCMA CAR detection reagent. TM, transmembrane domain.