Belantamab mafodotin（belamaf）是一种经过去醣化的单克隆抗体，与微管蛋白破坏剂单甲基auristatin-F（MMAF）共价连结在一起，靶向恶性浆细胞表面的B细胞成熟抗原（BCMA）。Belamaf可以通过多种机制消除骨髓瘤细胞（MM）。一方面，除了抑制BCMA受体信号和细胞存活外，细胞内释放的MMAF还可以破坏微管聚合并导致细胞周期停滞。另一方面，belamaf还通过抗体介导的细胞毒作用和抗体介导的细胞吞噬作用诱导效应细胞介导的肿瘤细胞裂解。在我们的体外共培养模型中，可以研究到上述第一种机制的后果：belamaf结合到BCMA上，降低MM的增殖和存活，然后进入恶性细胞的溶酶体中，释放MMAF。MMAF荷载引起DNA损伤检查点在G2和M期之间的细胞周期停滞，导致依赖caspase-3的凋亡。在这里，我们展示了从不同患者中分离的原发性MMs在BCMA表达水平方面可能存在广泛的差异，并且我们的细胞毒作用实验表明，BCMA表达不足与极高的belamaf耐药性相关。我们还揭示了原发性MMs对增加剂量的belamaf做出反应，通过增强来自自体骨髓基质细胞（BM-MSCs）的线粒体的并入，从而以这种方式使MMs变得更加耐药，这类似于我们以前分析过的其他药物，如蛋白酶体抑制剂卡菲索米布或BCL-2抑制剂维奈托克赛。在某些原发性骨髓瘤细胞培养物中观察到对belamaf的显着耐药性是令人担忧的，这表明需要使用联合治疗来克服抗原逃逸的风险。

Belantamab mafodotin (belamaf) is an afucosylated monoclonal antibody conjugated to the microtubule disrupter monomethyl auristatin-F (MMAF) that targets B cell maturation antigen (BCMA) on the surface of malignant plasma cells. Belamaf can eliminate myeloma cells (MMs) through several mechanisms. On the one hand, in addition to inhibiting BCMA-receptor signaling and cell survival, intracellularly released MMAF disrupts tubulin polymerization and causes cell cycle arrest. On the other hand, belamaf induces effector cell-mediated tumor cell lysis via antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis. In our in vitro co-culture model, the consequences of the first mentioned mechanism can be investigated: belamaf binds to BCMA, reduces the proliferation and survival of MMs, and then enters the lysosomes of malignant cells, where MMAF is released. The MMAF payload causes a cell cycle arrest at the DNA damage checkpoint between the G2 and M phases, resulting in caspase-3-dependent apoptosis. Here, we show that primary MMs isolated from different patients can vary widely in terms of BCMA expression level, and inadequate expression is associated with extremely high resistance to belamaf according to our cytotoxicity assay. We also reveal that primary MMs respond to increasing concentrations of belamaf by enhancing the incorporation of mitochondria from autologous bone marrow stromal cells (BM-MSCs), and as a consequence, MMs become more resistant to belamaf in this way, which is similar to other medications we have analyzed previously in this regard, such as proteasome inhibitor carfilzomib or the BCL-2 inhibitor venetoclax. The remarkable resistance against belamaf observed in the case of certain primary myeloma cell cultures is a cause for concern and points towards the use of combination therapies to overcome the risk of antigen escape.