Plamotamab (XmAb-13676) is a human bispecific antibody (bsAb) that binds CD3 and CD20. Plamotamab recruits cytotoxic T cells to kill CD20+ expressing tumor cells. Plamotamab induces a mild hematologic reaction (MR), and results in tumor regression in vivo.
Plamotamab induces the killing of endogenous B cells and activation of endogenous CD8+ T cells within human PBMCs in vitro, with an EC50 value of 0.113 nM[2].Plamotamab induces T cell-mediated killing in Raji tumor cells in vitro, with an EC50 value of 0.144 nM[2].Plamotamab binds to CD3δ/ε, CD3+ T cells, CD4+ T cells, CD8+ T cells, B cells, Raji cells, with EC50s of 2.1 nM, 11.78 nM, 10.12 nM, 200.3 nM, and 134.8 nM, respectively[2].
Plamotamab (0.17 mg/kg; i.p.) causes tumor growth suppression in human PBMC-engrafted mouse model containing Raji xenograft[2].Plamotamab (0.3 mg/kg; i.p.) leads to cytokine release in cynomolgus monkeys, indicating a safety to be improved[2].
References:
[1]. Parrondo RD, et al. Plamotamab (XmAb®13676) for Ibrutinib- refractory CXCR4-mutated extramedullary Waldenström macroglobulinemia. Leuk Lymphoma. 2022 Mar;63(3):738-742.
[2]. Luo Peter PZ, et al. Anti-CD3 antibodies and methods of use thereof. World Intellectual Property Organization, WO2022170740 A1. 2022-08-18.