MDX2003

**MDX2003** is a novel tetraspecific antibody developed by ModeX Therapeutics, a subsidiary of OPKO Health, designed as a T-cell engager-expander for relapsed/refractory B-cell malignancies. It simultaneously targets two tumor antigens, **CD19** and **CD20**, highly expressed on malignant B cells, along with T-cell effectors **CD3** and co-stimulatory **CD28** to optimize sustained T-cell function, enhance survival, and preferentially kill tumor cells over normal B cells. This dual-targeting strategy addresses tumor heterogeneity and antigen loss, common causes of resistance in B-cell lymphomas/leukemias, potentially offering an alternative to CAR-T therapies with improved scalability. Currently in a Phase 1/2 clinical trial (NCT07249905) evaluating safety, tolerability, pharmacokinetics, and preliminary anti-tumor activity in patients with large B-cell lymphoma, follicular lymphoma, mantle cell lymphoma, and other B-cell neoplasms who have progressed after at least two prior therapies.[2][3][5][7][8][9][10]