Phase 2/3 MK-1045 CD19×CD3 bispecific antibody plus rituximab (CD20 mAb) in 1L FL.

Merck Sharp & Dohme (MSD) is running a Phase 2/3, randomized, open-label study testing MK-1045 + rituximab (or a rituximab biosimilar) versus physician’s choice chemoimmunotherapy in previously untreated classical follicular lymphoma. MK-1045 is a CD19×CD3 bispecific monoclonal antibody designed to redirect T cells (CD3) to kill CD19-expressing malignant B cells, while rituximab targets CD20 on B cells for immune-mediated depletion.Part 1 dose-escalates weekly MK-1045 alongside Q4W rituximab to select a regimen; Part 2 expands and then compares against rituximab plus bendamustine or CHOP/CVP-based options per physician choice, focusing on outcomes including complete response and progression-free survival (Lugano/BICR). Eligible patients have stage II–IV, CD19+ and CD20+ FL (FLIPI 2–5), positioning this as a “chemo-sparing” frontline strategy that could shift a large commercial segment if efficacy is competitive with bendamustine-rituximab and R-CHOP/R-CVP, which remain common first-line approaches for patients who need systemic therapy.