A Phase 2 Trial of GlOfitamab anD pIrtobrutinib in Mantle Cell Lymphoma Patients With Prior BTK Inhibitor Exposure.

The goal of this clinical trial is to evaluate the safety and response of combination Pirtobrutinib and Glofitimab in patients with relapsed/refractory MCL. The main question it aims to answer are: * Will additive and synergistic effects be observed when using a combination of glofitamab and pirtobrutinib? * Will this combination be safe and lead to high complete- and MRD-negative remission rates? Participants will receive treatment based on 21 day cycles. This study design involves 3 phases: 1. Treatment Ramp-Up 1. Pre-Phase (7 days): Obinutuzumab (1000mg) will be administered intravenously (IV) on D-7 and a second dose administered between Day 6 and Day 1. 2. Cycle 1: An initial dose level of Glofitamab will evaluate step-up dosing. If excessive dose-limiting toxicity is observed, including cytokine release syndrome (CRS), a lower initial dose of 1.25mg of glofitamab will be evaluated at "dose level -1". i. Dose level 1 (14 days): * 2.5mg Glofitamab by IV on Day 1 * 10mg Glofitamab by IV on Day 8 ii. Dose level -1 (21 days): * 1.25mg Glofitamab by IV on Day 2 * 2.5mg Glofitamab by IV on Day 8 * 10mg Glofitamab by IV on Day 15 c. Cycle 2 (21 days): 30mg Glofitamab by IV on Day 1 2. Fixed course combination phase: Cycles 3-12 (21 days per cycle): 30mg of Glofitamab by IV on day 1 3. Maintenance phase: Cycles 13+ (21 days per cycle): Glofitamab discontinued. 200mg oral daily