This is a multi-center, open-label two-part study evaluating the safety and tolerability of MT-3724 in combination with GEMOX in relapsed or refractory B-cell Lymphoma patients.~Part 1: (MT-3724 Dose Escalation) Define the maximum tolerated dose (MTD) of MT-3724 in combination with standard treatment of GEMOX~Part 2: (MTD Expansion Cohort) Confirm the safety and tolerability of the MTD of MT-3724 from Part 1 in the MTD Expansion Cohort, where MT-3724 will be given at the MTD in combination with GEMOX. In addition, the PK, PD, immunogenicity and tumor response at the MTD of MT-3724 in combination with GEMOX will be more thoroughly evaluated in Part 2.~In original protocol and amendment 2, participants will be administered intravenous (IV) MT-3724 over 1 hour on Days 1, 3, 5, 8, 10 and 12 in Cycles 1 and 2 (each 28-day cycle) and on Days 1, 8, 15, and 22 in Cycles 3 and 4 (each 28-day cycle). Participants will also be administered Gemcitabine 1000 milligrams per meter square (mg/m^2) as 30-minute IV infusion and Oxaliplatin 100 mg/m^2 as 2-hour IV infusion on Days 2 and 16 in Cycles 1, 2, 3 and 4 (each 28-day cycle). Per amendment 2, participants will be administered MT-3724 on Days 1, 3, 5, 8, 10, 12, 15, 22, 29, and 36 in Cycle 1 (42-day cycle). In Cycles 2, 3 and 4, MT-3724 will be administered weekly on Days 1, 8, 15, and 22 of each 28-day cycle. Gemcitabine and oxaliplatin will be administered on Days 16 and 30 of Cycle 1 and on Days 2 and 16 in Cycles 2, 3 and 4 (42-day cycle for Cycle 1 and 28-day cycle for Cycle 2, Cycle 3 and Cycle 4).~Continued Treatment with MT-3724 in combination with GEMOX will continue for four cycles of until death, disease progression, unacceptable toxicity, withdrawal of consent or another reason for withdrawal.~After four cycles, the participants who experience clinical benefit can continue MT-3724 treatment with additional cycles of 28 days each (either alone or in combination with GEMOX) if supported by the investigator's assessment of the benefit-risk ratio, after consultation with sponsor and Medical Monitor
The purpose of this study is to evaluate the safety and tolerability of MT-3724 in combination with gemcitabine and oxaliplatin (GEMOX) in participants with relapsed or refractory B-Cell NHL.