The study consists of 2 sequential parts.
1. Safety Run-in - this part will compare dose levels of Surovatamig (AZD0486) in combination with rituximab in order to establish the RP3D.
2. Phase III - The Phase III part will assess the superiority of Surovatamig (AZD0486) at RP3D in combination with rituximab, compared to Investigator's choice between 3 standard chemoimmunotherapy regimens. Phase 3 consists of 3 arms
1. Arm A: treatment with Surovatamig plus rituximab Schedule A
2. Arm B: treatment with Surovatamig plus rituximab Schedule B
3. Arm C (Comparator arm): one of the following standard regimens per Investigator's choice: R-CVP + rituximab maintenance, R-CHOP + rituximab maintenance or B-R + rituximab maintenance
