RecruitingPhase 2Drug trialCHOP Plus Mosunetuzumab as First Line in Patients With Richter´s Syndrome: a Phase II Study of the Spanish Group of CLLThe goal of this clinical trial is to learn if drug Mosunetuzumab works to treat Richter´syndrome . It will also learn about the safety of drug Mosunetuzumab. The main questions it aims to evaluate the efficacy of mosunetuzumab combined with CHOP (M-CHOP) after the end of induction in patients with Richter´s Syndrome who have never received thearapy What medical problems do participants have when taking drug Mosunetuzumab? Patients with Richter´s Syndrome Participants will: Take drug Mosunetuzumab+CHOP during 6 cycle and they if they are not candidate to Alothasplant continuing 11 cycles more with mosunetuzumab on monoterapy Visit the clinic once every 23weeks for checkups and tests