Phase 2 Study of Glofitamab Monotherapy & With Polatuzumab Vedotin, Pirtobrutinib, or Atezolizumab in Richter's Transformation

Inclusion Criteria: Must have a confirmed diagnosis of chronic lymphocytic leukemia or small lymphocytic lymphoma as per IW-CLL 2018 criteria with biopsy proven transformation to large B-cell lymphoma (LBCL), consistent with Richter's Transformation. The diagnostic sample must be reviewed by the treating institution. * Tumor sample may be obtained by core needle or excisional surgical biopsy. * A fresh biopsy is encouraged, but an archival sample is acceptable if the following provisions are met: 1) availability of a tumor-containing formalin-fixed, paraffin-embedded (FFPE) tissue block, 2) if the tumor containing FFPE tissue block cannot be provided in total, sections from this block should be provided. * Biopsy can be obtained up to 3 months prior to first day of treatment. Measurable disease, defined as ≥1 measurable nodal lesion (long axis \>1.5 cm or short axis \>1.0 cm) or ≥1 measurable extra-nodal lesion (long axis \>1.0 cm) on PET, CT, or magnetic resonance imaging (MRI). Disease should be FDG-avid based on PET. Cohort-specific eligibility criteria: * Glofitamab monotherapy cohort: Patients with either relapsed/refractory or previously untreated Richter's Transformation. * Glofitamab + polatuzumab vedotin cohort: Patients with previously untreated RT. After the first 10 patients are enrolled in this cohort irrespective of prior BTKi exposure status, the remainder of the patients enrolled to this cohort must have previously untreated RT and no prior BTK inhibitor. Patients cannot have prior polatuzumab vedotin exposure. * Glofitamab + pirtobrutinib cohort: Patients with previously untreated RT and prior BTK inhibitor exposure (with enrollment to begin only after the first 10 patients are accrued to the polatuzumab combination cohort). Patients cannot have prior pirtobrutinib exposure. * Glofitamab + atezolizumab cohort: Patients with relapsed/refractory RT. Patients are required to have received ≥ 1 prior line of therapy. Patients cannot have prior atezolizumab exposure. Age ≥18 years. ECOG performance status of 0-2 (Appendix A). For patients receiving glofitamab monotherapy, glofitamab in combination with polatuzumab vedotin, or glofitamab in combination with atezolizumab, participants must meet the following organ and marrow function as defined below: * Absolute neutrophil count must be \> 1.0 x109/L (growth factor allowed to achieve), unless patients have significant bone marrow involvement of their malignancy confirmed on biopsy. * Platelets must be \> 30 x109/L, independent of transfusion within 7 days of screening, unless patients have bone marrow involvement of their malignancy confirmed on biopsy * Creatinine \< 2.0 x ULN (upper limit of normal) or estimated CrCl \> 50 ml/min according to Cockcroft/Gault formula * Total bilirubin \< 1.5 X ULN o Subjects with Gilbert's Syndrome or resolving autoimmune hemolytic anemia may have a bilirubin up to 3.0 X ULN * AST/ALT \< 3.0 X ULN, unless documented liver involvement by lymphoma For patients receiving glofitamab in combination with pirtobrutinib, participants must meet the following: * Absolute neutrophil count must be \> 1.0 x109/L (growth factor \>7 days prior allowed to achieve), unless patients have significant bone marrow involvement of their malignancy confirmed on biopsy. * Hemoglobin \> 8 g/dL, independent of transfusion within 7 days of screening, unless patients have bone marrow involvement of their malignancy confirmed on biopsy * Platelets must be \> 50 x109/L, independent of transfusion within 7 days of screening * Estimated CrCl \> 50 ml/min according to Cockcroft/Gault formula * AST/ALT \< 3.0 X ULN, or \< 5.0 X ULN with documented liver involvement by lymphoma * Total bilirubin \< 1.5 X ULN or \< 3.0 x ULN with documented liver involvement by lymphoma and/or Gilbert's Disease * Adequate coagulation, defined as activated partial thromboplastin time (aPTT) or partial thromboplastin time (PTT) and prothrombin (PT) or (international normalized ratio (INR) not greater than 1.5 x ULN. * The patient is able to take oral medications Patients who have undergone prior allogeneic transplantation are potentially eligible if their transplant day 0 is \> 6 months from their first dose of treatment and as follows: For patients receiving glofitamab monotherapy or glofitamab in combination with polatuzumab vedotin, all of the following must additionally be true: * No current or prior Grade 3/4 graft versus host disease (GVHD) * Stable off of immunosuppression for at least 2 months prior to receiving their first dose of treatment on study For patients receiving glofitamab in combination with pirtobrutinib, all of the following must additionally be true: * No active/current GVHD * No prior history of Grade 3/4 GVHD * Stable off of immunosuppression for at least 2 months prior to receiving their first dose of treatment on study For patients receiving atezolizumab, no prior allogeneic hematopoietic cell transplantation is allowed. Willingness to remain abstinent (refrain from heterosexual intercourse) or to use highly effective contraceptive methods that result in a failure rate of \<1% per year during the treatment period and for at least the following durations listed below: * Female patients: at least 18 months after pre-treatment with obinutuzumab, or 2 months after the last dose of glofitamab, or 5 months after the last dose of atezolizumab, or 9 months after the last dose of polatuzumab vedotin, or 3 months after the last dose of tocilizumab (if applicable), or 1 month after the last dose of pirtobrutinib, whichever is longest. * Male patients: at least 6 months after pre-treatment with obinutuzumab, or 2 months after the last dose of glofitamab, or 6 months after the last dose of polatuzumab vedotin, or 2 months after the last dose of tocilizumab (if applicable), whichever is longest. * Examples of highly effective contraceptive methods with a failure rate of \<1% per year include: Tubal ligation, male s