Vemurafenib, Cobimetinib, Atezolizumab, and Tiragolumab in Treating Patients With High-Risk Stage III Melanoma

PRIMARY OBJECTIVES: I. To estimate the percentage of patients with stage III BRAFV600 mutated (BRAFm) melanoma that achieves a pathologic complete response after 12 weeks of neoadjuvant vemurafenib/cobimetinib/atezolizumab (neoadjuvant phase). II. To estimate the percentage of patients with stage III BRAF-wild-type (BRAFwt) melanoma that achieves a pathologic complete response after 12 weeks of neoadjuvant cobimetinib/atezolizumab (neoadjuvant phase). III. To estimate the percentage of patients with stage III melanoma that achieves a pathologic complete response (pCR) after 12 weeks of neoadjuvant atezolizumab/tiragolumab (neoadjuvant phase). IV. To assess recurrence-free survival (RFS) in patients with stage III BRAFm melanoma after neoadjuvant vemurafenib/cobimetinib/ atezolizumab, surgery, and adjuvant atezolizumab (adjuvant phase). V. To assess RFS in patients with stage III BRAFwt melanoma after neoadjuvant cobimetinib/atezolizumab, surgery, and adjuvant atezolizumab (adjuvant phase). VI. To assess RFS in patients with stage III melanoma after neoadjuvant atezolizumab/tiragolumab, surgery, and adjuvant atezolizumab (adjuvant phase). SECONDARY OBJECTIVES: I. To determine the frequency of adverse events among patients with stage III BRAFm melanoma receiving neoadjuvant vemurafenib / cobimetinib / atezolizumab followed by surgery followed by adjuvant atezolizumab. II. To determine the frequency of adverse events among patients with stage III BRAFwt melanoma receiving neoadjuvant cobimetinib/atezolizumab followed by surgery followed by adjuvant atezolizumab. III. To determine the frequency of adverse events among patients with stage III melanoma receiving neoadjuvant atezolizumab/tiragolumab followed by surgery followed by adjuvant atezolizumab. TRANSLATIONAL OBJECTIVES: I. To determine the association between pretreatment, on treatment, post-neoadjuvant and post-adjuvant treatment soluble PD-L1 (sPD-L1) and RFS in patients with stage III melanoma receiving neoadjuvant vemurafenib / cobimetinib / atezolizumab or cobimetinib/atezolizumab, or atezolizumab/tiragolumab, followed by surgery and adjuvant atezolizumab. II. To determine the association between pretreatment, on treatment, post-neoadjuvant and post-adjuvant treatment intracellular bim in tumor-related T cells and RFS in patients with stage III melanoma after neoadjuvant vemurafenib/cobimetinib/atezolizumab or cobimetinib/atezolizumab, or atezolizumab/tiragolumab, followed by surgery and adjuvant atezolizumab. III. Evaluate associations between pre and post-neoadjuvant treatment molecular features of melanomas and the tumor immune microenvironment in responders versus non-responders with multiplex immunofluorescence (MxIF) (including T-cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibition motif domains \[TIGIT\]) and ribonucleic acid-sequencing (RNA-Seq) in patients with stage III melanoma after neoadjuvant vemurafenib/cobimetinib/atezolizumab or cobimetinib/atezolizumab, or atezolizumab/tiragolumab, followed by surgery and adjuvant atezolizumab. IV. To determine the association between pretreatment tumor PD-L1, pCR, and RFS in patients with stage III melanoma receiving neoadjuvant vemurafenib/ cobimetinib/ atezolizumab or cobimetinib/atezolizumab, or atezolizumab/tiragolumab, followed by surgery and adjuvant atezolizumab. V. To evaluate changes in cell-free deoxyribonucleic acid (DNA) over time to determine whether these changes correlate with clinical outcomes, including pathologic complete response and cancer progression. VI. To compare T cell receptor diversity/clonality in pretreatment tumor, tumor and uninvolved lymph node from the time of surgery, as well as blood from before treatment, after neoadjuvant treatment, after surgery, and after adjuvant treatment. VII. To compare the frequency of neoantigen-specific T cells in pretreatment tumor, tumor and uninvolved lymph node from the time of surgery, as well as blood from before treatment, after neoadjuvant treatment, after surgery, and after adjuvant treatment. VIII. To compare peripheral blood mononuclear cell subsets from before treatment, after neoadjuvant treatment, after surgery, and after adjuvant treatment via multiparametric mass cytometry (CyTOF). IX. To assess whether treatment response to neoadjuvant systemic therapy in the index biopsy-proven metastatic node is indicative of the overall response in the nodal basin. X. To evaluate whether baseline or changes over time in microbiome samples correlate with clinical outcomes, including pathologic complete response and cancer progression. OUTLINE: Patients are assigned to Arm C. ARM A (BRAF mutant): Patients receive vemurafenib orally (PO) twice daily (BID) on days 1-28 and cobimetinib PO once daily (QD) on days 1-21. Patients also receive atezolizumab intravenously (IV) over 30-60 minutes on days 1 and 15 of cycles 2 and 3. Treatment repeats every 28 days for up to 3 cycles in the absence of disease progression or unacceptable toxicity. (CLOSED TO ACCRUAL) ARM B (BRAF wild-type): Patients receive cobimetinib as in Arm A and atezolizumab IV over 30-60 minutes on days 1 and 15. Treatment repeats every 28 days for up to 3 cycles in the absence of disease progression or unacceptable toxicity. (CLOSED TO ACCRUAL) ARM C: Patients with BRAF wild-type or BRAF mutant melanoma receive atezolizumab IV over 30-60 minutes and tiragolumab IV over 30-60 minutes on day 1. Treatment repeats every 21 days for up to 4 cycles in the absence of disease progression or unacceptable toxicity. Within 2-4 weeks after treatment, patients undergo surgery then receive atezolizumab IV over 30-60 minutes on day 1. Treatment repeat every 21 days for up to 8 cycles in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed every 3 months for up to 3 years.