Ibrutinib Combined With Rituximab for Treatment of Relapsed Refractory MYD88 and CD79A/B (or CD79B Alone) DLBCL Who Have Received at Least Two Prior Therapies

Recent studies have found that about 30% of DLBCL have mutations in MYD88 and/or CD79A/B genes. MYD88 and CD79A/B protein molecules belong to two signal transduction pathways, which regulate B cell proliferation. Both MYD88 and CD79A/B gene mutations can abnormally activate BTK located downstream of MYD88 and CD79A/B, leading to over activation and proliferation of B cells. Ibrutinib is the first generation of oral BTKi, which may theoretically inhibit the tumorigenesis of DLBCL with abnormal BTK activation caused by mutations in MYD88 and CD79A/B genes. A phase II clinical study of ibrutinib monotherapy in the treatment of relapsed and refractory DLBCL showed that the effective rate of ibutinib for single CD79B mutation was 55.5% (5/9 cases), and that for both CD79B and MYD88 mutations was 80% (4/5 cases). About 40 \~ 50% of primary central nervous system large B cell lymphoma (PCNSL) have CD79B and MYD88 mutations. A small sample study found that the overall response rate (ORR) for the treatment of relapsed and refractory PCNSL with ibrutinib was 77% (10/13). An expanded sample study of 44 cases of PCNSL treated with ibrutinib found that the ORR is 52% and progression-free survival (PFS) is 4.8 months. These results suggest that ibrutinib may be more effective in DLBCL with MYD88 and CD79A/B or CD79B mutations. The relationship between mutations in MYD88 and CD79B and therapeutic sensitivity of ibrutinib can not be simply categorized, because abnormalities in other genes of B cell signaling pathway, such as CARD11, TNFAIP3, CXCR4, JAK1 and PIM1, may also affect the efficacy of ibrutinib. Therefore, it is necessary to comprehensively analyze the gene abnormalities of other B cell related signaling pathways, such as downstream signal of Bruton kinase, CXCR, JAK-STAT, and NFKB, to find out the most effective group of DLBCL patients treated with ibrutinib. This phase II, single-arm, open-label, multi-center clinical trial will evaluate the efficacy and safety of ibrutinib combined with rituximab in treating relapsed refractory MYD88 and CD79A/B (or CD79B alone) DLBCL who have received at least two prior therapies. The study will also explore the relationship between MYD88 and/or CD79A/B and efficacy, and detect the gene abnormality by Next Generation Sequencing (NGS) and evaluate the relationship between other gene abnormality and efficacy.