Acalabrutinib, venetoclax, and obinutuzumab as frontline treatment for chronic lymphocytic leukaemia: a single-arm, open-label, phase 2 study

High expression level of ROR1 and ROR1-signaling associates with venetoclax resistance in chronic lymphocytic leukemia

Although the BH3-mimetic venetoclax is highly cytotoxic for chronic lymphocytic leukemia (CLL) cells, some patients with CLL fail to clear minimal residual disease (MRD). We examined the CLL cells of seven such patients (CLL1-7) and found each had high-level expression of ROR1. By examining the CLL cells from such patients prior to therapy at SC1 and then more than 1 year later (Sample Collection 2 (SC2)), when they had progressive increases in MRD despite continued venetoclax therapy, we found the levels of ROR1 expressed on CLL cells at SC2 were significantly higher than that on CLL cells collected at SC1. At SC2, we also observed upregulation of genes induced by Wnt5a-induced ROR1 signaling, including BCL2L1. Transduction of the CLL-cell-line MEC1 to express ROR1 enhanced expression of target genes induced by ROR1-signaling, increased expression of BCL-XL, and enhanced resistance to venetoclax, even in MEC1 made to express mutant forms of BCL2, which are associated with venetoclax resistance. Treatment of primary CLL cells with Wnt5a also increased their resistance to venetoclax, an effect that could be inhibited by the anti-ROR1 mAb (UC-961, zilovertamab). Collectively, these studies indicate that Wnt5a-induced ROR1-signaling can enhance resistance to venetoclax therapy.

Bruton Tyrosine Kinase Inhibitors in B-Cell Malignancies: Their Use and Differential Features

Starting with the first-in-class agent ibrutinib, the development of Bruton tyrosine kinase (BTK) inhibitors has led to dramatic improvements in the management of B-cell malignancies. Subsequently, more-highly selective second-generation BTK inhibitors (including acalabrutinib, zanubrutinib, tirabrutinib and orelabrutinib) have been developed, primarily with an aim to reduce off-target toxicities. More recently, third-generation agents including the non-covalent BTK inhibitors pirtobrutinib and nemtabrutinib have entered later-stage clinical development. BTK inhibitors have shown strong activity in a range of B-cell malignancies, including chronic lymphocytic leukaemia/small lymphocytic lymphoma, mantle cell lymphoma, Waldenström's macroglobulinaemia and marginal zone lymphoma. The agents have acceptable tolerability, with adverse events generally being manageable with dosage modification. This review article summarises the evidence supporting the role of BTK inhibitors in the management of B-cell malignancies, including highlighting some differential features between agents.

Phase 2 study of obinutuzumab (GA-101), ibrutinib and venetoclax (CLL2-GIVe) in patients with untreated high-risk chronic lymphocytic leukemia

Despite considerable treatment advances with targeted therapies for patients with chronic lymphocytic leukemia (CLL) deemed high-risk (del(17p) and/or TP53 mutation), outcome is still inferior compared to other CLL patients. Combining multiple agents with distinct mechanisms of action may further improve outcomes. CLL2-GIVe is an open-label, multicenter trial, which enrolled patients with previously untreated CLL with del(17p) and/or TP53 mutation. Patients received induction therapy with obinutuzumab (GA-101), ibrutinib and venetoclax (GIVe) for cycles 1-6 and consolidation therapy with venetoclax and ibrutinib for cycles 7-12. Ibrutinib monotherapy was continued for cycles 13-36 in patients not reaching a complete response (CR) with serial undetectable minimal residual disease (uMRD) after consolidation. The primary endpoint was CR rate at cycle 15 (final restaging). Secondary endpoints included MRD, survival and safety. All 41 patients, enrolled between September 2016 and August 2018, received study treatment and were included in efficacy and safety populations. With a CR rate of 58.5% at cycle 15, the primary endpoint was met (95% CI: 42.1-73.7; p<0.001). At final restaging, 78.0% of patients had uMRD in peripheral blood; 65.9% of patients had uMRD in bone marrow. Estimated progression-free and overall survival rates at 24 months were both 95.1%. Adverse events were reported in all patients, most were low grade (grade ≥3: 23.9%). Two deaths were reported (cardiac failure and ovarian carcinoma), neither related to study treatment. The CLL2-GIVe treatment regimen has a manageable safety profile and is a first-line treatment of good efficacy for patients with high-risk CLL.