Anti-CD19 Monoclonal antibody, clone IJC20 [Alexa Fluor® 488]

RSK2 is a serine/threonine kinase downstream signaling mediator in the RAS/ERK signaling pathway and may be a therapeutic target in mantle cell lymphoma (MCL), an almost incurable disease subtype of non-Hodgkin lymphoma. In this study, serine-227 (RSK2(Ser227)) in the N-terminal kinase domain (NTKD) of RSK2 was found to be ubiquitously active in five MCL-derived cell lines and in tumor tissues derived from five MCL patients. BI-D1870, an inhibitor specific to RSK2-NTKD, caused RSK2(Ser227) dephosphorylation, and thereby, induced dose-dependent growth inhibition via G(2)/M cell cycle blockade and apoptosis in four of the five cell lines, while one cell line showed only modest sensitivity. In addition, RSK2 gene knockdown caused growth inhibition in the four BI-D1870-sensitive cell lines. Comparative gene expression profiling of the MCL-derived cell lines showed that inhibition of RSK2(Ser227) by BI-D1870 caused downregulation of oncogenes, such as c-MYC and MYB; anti-apoptosis genes, such as BCL2 and BCL2L1; genes for B cell development, including IKZF1, IKZF3, and PAX5; and genes constituting the B cell receptor signaling pathway, such as CD19, CD79B, and BLNK. These findings show that targeting of RSK2(Ser227) enables concomitant blockade of pathways that are critically important in B cell tumorigenesis. In addition, we found favorable combinatory growth inhibitory effects of BI-D1870 with inhibitors of BTK (ibrutinib), AKT (ipatasertib), and BCL2 (venetoclax) in cell characteristic-dependent manners. These results provide a rationale for RSK2(Ser227) in the NTKD as a potential therapeutic target in MCL and for future development of a novel bioavailable RSK2 NTKD-specific inhibitor.

Background The addition of rituximab to intensive chemotherapy improves outcomes in patients with B-cell acute lymphoblastic leukaemia. Ofatumumab is an anti-CD20 monoclonal antibody that binds to the small extracellular loop of CD20 and has greater in vitro complement-mediated cytotoxicity than rituximab. In this study, we assessed the activity and safety of ofatumumab in combination with chemotherapy in patients with Philadelphia chromosome (Ph)-negative CD20-positive B-cell acute lymphoblastic leukaemia. Methods This was a single-arm, phase 2 trial done at the MD Anderson Cancer Center (Houston, TX, USA). Patients with newly diagnosed, Ph-negative B-cell acute lymphoblastic leukaemia or lymphoblastic lymphoma with CD20 expression of at least 1% were eligible. Patients were treated with up to eight courses of the hyper-CVAD regimen (hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone) on courses 1, 3, 5, and 7 alternating with high-dose methotrexate and cytarabine on courses 2, 4, 6, and 8. Ofatumumab was administered on days 1 and 11 of courses 1 and 3 and on days 1 and 8 of courses 2 and 4 for a total of eight doses. The first dose of ofatumumab was 300 mg intravenously and all subsequent doses were 2000 mg intravenously. Patients received 30 courses of maintenance therapy with 6-mercaptopurine, vincristine, methotrexate, and prednisone (POMP), with four intensification courses (high-dose methotrexate plus L-asparaginase and hyper-CVAD plus ofatumumab on courses 6-7 and 18-19). The primary endpoints were event-free survival, overall response, and overall survival. All enrolled patients were included in the primary and safety analyses. The trial is registered with ClinicalTrials.gov, NCT01363128. Findings Between Aug 26, 2011, and May 18, 2017, 69 patients (67 patients had B-cell acute lymphoblastic leukaemia and two had B-cell lymphoblastic lymphoma; median age 41 years [IQR 32-50]) were enrolled and treated, including 33 (48%) aged between 18 and 39 years. Nine (27%) of 33 patients had Ph-like acute lymphoblastic leukaemia. With a median follow-up of 44 months (26-53), 4-year event-free survival was 59% (95% CI 48-73); 69% (54-87) in adolescents and young adults aged 18-39 years. 4-year overall survival was 68% (58-81); 74% (60-91) in adolescents and young adults. The overall response rate was 98% (64 of 65 patients). The most common non-haematological grade 3 or 4 adverse events were infections (35 [54%] of 65 patients during induction and 53 [78%] of 68 patients during consolidation). Ten (14%) of 69 patients died in complete remission from sepsis (two [3%]), cardiac arrest (one [1%]), therapy-related acute myeloid leukaemia (two [3%]), and haematopoietic stem-cell transplantation complications (five [7%]). None of these deaths were considered related to ofatumumab treatment by the study investigators. Interpretation The combination of hyper-CVAD plus ofatumumab is safe and active in adults with Ph-negative CD20-positive B-cell acute lymphoblastic leukaemia. Modifications of this regimen with the addition of novel monoclonal and bispecific antibody constructs targeting CD19 and CD22 might further improve outcomes and allow reduction in the intensity and duration of chemotherapy. Copyright (c) 2020 Elsevier Ltd. All rights reserved.