Dose reductions in ibrutinib therapy are not associated with inferior outcomes in patients with chronic lymphocytic leukemia (CLL).

Ibrutinib is a first-in-class small molecule inhibitor that has shown remarkable efficacy in the treatment of CLL. Current guidelines recommend lifelong administration at a fixed daily dose of 420 mg. Data from real-world studies indicate up to 17.5% of patients discontinue ibrutinib due to toxicity. Hypothetically, judicious dose reductions could result in improved tolerance. Our objective was to study the impact of dose reductions on outcomes in CLL patients treated with ibrutinib in a real-world setting. We identified 70 CLL patients treated with ibrutinib at Roswell Park Comprehensive Cancer Center between January 2014 and June 2017. Twenty-three (31.3%) patients required dose reductions. There was no statistically significant difference in overall response rate (ORR), clinical benefit rate (CBR), median progression-free survival, and overall survival (OS) between the dose-reduced and standard-dose groups (SDGs). These results extended to all patients, irrespective of whether the modification was made within three months of treatment initiation, or later.

Ofatumumab Exhibits Enhanced In Vitro and In Vivo Activity Compared to Rituximab in Preclinical Models of Mantle Cell Lymphoma.

PURPOSE: Mantle cell lymphoma (MCL) is a mature B-cell lymphoma considered to be incurable with current treatments, including first-line rituximab in combination with multiagent chemotherapy and for those eligible, high-dose chemotherapy and stem cell support or rituximab maintenance. On the other hand, achieving a complete remission by high-sensitive flow cytometry is associated with prolonged duration of remission, stressing the need to develop and/or incorporate novel agents into the management of MCL. To this end, we examined the activity of ofatumumab, an anti-CD20 monoclonal antibody with distinct binding and immunologic properties compared to rituximab, in MCL preclinical models. EXPERIMENTAL DESIGN: MCL cells were labeled with (51)Cr before incubation with rituximab or ofatumumab (10 µg/mL) plus human serum or effector cells. (51)Cr-release was measured and the percentage of lysis was calculated. Surface CD20, CD55, and CD59 were measured by Imagestream analysis. SCID mice inoculated subcutaneously with Z138 cells were assigned to control versus four doses of ofatumumab or rituximab (10 mg/kg/dose). RESULTS: Ofatumumab exhibited enhanced in vitro complement-dependent cytotoxicity activity compared with rituximab in MCL cell lines, despite a high degree of in vitro resistance to rituximab associated with low CD20 levels and/or high expression of complement inhibitory proteins. Ofatumumab also delayed tumor progression and prolonged survival in a murine model of MCL. CONCLUSIONS: Our results demonstrate that ofatumumab is more effective than rituximab in MCL preclinical models, including in the presence of rituximab resistance, and support the clinical investigation of ofatumumab in combination with standard systemic chemotherapy in MCL (NCT01527149).

Distinct cellular and therapeutic effects of obatoclax in rituximab-sensitive and -resistant lymphomas.

Bcl-2 proteins represent a rheostat that controls cellular viability. Obatoclax, a BH3-mimetic, has been designed to specifically target and counteract anti-apoptotic Bcl-2 proteins. We evaluated the biological effects of obatoclax on the anti-tumour activity of rituximab and chemotherapy agents. Obatoclax induced cell death of rituximab/chemotherapy-sensitive (RSCL), -resistant cell lines (RRCL) and primary tumour-cells derived from patients with B-cell lymphomas (N=39). Obatoclax also enhanced the activity of rituximab and had synergistic activity when combined with chemotherapy agents. The ability of Obatoclax to induce PARP cleavage varied between patient samples and was not observed in some RRCL. Inhibition of caspase activity did not affect obatoclax activity, suggesting the existence of caspase-independent death pathways. Autophagy was detected by LC3 conversion and/or electron microscopy in RRCL and in patient-derived tumour cells. Moreover, obatoclax activity was inhibited by Beclin-1 knockdown. In summary, obatoclax is an active Bcl-2 inhibitor that potentiates the activity of chemotherapy agents and, to a lesser degree, rituximab. Defining the molecular events triggered by obatoclax is necessary to further its clinical development and identify potential biomarkers that are predictive of response.

Dacetuzumab, a humanized mAb against CD40 for the treatment of hematological malignancies.

Dacetuzumab, a humanized mAb targeting the CD40 antigen, is in development by Seattle Genetics Inc and licensee Genentech Inc for the potential treatment of hematological malignancies. The CD40 antigen is a highly expressed cell surface transmembrane protein that is present in normal B-cells. Experiments using blocking antibodies for the CD40 ligand demonstrated that CD40 signaling may play a role in the development and maintenance of B-cell hematological malignancies and some solid tumors. In vitro, dacetuzumab exhibited antitumor activity against several B-cell lymphoma and multiple myeloma (MM) cell lines, and induced direct apoptosis as well as the engagement of effective antibody-dependent cell-mediated cytotoxicity. In vivo, dacetuzumab demonstrated enhanced antitumor efficacy in combination with other mAbs and chemotherapeutic agents; many of these combinations are now being tested clinically. Early clinical trials have evaluated the pharmacokinetics, safety and efficacy of dacetuzumab monotherapy in patients with relapsed/refractory B-cell lymphomas or MM. Targeting CD40 with dacetuzumab resulted in modest antitumor activity in B-cell lymphomas and, to a lesser extent, in MM. In particular, patients with diffuse large B-cell lymphoma responded well to dacetuzumab; the drug is being pursued for this indication in phase II trials.