Kathryn S. Kolibaba

Bruton Tyrosine Kinase Inhibitor Ibrutinib (PCI-32765) Has Significant Activity in Patients With Relapsed/Refractory B-Cell Malignancies

PURPOSE Survival and progression of mature B-cell malignancies depend on signals from the B-cell antigen receptor, and Bruton tyrosine kinase (BTK) is a critical signaling kinase in this pathway. We evaluated ibrutinib (PCI-32765), a small-molecule irreversible inhibitor of BTK, in patients with B-cell malignancies. PATIENTS AND METHODS Patients with relapsed or refractory B-cell lymphoma and chronic lymphocytic leukemia received escalating oral doses of ibrutinib. Two schedules were evaluated: one, 28 days on, 7 days off; and two, once-daily continuous dosing. Occupancy of BTK by ibrutinib in peripheral blood was monitored using a fluorescent affinity probe. Dose escalation proceeded until either the maximum-tolerated dose (MTD) was achieved or, in the absence of MTD, until three dose levels above full BTK occupancy by ibrutinib. Response was evaluated every two cycles. RESULTS Fifty-six patients with a variety of B-cell malignancies were treated over seven cohorts. Most adverse events were grade 1 and 2 in severity and self-limited. Dose-limiting events were not observed, even with prolonged dosing. Full occupancy of the BTK active site occurred at 2.5 mg/kg per day, and dose escalation continued to 12.5 mg/kg per day without reaching MTD. Pharmacokinetic data indicated rapid absorption and elimination, yet BTK occupancy was maintained for at least 24 hours, consistent with the irreversible mechanism. Objective response rate in 50 evaluable patients was 60%, including complete response of 16%. Median progression-free survival in all patients was 13.6 months. CONCLUSION Ibrutinib, a novel BTK-targeting inhibitor, is well tolerated, with substantial activity across B-cell histologies.

Protein tyrosine kinases and cancer.

4. Tyrosine kinase activation by mutation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F222 4.1. BCR–ABL and human leukemia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F222 4.2. TEL–ABL and human leukemia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F224 4.3. TEL–PDGF receptor and chronic myelomonocytic leukemia . . . . . . . . . . . . . . . . . . F224 4.4. ALK and lymphoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F225 4.5. RET and multiple endocrine neoplasia type 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . F226 4.6. Other mutations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F229

Randomized trial of bendamustine-rituximab or R-CHOP/R-CVP in first-line treatment of indolent NHL or MCL: the BRIGHT study

This randomized, noninferiority (NI), global, phase 3 study evaluated the efficacy and safety of bendamustine plus rituximab (BR) vs a standard rituximab-chemotherapy regimen (rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone [R-CHOP] or rituximab plus cyclophosphamide, vincristine, and prednisone [R-CVP]) for treatment-naive patients with indolent non-Hodgkins lymphoma or mantle cell lymphoma. Investigators preassigned the standard treatment regimen they considered most appropriate for each patient; patients were randomized to receive BR (n = 224) or standard therapy (R-CHOP/R-CVP, n = 223) for 6 cycles; 2 additional cycles were permitted at investigator discretion. Response was assessed by a blinded independent review committee. BR was noninferior to R-CHOP/R-CVP, as assessed by the primary end point of complete response rate (31% vs 25%, respectively; P = .0225 for NI [0.88 margin]). The overall response rates for BR and R-CHOP/R-CVP were 97% and 91%, respectively (P = .0102). Incidences of vomiting and drug-hypersensitivity reactions were significantly higher in patients treated with BR (P < .05), and incidences of peripheral neuropathy/paresthesia and alopecia were significantly higher in patients treated with standard-therapy regimens (P < .05). These data indicate BR is noninferior to standard therapy with regard to clinical response with an acceptable safety profile. This trial was registered at www.clinicaltrials.gov as #NCT00877006.

An open-label phase 2 trial of entospletinib (GS-9973), a selective spleen tyrosine kinase inhibitor, in chronic lymphocytic leukemia

Small-molecule inhibitors of kinases involved in B-cell receptor signaling are an important advance in managing lymphoid malignancies. Entospletinib (GS-9973) is an oral, selective inhibitor of spleen tyrosine kinase. This multicenter, phase 2 study enrolled subjects with relapsed or refractory chronic lymphocytic leukemia (CLL; n = 41) or non-Hodgkin lymphoma (n = 145). Participants received 800 mg entospletinib twice daily. We report efficacy outcomes in the CLL cohort (n = 41) and safety outcomes in all cohorts (N = 186). The primary end point was a progression-free survival (PFS) rate at 24 weeks in subjects with CLL. The PFS rate at 24 weeks was 70.1% (95% confidence interval [CI], 51.3%-82.7%); median PFS was 13.8 months (95% CI, 7.7 months to not reached). The objective response rate was 61.0% (95% CI, 44.5%-75.8%), including 3 subjects (7.3%) who achieved nodal response with persistent lymphocytosis. Fifty-four subjects (29.0%) had serious adverse events (SAEs). The most common treatment-emergent SAEs included dyspnea, pneumonia, febrile neutropenia, dehydration, and pyrexia. Common grade 3/4 laboratory abnormalities included neutropenia (14.5%) and reversible alanine aminotransferase/aspartate aminotransferase elevations (13.4%). Entospletinib demonstrates clinical activity in subjects with relapsed or refractory CLL with acceptable toxicity. This trial was registered at www.clinicaltrials.gov as #NCT01799889.

Results of a phase 2 study of bortezomib in patients with relapsed or refractory indolent lymphoma

This study evaluated the efficacy and safety of single-agent bortezomib in indolent B-cell lymphoma that had relapsed from or was refractory to rituximab. Sixty patients enrolled: 59 were treated with bortezomib 1.3 mg/m(2) on days 1, 4, 8, and 11 for up to eight 21-day cycles; responders could receive 4 additional cycles; maintenance was optional. Fifty-three evaluable patients completed more than 2 cycles. The median age was 70 years, 53% female, Ann Arbor stage III-IIIE (28%) and IV (65%); 43 patients (72%) had more than 2 prior regimens; and 6 patients went on to maintenance. Overall responses are as follows: 1 complete response (1.9%), 3 unconfirmed complete response (5.7%), 3 partial response (5.7%), 34 stable disease (64.2%), and 12 progressive disease (22.6%). Median time to response = 2.2 months (range, 1.2-5.3 months); duration of response = 7.9 months (2.8-21.3 months); 1-year survival was 73% and 2-year survival was 58%; median survival = 27.7 months (range, 1.4-30.9 months); median progression-free survival = 5.1 months (range, 0.2-27.7 months), median time to progression = 5.1 months (range, 0.2-27.7 months), and median event-free survival = 1.8 months (range, 0.2-27.7 months). Treatment-related grade 3 or 4 adverse events included: thrombocytopenia (20%), fatigue (10%), neutropenia (8.5%), and neuropathy and diarrhea (6.8% each). This study demonstrates that bortezomib has modest activity against marginal zone and follicular lymphoma; it has the potential for combination with other agents in low-grade lymphomas. Maintenance therapy should be explored further.

Interactions of CBL with BCR-ABL and CRKL in BCR-ABL-transformed Myeloid Cells

The Philadelphia chromosome, detected in virtually all cases of chronic myelogenous leukemia (CML), is formed by a reciprocal translocation between chromosomes 9 and 22 that fusesBCR-encoded sequences upstream of exon 2 of c-ABL. The BCR-ABL fusion creates a gene whose protein product, p210BCR-ABL, has been implicated as the cause of the disease. Although ABL kinase activity has been shown to be required for the transforming abilities of BCR-ABL and numerous substrates of the BCR-ABL tyrosine kinase have been identified, the requirement of most of these substrates for the transforming function of BCR-ABL is unknown. In this study we mapped a direct binding site of the c-CBL proto-oncogene to the SH2 domain of BCR-ABL. This interaction only occurs under conditions where c-CBL is tyrosine-phosphorylated. Despite the direct interaction of c-CBL with the SH2 domain of BCR-ABL, deletion of the SH2 domain of BCR-ABL did not result in an alteration in the complex formation of BCR-ABL and c-CBL, suggesting that another site of direct interaction between c-CBL and BCR-ABL exists or that another protein mediates an indirect interaction of c-CBL and BCR-ABL. Since CRKL, an SH2, SH3 domain-containing adapter protein is known to bind directly to BCR-ABL and also binds to tyrosine-phosphorylated c-CBL, the ability of CRKL to mediate a complex between c-CBL and BCR-ABL was examined.

Randomized phase 2 study of obinutuzumab monotherapy in symptomatic, previously untreated chronic lymphocytic leukemia

Obinutuzumab is a glycoengineered, type 2 anti-CD20 humanized antibody with single-agent activity in relapsed chronic lymphocytic leukemia (CLL). With other CD20 antibodies, a dose-response relationship has been shown. We therefore performed a randomized phase 2 study in symptomatic, untreated CLL patients to evaluate if an obinutuzumab dose response exists. Obinutuzumab was given at a dose of 1000 mg (100 mg IV day 1, 900 mg day 2, 1000 mg day 8 and day 15 of cycle 1; 1000 mg day 1 of cycles 2-8) or 2000 mg (100 mg IV day 1, 900 mg day 2, 1000 mg day 3, 2000 mg day 8 and day 15 of cycle 1; 2000 mg day 1 of cycles 2-8). The primary end point was overall response rate (ORR). Eighty patients were enrolled with similar demographics: median age 67 years, 41% high-risk Rai disease, and 10% del(17p)(13.1). ORR (67% vs 49%, P = .08) and complete response (CR) or CR with incomplete cytopenia response (20% vs 5%) favored 2000 mg obinutuzumab. Overall, therapy was well tolerated, and infusion events were manageable. This study demonstrates significant efficacy of obinutuzumab monotherapy, for 1000 mg as well as for 2000 mg, in untreated CLL patients with acceptable toxicity. Although exploratory, a dose-response relationship may exist, but its relevance to improving progression-free survival is uncertain and will require further follow-up. This trial was registered at www.clinicaltrials.gov as #NCT01414205.

Ublituximab (TG-1101), a novel glycoengineered anti-CD20 antibody, in combination with ibrutinib is safe and highly active in patients with relapsed and/or refractory chronic lymphocytic leukaemia: results of a phase 2 trial.

Ibrutinib is effective in patients with chronic lymphocytic leukaemia (CLL); however, treatment resistance remains a problem. Ublituximab is a novel, glycoengineered anti‐CD20 monoclonal antibody with single‐agent activity in relapsed CLL. We report the results of a phase 2 study evaluating combination therapy with ibrutinib and ublituximab in patients with relapsed or refractory CLL. Patients received ibrutinib 420 mg once daily. Ublituximab was administered on days 1, 8 and 15 of cycle 1 followed by day 1 of cycles 2–6. Response assessments were completed at cycles 3 and 6; patients then continued on ibrutinib monotherapy per standard of care. Forty‐one of 45 enrolled patients were evaluable for efficacy. Safety was consistent with prior experience for each drug, with infusion reactions the most prevalent adverse event. Combination therapy resulted in an overall response rate (ORR) of 88% at 6 months. In the 20 patients with high‐risk features (17p or 11q deletions or TP53 mutation) and evaluable for efficacy, the ORR was 95%, with three patients (15%) achieving negative minimal residual disease. Median time to response was 8 weeks. Ublituximab in combination with ibrutinib resulted in rapid and high response rates. The long‐term clinical benefit of ublituximab will be defined by an ongoing phase 3 trial (NCT 02301156).

Randomized Phase II Study of R-CHOP With or Without Bortezomib in Previously Untreated Patients With Non–Germinal Center B-Cell–Like Diffuse Large B-Cell Lymphoma

Purpose To evaluate the impact of the addition of bortezomib to rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) on outcomes in previously untreated patients with non-germinal center B-cell-like (non-GCB) diffuse large B-cell lymphoma (DLBCL). Patients and Methods After real-time determination of non-GCB DLBCL using the Hans immunohistochemistry algorithm, 206 patients were randomly assigned (1:1; stratified by International Prognostic Index [IPI] score) to six 21-day cycles of standard R-CHOP alone or R-CHOP plus bortezomib 1.3 mg/m2 intravenously on days 1 and 4 (VR-CHOP). The primary end point, progression-free survival (PFS), was evaluated in 183 patients with centrally confirmed non-GCB DLBCL who received one or more doses of study drug (91 R-CHOP, 92 VR-CHOP). Results After a median follow-up of 34 months, with 25% (R-CHOP) and 18% (VR-CHOP) of patients having had PFS events, the hazard ratio (HR) for PFS was 0.73 (90% CI, 0.43 to 1.24) with VR-CHOP ( P = .611). Two-year PFS rates were 77.6% with R-CHOP and 82.0% with VR-CHOP; they were 65.1% versus 72.4% in patients with high-intermediate/high IPI (HR, 0.67; 90% CI, 0.34 to 1.29), and 90.0% versus 88.9% (HR, 0.85; 90% CI, 0.35 to 2.10) in patients with low/low-intermediate IPI. Overall response rate with R-CHOP and VR-CHOP was 98% and 96%, respectively. The overall survival HR was 0.75 (90% CI, 0.38 to 1.45); 2-year survival rates were 88.4% and 93.0%, respectively. In the safety population (100 R-CHOP and 101 VR-CHOP patients), grade ≥ 3 adverse events included neutropenia (53% v 49%), thrombocytopenia (13% v 29%), anemia (7% v 15%), leukopenia (26% v 25%), and neuropathy (1% v 5%). Conclusion Outcomes for newly diagnosed, prospectively enrolled patients with non-GCB DLBCL were more favorable than expected with R-CHOP and were not significantly improved by adding bortezomib.

Demographics, treatment patterns, safety, and real-world effectiveness in patients aged 70 years and over with chronic lymphocytic leukemia receiving bendamustine with or without rituximab: a retrospective study

Objectives: Bendamustine is a unique cytotoxic agent active against various human malignancies, including chronic lymphocytic leukemia (CLL). In vitro studies suggest that cytotoxic activity of bendamustine on CLL-derived cells is synergized by rituximab. A retrospective chart review was conducted to characterize treatment-naïve outpatients and those with relapsed disease aged 70 years and over with CLL receiving bendamustine (with or without rituximab) and to evaluate real-world patterns of care, safety, and effectiveness. Methods: Using McKesson Specialty Care/US Oncology Network iKnowMed databases, 91 outpatients with at least two recorded visits and at least two cycles of bendamustine monotherapy or bendamustine–rituximab combination therapy were identified and included. Mean age at diagnosis and start of first therapy was 70.3 and 77.4 years respectively, and 63.7% of patients were men. Results: Observed overall response rate was 56.3% in pooled treatment-naïve patients [n = 9; complete response (CR) 18.8%; partial response (PR) 37.5%; nodular partial response (nPR) 0%] and 58.7% in pooled patients with relapsed disease (n = 44; CR 13.3%; PR 44.0%; nPR 1.3%). Median time to progressive disease has not been reached for the 16 treatment-naïve patients (median follow up 15.1 months), and was 18.4 months for those with relapsed disease (n = 73). No unexpected toxicities were observed. Overall rate of blood/bone marrow toxicities (all grades) was 40.7%; grade 3/4 rates were 18.8% in treatment-naïve patients and 25.3% in those with relapsed disease. Most frequent nonhematologic adverse events were fatigue and rash. Conclusion: In this retrospective chart review of 91 outpatients with CLL aged 70 years and over, bendamustine (with or without rituximab) was an effective therapeutic option with manageable toxicity.