Matthew S. Davids

Targeting BCL2 with Venetoclax in Relapsed Chronic Lymphocytic Leukemia

BACKGROUND New treatments have improved outcomes for patients with relapsed chronic lymphocytic leukemia (CLL), but complete remissions remain uncommon. Venetoclax has a distinct mechanism of action; it targets BCL2, a protein central to the survival of CLL cells. METHODS We conducted a phase 1 dose-escalation study of daily oral venetoclax in patients with relapsed or refractory CLL or small lymphocytic lymphoma (SLL) to assess safety, pharmacokinetic profile, and efficacy. In the dose-escalation phase, 56 patients received active treatment in one of eight dose groups that ranged from 150 to 1200 mg per day. In an expansion cohort, 60 additional patients were treated with a weekly stepwise ramp-up in doses as high as 400 mg per day. RESULTS The majority of the study patients had received multiple previous treatments, and 89% had poor prognostic clinical or genetic features. Venetoclax was active at all dose levels. Clinical tumor lysis syndrome occurred in 3 of 56 patients in the dose-escalation cohort, with one death. After adjustments to the dose-escalation schedule, clinical tumor lysis syndrome did not occur in any of the 60 patients in the expansion cohort. Other toxic effects included mild diarrhea (in 52% of the patients), upper respiratory tract infection (in 48%), nausea (in 47%), and grade 3 or 4 neutropenia (in 41%). A maximum tolerated dose was not identified. Among the 116 patients who received venetoclax, 92 (79%) had a response. Response rates ranged from 71 to 79% among patients in subgroups with an adverse prognosis, including those with resistance to fludarabine, those with chromosome 17p deletions (deletion 17p CLL), and those with unmutated IGHV. Complete remissions occurred in 20% of the patients, including 5% who had no minimal residual disease on flow cytometry. The 15-month progression-free survival estimate for the 400-mg dose groups was 69%. CONCLUSIONS Selective targeting of BCL2 with venetoclax had a manageable safety profile and induced substantial responses in patients with relapsed CLL or SLL, including those with poor prognostic features. (Funded by AbbVie and Genentech; ClinicalTrials.gov number, NCT01328626.).

Targeting the B-Cell Lymphoma/Leukemia 2 Family in Cancer

The B-cell lymphoma/leukemia 2 (BCL-2) family of proteins has attracted the attention of cancer biologists since the cloning of BCL-2 more than 25 years ago. In the intervening decades, the way the BCL-2 family controls commitment to programmed cell death has been greatly elucidated. Several drugs directed at inhibiting BCL-2 and related antiapoptotic proteins have been tested clinically, with some showing considerable promise, particularly in lymphoid malignancies. A better understanding of the BCL-2 family has also provided insight into how conventional chemotherapy selectively kills cancer cells and why some cancers are more chemosensitive than others. Further exploitation of our understanding of the BCL-2 family promises to offer improved predictive biomarkers for oncologists and improved therapies for patients with cancer.

Ipilimumab for Patients with Relapse after Allogeneic Transplantation

BACKGROUND Loss of donor-mediated immune antitumor activity after allogeneic hematopoietic stem-cell transplantation (HSCT) permits relapse of hematologic cancers. We hypothesized that immune checkpoint blockade established by targeting cytotoxic T-lymphocyte-associated protein 4 with ipilimumab could restore antitumor reactivity through a graft-versus-tumor effect. METHODS We conducted a phase 1/1b multicenter, investigator-initiated study to determine the safety and efficacy of ipilimumab in patients with relapsed hematologic cancer after allogeneic HSCT. Patients received induction therapy with ipilimumab at a dose of 3 or 10 mg per kilogram of body weight every 3 weeks for a total of 4 doses, with additional doses every 12 weeks for up to 60 weeks in patients who had a clinical benefit. RESULTS A total of 28 patients were enrolled. Immune-related adverse events, including one death, were observed in 6 patients (21%), and graft-versus-host disease (GVHD) that precluded further administration of ipilimumab was observed in 4 patients (14%). No responses that met formal response criteria occurred in patients who received a dose of 3 mg per kilogram. Among 22 patients who received a dose of 10 mg per kilogram, 5 (23%) had a complete response, 2 (9%) had a partial response, and 6 (27%) had decreased tumor burden. Complete responses occurred in 4 patients with extramedullary acute myeloid leukemia and 1 patient with the myelodysplastic syndrome developing into acute myeloid leukemia. Four patients had a durable response for more than 1 year. Responses were associated with in situ infiltration of cytotoxic CD8+ T cells, decreased activation of regulatory T cells, and expansion of subpopulations of effector T cells in the blood. CONCLUSIONS Our early-phase data showed that administration of ipilimumab was feasible in patients with recurrent hematologic cancers after allogeneic HSCT, although immune-mediated toxic effects and GVHD occurred. Durable responses were observed in association with several histologic subtypes of these cancers, including extramedullary acute myeloid leukemia. (Funded by the National Institutes of Health and others; ClinicalTrials.gov number, NCT01822509.).

Phase I First-in-Human Study of Venetoclax in Patients With Relapsed or Refractory Non-Hodgkin Lymphoma

Purpose B-cell leukemia/lymphoma-2 (BCL-2) overexpression is common in many non-Hodgkin lymphoma (NHL) subtypes. A phase I trial in patients with NHL was conducted to determine safety, pharmacokinetics, and efficacy of venetoclax, a selective, potent, orally bioavailable BCL-2 inhibitor. Patients and Methods A total of 106 patients with relapsed or refractory NHL received venetoclax once daily until progressive disease or unacceptable toxicity at target doses from 200 to 1,200 mg in dose-escalation and safety expansion cohorts. Treatment commenced with a 3-week dose ramp-up period for most patients in dose-escalation cohorts and for all patients in safety expansion. Results NHL subtypes included mantle cell lymphoma (MCL; n = 28), follicular lymphoma (FL; n = 29), diffuse large B-cell lymphoma (DLBCL; n = 34), DLBCL arising from chronic lymphocytic leukemia (Richter transformation; n = 7), Waldenström macroglobulinemia (n = 4), and marginal zone lymphoma (n = 3). Venetoclax was generally well tolerated. Clinical tumor lysis syndrome was not observed, whereas laboratory tumor lysis syndrome was documented in three patients. Treatment-emergent adverse events were reported in 103 patients (97%), a majority of which were grade 1 to 2 in severity. Grade 3 to 4 events were reported in 59 patients (56%), and the most common were hematologic, including anemia (15%), neutropenia (11%), and thrombocytopenia (9%). Overall response rate was 44% (MCL, 75%; FL, 38%; DLBCL, 18%). Estimated median progression-free survival was 6 months (MCL, 14 months; FL, 11 months; DLBCL, 1 month). Conclusion Selective targeting of BCL-2 with venetoclax was well tolerated, and single-agent activity varied among NHL subtypes. We determined 1,200 mg to be the recommended single-agent dose for future studies in FL and DLBCL, with 800 mg being sufficient to consistently achieve durable response in MCL. Additional investigations including combination therapy to augment response rates and durability are ongoing.

Idelalisib given front-line for treatment of chronic lymphocytic leukemia causes frequent immune-mediated hepatotoxicity

Idelalisib is a small-molecule inhibitor of PI3Kδ with demonstrated efficacy for the treatment of relapsed/refractory chronic lymphocytic leukemia (CLL). To evaluate idelalisib as front-line therapy, we enrolled 24 subjects in a phase 2 study consisting of 2 months of idelalisib monotherapy followed by 6 months of combination therapy with idelalisib and the anti-CD20 antibody ofatumumab. After a median follow-up period of 14.7 months, hepatotoxicity was found to be a frequent and often severe adverse event. A total of 19 subjects (79%) experienced either grade ≥1 ALT or AST elevation during the study, and 13 subjects (54%) experienced grade ≥3 transaminitis. The median time to development of transaminitis was 28 days, occurring before ofatumumab introduction. Younger age and mutated immunoglobulin heavy chain status were significant risk factors for the development of hepatotoxicity. Multiple lines of evidence suggest that this hepatotoxicity was immune mediated. A lymphocytic infiltrate was seen on liver biopsy specimens taken from 2 subjects with transaminitis, and levels of the proinflammatory cytokines CCL-3 and CCL-4 were higher in subjects experiencing hepatotoxicity. All cases of transaminitis resolved either by holding the drug, initiating immunosuppressants, or both, and rates of recurrent toxicity were lower in patients taking steroids when idelalisib was reinitiated. A decrease in peripheral blood regulatory T cells was seen in patients experiencing toxicity on therapy, which is consistent with an immune-mediated mechanism. These results suggest that caution should be taken as drugs within this class are developed for CLL, particularly in younger patients who have not received prior disease-specific therapy. This study was registered at www.clinicaltrials.gov as #NCT02135133.

Clonal evolution in patients with chronic lymphocytic leukaemia developing resistance to BTK inhibition

Resistance to the Brutons tyrosine kinase (BTK) inhibitor ibrutinib has been attributed solely to mutations in BTK and related pathway molecules. Using whole-exome and deep-targeted sequencing, we dissect evolution of ibrutinib resistance in serial samples from five chronic lymphocytic leukaemia patients. In two patients, we detect BTK-C481S mutation or multiple PLCG2 mutations. The other three patients exhibit an expansion of clones harbouring del(8p) with additional driver mutations (EP300, MLL2 and EIF2A), with one patient developing trans-differentiation into CD19-negative histiocytic sarcoma. Using droplet-microfluidic technology and growth kinetic analyses, we demonstrate the presence of ibrutinib-resistant subclones and estimate subclone size before treatment initiation. Haploinsufficiency of TRAIL-R, a consequence of del(8p), results in TRAIL insensitivity, which may contribute to ibrutinib resistance. These findings demonstrate that the ibrutinib therapy favours selection and expansion of rare subclones already present before ibrutinib treatment, and provide insight into the heterogeneity of genetic changes associated with ibrutinib resistance.

Venetoclax plus rituximab in relapsed or refractory chronic lymphocytic leukaemia: a phase 1b study.

BACKGROUND Selective BCL2 inhibition with venetoclax has substantial activity in patients with relapsed or refractory chronic lymphocytic leukaemia. Combination therapy with rituximab enhanced activity in preclinical models. The aim of this study was to assess the safety, pharmacokinetics, and activity of venetoclax in combination with rituximab. METHODS Adult patients with relapsed or refractory chronic lymphocytic leukaemia (according to the 2008 Modified International Workshop on CLL guidelines) or small lymphocytic lymphoma were eligible for this phase 1b, dose-escalation trial. The primary outcomes were to assess the safety profile, to determine the maximum tolerated dose, and to establish the recommended phase 2 dose of venetoclax when given in combination with rituximab. Secondary outcomes were to assess the pharmacokinetic profile and analyse efficacy, including overall response, duration of response, and time to tumour progression. Minimal residual disease was a protocol-specified exploratory objective. Central review of the endpoints was not done. Venetoclax was dosed daily using a stepwise escalation to target doses (200-600 mg) and then monthly rituximab commenced (375 mg/m2 in month 1 and 500 mg/m2 in months 2-6). Adverse events were graded according to the National Cancer Institute Common Terminology Criteria for adverse events version 4.0. Protocol-guided drug cessation was allowed for patients who achieved complete response (including complete response with incomplete marrow recovery) or negative bone marrow minimal residual disease. Analyses were done per protocol for all patients who commenced drug and included all patients who received at least one dose of venetoclax. Data were pooled across dose cohorts. Patients are still receiving therapy and follow-up is ongoing. The trial is registered at ClinicalTrials.gov, number NCT01682616. FINDINGS Between Aug 6, 2012, and May 28, 2014, we enrolled 49 patients. Common grade 1-2 toxicities included upper respiratory tract infections (in 28 [57%] of 49 patients), diarrhoea (27 [55%]), and nausea (25 [51%]). Grade 3-4 adverse events occurred in 37 (76%) of 49 patients; most common were neutropenia (26 [53%]), thrombocytopenia (eight [16%]), anaemia (seven [14%]), febrile neutropenia (six [12%]), and leucopenia (six [12%]). The most common serious adverse events were pyrexia (six [12%]), febrile neutropenia (five [10%]), lower respiratory tract infection, and pneumonia (each three [6%]). Clinical tumour lysis syndrome occurred in two patients (resulting in one death) who initiated venetoclax at 50 mg. After enhancing tumour lysis syndrome prophylaxis measures and commencing venetoclax at 20 mg, clinical tumour lysis syndrome did not occur. The maximum tolerated dose was not identified; the recommended phase 2 dose of venetoclax in combination with rituximab was 400 mg. Overall, 42 (86%) of 49 patients achieved a response, including a complete response in 25 (51%) of 49 patients. 2 year estimates for progression-free survival and ongoing response were 82% (95% CI 66-91) and 89% (95% CI 72-96), respectively. Negative marrow minimal residual disease was attained in 20 (80%) of 25 complete responders and 28 (57%) of 49 patients overall. 13 responders ceased all therapy; among these all 11 minimal residual disease-negative responders remain progression-free off therapy. Two with minimal residual disease-positive complete response progressed after 24 months off therapy and re-attained response after re-initiation of venetoclax. INTERPRETATION A substantial proportion of patients achieved an overall response with the combination of venetoclax and rituximab including 25 (51%) of 49 patients who achieved a complete response and 28 (57%) of 49 patients who achieved negative marrow minimal residual disease with acceptable safety. The depth and durability of responses observed with the combination offers an attractive potential treatment option for patients with relapsed or refractory chronic lymphocytic leukaemia and could allow some patients to maintain response after discontinuing therapy, a strategy that warrants further investigation in randomised studies. FUNDING AbbVie Inc and Genentech Inc.

Targeting the B cell receptor pathway in chronic lymphocytic leukemia

Abstract The B cell receptor (BCR) pathway plays a crucial role in the survival, proliferation and trafficking of chronic lymphocytic leukemia (CLL) cells. Inhibitors of the key kinases in this pathway, including spleen tyrosine kinase (SYK), mammalian target of rapamycin (mTOR), phosphoinositide 3’-kinase (PI3K) and Bruton’s tyrosine kinase (BTK), have been found in preclinical models to decrease CLL cell viability both directly and indirectly through modulation of the microenvironment. Recently, oral agents targeting each of these kinases have been explored in early phase clinical trials in patients with CLL. BCR pathway antagonists appear to be highly active in relapsed/refractory CLL, independent of high-risk disease markers such as del(17p). These agents have shown a unique pattern of inducing early transient lymphocytosis, which typically is associated with nodal response. Here, we review the biology of the BCR, the kinases within this pathway and their interaction with the CLL microenvironment. We also discuss data from recent and ongoing clinical trials of BCR antagonists. We address the development of potential biomarkers for response to these agents such as ZAP-70, IGHV status and CCL3, and discuss where these exciting new drugs may fit in the evolving landscape of CLL therapy.

The BCL2 selective inhibitor venetoclax induces rapid onset apoptosis of CLL cells in patients via a TP53-independent mechanism

BCL2 blunts activation of the mitochondrial pathway to apoptosis, and high-level expression is required for chronic lymphocytic leukemia (CLL) survival. Venetoclax (ABT-199) is a small-molecule selective inhibitor of BCL2 currently in clinical trials for CLL and other malignancies. In conjunction with the phase 1 first-in-human clinical trial of venetoclax in patients with relapsed or refractory CLL (M12-175), we investigated the mechanism of action of venetoclax in vivo, explored whether in vitro sensitivity assays or BH3 profiling correlated with in vivo responses in patients, and determined whether loss of TP53 function affected responses in vitro and in vivo. In all samples tested, venetoclax induced death of CLL cells in vitro at concentrations achievable in vivo, with cell death evident within 4 hours. Apoptotic CLL cells were detected in vivo 6 or 24 hours after a single 20-mg or 50-mg dose in some patients. The extent of mitochondrial depolarization by a BIM BH3 peptide in vitro was correlated with percentage reduction of CLL in the blood and bone marrow in vivo, whereas the half lethal concentration derived from standard cytotoxicity assays was not. CLL cell death in vitro and the depth of clinical responses were independent of deletion of chromosome 17p, TP53 mutation, and TP53 function. These data provide direct evidence that venetoclax kills CLL cells in a TP53-independent fashion by inhibition of BCL2 in patients and support further assessment of BH3 profiling as a predictive biomarker for this drug.

Serum free light chain analysis.

In a variety of hematologic malignancies, immunoglobulin light chains (LC) are overproduced clonally and circulate without being linked by disulphide bonds to the immunoglobulin heavy chain. The recent development of a robust assay known as κ and λ “free” LC (FLC) to quantify the levels of these unbound LC in the serum, and thereby determine their ratio, has led to an explosion of studies that demonstrate its utility in a wide range of hematologic disorders. This article summarizes laboratory testing for serum FLC, with a particular focus on clinical applications for the test. Am. J. Hematol., 2010.