PS1159 POOLED ANALYSIS OF SAFETY DATA FROM MONOTHERAPY STUDIES OF THE BRUTON TYROSINE KINASE (BTK) INHIBITOR, ZANUBRUTINIB (BGB-3111), IN B-CELL MALIGNANCIES

Cardiovascular Risk Associated With Ibrutinib Use in Chronic Lymphocytic Leukemia: A Population-Based Cohort Study

PURPOSE

Ibrutinib reduces mortality in chronic lymphocytic leukemia (CLL). It increases the risk of atrial fibrillation (AF) and bleeding and there are concerns about heart failure (HF) and central nervous system ischemic events. The magnitude of these risks remains poorly quantified.

METHODS

Using linked administrative databases, we conducted a population-based cohort study of Ontario patients who were treated for CLL diagnosed between 2007 and 2019. We matched ibrutinib-treated patients with controls treated with chemotherapy but unexposed to ibrutinib on prior AF, age ≥ 66 years, anticoagulant exposure, and propensity for receiving ibrutinib. Study outcomes were AF-related health care contact, hospital-diagnosed bleeding, new diagnoses of HF, and hospitalizations for stroke and acute myocardial infarction (AMI). The cumulative incidence function was used to estimate absolute risks. We used cause-specific regression to study the association of ibrutinib with bleeding rates, while adjusting for anticoagulation as a time-varying covariate.

RESULTS

We matched 778 pairs of ibrutinib-treated and unexposed patients with CLL (N = 1,556). The 3-year incidence of AF-related health care contact was 22.7% (95% CI, 19.0 to 26.6) in ibrutinib-treated patients and 11.7% (95% CI, 9.0 to 14.8) in controls. The 3-year risk of hospital-diagnosed bleeding was 8.8% (95% CI, 6.5 to 11.7) in ibrutinib-treated patients and 3.1% (95% CI, 1.9 to 4.6) in controls. Ibrutinib-treated patients were more likely to start anticoagulation after the index date. After adjusting for anticoagulation as a time-varying covariate, ibrutinib remained positively associated with bleeding (HR, 2.58; 95% CI, 1.76 to 3.78). The 3-year risk of HF was 7.7% (95% CI, 5.4 to 10.6%) in ibrutinib-treated patients and 3.6% (95% CI, 2.2 to 5.4) in controls. There was no significant difference in the risk of ischemic stroke or AMI.

CONCLUSION

Ibrutinib is associated with higher risk of AF, bleeding, and HF, but not AMI or stroke.

Clinical pharmacology and PK/PD translation of the second-generation Bruton's tyrosine kinase inhibitor, zanubrutinib

Introduction: Bruton's tyrosine kinase (BTK) inhibitors have revolutionized the treatment of B-cell lymphomas. Zanubrutinib was designed to achieve improved therapeutic concentrations and minimize off-target activities putatively accounting, in part, for the adverse effects seen with other BTK inhibitors.Areas covered: This drug profile covers zanubrutinib clinical pharmacology and the translation of pharmacokinetics (PK) and pharmacodynamics (PD) to clinical efficacy and safety profiles, by highlighting key differences between zanubrutinib and other BTK inhibitors. We discuss PK, sustained BTK occupancy, and potential factors affecting PK of zanubrutinib, including food effects, hepatic impairment, and drug-drug interactions. These data, along with exposure-response analyses, were used to support the recommended dose of 320 mg, either once daily or as 160 mg twice daily. Translation of PK/PD attributes into clinical effects was demonstrated in a randomized, phase 3 head-to-head study comparing it with ibrutinib in patients with Waldenström macroglobulinemia.Expert opinion: Among the approved BTK inhibitors, zanubrutinib is less prone to PK modulation by intrinsic and extrinsic factors, leading to more consistent, sustained therapeutic exposures and improved dosing convenience. Zanubrutinib PK/PD has translated into durable responses and improved safety, representing an important new treatment option for patients who benefit from BTK therapy.

Zanubrutinib monotherapy for patients with treatment naïve chronic lymphocytic leukemia and 17p deletion

Patients with chronic lymphocytic leukemia or small lymphocytic lymphoma whose tumors carry deletion of chromosome 17p13.1 [del(17p)] have an unfavorable prognosis and respond poorly to standard chemoimmunotherapy. Zanubrutinib is a selective next-generation Bruton tyrosine kinase inhibitor. We evaluated the safety and efficacy of zanubrutinib 160 mg twice daily in treatment-naïve patients with del(17p) disease enrolled in a dedicated, nonrandomized cohort (Arm C) of the phase 3 SEQUOIA trial. A total of 109 patients (median age, 70 years; range, 42 - 86) with centrally confirmed del(17p) were enrolled and treated. After a median of 18.2 months (range, 5.0 - 26.3), seven patients had discontinued study treatment due to progressive disease, four due to an adverse event, and one due to withdrawal of consent. The overall response rate was 94.5% with 3.7% of patients achieving complete response with or without incomplete hematologic recovery. The estimated 18-month progression-free survival rate was 88.6% (95% CI, 79.0 - 94.0) and the estimated 18-month overall survival rate was 95.1% (95% CI, 88.4 - 98.0). Most common all-grade adverse events included contusion (20.2%), upper respiratory tract infection (19.3%), neutropenia/neutrophil count decreased (17.4%), and diarrhea (16.5%). Grade ≥ 3 adverse events were reported in 53 patients (48.6%), most commonly neutropenia (12.9%) and pneumonia (3.7%). An adverse event of atrial fibrillation was reported in three patients (2.8%). Zanubrutinib was active and well tolerated in this large, prospectively enrolled treatment cohort of previously untreated patients with del(17p) chronic lymphocytic leukemia/small lymphocytic lymphoma. This trial was registered at ClinicalTrials.gov as #NCT03336333.

Zanubrutinib for the treatment of relapsed or refractory mantle cell lymphoma

Zanubrutinib, a highly selective Bruton tyrosine kinase inhibitor, was evaluated in a phase 1/2 study in patients with various B-cell malignancies. In the subgroup of patients with relapsed/refractory (R/R) mantle cell lymphoma (MCL), zanubrutinib was administered as 160 mg twice daily (n = 14), 320 mg once daily (n = 18), or ≤160 mg total dose (n = 5). Herein, we report results for patients receiving a total daily dose of 320 mg (N = 32). Median study follow-up was 18.8 months. Eighteen patients discontinued treatment, 10 because of progressive disease and 8 because of adverse events (AEs); 1 AE (peripheral edema) was considered to be related to zanubrutinib treatment. The most common AEs were diarrhea (43.8%), contusion (37.5%), constipation (31.3%), and upper respiratory tract infection (31.3%). Infection was the most commonly reported AE of interest (18.8% of patients experienced grade ≥3 infection). At least 1 AE of grade ≥3 was reported in 59.4% of patients; grade ≥3 AEs that were reported in >2 patients were anemia (12.5%), pneumonia (9.4%), and myalgia (9.4%). Overall response rate was 84%, with 25% achieving a complete response. Median duration of response was 18.5 months. Median progression-free survival (PFS) was 21.1 months. Zanubrutinib was well tolerated and demonstrated activity in patients with R/R MCL. The trial is registered at www.clinicaltrials.gov as #NCT02343120.

Zanubrutinib (BGB-3111) plus obinutuzumab in patients with chronic lymphocytic leukemia and follicular lymphoma

Zanubrutinib (BGB-3111) is a next-generation Bruton tyrosine kinase inhibitor designed to be more selective with fewer off-target effects. We conducted a phase 1 study to assess the safety of its combination with obinutuzumab and evaluate early efficacy in 81 patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) or relapsed/refractory (R/R) follicular lymphoma (FL). In this phase 1b study, zanubrutinib was tolerable at 160 mg twice daily or 320 mg once daily combined with IV obinutuzumab in patients with CLL/SLL (n = 45) and FL (n = 36). Common adverse events (AEs) included upper respiratory tract infection (51%; n = 23), neutropenia (44%; n = 20), contusion (33%; n = 15), cough, diarrhea, or fatigue (27%; n = 12 each), and pyrexia (22%; n = 10) in CLL/SLL patients and upper respiratory tract infection (39%; n = 14), contusion (28%; n = 10), fatigue (25%; n = 9), and cough (22%; n = 8) in FL patients. Neutropenia was the most common grade 3/4 AE (CLL/SLL, 31% [n = 14]; FL, 14% [n = 5]). Five patients required temporary dose reductions, and 5 discontinued the study drug because of AEs. Overall response rate (ORR) was 100% (n = 20) in treatment-naïve CLL patients and 92% (n = 23) in R/R CLL patients. ORR in 36 R/R FL patients was 72% (n = 26), with 14 complete and 12 partial responses. Median follow-up was 29 months (range, 8-37) for CLL patients and 20 months (range, 2-37) for FL patients. Zanubrutinib and obinutuzumab combination therapy was generally well tolerated. This trial was registered at www.clinicaltrials.gov as #NCT02569476.

Zanubrutinib for the treatment of patients with Waldenström macroglobulinemia: 3 years of follow-up

Inhibitors of Bruton's tyrosine kinase (BTK) have established therapeutic activity in patients with Waldenström macroglobulinemia (WM). Zanubrutinib, a potent and selective BTK inhibitor, was evaluated in a phase 1/2 study in patients with WM who were either treatment-naïve (TN) or had relapsed/refractory (R/R) disease. Patients had disease requiring treatment per International Workshop on Waldenström Macroglobulinemia (IWWM) criteria. Treatment was 160 mg of oral zanubrutinib twice daily (n = 50) or 320 mg once daily (n = 23). Efficacy endpoints included overall response rate (ORR) and very good partial response/complete response (VGPR/CR) rates per IWWM-6 criteria (with modification of VGPR definition published previously). Between September 2014 and March 2018, 77 patients (24 TN and 53 R/R) began treatment. At a median follow-up of 36.0 months for patients with R/R disease and 23.5 months for TN, 72.7% remained on treatment. Reasons for treatment discontinuation included any adverse events in 13.0% of patients (1 treatment related), disease progression (10.4%), and other (3.9%). The ORR was 95.9%, and the VGPR/CR rate was 45.2%, which increased over time: 20.5% at 6 months, 32.9% at 12 months, and 43.8% at 24 months. Estimated 3-year progression-free survival rate was 80.5%, and overall survival rate was 84.8%. Adverse events of interest included contusion (32.5%, all grade 1), neutropenia (18.2%), major hemorrhage (3.9%), atrial fibrillation/flutter (5.2%), and grade 3 diarrhea (2.6%). Long-term treatment with single-agent zanubrutinib resulted in deep and durable responses in some patients with WM. The safety profile of long-term zanubrutinib therapy in these patients was acceptable. This trial was registered at www.clinicaltrials.gov as #NCT02343120.

Zanubrutinib (BGB-3111), a Second-Generation Selective Covalent Inhibitor of Bruton's Tyrosine Kinase and Its Utility in Treating Chronic Lymphocytic Leukemia

The understanding of the B cell receptor (BCR) pathway and its contribution to chronic lymphocytic leukemia (CLL) pathogenesis have led to the development of targeted BCR inhibitors which have transformed the treatment paradigm of CLL. Ibrutinib is a first-in-class oral Bruton’s tyrosine kinase (BTK) inhibitor which has demonstrated improvements in both progression free (PFS) and overall survival (OS) in both the treatment naïve and relapsed/refractory setting as compared to traditional chemoimmunotherapy. Despite its clinical efficacy, many patients discontinue treatment due to adverse events, which are thought to be mediated through off-target kinase inhibition. Zanubrutinib is a second-generation non-covalent BTK inhibitor with higher potency, allowing for inhibition of BTK with fewer off target effects. Early phase clinical trials have demonstrated excellent efficacy and a well-tolerated safety profile. Long-term follow-up is needed, but zanubrutinib holds promise to be an effective therapy for CLL with a manageable side effect profile and will be an exciting addition to our treatment paradigm.

Dermatological Toxicities of Bruton's Tyrosine Kinase Inhibitors

The development of Bruton's tyrosine kinase (BTK) inhibitors represents a major breakthrough in the treatment of chronic lymphocytic leukemia and other B cell malignancies. The first-generation inhibitor ibrutinib works by covalent irreversible binding to BTK, a non-receptor tyrosine kinase of the TEC (transient erythroblastopenia of childhood) family that plays a critical role in the B-cell receptor signaling pathway. It also induces an 'off-target' inhibition of a range of other kinases including (but not limited to) epidermal growth factor receptor (EGFR), SRC, and other kinases of the TEC family (interleukin-2-inducible T-cell kinase [ITK], Tec, BMX). Dermatological toxicities are among the most common toxicities of ibrutinib, but remain of mild to moderate intensity in most cases and are readily manageable. Their incidence is highest during the first year of treatment and declines over time. In addition, it has been postulated that ibrutinib-related dermatologic adverse events are mediated by the direct binding to both BTK and other 'off-target' kinases. Bruising, ecchymoses, and petechiae represent the most characteristic dermatologic adverse events. Nail and hair changes are also common, as skin infections (opportunistic infections including herpes simplex and herpes zoster virus reactivations, and Staphylococcus aureus superinfection), folliculitis, and other types of rashes. Panniculitis, aphthous-like ulcerations with stomatitis, neutrophilic dermatosis, peripheral edema, and skin cracking can also occur. Next-generation BTK inhibitors, acalabrutinib and zanubrutinib, have been designed to optimize BTK inhibition and minimize off-target inhibition of alternative kinases (Tec, ITK, EGFR, SRC-family kinases). These drugs have been recently FDA-approved for relapsed or refractory mantle cell lymphoma. Although the overall incidence of their toxicities is expected to be more limited, acalubrutinib and zanubrutinib are associated with a range of dermatologic toxic effects that appear to be similar to those previously described with ibrutinib, including bruising and ecchymoses, panniculitis, human herpesvirus infections, cellulitis, and skin rash. In particular, both drugs induce skin bleeding events in more than 30% of patients treated. However, the available dermatological data are still rather limited and will have to be consolidated prospectively. This review article analyses the wide spectrum of dermatological toxicities that can be encountered with first- and second-generation BTK inhibitors. Finally, recommendations for appropriate treatment as well as a synthesis algorithm for management are also proposed.

A Phase III study of zanubrutinib plus rituximab versus bendamustine plus rituximab in transplant-ineligible, untreated mantle cell lymphoma

Mantle cell lymphoma is an aggressive B-cell malignancy. Current frontline chemoimmunotherapies produce high response rates but relapse is inevitable. Furthermore, the elderly and those with comorbidities are precluded from standard regimens and stem cell transplant, leaving them with limited options. Targeted therapies, including Bruton tyrosine kinase inhibitors, are an effective treatment strategy in mantle cell lymphoma. Zanubrutinib is a potent next-generation Bruton tyrosine kinase inhibitor that has demonstrated complete and sustained Bruton tyrosine kinase occupancy, minimal off-target effects and favorable pharmacokinetic/pharmacodynamic properties. Described herein is an ongoing Phase III study comparing the efficacy and safety of zanubrutinib plus rituximab followed by zanubrutinib monotherapy versus bendamustine plus rituximab followed by observation in transplant-ineligible patients with previously untreated mantle cell lymphoma. Clinical Trial Registration: NCT04002297 (ClinicalTrials.gov).

An evaluation of zanubrutinib, a BTK inhibitor, for the treatment of chronic lymphocytic leukemia

INTRODUCTION

Recent years have seen a tremendous increase in the availability of therapeutic options for the management of patients with chronic lymphocytic leukemia (CLL). Notable among those are Bruton's tyrosine kinase (BTK) and b-cell lymphoma-2 (bcl-2) inhibitors.

AREAS COVERED

The authors provide a brief overview of the BTK signaling pathway as well as available, approved BTK inhibitors for CLL. In addition, they review pre-clinical and clinical data related to zanubrutinib and its use and CLL and other lymphoid malignancies.

EXPERT OPINION

Two BTK inhibitors are currently Food and Drug Administration (FDA) approved for use in CLL, and multiple additional agents are in development. Zanubrutinib is currently approved for the treatment of patients with relapsed mantle cell lymphoma and has demonstrated an impressive safety and efficacy profile. The choice of a specific BTK inhibitor for clinical use is dependent on its efficacy and relative toxicity profile. In addition, drug interactions also influence this decision. Zanubrutinib therefore provides an exciting option to utilize a specific BTK inhibitor with potentially limited toxicities. Additional comparative studies are currently underway to establish its advantage over currently available BTK inhibitors. Combination strategies are also being pursued to increase the depth and durability of remissions.

Evaluating the Therapeutic Potential of Zanubrutinib in the Treatment of Relapsed/Refractory Mantle Cell Lymphoma: Evidence to Date

Mantle cell lymphoma (MCL) is an uncommon B-cell non-Hodgkin lymphoma characterized by an aggressive clinical course in the majority of patients. Despite recent improvements in outcomes, MCL remains incurable and a major therapeutic challenge. BTK inhibitors are the preferred treatment option for patients with relapsed/refractory MCL, including those unfit for chemotherapy or those with chemoresistant disease. In addition to ibrutinib and acalabrutinib, the FDA recently approved zanubrutinib for the treatment of patients with relapsed/refractory MCL based on the results of two Phase 2 clinical trials showing overall response rates of 85–87% with complete responses in 30–77% of patients. Compared with ibrutinib, zanubrutinib is more selective for BTK and has less off-target inhibition, which is thought to limit certain toxicities although direct comparative data are still lacking. This review article summarizes data from clinical trials of currently FDA-approved BTK inhibitors in MCL with a focus on zanubrutinib.

Emerging therapies in mantle cell lymphoma

Mantle cell lymphoma (MCL) is a rare, B cell non-Hodgkin's lymphoma with highly heterogeneous clinical presentation and aggressiveness. First-line treatment consists of intensive chemotherapy with autologous stem cell transplant for the fit, transplant eligible patients, or less intensive chemotherapy for the less fit (and transplant-ineligible) patients. Patients eventually relapse with a progressive clinical course. Numerous therapeutic approaches have emerged over the last few years which have significantly changed the treatment landscape of MCL. These therapies consist of targeted approaches such as BTK and BCL2 inhibitors that provide durable therapeutic responses. However, the optimum combination and sequencing of these therapies is unclear and is currently investigated in several ongoing studies. Furthermore, cellular therapies such as chimeric antigen receptor (CAR) T cells and bispecific T cell engager (BiTe) antibodies have shown impressive results and will likely shape treatment approaches in relapsed MCL, especially after failure with BTK inhibitors. Herein, we provide a comprehensive review of past and ongoing studies that will likely significantly impact our approach to MCL treatment in both the frontline (for transplant eligible and ineligible patients) as well as in the relapsed setting. We present the most up to date results from these studies as well as perspectives on future studies in MCL.

Treatment of relapsed/refractory chronic lymphocytic leukemia/small lymphocytic lymphoma with the BTK inhibitor zanubrutinib: phase 2, single-arm, multicenter study

Background

Bruton tyrosine kinase (BTK) inhibitors have demonstrated a high degree of efficacy in the treatment of B cell malignancies characterized by constitutive B cell receptor activation, including chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL).

Methods

The efficacy and safety of zanubrutinib, an investigational highly selective BTK inhibitor, was evaluated in this single-arm, phase 2 study of Chinese patients with relapsed/refractory CLL/SLL. The primary endpoint was overall response rate as assessed by an independent review committee.

Results

Of the 91 evaluable patients, 77 (84.6%) achieved a response, with three (3.3%), 54 (59.3%), and 20 (22%) patients achieving a complete response, partial response, and partial response with lymphocytosis, respectively, after a median follow-up of 15.1 months. The estimated 12-month event-free rate for duration of response was 92.9%. The most commonly reported grade ≥ 3 adverse events (AEs) were neutropenia (44%), thrombocytopenia (15.4%), lung infection/pneumonia (13.2%), upper respiratory tract infection (9.9%), and anemia (8.8%). The 12-month overall survival rate was 96%. Eight (9.0%) patients discontinued zanubrutinib due to AEs, and seven (8.0%) patients required at least one dose reduction.

Conclusion

Treatment of patients with relapsed/refractory CLL/SLL with zanubrutinib was generally well tolerated and resulted in a high overall response rate, thereby conferring a favorable benefit-risk profile.

Trial registration

Prospectively registered in China public registry (CTR20160890) on December 7, 2016: http://www.chinadrugtrials.org.cn/. Retrospectively registered in ClinicalTrials.gov (NCT03206918) on July 2, 2017.

ALPINE: zanubrutinib versus ibrutinib in relapsed/refractory chronic lymphocytic leukemia/small lymphocytic lymphoma

Treatment standards for chronic lymphocytic leukemia (CLL) have been transformed with the advent of effective inhibitors of B-cell receptor signaling such as ibrutinib - a first-in-class inhibitor of BTK. Off-target kinase inhibitions by ibrutinib are thought to contribute to its adverse events. Zanubrutinib is a next-generation BTK inhibitor with minimal off-target effects, sustained BTK occupancy in peripheral blood mononuclear cells and lymph nodes from patients with B-cell malignancies and promising responses in patients with CLL. Described here is a head-to-head Phase III study comparing the efficacy and safety of zanubrutinib with those of ibrutinib in patients with CLL/small lymphocytic lymphoma in the relapsed/refractory setting.