Selective Bruton's Tyrosine Kinase Inhibitor Research Articles

Discovery of AS-1763: A Potent, Selective, Noncovalent, and Orally Available Inhibitor of Bruton's Tyrosine Kinase.

Although Bruton's tyrosine kinase (BTK) has been recognized as a validated drug target for the treatment of B-cell malignances, the emergence of clinical resistance to the first-generation covalent BTK inhibitors is becoming a serious concern. As a part of our effort to develop noncovalent BTK inhibitors, a series of novel pyrrolopyrimidines was identified as noncovalent inhibitors of both the wild-type and C481S mutant BTKs. Subsequent lead optimization led to the identification of an orally available, potent, and selective BTK inhibitor 13f (AS-1763) as a next-generation noncovalent BTK inhibitor. With significant efficacies in vivo tumor xenograft models, AS-1763 has advanced to phase 1 clinical trials.

The MAGNOLIA Trial: Zanubrutinib, a Next-Generation Bruton Tyrosine Kinase Inhibitor, Demonstrates Safety and Efficacy in Relapsed/Refractory Marginal Zone Lymphoma.

Marginal zone lymphoma (MZL) is an uncommon non-Hodgkin lymphoma with malignant cells that exhibit a consistent dependency on B-cell receptor signaling. We evaluated the efficacy and safety of zanubrutinib, a next-generation selective Bruton tyrosine kinase inhibitor, in patients with relapsed/refractory (R/R) MZL. Patients with R/R MZL were enrolled in the phase II MAGNOLIA (BGB-3111-214) study. The primary endpoint was overall response rate (ORR) as determined by an independent review committee (IRC) based on the Lugano 2014 classification. Sixty-eight patients were enrolled. After a median follow-up of 15.7 months (range, 1.6 to 21.9 months), the IRC-assessed ORR was 68.2% and complete response (CR) was 25.8%. The ORR by investigator assessment was 74.2%, and the CR rate was 25.8%. The median duration of response (DOR) and median progression-free survival (PFS) by independent review was not reached. The IRC-assessed DOR rate at 12 months was 93.0%, and IRC-assessed PFS rate was 82.5% at both 12 and 15 months. Treatment was well tolerated with the majority of adverse events (AE) being grade 1 or 2. The most common AEs were diarrhea (22.1%), contusion (20.6%), and constipation (14.7%). Atrial fibrillation/flutter was reported in 2 patients; 1 patient had grade 3 hypertension. No patient experienced major hemorrhage. In total, 4 patients discontinued treatment due to AEs, none of which were considered treatment-related by the investigators. Zanubrutinib demonstrated high ORR and CR rate with durable disease control and a favorable safety profile in patients with R/R MZL.

Discovery of novel BTK PROTACs for B-Cell lymphomas

Bruton's tyrosine kinase (BTK) is a key drug target for B-cell related malignancies. Irreversible covalent BTK inhibitors have been approved for the treatment of B-cell malignancies, yet BTK C481S mutation at the covalent binding site has caused drug-resistance of BTK covalent binding inhibitors. The proteolysis targeting chimera (PROTAC) technology increases the sensitivity to drug-resistant targets compared to classic inhibitors, which provides a new strategy for mutant BTK related B-cell malignancies. ARQ531, a reversible non-covalent BTK inhibitor that inhibits wild type (WT) and mutated BTK with high selectivity, could be an ideal warhead for PROTACs targeting the mutant BTK. Herein, we designed a novel series of PROTACs using the selective non-covalent BTK inhibitor ARQ531 as warhead, with the goal of improving the degradation of both wild-type and C481S mutant BTKs, and increasing the selectivity of BTK over other kinases. This effort will provide some basis for further preclinical study of BTK PROTACs as a novel strategy for treatment of B-cell lymphomas.

Novel Treatment Approaches in Relapsed/Refractory Mantle Cell Lymphoma

<h2>Introduction</h2> Treatment with Bruton tyrosine kinase inhibitors (BTKi) changed the treatment landscape in relapsed/refractory (R/R) MCL. There are currently three FDA-approved irreversible BTKi for the treatment of R/R MCL, including ibrutinib, the first approved BTKi, and the more selective BTKi, acalabrutinib and zanubrutinib. These agents have single-agent overall response rates (ORR) of 67%–84%, with a median progression-free survival of 13–22 months,^1–3 with improvement in durability of response when used as second-line therapy.⁴ Despite the high single-agent responses, nearly all patients will relapse, and overall survival (OS) after progression on BTKi therapy is poor.⁵ This has led to evaluating BTKi-containing combination therapies to improve the depth and durability of remissions and the need for other targeted approaches. Cellular therapy, in the form of chimeric antigen receptor T-cells (CAR-T), has also proven to be effective, with the recent approval of the first autologous CD19-directed product in R/R MCL. Other promising constructs are being investigated, but the optimal sequencing with BTKi treatment is unclear. Here, we will review novel therapies under investigation for the treatment of R/R MCL.

CLL-354: Pooled Analysis of Cardiovascular Events from Clinical Trials Evaluating Acalabrutinib Monotherapy in Patients with Chronic Lymphocytic Leukemia (CLL)

Context: Bruton tyrosine kinase (BTK) inhibitors are effective treatments for B-cell malignancies, but an increased incidence of cardiovascular (CV) toxicities has been observed with ibrutinib. Acalabrutinib is a next-generation, highly selective BTK inhibitor approved for chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma and mantle cell lymphoma. Objective: To characterize CV adverse events (AEs). Patients: Patients with CLL who received acalabrutinib monotherapy. Design: Pooled data from patients with CLL in 4 studies (NCT02029443; NCT02475681; NCT02970318; NCT02337829). Interventions: Acalabrutinib was given orally at total daily doses of 100 mg to 400 mg, later switched to 100 mg twice daily, and continued until disease progression (PD) or toxicity. Main Outcome Measures: Cardiac AEs and hypertension were examined. Results: Seven hundred sixty-two patients were included (median age: 67 years [range: 32–89]; median follow-up: 25.9 months [range: 0–58.5]). A total of 199 cardiac AEs of any grade (irrespective of treatment relationship) were reported in 129 patients (17%). Cardiac AEs led to treatment discontinuation in 7 patients (0.9%). The most frequent cardiac AEs reported in ≥2% of patients were atrial fibrillation (afib: n=34; 4%; afib/flutter: n=38; 5%), palpitations (n=23; 3%), and tachycardia (n=17; 2%). Overall, 91% (117/129) of patients with cardiac AEs had ≥1 CV risk factor before acalabrutinib initiation. Hypertension AEs were reported in 9% (67/762) of patients, among whom 46 (69%) had pre-existing hypertension and 18 (27%) had hypertension risk factors. Thirty-seven patients (5%) had 51 grade ≥3 cardiac AEs (grade 3: n=37; grade 4: n=12; grade 5: n=2). Grade ≥3 cardiac AEs of interest included afib (n=10; 1.3%), complete atrioventricular block (n=2; 0.3%), acute coronary syndrome (n=1; 0.1%), atrial flutter (n=1; 0.1%), second degree atrioventricular block (n=1; 0.1%), and ventricular fibrillation (n=1; 0.1%). Two patients experienced grade 5 AEs (cardiac failure congestive [n=1], acute myocardial infarction [n=1]). Most grade ≥3 events (43/51 [84%]) resolved (dose delay: n=15; drug withdrawal: n=4; no dose change: n=24). Conclusions: These data suggest a low risk of cardiac AEs with acalabrutinib treatment in patients with CLL. The safety of acalabrutinib versus ibrutinib in patients with high-risk CLL is being investigated in the phase 3, randomized ACE-CL-006 trial (NCT02477696). Bruton tyrosine kinase (BTK) inhibitors are effective treatments for B-cell malignancies, but an increased incidence of cardiovascular (CV) toxicities has been observed with ibrutinib. Acalabrutinib is a next-generation, highly selective BTK inhibitor approved for chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma and mantle cell lymphoma. To characterize CV adverse events (AEs). Patients with CLL who received acalabrutinib monotherapy. Pooled data from patients with CLL in 4 studies (NCT02029443; NCT02475681; NCT02970318; NCT02337829). Acalabrutinib was given orally at total daily doses of 100 mg to 400 mg, later switched to 100 mg twice daily, and continued until disease progression (PD) or toxicity. Cardiac AEs and hypertension were examined. Seven hundred sixty-two patients were included (median age: 67 years [range: 32–89]; median follow-up: 25.9 months [range: 0–58.5]). A total of 199 cardiac AEs of any grade (irrespective of treatment relationship) were reported in 129 patients (17%). Cardiac AEs led to treatment discontinuation in 7 patients (0.9%). The most frequent cardiac AEs reported in ≥2% of patients were atrial fibrillation (afib: n=34; 4%; afib/flutter: n=38; 5%), palpitations (n=23; 3%), and tachycardia (n=17; 2%). Overall, 91% (117/129) of patients with cardiac AEs had ≥1 CV risk factor before acalabrutinib initiation. Hypertension AEs were reported in 9% (67/762) of patients, among whom 46 (69%) had pre-existing hypertension and 18 (27%) had hypertension risk factors. Thirty-seven patients (5%) had 51 grade ≥3 cardiac AEs (grade 3: n=37; grade 4: n=12; grade 5: n=2). Grade ≥3 cardiac AEs of interest included afib (n=10; 1.3%), complete atrioventricular block (n=2; 0.3%), acute coronary syndrome (n=1; 0.1%), atrial flutter (n=1; 0.1%), second degree atrioventricular block (n=1; 0.1%), and ventricular fibrillation (n=1; 0.1%). Two patients experienced grade 5 AEs (cardiac failure congestive [n=1], acute myocardial infarction [n=1]). Most grade ≥3 events (43/51 [84%]) resolved (dose delay: n=15; drug withdrawal: n=4; no dose change: n=24). These data suggest a low risk of cardiac AEs with acalabrutinib treatment in patients with CLL. The safety of acalabrutinib versus ibrutinib in patients with high-risk CLL is being investigated in the phase 3, randomized ACE-CL-006 trial (NCT02477696).

Acalabrutinib in the treatment of chronic lymphocytic leukemia: a review of recent evidence

Chronic lymphocytic leukemia (CLL) treatment landscape has changed dramatically with the recently developed drugs targeting the B-cell receptor (BCR) signalling pathway. Acalabrutinib, a second generation Bruton tyrosine kinase inhibitor, was approved in 2020 in Russia for the treatment of patients with CLL. Acalabrutinib was developed as a more selective Bruton tyrosine kinase inhibitor then ibrutinib. This drug is aimed at reducing the adverse events that limit the use of ibrutinib, such as atrial fibrillation and bleeding. Phase I/II multicenter studies have demonstrated the efficacy and safety of acalabrutinib monotherapy in untreated CLL patients and in patients with relapsed/refractory CLL and ibrutinib intolerance. Phase III trials, ASCEND and ELEVATE-TN, compared acalabrutinib monotherapy and a combination of acalabrutinib and obinutuzumab versus standard therapies and demonstrated improved efficacy and tolerability of acalabrutinib. A phase III trial comparing acalabrutinib and ibrutinib monotherapy (ELEVATE-RR) is ongoing. The results of this study along with real-life clinical data could determine the place of acalabrutinib in CLL treatment.

Bruton's tyrosine kinase Inhibitors and Cardiotoxicity: More Than Just Atrial Fibrillation.

Purpose of ReviewThe purpose of this review is to summarize the epidemiology, mechanisms, and management of cardiovascular complications of Bruton’s Tyrosine Kinase inhibitors (BTKIs).Recent FindingsIbrutinib increases the risk of atrial fibrillation, bleeding, and hypertension compared with non-BTKI therapies. The evidence to support an association between ibrutinib and other cardiovascular complications including ventricular tachyarrhythmias or cardiomyopathy is limited. Ibrutinib metabolism can be inhibited by some medications used to treat cardiovascular complications. The cardiovascular effects of more selective BTKIs, such as acalabrutinib, remain to be determined.SummaryFuture research should address the mechanisms underlying the cardiovascular complications of BTKIs and how best to manage them. The risks and benefits of more selective BTKIs as compared with ibrutinib require further evaluation.

SY-1530, a highly selective BTK inhibitor, effectively treats B-cell malignancies by blocking B-cell activation.

Objective:B-cell antigen receptor (BCR) signaling is required to maintain the physiological functions of normal B cells and plays an important pathogenic role in B-cell malignancies. Bruton tyrosine kinase (BTK), a critical mediator of BCR signaling, is an attractive target for the treatment of B-cell malignancies. This study aimed to identify a highly potent and selective BTK inhibitor.Methods:Homogeneous time-resolved fluorescence assays were used to screen BTK inhibitors. Typhoon fluorescence imaging and Western blot analysis were used to confirm the effects of SY-1530 on the BCR signaling pathway. Additionally, the anti-tumor activities of SY-1530 were evaluated in TMD8 xenografts and spontaneous canine B-cell lymphoma.Results:We found a novel irreversible and non-competitive inhibitor of BTK, SY-1530, which provided dose-dependent and time-dependent inhibition. SY-1530 selectively bound to BTK rather than inducible T-cell kinase; consequently, it did not significantly affect T-cell receptor signaling and caused limited off-target effects. SY-1530 blocked the BCR signaling pathway through down-regulation of BTK activity, thus leading to impaired phosphorylation of BTK and its downstream kinases. Moreover, SY-1530 induced apoptosis in a caspase-dependent manner and efficaciously inhibited tumor growth in mouse xenograft models of B-cell malignancy (P < 0.001). SY-1530 also induced positive clinical responses in spontaneous canine B-cell lymphoma.Conclusions:SY-1530 is an irreversible and selective BTK inhibitor that shows inhibitory effects on B-cell malignancies by blocking the BCR signaling pathway. Therefore, it may be a promising therapeutic approach for the treatment of B-cell malignancies.

Abstract 1267: Combination therapy of JNJ-67856633, a novel, first-in-class MALT1 protease inhibitor, and JNJ-64264681, a novel BTK inhibitor, for the treatment of B-cell lymphomas

Abstract Background: Constitutive activation of the classical nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB) pathway is a clear driver of B-cell non-Hodgkin lymphomas (NHL). Bruton's Tyrosine Kinase (BTK) and Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1), which lies downstream of BTK, are key mediators of the classical NF-κB signaling pathway activated by BCR and TCR receptors. JNJ-67856633 is a first-in-class MALT1 protease inhibitor. JNJ-64264681 is a BTK inhibitor with improved selectivity against BTK. Blocking the BCR pathway at multiple points using these two orally bioavailable compounds could enhance clinical activity in B-cell lymphoma patients. Methods: JNJ-67856633 and JNJ-64264681 are currently being evaluated in phase 1 clinical trials designed to establish safety, PK, PD and the Recommended Phase 2 Dose (RP2D) of each agent. Results: JNJ-67856633 is a potent, selective, orally bioavailable, allosteric inhibitor of MALT1 protease activity. The compound inhibits proliferation of activated B-cell diffuse large B-cell lymphoma (ABC-DLBCL) cell lines bearing CD79b or CARD11 mutations as well as models mimicking resistance to covalent BTK inhibitors. JNJ-67856633 exhibits potent tumor growth inhibition in two human DLBCL xenograft models, OCI-Ly3 and OCI-Ly10, and mutation selected patient derived DLBCL xenografts. Furthermore, treatment with JNJ-67856633 leads to dose dependent inhibition of the generation of Tregs (CD4+CD25+FoxP3+) following CD3/28 stimulation in vitro, suggesting a potential immune modulatory role of MALT1 inhibition. JNJ-64264681 is an orally active small molecule that is a potent, selective, and irreversible covalent BTK inhibitor. JNJ-64264681 inhibits the growth of CD79b-mutant DLBCL cell lines in vitro and potently inhibits tumor growth in xenograft- or patient-derived DLBCL models in vivo. Treatment with JNJ-64264681 and JNJ-67856633 administered together demonstrated statistically significant tumor growth inhibition compared with vehicle control in two CD79b mutant mouse lymphoma models, one based on a DLBCL cell line (OCI-Ly10) and one based on a patient-derived DLBCL model (LY2298). In both models, the combination showed increased growth inhibition compared with single agents and tumor regression in the combination arm. Synergistic anti-proliferative activity was observed in three DLBCL cell lines carrying CD79b mutations and one MCL cell line. Conclusions: Taken together, the in vitro and in vivo data for JNJ-67856633 and JNJ-64264681 suggest that combination therapy can increase the anti-tumor effect of the monotherapies and provide a more sustained response, offering strong support for clinical investigation of the combination of these two novel agents. A phase 1b combination study is scheduled to initiate. Citation Format: Ulrike Philippar, Lorena Fontan, Ivo Cornelissen, Haopeng Rui, Sriram Balasubramanian, Marcello Gaudiano, Mariette Bekkers, Luc Van Nuffel, Tianbao Lu, Tianbao Lu, John Wiener, Mark Tichenor, Tony Greway, Kathryn Packman, Bie Verbist, Yusri Elsayed, Ricardo Attar, Jacqueline Bussolari, John Gerecitano. Combination therapy of JNJ-67856633, a novel, first-in-class MALT1 protease inhibitor, and JNJ-64264681, a novel BTK inhibitor, for the treatment of B-cell lymphomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1267.

M7583 Is a Highly Selective and Potent Second Generation BTK Inhibitor for Treatment of B-Cell Malignancies

▪The advent of ibrutinib has represented a new era in the treatment of B-cell malignancies, with remarkable clinical efficacy shown in previously difficult to treat lymphomas. Now, second generation Bruton's tyrosine kinase (BTK) inhibitors are in development with more refined pharmacologic profiles that maintain the potent anti-tumor effects of ibrutinib, but that improve upon overall tolerability and circumvent ibrutinib's inhibitory effect on antibody-dependent cell-mediated cytotoxicity (ADCC).M7583 is a potent, orally administered, highly selective, adenosine triphosphate (ATP)-competitive, second generation, irreversible inhibitor of BTK. Kinase specificity has been determined in vitro using the Merck Millipore Kinase Profiler panel. Only 3 kinases (Blk, BMX, and Txk) had IC50s within a 10-fold range of BTK (BTK IC50 = 18.5 nM; Blk IC50 = 77 nM; BMX IC50= 5 nM; Txk IC50 = 62 nM). Target inhibition was confirmed with a concentration dependent decrease in BTK auto-phosphorylation detected by western blot in the Ramos cell line (human Burkitt's B-cell lymphoma). To examine the impact of kinase selectivity on the overall efficacy of M7583, its preclinical activity was compared with that of ibrutinib in a series of in vitro studies. M7583 inhibited the growth of diffuse large B-cell lymphoma (DLBCL) cell lines and primary chronic lymphocytic leukemia (CLL) blasts. In vivo , treatment with M7583 inhibited tumor growth in mantle cell lymphoma cell line-derived xenografts and patient-derived xenograft (PDX) models of DLBCL with the activated B-cell like diffuse large B-cell lymphoma (ABC-DLBCL) subtype being the most sensitive to M7583; consistent with the findings for other BTK inhibitors. To examine the potential for inhibition of ADCC by therapeutic antibodies, M7583 and ibrutinib were combined with rituximab or an ADCC incompetent version of rituximab in ADCC cell lysis experiments. At clinically relevant concentrations, ibrutinib inhibited the ADCC mechanism of rituximab, whereas M7583 did not. Collectively, these findings show the potency and selectivity of M7583 for BTK, as well as its efficacy in models of B-cell malignancies. The safety and efficacy of M7583 is currently being investigated in Phase I/II trials in patients with B-cell malignancies. DisclosuresGoodstal:EMD Serono: Employment. Ma:EMD Serono: Employment. Lin:EMD Serono: Employment. Crandall:EMD Serono: Employment. Crowley:EMD Serono: Employment. Bender:EMD Serono: Employment. Iadevaia:EMD Serono: Employment. Clark:EMD Serono: Employment.

Zanubrutinib for the treatment of relapsed or refractory mantle cell lymphoma

AbstractZanubrutinib, 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.

A novel tricyclic BTK inhibitor suppresses B cell responses and osteoclastic bone erosion in rheumatoid arthritis.

Rheumatoid arthritis (RA) is characterized by joint leukocyte infiltration, synovial inflammation and bone damage result from osteoclastogenesis. Bruton's tyrosine kinase (BTK) is a key regulator of B cell receptor (BCR) and Fc gamma receptor (FcγR) signaling involved in the pathobiology of RA and other autoimmune disorders. SOMCL-17-016 is a potent and selective tricyclic BTK inhibitor, structurally distinct from other known BTK inhibitors. In present study we investigated the therapeutic efficacy of SOMCL-17-016 in a mouse collagen-induced arthritis (CIA) model and underlying mechanisms. CIA mice were administered SOMCL-17-016 (6.25, 12.5, 25 mg·kg-1·d-1, ig), or ibrutinib (25 mg·kg-1·d-1, ig) or acalabrutinib (25 mg·kg-1·d-1, ig) for 15 days. We showed that oral administration of SOMCL-17-016 dose-dependently ameliorated arthritis severity and bone damage in CIA mice; it displayed a higher in vivo efficacy than ibrutinib and acalabrutinib at the corresponding dosage. We found that SOMCL-17-016 administration dose-dependently inhibited anti-IgM-induced proliferation and activation of B cells from CIA mice, and significantly decreased anti-IgM/anti-CD40-stimulated RANKL expression in memory B cells from RA patients. In RANKL/M-CSF-stimulated RAW264.7 cells, SOMCL-17-016 prevented osteoclast differentiation and abolished RANK-BTK-PLCγ2-NFATc1 signaling. In summary, this study demonstrates that SOMCL-17-016 presents distinguished therapeutic effects in the CIA model. SOMCL-17-016 exerts a dual inhibition of B cell function and osteoclastogenesis, suggesting that it to be a promising drug candidate for RA treatment.

The role of acalabrutinib in adults with chronic lymphocytic leukemia

The treatment landscape of chronic lymphocytic leukemia (CLL) has significantly changed in the past decade. This paradigm shift is due to the introduction of novel agents to the field. The two major classes of drugs that have contributed to this dramatic evolution include the Bruton tyrosine kinase (BTK) inhibitors and BCL2 inhibitors. Ibrutinib was the first-in-class drug which was initially approved by the US Food and Drug Administration (FDA) for the treatment of patients with relapsed/refractory and later for patients with treatment-naïve CLL. Despite encouraging efficacy outcomes, its use has been associated with cardiovascular and gastrointestinal toxicities likely due to off-target inhibition of ITK, TEC and EGFR family kinases. The next generation of BTK inhibitors was developed to be more selective with less off-target inhibition with the prospect to improve tolerability without compromising efficacy. Acalabrutinib, a selective covalent BTK inhibitor, is a second generation BTK inhibitor. The focus of this review is on two major phase III trials that resulted in the FDA approval of acalabrutinib in 2019. The ELEVATE TN trial investigated acalabrutinib with or without obintuzumab versus chlorambucil–obinutuzumab in older and frail patients with previously untreated CLL. The ASCEND trial explored acalabrutinib versus chemoimmunotherapy in patients with relapsed/refractory CLL. Both trials demonstrated superiority of the acalabrutinib-containing arms in terms of both efficacy and tolerability. Unfortunately, the availability of new generation BTK inhibitors has not resulted in mitigating the financial toxicities associated with these potentially life-long treatments.

Ibrutinib Off-Target Inhibition Inhibits Antibody-Dependent Cellular Phagocytosis but Not Efferocytosis of CLL Cells

Background Combinations of different targeted therapies, including Bruton tyrosine kinase (BTK) inhibitors and anti-CD20 monoclonal antibodies (mAbs) could improve treatment for CLL. Unexpectedly, the combination of ibrutinib (IBR) with rituximab did not show additional clinical benefit. However, IBR inhibits many off-target molecules that may limit therapeutic mAb clinical effectiveness and a more selective BTK inhibitor, such as acalabrutinib (ACALA), could be more effective in combination with mAb therapy. Initial data from the ELEVATE TN trial support this possibility. IBR off-target effects on antibody-dependent cellular phagocytosis (ADCP), the major mechanism of therapeutic mAb activity could explain this difference. Additionally, IBR induces a higher and longer duration increase in circulating lymphocytes than ACALA. IBR off-target effects on efferocytosis, another phagocytic process involved in apoptotic cell removal, might explain this difference. Methods Using state-of-the-art direct kinetic measurements of phagocytosis by time-lapse video, (Chu et al. J Cell Sci 2020;133:jcs237883) we investigated the effects of IBR and ACALA on phagocytosis (ADCP or efferocytosis) by human monocyte-derived macrophages (hMDM) in vitro. Live cell time-lapse video of 10 μg/ml rituximab (Genentech) mediated ADCP of CLL cells by CellTracker Deep Red (CTDR, Thermofisher) labeled hMDM (20:1 CLL:hMDM cell ratio) either untreated or treated with IBR or ACALA (3-fold serial dilutions from 100 to 0.41 μM) was imaged in a stage-top environmental chamber (37°C and 5% CO2) mounted onto a Nikon Ti-Eclipse inverted microscope with an ELWD 20x/0.45NA S Plan Fluor Ph1 objective and an Andor Zyla 5.5 sCMOS camera. Images were captured sequentially every 4 min over 2.8 h. For each experiment (n = 18), duplicate or triplicate wells for each drug concentration were imaged. For efferocytosis, live cell time-lapse video imaging of phagocytosis of pHrodo iFL Red STP ester (pHrodo Red, Thermo Fisher Scientific) labeled apoptotic CLL cells by CTDR-labeled hMDM (20:1 CLL:hMDM cell ratio) either untreated or treated with IBR or ACALA (2-fold serial dilutions from 10 to 1.25 μM) was collected every 4 min over 2.8 h. For each experiment (n = 7), duplicate or triplicate wells for each drug concentration was imaged and analyzed. Finally, for efferocytosis, the intensity of pHrodo Red dye, a pH-sensitive dye that increases in intensity with acidic pH, as found in the endolysosomes, was measured in the pHrodo Red color channel and analyzed. Results IBR significantly inhibited ADCP at all measured drug concentrations (0.41 μM, p &amp;lt; 0.05; 1.2 μM, p &amp;lt; 0.01; 3.7 - 100 μM, p &amp;lt; 0.001). The mean peak free drug concentration (Cmax) achieved clinically by standard doses for IBR is ~0.5 μM. ACALA only significantly inhibited ADCP at the highest concentration (100 μM, p &amp;lt; 0.001). The Cmax achieved clinically by standard doses for ACALA is ~1.2 μM. ACALA did not inhibit efferocytosis or subsequent transition to endolysosomal compartment at all tested concentrations (p &amp;gt; 0.05). IBR did not inhibit efferocytosis (p &amp;gt; 0.05) and only inhibited transition to endolysosomal compartment at highest concentration tested (10 μM, p &amp;lt; 0.01) Conclusion Our study shows that BTK inhibition does not block ADCP and a more selective BTK inhibitor may prove effective in combination with therapeutic anti-CD20 mAbs. IBR off-target inhibition specifically blocks ADCP and not efferocytosis. Thus, IBR off-target inhibition of ADCP should be via proximal signaling by antibody Fc receptors and not subsequent downstream phagocytic mechanisms in common with efferocytosis. These results also imply the lack of BTK and IBR off-target molecules involvement in efferocytosis. Finally, the increased lymphocytosis seen with IBR compared to ACALA treatment in CLL cannot be explained by IBR off-target effects on efferocytosis. These findings provide a critical understanding of macrophage phagocytosis reduction by BTK inhibitor selectivity that will have important consequences for the development of combination targeted therapies with mAbs. Disclosures Chu: Acerta Pharma/AstraZeneca: Research Funding; Pfizer: Current equity holder in publicly-traded company, Divested equity in a private or publicly-traded company in the past 24 months; TG Therapeutics: Research Funding. Izumi:AstraZeneca: Current equity holder in publicly-traded company; Acerta Pharma: Current equity holder in private company, Ended employment in the past 24 months, Patents &amp; Royalties: Acalabrutinib patents (no royalties). Munugalavadla:Gilead Sciences: Current equity holder in publicly-traded company; AstraZeneca: Current equity holder in publicly-traded company; Acerta Pharma: Current Employment. Barr:Gilead: Consultancy; Morphosys: Consultancy; TG therapeutics: Consultancy, Research Funding; Seattle Genetics: Consultancy; Celgene: Consultancy; AstraZeneca: Consultancy, Research Funding; Janssen: Consultancy; Merck: Consultancy; Genentech: Consultancy; Abbvie/Pharmacyclics: Consultancy, Research Funding; Verastem: Consultancy. VanDerMeid:Acerta Pharma / AstraZeneca: Research Funding. Elliott:Acerta Pharma / AstraZeneca: Research Funding. Zent:Mentrik Biotech: Research Funding; TG Therapeutics, Inc: Research Funding; Acerta / Astra Zeneca: Research Funding.

Pooled Analysis of Safety Data from Clinical Trials of Orelabrutinib Monotherapy in Hematologic Malignancies

Background: Bruton tyrosine kinase (BTK) is one of the key kinases implicated in the pathogenesis of multiple B cell malignancies. Orelabrutinib is a novel, highly selective and potent irreversible BTK inhibitor with minimal activities against other kinases (ITK, EGFR, ERBB2, etc.). As thus orelabrutinib may avoid off-target related adverse events and shall have improved safety profiles comparing to other BTK inhibitors. Here we present the safety profile of orelabrutinib analyzed based on data from 5 ongoing clinical studies in B cell malignancies (Table 1). Methods: Safety data of 266 patients (pts) from 5 ongoing orelabrutinib monotherapy studies were pooled and analyzed. All pts have been treated with at least one dose of oral orelabrutinib at ≥150 mg daily. The analysis includes the frequency and severity of adverse events (AEs), AEs of special interest, and AEs leading to treatment discontinuation or dose modifications. Results: Safety data were pooled from 266 pts with median age of 60 years (range 35.0-79.0, 69.2% males). The median duration of exposure was 11.0 months (range 0.2-22.0). The most common (occurring in ≥15% of pts) AEs were neutropenia (28.6%), thrombocytopenia (25.9%), Upper respiratory tract infection (24.4%), leukopenia (18.0%), anemia (16.2%) and rash (15.8%). Treatment related serious AEs (SAEs) were reported in 14.7% pts. The most common treatment related SAEs included thrombocytopenia (3.0%), lung infection (3.0%), pneumonitis (1.9%), anemia (1.1%) and lymphadentis (0.8%), The safety profiles were comparable in pts with various subtypes of B cell malignancies. It's noted that orelabrutinib has much less frequency of BTK off-target related adverse events, such as atrial fibrillation, diarrhea, major hemorrhage etc. Among all 266 pts, only one patient was reported with one episode of transient grade 1 atrial fibrillation, and no grade ≥3 atrial fibrillation was observed. Diarrhea of any grade was 7.1% and only one case (0.4%) was reported as grade 3. The major hemorrhage, defined as serious or ≥ G3 bleeding of any site, or central nervous system bleeding of any grade, was rarely observed; as only one case of cerebral hemorrhage, in 65-year-old male patient with more than 10 years hypertension was reported; the other three cases were subcutaneous hemorrhage, vitreous hemorrhage and vitreous hemorrhage/retinal hemorrhage. The later 2 cases of vitreous hemorrhage and/or retinal hemorrhage were resulted from posterior vitreous detachment and macular degeneration and both events were assessed as unlikely related to the treatment. Among 266 pts, the second primary malignancies were reported in only one pt with r/r MCL during orelabrutinib treatment. Grade ≥3 infection occurred in 41 pts (15.4%); most common infections were upper respiratory tract infection and lung infection. Most of the AEs were occurred during the early treatment, the frequency of the new event occurrence was significantly decreased during the later cycles. Dose reductions due to AEs occurred in 15 pts (5.6%), and treatment discontinuation due to AEs in 5.3% of pts with 2.3% related to orelabrutinib. Conclusions: Orelabrutinib shows excellent safety profiles and tolerability across various B-cell malignancies in long-term treatment. These data suggested orelabrutinib as a favorable treatment choice including the combinational therapy for B-cell malignancies. . Disclosures Zhu: Beijing InnoCare Pharma Tech Co., Ltd: Current Employment. Zhao:Beijing InnoCare Pharma Tech Co., Ltd: Current Employment. Xu:Beijing InnoCare Pharma Tech Co., Ltd: Current Employment.

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

AbstractInhibitors 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.

Chemoproteomic Profiling of an Ibrutinib Analogue Reveals its Unexpected Role in DNA Damage Repair.

Ibrutinib is an FDA-approved drug to treat B-lymphoid malignancies, which functions mechanistically as a covalent inhibitor for Bruton's tyrosine kinase (BTK). During the course of screening more potent and selective BTK inhibitors, we discovered that MM2-48, an ibrutinib analogue that contains the alkynyl amide functional group in place of the acrylamide warhead, exhibits a much stronger cytotoxicity. Comparative chemoproteomic profiling of the targets of ibrutinib and MM2-48 revealed that the alkynyl amide warhead exhibits much higher reactivity in proteomes. Unexpectedly, MM2-48 covalently targets a functional cysteine in a BRCA2 and CDKN1A-interacting protein, BCCIP, and significantly inhibits DNA damage repair. Our findings suggest that simultaneous inhibition of BTK activity and DNA damage repair might be a more effective therapeutic strategy for combating B-cell malignancies.

HZ-A-005, a potent, selective, and covalent Bruton’s tyrosine kinase inhibitor in preclinical development

Bruton’s tyrosine kinase (BTK), a non-receptor tyrosine kinase, is a member of the Tec kinases family and is essential for B cell receptor (BCR) mediated signaling. BTK inhibitors such as ibrutinib hold a prominent role in the treatment of B cell malignancies. Here we disclose a potent, selective, and covalent BTK inhibitor, HZ-A-005, currently in preclinical development. HZ-A-005 demonstrated dose-dependent activity in two xenograft models of lymphoma in vivo. It showed highly favourable safety, pharmacokinetic (PK), and pharmacodynamic (PD) profiles in preclinical studies. On the basis of its potency, selectivity, and covalent mode of inhibition, HZ-A-005 reveals the potential to be a promising BTK inhibitor for a wide range of cancer indications.

Acalabrutinib: Managing Adverse Events and Improving Adherence in Patients With Mantle Cell Lymphoma.

Acalabrutinib is a selective Bruton tyrosine kinase inhibitor approved for patients with relapsed or refractory mantle cell lymphoma, an aggressive B-cell malignancy. Treatment-related adverse events (AEs) can have a negative effect on treatment adherence. This article aims to provide nurses with firsthand guidance so that they can better support patients with mantle cell lymphoma initiating acalabrutinib. Safety data from the acalabrutinib ACE-LY-004 phase 2 trial in 124 patients with relapsed or refractory mantle cell lymphoma were reviewed, and strategies implemented at the University of Texas MD Anderson Cancer Center to manage trial AEs are described. The most common AEs of any grade were headache and diarrhea, but no patients discontinued treatment because of them. When doses were missed or modified, patients were reeducated about the importance of adherence and how to manage AEs. Grade 1-2 AEs were managed with over-the-counter medication, if needed. These strategies allowed for the tracking of occurrences of nonadherence, providing the opportunity to advise and educate patients and to manage AEs more effectively.

Clinical and biological implications of target occupancy in CLL treated with the BTK inhibitor acalabrutinib

AbstractInhibition of the B-cell receptor pathway, and specifically of Bruton tyrosine kinase (BTK), is a leading therapeutic strategy in B-cell malignancies, including chronic lymphocytic leukemia (CLL). Target occupancy is a measure of covalent binding to BTK and has been applied as a pharmacodynamic parameter in clinical studies of BTK inhibitors. However, the kinetics of de novo BTK synthesis, which determines occupancy, and the relationship between occupancy, pathway inhibition and clinical outcomes remain undefined. This randomized phase 2 study investigated the safety, efficacy, and pharmacodynamics of a selective BTK inhibitor acalabrutinib at 100 mg twice daily (BID) or 200 mg once daily (QD) in 48 patients with relapsed/refractory or high-risk treatment-naïve CLL. Acalabrutinib was well tolerated and yielded an overall response rate (ORR) of partial response or better of 95.8% (95% confidence interval [CI], 78.9-99.9) and an estimated progression-free survival (PFS) rate at 24 months of 91.5% (95% CI, 70.0-97.8) with BID dosing and an ORR of 79.2% (95% CI, 57.9-92.9) and an estimated PFS rate at 24 months of 87.2% (95% CI, 57.2-96.7) with QD dosing. BTK resynthesis was faster in patients with CLL than in healthy volunteers. BID dosing maintained higher BTK occupancy and achieved more potent pathway inhibition compared with QD dosing. Small increments in occupancy attained by BID dosing relative to QD dosing compounded over time to augment downstream biological effects. The impact of BTK occupancy on long-term clinical outcomes remains to be determined. This trial was registered at www.clinicaltrials.gov as #NCT02337829.