Ibrutinib plus Bendamustine and Rituximab in Untreated Mantle-Cell Lymphoma.

BACKGROUND: Ibrutinib, a Bruton's tyrosine kinase inhibitor, may have clinical benefit when administered in combination with bendamustine and rituximab and followed by rituximab maintenance therapy in older patients with untreated mantle-cell lymphoma. METHODS: We randomly assigned patients 65 years of age or older to receive ibrutinib (560 mg, administered orally once daily until disease progression or unacceptable toxic effects) or placebo, plus six cycles of bendamustine (90 mg per square meter of body-surface area) and rituximab (375 mg per square meter). Patients with an objective response (complete or partial response) received rituximab maintenance therapy, administered every 8 weeks for up to 12 additional doses. The primary end point was progression-free survival as assessed by the investigators. Overall survival and safety were also assessed. RESULTS: Among 523 patients, 261 were randomly assigned to receive ibrutinib and 262 to receive placebo. At a median follow-up of 84.7 months, the median progression-free survival was 80.6 months in the ibrutinib group and 52.9 months in the placebo group (hazard ratio for disease progression or death, 0.75; 95% confidence interval, 0.59 to 0.96; P = 0.01). The percentage of patients with a complete response was 65.5% in the ibrutinib group and 57.6% in the placebo group (P = 0.06). Overall survival was similar in the two groups. The incidence of grade 3 or 4 adverse events during treatment was 81.5% in the ibrutinib group and 77.3% in the placebo group. CONCLUSIONS: Ibrutinib treatment in combination with standard chemoimmunotherapy significantly prolonged progression-free survival. The safety profile of the combined therapy was consistent with the known profiles of the individual drugs. (Funded by Janssen Research and Development and Pharmacyclics; SHINE ClinicalTrials.gov number, NCT01776840.).

SOX11+ Large B-Cell Neoplasms: Cyclin D1-Negative Blastoid/Pleomorphic Mantle Cell Lymphoma or Large B-Cell Lymphoma?

Large or blastoid B-cell neoplasms that are SOX11+ are a diagnostic dilemma and raise a differential diagnosis of cyclin D1-negative blastoid/pleomorphic mantle cell lymphoma (MCL) versus diffuse large B-cell lymphoma (DLBCL) or blastoid high-grade B-cell lymphoma (HGBL) with aberrant SOX11 expression. Here we report a study cohort of 13 SOX11+ large/blastoid B-cell neoplasms. Fluorescence in situ hybridization analysis was negative for CCND1 rearrangement in all 13 cases; 1 of 8 (12.5%) cases tested showed CCND2 rearrangement and 2 (25%) cases had extracopies of CCND2. Gene expression profiling showed that the study group had a gene expression signature similar to cyclin D1+ blastoid/pleomorphic MCL but different from DLBCL. Principal component analysis revealed that the cohort cases overlapped with cyclin D1+ blastoid/pleomorphic MCL but had minimal overlap with DLBCL. All patients in the cohort had clinicopathologic features similar to those reported for patients with cyclin D1+ MCL. We also performed a survey of SOX11 expression in a group of 85 cases of DLBCL and 24 cases of blastoid HGBL. SOX11 expression showed a 100% specificity and positive predictive value for the diagnosis of MCL. Overall, the results support the conclusion that large or blastoid B-cell neoplasms that are positive for SOX11 are best classified as cyclin D1-negative blastoid/pleomorphic MCL, and not as DLBCL or blastoid HGBL. We also conclude that SOX11 is a specific marker for the diagnosis of MCL, including cyclin D1-negative blastoid/pleomorphic MCL cases and should be performed routinely on blastoid/large B-cell neoplasms to help identify potential cases of cyclin D1-negative blastoid/pleomorphic MCL.

Therapeutic options for relapsed/refractory mantle cell lymphoma.

Mantle cell lymphoma (MCL) is an uncommon subtype of non-Hodgkin lymphoma in which immunochemotherapy, with or without high-dose therapy, and autologous stem cell transplantation remain standard frontline therapies. Despite their clear efficacy, patients inevitably relapse and require subsequent therapy. In this review, we discuss the key therapeutic approaches in the management of relapsed MCL, covering in depth the data supporting the use of covalent Bruton tyrosine kinase (BTK) inhibitors at first or subsequent relapse. We describe the outcomes of patients progressing through BTK inhibitors and discuss the mechanisms of covalent BTKi resistance and treatment options after covalent treatment with BTKi. Options in this setting may depend on treatment availability, patient's and physician's preference, and the patient's age and comorbidity status. We discuss the rapid recent development of anti-CD19 chimeric antigen receptor T-cell therapy, as well as the utility of allogenic stem cell transplantation and novel therapies, such as noncovalent, reversible BTK inhibitors; ROR1 antibody drug conjugates; and bispecific antibodies.

Structure of N-terminal domain of NPC1 reveals distinct subdomains for binding and transfer of cholesterol.

LDL delivers cholesterol to lysosomes by receptor-mediated endocytosis. Exit of cholesterol from lysosomes requires two proteins, membrane-bound Niemann-Pick C1 (NPC1) and soluble NPC2. NPC2 binds cholesterol with its isooctyl side chain buried and its 3beta-hydroxyl exposed. Here, we describe high-resolution structures of the N-terminal domain (NTD) of NPC1 and complexes with cholesterol and 25-hydroxycholesterol. NPC1(NTD) binds cholesterol in an orientation opposite to NPC2: 3beta-hydroxyl buried and isooctyl side chain exposed. Cholesterol transfer from NPC2 to NPC1(NTD) requires reorientation of a helical subdomain in NPC1(NTD), enlarging the opening for cholesterol entry. NPC1 with point mutations in this subdomain (distinct from the binding subdomain) cannot accept cholesterol from NPC2 and cannot restore cholesterol exit from lysosomes in NPC1-deficient cells. We propose a working model wherein after lysosomal hydrolysis of LDL-cholesteryl esters, cholesterol binds NPC2, which transfers it to NPC1(NTD), reversing its orientation and allowing insertion of its isooctyl side chain into the outer lysosomal membranes.

Ibrutinib-rituximab followed by R-HCVAD as frontline treatment for young patients (≤65 years) with mantle cell lymphoma (WINDOW-1): a single-arm, phase 2 trial.

BACKGROUND: Induction with ibrutinib and rituximab provides an opportunity to minimise chemotherapy exposure, because upfront use of these targeted therapies could result in remission without chemotherapy and allow for consolidation with only four cycles of chemotherapy instead of the conventional eight. We aimed to determine the activity and safety of ibrutinib-rituximab induction followed by shortened chemoimmunotherapy (four cycles) with rituximab plus hyper-fractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone (R-HCVAD) alternating with methotrexate-cytarabine in previously untreated patients with mantle cell lymphoma. METHODS: We did a single-centre, single-arm, phase 2 trial in previously untreated patients with mantle cell lymphoma. Eligible patients were aged 65 years or younger and had serum bilirubin of less than 1·5 mg/dL, creatinine clearance of 30 mL/min or more, Eastern Cooperative Oncology Group performance status of 2 or less, and cardiac ejection fraction 50% or more by echocardiogram. Patients received 12 cycles of ibrutinib-rituximab induction (part A; oral ibrutinib 560 mg daily and intravenous rituximab 375 mg/m2 weekly for the first 4 weeks and then on day 1 of cycles 3-12). As soon as patients had a complete response, four cycles of R-HCVAD alternating with methotrexate-cytarabine (part B) were administered. If they did not have a complete response or had a partial response, patients received two cycles of R-HCVAD alternating with methotrexate-cytarabine followed by reassessment, up to a total of eight cycles. Patients were taken off study if they had stable disease or progression during R-HCVAD. The primary outcome was the overall response rate after part A. The analyses were conducted on an intention-to-treat basis. This trial is registered with ClinicalTrials.gov, number NCT02427620. FINDINGS: 131 patients were enrolled between June 12, 2015, and Dec 6, 2018. The median age was 56 years (IQR 49-60). 58 (50%) of 117 patients had high Ki-67 (≥30%). 129 (98%, 95% CI 95-100) of 131 patients had an overall response in part A. The most common grade 3-4 adverse events were lymphocytopenia (19 [14%] of 131), skin rash (16 [12%]), thrombocytopenia (12 [9%]), infections (11 [8%]), and fatigue (ten [8%]) in part A and lymphocytopenia (96 [73%]), leukocytopenia (42 [32%]), thrombocytopenia (40 [30%]), and neutropenia (26 [20%]) in part B. There was one on-study death, which was not deemed to be treatment-related. INTERPRETATION: Induction with ibrutinib-rituximab in the frontline treatment of young patients with mantle cell lymphoma is active and safe. This approach allowed minimisation of the number of chemotherapy cycles, thereby reducing the adverse events associated with chemotherapy. Newer trials bringing the next-generation Bruton's tyrosine kinase inhibitors into the frontline setting might obviate the need for chemotherapy altogether in patients with mantle cell lymphoma. FUNDING: Pharmacyclics, Janssen.

Mantle cell lymphoma in 2022-A comprehensive update on molecular pathogenesis, risk stratification, clinical approach, and current and novel treatments.

The field of mantle cell lymphoma (MCL) has witnessed remarkable progress due to relentless advances in molecular pathogenesis, prognostication, and newer treatments. MCL consists of a spectrum of clinical subtypes. Rarely, atypical cyclin D1-negative MCL and in situ MCL neoplasia are identified. Prognostication of MCL is further refined by identifying somatic mutations (such as TP53, NSD2, KMT2D), methylation status, chromatin organization pattern, SOX-11 expression, minimal residual disease (MRD), and genomic clusters. Lymphoid tissue microenvironment studies demonstrated the role of B-cell receptor signaling, nuclear factor kappa B (NF-kB), colony-stimulating factor (CSF)-1, the CD70-SOX-11 axis. Molecular mechanism of resistance, mutation dynamics, and pathogenic pathways (B-cell receptor (BCR), oxidative phosphorylation, and MYC) were identified in mediating resistance to various treatments (bruton tyrosine kinase (BTK) inhibitors [ibrutinib, acalabrutinib]. Treatment options range from conventional chemoimmunotherapy and stem cell transplantation (SCT) to targeted therapies against BTK (covalent and noncovalent), Bcl2, ROR1, cellular therapy such as anti-CD19 chimeric antigen receptor therapy (CAR-T), and most recently bispecific antibodies against CD19 and CD20. MCL patients frequently relapse. Complex pathogenesis and the management of patients with progression after treatment with BTK/Bcl2 inhibitors and CAR-T (triple-resistant MCL) remain a challenge. Next-generation clinical trials incorporating newer agents and concurrent translational and molecular investigations are ongoing.

BRUIN MCL-321: phase III study of pirtobrutinib versus investigator choice of BTK inhibitor in BTK inhibitor naive mantle cell lymphoma.

Treatment with covalent Bruton tyrosine kinase inhibitors (BTKi) represents an important advance in the management of relapsed or refractory mantle cell lymphoma, but these treatments are not curative and many patients ultimately relapse. Pirtobrutinib, a highly selective, noncovalent (reversible) BTKi, inhibits both wild type and C481-mutant BTK with equal low nM potency, and has favorable oral pharmacology that enables continuous BTK inhibition throughout the dosing interval regardless of intrinsic rate of BTK turnover. Pirtobrutinib is well tolerated and has demonstrated promising efficacy in patients with poor prognosis B-cell malignancies following prior therapy, including covalent BTKi. This phase III, head-to-head, randomized study (NCT04662255) will evaluate whether pirtobrutinib is superior to investigator's choice of covalent BTKi in patients with previously treated, BTKi-naive mantle cell lymphoma.

MCL is an uncommon type of B-cell non-Hodgkin lymphoma, a cancer of the immune system. It starts in the part of the lymph node called the mantle zone, where unusual B cells gather and crowd out healthy B cells in the lymph nodes, spleen, bone marrow and/or other organs. MCL can be caused by inappropriate cell signaling. BTK has been identified as a key driver of unusual cell signaling and blocking BTK has been shown to help kill the cancer cells. Covalent (not reversible) BTK inhibitors have advanced the treatment of MCL, but the effectiveness of these treatments is limited by side effects and treatment resistance. Pirtobrutinib, a noncovalent (reversible) BTK inhibitor, has been shown to have manageable side effects and to be effective in patients with MCL following previous treatment, including treatment with covalent BTK inhibitors. The BRUIN MCL-321 study compares pirtobrutinib with three currently approved covalent BTK inhibitors (ibrutinib, acalabrutinib or zanubrutinib), in patients with MCL who have never received any form of BTK inhibitor. This trial will look at how many people live with the disease without it getting worse. Like other cancer treatments, pirtobrutinib may affect both healthy cells and tumor cells, which can result in side effects that will also be looked at in this study. This study is active and currently recruiting new patients who have received at least one previous therapy for MCL and have never been treated with a BTK inhibitor. Clinical Trial Registration: NCT04662255 (ClinicalTrials.gov).

EZH2 expression is associated with inferior overall survival in mantle cell lymphoma.

Enhancer of zeste homolog 2 (EZH2) is a catalytic component of the polycomb repressive complex 2 (PRC2) which reduces gene expression via trimethylation of a lysine residue of histone 3 (H3K27me3). Expression of EZH2 has not been assessed systematically in mantle cell lymphoma (MCL). Expression of EZH2 was assessed by immunohistochemistry in 166 patients with MCL. We also assessed other PRC2 components and H3K27me3. Fifty-seven (38%) of MCL patients were positive for EZH2 using 40% cutoff. EZH2 expression was associated with aggressive histologic variants (65% vs. 29%, p < 0.001), high Ki-67 proliferation rate (median, 72% vs. 19%, p < 0.001), and p53 overexpression (43% vs. 2%, p < 0.001). EZH2 expression did not correlate with expression of other PRC2 components (EED and SUZ12), H3K27me3, MHC-I, and MHC-II. Patients with EZH2 expression (EZH2+) had a poorer overall survival (OS) compared with patients without EZH2 expression (EZH2-) (median OS: 3.9 years versus 9.4 years, respectively, p < 0.001). EZH2 expression also predicted a poorer prognosis in MCL patients with classic histology (median OS, 4.6 years for EZH2+ and 9.6 years for EZH2-negative, respectively, p < 0.001) as well as aggressive histology (median OS, 3.7 years for EZH2+ and 7.9 years for EZH2-negative, respectively, p = 0.046). However, EZH2 expression did not independently correlate with overall survival in a multivariate analysis. Gene expression analysis and pathway enrichment analysis demonstrated a significant enrichment in cell cycle and mitotic transition pathways in MCL with EZH2 expression. EZH2 expression detected by immunohistochemistry is present in 38% of MCL cases and it is associated with high proliferation rate, p53 overexpression, aggressive histologic variants, and poorer OS. Based on gene expression profiling data, EZH2 expression could potentiate cell cycle machinery in MCL. These data suggest that assessment of EZH2 expression could be useful to stratify MCL patients into low- and high-risk groups.

Efficacy of venetoclax in high risk relapsed mantle cell lymphoma (MCL) - outcomes and mutation profile from venetoclax resistant MCL patients.

Venetoclax is effective in relapsed patients with mantle cell lymphoma (MCL). Mechanisms of resistance to venetoclax in MCL are poorly understood. We describe the clinical outcomes and genomic characteristics of 24 multiply relapsed patients (median of five prior lines of therapy) who received venetoclax-based therapies; 67% had progressed on BTK inhibitors (BTKi) and 54% had blastoid or pleomorphic histology. Median follow up after venetoclax treatment was 17 months. The overall response rate was 50% and complete response (CR) rate was 21%, 16 patients had progressed and 15 died. The median progression free, overall and post venetoclax survival were 8, 13.5 and 7.3 months respectively. Whole-exome sequencing (WES) was performed on samples collected from seven patients (including five pairs; before starting venetoclax and after progression on venetoclax). The SMARCA4 and BCL2 alterations were noted only after progression, while TP53, CDKN2A, KMT2D, CELSR3, CCND1, NOTCH2 and ATM were altered 2-4-fold more frequently after progression. In two patients with serial samples, we demonstrated clonal evolution of novel SMARCA4 and KMT2C/D mutations at progression. Mutation dynamics in venetoclax resistant MCL is demonstrated. Our data indicates that venetoclax resistance in MCL is predominantly associated with non-BCL2 gene mutations. Further studies are ongoing in MCL patients to evaluate the efficacy of venetoclax in combination with other agents and understand the biology of venetoclax resistance in MCL.

Encouraging activity for R-CHOP in advanced stage nodular lymphocyte-predominant Hodgkin lymphoma.

Nodular lymphocyte Hodgkin lymphoma (NLPHL) is a rare disease for which the optimal therapy is unknown. We hypothesized that rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) could decrease rates of relapse and transformation. We retrospectively reviewed patients with NLPHL diagnosed between 1995 and 2015 confirmed by central pathologic review. Fifty-nine had sufficient treatment and follow-up data for analysis. We described progression-free survival (PFS), overall survival (OS), and histologic transformation according to treatment strategy and explored prognostic factors for PFS and OS. The median age at diagnosis was 41 years; 75% were male, and 61% had a typical growth pattern. Twenty-seven patients were treated with R-CHOP with an overall response rate of 100% (complete responses 89%). The median follow-up was 6.7 years, and the estimated 5- and 10-year PFS rates for patients treated with R-CHOP were 88.5% (95% confidence interval [CI], 68.4% to 96.1%) and 59.3 (95% CI, 25.3% to 89.1%), respectively. Excluding patients with histologic transformation at diagnosis, the 5-year cumulative incidence of histologic transformation was 2% (95% CI, 87% to 100%). No patient treated with R-CHOP experienced transformation. A high-risk score from the German Hodgkin Study Group was adversely prognostic for OS (P = .036), whereas male sex and splenic involvement were adversely prognostic for PFS (P = .006 and .002, respectively) but not OS. Our data support a potential role for R-CHOP in patients with NLPHL. Larger prospective trials are needed to define the optimal chemotherapy regimen.

Four-year follow-up of a single arm, phase II clinical trial of ibrutinib with rituximab (IR) in patients with relapsed/refractory mantle cell lymphoma (MCL).

Ibrutinib has shown significant activity in patients with relapsed or refractory mantle cell lymphoma (RR-MCL). We report the long-term outcome and safety profile of a single-centre, single arm, open-label, phase 2 study of RR-MCL treated with IR. Overall, the median follow-up time was 47 months (range 1-52 months), median duration on treatment was 16 months (range 1-53 months) and median number of treatment cycles was 17 (range 1-56). Twenty-nine patients (58%) achieved complete remission and of these, 12 patients continue on study. Thirty-eight patients discontinued treatment, 14 due to disease progression (2 transformed). Patients with blastoid morphology, high risk MCL International Prognostic Index score and high Ki67% had inferior survival. The commonest grade 1-2 toxicities were fatigue, diarrhoea, nausea, arthralgias and myalgias. None had long term toxicities. Median progression-free survival was 43 months. Eighteen patients (36%) died (14 deaths were MCL-related). The median overall survival has not been reached. Treatment with IR can provide durable remissions in a subset of patients with RR-MCL, especially those with low Ki67%. The possible benefit of adding other therapies in combination with IR in RR-MCL is under exploration.

Long-term outcomes and mutation profiling of patients with mantle cell lymphoma (MCL) who discontinued ibrutinib.

Long term outcomes and mutations in patients with mantle cell lymphoma (MCL) who discontinued ibrutinib have not been described. Using deep targeted next generation sequencing, we performed somatic mutation profiling from 15 MCL patients (including 5 patients with paired samples; before and after progression on ibrutinib). We identified 80 patients with MCL who discontinued ibrutinib therapy for various reasons. Median follow-up after ibrutinib discontinuation was 38 months. The median duration on ibrutinib was 7·6 months. Forty-one (51%) patients discontinued ibrutinib due to disease progression/transformation, 20 (25%) for intolerance, 7 (9%) due to patient choice, 5 (6%) for stem cell transplant, 4 (5%) due to second cancers and 3 (4%) other causes. The median survival after ibrutinib was 10 and 6 months for disease progression and transformation, respectively, and 25 months for patients with ibrutinib intolerance. Overall, BTK mutations were observed in 17% patients after progression on ibrutinib. Notably, TP53 alterations were observed after progression in 75% patients. Among the 4 patients with blastoid transformation, 3 (75%) had NSD2 mutations (co-existing with TP53). Ibrutinib-refractory MCL patients had a short survival. Demonstration of TP53 and NSD2 mutations in patients who developed blastoid transformation and ATM and TP53 mutations in patients who progressed, opens the door for future investigations in ibrutinib-refractory MCL.

Frontline Treatment for Older Patients with Mantle Cell Lymphoma.

The natural history of mantle cell lymphoma (MCL) undergoing chemotherapy is a cyclical pattern of remission followed by recurrence of disease due to acquired chemotherapy resistance. The median age of the occurrence of MCL is 65 years, so half of the newly diagnosed MCL patients are considered "elderly." The tolerance to long-term chemotherapy in elderly patients is decreased; hence, the response to frontline therapy used is of paramount importance. We hope that our review may guide clinicians in treating such populations in a more personalized and evidence-based manner.In the older patients with risk variables, frontline treatment is determined according to different body status of fit, unfit or compromised, and frail. In the fit patients, the pursuit of remission and prolongation of survival might currently justify the use of more intense and toxic therapies. For unfit or compromised older patients, disease control needs to be prioritized, maintaining a balance between the benefits and toxicities of the treatment. For frail patients, tolerance of treatment and minimizing myelotoxicity should be the primary focus. "Chemotherapy-free" regimens are likely to be considered as the first-line strategy for this population. On the other hand, in the older MCL population without risk variables, observation or "watch and wait" can prevent overtreatment. Furthermore, more clinical trials and research studies on novel agents and targeted therapies need to be translated into the general population to provide optimal treatment and to guide personalized treatment. IMPLICATIONS FOR PRACTICE: This review emphasizes the importance of frontline therapies for older MCL patients. MCL patients commonly experience a cyclical pattern of remission followed by recurrence of disease due to acquired chemotherapy resistance. As a special population, elderly patients have various comorbidities and decreased organ function, which may reduce the chances of undergoing treatment for recurrent disease. Thus, this older population of patients with MCL should be treated separately and exceptionally. So far, systematic reviews with regard to frontline treatment for older patients with MCL have not been encountered, but the hope is that this review may guide clinicians in treating such populations in a more personalized and evidence-based manner.

Malignant melanoma with osteosarcomatous differentiation in a lymph node metastasis.

Osteocartilaginous differentiation in malignant melanoma is rare and can pose a diagnostic challenge. In previously reported cases, melanomas were predominantly located on acral and mucosal sites, with osteocartilaginous differentiation present in either primary or recurrent lesions. We report a case of a 52-year-old female with malignant melanoma located on the right upper back exhibiting osteosarcomatous differentiation only in the axillary lymph node metastasis. This case serves to highlight that the divergent differentiation can occur in lymph node metastases while being absent in the primary lesion. The patient's medical history, careful histological examination, and immunohistochemistry may be necessary for establishing the correct diagnosis.

Comparative Analysis of Chilblain Lupus Erythematosus and Idiopathic Perniosis: Histopathologic Features and Immunohistochemistry for CD123 and CD30.

Distinction of chilblain lupus erythematosus (CLE) from idiopathic perniosis (IP) could predict an underlying connective tissue disease; however, histopathologic discrimination of the two is difficult. Increased CD123 plasmacytoid dendritic cells and CD30 lymphocytes have been demonstrated in various forms of cutaneous lupus erythematosus and IP, respectively. To our knowledge, CD123 and CD30 have not been examined in CLE. Our objective was to identify helpful histopathologic and immunohistochemical features in distinguishing CLE and IP. Skin biopsies classified as CLE (n = 20) and IP (n = 39) based on clinicopathologic correlation were collected from 2000 to 2015. Various histopathologic features were examined on hematoxylin and eosin and alcian blue stains. CD123 and CD30 immunostains were performed and characterized. We identified dermal interstitial fibrin exudate (P = 0.0352) and increased dermal mucin (P = 0.0002) as features significantly associated with CLE. Other histopathologic features and CD123 failed to distinguish between groups. CD30 lymphocytes were sparse in all cases. Despite being the largest series of CLE and IP to date, the number of CLE cases in this study remained relatively limited, and some patients in the IP group may have yet to develop diagnostic features of systemic lupus erythematosus. In conclusion, histopathologic distinction between CLE and IP remains challenging. Interstitial fibrin and abundant dermal mucin help favor CLE. The number and distribution of CD123 plasmacytoid dendritic cells and CD30 lymphocytes have no discriminatory role.

Targeting Bruton's tyrosine kinase for the treatment of B cell associated malignancies and autoimmune diseases: Preclinical and clinical developments of small molecule inhibitors.

B cell receptor (BCR) signaling plays a key role in B cell development and function. Aberrant BCR signaling has been confirmed as a central driver for the pathogenesis of various B cell malignancies. Bruton's tyrosine kinase (BTK) is a vital component of BCR signaling and exhibits overexpression in various B cell leukemias and lymphomas. Inhibiting BTK has been proved as an efficient way for B cell malignancy intervention. Remarkable achievements have been made in the pursuit of selective BTK inhibitors, represented by the success of the irreversible BTK inhibitors, ibrutinib and acalabrutinib. Constantly emerging agents exhibiting superior efficacy and safety in preclinical and clinical studies provide promising therapeutics for the treatment of B cell malignancies.

Synergistic activity of BET protein antagonist-based combinations in mantle cell lymphoma cells sensitive or resistant to ibrutinib.

Mantle cell lymphoma (MCL) cells exhibit increased B-cell receptor and nuclear factor (NF)-κB activities. The bromodomain and extra-terminal (BET) protein bromodomain 4 is essential for the transcriptional activity of NF-κB. Here, we demonstrate that treatment with the BET protein bromodomain antagonist (BA) JQ1 attenuates MYC and cyclin-dependent kinase (CDK)4/6, inhibits the nuclear RelA levels and the expression of NF-κB target genes, including Bruton tyrosine kinase (BTK) in MCL cells. Although lowering the levels of the antiapoptotic B-cell lymphoma (BCL)2 family proteins, BA treatment induces the proapoptotic protein BIM and exerts dose-dependent lethality against cultured and primary MCL cells. Cotreatment with BA and the BTK inhibitor ibrutinib synergistically induces apoptosis of MCL cells. Compared with each agent alone, cotreatment with BA and ibrutinib markedly improved the median survival of mice engrafted with the MCL cells. BA treatment also induced apoptosis of the in vitro isolated, ibrutinib-resistant MCL cells, which overexpress CDK6, BCL2, Bcl-xL, XIAP, and AKT, but lack ibrutinib resistance-conferring BTK mutation. Cotreatment with BA and panobinostat (pan-histone deacetylase inhibitor) or palbociclib (CDK4/6 inhibitor) or ABT-199 (BCL2 antagonist) synergistically induced apoptosis of the ibrutinib-resistant MCL cells. These findings highlight and support further in vivo evaluation of the efficacy of the BA-based combinations with these agents against MCL, including ibrutinib-resistant MCL.

Long-term follow-up of MCL patients treated with single-agent ibrutinib: updated safety and efficacy results.

Ibrutinib, an oral inhibitor of Bruton tyrosine kinase, is approved for patients with mantle cell lymphoma (MCL) who have received one prior therapy. We report the updated safety and efficacy results from the multicenter, open-label phase 2 registration trial of ibrutinib (median 26.7-month follow-up). Patients (N = 111) received oral ibrutinib 560 mg once daily, and those with stable disease or better could enter a long-term extension study. The primary end point was overall response rate (ORR). The median patient age was 68 years (range, 40-84), with a median of 3 prior therapies (range, 1-5). The median treatment duration was 8.3 months; 46% of patients were treated for >12 months, and 22% were treated for ≥2 years. The ORR was 67% (23% complete response), with a median duration of response of 17.5 months. The 24-month progression-free survival and overall survival rates were 31% (95% confidence interval [CI], 22.3-40.4) and 47% (95% CI, 37.1-56.9), respectively. The most common adverse events (AEs) in >30% of patients included diarrhea (54%), fatigue (50%), nausea (33%), and dyspnea (32%). The most frequent grade ≥3 infections included pneumonia (8%), urinary tract infection (4%), and cellulitis (3%). Grade ≥3 bleeding events in ≥2% of patients were hematuria (2%) and subdural hematoma (2%). Common all-grade hematologic AEs were thrombocytopenia (22%), neutropenia (19%), and anemia (18%). The prevalence of infection, diarrhea, and bleeding was highest for the first 6 months of therapy and less thereafter. With longer follow-up, ibrutinib continues to demonstrate durable responses and favorable safety in relapsed/refractory MCL. The trial is registered to www.ClinicalTrials.gov as #NCT01236391.

Ibrutinib in combination with rituximab in relapsed or refractory mantle cell lymphoma: a single-centre, open-label, phase 2 trial.

BACKGROUND: Ibrutinib is approved in the EU, USA, and other countries for patients with mantle cell lymphoma who received one previous therapy. In a previous phase 2 study with single-agent ibrutinib, the proportion of patients who achieved an objective response was 68%; 38 (34%) of 111 patients had transient lymphocytosis. We hypothesised that adding rituximab could target mantle cell lymphoma cells associated with redistribution lymphocytosis, leading to more potent antitumour activity. METHODS: Patients with a confirmed mantle cell lymphoma diagnosis (based on CD20-positive and cyclin D1-positive cells in tissue biopsy specimens), no upper limit on the number of previous treatments received, and an Eastern Cooperative Oncology Group performance status score of 2 or less were enrolled in this single-centre, open-label, phase 2 study. Patients received continuous oral ibrutinib (560 mg) daily until progressive disease or unacceptable toxic effects. Rituximab 375 mg/m(2) was given intravenously once per week for 4 weeks during cycle 1, then on day 1 of cycles 3-8, and thereafter once every other cycle up to 2 years. The primary endpoint was the proportion of patients who achieved an objective response in the intention-to-treat population and safety assessed in the as-treated population. The study is registered with ClinicalTrials.gov, number NCT01880567, and is still ongoing, but no longer accruing patients. FINDINGS: Between July 15, 2013, and June 30, 2014, 50 patients were enrolled. Median age was 67 years (range 45-86), and the median number of previous regimens was three (range 1-9). At a median follow-up of 16·5 months (IQR 12·09-19·28), 44 (88%, 95% CI 75·7-95·5) patients achieved an objective response, with 22 (44%, 30·0-58·7) patients achieving a complete response, and 22 (44%, 30·0-58·7) a partial response. The only grade 3 adverse event in >=10% of patients was atrial fibrillation, which was noted in six (12%) patients. Grade 4 diarrhoea and neutropenia occurred in one patient each. Adverse events led to discontinuation of therapy in five (10%) patients (atrial fibrillation in three [6%] patients, liver infection in one [2%], and bleeding in one [2%]). Two patients died while on-study from cardiac arrest and septic shock; the latter was deemed possibly related to treatment. INTERPRETATION: Ibrutinib combined with rituximab is active and well tolerated in patients with relapsed or refractory mantle cell lymphoma. Our results provide preliminary evidence for the activity of this combination in clinical practice. A phase 3 trial is warranted for more definitive data. FUNDING: Pharmacyclics LLC, an AbbVie Company.