T-bet suppresses proliferation of malignant B cells in chronic lymphocytic leukemia.

The T-box transcription factor T-bet is known as a master regulator of T-cell response but its role in malignant B cells is not sufficiently explored. Here, we conducted single-cell resolved multi-omics analyses of malignant B cells from patients with chronic lymphocytic leukemia (CLL) and studied a CLL mouse model with genetic knockout of TBX21. We found that T-bet acts as a tumor suppressor in malignant B cells by decreasing their proliferation rate. NF-κB activity induced by inflammatory signals provided by the microenvironment, triggered T-bet expression which impacted on promoter proximal and distal chromatin co-accessibility and controlled a specific gene signature by mainly suppressing transcription. Gene set enrichment analysis identified a positive regulation of interferon signaling, and a negative control of proliferation by T-bet. In line, we showed that T-bet represses cell cycling and is associated with longer overall survival of CLL patients. Our study uncovers a novel tumor suppressive role of T-bet in malignant B cells via its regulation of inflammatory processes and cell cycling which has implications for stratification and therapy of CLL patients. Linking T-bet activity to inflammation explains the good prognostic role of genetic alterations in inflammatory signaling pathways in CLL.

STAT3 Activates the Pentraxin 3 Gene in Chronic Lymphocytic Leukemia Cells.

Pentraxin-related protein 3 (PTX3), commonly produced by myeloid and endothelial cells, is a humoral pattern recognition protein of the innate immune system. Because PTX3 plasma levels of patients with chronic lymphocytic leukemia (CLL) are high and most circulating cells in patients with CLL are CLL cells, we reasoned that CLL cells produce PTX3. Western immunoblotting revealed that low-density cells from seven of seven patients with CLL produce high levels of PTX3, flow cytometry analysis revealed that the PTX3-producing cells are B lymphocytes coexpressing CD19 and CD5, and confocal microscopy showed that PTX3 is present in the cytoplasm of CLL cells. Because STAT3 is constitutively activated in CLL cells, and because we identified putative STAT3 binding sites within the PTX3 gene promoter, we postulated that phosphorylated STAT3 triggers transcriptional activation of PTX3. Immunoprecipitation analysis of CLL cells' chromatin fragments showed that STAT3 Abs precipitated PTX3 DNA. STAT3 knockdown induced a marked reduction in PTX3 expression, indicating a STAT3-induced transcriptional activation of the PTX3 gene in CLL cells. Using an EMSA, we established and used a dual-reporter luciferase assay to confirm that STAT3 binds the PTX3 gene promoter. Downregulation of PTX3 enhanced apoptosis of CLL cells, suggesting that inhibition of PTX3 might benefit patients with CLL.

Chronic Lymphocytic Leukemia: Disease Biology.

BACKGROUND: B-cell receptor (BCR) signaling is crucial for normal B-cell development and adaptive immunity. In chronic lymphocytic leukemia (CLL), the malignant B cells display many features of normal mature B lymphocytes, including the expression of functional B-cell receptors (BCRs). Cross talk between CLL cells and the microenvironment in secondary lymphatic organs results in BCR signaling and BCR-driven proliferation of the CLL cells. This critical pathomechanism can be targeted by blocking BCR-related kinases (BTK, PI3K, spleen tyrosine kinase) using small-molecule inhibitors. Among these targets, Bruton tyrosine kinase (BTK) inhibitors have the highest therapeutic efficacy; they effectively block leukemia cell proliferation and generally induce durable remissions in CLL patients, even in patients with high-risk disease. By disrupting tissue homing receptor (i.e., chemokine receptor and adhesion molecule) signaling, these kinase inhibitors also mobilize CLL cells from the lymphatic tissues into the peripheral blood (PB), causing a transient redistribution lymphocytosis, thereby depriving CLL cells from nurturing factors within the tissue niches. SUMMARY: The clinical success of the BTK inhibitors in CLL underscores the central importance of the BCR in CLL pathogenesis. Here, we review CLL pathogenesis with a focus on the role of the BCR and other microenvironment cues. KEY MESSAGES: (i) CLL cells rely on signals from their microenvironment for proliferation and survival. (ii) These signals are mediated by the BCR as well as chemokine and integrin receptors and their respective ligands. (iii) Targeting the CLL/microenvironment interaction with small-molecule inhibitors provides a highly effective treatment strategy, even in high-risk patients.

Long-term outcomes in patients with chronic lymphocytic leukemia treated with ibrutinib: Focus on hypertension and cardiovascular toxicity.

BACKGROUND: Continuous ibrutinib administration is needed to maintain efficacy in patients with chronic lymphocytic leukemia (CLL) and, as such, long-term toxicity is a concern. The authors report the 5-year follow-up of patients with CLL who received treatment with ibrutinib with a focus on hypertension and cardiovascular toxicities. METHODS: Patient characteristics were assessed, including blood pressure, cardiovascular disease, disease progression, and death. Univariate logistic regression analysis assessed the relation of patient characteristics and the development of new or worsened hypertension. The incidence of hypertensive outcomes was evaluated using competing risk. Survival was estimated using the Kaplan-Meier method. RESULTS: Three hundred patients with CLL who were treated with ibrutinib on clinical trials were included. The median patient age at study enrollment was 65 years (range, 29-83 years). Seventy percent of patients were men, and 88% were Caucasian. Sixty-nine percent of patients had hypertension at baseline, and 47% were on antihypertensive medication. Eighty-eight percent had relapsed or refractory CLL. New-onset and worsening hypertension were common, occurring in 68.5% and 38% of patients, respectively. Systolic blood pressure ≥160 mm Hg or diastolic blood pressure ≥100 mm Hg was observed in 16.9% of patients. Hypertension was reversible after ibrutinib discontinuation. Older age, male sex, tobacco use, and chronic kidney disease were associated with ibrutinib-related hypertension. Baseline hypertension was not associated with major adverse cardiovascular events in ibrutinib-treated patients nor with event-free or overall survival. CONCLUSIONS: Hypertension is a common toxicity in patients with CLL who receive ibrutinib but is manageable in most patients. Other than chronic kidney disease, baseline cardiovascular disease did not affect ibrutinib-related hypertension nor was hypertension associated with major adverse cardiovascular events or survival. PLAIN LANGUAGE SUMMARY: Ibrutinib is an effective treatment for patients with chronic lymphocytic leukemia. Ibrutinib is a well tolerated therapy, however hypertension can develop or worsen in patients receiving ibrutinib and other cardiovascular events are significant challenges to the use of this drug. This may be particularly true in patients with heart disease. Short-term side effects may worsen heart disease, but the long-term impact is unknown. The long-term results of ibrutinib on heart disease and hypertension are described.

Profiling the activity of the para-caspase MALT1 in B-cell acute lymphoblastic leukemia for potential targeted therapeutic application.

B cell acute lymphoblastic leukemia (B-ALL) remains a hard-to-treat disease with a poor prognosis in adults. Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is a para-caspase required for B-cell receptor (BCR)-mediated NF-κB activation. Inhibition of MALT1 in preclinical models has proven efficacious in many B-cell malignancies including chronic lymphocytic leukemia, mantle cell lymphoma and diffuse large B-cell lymphoma. We sought to examine the role of MALT1 in B-ALL and determine the biological consequences of its inhibition. Targeting MALT1 with both Z-VRPR-fmk and MI-2 efficiently kills B-ALL cells independent of the cell-of-origin (pro, pre, mature) or the presence of the Philadelphia chromosome, and spares normal B-cells. The mechanism of cell death was through apoptotic induction, mostly in cycling cells. The proteolytic activity of MALT1 can be studied by measuring its ability to cleave its substrates. Surprisingly, with the exception of mature B-ALL, we did not detect cleavage of MALT1 substrates at baseline, nor after proteasomal inhibition or following activation of pre-BCR. To explore the possibility of a distinct role for MALT1 in B-ALL, independent of signaling through BCR, we studied the changes in gene expression profiling following a 24-hour treatment with MI-2 in 12 B-ALL cell lines. Our transcriptome analysis revealed a strong inhibitory effect on MYC-regulated gene signatures, further confirmed by Myc protein downregulation, concomitant with an increase in the Myc degrader FBXW7. In conclusion, our evidence suggests a novel role for MALT1 in B-ALL through Myc regulation and provides support for clinical testing of MALT1 inhibitors in B-ALL.

Many People With Chronic Lymphocytic Leukemia or Small Lymphocytic Lymphoma Benefit From Ibrutinib Treatment Up To 8 Years: A Plain Language Summary.

WHAT IS THIS SUMMARY ABOUT?: This is a plain language summary of a publication describing long-term results from the RESONATE-2 study with up to 8 years of follow-up. The original paper was published in Blood Advances in June 2022. WHAT WERE THE RESULTS?: Researchers looked at 269 adults with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) who had not received any treatment for their CLL/SLL. Study participants were randomly divided into two groups: 136 participants received treatment with a drug called ibrutinib, and 133 participants received treatment with a drug called chlorambucil. Participants in the study were treated and followed for up to 8 years, with results showing that more participants who took ibrutinib (59%) were alive without worsening of their disease at 7 years after starting treatment than participants who took chlorambucil (9%). Almost half of the participants (42%) were able to stay on ibrutinib treatment for up to 8 years. WHAT DO THE RESULTS OF THE STUDY MEAN?: In people with CLL or SLL, more participants who were taking ibrutinib were alive without worsening of their disease after 7 years compared with participants who took chlorambucil. Clinical Trial Registration: NCT01722487 (ClinicalTrials.gov) Clinical Trial Registration: NCT01724346 (ClinicalTrials.gov).

Prognostication of DNA Damage Response Protein Expression Patterns in Chronic Lymphocytic Leukemia.

Proteomic DNA Damage Repair (DDR) expression patterns in Chronic Lymphocytic Leukemia were characterized by quantifying and clustering 24 total and phosphorylated DDR proteins. Overall, three protein expression patterns (C1-C3) were identified and were associated as an independent predictor of distinct patient overall survival outcomes. Patients within clusters C1 and C2 had poorer survival outcomes and responses to fludarabine, cyclophosphamide, and rituxan chemotherapy compared to patients within cluster C3. However, DDR protein expression patterns were not prognostic in more modern therapies with BCL2 inhibitors or a BTK/PI3K inhibitor. Individually, nine of the DDR proteins were prognostic for predicting overall survival and/or time to first treatment. When looking for other proteins that may be associated with or influenced by DDR expression patterns, our differential expression analysis found that cell cycle and adhesion proteins were lower in clusters compared to normal CD19 controls. In addition, cluster C3 had a lower expression of MAPK proteins compared to the poor prognostic patient clusters thus implying a potential regulatory connection between adhesion, cell cycle, MAPK, and DDR signaling in CLL. Thus, assessing the proteomic expression of DNA damage proteins in CLL provided novel insights for deciphering influences on patient outcomes and expanded our understanding of the potential complexities and effects of DDR cell signaling.

Reverse Phase Protein Array Profiling Identifies Recurrent Protein Expression Patterns of DNA Damage-Related Proteins across Acute and Chronic Leukemia: Samples from Adults and the Children's Oncology Group.

DNA damage response (DNADR) recognition and repair (DDR) pathways affect carcinogenesis and therapy responsiveness in cancers, including leukemia. We measured protein expression levels of 16 DNADR and DDR proteins using the Reverse Phase Protein Array methodology in acute myeloid (AML) (n = 1310), T-cell acute lymphoblastic leukemia (T-ALL) (n = 361) and chronic lymphocytic leukemia (CLL) (n = 795) cases. Clustering analysis identified five protein expression clusters; three were unique compared to normal CD34+ cells. Individual protein expression differed by disease for 14/16 proteins, with five highest in CLL and nine in T-ALL, and by age in T-ALL and AML (six and eleven proteins, respectively), but not CLL (n = 0). Most (96%) of the CLL cases clustered in one cluster; the other 4% were characterized by higher frequencies of deletion 13q and 17p, and fared poorly (p < 0.001). T-ALL predominated in C1 and AML in C5, but both occurred in all four acute-dominated clusters. Protein clusters showed similar implications for survival and remission duration in pediatric and adult T-ALL and AML populations, with C5 doing best in all. In summary, DNADR and DDR protein expression was abnormal in leukemia and formed recurrent clusters that were shared across the leukemias with shared prognostic implications across diseases, and individual proteins showed age- and disease-related differences.

Zanubrutinib for treatment-naïve and relapsed/refractory chronic lymphocytic leukaemia: long-term follow-up of the phase I/II AU-003 study.

The phase I/II AU-003 study in patients with treatment-naïve (TN) or relapsed/refractory (R/R) chronic lymphocytic leukaemia/small lymphocytic lymphoma demonstrated that zanubrutinib therapy results in clinically meaningful and durable responses with acceptable safety and tolerability. We report updated safety and efficacy data for 123 patients with a median follow-up of 47·2 months. Patients received zanubrutinib 160 mg twice daily (81 patients), 320 mg once daily (40), or 160 mg once daily (two). Discontinuations due to adverse events or disease progression were uncommon. The overall response rate (ORR) was 95·9% (TN, 100%; R/R, 95%) with 18·7% achieving complete response (CR). Ongoing response at 3 years was reported in 85·7%. The ORR in patients with del(17p)/tumour protein p53 mutation was 87·5% (CR 16·7%). The 2- and 3-year progression-free survival estimates were 90% (TN, 90%; R/R, 91%) and 83% (TN, 81%; R/R, 83%) respectively. The most reported Grade ≥3 adverse events were neutropenia (15·4%), pneumonia (9·8%), hypertension (8·9%) and anaemia (6·5%). The annual incidence of atrial fibrillation, major haemorrhage, Grade ≥3 neutropenia and Grade ≥3 infection decreased over time. With a median follow-up of ~4 years, responses remain clinically meaningful and durable and long-term tolerability to zanubrutinib therapy continues.

Ibrutinib and Venetoclax for First-Line Treatment of CLL.

BACKGROUND: Ibrutinib, an inhibitor of Bruton's tyrosine kinase, and venetoclax, an inhibitor of B-cell lymphoma 2 protein, have been approved for patients with chronic lymphocytic leukemia (CLL). Preclinical investigations have indicated potential synergistic interaction of their combination. METHODS: We conducted an investigator-initiated phase 2 study of combined ibrutinib and venetoclax involving previously untreated high-risk and older patients with CLL. All patients had at least one of the following features: chromosome 17p deletion, mutated TP53, chromosome 11q deletion, unmutated IGHV, or an age of 65 years or older. Patients received ibrutinib monotherapy (420 mg once daily) for 3 cycles, followed by the addition of venetoclax (weekly dose escalation to 400 mg once daily). Combined therapy was administered for 24 cycles. Response assessments were performed according to International Workshop on Chronic Lymphocytic Leukemia 2008 criteria. Minimal residual disease was assessed by means of multicolor flow cytometry in bone marrow (sensitivity, 10-4). RESULTS: A total of 80 patients were treated. The median age was 65 years (range, 26 to 83). A total of 30% of the patients were 70 years of age or older. Overall, 92% of the patients had unmutated IGHV, TP53 aberration, or chromosome 11q deletion. With combined treatment, the proportions of patients who had complete remission (with or without normal blood count recovery) and remission with undetectable minimal residual disease increased over time. After 12 cycles of combined treatment, 88% of the patients had complete remission or complete remission with incomplete count recovery, and 61% had remission with undetectable minimal residual disease. Responses were noted in older adults and across all high-risk subgroups. Three patients had laboratory evidence of tumor lysis syndrome. The adverse-event profile was similar to what has been reported with ibrutinib and venetoclax. CONCLUSIONS: In this study, combined venetoclax and ibrutinib was an effective oral regimen for high-risk and older patients with CLL. (Funded by AbbVie and others; ClinicalTrials.gov number, NCT02756897.).

Kinematic Signatures of Impulsive Supernova Feedback in Dwarf Galaxies.

Impulsive supernova feedback and nonstandard dark matter models, such as self-interacting dark matter (SIDM), are the two main contenders for the role of the dominant core formation mechanism at the dwarf galaxy scale. Here we show that the impulsive supernova cycles that follow episodes of bursty star formation leave distinct features in the distribution function of stars: groups of stars with similar ages and metallicities develop overdense shells in phase space. If cores are formed through supernova feedback, we predict the presence of such features in star-forming dwarf galaxies with cored host halos. Their systematic absence would favor alternative dark matter models, such as SIDM, as the dominant core formation mechanism.

TP53-altered chronic lymphocytic leukemia treated with firstline Bruton's tyrosine kinase inhibitor-based therapy: A retrospective analysis.

Long-term follow up of prospective studies has shown that continuous Bruton's tyrosine kinase inhibitor (BTKi) therapy leads to durable remissions in previously untreated patients with TP53-altered chronic lymphocytic leukemia (CLL); however, it is unknown how variant allele frequency (VAF) of TP53 mutation (TP53-m) or percentage of cells with deletion of chromosome 17p [del(17p)] influences efficacy of firstline BTKi. We performed a retrospective analysis of 130 patients with CLL with baseline del(17p) and/or TP53-m treated with BTKi with or without the BCL2 inhibitor venetoclax (VEN) and with or without CD20 antibody in the firstline setting. A total of 104/130 (80%) patients had del(17p). TP53-m was noted in 89/110 (81%) patients tested; there were 101 unique TP53-m with an available VAF. The 4-year progression-free survival (PFS) and overall survival (OS) rates were 72.9% and 83.6%. No baseline characteristics including IGHV mutation status and number of TP53 alterations were associated with significant differences in PFS or OS, though a trend toward shorter PFS with increasing karyotypic complexity (hazard ratio 1.08, p = .066) was observed. Del(17p) was identified in <25% of cells in 26/104 (25%) of patients, and 28/101 (28%) of TP53-m were low-burden with a VAF of <10%; outcomes of these patients were similar to those with high-burden lesions. This study suggests that low-burden TP53 alterations should not be ignored when assessing genomic risk in CLL in the era of targeted therapy.

Long-term follow-up of salvage therapy using a combination of inotuzumab ozogamicin and mini-hyper-CVD with or without blinatumomab in relapsed/refractory Philadelphia chromosome-negative acute lymphoblastic leukemia.

BACKGROUND: The outcome of patients with relapsed/refractory (R/R) acute lymphoblastic leukemia (ALL) is poor. The combination of inotuzumab with low-intensity mini-hyper-CVD (mini-hyper-CVD; cyclophosphamide and dexamethasone at 50% dose reduction, no anthracycline, methotrexate at 75% dose reduction, cytarabine at 0.5 g/m2 × 4 doses) chemotherapy has shown encouraging results. The sequential addition of blinatumomab might improve outcome in patients with R/R ALL. METHODS: We used lower intensity chemotherapy, mini-hyper-CVD (cyclophosphamide and dexamethasone at 50% dose reduction, no anthracycline, methotrexate at 75% dose reduction, cytarabine at 0.5 g/m2 x 4 doses) compared to conventional hyper-CVAD. RESULTS: Ninety-six patients with a median age of 37 years (range, 18-87 years) were treated. Overall, 77 patients (80%) responded, 55 (57%) of whom achieved complete response. The overall measurable residual disease negativity rate among responders was 83%. Forty-four (46%) patients underwent later allogeneic stem cell transplantation. Veno-occlusive disease of any grade occurred in 10 (10%) patients. The rates were 13% with the original schedule and 3% with the use of lower-dose inotuzumab and sequential blinatumomab. With a median follow-up of 36 months, the median overall survival (OS) was 13.4 months, with 3-year OS rates of 33%. The 3-year OS rate for patients with CD22 expression ≥70% and without adverse cytogenetics (KMT2A rearrangements, low hypodiploidy/near triploidy) was 55%. CONCLUSION: The combination of inotuzumab and low-intensity mini-hyper-CVD chemotherapy with or without blinatumomab shows sustained efficacy in patients with R/R ALL.

Clinical and molecular characteristics and treatment patterns of adolescent and young adult patients with chronic lymphocytic leukaemia.

Chronic lymphocytic leukaemia (CLL) rarely presents in adolescent and young adult (AYA) patients (patients aged 15-39 years). Disease characteristics and outcomes of AYA patients with CLL are not well understood, particularly in the era of novel oral targeted therapies. We analysed outcomes of 227 AYA patients with CLL diagnosed in the last two decades and evaluated at our institution. Median time to first treatment (TTFT) was 2·2 years, and five- and 10-year overall survival (OS) were 90% and 78%, respectively. Pre-treatment elevated beta 2-microglobulin, advanced Rai stage, del(11q) or del(17p) by FISH, unmutated IGHV and CD38 positivity were associated with both shorter TTFT and OS. Within the subgroup of patients who received oral targeted therapy at any time, del(11q) or del(17p) and complex karyotype were associated with shorter OS. First-line treatment choice was significantly associated with time to second treatment (P < 0·001). Patients harbouring del(11q) or del(17p) experienced shorter time to Richter transformation and were more likely to undergo an allogeneic stem cell transplant. There was a significant association between age and both OS and time to Richter transformation. Our study is the first analysis of AYA patients with CLL with a large number of patients treated with oral targeted therapies.

Ibrutinib therapy downregulates AID enzyme and proliferative fractions in chronic lymphocytic leukemia.

Activation-induced cytidine deaminase (AID) initiates somatic hypermutation and class switch recombination of the immunoglobulin genes. As a trade-off for its physiological function, AID also contributes to tumor development through its mutagenic activity. In chronic lymphocytic leukemia (CLL), AID is overexpressed in the proliferative fractions (PFs) of the malignant B lymphocytes, and its anomalous expression has been associated with a clinical poor outcome. Recent preclinical data suggested that ibrutinib and idelalisib, 2 clinically approved kinase inhibitors, increase AID expression and genomic instability in normal and neoplastic B cells. These results raise concerns about a potential mutagenic risk in patients receiving long-term therapy. To corroborate these findings in the clinical setting, we analyzed AID expression and PFs in a CLL cohort before and during ibrutinib treatment. We found that ibrutinib decreases the CLL PFs and, interestingly, also reduces AID expression, which correlates with dampened AKT and Janus Kinase 1 signaling. Moreover, although ibrutinib increases AID expression in a CLL cell line, it is unable to do so in primary CLL samples. Our results uncover a differential response to ibrutinib between cell lines and the CLL clone and imply that ibrutinib could differ from idelalisib in their potential to induce AID in treated patients. Possible reasons for the discrepancy between preclinical and clinical findings, and their effect on treatment safety, are discussed.

Minimal residual disease undetectable by next-generation sequencing predicts improved outcome in CLL after chemoimmunotherapy.

Patients with chronic lymphocytic leukemia (CLL) who achieve blood or bone marrow (BM) undetectable minimal residual disease (U-MRD) status after first-line fludarabine, cyclophosphamide, and rituximab (FCR) have prolonged progression-free survival (PFS), when assessed by an assay with sensitivity 10-4 (MRD4). Despite reaching U-MRD4, many patients, especially those with unmutated IGHV, subsequently relapse, suggesting residual disease <10-4 threshold and the need for more sensitive MRD evaluation. MRD evaluation by next-generation sequencing (NGS) has a sensitivity of 10-6 (MRD6). To better assess the depth of remission following first-line FCR treatment, we used NGS (Adaptive Biotechnologies Corporation) to assess MRD in 62 patients, all of whom had BM U-MRD by multicolor flow cytometry (sensitivity 10-4) at end-of-FCR treatment. Samples from these patients included 57 BM samples, 29 peripheral blood mononuclear cell (PBMC) samples, and 32 plasma samples. Only 27.4% of the 62 patients had U-MRD by NGS. Rate of U-MRD by NGS was lowest in BM (25%), compared with PBMC (55%) or plasma (75%). No patient with U-MRD by NGS in BM or PBMC was MRD+ in plasma. Patients with mutated IGHV were more likely to have U-MRD by NGS at the end of treatment (EOT; 41% vs 13%, P = .02) than those with unmutated IGHV. Median follow-up was 81.6 months. Patients with U-MRD at EOT had superior PFS vs MRD+ patients, regardless of sample type assessed (BM, P = .02, median not reached [NR] vs 67 months; PBMC, P = .02, median NR vs 74 months). More sensitive MRD6 testing increases prognostic discrimination over MRD4 testing.

Ublituximab and umbralisib in relapsed/refractory B-cell non-Hodgkin lymphoma and chronic lymphocytic leukemia.

Targeting both CD20 and phosphatidylinositol 3-kinase (PI3K), a protein that is critically involved in B-cell maturation, could be an efficacious strategy for treating B-cell malignancies. The safety of the next-generation compounds umbralisib, a PI3K-δ inhibitor, plus ublituximab, an anti-CD20 monoclonal antibody (combination referred to as U2), was evaluated in patients with chronic lymphocytic lymphoma (CLL) or non-Hodgkin lymphoma (NHL) in this phase 1/1b study. Phase 1 dose escalation was performed with a 3 + 3 design to establish the maximum tolerated dose. In this portion, ublituximab was given intravenously (NHL, 900 mg; CLL, 600 or 900 mg) for 12 cycles. Umbralisib was given orally once daily at 800 or 1200 mg (initial formulation) or 400 to 1200 mg (micronized formulation) in the phase 1 dose escalation portion, and at 800 to 1200 mg in the phase 1b portion until progression, toxicity, or study removal. The maximum tolerated dose was not reached in either the CLL or NHL cohort, and only 1 dose-limiting toxicity was observed. U2 had low instances of grade 3 or higher diarrhea (8%), pneumonia (8%), or hepatic toxicity (4%). Treatment discontinuation due to adverse events occurred in 13% of patients, and umbralisib dose reductions occurred in 15% of patients. The overall response rate for all patients was 46% with 17% complete responses. The median duration of response was 20 months (95% confidence interval, 11.3-not reached). U2 was well tolerated, and no new safety signals were observed over single-agent umbralisib. Preliminary efficacy with this combination is promising and warrants further investigation. This study was registered at www.clinicaltrials.gov as #NCT02006485.

Randomized trial of ibrutinib vs ibrutinib plus rituximab in patients with chronic lymphocytic leukemia.

Ibrutinib, an oral covalent inhibitor of Bruton's tyrosine kinase, is an effective therapy for patients with chronic lymphocytic leukemia (CLL). To determine whether rituximab provides added benefit to ibrutinib, we conducted a randomized single-center trial of ibrutinib vs ibrutinib plus rituximab. Patients with CLL requiring therapy were randomized to receive 28-day cycles of once-daily ibrutinib 420 mg, either as a single agent (n = 104), or together with rituximab (375 mg/m2; n = 104), given weekly during cycle 1, then once per cycle until cycle 6. The primary end point was progression-free survival (PFS) in the intention-to-treat population. We enrolled 208 patients with CLL, 181 with relapsed CLL and 27 treatment-naive patients with high-risk disease (17p deletion or TP53 mutation). After a median follow-up of 36 months, the Kaplan-Meier estimates of PFS were 86% (95% confidence interval [CI], 76.6-91.9) for patients receiving ibrutinib, and 86.9% (95% CI, 77.3-92.6) for patients receiving ibrutinib plus rituximab. Similarly, response rates were the same in both arms (overall response rate, 92%). However, time to normalization of peripheral blood lymphocyte counts and time to complete remission were shorter, and residual disease levels in the bone marrow were lower, in patients receiving ibrutinib plus rituximab. We conclude that the addition of rituximab to ibrutinib in relapsed and treatment-naive high-risk patients with CLL failed to show improvement in PFS. However, patients treated with ibrutinib plus rituximab reached their remissions faster and achieved significantly lower residual disease levels. Given these results, ibrutinib as single-agent therapy remains current standard-of-care treatment in CLL. This trial was registered at www.clinicaltrials.gov as #NCT02007044.

Phase 1 study of the selective BTK inhibitor zanubrutinib in B-cell malignancies and safety and efficacy evaluation in CLL.

Zanubrutinib is a potent and highly selective inhibitor of Bruton tyrosine kinase (BTK). In this first-in-human, open-label, multicenter, phase 1 study, patients in part 1 (3 + 3 dose escalation) had relapsed/refractory B-cell malignancies and received zanubrutinib 40, 80, 160, or 320 mg once daily or 160 mg twice daily. Part 2 (expansion) consisted of disease-specific cohorts, including treatment-naive or relapsed/refractory chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). The primary end points were safety and tolerability, and definition of the maximum tolerated dose (part 1). Additional end points included pharmacokinetics/pharmacodynamics and preliminary efficacy. Reported herein are results from 144 patients enrolled in the dose-finding and CLL/SLL cohorts. No dose-limiting toxicities occurred in dose escalation. Median BTK occupancy in peripheral blood mononuclear cells was >95% at all doses. Sustained complete (>95%) BTK occupancy in lymph node biopsy specimens was more frequent with 160 mg twice daily than 320 mg once daily (89% vs 50%; P = .0342). Consequently, 160 mg twice daily was selected for further investigation. With median follow-up of 13.7 months (range, 0.4-30.5 months), 89 CLL/SLL patients (94.7%) remain on study. Most toxicities were grade 1/2; neutropenia was the only grade 3/4 toxicity observed in >2 patients. One patient experienced a grade 3 subcutaneous hemorrhage. Among 78 efficacy-evaluable CLL/SLL patients, the overall response rate was 96.2% (95% confidence interval, 89.2-99.2). Estimated progression-free survival at 12 months was 100%. Zanubrutinib demonstrated encouraging activity in CLL/SLL patients, with a low incidence of major toxicities. This trial was registered at www.clinicaltrials.gov as #NCT02343120.

Long-term follow-up of the RESONATE phase 3 trial of ibrutinib vs ofatumumab.

Ibrutinib, a once-daily oral inhibitor of Bruton tyrosine kinase, has greatly improved outcomes for patients with chronic lymphocytic leukemia (CLL). The phase 3 RESONATE trial, which compared single-agent ibrutinib to ofatumumab in high-risk, relapsed patients with CLL, provided support for approval of ibrutinib in the United States and Europe. We describe long-term follow-up of patients treated in RESONATE, where continued superiority of progression-free survival (PFS) (hazard ratio [HR], 0.133; 95% confidence interval [CI], 0.099-0.178) was observed. Overall survival benefit continues (HR, 0.591; 95% CI, 0.378-0.926), although with decreased magnitude relative to that seen before crossover to ibrutinib was implemented for patients on ofatumumab (HR, 0.426; 95% CI, 0.220-0.823). Notably, overall response to ibrutinib increased over time, with 91% of patients attaining a response. The PFS benefit with ibrutinib was independent of baseline risk factors, although patients with ≥2 prior therapies had shorter PFS than those with <2 prior therapies, and the presence of TP53 or SF3B1 mutations showed a trend toward shorter PFS vs without these factors. Median duration of ibrutinib was 41 months, with 46% remaining on treatment at a median follow-up of 44 months. Grade ≥3 adverse events generally decreased over time, causing only a small proportion of patients to cease therapy. Ibrutinib was discontinued due to progressive disease in 27% of patients. This long-term study provides support for sustained efficacy and safety of ibrutinib in relapsed/refractory CLL and consideration of study provisions that allow crossover to investigational therapy when benefit has been clearly demonstrated. This trial was registered at www.clinicaltrials.gov as #NCT01578707.