Apoptosis, the process of programmed cell death, occurs normally during development and aging. Members of the B-cell lymphoma 2 (BCL2) family of proteins are central regulators of apoptosis, and ...resistance to apoptosis is one of the hallmarks of cancer. Targeting the apoptotic pathway via BCL2 inhibitors has been considered a promising treatment strategy in the past decade. Initial efforts with small molecule BH3 mimetics such as ABT-737 and ABT-263 (navitoclax) pioneered the development of the first-in-class Food and Drug Administration (FDA)-approved oral BCL2 inhibitor, venetoclax. Venetoclax was approved for the treatment of chronic lymphocytic leukemia and acute myeloid leukemia, and is now being studied in a number of hematologic malignancies. Several other inhibitors targeting different BCL2 family members are now in early stages of development.
Bruton tyrosine kinase inhibitors (BTKi) and venetoclax are currently used to treat newly diagnosed and relapsed/refractory chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). ...However, most patients eventually develop resistance to these therapies, underscoring the need for effective new therapies. We report results of the phase 1 dose-escalation portion of the multicenter, open-label, phase 1/2 TRANSCEND CLL 004 (NCT03331198) study of lisocabtagene maraleucel (liso-cel), an autologous CD19-directed chimeric antigen receptor (CAR) T-cell therapy, in patients with relapsed/refractory CLL/SLL. Patients with standard- or high-risk features treated with ≥3 or ≥2 prior therapies, respectively, including a BTKi, received liso-cel at 1 of 2 dose levels (50 × 106 or 100 × 106 CAR+ T cells). Primary objectives included safety and determining recommended dose; antitumor activity by 2018 International Workshop on CLL guidelines was exploratory. Minimal residual disease (MRD) was assessed in blood and marrow. Twenty-three of 25 enrolled patients received liso-cel and were evaluable for safety. Patients had a median of 4 (range, 2-11) prior therapies (100% had ibrutinib; 65% had venetoclax) and 83% had high-risk features including mutated TP53 and del(17p). Seventy-four percent of patients had cytokine release syndrome (9% grade 3) and 39% had neurological events (22% grade 3/4). Of 22 efficacy-evaluable patients, 82% and 45% achieved overall and complete responses, respectively. Of 20 MRD-evaluable patients, 75% and 65% achieved undetectable MRD in blood and marrow, respectively. Safety and efficacy were similar between dose levels. The phase 2 portion of the study is ongoing at 100 × 106 CAR+ T cells. This trial was registered at clinicaltrials.gov as NCT03331198.
•Liso-cel was associated with manageable toxicities and rapid and deep responses in patients with relapsed/refractory CLL/SLL.•With successful manufacturing of liso-cel for patients with CLL/SLL and the encouraging phase 1 results, a phase 2 study is underway.
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Pim kinases are involved in B-cell development and are overexpressed in B-cell chronic lymphocytic leukemia (CLL). We hypothesized that Pim kinase inhibition would affect B-cell survival. Identified ...from a screen of imidazo1,2-bpyridazine compounds, SGI-1776 inhibits Pim-1, Pim-2, and Pim-3. Treatment of CLL cells with SGI-1776 results in a concentration-dependent induction of apoptosis. To elucidate its mechanism of action, we evaluated the effect of SGI-1776 on Pim kinase function. Unlike in replicating cells, phosphorylation of traditional Pim-1 kinase targets, phospho-Bad (Ser112) and histone H3 (Ser10), and cell-cycle proteins were unaffected by SGI-1776, suggesting an alternative mechanism in CLL. Protein levels of total c-Myc as well as phospho-c-Myc(Ser62), a Pim-1 target site, were decreased after SGI-1776 treatment. Levels of antiapoptotic proteins Bcl-2, Bcl-XL, XIAP, and proapoptotic Bak and Bax were unchanged; however, a significant reduction in Mcl-1 was observed that was not caused by caspase-mediated cleavage of Mcl-1 protein. The mechanism of decline in Mcl-1 was at the RNA level and was correlated with inhibition of global RNA synthesis. Consistent with a decline in new RNA synthesis, MCL-1 transcript levels were decreased after treatment with SGI-1776. These data suggest that SGI-1776 induces apoptosis in CLL and that the mechanism involves Mcl-1 reduction.
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.
•Most patients with U-MRD by flow cytometry (sensitivity 10−4) after first-line FCR for CLL are MRD+ by NGS (sensitivity 10−6).•Patients with undetectable MRD by NGS have superior PFS.
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Ibrutinib inhibits Bruton tyrosine kinase (BTK) by irreversibly binding to the Cys-481 residue in the enzyme. However, ibrutinib also inhibits several other enzymes that contain cysteine residues ...homologous to Cys-481 in BTK. Patients with relapsed/refractory or previously untreated chronic lymphocytic leukemia (CLL) demonstrate a high overall response rate to ibrutinib with prolonged survival. Acalabrutinib, a selective BTK inhibitor developed to minimize off-target activity, has shown promising overall response rates in patients with relapsed/refractory CLL. A head-to-head comparison of ibrutinib and acalabrutinib in CLL cell cultures and healthy T cells is needed to understand preclinical biologic and molecular effects.
Using samples from patients with CLL, we compared the effects of both BTK inhibitors on biologic activity, chemokine production, cell migration, BTK phosphorylation, and downstream signaling in primary CLL lymphocytes and on normal T-cell signaling to determine the effects on other kinases.
Both BTK inhibitors induced modest cell death accompanied by cleavage of PARP and caspase-3. Production of CCL3 and CCL4 chemokines and pseudoemperipolesis were inhibited by both drugs to a similar degree. These drugs also showed similar inhibitory effects on the phosphorylation of BTK and downstream S6 and ERK kinases. In contrast, off-target effects on SRC-family kinases were more pronounced with ibrutinib than acalabrutinib in healthy T lymphocytes.
Both BTK inhibitors show similar biological and molecular profile in primary CLL cells but appear different on their effect on normal T cells.
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Lenalidomide is an immunomodulatory drug active as salvage therapy for chronic lymphocytic leukemia (CLL). We combined lenalidomide with rituximab to improve response rates in patients with relapsed ...or refractory CLL.
Fifty-nine adult patients (age 42 to 82 years) with relapsed or refractory CLL were enrolled onto a phase II study of lenalidomide and rituximab. Patients had received prior fludarabine-based therapy or chemoimmunotherapy. Rituximab (375 mg/m(2) intravenously) was administered weekly during cycle one and on day 1 of cycles three to 12. Lenalidomide was started on day 9 of cycle one at 10 mg orally and administered daily continuously. Each cycle was 28 days. Rituximab was administered for 12 cycles; lenalidomide could continue indefinitely if patients benefitted clinically.
The overall response rate was 66%, including 12% complete responses and 12% nodular partial remissions. Time to treatment failure was 17.4 months. Median overall survival has not been reached; estimated survival at 36 months is 71%. The most common grade 3 or 4 toxicity was neutropenia (73% of patients). Fourteen patients (24%) experienced a grade 3 to 4 infection or febrile episode. There was one episode of grade 3 tumor lysis; one patient experienced renal failure during the first cycle of therapy, and one venous thromboembolic event occurred during the study.
The combination of lenalidomide and rituximab is active in patients with recurrent CLL and warrants further investigation.
The treatment of relapsed chronic lymphocytic leukemia (CLL) has resulted in few durable remissions. Bruton's tyrosine kinase (BTK), an essential component of B-cell-receptor signaling, mediates ...interactions with the tumor microenvironment and promotes the survival and proliferation of CLL cells.
We conducted a phase 1b-2 multicenter study to assess the safety, efficacy, pharmacokinetics, and pharmacodynamics of ibrutinib (PCI-32765), a first-in-class, oral covalent inhibitor of BTK designed for treatment of B-cell cancers, in patients with relapsed or refractory CLL or small lymphocytic lymphoma. A total of 85 patients, the majority of whom were considered to have high-risk disease, received ibrutinib orally once daily; 51 received 420 mg, and 34 received 840 mg.
Toxic effects were predominantly grade 1 or 2 and included transient diarrhea, fatigue, and upper respiratory tract infection; thus, patients could receive extended treatment with minimal hematologic toxic effects. The overall response rate was the same in the group that received 420 mg and the group that received 840 mg (71%), and an additional 20% and 15% of patients in the respective groups had a partial response with lymphocytosis. The response was independent of clinical and genomic risk factors present before treatment, including advanced-stage disease, the number of previous therapies, and the 17p13.1 deletion. At 26 months, the estimated progression-free survival rate was 75% and the rate of overall survival was 83%.
Ibrutinib was associated with a high frequency of durable remissions in patients with relapsed or refractory CLL and small lymphocytic lymphoma, including patients with high-risk genetic lesions. (Funded by Pharmacyclics and others; ClinicalTrials.gov number, NCT01105247.).
CLL cell trafficking between blood and tissue compartments is an integral part of the disease process. Idelalisib, a phosphoinositide 3-kinase delta (PI3Kδ) inhibitor causes rapid lymph node ...shrinkage, along with an increase in lymphocytosis, prior to inducing objective responses in CLL patients. This characteristic activity presumably is due to CLL cell redistribution from tissues into the blood, but the underlying mechanisms are not fully understood. We therefore analyzed idelalisib effects on CLL cell adhesion to endothelial and bone marrow stromal cells (EC, BMSC). We found that idelalisib inhibited CLL cell adhesion to EC and BMSC under static and shear flow conditions. TNFα-induced VCAM-1 (CD106) expression in supporting layers increased CLL cell adhesion and accentuated the inhibitory effect of idelalisib. Co-culture with EC and BMSC also protected CLL from undergoing apoptosis, and this EC- and BMSC-mediated protection was antagonized by idelalisib. Furthermore, we demonstrate that CLL cell adhesion to EC and VLA-4 (CD49d) resulted in the phosphorylation of Akt, which was sensitive to inhibition by idelalisib. These findings demonstrate that idelalisib interferes with integrin-mediated CLL cell adhesion to EC and BMSC, providing a novel mechanism to explain idelalisib-induced redistribution of CLL cells from tissues into the blood.
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