Simultaneous Inhibition of BCL-2 and PI3K Signaling Overcomes Ibrutinib Resistance in Mantle Cell Lymphoma

Abstract Background: Mantle cell lymphoma (MCL) is an aggressive B-cell malignancy that is initially responsive but ultimately relapses to frontline therapy. Ibrutinib, a first-in-class, once-daily, oral covalent inhibitor of Bruton's tyrosine kinase (BTK) has achieved a 68% overall response rate in relapsed/refractory MCL patients (Wang et al., NEJM, 2013). However, the vast majority of MCL patients experience disease progression; therefore, novel therapies to overcome ibrutinib resistance are urgently needed. Ibrutinib resistance is associated with the dysregulation of alternative signaling pathways such as the apoptotic pathway and PI3K/AKT signaling; therefore, combinatorial therapeutic strategies may prove fruitful in overcoming ibrutinib resistance via the blockade of these compensatory pathways. Based on the upregulation of the PI3K signaling pathway and the anti-apoptotic pathway in ibrutinib resistance, we co-inhibited both pathways with the dual PI3K-delta and -gamma inhibitor duvelisib and the BCL-2 inhibitor venetoclax to assess the ability of this combination to overcome ibrutinib resistance in MCL. Methods: Cell viability and apoptosis assays were conducted to assess the effects of venetoclax and duvelisib on 4 ibrutinib-resistant cell lines (Jeko BTK KD, Jeko-R, Z-138 and Maver-1) and 4 primary patient samples. We also confirmed the synergistic effect of this combination on two ibrutinib-resistant cell lines (Jeko BTK KD and Z-138) by western blotting. Aberrant protein expression between single agents and drug combination in Jeko BTK KD cells was detected using Reverse Phase Protein Array (RPPA) analysis with confirmation by western blotting. Cell migration of Jeko BTK KD cells was assessed. A Jeko-1 cell xenograft (which is resistant to ibrutinib in vivo) was established in NSG mice, and drug testing was performed in this model with tumor burden assessed viain vivo imaging. Results: We observed synergistic activity with the combination of venetoclax and duvelisib in 4 ibrutinib-resistant cell lines (Jeko BTK KD, 0.36; Jeko-R, 0.47; Z-138, 0.66; Maver-1, 0.41) and in 4 ibrutinib-resistant patient samples (PT1, 0.14; PT2, 0.43; PT3, 0.52; PT4, 0.41) by calculating the synergistic index (Ki value). We confirmed the synergistic effects of this combination by observing apoptosis at 72 hours post-treatment in Jeko BTK KD and Z-138 cells. Moreover, the combination of venetoclax and duvelisib synergistically reduced the cell migration of Jeko BTK KD cells. RPPA analysis of Z-138 MCL cells post-treatment demonstrated that multiple pathways, including the apoptotic pathway as well as the PI3K/AKT and BCR signaling pathways, were synergistically altered by venetoclax and duvelisib. Moreover, venetoclax and duvelisb synergistically reduced tumor burden in a Jeko-1 cell xenograft model resistant to ibrutinib. Conclusion: PI3K signaling and BCL-2-related pathways are activated in ibrutinib-resistant MCL cells, and targeting these pathways using a combinatorial approach may potentially overcome ibrutinib resistance. Disclosures Wang: AstraZeneca: Consultancy, Research Funding; Pharmacyclics: Honoraria, Research Funding; Novartis: Research Funding; MoreHealth: Consultancy; Juno: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta Pharma: Honoraria, Research Funding; Kite Pharma: Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Dava Oncology: Honoraria.

Download Full-text

Characterization of Mechanisms Underlying Acquired Venetoclax-Resistance in Mantle Cell Lymphoma: BDA-366 As a Potential Treatment Option

Blood ◽

10.1182/blood-2018-99-115845 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 1580-1580

Author(s):

Daniela Steinbrecher ◽

Felix Seyfried ◽

Johannes Bloehdorn ◽

Billy Michael Chelliah Jebaraj ◽

Lüder Hinrich Meyer ◽

...

Keyword(s):

Cell Death ◽

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Cell Lymphoma ◽

Resistant Cell ◽

Advisory Committees ◽

Apoptotic Protein ◽

Mantle Cell ◽

Resistant Cells

Abstract In many cancers the equilibrium of pro- versus anti-apoptotic BCL-2 proteins is deregulated. BCL-2 inhibitors like Venetoclax (VEN) have been shown to be highly active drugs in BCL-2 dependent cancers like chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL). Despite being highly efficient in cell killing, resistance to VEN can be acquired over time. In addition to understanding the underlying mechanisms of resistance to VEN it is important to identify additional treatment options. BDA-366 is a BCL-2 inhibitor with a different mode of action than the BH3 mimetic VEN. BDA-366 acts by inhibiting the BH4 domain and thereby inducing a conversion of anti-apoptotic BCL-2 into a pro-apoptotic protein. BDA-366 showed high effectivity in inducing apoptosis in CLL cells, in primary as well as in cell lines, while all of the CLL cell lines (n=7) tested were resistant to VEN. Furthermore all of the MCL cell lines (n=5) tested were sensitive to the treatment with BDA-366 while only a subset (3 out of 5) responded to treatment with VEN. In order to investigate whether BDA-366 would be a treatment option for VEN-resistant patients, we generated VEN-resistant MCL cell lines (MINO and MAVER-1) by chronic exposure to the drug. In the resistant cell lines, BCL-2 protein levels were not deregulated. In variance to previous reports in diffuse large B cell lymphoma (DLBCL) (Choudhary et al, Cell Death Dis 2015), resistance in MCL cell lines was not mediated by MCL-1 upregulation. In VEN-resistant MINO cells, MCL-1 expression was similar to the parental cells, while MCL-1 was significantly downregulated in VEN-resistant MAVER-1 cells. In contrast, VEN-resistant MCL cell lines showed BCL-XL upregulation as compared to parental cells, which is in line with results obtained in DLBCL (Choudhary et al, Cell Death Dis 2015). Furthermore, dynamic BH3 profiling validated a dependency on BCL-XL in resistant cells and confirmed that resistance was not mediated by MCL-1. The significance of BCL-XL in mediating resistance to VEN was underlined by additional experiments using navitoclax. In contrast to VEN, navitoclax inhibits BCL-2, BCL-XL and BCL-W and was sufficient to induce apoptosis in both parental and resistant cells. In contrast to the BH3 domain inhibitor VEN, the BCL-2 inhibitor BDA-366 acts by converting BCL-2 into a pro-apoptotic molecule. BDA-366 efficiently induced dose dependent apoptosis in VEN-resistant cells. MINO as well as MINO VEN-resistant cells showed the same sensitivity to BDA-366 while VEN-resistant MAVER-1 cells showed reduced sensitivity to BDA-366 as compared to the parental cells. However, with increased BDA-366 concentrations efficient cell killing was achieved in the VEN-resistant cell lines Overall, these results suggest that VEN-resistance is mostly mediated by permanent upregulation of BCL-XL. BCL-2 levels are not deregulated upon development of resistance to VEN. The inhibition of the BH4 domain and thereby converting BCL-2 into a pro-apoptotic protein proved to be a promising therapeutic option even in cancers with acquired resistance to VEN. Disclosures Döhner: Pfizer: Research Funding; Amgen: Consultancy, Honoraria; Jazz: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Sunesis: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria; Sunesis: Consultancy, Honoraria, Research Funding; Agios: Consultancy, Honoraria; Pfizer: Research Funding; AROG Pharmaceuticals: Research Funding; Bristol Myers Squibb: Research Funding; Astex Pharmaceuticals: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; AROG Pharmaceuticals: Research Funding; Astellas: Consultancy, Honoraria; Astellas: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Astex Pharmaceuticals: Consultancy, Honoraria; Celator: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Celator: Consultancy, Honoraria; Jazz: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Bristol Myers Squibb: Research Funding; Janssen: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding. Stilgenbauer:Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Boehringer-Ingelheim: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Hoffmann La-Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genzyme: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Mundipharma: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmcyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Download Full-text

Activation of MYC, a bona fide client of HSP90, contributes to intrinsic ibrutinib resistance in mantle cell lymphoma

Blood Advances ◽

10.1182/bloodadvances.2018016048 ◽

2018 ◽

Vol 2 (16) ◽

pp. 2039-2051 ◽

Cited By ~ 16

Author(s):

Jimmy Lee ◽

Liang Leo Zhang ◽

Wenjun Wu ◽

Hui Guo ◽

Yan Li ◽

...

Keyword(s):

Mantle Cell Lymphoma ◽

Cell Lines ◽

Cell Lymphoma ◽

Resistant Cell ◽

Intrinsic Resistance ◽

Mantle Cell ◽

Myc Gene ◽

Bona Fide ◽

Ibrutinib Resistance ◽

Induced Apoptosis

Abstract The BTK inhibitor ibrutinib has demonstrated a remarkable therapeutic effect in mantle cell lymphoma (MCL). However, approximately one-third of patients do not respond to the drug initially. To identify the mechanisms underlying primary ibrutinib resistance in MCL, we analyzed the transcriptome changes in ibrutinib-sensitive and ibrutinib-resistant cell lines on ibrutinib treatment. We found that MYC gene signature was suppressed by ibrutinib in sensitive but not resistant cell lines. We demonstrated that MYC gene was structurally abnormal and MYC protein was overexpressed in MCL cells. Further, MYC knockdown with RNA interference inhibited cell growth in ibrutinib-sensitive as well as ibrutinib-resistant cells. We explored the possibility of inhibiting MYC through HSP90 inhibition. The chaperon protein is overexpressed in both cell lines and primary MCL cells from the patients. We demonstrated that MYC is a bona fide client of HSP90 in the context of MCL by both immunoprecipitation and chemical precipitation. Furthermore, inhibition of HSP90 using PU-H71 induced apoptosis and caused cell cycle arrest. PU-H71 also demonstrates strong and relatively specific inhibition of the MYC transcriptional program compared with other oncogenic pathways. In a MCL patient-derived xenograft model, the HSP90 inhibitor retards tumor growth and prolongs survival. Last, we showed that PU-H71 induced apoptosis and downregulated MYC protein in MCL cells derived from patients who were clinically resistant to ibrutinib. In conclusion, MYC activity underlies intrinsic resistance to ibrutinib in MCL. As a client protein of HSP90, MYC can be inhibited via PU-H71 to overcome primary ibrutinib resistance.

Download Full-text

Phase II Randomized, Multicenter Study of Lenalidomide Vs Best Investigator’s Choice in Relapsed/Refractory Mantle Cell Lymphoma: Results of the MCL-002 (SPRINT) Study

Blood ◽

10.1182/blood.v124.21.626.626 ◽

2014 ◽

Vol 124 (21) ◽

pp. 626-626 ◽

Cited By ~ 6

Author(s):

Marek Trneny ◽

Thierry Lamy ◽

Jan Walewski ◽

Wojciech Jurczak ◽

David Belada ◽

...

Keyword(s):

Board Of Directors ◽

Phase Ii ◽

Research Funding ◽

Cell Lymphoma ◽

Tumor Burden ◽

Advisory Committees ◽

First Response ◽

Mantle Cell ◽

Grade 3 ◽

Prognostic Profile

Abstract Introduction: Mantle cell lymphoma (MCL) is an aggressive non-Hodgkin’s lymphoma with poor outcome, especially after failure of first-line treatment. Lenalidomide, an immunomodulatory drug with antineoplastic and antiproliferative effects, has shown activity in single-arm phase II studies of patients with relapsed/refractory (R/R) MCL. The present controlled randomized study compared the efficacy and safety of lenalidomide vs investigator’s choice (IC) in patients with R/R MCL. Methods: MCL-002 (SPRINT), a European multicenter, open-label, phase II study enrolled patients with up to 3 relapses or who failed prior therapy and were ineligible for intensified treatment or stem cell transplantation (NCT00875667). Oral lenalidomide was given at 25 mg/day on days 1-21 of each 28-day cycle until progressive disease (PD) or intolerability. The IC treatment consisted of single-agent therapy with cytarabine, rituximab, gemcitabine, fludarabine, or chlorambucil. Patients who progressed on IC per investigator judgment were allowed to crossover to lenalidomide. The primary endpoint was progression-free survival (PFS); secondary endpoints included overall response rate (ORR), time to first response, duration of response (DOR), overall survival (OS), and safety. Response assessments were centrally reviewed using the modified IWG criteria. Results: 254 patients with R/R MCL were randomized 2:1 to lenalidomide (n=170) or IC (n=84). Patients had median age 68.5 years, were predominantly male (73%), and had received a median of 2 prior therapies. 91% had stage III/IV disease at diagnosis, with 34% high-risk MIPI, 43% high tumor burden, and 20% bulky disease at baseline. Overall, patients on the lenalidomide arm had a worse prognostic profile than the IC arm due to higher tumor burden and disease risk (>5 percentage points for a number of parameters). After a median time of 2.9 months, 39 patients (46%) from the IC arm crossed over to lenalidomide due to PD. Overall, 84 patients remain on lenalidomide (15 having crossed over from IC) and 11 patients on IC without PD. At a median follow-up time on study of 15.9 months, the risk reduction for PFS was 39% (HR=0.61 [95% CI, 0.44-0.84]; P=0.004; Table) in favor of lenalidomide (median PFS: 8.7 months lenalidomide vs 5.2 months IC). ORR was significantly improved for lenalidomide vs IC (40% vs 11%; CR/CRu 5% vs 0%). Median time to first response was 4.3 months for lenalidomide (not reached for IC). Median DOR (16.1 vs 10.4 months) and OS on mature data (27.9 vs 21.2 months) were longer for lenalidomide vs IC. Efficacy results were consistent among subgroups. Safety data in 250 patients receiving ≥1 dose showed more dose reductions in lenalidomide-treated patients (41%) vs IC (17%), due in part to a longer median duration of lenalidomide treatment vs IC, and to strict dose modification rules for lenalidomide. The most common grade 3/4 adverse events (AEs) were neutropenia (lenalidomide 44% vs IC 34% [without increased risk of infection]), thrombocytopenia (18% vs 28%), and leukopenia (8% vs 11%). Tumor flare reaction occurred in lenalidomide patients only (10%; 2% grade ≥3); 1 patient in each arm experienced tumor lysis syndrome. Invasive second primary malignancies were identified in 4% and 5% of lenalidomide and IC treated patients, respectively. Conclusions: The MCL-002 study demonstrated a statistically significant and clinically meaningful improvement in PFS for lenalidomide over best IC monotherapy in patients with advanced R/R MCL despite a worse prognostic profile in the lenalidomide arm at baseline. In addition, ORR and CR rates, TTR, DOR, and OS were improved for lenalidomide over IC. The DOR has been remarkably consistent in various studies with lenalidomide in MCL patients. The safety profile for lenalidomide was as expected and no new safety signals were identified. The results of this first randomized, controlled study of lenalidomide showed superior efficacy compared to IC in patients with R/R MCL with a manageable toxicity profile. Table Efficacy of lenalidomide vs IC in R/R MCL Efficacy Lenalidomide (n=170) IC (n=84) P PFS (Lenalidomide vs IC) Median PFS, mo (95% CI) 8.7 (5.54-12.14) 5.2 (3.67-6.95) Sequential HR (95% CI) 0.61 (0.44-0.84) Sequential log-rank test p-value 0.004 ORR, n (%) 68 (40) 9 (11) <0.001 CR/CRu, n (%) 8 (5) 0 (0) 0.043 Median DOR, mo 16.1 10.4 0.421 Median OS, mo 27.9 21.2 0.52 Disclosures Trneny: Celgene, Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding. Walewski:Celgene: Consultancy, Other, Research Funding; Janssen-Cilag: Consultancy; Mundipharma : Consultancy, Research Funding; Roche: Consultancy, Honoraria, Other, Research Funding. Jurczak:Celgene, Eisai, Gilead, Janssen, Pharmacyclics, Pfizer, Roche, Novartis, Spectrum, Takeda, Teva: Research Funding. Belada:Celgene: Research Funding. Mayer:Janssen Research & Development: Research Funding; Roche: Research Funding; GlaxoSmithKline: Research Funding; Celgene: Research Funding. Biyukov:Celgene: Employment. Patturajan:Celgene: Employment. Casadebaig Bravo:Celgene: Employment. Arcaini:Celgene, Roche, Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Download Full-text

Inhibition of B-Cell Receptor Signaling Disrupts Cell Adhesion in Mantle Cell Lymphoma Via RAC2

Blood ◽

10.1182/blood-2018-99-118598 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 1369-1369

Author(s):

Weige Wang ◽

Franzen Carrie ◽

Hui Guo ◽

Jimmy Lee ◽

Yan Li ◽

...

Keyword(s):

Cell Adhesion ◽

B Cell ◽

Cell Lines ◽

Research Funding ◽

Cell Receptor ◽

Resistant Cell ◽

Advisory Committees ◽

Tumor Tissues ◽

Mantle Cell ◽

Bcr Signaling

Abstract Background: B-cell receptor (BCR) signaling pathway is recognized as a crucial pathway for the pathogenesis of neoplastic B-cells. Inhibition of the BCR signaling and the downstream pathway is highly effective in B-cell malignancy through Bruton tyrosine kinase inhibition by ibrutinib. In addition to cell proliferation inhibition, ibrutinib disrupts cell adhesion between tumor and its microenvironment through unknown molecular mechanisms, resulting in peripheral lymphocytosis with accompanying lymphadenopathy reduction in patients who receive ibrutinib. Methods and materials: In an effort to elucidate the link between BCR signaling and cell adhesion phenotype, we first characterized ibrutinib sensitive and resistant mantle cell lymphoma (MCL) cell lines. We measured cell proliferation and cell growth, and correlated ibrutinib sensitivity with cell adhesion disruption. We then used RNA-sequencing to identify differential pathways between sensitive or resistant cell lines in response to ibrutinib treatment. We validated RNA-Seq findings using cell lines, as well as animal models and human primary MCL tumor tissues and cells. Results: We found that intrinsic sensitivities of MCL cell lines to ibrutinib correlated well with their cell adhesion phenotype. RNA-sequencing revealed that BCR and cell adhesion gene signatures were simultaneously down-regulated by ibrutinib in ibrutinib-sensitive but not ibrutinib-resistant cell lines. Among the differentially expressed genes in the BCR gene signature, we identified and validated that RAC2, a regulator of cell adhesion, was down-regulated at both RNA and protein levels by ibrutinib only in ibrutinib-sensitive cells. Physical association of RAC2 with BLNK, an early BCR pathway adaptor, was disrupted by ibrutinib uniquely in sensitive cells. RAC2 knockdown with siRNA impaired cell adhesion while RAC2 over-expression rescued ibrutinib-induced reduction in cell adhesion. In a xenograft mouse model, mice treated with ibrutinib demonstrated tumor growth retardation along with down-regulation in RAC2 protein expression. Using immunohistochemical staining, we demonstrated that RAC2 was expressed in ~65% primary MCL tumor tissues with majority of RAC2-positive tumors characterized as being the more aggressive subtypes. Finally, primary MCL cells treated with ibrutinib demonstrated reduced RAC2 that is accompanied by cell adhesion impairment. Conclusions: Our findings uncover a novel cross-talk between BCR signaling and cell adhesion. Ibrutinib inhibits cell adhesion via down-regulation of RAC2. Our study highlights the importance of RAC2 and cell adhesion in MCL pathogenesis and new drug development. Disclosures Wang: Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Juno: Research Funding; AstraZeneca: Consultancy, Research Funding; MoreHealth: Consultancy; Pharmacyclics: Honoraria, Research Funding; Novartis: Research Funding; Dava Oncology: Honoraria; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Kite Pharma: Research Funding; Acerta Pharma: Honoraria, Research Funding.

Download Full-text

Developing Novel Therapeutic Strategies to Overcome Ibrutinib Resistance in Mantle Cell Lymphoma

Blood ◽

10.1182/blood.v126.23.707.707 ◽

2015 ◽

Vol 126 (23) ◽

pp. 707-707 ◽

Cited By ~ 2

Author(s):

Lan Pham ◽

Liang Zhang ◽

Wenjing Tao ◽

Donglu Zhao ◽

Hui Zhang ◽

...

Keyword(s):

Clinical Trial ◽

Disease Progression ◽

Cell Lines ◽

Research Funding ◽

Cell Lymphoma ◽

Mtor Inhibitors ◽

Resistant Cell ◽

20S Proteasome ◽

Ic50 Values ◽

Ibrutinib Resistance

Abstract MCL accounts for 7% of all non-Hodgkin lymphoma cases and is a rare and incurable subtype of B-cell lymphoma. Unfortunately, most MCL patients experience disease progression after frontline therapy, with a median overall survival of approximately 1-2 years after relapse; therefore, novel therapies for MCL are urgently needed. Ibrutinib, a first-in-class, once-daily, oral covalent inhibitor of Bruton's tyrosine kinase (BTK) was recently approved by the FDA to treat this disease. In our prior multiple-center phase II clinical trial, the overall response rate in relapsed/refractory MCL patients was 68%, with a median progression free survival (PFS) of 13.9 months, surpassing the effectiveness of other therapies. Based on our phase II clinical trial, approximately 48% of patients showed no response to ibrutinib or displayed initial positive responses to ibrutinib but also experienced disease progression within 12 months of treatment. Furthermore, the patients who initially show lengthy, durable responses to ibrutinb often acquire resistance and relapse at a median of 17 months. Once patients relapse after ibrutinib treatment, the 1-year survival rate is only 22%; therefore, the vast majority of MCL patients who experience disease progression after ibrutinib treatment will die within 12 months. Overall, the dismal outcomes of these patients demand that novel and pioneering approaches be taken to overcome ibrutinib resistance and improve the cure rate of MCL. To understand the mechanism(s) of acquired resistance for ibrutinib in MCL cells, we have recently generated two ibrutinib-resistant Jeko-1 and PF-1 MCL cell lines. These resistant cells were generated in culture by growing these cells in increasing concentrations of ibrutinib over a period of six months. The ibrutinib-resistant MCL cell lines were at least 8-10-fold more resistant to ibrutinib in comparison to the parental cell lines. The ibrutinib-resistant MCL cell lines were also cross-resistant to another BTK inhibitor, BGB, suggesting that BTK is the specific target in the resistant cell lines. Whole exome sequencing (WES) did not reveal any mutations in BTK or within the proximal BCR pathway, consistent with WES data on primary ibrutinib resistant MCL cases. Next, we conducted proteomics analyses using reverse-phase protein array (RPPA) to examine the protein expression profile of parental and ibrutinib-resistant MCL cell lines. We discovered a significant increase the levels of PI3K/AKT/mTOR/MCL-1 compensatory pathway components in both Jeko-1 and PF-1 ibrutinib-resistant cell lines when compared with their parental cells. Next, we screened for potential therapeutic agents that can overcome ibrutinib resistance. Of the many key agents tested, we discovered that the proteasome inhibitor carfilzomib (CFZ), the Bcl-2 inhibitor ABT-199, and the mTOR inhibitors BEZ and AZD demonstrated the greatest potential to overcome ibrutinib resistance in MCL cells. Interestingly, the ibrutinib-resistant MCL cells developed sensitization to CFZ. We found that the IC50 values of CFZ in the PF-1 ibrutinib-resistant cells were significantly lower (10-fold) in comparison to the IC50 values in the PF-1 parental line, which is consistent with primary MCL cells, where MCL cells derived from ibrutinib-resistant patients are more sensitive to CFZ than ibrutinib-naïve primary MCL cells. These findings are reflected by the function of the 20S proteasome because ibrutinib-resistant MCL cells have higher 20S proteasome activity. In contrast, MCL cell lines and primary MCL cells are highly sensitive to ABT-199 (IC50 < 50 nM) regardless of ibrutinib sensitivity, and ABT-199 is strictly dependent on Bcl-2 protein expression. Furthermore, based on our RPPA data, BEZ and AZD were used to target mTOR to determine whether mTOR inhibition reverses ibrutinib resistance. Our data showed that ibrutinib-resistant MCL cells are more highly resistant to both BEZ and AZD compared with the parental lines. Taken together, our data indicate that CFZ, ABT-199, and mTOR inhibitors have the potential to overcome ibrutinib resistance, and further investigation with in vivo models is warranted to validate our findings. Disclosures Pham: Amgen, Onyx, Millennium: Research Funding. Wang:Celgene: Research Funding.

Download Full-text

Targeting Oxphos Pathway Against Ibrutinib Resistance to Mantle Cell Lymphoma

Blood ◽

10.1182/blood.v128.22.290.290 ◽

2016 ◽

Vol 128 (22) ◽

pp. 290-290 ◽

Cited By ~ 1

Author(s):

Yang Liu ◽

Taylor Bell ◽

Hui Zhang ◽

Yuting Sun ◽

Carrie J Li ◽

...

Keyword(s):

Tumor Growth ◽

Mantle Cell Lymphoma ◽

Cell Lines ◽

Research Funding ◽

Cell Lymphoma ◽

Gene Set Enrichment Analysis ◽

Pdx Model ◽

Mantle Cell ◽

Ibrutinib Resistance

Abstract Background: Mantle cell lymphoma (MCL) is an aggressive B-cell malignancy that is initially responsive but ultimately relapses to frontline therapy. Ibrutinib, a first-in-class, once-daily, oral covalent inhibitor of Bruton's tyrosine kinase (BTK) has achieved 68% of overall response rate in relapsed/refractory mantle cell lymphoma (MCL) patients. However, the vast majority of MCL patients experience disease progression, demonstrating that standard-of-care approaches are failing and that a means for targeting ibrutinib resistant MCL is clinically needed. Our hypothesis is that the ibrutinib-resistant MCL may rely on the mitochondrial oxidative phosphorylation (OXPHOS) pathway to produce energy for tumor growth. In this study, we investigated the effects of IACS-010759, a small molecule mitochondrial complex I inhibitor discovered in MD Anderson Cancer Center which can block the OXPHOS pathway, to overcome ibrutinib resistance in MCL in vitro and in a patient-derived xenograft (PDX) model. Methods: The OXPHOS metabolic pathways were investigated by RNASeq in a panel of ibrutinib-sensitive and -resistant MCL samples. Cell growth inhibition assays were tested after 72-hour treatment with IACS-010759 in ibrutinib-resistant MCL cell lines, Z-138 and Maver-1, and ibrutinib-sensitive MCL cell lines, Rec-1, Mino, and Jeko-1, by CellTiter-Glo luminescent cell viability assay (Promega). Furthermore, an IBN-resistant MCL PDX model was established and the therapeutic effects and tolerability of IACS-010759 were investigated in the primary MCL-bearing PDX model. Results: We have done RNA sequencing (RNASeq) in 7 primary ibrutinib-resistant and 16 ibrutinib-sensitive MCL patient samples, and analyzed the data using Gene Set Enrichment Analysis (GSEA) software. The results demonstrated that the OXPHOS pathway was activated in the primary ibrutinib-resistant MCL cells but not ibrutinib-sensitive MCL cells. Based on the RNASeq data, we selected an OXPHOS inhibitor IACS-010759 to investigate its effects on both primary ibrutinib-resistant and ibrutinib-sensitive MCL cells in vitroand in PDX mice. IACS-010759 significantly inhibited cell proliferation in ibrutinib-resistant MCL cell lines, Z-138 and Maver-1, but not in ibrutinib-sensitive MCL cell lines, Rec-1, Mino, and Jeko-1, during a 72-hour incubation. Furthermore, the primary ibrutinib-resistant MCL PDX mice were administrated with 10 mg/kg IACS-10759 by oral gavage, for 28 days using a 5 on/2 off dosing schedule. Our data showed that IACS-010759 completely eradicated tumor growth in ibrutinib-resistant MCL PDX mice (n=5, p=0.045). All mice tolerated the treatment dose and no toxicity was found during 28 days of IACS-010759 treatment. Conclusions: The OXPHOS inhibitor IACS-010759 overcomes ibrutinib resistance both in vitro and in the PDX mouse model. The investigation of its mechanism-of-action is ongoing. IACS-010759 could have the potential for clinical use in ibrutinib-resistant relapsed/refractory MCL patients. Disclosures Wang: Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Asana BioSciences: Research Funding; Kite Pharma: Research Funding; Juno Therapeutics: Research Funding; Asana biosciences, Beigene, Celgene, Juno, Kite, Onyx, Pharmacyclics: Research Funding; Dava Oncology: Honoraria; BeiGene: Research Funding; Acerta: Consultancy, Research Funding.

Download Full-text

Genetic and Molecular Characterization of Ibrutinib-Resistant Mantle Cell Lymphoma: Designing Innovative Therapeutic Strategies

Blood ◽

10.1182/blood.v128.22.1838.1838 ◽

2016 ◽

Vol 128 (22) ◽

pp. 1838-1838 ◽

Cited By ~ 1

Author(s):

Hui Guo ◽

Shengjian Huang ◽

Yang Liu ◽

Carrie J Li ◽

Jack Wang ◽

...

Keyword(s):

Board Of Directors ◽

Research Funding ◽

Cell Lymphoma ◽

Therapeutic Strategies ◽

Rna Seq ◽

Biological Functions ◽

Advisory Committees ◽

Mantle Cell ◽

Resistant Patient ◽

Ibrutinib Resistance

Abstract Background Mantle cell lymphoma (MCL) is a B-cell malignancy with a broad spectrum of clinical, pathological, and biological features, and clinical evolution is usually very aggressive with short responses to treatment and frequent relapses. Ibrutinib is considered the drug of choice in relapsed-refractory cases but patients may develop resistance as some patients in complete remission (CR) have not relapsed yet and are in long term follow-up. The understanding of the resistance mechanisms and the emergence of new drugs targeting key oncogenic mechanisms are providing the basis for designing innovative therapeutic strategies to overcome ibrutinib resistance, both in preclinical studies and preliminary clinical trials. Methods We identified differentially expressed genes (DEGs) in 7 ibrutinib-primary resistant MCL patient samples compared with 16 ibrutinib-sensitive MCL patient samples by next generation sequencing (RNA-Seq) and top28-gene signature were developed via Gene Set Enrichment Analysis (GSEA) analysis of RNA-Seq data, and we also verified the expression level of these genes in ibrutinib-resistant and-sensitive MCL patient samples using Real time-PCR, and then a secondary focus of this study was to identify potential predictive biomarkers for therapy in relapsed or refractory MCL. In order to place the gene expression data into a biological context, Ingenuity Pathway Analysis (IPA) software was used to assign the DEGs to know the canonical pathways and functional networks in order to predict the biological functions of the transcriptional changes. Results We identified top-28 DEGs in five ibrutinib-resistant MCL patient samples compared with four ibrutinib-sensitive MCL patient samples. We performed gene enrichment and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG pathway) of differentially expressed genes of each samples and verified the predicted genes using Real time-PCR, which were truly related to MCL and not false positive results. Moreover, Using IPA software, we identified that the enriched biological functions in the MCL ibrutinib-resistant patient samples were Oxidative phosphorylation, Mitochondrial Dysfunction and TCA Cycle (Eukaryotic), which were enriched biological functions in the analysis of RNA-Seq data, and which may be targeted by oncogenic events in MCL, and they may influence the tumor response to new therapeutic agents. We also found that expression of these genes (SEPT3, FASN, IDH3A, SLC1A5, INPP5J, CCT5, MTHFD1) was significantly increased in five ibrutinib-resistant MCL patient samples compared with four ibrutinib-sensitive MCL patient samples, and we used IPA to identify some functionally related genes with these genes increased in MCL ibrutinib-resistant patient samples and built networks based on the molecular relationships most relevant to this project. Conclusion These data identify a genomic basis for ibrutinib-primary resistance in MCL and provide the important insights into the strategy to address the problem of ibrutinib-resistance, and will hopefully allow more tailored and specific therapies to be designed. Disclosures Wang: Onyx: Research Funding; Pharmacyclics: Research Funding; Celgene: Research Funding; Kite Pharma: Research Funding; Asana BioSciences: Research Funding; BeiGene: Research Funding; Juno Therapeutics: Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Download Full-text

Oncogenic MALT1 Promotes Cell Survival and Mediates Ibrutinib Resistance and Ibrutinib-Venetoclax Resistance in Mantle Cell Lymphoma

Blood ◽

10.1182/blood-2020-140871 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 18-18

Author(s):

Vivian Changying Jiang ◽

Junwei Lian ◽

Shengjian Huang ◽

Shaojun Zhang ◽

Yang Liu ◽

...

Keyword(s):

Cell Survival ◽

Cell Lines ◽

Research Funding ◽

Cell Lymphoma ◽

Mtor Signaling ◽

Mantle Cell ◽

Whole Transcriptome Sequencing ◽

Ibrutinib Resistance ◽

Whole Transcriptome

Both as monotherapies and in combination, the Bruton's tyrosine kinase inhibitor ibrutinib and the BH3 mimetic BCL2 inhibitor venetoclax have proven to be efficacious and are now widely used treatment options for mantle cell lymphoma (MCL) patients. However, mono- and dual- resistance frequently develops, necessitating investigation into the mechanisms mediating resistance to these therapies. To investigate the mechanism of ibrutinib resistance, we generated two ibrutinib-resistant cells due to marked BTK knockdown via CRISPR/CAS9 from JeKo-1, which is ibrutinib-sensitive and venetoclax-resistant. To understand the mechanism of venetoclax resistance, we generated three venetoclax-resistant cell lines with acquired resistance via chronic exposure to increasing doses of venetoclax from ibrutinib/venetoclax double sensitive Mino and Rec-1 cells, and ibrutinib-resistant but venetoclax-sensitive Granta519 cells. All these paired cell lines with various resistance to ibrutinib and venetoclax were subject to whole transcriptome sequencing of these paired MCL cell lines. We discovered that mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is significantly overexpressed in ibrutinib-resistant and ibrutinib-venetoclax dual-resistant MCL cells, especially in cells with BTK knockdown. This was further validated in primary MCL patient cells (n=24). Interestingly, MALT1 overexpression inversely correlates with CARD11 expression and enhances non-canonical NF-κB signaling, suggesting a switch from a highly-dependent BTK-CARD11 mechanism to an independent mechanism in both ibrutinib-resistant and ibrutinib-venetoclax dual-resistant MCL cells. Chromosomal translocations of MALT1 are the hallmarks of MALT lymphoma, which result in oncogenic fusion of MALT1 products. MALT1 is constitutively active in driving aggressive ABC-type DLBCL. This indicates MALT1 can be oncogenic when its activity is dysregulated. Therefore, we hypothesized that constitutive MALT1 activity may be responsible for the resistance to ibrutinib and venetoclax in MCL cells. To demonstrate this relationship, MALT1 ablation using genetic manipulation resulted in significant growth defects both in vitro and in vivo. Pharmaceutical approaches using MALT1 inhibitor MI-2 resulted in similar effects on cell survival and using cell viability assays. Whole transcriptome sequencing analysis revealed that MYC, NF-kB, ROS, cell cycle and mTOR signaling are the most significantly downregulated pathways upon MI-2 treatment. Intriguingly, MYC, NF-kB, PI3K-AKT-mTOR and mTOR signaling pathways were reported to be upregulated in ibrutinib-resistant MCL cells compared to sensitive MCL cells. To address this further, proteomics analysis by reverse phase protein array (RPPA) using more than 400 antibodies confirmed that MI-2 significantly downregulated AKT-mTOR signaling. NF-kB modulation, ROS production, AKT-mTOR, and metabolism changes were further confirmed through multiple biochemical approaches. In addition, MI-2 treatment resulted in a dramatic reduction of MALT1 expression, suggesting that MI-2 treatment affected both its scaffold and paracaspase activities. Furthermore, MI-2 treatment resulted in significant inhibition of in vivo tumor growth of ibrutinib-venetoclax dual-resistant MCL subcutaneous xenografts and tumor homing to the spleen and bone marrow in an ibrutinib-venetoclax dual-resistant MCL patient-derived xenograft (PDX) mouse model. In conclusion, we discovered that MALT1, an essential regulator of NF-κB signaling, is hyperactive in ibrutinib-resistant cells and ibrutinib-venetoclax dual-resistant MCL cells, which puts MALT1 forward as a potentially new therapeutic target in ibrutinib and venetoclax-resistant MCL tumors. Genetic depletion or pharmaceutical inhibition of MALT1 resulted in remarkable defects in cell survival and cell proliferation. The MALT1 inhibitor MI-2 proved its in vivo potency by its pro-apoptotic effect and its significant tumor growth inhibition. In conclusion, targeting a hyperactive MALT1 is a promising therapeutic strategy that could lead to clinical implementation of a new treatment strategy meant to overcome ibrutinib and ibrutinib-venetoclax dual resistance in MCL patients by reversing the NF-kB and ROS/mTOR- mediated resistance in these tumors. Disclosures Wang: Targeted Oncology: Honoraria; Loxo Oncology: Consultancy, Research Funding; Pulse Biosciences: Consultancy; Kite Pharma: Consultancy, Other: Travel, accommodation, expenses, Research Funding; Juno: Consultancy, Research Funding; BioInvent: Research Funding; VelosBio: Research Funding; Acerta Pharma: Research Funding; InnoCare: Consultancy; Oncternal: Consultancy, Research Funding; Nobel Insights: Consultancy; Guidepoint Global: Consultancy; Dava Oncology: Honoraria; Verastem: Research Funding; Molecular Templates: Research Funding; OncLive: Honoraria; Beijing Medical Award Foundation: Honoraria; Lu Daopei Medical Group: Honoraria; MoreHealth: Consultancy; Celgene: Consultancy, Other: Travel, accommodation, expenses, Research Funding; AstraZeneca: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding; Pharmacyclics: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding; Janssen: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding; OMI: Honoraria, Other: Travel, accommodation, expenses.

Download Full-text

The Novel Multitarget Small-Molecule Inhibitor SRX3177 Overcomes Ibrutinib Resistance in Mantle Cell Lymphoma

Blood ◽

10.1182/blood-2021-154253 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 2262-2262

Author(s):

Dhananjaya Pal ◽

Cody C. McHale ◽

Samon Benrashid ◽

Poornima Gourabathini ◽

Krishnaiah Maddeboina ◽

...

Keyword(s):

Cell Cycle ◽

Board Of Directors ◽

Cell Lines ◽

Small Molecule ◽

Research Funding ◽

Single Agent ◽

Advisory Committees ◽

Molecule Inhibitor ◽

Mantle Cell ◽

Ibrutinib Resistance

Abstract Mantle cell lymphoma (MCL) is an aggressive, rare, and difficult to treat subtype of non-Hodgkin's Lymphoma (NHL) that accounts for about 6% of all cases. Although there is no defined standard of care for MCL treatment, some combination of chemo-immunotherapy and rituximab maintenance with or without autologous stem cell transplantation is generally employed depending on the age and fitness of the patient. Despite recent development of novel therapeutics, there is inevitable disease relapse with progressively declining efficacy and increasing frequency of resistance with single agent targeted therapy. Here, we describe the novel multitarget inhibitor SRX3177 which simultaneously hits three oncogenic targets: phosphatidylinositol-3 kinase (PI3K), cyclin-dependent kinases 4 and 6 (CDK4/6), and the epigenetic reader protein BRD4. This in silico designed, thieno-pyranone (TP) scaffold-based small molecule inhibitor orthogonally disrupt three targets within the cancer cell with one agent. Targeting the cell cycle with small molecule inhibitors represents a reasonable attempt to treat MCL, as cell cycle-associated genes like ATM, TP53, CDKN2A, CCND1 and CDK4/6 are most frequently mutated in patients. Palbociclib is a well-known single agent CDK4/6 inhibitor that has been employed in both solid and hematological malignancies. Due to its cytostatic nature, treatment with single agent palbociclib often results in the emergence of treatment-resistant clones. Therefore, a combination strategy would theoretically be more effective and can overcome the development of resistance. Moreover, prolonged G1 arrest by CDK4/6 inhibition sensitizes lymphoma cells to PI3K inhibition, suggesting a synthetic lethality relationship between these two agents. Inhibiting the chromatin reader protein BRD4 causes downregulation of target genes c-MYC and BCL2, further increasing cytotoxic capabilities. Hence, we developed SRX3177 as a potent CDK4/6/PI3K/BRD4 triple inhibitor to synergistically inhibit cell cycle progression and induce cancer cell apoptosis. SRX3177 is an ATP competitive CDK4/6 inhibitor (IC 50: CDK4 = 2.54 nM, CDK6 = 3.26 nM), PI3K inhibitor (IC 50: PI3Kα = 79.3 nM, PI3Kδ = 83.4 nM), and BRD4 inhibitor (IC 50: BD1 = 32.9 nM, BD2 = 88.8 nM). We have tested the efficacy of SRX3177 against a panel of MCL cell lines and report that SRX3177 induces a strong antiproliferative activity with maximal IC 50 0f 340 nM in JeKo-1, 29 nM in Mino cells, and 630 nM for Rec-1 cells while IC 50 values for cell lines Granta and JVM-2 were 1.3 µM and 1.5 µM, respectively. Further, we show that SRX3177 is more potent to tumor cells than the individual PI3K (BKM120), BTK (Ibrutinib), BRD4 (JQ1), and CDK4/6 (palbociclib) inhibitors, and dual PI3K/BRD4 inhibitor SF2523 (backbone for SRX3177) in JeKo-1 cells. Next, we examine the cytotoxic effect of SRX3177 in ibrutinib/palbociclib resistant primary MCL cells. Our results show that SRX3177 triggers cytotoxic response at 500 nM and 1000 nM as compared to the lack of cytotoxicity of combination Ibrutinib and palbociclib at 150 nM and 1000 nM (Fig 1). SRX3177 induces a strong apoptotic response and cell cycle arrest in JeKo-1 and Mino cells at 24hrs. Annexin V/7AAD apoptosis staining confirmed the induction of PCD by SRX3177with increase in c-PARP. Western blot analysis shows SRX3177 treatment blocks both PI3K/AKT signaling and Rb phosphorylation. Moreover, analysis by chromatin immunoprecipitation revealed that SRX3177 effectively blocked BRD4 binding to both the promoter and enhancer of c-MYC (p≤0.01 and p≤0.001) and BCL2 (p≤0.05). SRX3177 also suppresses the c-MYC and BCL2 transcriptional program in both a time- and dose-dependent manner. Our findings also demonstrate a SRX3177-dependent reduction in c-MYC half-life via induction of proteasomal-mediated degradation. This degradation is associated with decreased phosphorylation of c-MYC at Ser62 and increased phosphorylation of c-MYC at Thr58 - indicative of differential regulation of c-MYC stability. Finally, we show that SRX3177 overcomes chronic ibrutinib resistance in Jeko-1 cells with a maximal IC 50 of 150 nM as compared to 64 µM with ibrutinib. Hence, the triple inhibitor SRX3177 has superior potency to ibrutinib in MCL cell lines and succeeds in overcoming ibrutinib-resistance at nanomolar doses. Taken together, our data supports the development of SRX3177 as a novel therapeutic agent for treatment of MCL. Figure 1 Figure 1. Disclosures Martin: ADCT: Consultancy. Park: Takeda: Research Funding; G1 Therapeutics: Consultancy; Teva: Consultancy, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Research Funding, Speakers Bureau; Gilead: Speakers Bureau; Rafael Pharma: Membership on an entity's Board of Directors or advisory committees, Other: Advisory Board; Morphosys: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding. Durden: SignalRx Pharmaceuticals: Current holder of individual stocks in a privately-held company.

Download Full-text

Pre-Clinical Evaluation of the PI3K-p110β/δ Inhibitor KA2237 in Mantle Cell Lymphoma

Blood ◽

10.1182/blood.v128.22.1837.1837 ◽

2016 ◽

Vol 128 (22) ◽

pp. 1837-1837 ◽

Cited By ~ 3

Author(s):

Shengjian Huang ◽

Loretta J. Nastoupil ◽

Hui Guo ◽

Taylor Bell ◽

Makhdum Ahmed ◽

...

Keyword(s):

Cell Viability ◽

Tumor Cells ◽

Cell Lines ◽

Research Funding ◽

Synergistic Effects ◽

Resistant Cell ◽

Dependent Manner ◽

Advisory Committees ◽

Mantle Cell ◽

Dose Dependent

Abstract Background: Mantle cell lymphoma (MCL) accounts for 6% of all non-Hodgkin lymphoma and is a therapeutic challenge. Phosphoinositide-3 kinase (PI3K) has been shown to be an alternative survival pathway in relapsed/refractory MCL. KA2237 (designed by Karus Therapeutics Ltd, Oxfordshire, United Kingdom) is a dual inhibitor of the class I beta and delta isoforms of the 110 kDa catalytic subunit of PI3K. By selectively targeting PI3K-beta and -delta isoforms and preventing their activation, KA2237 may decrease proliferation and induce cell death in susceptible tumor cells. Methods: We assessed the effects of KA2237 on the in vitro cell proliferation of both ibrutinib-sensitive (Mino, Jeko-1, and Rec-1) and primary ibrutinib-resistant (Z-138 and Maver-1) cell lines, and acquired ibrutinib-resistant MCL cell line, Jeko-R. We also tested the viability of patient-derived xenograft (PDX) tumor cells to KA2237. We compared the efficacy of KA2237 with two other commercial PI3K inhibitors, duvelisib (IPI-145, Selleck) and idelalisib (Cal-101, Selleck). Also, we paired these three inhibitors (KA2237, duvelisib and idelalisib) each with ibrutinib to evaluate the potential synergistic effects of these combinations. Lastly, we also tested in vivo efficacy of KA2237 and its combination with ibrutinib in PDX tumor cells. Results: KA2237 inhibited cell proliferation in both ibrutinib-sensitive and ibrutinib-resistant cell lines in a dose-dependent and time-dependent manner. For Mino and Jeko-1, the IC50 was 4.8 uM and 2.9 uM and for Z-138 and Maver-1 cell lines, the IC50 was 0.6 uM and 0.1 uM, respectively. KA2237 also decreased cell viability of ibrutinib-sensitive and ibrutinib-resistant MCL PDX tumor cells. However, KA2237 did not decrease the cell viability of normal human peripheral blood mono-nuclear cells. KA2237 arrested phase G0/G1 in Rec-1 and Jeko-R cell lines. We detected the expression of PI3K isoforms in MCL, finding higher expression of PI3K β and δ in MCL-resistant cell lines as compared with sensitive cell lines. We found that KA2237 induced MCL cell apoptosis in a time-dependent and dose-dependent manner. In comparison with duvelisib and idelalisib, KA2237 achieved greater inhibition of cell viability, cell apoptosis and cell cycle arrest. Furthermore, we found synergistic effects of KA2237 and ibrutinib combination in several MCL cell lines and in PDX models. In an ibrutinib-resistant PDX model, KA2237 treated mice reduced tumor burden significantly compared with vehicle control, and higher tumor growth inhibition was achieved as compared with ibrutinib. Conclusion: The novel PI3K inhibitor, KA2237 may be a potential candidate for MCL therapy, especially in the ibrutinib-resistant cases. Disclosures Wang: Acerta Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Juno Therapeutics: Research Funding; Pharmacyclics: Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Onyx: Research Funding; BeiGene: Research Funding; Asana BioSciences: Research Funding; Kite Pharma: Research Funding; Celgene: Research Funding.

Download Full-text