Selective Bcl-2 Inhibition With ABT-199 Is Highly Active Against Chronic Lymphocytic Leukemia (CLL) Irrespective Of TP53 Mutation Or Dysfunction

Abstract Aim CLL is characterized by universal overexpression of the anti-apoptotic protein Bcl-2 which promotes inappropriate survival and chemotherapy resistance. ABT-199 is a Bcl-2 selective BH3-mimetic molecule currently in phase I clinical trials for the treatment of CLL. Del(17p) is a key negative prognostic indicator in CLL, associated with reduced response rates, progression-free and overall survival with standard therapy. Reduction or loss of TP53 function is considered the biological basis for its impact. Consistent with this, TP53 mutations in CLL lacking del(17p) also confer similar negative prognostic effects. BH3-mimetics are small molecule inhibitors that theoretically act downstream of TP53. We therefore hypothesized that ABT-199 will be equally effective in patients (pts) with CLL irrespective of TP53 function. We aimed to: (i) examine the incidence of TP53 aberrations in a heavily pretreated group of patients referred to two centers for ABT-199 therapy; (ii) determine the impact of TP53 aberrations on in vitro and clinical responses of CLL to ABT-199; and (iii) determine if CLL cells deficient in TP53 pathway function are as sensitive to ABT-199 as CLL with intact TP53 function. Methods This work was conducted in parallel with phase I clinical trials of ABT-199 monotherapy (NCT01328626; n = 25) or monotherapy followed by combination with rituximab (NCT01682616; n = 5) in pts with relapsed and refractory (r/r) CLL, after written, informed consent. Pts were tested for potential TP53 aberration using (i) FISH for del(17p); (ii) bone marrow (BM) immunohistochemistry (IHC) for elevated TP53 expression (>20% CLL cells staining positive on BM trephine); (iii) a 72hour in vitro nutlin-3a cytotoxicity assay for functional assessment of the TP53 pathway; and (iv) targeted next generation sequencing of the TP53 gene (with confirmatory Sanger sequencing) to detect deleterious mutations. Del(17p) and TP53 status of CLL samples at screening was determined and correlated with in vitro responses to ABT-199 after 24 hours and objective clinical responses to therapy with ABT-199 as determined within the trial protocol using iwCLL criteria. Results In this r/r group of CLL pts, 13/30 (43%) had evidence of del(17p) by FISH (range 9 - 90% of cells); 15/28 (54%) had evidence of TP53 mutation by sequencing; and 7/29 (24%) had TP53 overexpression by IHC, all of whom had TP53 mutations. For 27 pts with data for all three assays, ten had no evidence of TP53 abnormality. In the 10 samples with >20% del(17p) by FISH, deleterious TP53 mutations were detected in all. For the purposes of comparing responses to ABT-199 by TP53 status, three categories were identified: negative for both del(17p) and p53 mutation, positive for one only, and positive for both (table 1). CLL cells in all groups were similarly highly sensitive in vitro to ABT-199 (ANOVA p>0.05). The overall response rate was at least 87.5% in all groups. Given that CLL is characterized by heterogeneity for TP53 aberrations within individual patients, we selected four samples with high level del(17p) and TP53 mutations for assessment of TP53 function. All showed resistance to nutlin 3a-induced cytotoxicity (median IC50 12mM [95%CI 9 – 41mM]) when compared with CLL cells without del(17p) or TP53 mutations which were 15 – 30-fold more sensitive. No differences in vitro sensitivity to ABT-199 were detected when these nutlin-3a resistant samples were compared with cells lacking TP53 mutations or del(17p). Conclusions Defects in the TP53 pathway are present in the majority of patients with heavily pretreated CLL; novel treatment for such patients must include activity against TP53 aberrant clones. CLL cells lacking TP53 pathway function have similar sensitivity to ABT-199 in vitro as do TP53 pathway intact cells, and clinical responses were observed in ≥87.5% of patients. These data suggest that ABT-199 should be evaluated alone and in combination in pts with TP53-aberrant lymphoid neoplasms. Disclosures: Anderson: Abbvie: Research Funding. Off Label Use: ABT-199 is an unlicensed drug currently in phase I and II studies in patients with chronic lymphocytic leukemia. Seymour:Roche: Honoraria, Membership on an entity’s Board of Directors or advisory committees; Genentech: Honoraria, Membership on an entity’s Board of Directors or advisory committees. Huang:Genentech: Employee of Walter and Eliza Hall Institute which recieves commercial income related to ABT-199. Other, Research Funding; Abbvie: Research Funding. Roberts:Abbvie: Research Funding; Genentech: Employee Walter and Eliza Hall Institute which recieves commercial income related to ABT-199. Other, Research Funding.

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The Broad Spectrum of TP53 Variants in CLL: NGS Analysis of 573 Pathogenic TP53 Variants

Blood ◽

10.1182/blood-2019-130907 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 3021-3021

Author(s):

Gregory Lazarian ◽

Floriane Theves ◽

Myriam Hormi ◽

Virginie Eclache ◽

Stéphanie Poulain ◽

...

Keyword(s):

Tumor Progression ◽

Board Of Directors ◽

Research Funding ◽

Lymphocytic Leukemia ◽

Fish Analysis ◽

Snp Analysis ◽

Advisory Committees ◽

Exon 2 ◽

Tp53 Mutations ◽

Mutational Status

TP53 aberrations, including somatic mutations of TP53 gene or 17p deletion leading to the loss of the TP53 locus, are a major predictive factor of resistance to fludarabin based chemotherapy in chronic lymphocytic leukemia (CLL) and remain an adverse prognostic factor in the chemofree era. Therefore, detection of TP53 alteration before each new line of treatment is required for theranostic stratification. In order to better characterize the distribution and combination of the TP53 variants in CLL, we collected the TP53 sequencing data of 343 patients harboring TP53 mutations from centers of the French Innovative Leukemia Organization-CLL (FILO) and established a large data base of 573 TP53 mutations. Mutations were identified through NGS sequencing (covering exon 2 to 11) allowing the detection of low frequency variants down to 1% VAF. Several distinct low VAF mutations were orthogonally confirmed by digital PCR. TP53 variants were analyzed through UMD_TP53 data gathering 90 000 TP53 mutations from all type of cancers. IGHV mutational status and FISH analysis were available for 224 and 176 patients respectively. Using ACMG criteria from the UMD_TP53 database, we confirmed that 523 could be classified as pathogenic, 42 were likely pathogenic and 8 were VUS (Variants of Unknown Significance). As expected, the mutation distribution along the p53 protein exhibited a clustering of variants in the DNA binding domain of the protein. We also confirmed the presence of a specific hotspot at codon 234 (6%) which is noticeable in other CLL cohorts but absent in solid tumors. 431 TP53 variants led to the expression of a mutant protein whereas the remaining 142 led a TP53 null phenotype. For 8 patients without 17p deletion and a mutation VAF larger than 50%, SNP analysis indicate that these tumors had a copy number neutral loss of heterozygosis at 17p with a duplication of the mutant allele leading to homozygous mutations of TP53. When focusing on the allele burden of TP53 mutations, 264/573 (46%) variants had an allele frequency <10%. Even if they were predominantly found in polymutated cases, presence of only low VAF (<10%) mutations was evidenced in 74 (21%) patients (50 patients with a single TP53 mutation and 24 patients with more than one). All these cases would have been missed by conventional sequencing. Among the 343 patients, 113 (33%) were poly-mutated and harbored more than one pathogenic TP53 variants (2 to 11 variants per patient): 57 (16,7 %) had 2 variants, 32 (9,3%) had 3, 10 had 4 (3%) and 14 patients (4%) had 5 to 11 variants. Using both long range sequencing and in silico analysis, we could show that all these variants were distributed in different alleles supporting an important intratumoral heterogeneity and a strong selection for TP53 loss of function during tumor progression in these patients. Null variants were rarely found as single alteration: only 46 patients (13,4%) patients harbored a single null mutation. Null mutations were predominantly found in patients with multiclonal mutations (87% with 4 or more). Median size of variants significantly decreased with the number of mutations and most of low VAF (less than 10%) variants were found in multiclonal combinations. Multiclonal mutations were predominantly found in previously treated patients (41% treated versus 10 % untreated) but whether all these variants preceded treatment and were further selected is currently unknown. We observed that 71,5 % of patients were IGHV unmutated and multiclonal mutations were surprisingly more frequent in mutated IGHV cases than in unmutated ones. Only 50% of cases carried a 17p deletion, highlighting again the importance of testing for TP53 mutations in addition to FISH analysis. Presence or absence of 17p deletion was unrelated to the number of TP53 mutations. Taken together these observations suggest that the TP53 mutational landscape in CLL is very complex and can involve multiple mechanisms, converging to a total loss of TP53 function and tumor progression. NGS provides a powerful tool for detecting all these alterations including variants with low VAF and should become a standard for CLL screening prior to each line of treatment. Disclosures Leblond: Amgen: Honoraria, Speakers Bureau; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Honoraria, Speakers Bureau; Astra Zeneca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Letestu:Abbvie: Membership on an entity's Board of Directors or advisory committees, Other: speaker fee, expert contracts; Janssen: Membership on an entity's Board of Directors or advisory committees, Other: speaker fee, expert contracts; Roche: Membership on an entity's Board of Directors or advisory committees, Other: speaker fee, expert contracts; Alexion: Membership on an entity's Board of Directors or advisory committees, Other: speaker fee, expert contracts. Cymbalista:Abbvie: Honoraria; Roche: Research Funding; Sunesis: Research Funding; Gilead: Honoraria; Janssen: Honoraria; AstraZeneca: Honoraria.

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Selinexor Demonstrates Marked Synergy with Dexamethasone (Sel-Dex) in Preclinical Models and in Patients with Heavily Pretreated Refractory Multiple Myeloma (MM)

Blood ◽

10.1182/blood.v124.21.4773.4773 ◽

2014 ◽

Vol 124 (21) ◽

pp. 4773-4773 ◽

Cited By ~ 4

Author(s):

Christine I. Chen ◽

Martin Gutierrez ◽

David S. Siegel ◽

Joshua R. Richter ◽

Nina Wagner-Johnston ◽

...

Keyword(s):

Board Of Directors ◽

Transcriptional Activation ◽

Nuclear Export ◽

Research Funding ◽

Phase 1 ◽

Advisory Committees ◽

Nuclear Retention ◽

Heavily Pretreated ◽

Equity Ownership

Abstract Introduction: The nuclear export protein exportin 1, (XPO1) is overexpressed in a wide variety of cancers including MM and often correlate with poor prognosis. Selinexor (KPT-330) is an oral Selective Inhibitor of Nuclear Export (SINE) XPO1 antagonist in Phase 1 and 2 clinical studies. Selinexor forces nuclear retention and reactivation of tumor suppressor proteins (TSPs) and reduction of many proto-oncogenes, including MDM2, MYC and Cyclin D. In addition, selinexor potently deactivates NF-κB, through forced nuclear retention of IκBα. Together these effects induce selective apoptosis in MM cells and inhibition of NF-κB dependent osteoclast activation. XPO1 is also responsible for nuclear export of the glucocorticoid receptor (GR). We hypothesized that selinexor will enhance the activity of dexamethasone (DEX)-bound GR, resulting in synergistic tumor cell killing. Methods: In vitro tumor cell viability measurements were based on MTT (CellTiter 96¨/Promega) and combination indices were calculated using CalcuSyn software. For xenograft studies, utilized NOD-SCID mice with subcutaneous inoculation of MM.1s cells. GR nuclear localization was measured with immunofluorescent anti-GR (phosphor-S211) antibody and quantitative imaging. To assess GR transcriptional activation, GR binding to a GCR consensus sequence was measured in nuclear extracts using an ELISA method (GR ELISA kit/Affymetrix). Patients (pts) with heavily pretreated refractory MM were dosed with oral selinexor at doses of up to 60 mg/m2 (8-10 doses/4 wk cycle) as part of a Phase 1 program in advanced hematological malignancies. Response we defined based on the IMWG criteria. The effect of combining DEX with selinexor was analyzed in all pts who received selinexor at moderate to high doses (30-60 mg/m2). Safety and efficacy were analyzed separately in three groups: no DEX, <20 mg DEX and 20 mgs DEX. Results: In MM.1s cells Sel-Dex showed synergy for nuclear retention of the DEX activated GR (Ser211-phosphorylated) and concomitant GR transcriptional activation. Sel-Dex showed highly synergistic cytotoxicity in MM.1s cells in vitro and in vivo, with a corresponding increase in apoptosis. Selinexor alone was potently cytotoxic in the DEX resistant MM cell lines MM.1R and ANBL6, but addition of DEX provided no additional effect. Twenty-eight pts with heavily pretreated refractory MM (16 M, 12 F; median age 62; ECOG PS 0/1: 7/21; median prior regimens: 6) received selinexor at 30 – 60 mg/m2 with either 0, <20, or 20 mgs DEX. All pts have received a proteasome inhibitor and an Imid and the majority of the pts have received pomalidomide (68%) and/or carfilzomib (36%). The most common Grade 1/2 AEs for these three groups were: nausea (82%/86%/70%), fatigue (55%/86%/40%), anorexia (36%/71%/60%), and vomiting (36%/57%/10%). Of the 28 pts treated; 10 heavily pretreated refractory MM pts treated with a combination of selinexor (45 mg/m2 twice weekly) and DEX (20 mg with each selinexor dose) were found to have dramatically improved disease response (n=10, ORR 60%), with one stringent complete response (sCR, 10%), 5 partial responses (PR, 50%) and clinical benefit rate (CBR) rate of 80% (Figure 1). Treatment with ³30mg/m2 selinexor and <20 mg DEX (n=7), resulted in ORR of 14% and CBR of 86%, while treatment with selinexor (30-60 mg/m2) without DEX (n=12) showed best response of stable disease (50%). Sel-Dex was also associated with an increase in time on study relative to selinexor alone, with 7 of out 10 pts in the 20 mg DEX combo group still on study (11-25 weeks). Five additional pts were treated with selinexor at a dose of 60 mg/m2 in combination with 20 mg DEX. Response evaluation is pending. Conclusions: Sel-Dex combination is markedly synergistic in preclinical models, which is supported by the preliminary clinical data presented. One potential mechanism underlying this synergy is the amplification of GR activity due the combined effects of selinexor-induced nuclear retention of activated GR coupled with DEX-mediated GR agonism. These results provide a promising basis for the continuing study of Sel-Dex for treatment of pts with refractory MM. Phase 2 studies of Sel-Dex in pts with MM refractory to both pomalidomide and carfilzomib are planned for early 2015. Disclosures Chen: Celgene: Honoraria; Janssen: Honoraria. Off Label Use: Lenalidomide maintenance therapy after ASCT. Gutierrez:Senesco: PI Other. Siegel:Celgene, Millennium, Onyx: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Baz:Celgene: Research Funding; Millennium: Research Funding; Bristol Myers Squibb: Research Funding; Karyopharm: Research Funding; Sanofi: Research Funding. Kukreti:Celgene: Honoraria. Azmi:Karyopharm Therpeutics: Research Funding. Kashyap:Karyopharm Therapeutics: Employment. Landesman:Karyopharm Therapeutics: Employment. Marshall:Karyopharm Therpeutics: Employment. McCartney:Karyopharm Therpeutics: Employment. Saint-Martin:Karyopharm Therpeutics: Employment. Norori:Karyopharm Therpeutics: Consultancy. Savona:Karyopharm Therpeutics: Membership on an entity's Board of Directors or advisory committees. Rashal:Karyopharm Therapeutics: Employment. Carlson:Karyopharm Therapeutics: Employment. Mirza:Karyopharm Therpeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Shacham:Karyopharm Therapeutics Inc.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Kauffman:Karyopharm Therapeutics: Employment, Equity Ownership. Reece:Millennium: Honoraria, Research Funding; Millennium: Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Otsuka: Honoraria, Research Funding; Otsuka: Honoraria, Research Funding; Merck: Research Funding; Merck: Research Funding; BMS: Research Funding; BMS: Research Funding; Novartis: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Amgen : Honoraria; Amgen : Honoraria.

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Phase I/Ib Study of the Novel Immunotoxin MT-3724 in Relapsed/Refractory Non-Hodgkin's B-Cell Lymphoma (NHL)

Blood ◽

10.1182/blood.v126.23.5112.5112 ◽

2015 ◽

Vol 126 (23) ◽

pp. 5112-5112

Author(s):

Paul A Hamlin ◽

Catherine S. Diefenbach ◽

David J. Valacer ◽

Jack Higgins ◽

Michelle A. Fanale

Keyword(s):

B Cells ◽

Phase I ◽

B Cell ◽

Board Of Directors ◽

Research Funding ◽

B Cell Lymphoma ◽

Advisory Committees ◽

Dose Cohort ◽

Mixed Response

Abstract Background CD20 is selectively expressed on the surface of early pre-B-cells, remains throughout B-cell development, and is then lost from plasma cells. Because CD20 is present on the majority of B-cell lymphomas, anti-CD20 monoclonal antibody (MAb) therapy is widely employed in the treatment of NHL. However a majority of NHL patients eventually become refractory to CD20 MAb(s). Resistance mechanisms may include increased MAb catabolism, initial or post treatment selection of low CD20 expressing tumor cells, trogocytosis of surface CD20, failure of MAb effector mechanisms and/or impaired patient immune cell function. MT-3724 is a recombinant fusion protein consisting of a CD20 binding variable fragment (scFv) fused to the enzymatically active Shiga-like toxin-I A1 subunit (SLT-I A1). SLT-I A1 is an N-glycosidase that catalytically inactivates 60S ribosomal subunits causing inhibition of protein synthesis. Upon its scFv binding to cell surface CD20 in vitro, SLT-I A1 forces MT-3724 internalization which then routes in a predictable fashion to the cytosol and irreversibly inactivates the cell ribosomes triggering cell death. MT-3724 has been shown to specifically bind and kill CD20+ malignant human B-cells in vitro and non-human primate (NHP) B-cells in vivo. MT-3724 was tested for safety in healthy NHPs: 6 intravenous (IV) doses of MT-3724 were given over 12 days at doses of 50, 150, and 450 mcg/kg. There were no deaths or effects on serum chemistries in the NHP studies. The major observed toxicity (inappetence) resolved within 48 hours of last dose. There was a significant, dose-dependent NHP B-cell depletion by Day 3 at all doses. Given the preclinical activity and mechanism of action, a Phase I/Ib study of MT-3724 was initiated in NHL. Methods MT-3724 is being tested for safety and tolerability in a first-in-human, open label, ascending dose study (3 + 3 design) in sequential cohorts of 5, 10, 20 and 50 mcg/kg/dose. Eligible subjects who previously responded to a CD20 MAb containing therapy followed by relapse/recurrence of NHL receive 6 doses by 2 hour IV infusions over the first 12 days of a 28 day cycle (first cycle). With continued safety, tolerability and lack of tumor progression, subjects may receive up to 4 additional 6-dose cycles (21 days) with tumor assessments after cycles 2, 4 and 5. Dose escalation is based on < 33% dose limiting toxicities (DLTs) observed during the first 28 day cycle. Results Three NHL subjects (2 transformed DLBCL, 1 FL) have completed at least one cycle in the 5 mcg/kg/dose cohort with no protocol DLTs or infusion related reactions and are evaluable for safety. Non-DLTs included grade (Gr) 2-3 transient hyperglycemic episodes related to pre-infusion corticosteroid therapy (n=1); transient Gr 4 neutropenia, possibly related to MT-3724 during cycle 1, week 4 (n=1); Gr 4 hypercalcemia and acute kidney injury with Gr 3 hypophosphatemia during cycle 1, week 4 due to leukemic disease progression (n=1). Subject 1 completed 5 cycles of therapy, with a partial response achieved post cycle 2 sustained through cycle 5; Subject 3 had a mixed response (both subjects had transformed DLBCL). Three subjects have now initiated treatment in the 10 mcg/kg/dose cohort with updated data to be presented at the meeting. Conclusions MT-3724 at 5 mcg/kg/dose has been safely administered for up to 5 cycles in this first-in-human study in relapsed/refractory NHL subjects. Treatment with the 10 mcg/kg cohort has commenced with continuing dose ascension planned. There is early evidence of clinical activity. Disclosures Diefenbach: Gilead: Equity Ownership, Research Funding, Speakers Bureau; Jannsen Oncology: Consultancy; Idera: Consultancy; Immunogen: Consultancy; Incyte: Research Funding; Genentech: Research Funding; Celgene: Consultancy; Molecular Templates: Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding. Valacer:Molecular Templates: Employment. Higgins:Molecular Templates: Employment. Fanale:Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Honoraria, Research Funding; Infinity: Membership on an entity's Board of Directors or advisory committees; Spectrum: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Honoraria, Research Funding; Genentech: Research Funding; Medimmune: Research Funding; Novartis: Research Funding; Bayer: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Molecular Templates: Research Funding; ADC Therapeutics: Research Funding; Onyx: Research Funding; Gilead: Research Funding.

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Bone Marrow Hematopoietic Dysfunction in Untreated Chronic Lymphocytic Leukemia Is Partially Mediated By Exposure to Constituents of the Leukemic Microenvironment

Blood ◽

10.1182/blood-2018-99-118916 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 3132-3132

Author(s):

Bryce Manso ◽

Kimberly Gwin ◽

Charla R Secreto ◽

Henan Zhang ◽

Wei Ding ◽

...

Keyword(s):

Bone Marrow ◽

B Cells ◽

Chronic Lymphocytic Leukemia ◽

Board Of Directors ◽

Research Funding ◽

Lymphocytic Leukemia ◽

Healthy Controls ◽

Advisory Committees ◽

The Impact

Abstract Peripheral immune dysfunction in B-Chronic Lymphocytic Leukemia (CLL) is well-studied and likely relates to the incidence of serious recurrent infections and second malignancies that plague CLL patients. However, the current paradigms of known immune abnormalities are not able to consistently explain these complications and it is not easy to correct CLL patient immune status. Here, we expand on our preliminary reports that demonstrate bone marrow (BM) hematopoietic dysfunction in early and late stage untreated CLL patients. We found reduced short-term functional capacity of hematopoietic progenitors in BM using colony forming unit assays (Figure 1A-C) and flow cytometry revealed significant reductions in frequencies of hematopoietic stem and progenitor cell (HSPC) populations (exemplified by Lin-CD34+ HSPCs, Figure 1D). We further report that protein levels of the transcriptional regulators HIF-1α, GATA-1, PU.1, and GATA-2 are overexpressed in distinct HSPC subsets from CLL patient BM, providing molecular insight into the basis of HSPC dysfunction. Interestingly, sustained myelopoiesis, evaluated by limiting dilution analysis in long-term culture-initiating cell (LTC-IC) assays maintained for five weeks, revealed no difference between healthy controls and CLL patients. These new data indicate that when HSPCs are removed from the leukemic microenvironment for ample in vitro culture time, they recover the ability to sustain myelopoiesis. To further assess the impact of the CLL microenvironment on HSPC biology, isolated HSPCs (CD34+ BM cells) from healthy controls were exposed in vitro to known leukemic microenvironment constituents. Exposure to TNFα, a cytokine constitutively produced by CLL B cells, resulted in rapid increases in PU.1 and GATA-2 proteins (Figure 2A-D). Similarly, addition of TNFα to the LTC-IC assay resulted in a striking ablation of myelopoiesis, even at the highest input cell concentration. Further, overexpression of PU.1 and GATA-2 were observed in HSPCs following co-culture with CLL B cells, a result that was not recapitulated when cells were exposed to IL-10, another cytokine constitutively produced by CLL B cells. These findings indicate specific components of the leukemic microenvironment are involved in HSPC modulation. Together, these findings expand on our previous observations of BM hematopoietic dysfunction in untreated CLL patients and offer new molecular insights into the contribution of the leukemic microenvironment on immunodeficiency in CLL. Disclosures Ding: Merck: Research Funding. Parikh:Pharmacyclics: Honoraria, Research Funding; MorphoSys: Research Funding; Janssen: Research Funding; Abbvie: Honoraria, Research Funding; Gilead: Honoraria; AstraZeneca: Honoraria, Research Funding. Kay:Morpho-sys: Membership on an entity's Board of Directors or advisory committees; Agios Pharm: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Acerta: Research Funding; Infinity Pharm: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Tolero Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Cytomx Therapeutics: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding.

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Blockade of IL-15 Utilizing Bnz-1, a Selective γ-Chain Inhibiting Peptide, Is Safe and Has Clinical Activity in Patients with T-Cell Large Granular Lymphocytic Leukemia (T-LGLL): Results of a Phase I/II Multi-Center Clinical Trial

Blood ◽

10.1182/blood-2019-129291 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 2835-2835 ◽

Cited By ~ 1

Author(s):

Jonathan E. Brammer ◽

Lubomir Sokol ◽

Yutaka Tagaya ◽

Kerry Rogers ◽

Anjali Mishra ◽

...

Keyword(s):

Clinical Trial ◽

T Cell ◽

Phase I ◽

Board Of Directors ◽

Dose Escalation ◽

Research Funding ◽

Lymphocytic Leukemia ◽

Weekly Dose ◽

Advisory Committees ◽

Large Granular Lymphocytic Leukemia

T-cell large granular lymphocytic leukemia (T-LGLL) is an incurable, and likely under-diagnosed leukemia characterized by abnormal clonal proliferation of CD8+ memory T-cells. The clonal outgrowth of T-LGLL cells can lead to the development of profound neutropenia and anemia which results in frequent infections, transfusion dependence, and impairment in quality of life and lifespan. There have been few prospective clinical trials in this disease, and no drugs have been FDA approved for its treatment. The primary driver of leukemogenesis in T-LGLL is known to be interleukin-15 (IL-15), a gamma-chain cytokine that induces proliferation of T-LGLL cells. BNZ-1 is a novel pegylated peptide antagonist that inhibits IL-15 by binding to the common γ-chain receptor for cytokines IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21. Studies utilizing BNZ-1 in vitro on T-LGLL cell lines, and ex vivo on clinical patient samples demonstrated significant inhibition of downstream signaling and increased LGLL cell apoptosis (Wang et al., Leukemia 2018). Given these results, we conducted a phase I/II dose escalation study to evaluate the safety, maximum tolerated dose (MTD), and preliminary efficacy of BNZ-1 in T-LGLL (NCT03239393). Patients with T-LGLL were eligible if they had one or more of the following: absolute neutrophil count (ANC) <500 cells/m3, neutropenia with recurrent infections, or symptomatic or transfusion-dependent anemia. Diagnosis of T-LGLL required: >400/mm3 CD3+CD57+ cells or >650 mm3 CD8+ cells, with a clonal T-cell receptor rearrangement. No prior therapy within 30 days or 5 half-lives was permitted. MTD was evaluated using a standard 3+3 design; with a dose escalation strategy using four doses of BNZ-1: 0.5 mg/kg, 1 mg/kg, 2 mg/kg, and 4 mg/kg. BNZ-1 was administered by infusion on Days 1, 8, 15, and 22 of a 4-week cycle. Patients then had the option to enter the 3-month extension period, at the same weekly dose. Efficacy was determined utilizing criteria from the ECOG5998 study in T-LGLL. CR was defined as complete normalization of blood counts. Partial response (PR) in neutropenic patients was determined by 4 weeks or greater response with ANC >500 cells/mm3 if >/=50% improvement from baseline. For transfusion-dependent anemia patients, a >/=50% decrease in monthly transfusions for at least 2 months was required for a PR. For patients with symptomatic anemia, improvement in hemoglobin >/=1 g/dL with improvement in symptoms constituted a PR. Patients with a response were permitted to remain on a long-term extension (LTE). Eighteen patients, at 3 US centers were enrolled on study including: 3 patients at 0.5 mg/kg, 4 at 1 mg/kg, 5 at 2 mg/kg, and 6 at 4 mg/kg. 10 patients were enrolled for neutropenia, 4 for transfusion dependent anemia, 2 for symptomatic anemia, and 2 with anemia and neutropenia. 15 patients (83%) completed all 16 weeks of treatment, 2 patients declined to enter the extension phase, and one patient on the 2 mg/kg dosage was taken off study at 4 weeks due to neutropenia <100 thought secondary to T-LGLL. One patient developed grade 2 hyperbilirubinemia, which was thought possibly due to study drug though was grade 1 at baseline.The MTD was not reached. Four patients attained a PR: 3 patients with transfusion-dependent anemia became transfusion independent, while one patient with neutropenia had significant resolution of her neutropenia (Table). These three patients remain on the LTE, though one patient is under observation. Correlative studies demonstrated apoptosis of T-LGLL cells on flow cytometry utilizing CD3 T-cell gating within 24 hours of the first dosage of BNZ-1 (a representative example is shown in the Figure), confirming in patients that inhibition of IL-15 induces apoptosis of T-LGLL cells. In this Phase I/II clinical trial, IL-15 blockade utilizing BNZ-1 demonstrated increased apoptosis in patients with T-LGLL, with early evidence of clinical response, particularly amongst patients with transfusion-dependent anemia. Remarkably, these patients remained transfusion-independent while on BNZ-1. The MTD was not reached in this cohort of patients, and there were minimal AEs associated with BNZ-1. Further analysis of responding patients is underway to determine the most effective approach utilizing BNZ-1 in this rare disease. Table Disclosures Brammer: Celgene: Research Funding; Seatlle Genetics: Honoraria, Speakers Bureau. Sokol:EUSA: Consultancy. Tagaya:Bioniz: Membership on an entity's Board of Directors or advisory committees; Bioniz: Research Funding. Rogers:AbbVie: Research Funding; Acerta Pharma: Consultancy; Genentech: Research Funding; Janssen: Research Funding. Waldmann:Bioniz: Membership on an entity's Board of Directors or advisory committees. Azimi:Bioniz: Employment. Frohna:Bioniz: Employment. Ratnayake:Bioniz: Employment. Loughran:Bioniz: Membership on an entity's Board of Directors or advisory committees; Keystone Nano: Membership on an entity's Board of Directors or advisory committees.

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The Green Tea Extract EGCG Demonstrates Synergist Activity against CLL B-Cells When Combined with Fludarabine and Chlorambucil.

Blood ◽

10.1182/blood.v114.22.3452.3452 ◽

2009 ◽

Vol 114 (22) ◽

pp. 3452-3452 ◽

Cited By ~ 1

Author(s):

Connie Lesnick ◽

Neil E. Kay ◽

Betsy LaPlant ◽

Tait D. Shanafelt

Keyword(s):

B Cells ◽

Synergistic Effect ◽

Phase I ◽

Board Of Directors ◽

Research Funding ◽

Fixed Dose ◽

Advisory Committees ◽

Purine Analogue

Abstract Abstract 3452 Poster Board III-340 PURPOSE Chronic Lymphocytic Leukemia (CLL) is incurable with current chemotherapy treatments. Epigallocatechin 3 gallate (EGCG), the major catechin in green tea, has been shown to induced caspase-dependent death CLL B-cells and down regulate anti-apoptotic proteins (Mcl-1; XIAP) known to increase the resistance of CLL B-cells to apoptosis (Blood 104:788-94). In Phase I testing for patients with early stage CLL (Rai 0-II), EGCG treatment was well tolerated and induced a decline in absolute lymphocyte count (ALC) and/or lymphadenopathy in the majority of treated patients without myelosuppression (JCO 27:3808-14). Although peak plasma EGCG levels were not measured in this study, trough plasma EGCG levels as high as 4 μg/ML were achieved. To further our understanding of the potential clinical applications of EGCG for patients with CLL, we evaluated the effects of EGCG on the viability of CLL B-cells when combined with fludarabine (F), chlorambucil (C), or fludarabine and chlorambucil in combination (FC). METHODS Primary CLL B-cells were treated with various doses of F (0.25-1 μM), C (10-30 μM), or FC either alone or in combination EGCG (50 to 100 μM). In other experiments, CLL B-cells were treated with various doses of F (0.25-1 μM), C (10-30 μM), or FC with or without a fixed dose of EGCG known to be physiologically achievable in vivo (4 μM). After 48 hours (experiments with C +/− EGCG) or 72 hours (experiments with F +/− EGCG or FC +/− EGCG), cells were harvested, stained with annexin/PI and viability analyzed by flow cytometry. After concentration-effect curves were generated for each agent, data were also analyzed using the CalcuSyn software program (Biosoft, Cambridge, UK) which uses the method of Chou and Talalay to determine whether combination treatment yielded greater effects than expected from summation alone. A combination index (CI) of 0.8 – 1.2 indicates an additive effect, a CI >1.2 indicates an antagonistic effect and a CI <0.8 indicates a synergistic effect. RESULTS Primary leukemic B-cells from 56 CLL patients were cultured in vitro with various doses of EGCG alone or in combination with F, C, or FC. The median LD50 was approximately 100 μM. Although % apoptotic cells at the 100 μM EGCG dose did not vary based on Rai stage, ZAP-70 status, IGHV gene mutation status, or cytogenetic abnormalities by FISH, CD38 negative patients had greater cell death than CD38 positive patients (67% vs. 49%; p=0.05). In co-titration experiments, EGCG had an additive (CI 0.8 – 1.2) or synergistic (CI <0.8) effect on apoptosis when combined with C in the majority of patients (13/15; additive 11, synergism 2) with rare individuals demonstrating antagonism (CI >1.2; 2/15). The effects of EGCG when combined with F in co-titration experiments were more variable with a relatively even distribution between antagonism (8/18), additive effects (4/18), and synergy (6/18). However, co-titration experiments of FC with or without EGCG demonstrated additive or synergistic effect in most patients (8/10; additive 7, synergism 1). Next we evaluated the effect of F (0.25 - 1 μM), C (10 - 30 μM), or FC with or without a fixed dose of EGCG known to be physiologically achievable in vivo (4 μM). This dose of EGCG had an additive or synergistic effect in the majority of samples across the spectrum of dose levels under all 3 conditions (F, C, and FC). For example, at the 10 μM dose of C the addition of 4 μM EGCG had an additive or synergistic effect in 11/14 patients (synergistic 6; additive 5). With F at the 2.5 μM dose level the addition of 4 μM EGCG had an additive or synergistic effect in 13/16 patients (synergistic 7, additive 6). The addition of 4 μM EGCG appeared particularly beneficial when given in combination with FC (Fig.). For example, at F 2.5 μM in combination with C 5 μM the addition of 4 μM EGCG had an additive or synergistic effect in 10/10 patients (synergism 7; additive 3). CONCLUSIONS Physiologically achievable doses of EGCG appear to enhance the efficacy of alkylating agents, purine nucleoside analogues, and alkylating agent/purine analogue combination therapy for the majority of CLL patients on in vitro testing. The favorable toxicity profile of EGCG and lack of myelosuppression with this agent in the phase I trial (JCO 27:3808-14) make it an attractive agent to test in combination with purine analogue and alkylator based chemo-immunotherapy for patients with CLL. Disclosures Kay: Genentech, Celgene, Hospira, Polyphenon Pharma, Sanofi-Aventis: Research Funding; Biogenc-Idec, Celgene, Genentech, genmab: Membership on an entity's Board of Directors or advisory committees. Shanafelt:Genentech: Research Funding; Hospira: Membership on an entity's Board of Directors or advisory committees, Research Funding; Polyphenon Pharma : Patents & Royalties, Research Funding; Celgene: Research Funding; Cephalon: Research Funding; Bayer Health Care Pharmaceuticals: Research Funding.

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Axl Regulates Fibroblast Growth Factor Receptor Signaling in B-Cell Chronic Lymphocytic Leukemia: Dual Targeting in CLL Therapy

Blood ◽

10.1182/blood.v124.21.831.831 ◽

2014 ◽

Vol 124 (21) ◽

pp. 831-831

Author(s):

Sutapa Sinha ◽

Justin Boysen ◽

Charla Secreto ◽

Steven L. Warner ◽

Neil E. Kay ◽

...

Keyword(s):

B Cells ◽

B Cell ◽

Board Of Directors ◽

Research Funding ◽

Lymphocytic Leukemia ◽

Advisory Committees ◽

High Affinity ◽

Fgfr Signaling ◽

Cell Chronic Lymphocytic Leukemia

Abstract B-cell chronic lymphocytic leukemia (CLL) is an incurable disease and represents a significant health problem in the western world. We and others have reported that primary CLL B-cells spontaneously produce increased levels of proangiogenic basic fibroblast growth factor (bFGF) in vitro and that most CLL plasma contains elevated levels of bFGF. However, the precise role of bFGF in CLL pathobiology is not clearly understood. In this study we investigated the functional implication of the FGF/FGF receptor (FGFR) signaling axis in CLL B-cell biology. We have detected expression of FGFR1 and FGFR3 with comparatively higher levels of the latter receptor tyrosine kinase (RTK), but no or notably low levels of FGFR2/FGFR4, by flow cytometry and Western blot analyses in primary CLL B-cells. This observation was further supported by detection of FGFR1/FGFR3 transcripts in CLL B-cells by semi-quantitative reverse transcriptase polymerase chain reaction. Although both FGFR1 and FGFR3 in CLL B-cells remain as constitutively phosphorylated, we found significantly higher levels of phosphorylation on FGFR3 and thus this latter receptor is likely the predominant RTK of the FGFR family in these leukemic B-cells. Of note, in vitro stimulation of FGFRs with recombinant bFGF was unable to increase total phosphorylation on FGFRs from their constitutive basal levels in CLL B-cells. Further analysis using a bFGF neutralizing antibody suggested that FGFR phosphorylation in CLL B-cells is likely independent of bFGF ligation. We then interrogated the mechanism of how FGFRs were being phosphorylated and/or maintained at the observed constitutive levels of phosphorylation in CLL B-cells. Our previous studies established that Axl is a critical RTK in CLL B-cells since it acts as a docking site for multiple cellular kinases/lipase, an observation supported by earlier literatures in human malignancies. Given this, Axl is likely capable of cross talk with other RTKs including FGFRs to regulate FGFR-signaling in CLL B-cells. Therefore, in an effort to determine whether Axl is functionally associated with FGFR, we examined if these two RTKs exist in the same molecular complex in CLL B-cells. Indeed, immunoprecipitation assays demonstrated that Axl formed a complex with FGFR3 in CLL B-cells, suggesting that Axl is likely functionally linked to the FGFR signaling. In this regard we found that Axl inhibition, using a high-affinity Axl inhibitor (TP-0903; Tolero Pharmaceuticals), resulted in significant reduction of total FGFR phosphorylation in CLL B-cells. Additionally, siRNA-mediated partial depletion of Axl in CLL B-cells reduced total FGFR phosphorylation. In contrast, inhibition of FGFR phosphorylation using a high-affinity FGFR inhibitor could not alter phosphorylation levels on Axl RTK in CLL B-cells. Together, these findings suggest that Axl has a dominant role in the regulation of FGFR signaling in CLL B-cells. To find out if inhibition of FGFR can induce apoptosis in CLL B-cells we used a specific inhibitor for FGFR (TKI-258; Novartis) to treat CLL B-cells. Here we found a substantial level of apoptosis induction in the leukemic B-cells with a mean LD50 dose of ~2.5 μM. Interestingly, Axl inhibition by TP-0903 induced a robust level of apoptosis in CLL B-cells in the nanomolar dose range with a mean LD50 dose of 0.14 mM. Thus Axl inhibition exerts a very robust cytotoxic effect on CLL B-cell survival likely targeting both Axl and FGFR signaling pathways via Axl inhibition. In conclusion, we have detected expression of constitutively active FGFR1 and 3 in primary CLL B-cells and that inhibition of FGFR signaling induces considerable levels of CLL B-cell apoptosis albeit lower than that observed on Axl RTK inhibition. Interestingly, our findings here suggest that Axl forms an active RTK complex with FGFR and that Axl inhibition modifies FGFR phosphorylation levels. Thus it is likely that Axl RTK can regulate FGFR signaling in the CLL B-cells. In total these observations suggest that the finding of robust induction of apoptosis in CLL B-cells is as a result of targeting two signaling pathways with Axl inhibition: Axl and FGFR. These studies further support investigation of Axl inhibition as a way to develop a more effective and efficient therapeutic intervention for CLL patients. Disclosures Warner: Tolero Pharmaceuticals: Employment, Equity Ownership, Patents & Royalties. Kay:Genetech: Research Funding; Pharmacyclics: Research Funding; Hospira: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees.

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Comparative in Vitro Cellular Data Alone Is Insufficient to Predict Clinical Responses and Guide Choice of BCR-ABL Inhibitor to Treat Imatinib-Resistant Chronic Myeloid Leukemia.

Blood ◽

10.1182/blood.v114.22.510.510 ◽

2009 ◽

Vol 114 (22) ◽

pp. 510-510 ◽

Cited By ~ 1

Author(s):

Pierre Laneuville ◽

Clifford DiLea ◽

Jürgen Mestan ◽

Ophelia Yin ◽

Richard C. Woodman ◽

...

Keyword(s):

Research Funding ◽

Systemic Exposure ◽

Clinical Factors ◽

Advisory Committees ◽

Exposure Data ◽

Imatinib Resistant ◽

Clinical Responses ◽

Selection Of

Abstract Abstract 510 Background: Recently, Redaelli et al (J Clin Oncol. 2009;27:469) compared the in vitro inhibitory activity of imatinib, dasatinib, nilotinib, and bosutinib against 18 mutant forms of BCR-ABL (expressed in transfected Ba/F3 cells) associated with imatinib resistance and proposed a chart to assist in the selection of second-generation tyrosine kinase inhibitors (2TKIs) for the treatment of imatinib-resistant CML associated with mutations. However, the predictability of this chart has neither been clinically evaluated nor does it take into account other important clinical factors (e.g. pharmacokinetics (PK)/pharmacodynamics) that may impact response rates to 2TKIs in the presence of mutations. The purpose was to assess the impact of 2TKIs' in vivo plasma levels on the in vitro GI50 data, and to determine if in vitro GI50 data with or without plasma levels correlates with observed clinical responses in imatinib-resistant patients (pts) with mutations. Methods: To enable appropriate comparison of the activity of 2TKIs against specific mutations we modified the original in vitro GI50 data by adjusting it to include an estimate of in vivo Cmax exposure data for each 2TKI. Further refinement was achieved by calculating the Cmax/GI50 values for each agent and normalizing these against imatinib vs wild-type BCR-ABL. To assess the correlation between patient response and in vitro GI50 data, the previously published CCyR rates for pts with specific mutations were plotted according to in vitro GI50 values alone and against the adjusted Cmax/GI50 values. Results: The adjusted Cmax/GI50 data suggest that nilotinib delivers the most potent inhibition of most BCR-ABL mutations in vivo, with dasatinib being the next most potent. However, when either in vitro GI50 data alone or the modified Cmax/GI50 data are considered, there is poor correlation of clinical responses to both nilotinib and dasatinib against several of the mutations in vivo (Figure). Overall, activity of 2TKIs against all mutations was less than expected based on original in vitro GI50 or Cmax/GI50 calculations of systemic exposure. For example, the G250E mutation has similar systemic exposure to nilotinib as the F359V mutation as indicated by Cmax/GI50, but substantial differences are observed in the CCyR rate (60% vs 0%). For dasatinib, the same was observed for the F317L and L248V mutations which have similar exposures to dasatinib but have different CCyR rates (7% vs 41%). Similarly, several mutations with comparable exposure to nilotinib and dasatinib had substantial differences in CCyR rates, suggesting that other factors were influencing responses. For example, the G250E mutation was considered moderately sensitive to both nilotinib and dasatinib based on the adjusted Cmax/GI50; however, CCyR rates on nilotinib were much higher (60%) compared with dasatinib (34%). Similarly, the E255K mutation was considered moderately sensitive to both agents based on the adjusted Cmax/GI50; however, CCyR rates on dasatinib were much higher (38%) compared with nilotinib (13%). Conclusions: This analysis illustrates the limitations of in vitro inhibition data alone or in combination with PK exposure data in the selection of 2TKI therapy for imatinib-resistant pts with mutations. The current analysis still does not consider parameters such as protein binding and intracellular influx/efflux, among a variety of other clinical factors that could further influence response rates. This tool is also not useful for pts with mutations of unknown in vitro sensitivity, which may represent 15% of all pts with mutations. Currently, clinical responses remain the best approach for selection of 2TKIs in pts with mutations, with only a small subset of mutations having low sensitivity mutations existing for each 2TKI. Other factors, such as patient medical history, comorbidities, and the agents' safety profiles, are also important in selection of 2TKIs. Disclosures: Laneuville: Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Wyeth: Research Funding; ChemGenex: Research Funding. DiLea:Novartis: Employment. Mestan:Novartis: Employment. Yin:Novartis: Employment, Equity Ownership. Woodman:Novartis: Employment. Manley:Novartis: Employment.

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Expression of Sf3b1-K700E accelerates the Development of Chronic Lymphocytic Leukemia in a Del(13q) Murine Model

Blood ◽

10.1182/blood-2020-139096 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 4-5

Author(s):

Bo Zhang ◽

Prajish Iyer ◽

Meiling Jin ◽

Elisa Ten Hacken ◽

Zachary Cartun ◽

...

Keyword(s):

B Cells ◽

Board Of Directors ◽

Murine Model ◽

Rna Splicing ◽

Research Funding ◽

Lymphocytic Leukemia ◽

Advisory Committees ◽

Nsg Mice ◽

Mtorc1 Pathway

RNA splicing factor SF3B1 is one of the most recurrently mutated genes in chronic lymphocytic leukemia (CLL), but expression of this mutation alone in murine B cells does not result in CLL. This gene mutation is often subclonal and associated with poor survival. How this mutation impacts CLL progression remains elusive. Since SF3B1 mutation frequently co-occurs with chromosome 13q deletion (del(13q)), and mice with deletion of the Minimal Deleted Region (MDR) of del(13q) develop indolent CLL, we therefore asked whether co-expression of Sf3b1 mutation can accelerate the onset of CLL in this murine model. If so, how does Sf3b1 mutation mechanistically contribute to CLL. To this end, we first crossed mice carrying conditional knock in allele Sf3b1-K700E and mice with conditional knockout of MDR. We then bred the offspring with CD19-Cre mice to generate cohorts of mice which have B cell-specific homozygous deletion of MDR with (DM) or without (MDR-MT) heterozygous Sf3b1-K700E. We monitored the onset of CLL by tracking of circulating B220+CD5+ CLL-like cells from peripheral blood with flow cytometry, starting at the age of 6-months and ending by 24-months. We detected CLL-like disease in 24% (6 of 25) of DM and 7.4% (2 of 27) of MDR-MT mice with disease presence in the spleen, bone marrow and lymph node, confirmed by flow cytometry and immunohistochemistry. The increased frequency of CLL in DM mice indicated that Sf3b1-K700E could accelerate CLL (Pearson Chi-Square 2-sided, p=0.098). To elucidate how Sf3b1 mutation contributes to increased CLL penetrance, we performed integrated RNA sequencing (RNA-seq) and TMT proteomics analysis with splenic B cells derived from DM mice with and without CLL. We found that genes involved in MYC, cell cycle checkpoints and mTORC1 pathways are upregulated and enriched at both the RNA and protein levels when we compared DM-CLL cells to their DM B cell counterparts, indicating these cellular processes are involved in the onset of CLL. To further define the role of Sf3b1-K700E mediated alternative splicing in the activation of these pathways, we first identified candidate splicing isoforms (nfatc1, braf, depdc5, tsc2) through computational analysis of RNA-seq data and then validated the isoforms in an independent cohort of samples (n=3,). Functional annotation of how exactly these isoforms impact CLL is ongoing. Importantly, we also observed gene upregulation of mTORC1 pathway in human CLL cells with SF3B1 mutation and del(13q) when compared with normal B cells. We next asked whether DM CLL cells are sensitive to inhibition of mTORC1 pathway and RNA splicing inhibition in vitro. We exposed DM B and CLL cells to either Temsirolimus (Tem, mTORC1 inhibitor), or H3B8800 (H3B, SF3B1 inhibitor) alone or in combination for 24 hours and then measured the cell viability with CellTiter-Glo assay. When compared to DMSO control, both Tem and H3B single treatments significantly inhibited the survival of DM CLL cells, but not DM B cells (all groups vs control, unpaired t test, p<0.01). Furthermore, an additive effect was observed in DM CLL cells when 1nM of H3B was combined with Tem treatment (IC50: 1.2nM vs. 135.2uM, unpaired t test p<0.001). We then tested the effects of both drugs in vivo using NSG mice engrafted with DM CLL cells. Mice treated with combination of Tem (15mg/kg, i.p, 5 days) and H3B (4mg/kg, gavage, 5 days) had a lower CLL burden in peripheral blood in comparison to either the single treatment or no drug treatment group (all groups vs. comb, p≤0.001). Furthermore, the combination treatment increased the survival of NSG mice engrafted with CLL cells compared to control (median survival: control vs. comb 15 vs. 34 days, log rank p<0.001). Importantly, when we exposed human CLL cells with both del(13q) and sf3b1 mutation (DM-CLL, n=3), or with del(13q) alone (n=2), or normal B cells (n=4) to the combination treatment in vitro, DM-CLL cells showed the highest sensitivity to the treatment (DM-CLL vs. all groups, p<0.05), suggesting that SF3B1 mutation may accelerate CLL with del(13q) through modulating RNA splicing and mTORC1 pathway. Our study demonstrates that expression of Sf3b1-K700E could accelerate the development of CLL based on MDR deleted murine model through alternative RNA splicing and mTORC1 activation. This finding supports the use of an mTORC1 inhibitor together with RNA splicing inhibitor in the subset of CLL patients with both SF3B1 mutation and del(13q). Disclosures Kipps: Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genentech/Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Honoraria, Research Funding; Ascerta/AstraZeneca, Celgene, Genentech/F. Hoffmann-La Roche, Gilead, Janssen, Loxo Oncology, Octernal Therapeutics, Pharmacyclics/AbbVie, TG Therapeutics, VelosBio, and Verastem: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics/ AbbVie, Breast Cancer Research Foundation, MD Anderson Cancer Center, Oncternal Therapeutics, Inc., Specialized Center of Research (SCOR) - The Leukemia and Lymphoma Society (LLS), California Institute for Regenerative Medicine (CIRM): Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; VelosBio: Research Funding; Oncternal Therapeutics, Inc.: Other: Cirmtuzumab was developed by Thomas J. Kipps in the Thomas J. Kipps laboratory and licensed by the University of California to Oncternal Therapeutics, Inc., which provided stock options and research funding to the Thomas J. Kipps laboratory, Research Funding. Neuberg:Celgene: Research Funding; Madrigak Pharmaceuticals: Current equity holder in publicly-traded company; Pharmacyclics: Research Funding. Wu:BionTech: Current equity holder in publicly-traded company; Pharmacyclics: Research Funding.

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Combinations of the Phosphatidylinositol 3-Kinase-Delta (PI3Kδ) Inhibitor Gs-1101 (CAL-101) with Rituximab and/or Bendamustine Are Tolerable and Highly Active in Previously Treated, Indolent Non-Hodgkin Lymphoma: Results From a Phase I Study

Blood ◽

10.1182/blood.v120.21.3645.3645 ◽

2012 ◽

Vol 120 (21) ◽

pp. 3645-3645 ◽

Cited By ~ 2

Author(s):

Nathan H Fowler ◽

Sven de Vos ◽

Marshall T. Schreeder ◽

John P. Leonard ◽

Ian W. Flinn ◽

...

Keyword(s):

Phase I ◽

Board Of Directors ◽

Research Funding ◽

Phase 1 ◽

Single Agent ◽

Progression Free Survival ◽

Tumor Control ◽

Advisory Committees ◽

Heavily Pretreated ◽

Previously Treated

Abstract Abstract 3645 Introduction: PI3Kδ drives proliferation and survival in malignant B-cells. GS-1101 is an orally bioavailable, small-molecule inhibitor of PI3Kδ that has shown considerable monotherapy activity when given at dose levels of ≥100 mg BID in patients with heavily pretreated indolent non-Hodgkins lymphoma (iNHL). Methods and Patients: This Phase 1 combination study has evaluated repeated 28-day cycles of GS-1101 with rituximab and/or bendamustine in patients with previously treated iNHL. GS-1101 was administered starting on Day 1 of Cycle 1 with rituximab (R) (375 mg/m2 given weekly for 8 doses) (GS-1101/R regimen), with bendamustine (B) (90 mg/m2 given on Days 1 and 2 of each cycle for 6 cycles) (GS-1101/B regimen), or in combination with R (375 mg/m2, on Day 1 of each cycle for 6 cycles) and B (90 mg/m2 given on Days 1 and 2 of each cycle for 6 cycles (GS-1101/BR regimen). Initial cohorts received a GS-1101 dose of 100 mg/dose BID. Thereafter, all patients received a GS-1101 dose of 150 mg/dose BID. Tumor response was evaluated according to standard criteria (Cheson 2007). Chemokine/cytokine plasma levels were assessed at baseline and on Day 28 of therapy using multiplexed bead suspension arrays. Results: The study enrolled 76 patients with iNHL. Patient characteristics, histological sub-typing, safety, and efficacy results are depicted in the table. The majority of patients were >60 years of age and had undergone extensive prior therapy. Grade ≥3 adverse events and lab abnormalities were generally consistent with those expected with each of the single agents. Lymph node shrinkage was rapid and all evaluable patients had reductions in lymphadenopathy, resulting in overall response rates (ORR) of 77%, 85%, and 77% for the GS-1101/R, GS-1101/B, and GS-1101/BR regimens, respectively. Complete responses (with bone marrow confirmation) were observed in 13%, 16%, and 30% of patients. With median follow-up duration ranging from 28 to 48 weeks, 1-year progression- free survival (PFS) rates were >75% in all treatment groups. Disease-associated chemokines/cytokines were commonly elevated at baseline and were significantly reduced by GS-1101-based combination treatment. Conclusions: A lack of overlapping toxicities allows the oral PI3Kδ inhibitor, GS-1101, to be delivered at the full single-agent starting dose when coadministered with chemoimmunotherapies in heavily pretreated patients with iNHL. GS-1101-based combination therapy with rituximab and/or bendamustine offers major and rapid reductions in lymphadenopathy. All 3 regimens provide durable tumor control. The data from this trial support the development of Phase 3 combination trials of GS-1101 with rituximab- and/or bendamustine-containing regimens in patients with iNHL. Disclosures: Fowler: Gilead Sciences: Membership on an entity's Board of Directors or advisory committees. Off Label Use: Phase I trial of GS-1101, a PI3K delta inhibitor, in B cell malignancies. de Vos:Gilead Sciences: Membership on an entity's Board of Directors or advisory committees. Schreeder:Gilead Sciences: Research Funding. Leonard:Gilead: Consultancy. Coutre:Gilead Sciences: Membership on an entity's Board of Directors or advisory committees. Sharman:Gilead: Honoraria, Research Funding. Boccia:Gilead Sciences: Research Funding. Barrientos:Gilead Sciences: Research Funding. Holes:Gilead: Employment. Lannutti:Gilead Sciences Inc: Employment. Johnson:Gilead Sciences: Employment. Jahn:Gilead: Employment. Miller:Gilead: Employment. Godfrey:Gilead Sciences: Employment.

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