PARP Inhibition with Talazoparib Enhances DNA Damage and Anti-Leukemic Activity of Venetoclax in Preclinical Human Acute Myeloid Leukemia (AML) Models

Abstract Background: BCL-2 is an anti-apoptotic protein associated with chemotherapy resistance and survival of acute myeloid leukemia (AML) cells following cell stress or DNA damage. Venetoclax (Ven) is a BH3-mimetic that competitively binds to BCL-2, allowing BH3 proteins to bind to pro-apoptotic proteins (BAX, BAK) and induce cell death. The combination of Ven with Azacitidine (Aza), is now standard of care therapy for older patients with AML. Poly (ADP-ribose) polymerase (PARP) inhibitors prevent the repair of single stranded DNA breaks by blocking the nicotinamide adenine dinucleotide (NAD) catalytic domain of the PARP protein and preventing dissociation of PARP from the DNA (termed PARP trapping). The PARP inhibitor, talazoparib (Tala) displays 10,000-fold increased PARP trapping as compared to other clinical PARP inhibitor agents in tumor models. We hypothesized that Tala could enhance the anti-leukemic activity of Ven on AML cells specifically by increasing DNA damage. Methods: Human AML (Molm13) cells were continuously exposed to increasing doses of Ven (1nM - 10mM), Tala (1nM - 10mM), and Aza (0.1-5mM) alone and in combination. Synergy reports were generated using CompuSyn software. Cell viability was measured using a WST colorimetric assay. Apoptosis (annexin /PI), DNA damage (pH2AX), and cell cycle arrest (propidium iodide) were quantified by flow cytometric analysis. DNA damage was also evaluated using the Fast-Halo assay. In vivo efficacy was assessed in NSG mice systematically engrafted with stably luciferase transfected Molm13 BLIV cells via tail vein injection. Cohorts of mice (5-10) were treated with vehicle, Ven (100 mg/kg given 5 days/week for 3 weeks), Tala (0.33 mg/kg for 5 days/week over 3 weeks), Ven + Tala (same doses), and Ven+ Aza (1.25 or 2.5 mg/kg daily for 7 days). Treatment effects on leukemia burden, toxicity, and overall survival were determined using weekly whole animal bioluminescent imaging, total animal weights, and time to morbidity, respectively. Results: Human AML cells treated with Ven displayed dose and time-dependent induction of DNA damage, apoptosis, and cell death. Similarly, treatment with single agent Tala resulted in dose-dependent anti-proliferative effects and PARP trapping. Combination in vitro therapy with Ven (0.1 - 1 μM) + Tala (10- 100 nM) or Ven (same doses) + Aza (1 μM) resulted in significant and synergistic anti-leukemic effects improving upon monotherapy with Ven, Tala, or Aza alone. However, in contrast to Ven+Aza, increased levels of DNA damage (as determined by phosphorylated H2AX and Fast Halo assays) were detected as well as induction of apoptosis, cell cycle arrest, decreased viability, and increased cell death vs vehicle and single agent therapy. We then evaluated the effects of in vivo treatment with vehicle, Ven, Tala, Ven + Tala, and Ven +Aza in NSG mice systemically engrafted with human luciferase-tagged AML cells (Molm13 BLIV). Single agent Ven or Tala therapy decreased systemic AML burden but did not prolong overall survival over vehicle treated mice. Combination Ven + Tala significantly prolonged overall survival of leukemia xenografted mice over vehicle, Ven, or Tala monotherapy. Of note, Ven + Tala treatment appeared to result in similar disease burden reduction and prolonged overall survival as Ven + Aza treated animals (Figure 1). Preliminary experiments of iv vivo triple therapy with Ven + Aza + Tala in AML xenografted mice resulted in further reduction in AML disease burden but was associated with marked weight loss leading to early morbidity and shortened overall survival (data not shown). Additional doses and schedules of this triplet approach are under investigation. Conclusions: Our results demonstrate that addition of the potent PARP inhibitor, talazoparib, to the BCL-2 inhibitor, venetoclax, enhances DNA damage and results in potent in vitro and in vivo activity in preclinical human AML models. Further evaluation of this combination in primary AML samples with varying genetic backgrounds as well as in confirmatory primary xenograft models is underway. These data strongly support future clinical investigation of PARP inhibitors as a novel class of agents with the potential to significantly enhance the efficacy of novel targeted therapies for acute leukemia. Figure 1 Figure 1. Disclosures Wang: BMS/Celgene: Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Other: Advisory Board, Speakers Bureau; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Consultancy, Honoraria, Other: Advisory Board; Mana Therapeutics: Consultancy, Honoraria; DAVA Oncology: Consultancy, Speakers Bureau; Takeda: Consultancy, Honoraria, Other: Advisory board; Stemline Therapeutics: Consultancy, Honoraria, Other: Advisory board, Speakers Bureau; Jazz Pharmaceuticals: Consultancy, Honoraria, Other: Advisory Board; Kite Pharmaceuticals: Consultancy, Honoraria, Other: Advisory Board; Kura Oncology: Consultancy, Honoraria, Other: Advisory board, steering committee, Speakers Bureau; Novartis: Consultancy, Honoraria, Other: Advisory Board; Rafael Pharmaceuticals: Other: Data safety monitoring committee; Gilead: Consultancy, Honoraria, Other: Advisory board; Daiichi Sankyo: Consultancy, Honoraria, Other: Advisory board; PTC Therapeutics: Consultancy, Honoraria, Other: Advisory board; Genentech: Consultancy; MacroGenics: Consultancy.

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Targeting Wnt/β-Catenin and BCL-2, Two Critical Survival Factors, Synergistically Induces Apoptosis in AML Via Rac1-Mediated MCL-1 Inhibition

Blood ◽

10.1182/blood-2018-99-118367 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 1442-1442

Author(s):

Xiangmeng Wang ◽

Po Yee Mak ◽

Wencai Ma ◽

Xiaoping Su ◽

Hong Mu ◽

...

Keyword(s):

Progenitor Cells ◽

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Single Agent ◽

Advisory Committees ◽

Equity Ownership ◽

Critical Survival

Abstract Wnt/β-catenin signaling regulates self-renewal and proliferation of AML cells and is critical in AML initiation and progression. Overexpression of β-catenin is associated with poor prognosis. We previously reported that inhibition of Wnt/β-catenin signaling by C-82, a selective inhibitor of β-catenin/CBP, exerts anti-leukemia activity and synergistically potentiates FLT3 inhibitors in FLT3-mutated AML cells and stem/progenitor cells in vitro and in vivo (Jiang X et al., Clin Cancer Res, 2018, 24:2417). BCL-2 is a critical survival factor for AML cells and stem/progenitor cells and ABT-199 (Venetoclax), a selective BCL-2 inhibitor, has shown clinical activity in various hematological malignancies. However, when used alone, its efficacy in AML is limited. We and others have reported that ABT-199 can induce drug resistance by upregulating MCL-1, another key survival protein for AML stem/progenitor cells (Pan R et al., Cancer Cell 2017, 32:748; Lin KH et al, Sci Rep. 2016, 6:27696). We performed RNA Microarrays in OCI-AML3 cells treated with C-82, ABT-199, or the combination and found that both C-82 and the combination downregulated multiple genes, including Rac1. It was recently reported that inhibition of Rac1 by the pharmacological Rac1 inhibitor ZINC69391 decreased MCL-1 expression in AML cell line HL-60 cells (Cabrera M et al, Oncotarget. 2017, 8:98509). We therefore hypothesized that inhibiting β-catenin by C-82 may potentiate BCL-2 inhibitor ABT-199 via downregulating Rac1/MCL-1. To investigate the effects of simultaneously targeting β-catenin and BCL-2, we treated AML cell lines and primary patient samples with C-82 and ABT-199 and found that inhibition of Wnt/β-catenin signaling significantly enhanced the potency of ABT-199 in AML cell lines, even when AML cells were co-cultured with mesenchymal stromal cells (MSCs). The combination of C-82 and ABT-199 also synergistically killed primary AML cells (P<0.001 vs control, C-82, and ABT-199) in 10 out of 11 samples (CI=0.394±0.063, n=10). This synergy was also shown when AML cells were co-cultured with MSCs (P<0.001 vs control, C-82, and ABT-199) in all 11 samples (CI=0.390±0.065, n=11). Importantly, the combination also synergistically killed CD34+ AML stem/progenitor cells cultured alone or co-cultured with MSCs. To examine the effect of C-82 and ABT-199 combination in vivo, we generated a patient-derived xenograft (PDX) model from an AML patient who had mutations in NPM1, FLT3 (FLT3-ITD), TET2, DNMT3A, and WT1 genes and a complex karyotype. The combination synergistically killed the PDX cells in vitro even under MSC co-culture conditions. After PDX cells had engrafted in NSG (NOD-SCID IL2Rgnull) mice, the mice were randomized into 4 groups (n=10/group) and treated with vehicle, C-82 (80 mg/kg, daily i.p injection), ABT-199 (100 mg/kg, daily oral gavage), or the combination for 30 days. Results showed that all treatments decreased circulating blasts (P=0.009 for C-82, P<0.0001 for ABT-199 and the combination) and that the combination was more effective than each single agent (P<0.001 vs C-82 or ABT-199) at 2 weeks of therapy. The combination also significantly decreased the leukemia burden in mouse spleens compared with controls (P=0.0046) and single agent treated groups (P=0.032 or P=0.020 vs C-82 or ABT-199, respectively) at the end of the treatment. However, the combination did not prolong survival time, likely in part due to toxicity. Dose modifications are ongoing. These results suggest that targeting Wnt/β-catenin and BCL-2, both essential for AML cell and stem cell survival, has synergistic activity via Rac1-mediated MCL-1 inhibition and could be developed into a novel combinatorial therapy for AML. Disclosures Andreeff: SentiBio: Equity Ownership; Oncolyze: Equity Ownership; Oncoceutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Consultancy; Amgen: Consultancy, Research Funding; Eutropics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Consultancy, Patents & Royalties: MDM2 inhibitor activity patent, Research Funding; Aptose: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Reata: Equity Ownership; Astra Zeneca: Research Funding; Celgene: Consultancy; United Therapeutics: Patents & Royalties: GD2 inhibition in breast cancer . Carter:novartis: Research Funding; AstraZeneca: Research Funding.

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The roles of hypoxia, PTEN, and Rad51 in mediating metastatic prostate cancer cells' responses to PARP inhibitor and topoisomerase 1 inhibitor.

Journal of Clinical Oncology ◽

10.1200/jco.2012.30.15_suppl.e13564 ◽

2012 ◽

Vol 30 (15_suppl) ◽

pp. e13564-e13564

Author(s):

Jingsong Zhang ◽

Minghui Wu ◽

Xue Wang

Keyword(s):

Prostate Cancer ◽

Dna Damage ◽

Topoisomerase I ◽

Metastatic Prostate Cancer ◽

Synthetic Lethality ◽

Parp Inhibitor ◽

Single Agent ◽

Study Results

e13564 Background: With the recent success of poly (ADP-ribose) polymerase inhibitor (PARPi) in the treatment of BRCA1 or BRCA2 mutated cancers, there is increasing interest to explore synthetic lethality in cancers with defective DNA repair pathways. Rad51 is an essential protein in the homologous recombination repair (HRR) of DNA double strand breaks. Previous studies with non metastatic prostate cancer (mCaP) cells have reported low Rad51 levels in cells with loss of PTEN or under hypoxia, which then led to their sensitivity to PARPi. Given intra tumor hypoxia and loss of PTEN is common in mCaP, we test PAPRi, ABT888 and DNA damaging topoisomerase I inhibitor, CPT11, either alone or in combination in mCaP preclinical models. Methods: mCaP cell lines with functional PTEN (DU145) and loss of PTEN (PC3) were grew under normoxia (21% O2) or hypoxia (0.2% O2). DNA damage, HRR, apoptosis were assessed with comet assay, western blot, immunofluorescence and flowcytometry. The regulation of RAD51 was studied with quantitative RT-PCR and RAD51 promoter reporter assay. PC3 xenograft was used for in vivo study. Results: Despite of its low levels of expression under hypoxia, up regulation of Rad51 was observed soon after treating hypoxic PC3 and Du145 cells with ABT888 or SN38, an active metabolite of CPT11. Such Rad51 up regulation led to less DNA damage and apoptosis under hypoxia compared to normoxia. Inhibiting RAD51 expression with siRNA overcame PC3 and Du145’s resistance to SN38. Furthermore, ABT888 enhanced the activities of SN38 as detected by clonogenic assay and flowcytometry under both normoxia and hypoxia. Consistent with the in vitro data, ABT888 by itself had limited anti-tumor activities despite the loss of PTEN in PC3 xenografts. The anti-tumor activity of single agent CPT11 was significantly improved with the ABT888 and CPT11 combination (P<0.008). Conclusions: neither loss of PTEN nor hypoxia sensitized mCaP cells to PARPi or DNA damaging drugs. Such resistance under hypoxia was at least partly due to up regulation of Rad51. Combining ABT888 with CPT11 overcame the resistance to CPT11 under hypoxia and enhanced its anti-tumor activities both in vitro and in vivo.

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Pooled Safety Analysis From Phase (Ph) 1 and 2 Studies of Carfilzomib (CFZ) In Patients with Relapsed and/or Refractory Multiple Myeloma (MM)

Blood ◽

10.1182/blood.v116.21.1954.1954 ◽

2010 ◽

Vol 116 (21) ◽

pp. 1954-1954 ◽

Cited By ~ 6

Author(s):

Seema B. Singhal ◽

David Samuel diCapua Siegel ◽

Thomas Martin ◽

Ravi Vij ◽

Michael Wang ◽

...

Keyword(s):

Board Of Directors ◽

Research Funding ◽

Single Agent ◽

Study Drug ◽

Underlying Disease ◽

Tolerability Profile ◽

Treatment Schedule ◽

Advisory Committees

Abstract Abstract 1954 Background: Carfilzomib (CFZ) is a novel, highly selective epoxyketone proteasome inhibitor that produces potent and sustained proteasome inhibition both in vitro and in vivo. CFZ appears to lack many of the off-target activities frequently associated with bortezomib (BTZ). This lack of off-target activity may account for observed differences in tolerability seen with CFZ including lack of significant neuropathy and minimal neutropenia and diarrhea. To date, single agent CFZ has been evaluated in Ph 1 and 2 studies in >600 patients, and the vast majority of patients treated had relapsed and/or refractory (R/R) MM. In these settings, CFZ has demonstrated durable single-agent activity and was well-tolerated in patients with advanced stage disease with co-morbidities including baseline neuropathy or renal insufficiency. Here we present the results of parallel safety analyses of patients from four Ph 1 and 2 studies with CFZ. Materials and Methods: The present safety analyses were based on data accumulated from patients enrolled in the following trials: PX-171-003 A0 (R/R MM), PX-171-003 A1 (R/R MM), PX-171-004 (relapsed MM), and PX-171-005 (R/R MM with varying degrees of renal function). In all studies, the treatment schedule was based on a 28-day cycle, dosing CFZ QDx2 each week for 3 weeks (Days 1, 2, 8, 9, 15, 16) with 12 days of rest. Doses of CFZ ranged from 15–20 mg/m2 in cycle 1 (005 [15 mg/m2], 003 A0 and A1, 004 [20 mg/m2]). In three studies CFZ was escalated to 27 mg/m2 after the first cycle, as tolerated (003- A1, 004-BTZ naïve subset and 005). In PX-171-005, low-dose dexamethasone was added in the majority of patients. Results: CFZ was well-tolerated by patients across the 4 studies analyzed. The most common treatment-emergent adverse events (AEs) included fatigue, anemia, nausea, dyspnea, and thrombocytopenia. Detailed descriptions of the incidence of treatment-related AEs (all Grades (G) in ≥25% of pts; ≥G3 in ≥5% of pts) across studies are presented in the table. Peripheral neuropathy (PN) occurred infrequently across all 4 studies (N= 517), with only 20 patients (3.9%) experiencing PN of any G and only 2 patients (0.4%) with G3 PN. Febrile neutropenia was likewise uncommon, occurring in only 3 patients (0.6%). Serious treatment emergent AEs (SAEs) occurring in ≥1% of patients and considered possibly/probably related to study drug across all 4 studies included: pneumonia (3.5%), congestive cardiac failure (2.5%), acute renal failure (1.7%), pyrexia (1.2%), and dyspnea (1%). Conclusions: Despite a substantial disease burden present in the patient populations described here, CFZ was well-tolerated by patients with MM across all studies examined. The excellent safety/tolerability profile of CFZ has permitted prolonged administration (in some cases over 24 mos of continuous therapy including extension study) with minimal dose modifications or discontinuations due to toxicity. The low levels of neuropathy seen with CFZ make this agent a potentially important treatment option for patients with pre-existing neuropathy from either underlying disease or prior neuropathic anti-myeloma therapy. Disclosures: Singhal: Celgene: Speakers Bureau; Takeda/Millenium: Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau; Onyx: Research Funding. Siegel:Millenium: Consultancy, Honoraria; Celgene: Consultancy, Honoraria. Martin:Celgene: Honoraria; Onyx: Consultancy. Vij:Onyx: Honoraria. Wang:Celgene: Research Funding; Onyx: Research Funding; Millenium: Research Funding; Novartis: Research Funding. Jakubowiak:Millennium Pharmaceuticals, Inc.: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees; Celgene: Consultancy, Honoraria; Centocor Ortho Biotec: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees; Exelixis: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees. Lonial:Millennium: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Onyx: Consultancy, Research Funding. Kukreti:Celgene: Honoraria; Roche: Honoraria; Ortho Biotech: Honoraria. Zonder:Millenium: Consultancy, Honoraria, Research Funding; Cephalon: Research Funding; Celgene: Honoraria. Wong:Onyx Pharmaceuticals: Employment. McCulloch:Onyx Pharmaceuticals: Employment. Kauffman:Onyx Pharmaceuticals: Employment. Niesvizky:Celgene: Consultancy, Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Millenium: Consultancy, Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Onyx: Consultancy, Research Funding. Stewart:Millennium: Consultancy; Celgene: Honoraria. Jagannath:Millenium, OrthoBiotec, Celgene, Merck, Onyx: Honoraria; Imedex, Medicom World Wide, Optum Health Education, PER Group: Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau.

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Addition of the PARP Inhibitor, Talazoparib, to Gemtuzumab Ozogamicin Significantly Enhances Anti-Leukemic Activity in Human CD33+ Acute Myeloid Leukemia

Blood ◽

10.1182/blood-2019-130427 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 1371-1371

Author(s):

Scott M. Portwood ◽

Marianna C Cantella ◽

Tara L. Cronin ◽

Eunice S. Wang

Keyword(s):

Dna Damage ◽

Parp Inhibitor ◽

Single Agent ◽

Parp Inhibitors ◽

Gemtuzumab Ozogamicin ◽

Nsg Mice ◽

Dose Dependent ◽

Advisory Role

Background CD33 (Siglec3) is a cell surface transmembrane receptor that is rapidly internalized and highly expressed on AML blasts but is absent on normal hematopoietic stem cells. Gemtuzumab ozogamicin (GO), a humanized anti-CD33 antibody conjugated to a DNA strand scission inducing agent (calicheamicin) was recently FDA approved for the treatment of newly-diagnosed or relapsed/refractory CD33-positive acute myeloid leukemia (AML). GO has been shown to exert clinical activity in leukemia patients. Poly (ADP-ribose) polymerase (PARP) inhibitors prevent the repair of single stranded DNA breaks by blocking the nicotinamide adenine dinucleotide (NAD) catalytic domain of the PARP protein and by preventing the dissociation of PARP from the DNA (PARP trapping). Talazoparib is unique among clinical PARP inhibitors in displaying 10,000-fold increased PARP trapping as compared to other agents . We hypothesized that combination therapy using GO and Talazoparib would result in synergistic anti-leukemic effects on human CD33+ AML cells due to the ability of the PARP inhibitor to enhance levels of DNA damage induced by GO therapy. Materials and Methods Human AML cell lines were characterized for CD33 expression using flow cytometry after staining with antibody-linked fluorescent QuantiBrite Beads. Cells were continuously exposed to varying doses of GO (10pM - 100mM) and PARP inhibitors (1nM - 100mM) for 96h alone and in combination. Cell viability was measured immediately following treatment using a WST colorimetric assay. Treatment-induced apoptosis (annexin/PI) and DNA damage (H2AX) were quantified by flow cytometric assays. Synergy reports were generated using Compusyn software. In vivo efficacy was assessed in NSG mice systematically engrafted with luciferase labeled human CD33+ AML cells following tail vein injection. Animals were treated with varying doses of vehicle, GO (1 and 50ug/kg 1x/week for 3 weeks), or talazoparib (0.1 and 0.33mg/kg 5 days/week) either alone or in combination. Treatment effects on leukemia burden, toxicity, and survival were determined by weekly whole animal bioluminescent imaging, total animal weights, and time to morbidity. Results Human AML cell lines (HEL, HL60) express high expression levels of CD33 molecules/cell (43,645 and 31,286 respectively) relative to negative controls. Continuous exposure to single agent GO and Talazoparib for 96h resulted in a dose dependent inhibition of human AML cell growth (HEL, HL60) . IC values for GO were 0.01 - 6.6μg/ml and for Talazoparib were 0.8-0.95μM. Combination in vitro therapy with GO (0.005 - 1μg/ml) and Talazoparib (fixed dose 100nM) resulted in synergistic anti-leukemic effects (p<0.01) significantly improving upon monotherapy. Software analyses yielded a combination Index (CI) <1 consistent with synergistic anti-leukemic effects. Combination GO and Talazoparib therapy also significantly enhanced AML cell apoptosis (p=0.0111) and levels of DNA damage (phosphorylated H2AX) (p=0.0054) over single agent activity. Evaluation of PARP trapping by western blot analysis is ongoing. In vivo administration of GO (1-50μg/kg) and Talazoparib (0.1-0.33mg/kg) in NSG mice with systemic engraftment of luciferase tagged human CD33+ AML cells was generally well tolerated with no significant weight loss or early morbidity. Single agent GO and Talazoparib therapy decreased systemic AML burden in a dose dependent manner and prolonged overall survival over vehicle treated mice (P<0.05). Concomitant GO (1μg/kg) and Talazoparib (0.33μg/kg) treatment was similarly well tolerated with no notable weight loss or toxicities. Combination GO and Talazoparib therapy significantly prolonged overall survival of leukemia xenografted mice over vehicle (p=0.0018) and single agent therapy with the same doses of GO (p=0.0018) and Talazoparib (p=0.0499), respectively). Conclusions In summary, our results demonstrate that the addition of the PARP inhibitor, Talazoparib, to the CD33 antibody drug conjugate, GO, results in potent in vitro and in vivo anti-tumor activity in human CD33+ AML preclinical models. Further studies investigating this novel combinatorial approach in AML are currently ongoing. Due to GO's FDA approval for CD33+ AML in 2018, this data strongly supports future clinical investigation using PARP inhibitors as a novel class of agents for combination therapy to significantly enhance the efficacy of ADCs. Figure 1 Disclosures Wang: Amgen: Other: Advisory role; Agios: Other: Advisory role; Stemline: Other: Advisory role, Speakers Bureau; Daiichi: Other: Advisory role; Abbvie: Other: Advisory role; Kite: Other: Advisory role; Jazz: Other: Advisory role; Astellas: Other: Advisory role, Speakers Bureau; celyad: Other: Advisory role; Pfizer: Other: Advisory role, Speakers Bureau.

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Epitope Dependent Augmentation of the Immune Response in Hemophilia Α Mice Immunized with Factor VIII/Antibody Immune Complexes

Blood ◽

10.1182/blood-2019-127436 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 2387-2387

Author(s):

Glaivy Batsuli ◽

Seema R Patel ◽

Courtney Cox ◽

Wallace H. Baldwin ◽

John S. Lollar ◽

...

Keyword(s):

Immune Response ◽

Dendritic Cells ◽

Board Of Directors ◽

Hemophilia A ◽

Advisory Board ◽

Inhibitory Antibody ◽

Advisory Committees ◽

Antibody Titers

Introduction: The immune response to factor VIII (fVIII) is a CD4+ T cell dependent process initiated by fVIII recognition and processing by antigen presenting cells. The C1 and C2 domains have been proposed as the primary domains that mediate fVIII internalization by dendritic cells. Our prior studies demonstrate that fVIII pre-bound to anti-C1 and C2 domain monoclonal antibodies (MAbs) reduces fVIII internalization by murine derived dendritic cells. However, anti-A1 and A3 domain antibodies increase fVIII endocytosis by dendritic cells. In this study, we analyzed the antibody titers of hemophilia A mice immunized with binary fVIII and MAb complexes to determine whether changes in fVIII internalization observed in vitro correspond to changes in the immune response to fVIII in vivo. Methods: Exon16 (E16) knockout mice deficient in fVIII were immunized with B-domain deleted fVIII in the presence of either anti-fVIII MAb 2-116 (anti-A1, IgG2a), 4A4 (anti-A2, IgG2a), 2-113 (anti-A3, IgG1), B136 (anti-C1, IgG2a), or 3D12 (anti-C2, IgG2b) versus fVIII alone. Mice were immunized by weekly retro-orbital injections of 0.1 µg fVIII incubated with 1 µg anti-fVIII MAb for 4 weeks followed by a boost dose of 0.2 µg fVIII and 2 µg anti-fVIII MAb one week later at week 5. Anti-fVIII ELISA titers (in arbitrary units, AU) were analyzed from plasma samples collected at week 7 to account for IgG half-life. A separate cohort of mice immunized with anti-fVIII MAbs alone served as controls to normalize ELISA titers in each fVIII/MAb group to account for residual injected MAbs in the plasma samples. Results: Hemophilia A mice immunized with fVIII/2-116 and fVIII/4A4 complexes significantly increased anti-fVIII ELISA titers compared to mice immunized with fVIII alone (figure 1). Mice immunized with fVIII/2-116 and fVIII/4A4 had median ELISA titers of 7,401 AU (interquartile range, IQR, 2,654 - 11,910 AU) and 3,620 AU (IQR 1,062 - 7,969 AU), respectively, compared to mice immunized with fVIII (median titer 1,063 AU, IQR 402 - 2,476 AU). MAb 2-116 is a non-inhibitory antibody with a titer of <1 Bethesda Unit (BU)/mg IgG, while 4A4 is a highly inhibitory antibody with a titer of 40,000 BU/mg IgG. Neither MAb interferes with fVIII binding to von Willebrand factor (VWF) or phospholipid vesicles. Mice immunized with fVIII/2-113 (median titer 2,210 AU, IQR 402 - 8,318 AU), fVIII/B136 (median titer 123 AU, IQR 0 - 9,709 AU), and fVIII/3D12 (median titer 3,244 AU, IQR 0 - 5,180 AU) did not have significantly different anti-fVIII ELISA titers compared to mice immunized with fVIII. However there was a trend towards reduced anti-fVIII titers with fVIII/B136 and fVIII/3D12 injections. MAbs B136 and 3D12 inhibit fVIII binding to VWF and have been shown to significantly increased fVIII clearance in hemophilia A mice compared to fVIII in a VWF-dependent manner. Median titers for mice immunized with MAbs alone to account for residual injected MAbs were 13 AU (2-116), 12 AU (4A4), 18 AU (2-113), 16 AU (B136), and 4 AU (3D12). Conclusions: Immunization of hemophilia A mice with fVIII/MAb complexes, specifically anti-A1 MAb 2-116 and anti-A2 MAb 4A4, enhance the immune response to fVIII. MAb 2-116 significantly increased anti-fVIII antibody titers in vivo, which correlates with increased fVIII internalization by immature dendritic cells observed in vitro. A better understanding of the effect of anti-fVIII antibodies on fVIII conformational changes could provide insight into whether these changes alter fVIII recognition by immune cells and subsequently propagate the immune response to fVIII at the onset of inhibitor formation or during immune tolerance induction. Disclosures Batsuli: Genentech: Other: Advisory board participant; Bayer: Other: Advisory board participant; Octapharma: Other: Advisory board participant. Meeks:HEMA Biologics: Membership on an entity's Board of Directors or advisory committees; Novo Nordisk: Membership on an entity's Board of Directors or advisory committees; Genentech: Membership on an entity's Board of Directors or advisory committees; Bioverativ: Membership on an entity's Board of Directors or advisory committees; Takeda-Shire: Membership on an entity's Board of Directors or advisory committees; Bayer: Membership on an entity's Board of Directors or advisory committees.

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EXTH-03. COMBINED TOP1 AND PARP INHIBITION ENFORCES GENOMIC INSTABILITY AND CELL DEATH IN PTEN-DEFICIENT GLIOBLASTOMA

Neuro-Oncology ◽

10.1093/neuonc/noab196.642 ◽

2021 ◽

Vol 23 (Supplement_6) ◽

pp. vi163-vi164

Author(s):

Olga Kim ◽

Madison Butler ◽

Ying Pang ◽

Guangyang Yu ◽

Mythili Merchant ◽

...

Keyword(s):

Dna Damage ◽

Cell Death ◽

Topoisomerase I ◽

Parp Inhibitor ◽

Annexin V ◽

Parp Inhibition ◽

Pten Loss ◽

Tensin Homolog

Abstract BACKGROUND Glioblastoma is an aggressive brain tumor with high mortality. The development of new therapies is critical for improving patient outcomes. LMP400, a novel topoisomerase I (TOP1) inhibitor, traps TOP1 cleavage complexes, thereby generating DNA damage. Poly(ADP-ribose) polymerase (PARP) is involved in DNA repair responses triggered by TOP1 inhibition. Niraparib is a potent PARP inhibitor that can cross the blood-brain barrier. Loss of phosphatase and tensin homolog (PTEN) occurs in 40% of GBM patients and is known to promote DNA damage repair deficiency. Here, we hypothesize that PTEN loss presents a vulnerability to a combined induction of DNA damage and inhibition of repair mechanisms. METHODS Human glioblastoma cells (U251, SNB-75, SF-295, LN18) and patient-derived glioblastoma stem cells (GSC923 and GSC827) were treated with LMP400 and/or Niraparib. Cell viability and apoptosis were examined using Celigo image cytometer and Annexin V/PI assay at 72h after treatment. Single clones after PTEN knockdown using shRNA were isolated after puromycin selection. For planned studies of PTEN knockout, sgRNA plasmids targeting PTEN will be transiently transfected and GFP-positive single KO clones will be isolated. PTEN will be restored in PTEN-null cells using lentiviral transduction. RESULTS CRISPR-Cas9 KO screening in GSC923 cells suggests that LMP400 is unlikely a substrate for ABC transporters. LMP400 and Niraparib synergistically induced cytotoxic effects in U251, SF-295, GSC923, GSC827 cells lacking PTEN expression. Combined LMP400/Niraparib led to increased expression of gamma-H2AX, cleaved caspase 3 and PARP, indicative of enhanced DNA damage and cell death. CONCLUSION LMP400 and Niraparib act synergistically to target PTEN-deficient glioblastoma by inducing DNA damage and cell death. These results will be further verified in isogenic cells in vitro as well as in vivo in a mouse model driven by PTEN deletion which would strongly support a novel therapeutic strategy in a subset of glioblastoma with PTEN loss.

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Co-Targeting of BCL2 with Venetoclax and MCL1 with S63845 Is Synthetically Lethal In Vivo in Relapsed Refractory Mantle Cell Lymphoma with Complex Karyotype Changes

Blood ◽

10.1182/blood-2018-99-112437 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 42-42

Author(s):

Pavel Klener ◽

Marek Trněný ◽

Ladislav Andera ◽

Zuzana Nahacka ◽

Magdalena Klanova ◽

...

Keyword(s):

Board Of Directors ◽

Cell Lines ◽

Cell Lymphoma ◽

Advisory Board ◽

Advisory Committees ◽

Mantle Cell ◽

Vitro Data ◽

In Vitro Data

Abstract Introduction Mantle cell lymphoma (MCL) is an aggressive subtype of B-cell non-Hodgkin lymphomas characterized by (over)expression of BCL2 and good sensitivity to a small molecule BCL2 inhibitor venetoclax. In the present study we analyzed molecular mechanisms of venetoclax resistance in MCL cells, and tested strategies to overcome it based on concurrent targeting of BCL2 a MCL1. Methods Cell death was determined by flow cytometry using Annexin-V/PI staining. Establishment of MCL cell clones with knock-down or transgenic overexpression of MCL1, BIM and NOXA, western blotting, immunohistochemistry of formalin-fixed paraffin-embedded tissue sections, and immunoprecipitation experiments were carried out as previously described (Klanova et al, Clin Cancer Res, 2016). All PDXs were derived in our laboratory from patients with relapsed MCL. All PDX were confirmed by NGS to keep majority of somatic mutations with the primary MCL cells from which they were derived. Samples were sequenced using SureSelectXT Human All Exon V6+UTR (Agilent Technologies, Santa Clara, CA) on the NextSeq 500 (Illumina, San Diego, CA) instrument according to manufacturer's protocols. Experimental therapies were implemented using NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ mice purchased from Jackson Laboratory (Bar Harbor, Maine, USA). Therapy was initiated when all mice developed palpable subcutaneous tumors (= day 1, D1). Venetoclax (VTX) and S63845 were from MedchemExpress, carfilzomib (CFZ) was from Charles University General hospital pharmacy. Carfilzomib (4 mg / kg) was administered intravenously (IV) on days 1 and 6. Venetoclax (40 mg / kg) was given by oral gavage on days 1, 2, 3, 6 and 7. S63845 (25 mg / kg) was administered IV on days 1, 2, 3, 6 and 7. Tumor volumes were calculated using the following formula: π / 6 × tumor length × width × height. Results By transgenic overexpression or shRNA-mediated knock-down we confirmed key roles of proapoptotic proteins BIM and NOXA in mediating venetoclax-induced cell death in MCL. We demonstrated that both BIM and NOXA are differentially expressed between MCL cell lines on one side, and primary MCL cells and patient-derived xenograft (PDX) cells on the other side. First, NOXA protein is significantly overexpressed in most MCL cell lines. Second, biallelic deletions of BIM harbored by three commonly used MCL cell lines (JEKO-1, MINO and Z138), and previously reported to be present in approx. 30% of MCL patients, were not found in primary MCL cells. As a consequence, vast majority of the in vitro data was implemented on venetoclax-sensitive cell lines HBL2 and MAVER-1, whose patterns of expression of BCL2, MCL1, BIM and NOXA are similar to primary MCL cells. We demonstrated that MCL1, another key anti-apoptotic protein, plays an essential role in mediating resistance to venetoclax. First, MCL1 functions as a buffer for BIM released from BCL2 upon binding of venetoclax thereby preventing activation of BAX and induction of apoptosis. Second, marked upregulation of MCL1 protein was associated with acquired resistance to venetoclax in two most sensitive MCL cell lines HBL2 and MAVER-1. Based on the in vitro data we proposed two experimental treatment strategies that co-targeted MCL1 (along with inhibition of BCL2 with venetoclax): a direct blockage with a highly specific small molecule MCL1 inhibitor S63845, and an indirect blockage achieved by proteasome inhibitor carfilzomib that upregulates the proapoptotic protein NOXA that specifically binds and blocks MCL1. The combination of venetoclax and S63845 demonstrated synthetic lethality in vivo inducing the longest "remissions" of MCL bearing mice (i.e. temporary disappearance of subcutaneous MCL tumors) using a panel of four different PDXs derived from patients with relapsed / refractory MCL with complex karyotype changes (Figure 1). The combination of carfilzomib and venetoclax was far less effective, and at the same time more toxic suggesting functional blockage of MCL1 induced by overexpressed NOXA is either incomplete or insufficient. Conclusions Our data strongly support investigation of venetoclax in combination with S63845 as an innovative proapoptotic treatment strategy for chemoresistant MCL patients with adverse cytogenetics in the clinical grounds. Figure 1 Figure 1. Disclosures Trněný: Janssen: Membership on an entity's Board of Directors or advisory committees, Other: Advisory board; Gilead: Honoraria; Morphosys: Membership on an entity's Board of Directors or advisory committees, Other: Advisory board; Abbvie: Honoraria, Research Funding; F. Hoffman-La Roche Ltd: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Advisory board, Research Funding; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Advisory board; Sandoz: Honoraria; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Advisory board; Incyte: Membership on an entity's Board of Directors or advisory committees, Other: Advisory board.

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Phase I Study of IMGN901, Used as Monotherapy, in Patients with Heavily Pre-Treated CD56-Positive Multiple Myeloma - A Preliminary Safety and Efficacy Analysis.

Blood ◽

10.1182/blood.v114.22.2883.2883 ◽

2009 ◽

Vol 114 (22) ◽

pp. 2883-2883 ◽

Cited By ~ 8

Author(s):

Asher Chanan-Khan ◽

Jeffrey Wolf ◽

Mecide Gharibo ◽

Sundar Jagannath ◽

Nikhil C. Munshi ◽

...

Keyword(s):

Clinical Trial ◽

Multiple Myeloma ◽

Board Of Directors ◽

Dose Level ◽

Single Agent ◽

Duration Of Treatment ◽

Advisory Committees ◽

Grade 3

Abstract Abstract 2883 Poster Board II-859 Background: IMGN901 (huN901-DM1/BB-10901) is a novel anticancer agent consisting of a potent cytotoxic maytansinoid, DM1, attached to a CD56-binding monoclonal antibody, huN901, using an engineered linker. Once bound to CD56 on a cancer cell, the conjugate is internalized and releases DM1. About 70% of multiple myeloma (MM) cases have surface expression of CD56. In preclinical settings, IMGN901 showed significant in vitro and in vivo anti-myeloma activity as a single agent and in combination with approved drugs such as lenalidomide. Objectives: To determine the maximum tolerated dose (MTD), pharmacokinetics (PK), and activity of IMGN901, used as monotherapy, in patients with MM. Methods: Patients with CD56+ relapsed or relapsed/refractory MM receive a single IV infusion of IMGN901 on 2 consecutive weeks every 3 weeks. Patients are enrolled into each dose level in cohorts of 3, with dose-limiting toxicity (DLT) triggering cohort expansion. The European Bone Marrow Transplant (EBMT) criteria were used for response assessment. Results: Twenty-three CD56+ MM patients have received IMGN901 at doses ranging from 40 to 140 mg/m2/week. Most of these 23 patients had been treated with 6 or more chemotherapy regimens prior to study entry. Two of 6 patients treated at the 140 mg/m2/week dose experienced DLT (grade 3 fatigue and grade 3 acute renal failure) and a lower dose has been defined as the MTD. Commonly reported adverse events that were at least possibly related to IMGN901 were fatigue, increased aspartate aminotransferase, increased uric acid, sensory neuropathy and headache. None of the patients experienced serious hypersensitivity reactions or demonstrated a humoral response against either the antibody or DM1 component of IMGN901. Sustained partial response (PR) was documented in 1 patient treated at 140 mg/m2/week and 3 minor responses (MR) were reported in 1 patient each at doses of 60, 90, and 112 mg/m2/week. Of the 23 patients receiving any dose level of IMGN901, 8 remained on IMGN901 treatment for at least 15 weeks. Five of these 8 patients continued treatment on IMGN901 for at least 24 weeks, and two of these 5 patients remained on IMGN901 for at least 50 weeks. Preliminary PK results indicate an approximately linear relationship between dose and observed maximal serum concentration. Conclusion: This is the first study of IMGN901 in patients with MM. The MTD of this agent in MM patients is now defined. Our experience with IMGN901 in this clinical trial demonstrates an overall favorable safety profile. Although the primary objective of this clinical trial was to determine the MTD of single agent IMGN901, exciting single agent activity was observed in heavily pretreated MM patients. This is particularly encouraging as the duration of treatment with IMGN901 in some patients was longer than duration of treatment with prior regimens of approved agents. Clinical observations noted here (including single agent efficacy and the favorable toxicity profile) as well as findings from preclinical combination studies warrant continued investigation of this novel agent in patients with MM especially in combination with approved anti-myeloma agents/regimens such as lenalidomide and dexamethasone. Disclosures: Chanan-Khan: Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millennium: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Immunogen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Jagannath:Millennium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria; Merck: Honoraria. Miller:Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millennium: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Guild:ImmunoGen, Inc: Employment. Zildjian:ImmunoGen, Inc: Employment. Qin:ImmunoGen, Inc.: Employment. O'Leary:ImmunoGen, Inc.: Employment.

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Venetoclax Synergizes with the RNA-Directed Nucleoside Analog 8-Chloro-Adenosine in Acute Myeloid Leukemia in Vitro and In Vivo

Blood ◽

10.1182/blood-2020-143240 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 22-23

Author(s):

Ralf Buettner ◽

Le Xuan Truong Nguyen ◽

Corey James Morales ◽

Lisa S Chen ◽

Timothy Synold ◽

...

Keyword(s):

Clinical Trial ◽

Board Of Directors ◽

Myeloid Leukemia ◽

Single Agent ◽

Inhibitory Effect ◽

Nucleoside Analog ◽

Research Support ◽

Advisory Committees

Relapse of acute myeloid leukemia (AML) is attributed to the persistence of quiescent leukemia stem cells (LSCs). Bcl-2 inhibition has been shown to target primitive leukemia progenitors. Venetoclax (VEN) is a FDA-approved Bcl-2-selective inhibitor for the treatment of AML. Although the activity of single agent VEN in AML patients (pts.) is modest, clinical efficacy in newly diagnosed, older pts. unfit for intense chemotherapy has been shown when VEN is combined with the hypomethylating agents (HMAs) azacytidine and decitabine or with low-dose nucleoside analog cytarabine. We have recently shown that VEN in combination with HMAs augments oxidative stress in AML cells and provided a molecular mechanism for the VEN-HMA-regulated NF-E2-related factor 2 (Nrf2) antioxidant pathway that could explain the results observed in early clinical studies in AML. Although about 70% of pts. initially respond to these VEN treatment regimens, about 30% of pts. do not and diminished efficacy of VEN combination treatments have been observed in pts. harboring poor-prognosis markers such as FLT3-ITD. In addition, future relapse of a percentage of pts. treated with VEN combinations is expected. Thus, novel treatment options for are urgently needed. We previously reported that the ribose containing, RNA-directed nucleoside analog 8-chloro-adenosine (8-Cl-Ado) demonstrates cytotoxic activity against AML cells and LSCs in vitro and in vivo, without significantly affecting normal hematopoietic stem cells. Importantly, our initial, unpublished results from a phase I/II clinical trial with single agent 8-Cl-Ado in pts. with refractory/relapsed AML demonstrate encouraging clinical benefits. Moreover, we have reported that FLT3-ITD AML is particularly sensitive to 8-Cl-Ado, thus suggesting 8-Cl-Ado plus VEN as a potential novel therapeutic regimen for treatment of AML. We here report that the VEN plus 8-Cl-Ado combination inhibited in vitro growth and induced apoptosis in AML primary cells, LSCs and cell lines significantly more compared to treatment with the individual agents. For in vitro cell growth studies, combination indices of <1 for all experimental and calculated drug concentrations demonstrated strong synergy between the two drugs in 2 human AML cell lines (MV4-11 and KG-1a) and in AML cells isolated from 2 pts. Moreover, immune compromised NSG mice engrafted with FLT3-ITD MV4-11 cells survived significantly longer when treated with VEN (20 mg·kg‒1·day‒1, daily oral) plus 8-Cl-Ado (50 mg·kg‒1·day‒1; osmotic pump), as compared to single agent or vehicle-treated mice (p<0.006, VEN+8-Cl-Ado vs. 8-Cl-Ado; p<0.001 VEN+8-Cl-Ado vs. VEN). LSCs depend on amino acid metabolism-driven and/or fatty acid oxidation (FAO)-driven oxidative phosphorylation (OXPHOS) for energy production. VEN is known to target LSCs through inhibition of OXPHOS by targeting amino acid uptake/metabolism. We report here that 8-Cl-Ado inhibited the FAO pathway and down-regulated the oxygen consumption rate (OCR), a marker for OXPHOS, in LSCs. However, whereas 500 nM of 8-Cl-Ado was sufficient to induce MV4-11 growth inhibition, 1 microM of 8-Cl-Ado was needed for maximum inhibitory effect on FAO. We also report that 8-Cl-Ado increased expression of the anti-apoptotic protein p53. It was previously reported that p53 induces FAO in LSCs. Knockdown of p53 by siRNA augmented the inhibitory effect of 8-Cl-Ado on FAO and OCR. Importantly, addition of VEN could completely overcome the p53-induced activation of FAO and OCR. Mechanistically, we show that 8-Cl-Ado inhibited ribosomal RNA (rRNA) synthesis, a prerequisite for cellular proliferation, through down-regulation of the transcription initiation factor 1 (TIF-IA) protein. Since TIF-1A negatively regulates p53 expression, the inhibition of TIF-1A by 8-Cl-Ado resulted in up-regulation of p53 and subsequent p53-induced upregulation of FAO and OCR, thus diminishing the suppressive effects of 8-Cl-Ado on FAO and OCR. We further show that the VEN plus 8-Cl-Ado combination strongly induced p53 signaling, as shown by activation and inhibition of downstream p21 and PCNA proteins, respectively. This combination also augmented DNA fragmentation and apoptosis in LSCs. Thus, our data suggest that the synergy seen in AML with the VEN plus 8-Cl-Ado combination can be explained at least in part due to augmented inhibition of FAO and OXPHOS and represents a promising novel treatment for AML. Disclosures Pullarkat: Dova: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Servier: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genetech: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AbbVie, Inc.: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Marcucci:Iaso Bio: Membership on an entity's Board of Directors or advisory committees; Abbvie: Speakers Bureau; Novartis: Speakers Bureau; Pfizer: Other: Research Support (Investigation Initiated Clinical Trial); Merck: Other: Research Support (Investigation Initiated Clinical Trial); Takeda: Other: Research Support (Investigation Initiated Clinical Trial). Rosen:Celgene: Speakers Bureau; NeoGenomics: Consultancy; Seattle Genetics: Consultancy; Aileron Therapeutics: Consultancy; Novartis: Consultancy; paradigm Medical Communications: Speakers Bureau; Abbvie: Speakers Bureau; Pebromene: Consultancy.

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The Vk*MYC Mouse Model of Myeloma Identifies Successful Combination Therapies for the Treatment of Bortezomib Refractory Myeloma Patients

Blood ◽

10.1182/blood.v116.21.3015.3015 ◽

2010 ◽

Vol 116 (21) ◽

pp. 3015-3015 ◽

Cited By ~ 1

Author(s):

Marta Chesi ◽

Stephen Palmer ◽

Victoria Garbitt ◽

P. Leif Bergsagel

Keyword(s):

Clinical Trials ◽

Mouse Model ◽

Board Of Directors ◽

Cell Lines ◽

Human Disease ◽

Single Agent ◽

Hdac Inhibitors ◽

Advisory Committees

Abstract Abstract 3015 Several preclinical models are available to assess the efficacy of novel anti-myeloma therapies, each of them with specific utilities. The most commonly utilized are: 1) Human myeloma cell lines (HMCLs) offer the advantage of being easily manipulated and well genetically characterized and therefore are best used to provide in-vitro target validation and to demonstrate specific target inhibition by a drug. On the other hand, they are highly proliferative and do not recapitulate the complexity of the human disease in an endogenous micro-environment. 2) Xenograft studies, in which HMCLs are injected into immunodeficient mice, serve the purpose of demonstrating that in-vivo target inhibition can be achieved under physiological conditions, but again fail to represent the indolence of human MM and its complex interaction with the BM stromal cells. Drug screenings performed on both these models tend inevitably to overestimate the antimyeloma activity of compounds that simply inhibit proliferation, but are ineffective in targeting the bulk of MM tumor. 3) Direct cytotoxic studies on primary patients cells, alone or in co-culture with stroma cell lines, are useful in assessing a pro-apoptotic activity in a way that is completely independent on proliferation. However, once again this in-vitro model does not capture the complete biology of human MM. The immuno-competent Vk*MYC mouse model of myeloma has already demonstrated high biological fidelity to the human disease, making it an ideal model to study the behavior of myeloma cells in the context of a native microenvironment and immune system. Furthermore, this model offers the advantage of studying both indolent, BM localized, untreated MM (primary MM), and, with the use of transplants into syngeneic hosts, advanced, more proliferative and refractory disease (secondary MM). Using the primary MM model, we have assessed the anti-myeloma activity of 30 known and novel compounds, many of which currently in clinical trials, and found that agents effective in the treatment of patients are active in this model, whereas agents ineffective in the treatment of patients are not. From this study, the most promising class of novel agents in clinical trials are the HDAC inhibitors vorinostat and panobinostat. Based on this promising single agent activity, we sought to model the effects of combination therapy in the secondary myeloma models that we specifically generated to be bortezomib refractory or multidrug resistance. Although transplanted mice treated with full dose single agent bortezomib, vorinostat or panobinostat showed no response and died within three weeks post transplant, recipient mice treated with bortezomib in combination with either vorinostat or panobinostat achieved complete response and are still alive 10 weeks post-transplant. We conclude that the bortezomib + HDAC inhibitors is an active combination that overcomes in vivo bortezomib resistance. Furthermore, the Vk*MYC model provides an excellent platform for the development of novel combinations aimed to the treatment of refractory MM disease. Disclosures: Bergsagel: Amgen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Genentech: Membership on an entity's Board of Directors or advisory committees; Millennium: Speakers Bureau; Novartis: Speakers Bureau.

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