Panobinostat Dose Research Articles

A Phase Ib Dose-finding Study of Panobinostat and Ruxolitinib in Myelofibrosis.

A Phase Ib Dose-finding Study of Panobinostat and Ruxolitinib in Myelofibrosis.

DIPG-10. A Phase I trial of panobinostat following radiation therapy in children with diffuse intrinsic pontine glioma (DIPG) or H3K27M-mutated thalamic diffuse midline glioma (DMG): Report from the Pediatric Brain Tumor Consortium (PBTC-047)

INTRODUCTION: Panobinostat is an oral HDAC inhibitor with pre-clinical activity against DIPG. The phase I study in children with progressive DIPG (stratum 1) defined the maximum-tolerated dose (MTD) as 10 mg/m2 administered 3x/week, 3 weeks on/1 week off. Herein, we report results of stratum 2, involving children with non-progressive DIPG/DMG using an alternative schedule. Primary objectives were to describe the toxicity profile and define the MTD; secondary objectives were to describe progression-free survival (PFS) and overall survival (OS). PATIENTS AND METHODS: Patients with non-progressive DIPG or H3K27M-mutated thalamic DMG were eligible >14 days following standard radiation therapy only. Panobinostat was given every other day, 3x/week, on alternate weeks. Patients who received at least one dose of panobinostat were evaluable for toxicity. Four dose levels (DL) were evaluated: DL1 (16mg/m2/dose), DL2 (22 mg/m2/dose), DL3 (28 mg/m2/dose) and DL4 (36 mg/m2/dose). Dose escalation was determined by a continuous reassessment method. Correlative studies included pharmacokinetics obtained on course 1, day 1, and day 3 prior to subsequent dosing. RESULTS: Thirty-four eligible patients (median age, 7.6 [3-16] years) were enrolled with 29 evaluable for dose finding; DL1, n=3; DL2, n=10; DL3, n=11; DL4, n=5. The primary toxicities were myelosuppression and gastrointestinal. Eight DLTs occurred: DL2, Grade 3 thrombocytopenia (n=1); DL3, Grade 4 neutropenia (n=3), Grade 4 neutropenia and Grade 4 thrombocytopenia, (n=1); DL4, Grade 2 nausea (n=1), Grade 3 increased ALT (n=1), Grade 4 thrombocytopenia (n=1). Median PFS from drug initiation was 4.4 (1-11.2) months; median OS from diagnosis was 11.7 (4.5-25) months. These did not significantly differ from the PBTC historical cohort (PFS, p-value 0.4967; OS, p-value 0.6457). CONCLUSION: The MTD of panobinostat administered on this schedule to children with non-progressive DIPG/DMG is 22 mg/m2/dose. The primary DLT was myelosuppression. There was no significant improvement in PFS or OS in this cohort.

Epigenetic Priming with Pre-Transplant Oral Panobinostat Followed By Post-Transplant Consolidation

Despite the rich armamentarium of novel agents that are available to treat multiple myeloma (MM), high dose melphalan (HDM) and stem cell transplant (SCT) remain an essential therapy that achieves long-term durable remissions. However, most patients relapse following HDM-SCT due to the persistence of minimal residual disease (MRD). Therefore, there remains an unmet clinical need to overcome chemoresistant MRD and potentially achieve a cure for MM patients. Here, we describe a phase Ib trial designed to epigenetically priming with pre-transplant oral panobinostat to increase MRD sensitivity to HDM-SCT.The contribution of dysregulated gene silencing to epigenomic alterations in cancer development provides a strong rationale for the use of epigenetic modulators, such as the histone deacetylase (HDAC) inhibitor panobinstat as anti-myeloma therapy. Access to DNA is primarily governed by chromatin structure such that its configuration is under control of histone acetylators and deacetylators. Inhibition of histone deacetylases weakens the histone-DNA bonds and decondenses chromatin, i.e., epigenetic priming, which potentially enhances sensitivity to melphalan. Pre-clinical studies have demonstrated a strong synergistic effect between panobionostat (LBH589) and melphalan in in vitro as well as in vivo studies utilizing patient-derived xenograph models, i.e., SCID-hu model of human MM, LAG-1(Sanchez et al. Leukemia research. March 2011). Furthermore, HDAC inhibitors suppress multi-drug resistance protein-1 (MRP1) and it can count as another mechanism of synergy for this class of drugs and alkylating agents in hematologic disorders (Tsubaki M. et al. Leukemia research. Oct 2012). Taken together, these studies support HDAC inhibitors in combination with melphalan to augment anti-myeloma efficacy of HDM-SCT. Here, we propose the combination through a pre-SCT epigenetic priming phase with high dose panobinostat and a post-SCT lower dose panobinostat consolidation phase (Study Schema).Trial design: We propose a Simon 3+3 design to test panobinostat at three dose levels of 20, 30 and 40 mg every other day for four doses prior to high dose melphalan as study schema illustrates. There will not be any intra-patient dose escalation. The study will be extended to another 15 patients at the maximum tolerated dose for the pre-SCT phase. All patients regardless of the pre-SCT panobinostat dose level will received fixed dose of Panobinostat. Primary and Secondary objectives and endpoints are listed in Table 1.Rationale for high dose panobinostat in epigenomic phase: Previous reports of HDACi combined with standard-dose chemotherapy (e.g., Ifosfomide, Carboplatin, and Etoposide for lymphoma or 7+3 for acute myeloid leukemia) had shown prolonged myelosuppression as the main adverse effect, but no significant increase in the non-hematological toxicities. Therefore, we predict the use of peripheral blood progenitor cells in the offered study has potential to circumvent the increased myelotoxicity associated with pre-SCT high dose panobinostat, and it may render the opportunity to test higher doses such as 40 mg every other day before SCT as epigenetic priming strategy.Rational for low dose panobinostat dosing for the consolidation phase: The Panobinostat consolidation design will follow the positive landmark trial by the Australian group (Mithraprabhu S. et al. British J. Hemat. Apr 2021). In their study panobinostat was given at 20 mg three times weekly on alternate weeks for 6 months started 8-12 weeks post-transplant was administered. Forty eight percent of patients improved their depth of response after a median range of 4.3 months of panobinostat. In responders, T lymphocyte histone acetylation increased after both three cycles and six cycles of panobinostat when compare to baseline, with no differences in no-responders. [Display omitted] DisclosuresMalek: Janssen: Other: Advisory board ; Bluespark Inc.: Research Funding; BMS: Honoraria, Research Funding; Amgen: Honoraria; Cumberland Inc.: Research Funding; Sanofi: Other: Advisory Board; Medpacto Inc.: Research Funding; Takeda: Honoraria. Metheny: Incyte: Speakers Bureau; Pharmacosmos: Honoraria. Stricker: Secura Bio: Current Employment. OffLabel Disclosure:Panobinostat has been used as single agent therapy before and after transplant in this trial.

Focused Ultrasound-Mediated Blood-Brain Barrier Opening Enhances Panobinostat Efficacy in a Murine Diffuse Intrinsic Pontine Glioma Model

Purpose/Objective(s)Diffuse intrinsic pontine glioma (DIPG) is the most lethal brain tumor in children with no effective treatment options to date. The prognosis remains poor with a median overall survival of less than 1 year. Recent in vitro drug screening studies found the histone deacetylase (HDAC) inhibitor, panobinostat, to be highly effective against DIPG. However, as panobinostat has poor blood-brain barrier (BBB) penetration, phase 1 clinical trials using systemic administration of panobinostat have been unsuccessful. Therefore, improved efficacy will require enhancement of delivery into the brain. Focused ultrasound (FUS), a non-ionizing acoustic form of radiation, has been shown to safely and non-invasively open the BBB, which can increase drug delivery. In this study, we hypothesize that FUS-mediated BBB opening (BBBO) can enhance the delivery of panobinostat for a therapeutic benefit in DIPG.Materials/MethodsA syngeneic DIPG model was established by injecting mouse DIPG cells (PDGFB+, H3.3K27M, p53−/−) intracranially. A single-element, spherical-segment FUS transducer (center frequency: 0.5 MHz) driven by a function generator through a power amplifier was used with concurrent microbubble injection to perform BBBO. We then utilized magnetic resonance imaging to evaluate BBBO and tumor progression.ResultsWe first demonstrated that FUS-mediated BBBO is safe and feasible in mice with DIPG tumors by MRI and passive cavitation detection. Our DIPG cell line was shown to be very sensitive to panobinostat in cell viability assay (IC50 = 0.012 μM). The combined treatment of FUS-mediated BBBO and panobinostat showed benefits in both local control and overall survival.ConclusionThe current results demonstrate that FUS could increase the treatment efficacy of panobinostat in a DIPG animal model due to the improved targeted dose of systemic panobinostat in the DIPG tumors. We believe these data establish a strong preclinical rationale to assess the combination of FUS-mediated BBB opening with panobinostat in pediatric patients with DIPG. Diffuse intrinsic pontine glioma (DIPG) is the most lethal brain tumor in children with no effective treatment options to date. The prognosis remains poor with a median overall survival of less than 1 year. Recent in vitro drug screening studies found the histone deacetylase (HDAC) inhibitor, panobinostat, to be highly effective against DIPG. However, as panobinostat has poor blood-brain barrier (BBB) penetration, phase 1 clinical trials using systemic administration of panobinostat have been unsuccessful. Therefore, improved efficacy will require enhancement of delivery into the brain. Focused ultrasound (FUS), a non-ionizing acoustic form of radiation, has been shown to safely and non-invasively open the BBB, which can increase drug delivery. In this study, we hypothesize that FUS-mediated BBB opening (BBBO) can enhance the delivery of panobinostat for a therapeutic benefit in DIPG. A syngeneic DIPG model was established by injecting mouse DIPG cells (PDGFB+, H3.3K27M, p53−/−) intracranially. A single-element, spherical-segment FUS transducer (center frequency: 0.5 MHz) driven by a function generator through a power amplifier was used with concurrent microbubble injection to perform BBBO. We then utilized magnetic resonance imaging to evaluate BBBO and tumor progression. We first demonstrated that FUS-mediated BBBO is safe and feasible in mice with DIPG tumors by MRI and passive cavitation detection. Our DIPG cell line was shown to be very sensitive to panobinostat in cell viability assay (IC50 = 0.012 μM). The combined treatment of FUS-mediated BBBO and panobinostat showed benefits in both local control and overall survival. The current results demonstrate that FUS could increase the treatment efficacy of panobinostat in a DIPG animal model due to the improved targeted dose of systemic panobinostat in the DIPG tumors. We believe these data establish a strong preclinical rationale to assess the combination of FUS-mediated BBB opening with panobinostat in pediatric patients with DIPG.

Upregulation of CD38 Expression on Multiple Myeloma Cells By the HDAC Inhibitor Ricolinostat Augments the Efficacy of Daratumumab

Background:The anti-CD38 antibody daratumumab is effective and increasingly being utilized to treat multiple myeloma. A clinical observation with daratumumab is that expression of CD38 on pretreatment myeloma cells correlates with efficacy, and patients with higher CD38 expression have a higher chance to respond. Moreover, during daratumumab therapy, there are reduced CD38 expression levels on myeloma cells, favoring immune escape and disease progression. We have recently shown that the histone deacetylase (HDAC) inhibitor panobinostat induces CD38 upregulation and augments the antibody-dependent cellular cytotoxicity (ADCC) of daratumumab (García-Guerrero E, Blood 2017). Here, we investigated the alternative HDAC inhibitor ricolinostat and all-trans retinoic acid (ATRA) to determine whether upregulation of CD38 is a class effect, and to identify the substance that works most synergistically with daratumumab.Methods:The myeloma cell lines MM1.S and OPM2 were treated with titrated doses of ricolinostat (0, 5, 10 µM), ATRA (0, 10, 25 nM) and panobinostat (0, 10, 25 nM). Expression of CD38, B-cell maturation antigen (BCMA) and SLAMF7 was analyzed by flow cytometry after 24, 48 and 72 h of exposure. ADCC against HDAC inhibitor-treated and untreated myeloma cells was analyzed after addition of PBMC at an effector to target ratio of 25:1 in the presence of daratumumab (1, 10, 50 ug/mL) or isotype control.Results:We first treated the myeloma cell line MM1.S with each of the HDAC inhibitors and analyzed their direct cytotoxic antimyeloma effect. We found the strongest effect with ricolinostat where live MM1.S myeloma cells had decreased to 50% and 20% after 48 h of exposure to 5 and 10 µM of the drug, respectively. Consistent with previous work the direct anti-myeloma effect of panobinostat (decrease of live MM1.S myeloma cells to 85% and 50% after 48 h of exposure to 10 and 25 nM, respectively) and ATRA (no cytotoxic effect) was lower compared to ricolinostat.We then analyzed expression of CD38 on residual live i.e. 7-AAD negative MM1.S cells by flow cytometry and observed a 2-fold (5 µM) and 2,5-fold (10 µM) increase in CD38 expression by mean fluorescence intensity (MFI) after treatment with ricolinostat-treated compared to untreated MM1.S cells. The increase in CD38 expression was already detectable after 24 h and further increased with longer exposure to the drug. Off note, withdrawal of ricolinostat resulted in rapid decline of CD38 expression to baseline levels but increased again to the same magnitude within 24 h of re-exposure to the drug. Overall, the increase in CD38 expression was strongest with ricolinostat followed by panobinostat and ATRA, which we confirmed with several myeloma cell lines and primary myeloma cells. We also confirmed that ricolinostat-induced upregulation of CD38 specifically occurred in myeloma cells and not in the lymphoma cell lines Raji and JeKo-1. In contrast to CD38, expression of BCMA and SLAMF7 after treatment of myeloma cells with ricolinostat had decreased.We then treated myeloma cells with ricolinostat for 48 hours to induce upregulation of CD38 and then performed ADCC assays with daratumumab in the presence of ricolinostat. We found, that the combination treatment ricolinostat plus daratumumab eliminated 95,6% of MM1.S cells after 20h; while 87,4% were eliminated with ricolinostat alone, and only 22,6% with daratumumab alone. Preliminary data show that ricolinostat does not affect expression of the complement inhibitor CD55 and induces a lower increase in CD59 expression compared to panobinostat. Experiments to evaluate complement-dependent cytotoxicity (CDC), and to confirm the synergistic antimyeloma effect of ricolinostat and daratumumab in a murine xenograft myeloma model, are ongoing.Conclusions:Our data demonstrate that the HDAC inhibitor ricolinostat induces upregulation of CD38 expression on myeloma cells. The increase in CD38 expression after treatment with ricolinostat is stronger compared to panobinostat and ATRA. Our data suggest that upregulation of CD38 on myeloma cells is a class effect of HDAC inhibitors, and identify ricolinostat as a highly synergistic combination partner for daratumumab, due to its considerable intrinsic antimyeloma activity. Our data suggest that combination treatment with ricolinostat and daratumumab could increase response rates and extend duration of responses of daratumumab therapy. DisclosuresNo relevant conflicts of interest to declare.

Targeting HDACs in Pancreatic Neuroendocrine Tumor Models.

Compared to pancreatic adenocarcinoma (PDAC), pancreatic neuroendocrine tumors (PanNET) represent a rare and heterogeneous tumor entity. In addition to surgical resection, several therapeutic approaches, including biotherapy, targeted therapy or chemotherapy are applicable. However, primary or secondary resistance to current therapies is still challenging. Recent genome-wide sequencing efforts in PanNET identified a large number of mutations in pathways involved in epigenetic modulation, including acetylation. Therefore, targeting epigenetic modulators in neuroendocrine cells could represent a new therapeutic avenue. Detailed information on functional effects and affected signaling pathways upon epigenetic targeting in PanNETs, however, is missing. The primary human PanNET cells NT-3 and NT-18 as well as the murine insulinoma cell lines beta-TC-6 (mouse) and RIN-T3 (rat) were treated with the non-selective histone-deacetylase (HDAC) inhibitor panobinostat (PB) and analyzed for functional effects and affected signaling pathways by performing Western blot, FACS and qPCR analyses. Additionally, NanoString analysis of more than 500 potentially affected targets was performed. In vivo immunohistochemistry (IHC) analyses on tumor samples from xenografts and the transgenic neuroendocrine Rip1Tag2-mouse model were investigated. PB dose dependently induced cell cycle arrest and apoptosis in neuroendocrine cells in human and murine species. HDAC inhibition stimulated redifferentiation of human primary PanNET cells by increasing mRNA-expression of somatostatin receptors (SSTRs) and insulin production. In addition to hyperacetylation of known targets, PB mediated pleitropic effects via targeting genes involved in the cell cycle and modulation of the JAK2/STAT3 axis. The HDAC subtypes are expressed ubiquitously in the existing cell models and in human samples of metastatic PanNET. Our results uncover epigenetic HDAC modulation using PB as a promising new therapeutic avenue in PanNET, linking cell-cycle modulation and pathways such as JAK2/STAT3 to epigenetic targeting. Based on our data demonstrating a significant impact of HDAC inhibition in clinical relevant in vitro models, further validation in vivo is warranted.

Phase 1 open-label study of panobinostat, lenalidomide, bortezomib\u2009+\u2009dexamethasone in relapsed and relapsed/refractory multiple myeloma

Additional therapeutic options are needed for relapsed and refractory multiple myeloma (RRMM). We present data from a phase 1b, open-label, dose-escalation study (NCT01965353) of 20 patients with RRMM (median age: 63 years [range: 50–77]) and a median of four prior regimens (range: 2–14); 85% had refractory disease (lenalidomide [80%]; bortezomib [75%]; lenalidomide and bortezomib [50%]). Patients received a median of six cycles (range: 1–74) of panobinostat (10 or 15 mg), lenalidomide 15 mg, bortezomib 1 mg/m2, and dexamethasone 20 mg (pano-RVd). Median follow-up was ~14 months. Six dose-limiting toxicities were reported (mostly hematological); maximum tolerated dose of panobinostat (primary endpoint) was 10 mg. Most common adverse events (AEs) were diarrhea (60%) and peripheral neuropathy (60%); all grade 1/2. Grade 3/4 AEs occurred in 80% of patients and included decreased neutrophil (45%), platelet (25%) and white blood cell (25%) counts, anemia (25%) and hypophosphatemia (25%). No treatment-related discontinuations or mortality occurred. In evaluable patients (n = 18), overall response rate was 44%, and clinical benefit rate was 61%. Median duration of response was 9.2 months; progression-free survival was 7.4 months; overall survival was not reached. Pano-RVd proved generally well-tolerated and demonstrated potential to overcome lenalidomide and/or bortezomib resistance.

MM-003: Panobinostat: A Light at the End of the Tunnel

Panobinostat, a pan histone deacetylace inhibitor, was approved by FDA in 2015 for treatment of relapsed myeloma that progressed after at least 2 lines of therapy including IMiDs. Its toxicity, mainly severe diarrhoea and cardiac events, became its limiting factor for widespread use. Its availability in India since 2018 broadened our choice to treat patients in a cost-effective manner who had otherwise exhausted all their options. Our data includes limited number of 8 patients aged 38-77yrs in single centre from 2018-2019 and was very encouraging. Panobinostat, bortezomib, and dexamethasone combination was used mainly as 5th or 6th line of treatment. Dose of panobinostat was escalated starting with 10 mg thrice weekly on 2-week on 1-week off cycle. Maximum tolerated dose was 15 mg. Bortezomib 1.3 mg/m2 given on a weekly schedule along with dexamethasone 20-40 mg based on age and comorbidities. Median number of cycles given were 6 (1-10). Results: ORR was 85% patients with reduction in their paraprotein or light chains after 1st cycle. 1 patient achieved a CR with disappearance of M band, 1 patient died shortly due to progressive disease and the remaining achieved VGPR. The duration of response varied from 6 months to a year. The main side effects were severe fatigue, grade 2 thrombocytopenia, and mild diarrhoea not requiring hospitalisation. It was impressive that even patients who failed monoclonal antibodies daratumumab and elotuzumab had an objective response. Its activity is demonstrated even in the high-risk cytogenetic group including 17p deletion. Conclusion: Our retrospective analysis confirms the efficacy of panobinostat in a relapsed refractory setting with manageable toxicities through all age groups. The dose of panobinostat was the key factor in limiting the toxicity. Considering the health-related economics in a resource constrained setting an outpatient-based treatment is a very attractive option. The cost of therapy with monoclonal antibodies is prohibitive to most of our population. With reduced hospital inpatient days and visits, the reported quality of life was much better. We aim to gather more data from other centres in our state.

Abstract TP114: Histone Deacetylase Inhibitors Panobinostat and Entinostat for Motor Recovery After Ischemic Stroke in Mice

In this study, we investigated the potential of two histone deacetylase (HDAC) inhibitors, panobinostat and entinostat, to enhance recovery of motor function after ischemic stroke in CD-1 male mice. Panobinostat, which is a pan-HDAC inhibitor, is an FDA-approved drug for certain cancers, whereas entinostat is a class-I HDAC inhibitor and is widely expected to get approval for clinical use in near future. Stroke was induced by photothrombosis and the drugs were administered intraperitoneally every other day (panobinostat at 10 mg/kg or 30 mg/kg; entinostat at 5 mg/kg or 15 mg/kg) starting from day 5 to day 15 after stroke. The control group received only vehicle following the same regimen. In addition, all drug or vehicle-treated mice exercised for 2 hours (voluntary wheel running) starting from day 9 to day 41 after stroke. Additional control groups included sham-operated animals, and mice which had stroke but were not drug/vehicle-treated or allowed to run. Motor function of the mice was evaluated by blinded investigators using gridwalk and cylinder tests before and after stroke. Acetylation of histone 3 in the peri-infarct region of the brain samples was measured by immunoblotting. Our results indicate that lower dose of both panobinostat and entinostat marginally improved motor function in mice by day 42 after stroke, although it did not reach statistical significance. Notably, this improvement trend was lost with the higher dose of both drugs which also showed some toxicity. No statistical difference was observed in running distance of mice among experimental groups. Likewise, we did not observe statistically significant difference in stroke volumes among the experimental groups. Immunoblotting experiments indicated that both panobinostat and entinostat dose-dependently increased the level of acetylated histone in the cortical, peri-infarct region of drug-treated animals compared to the non-treated groups. In summary, our results indicate that both panobinostat and entinostat do not facilitate improvement of motor function after stroke at the tested doses. However, it is likely that lower doses of these drugs may enhance recovery of motor function after stroke.

Safety and efficacy of oral panobinostat plus chemotherapy in patients aged 65 years or younger with high-risk acute myeloid leukemia

The role of histone deacetylase inhibitors in the treatment of acute myeloid leukemia (AML) is not well characterized. The current study evaluated the safety and efficacy of panobinostat in combination with idarubicin and cytarabine in newly diagnosed patients aged ≤65 years with primary or secondary high-risk AML based on cytogenetic classification. Treatment included fixed dose idarubicin (12 mg/m2/d, IV; day 1–3) and cytarabine (100 mg/m2/d, continuous IV infusion; day 1–7) and escalating oral doses of panobinostat at 15 mg, 20 mg, and 25 mg, thrice weekly starting at week 2 of a 28-day cycle. Forty-six patients were enrolled (primary AML [n = 36], secondary AML [n = 10]). The median age was 55 years. The most common all-grade AEs were diarrhea (54.3%), nausea (39.1%), vomiting, and decreased appetite (each, 21.7%), stomatitis (19.6%), and fatigue (17.4%). The overall response rate was 60.9%, 43.5% achieved a complete remission (CR), and 17.4% achieved CR with incomplete count recovery. The event-free survival at 1-year was 78.3%. Panobinostat in combination with idarubicin and cytarabine demonstrated tolerable safety and efficacy in younger patients with high-risk AML. The recommended phase 2 dose of panobinostat in this combination was 20 mg. ClinicalTrials.gov registry no: NCT01242774, and European Trial Registry EudraCT no: 2009-016809-42.

Genetic and epigenetic alterations induced by the small-molecule panobinostat: A mechanistic study at the chromosome and gene levels

Increasing evidence supports the role of genetic and epigenetic alterations in a wide variety of human diseases, including cancer. Assessment of these alterations is hence essential for estimating the hazardous effects of human exposure to medications. Panobinostat received US Food and Drug Administration’s approval in 2015 for treatment of certain tumors and its usefulness as part of a strategy to treat other diseases, such as human immunodeficiency virus infection, is currently investigated. Nevertheless, no data on in vivo genotoxical and epigenotoxical effects of panobinostat are available. The aim of the current study was to assess the genotoxical and epigenotoxical properties of panobinostat in murine bone marrow cells. Molecular mechanisms underlying these alterations were also evaluated. We show that mice treated with panobinostat doses recommended for human developed numerical chromosomal abnormalities, structural chromosomal damage, oxidative DNA damage, and DNA hypomethylation. These effects were dose-dependent. Further, panobinostat altered the expression of 23 genes implicated in DNA damage, as determined by RT² Profiler polymerase chain reaction (PCR) array, and confirmed by quantitative real-time PCR and western blotting. Collectively, these findings indicate that panobinostat exposure induces aneugenicity, clastogenicity, oxidative DNA damage, DNA hypomethylation, and down-regulation of repair gene expression, which may be responsible for panobinostat-induced genotoxical and epigenotoxical effects. Considering the potential toxicity of panobinostat, the medicinal use of panobinostat must be weighed against the risk of tumorigenesis and the demonstrated toxicity profile of panobinostat may support further development of chemotherapeutic treatments with reduced toxicity. Diminishing the metabolic liabilities associated with panobinostat exposure, and simultaneous use of panobinostat with DNA repair enhancers, are examples of strategies for drug design to reduce panobinostat carcinogenicity.

CRISPR Activation Screen for HDAC Inhibitor Resistance

Panobinostat is an oral broad-spectrum histone deacetylase inhibitor that alters gene expression via epigenetic mechanisms and function of key proteins through changes in their protein acetylation state. Panobinostate was approved a few years ago by the FDA and EMA for use in combination with bortezomib and dexamethasone in patients with multiple myeloma (MM) who have received ≥2 prior regimens, including bortezomib and an immunomodulatory drug. To study the mechanisms which regulate the response vs. resistance of MM cells to panobinostat, we performed genome-scale CRISPR activation screen of MM1S cells. MM1S cells were transduced with dCas9 and pooled lentiviral particles of the Calabrese P65-HSF CRISPR activation library consisting of 2 pooled sgRNA sub-libraries. After selection for viral transduction, cells were continuously cultured with (2 different concentration of 12.5 and 20 nM) or without panobinostat for 5 weeks, before being harvested. At that time point, dose-response curves for panobinostat treatment confirmed that the drug-exposed MM.1S cell populations of our study had become significantly less sensitive to panobinostat than treatment- naive MM.1S cells. Genomic DNA was extracted and next generation sequencing was performed to quantify the abundance of the sgRNA “barcodes” within the tumor cell populations of our study, while rank aggregation algorithms were performed to rank genes according to the magnitude and concordance of enrichment for its different sgRNAs. In MM.1S cells which had developed resistance to the lower dose (12.5 nM) of panobinostat, we observed major sgRNA enrichment (at least 4 of 6 sgRNAs, enrichment p-value <0.05, average log2 fold change of enrichment >1.5) for sgRNAs for a variety of genes, of which the most prominently enriched ones encode for the cell surface ABC transporters ABCB1 (MDR1/p-glycoprotein), to a lesser extent ABCC4 (MRP4) and even less so for ABCG2. In addition, we observed sgRNA enrichment for transcription factors, such as IRF4, POU2AF1, AFF2, IKZF3, AFF3, and RELA, or the transcriptional coregulator MTA1; Bcl2 family members such as BCL2 and BCL2L1; and chromatin remodeling genes such as KAT6A. However, in MM.1S cells which had survived the treatment with higher concentration (25 nM) of panobinostat, the genes with significant and concordant sgRNA enrichment were restricted to ABCB1, ABCC4, and IRF4. These observations indicate that the most efficient mechanism for MM cells to develop resistance to both low and higher concentrations of panobinostat is by increasing its export from the cells, with ABCB1 as the primary, but not sole, transporter which can assume this role. When we transduced MM.1S cells, which already express high levels of IRF4 transcript and protein, with lentiviral construct for IRF4 cDNA, we observed a shift to the right for the panobinostat dose-response curve, further supporting the observation that modulation of IRF4 levels in MM cells can alter the degree of MM cell sensitivity to panobinostat. Proteasome inhibitors suppress the activity of RELA and NFkappaB more broadly, while thalidomide derivatives cause degradation of IKZF3 and can decrease the IRF4 transcript levels: these results may respectively explain, at least in part, the mechanistic basis for the enhanced combined effect of panobinostat with proteasome inhibitors and the favorable clinical results obtained with panobinostat and other broad spectrum HDAC inhibitors in combination with thalidomide derivatives. Our study provides unbiased genome-scale systematic characterization of the mechanisms regulating MM cell response vs. resistance to panobinostat and identify the pronounced and dose-dependent enrichment of these resistance mechanisms for genes contributing to panobinostat export from MM cells, as well as a role for IRF4 and (primarily at lower panobinostat concentrations) for other transcription factors, chromatin remodeling genes and anti-apoptotic BCL-2 family members. These observations also support the need for a more systematic characterization of the regulation of expression of ABC transporters in MM cells; and for development of novel strategies to disrupt more comprehensively IRF4 and other transcription factors for which gain-of-function is associated with decreased responsiveness to panobinostat, with the goal of improving the impact of this agent and potentially other broad spectrum HDAC inhibitors in MM. DisclosuresMitsiades:TEVA: Research Funding; Takeda: Other: employment of a relative; EMD Serono: Research Funding; Abbvie: Research Funding; Janssen/ Johnson & Johnson: Research Funding.

Bortezomib, lenalidomide, and dexamethasone with panobinostat for front-line treatment of patients with multiple myeloma who are eligible for transplantation: a phase 1 trial

Bortezomib with lenalidomide and dexamethasone (VRd) is a standard regimen for the front-line treatment of multiple myeloma. Panobinostat is approved in combination with bortezomib and dexamethasone in patients with myeloma who 'have been given at least two previous regimens including bortezomib and an immunomodulatory agent. We aimed to determine the maximum tolerated dose of a new regimen combining VRd with panobinostat in patients with newly diagnosed multiple myeloma. In this phase 1 study, we enrolled patients from the University of Texas MD Anderson Cancer Center (Houston, TX, USA) with newly diagnosed multiple myeloma who were aged 18 years or older and eligible for autologous stem-cell transplant (ASCT) according to International Myeloma Working Group 2014 diagnostic criteria. Participants were allocated either to the dose-escalation cohort or the dose-expansion cohort. In the dose-escalation cohort, in a 3 + 3 design, patients were treated in cycles of 21 days with bortezomib (1·3 mg/m2, subcutaneously) on days 1, 4, 8, 11; lenalidomide (25 mg, orally) on days 1-14; dexamethasone (20 mg, orally) on days 1, 2, 4, 5, 8, 9, 11, and 12; and escalating doses of panobinostat (10-20 mg, orally) on days 1, 3, 5, 8, 10, and 12. The dose level exceeded the maximum tolerated dose if at any given dose more than one of three patients, or two of six patients, had a dose-limiting toxic event. In the dose-expansion cohort, patients were given the maximum tolerated dose of the drug combination as determined from the dose-escalation cohort. Patients could proceed with upfront ASCT after two to four cycles of initial therapy or store their stem cells and proceed with a delayed ASCT approach. Patients with delayed ASCT could continue therapy for up to eight cycles, followed by maintenance with lenalidomide, dexamethasone, and panobinostat at their last tolerated dose for up to 2 years. The primary objective was to determine the maximum tolerated dose of VRd with panobinostat. Safety was assessed in all patients who completed at least one cycle of therapy. This trial is registered with ClinicalTrials.gov, number NCT01440582, and is no longer recruiting participants. Between Feb 18, 2013, and June 8, 2016, 55 patients were identified as eligible for enrolment. The dose-escalation cohort comprised 12 participants. The first three (25%) patients at dose level 1 (panobinostat 10 mg) did not encounter dose-limiting toxicity. Of six (50%) patients at dose level 2 (panobinostat 15 mg), two (33%) had dose-limiting toxic events during cycle 1; one (17%) had grade 4 thrombocytopenia with bleeding and the other had grade 3 diarrhoea, thus exceeding the maximum tolerated dose. Because the maximum tolerated dose had been exceeded, three more patients were accrued to dose level 1 and these patients did not experience dose-limiting toxic events. Dose level 1 (21 day cycles of bortezomib 1·3 mg/m2 subcutaneously on days 1, 4, 8, 11; lenalidomide 25 mg orally on days 1-14; dexamethasone 20 mg orally on days 1, 2, 4, 5, 8, 9, 11, 12; and panobinostat 10 mg orally on days 1, 3, 5, 8, 10 and 12) was established as the maximum tolerated dose. The combination of VRd with panobinostat 10 mg is safe and effective in patients who are newly diagnosed with multiple myeloma and who are transplant eligible. Further studies in large randomised controlled settings are needed to confirm these results. Novartis and MD Anderson Cancer Center Support Grant.

Panobinostat inhibits the proliferation of CD34+ CD38- cells under stimulation of hematopoietic growth factors on AGM-S3 cells in juvenile myelomonocytic leukemia.

Encouraging responses to histone deacetylase inhibitors have been reported for hematologic malignancies. Here, we report effects of panobinostat and 5-azacytidine on the proliferation of juvenile myelomonocytic leukemia (JMML) CD34+ cells. We previously reported that stimulation of JMML CD34+ cells with stem cell factor and thrombopoietin on irradiated murine AGM-S3 cells led to substantial expansion of JMML CD34+ cells that contained leukemic stem cells capable of transplantation into immunodeficient mice. Using this culture system, we evaluated effects of panobinostat and 5-azacytidine on the proliferation of JMML CD34+ cells. Panobinostat dose dependently reduced the numbers of day 7 CD34+ cells generated under stimulation of hematopoietic growth factors on AGM-S3 cells in all eight patients with JMML. These patients possessed various genetic and/or karyotypic abnormalities. CD34+ CD38- cells were substantially more sensitive to panobinostat at 10 and 20nM than CD34+ CD38+ cells. Panobinostat, however, failed to influence the ability of AGM-S3 cells to stimulate JMML CD34+ cell production. In contrast to HL60 cells, apoptosis and cell cycle arrest in panobinostat-mediated inhibition were at low levels in JMML. The inhibitor also suppressed the factor-dependent proliferation of normal CD34+ cells on AGM-S3 cells. Meanwhile, no substantial inhibitory effects of 5-azacytidine on the growth of JMML CD34+ cells were observed. These results demonstrate that panobinostat directly suppresses the growth of JMML CD34+ cells, in particular CD34+ CD38- cells, regardless of the genetic abnormality type, suggesting that it is a useful antileukemic drug to target JMML stem cells at a pretransplant stage.

Treatment of HIV-Infected Individuals with the Histone Deacetylase Inhibitor Panobinostat Results in Increased Numbers of Regulatory T Cells and Limits Ex Vivo Lipopolysaccharide-Induced Inflammatory Responses.

Histone deacetylase inhibitors (HDACi) modulate the transcriptional activity of all cells, including innate and adaptive immune cells. Therefore, we aimed to evaluate immunological effects of treatment with the HDACi panobinostat in HIV-infected patients during a clinical phase IIa latency reversal trial. Using flow cytometry, we investigated changes in T cell activation (CD69, CD38, HLA-DR) and the expression of CD39 and CTLA4 on regulatory T cells (Tregs). Whole-blood stimulations were performed and cytokine responses measured using Luminex. Gene expression in purified peripheral blood mononuclear cells (PBMCs) was evaluated using an Affymetrix HTA 2.0 gene chip. We found that proportions of CD4+ and CD8+ T cells expressing CD69 increased 24h after initial panobinostat administration (P < 0.01), followed by an increase in the proportions of CD38+ HLA-DR+-coexpressing CD4+ T cells on day 4 (P = 0.02). Concurrently, proportions of Tregs increased by 40% (P = 0.003). Treg CTLA4 median fluorescent intensity (MFI) increased by 25% (P = 0.007), and CD39 MFI on CD39+ Treg increased by 12% (P = 0.02). Lipopolysaccharide (LPS)-induced inflammatory responses (interleukin-1β [IL-1β], IL-6, IL-12p40, and tumor necrosis factor alpha [TNF-α]) in whole blood were significantly downregulated 4days after initial dosing. Lastly, panobinostat induced significant changes in the overall gene expression pattern (fold change, >1.5; false-discovery-rate [FDR]-corrected P, <0.05). Importantly, measures of immune function returned to baseline after panobinostat treatment and follow-up revealed no sustained effect on overall gene expression. IMPORTANCE The effect of treatment with histone deacetylase inhibitors on the immune system in HIV-infected individuals is not clear. Analysis of results from a clinical trial in which 15 HIV-infected individuals received 12 doses of panobinostat identified a significant impact on both T cell activation status and regulatory T cell suppressive marker expression and a reduced level of monocytic responsiveness to inflammatory stimuli. These changes were substantiated by global gene expression analysis. Collectively, the results suggest that panobinostat has multiple effects on innate and adaptive immune responses. Importantly, all the effects were transient, and further panobinostat treatment did not cause persistent long-term changes in gene expression patterns in HIV-infected individuals.

EMA Review of Panobinostat (Farydak) for the Treatment of Adult Patients with Relapsed and/or Refractory Multiple Myeloma.

Farydak was approved in the European Union in combination with bortezomib and dexamethasone, for the treatment of adult patients with relapsed and/or refractory multiple myeloma who have received at least two prior regimens including bortezomib and an immunomodulatory agent (IMiD). The addition of panobinostat to bortezomib and dexamethasone resulted in a clinically meaningful and statistically significant improvement of progression-free survival compared with bortezomib and dexamethasone, and an additional therapeutic option with a new mechanism of action was considered valuable. Although the toxicity associated with panobinostat combination was significant, at the time of the marketing authorization of panobinostat, it was considered that it was acceptable and that it should be left to the clinician and the patient to decide whether the panobinostat combination is the preferred treatment option or not.

Efficacy and tolerability of the histone deacetylase inhibitor panobinostat in clinical practice.

The histone deacetylase inhibitor panobinostat has shown efficacy in phase-II and phase-III trials for multiple myeloma and has recently received market approval in combination with bortezomib and dexamethasone. Here, we retrospectively report our single center experience with panobinostat/bortezomib/dexamethasone (FVD) in a heavily pretreated patient population (n=24) with a high degree of refractoriness to proteasome inhibitors (PI) and immunomodulatory drugs (IMiD). Median age was 67years (range 49-87) and the median number of prior therapies was 5 (range 2-17). Fourteen patients (58%) had high-risk cytogenetic aberrations. Thirteen (54%) and 21 (88%) patients were refractory to PIs and IMiDs, respectively. Twelve patients (50%) were refractory to bortezomib and 7 (29%) to carfilzomib; 6 patients (25%) were refractory to both bortezomib and carfilzomib. In 21 patients evaluable for response, overall response rate (ORR; ≥PR) was 33% (7/21) and 81% (17/21) achieved at least stable disease. Median progression-free survival (PFS) and overall survival were 3.5 and 9.8months, respectively. Significant differences between bortezomib-sensitive and -refractory patients were observed. In bortezomib-sensitive patients, median PFS was 6.3months compared to 2.3months in bortezomib-refractory patients (P<.001). Median overall survival was not reached vs 4.8months (P=.046) in bortezomib-sensitive and bortezomib-refractory patients, respectively. The only patient refractory to carfilzomib but sensitive to bortezomib achieved very good partial remission and PFS of 6.3months, suggesting discrete mechanisms of resistance to different PIs. As expected, thrombocytopenia and fatigue/asthenia occurred in nearly all patients (96% and 83%, respectively). Diarrhea was observed in only 19% of patients which compares favorably with the high rates of diarrhea reported in the PANORAMA trials. With panobinostat dose reductions in 67% of patients, FVD was tolerated by the majority of patients. In conclusion, FVD showed efficacy in a heavily pretreated, high-risk multiple myeloma population with a high degree of patients refractory to novel agents including PIs.

Clinical Pharmacokinetics and Pharmacodynamics of Panobinostat

Histone deacetylase (HDAC) inhibitors cause an increase in acetylation that leads to an increase in DNA transcription and accumulation of different proteins, reducing cell proliferation and inducing cell death. Panobinostat is a first-in-line HDAC inhibitor approved for treating multiple myeloma in combination with bortezomib and dexamethasone. It is a pan-deacetylase inhibitor and therefore inhibits not only HDAC but also other deacetylases. The main mechanism of action of panobinostat is to inhibit HDAC, which causes cell cycle arrest and apoptosis, leading to it being an antineoplastic drug. Pooled data of multiple-dose studies show that an oral dose of panobinostat 20mg resulted in a maximum plasma concentration (C max) of 21.6ng/mL approximately 1h after administration, while doses between 10 and 30mg resulted in dose proportional plasma levels. The absolute bioavailability of panobinostat is 21.4%, and it is moderately bound to plasma proteins. Renal impairment does not influence the intrinsic pharmacokinetics of panobinostat, however hepatic impairment causes an increase in the plasma concentrations of this drug. Therefore, starting treatment at lower doses could be considered in patients with mild to moderate hepatic impairment. Different ethnic backgrounds have an influence on the pharmacokinetics of panobinostat; however, due to major interindividual variability, no dose adjustment is recommended. The area under the concentration-time curve of panobinostat changes significantly under cytochrome P450 (CYP) 3A4 inhibitors, CYP3A4 and CYP2D6 inducers, and P-glycoprotein inhibitors. Panobinostat itself is a CYP2D6 inhibitor, which influences the plasma levels of the CYP2D6 substrate dexamethasone. The main side effects of panobinostat are diarrhea, peripheral neuropathy, asthenia and fatigue; hematologic side effects include neutropenia, thrombocytopenia, and lymphocytopenia.

A phase 1b/2b multicenter study of oral panobinostat plus azacitidine in adults with MDS, CMML or AML with \u2a7d30% blasts

Treatment with azacitidine (AZA), a demethylating agent, prolonged overall survival (OS) vs conventional care in patients with higher-risk myelodysplastic syndromes (MDS). As median survival with monotherapy is <2 years, novel agents are needed to improve outcomes. This phase 1b/2b trial (n=113) was designed to determine the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) of panobinostat (PAN)+AZA (phase 1b) and evaluate the early efficacy and safety of PAN+AZA vs AZA monotherapy (phase 2b) in patients with higher-risk MDS, chronic myelomonocytic leukemia or oligoblastic acute myeloid leukemia with <30% blasts. The MTD was not reached; the RP2D was PAN 30 mg plus AZA 75 mg/m2. More patients receiving PAN+AZA achieved a composite complete response ([CR)+morphologic CR with incomplete blood count+bone marrow CR (27.5% (95% CI, 14.6–43.9%)) vs AZA (14.3% (5.4–28.5%)). However, no significant difference was observed in the 1-year OS rate (PAN+AZA, 60% (50–80%); AZA, 70% (50–80%)) or time to progression (PAN+AZA, 70% (40–90%); AZA, 70% (40–80%)). More grade 3/4 adverse events (97.4 vs 81.0%) and on-treatment deaths (13.2 vs 4.8%) occurred with PAN+AZA. Further dose or schedule optimization may improve the risk/benefit profile of this regimen.

A phase I trial of panobinostat with ipilimumab in advanced melanoma.

9547 Background: Immune checkpoint blockade is standard therapy for advanced melanoma (MEL), yet not all patients (pts) benefit. Panobinostat (PAN), a pan inhibitor of class I, II, and IV histone deacetylases (HDAC) is immunomodulatory, decreases tumor associated inhibitory cytokines and inhibition of effector T-cells. This dose finding study aimed to determine the safety and efficacy of escalating doses of PAN combined with ipilimumab (IPI) in advanced MEL. Methods: Eligible pts with unresectable stage 3/4 MEL, up to 3 prior lines of therapy, and adequate laboratory values were treated with oral PAN 5mg thrice weekly (TIW) plus IPI at 3mg/kg IV every 3 weeks X 4 doses, followed by maintenance PAN until progression or intolerance. Using a modified Ji design, PAN dose escalation by 5mg was planned in 3-12 pt cohorts up to a maximum dose of 20mg TIW, without intra-pt dose escalation. Dose limiting toxicity (DLT) was assessed up to day 84 from start of therapy. Results: Seventeen pts (M/F: 13/4), median age 66 yrs (48, 80) were treated with a median of 4 cycles of IPI (1,4). Of 6 pts treated at PAN 5mg TIW, there was one DLT (G3 hydronephrosis). Eleven pts received PAN 10mg TIW; of 9 evaluable for DLT, there were 3 DLTs (G3 rash, G3 diarrhea, G4 thrombocytopenia) preventing further dose escalation. Other G3 toxicities included anemia, hypophysitis, diarrhea, fatigue (all n = 2); rash, colitis, nausea, dehydration, dizziness, hypotension, ↑ lipase, ↓ sodium, &amp; ↑ glucose (all n = 1). Three pts had previous anti-PD1 therapy. The response rate was 12% (2 PRs) with 35% stable disease. One pt remains on PAN &gt; 24m since start of therapy. Median progression free- and overall survival was 2.23m (95% CI,1.57, 5.8) and 20.97m (95% CI, 8.97, NR) respectively. Biomarker analysis from peripheral blood and limited tumor biopsies pre-and on treatment examining immunoregulatory markers, including EOMES promoter acetylation in T-cells from PAN are ongoing. Conclusions: At tolerated doses, PAN does not appear to increase response to standard IPI in advanced MEL. Biomarker analyses will inform if immunomodulation by PAM improves efficacy of IPI. Combinations with selective HDAC inhibitors may be more appropriate for future study. Supported by grant P50 CA168536, Moffitt Skin Cancer SPORE. Clinical trial information: NCT02032810.