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BackgroundNicotinamide (NAM), an allosteric inhibitor of NAD-dependent enzymes, has been shown to preserve cell function and prevent differentiation in ex vivo cell culture. GDA-201 is an investigational natural killer (NK) cell immunotherapy derived from allogeneic donors and expanded using IL-15 and NAM. In previous preclinical studies, NAM led to increased homing and cytotoxicity, preserved proliferation, and enhanced tumor reduction of NK cells. In a phase I clinical trial, treatment with GDA-201 showed tolerability and clinical responses in patients with refractory non-Hodgkin lymphoma (NHL) (Bachanova, et. al., Blood 134:777, 2019). While NAM is known to affect cellular metabolism and participate in 510 enzymatic reactions −in 66 as an inhibitor or activator− its mechanism of action and role in GDA-201 cytotoxicity is unknown.MethodsIn order to define the network of intracellular interactions that leads to the GDA-201 phenotype, flow-cytometry, next generation sequencing (NGS), and liquid chromatography–mass spectrometry (LC-MS)-based metabolite quantification were performed on NK cells cultured for 14 days with IL-15 and human serum in the presence or absence of NAM (7 mM). Artificial Intelligence (AI) machine learning analysis was applied by Pomicell in order to analyze the data using the Pomicell databases supporting data extracted from multiple origins including scientific articles organized using natural language processing tools. AI training was done using a combined algorithm designed to blindly explain and predict the transcriptomic and metabolomic (omics) profile.ResultsOmics analyses defined 1,204 differentially expressed genes, and 100 significantly modified metabolites in the presence of NAM. An in silico model was created that successfully predicted the experimental data in 83% of the cases. Upregulation of TIM-3 expression in GDA-201 was predicted to be mediated by inhibition of IL-10 and SIRT3, via CREB1/HLA-G signaling and adrenoceptor beta 2 (ADRB2) upregulation. Adenosine metabolite reduction supports this and suggests dopaminergic activation of NK cytotoxicity. Upregulation of CD62L in the presence of NAM was predicted to be mediated by transcription factor Dp-1 (TFDP1) via dihydrofolate reductase (DHFR) activation and intracellular folic acid reduction. Interferon-gamma and CASP3 modulation (via JUN and MCL1, respectively), via PPARa inhibition, support that finding.ConclusionsIn conclusion, AI machine learning of transcriptome and metabolome data revealed multiple pleiotropic metabolic pathways modulated by NAM. These data serve to further elucidate the mechanism by which NAM enhances cell function, leading to the observed cytotoxicity and potency of GDA-201.Ethics ApprovalWe hereby declare that the collection of the Apheresis units in the three participating institutes (sites) has been done under an approved clinical study that meets the following requirements:1. Ethics approval has been obtained from the local EC at each of the sites, prior to any study related activities.2. The working procedures of the EC at the sites for conduct of clinical studies are in due compliance with local regulations (Israeli Ministry of Health) and provisions of Harmonized International Guidelines for Good Clinical Practice, namely: ICH-GCP.3. Sites follow EC conditions & requirements in terms of submissions, notifications, and approval renewals. 4. Participants gave Informed Consent (approved by the EC) before taking part in the study.5. Informed Consent has been approved by the ECs. The Israeli template of Informed Consent is in used and it includes study specific information (e.g. study goal, design, method, duration, risks, etc.). Name of the Institute Name of the EC/IRB EC Study No.Hadassah Medical Center Helsinki Committee 0483-16-HMORambam Health Care Campus Helsinki Committee 0641-18-RMBIchilov Sourasky Medical Center Tel-Aviv Helsinki Committee 0025-17-TLV

Adoptive transfer of NK cells is a promising immunotherapeutic modality, however limited NK cell persistence and proliferation in vivo have historically been barriers to clinical success. Nicotinamide (NAM), an allosteric inhibitor of NAD-dependent enzymes, has been shown to preserve cell function and prevent differentiation in ex vivo culture of NK (NAM-NK) and other cells. Clinical responses were observed in a Phase 1 trial of NAM-NK (GDA-201) in patients with refractory non-Hodgkin lymphoma (Bachanova, et. al., Blood 134:777, 2019). We now use transcriptional and metabolic profiling to characterize the mechanisms underlying the activity of NAM-NK. CD3 negative lymphocytes obtained from healthy donors were cultured for 14 days with IL-15 in the presence or absence of NAM (7 mM). Next generation sequencing (NGS), liquid chromatography-mass spectrometry (LC-MS)-based metabolite quantification, and glycolytic/mitochondrial respiration measurements were performed. Transcriptome and pathway enrichment analyses were performed with Ingenuity Pathway Analysis software. Extracted cellular and medium metabolites were analyzed on a Thermo Q-Exactive Plus mass spectrometer coupled with a Vanquish UHPLC system. Extracellular acidification (ECAR) and oxygen consumption rates (OCR) were quantified using a Seahorse Extracellular Flux Analyzer. Glycolysis/citric acid cycle (TCA) rates were measured using isotope-labelled glucose incorporation assays. Transcriptome analyses defined 1,204 differentially expressed (DE) genes in NAM-NK vs. control NK. Biological/functional enrichment and pathway analyses of DE-genes predicted upregulation of cell cycle, DNA replication (CDK4/CDKN2D, CyclinD/E, MAD2L), RNA transcription, translation (SMN1/2, ABCF1, EIF4B, RPL13, RPS6), protein synthesis (EIF2, PABPC1, SOS, 60S complex) mitochondrial energy metabolism (NDUFB8, ATP5G2/E, COX7B/C) migration, homing (CD62L, CD44, DNAM1), and cytokine/chemokine response (IL18R, CXCR3, CCR5, XCL1, SOCS3, LFA1) pathways, with concomitant downregulation of cell exhaustion, senescence (BATF1, FOXP1, STAT1, CD86, LGALS9, LAG3), apoptosis, necrosis (CASP1, MDM2, IKK3), stress response (CALR, HSP90, HSPH1), and lymphoid cellular maturation (IL-2Ra, CD40L, GATA3) pathways in NAM-NK. Metabolomic analyses showed a significant increase of intracellular NAD, NADH, NADP, NADPH, high-energy triphosphates (ATP, UTP, GTP) and overall energy charge ([ATP+0.5*ADP]/[ATP+ADP+AMP]) in NAM-NK. Cellular metabolic fitness analyses revealed increased basal and ATP-linked respiration, mitochondrial maximal respiratory capacity, and glycolytic capacity in NAM-NK compared to control NK. In addition, NAM increased the rate of glucose incorporation into TCA cycle intermediates (acetyl-CoA, succinyl-CoA), consistent with a more rapid glycolysis rate, increased TCA cycling, and improved glucose consumption efficiency. Taken together, results of transcriptome, metabolomic, mitochondrial respiration, and glycolytic rate analyses suggest that NAM pleiotropically modulates key cellular metabolic functions in ex vivo-expanded NK cells, resulting in increased response to cytokine stimulation and enhanced potency. NAM inhibits differentiation, cellular stress, and exhaustion pathways that are typically activated in culture. Moreover, NAM increases cellular metabolic fitness, energy charge, and efficiency of glucose consumption, potentially imparting a protective effect against oxidative stress in the tumor microenvironment. These data offer insight into the mechanism of improved persistence, proliferation, and cytotoxicity observed in in vivo and clinical studies of GDA-201. Disclosures Yackoubov: Gamida Cell: Current Employment. Pato: Gamida Cell: Current Employment. Rifman: Gamida Cell: Current Employment. Cohen: Gamida Cell: Current Employment. Hailu: Gamida Cell: Current Employment. Persi: Gamida Cell: Current Employment. Berhani-Zipori: Gamida Cell: Current Employment. Edri: Gamida Cell: Current Employment. Peled: Biokine Therapeutics Ltd: Current Employment; Gamida Cell: Research Funding. Cichocki: Gamida Cell: Research Funding; Fate Therapeutics, Inc: Patents & Royalties, Research Funding. Rabinowitz: Gamida Cell: Research Funding. Lodie: Gamida Cell: Current holder of stock options in a privately-held company, Ended employment in the past 24 months. Adams: Gamida Cell: Current Employment. Simantov: Gamida Cell: Current Employment. Geffen: Gamida Cell: Current Employment.

Significance Standard of care for metastatic castration-resistant prostate cancer (mCRPC) mainly relies on suppression of androgen receptor (AR) signaling. This approach has no lasting benefit due to the emergence of resistance mechanisms, such as ligand-independent splicing variant AR-V7. A metabolic feature of mCRPC is the upregulation of de novo lipogenesis to provide substrates and fuel for metastatic spread. Whether increased levels of fats affect AR signaling to promote an aggressive disease remains to be determined. Using a selective and potent inhibitor of fatty acid synthase we demonstrate that suppression of this key enzyme inhibits AR, most importantly AR-V7, and reduces mCRPC growth. Our findings offer a therapeutic opportunity for mCRPC and a potential mechanism to overcome resistance to AR inhibitors., A hallmark of prostate cancer progression is dysregulation of lipid metabolism via overexpression of fatty acid synthase (FASN), a key enzyme in de novo fatty acid synthesis. Metastatic castration-resistant prostate cancer (mCRPC) develops resistance to inhibitors of androgen receptor (AR) signaling through a variety of mechanisms, including the emergence of the constitutively active AR variant V7 (AR-V7). Here, we developed an FASN inhibitor (IPI-9119) and demonstrated that selective FASN inhibition antagonizes CRPC growth through metabolic reprogramming and results in reduced protein expression and transcriptional activity of both full-length AR (AR-FL) and AR-V7. Activation of the reticulum endoplasmic stress response resulting in reduced protein synthesis was involved in IPI-9119–mediated inhibition of the AR pathway. In vivo, IPI-9119 reduced growth of AR-V7–driven CRPC xenografts and human mCRPC-derived organoids and enhanced the efficacy of enzalutamide in CRPC cells. In human mCRPC, both FASN and AR-FL were detected in 87% of metastases. AR-V7 was found in 39% of bone metastases and consistently coexpressed with FASN. In patients treated with enzalutamide and/or abiraterone FASN/AR-V7 double-positive metastases were found in 77% of cases. These findings provide a compelling rationale for the use of FASN inhibitors in mCRPCs, including those overexpressing AR-V7.

Acute myeloid leukemia (AML) is the most common form of acute leukemia with dismal long-term prognosis with age. The most aggressive subtype of AML is MLL-AML that is characterized by translocations of the mixed-lineage leukemia gene (MLL)and resistance to conventional chemotherapy. Cyclin dependent kinase 9 (CDK9) plays a crucial role in the MLL-driven oncogenic transcription, and hence, inhibiting activity of CDK9 has been proposed as a promising strategy for treatment of AML. We investigated the therapeutic potential of CDKI-73, one of the most potent CDK9 inhibitors, against a panel of AML cell lines and samples derived from 97 patients. CDKI-73 induced cancer cells undergoing apoptosis through transcriptional down regulation of anti-apoptotic proteins Bcl-2, Mcl-1 and XIAP by majorly targeting CDK9. Contrastively, it was relatively low toxic to the bone marrow cells of healthy donors. In MV4–11 xenograft mouse models, oral administration of CDKI-73resulted in a marked inhibition of tumor growth (p < 0.0001) and prolongation of animal life span (P < 0.001) without causing body weight loss and other overt toxicities. The study suggests that CDKI-73 can be developed as a highly efficacious and orally deliverable therapeutic agent for treatment of AML. Refereed/Peer-reviewed

Historical efforts at expansion of umbilical cord blood (UCB) derived CD34+ hematopoietic stem cells (HSCs) ex vivo with cytokines yielded large numbers of progenitors for transplantation but impaired their long-term engraftment ability. We used nicotinamide (NAM), an allosteric inhibitor of NAD-enzymes, to create omidubicel, an investigational cell therapy designed to improve the expansion of CD34+ HSCs for bone marrow transplant. A Phase 1/2 clinical study of omidubicel in patients with high-risk hematologic malignancies showed rapid neutrophil engraftment and a more favorable immune reconstitution profile in patients compared to historical controls.1 We hypothesized that NAM treatment maintains the stemness and engraftment potential of omidubicel, which is associated with clinical benefit.2 We performed transcriptome, transcription factor (TF), and pathway analysis by next generation sequencing (NGS) to discern the mechanism of action of NAM and to elucidate the pathways leading to the preservation of engraftment after ex vivo expansion of omidubicel compared to CD34+ cells grown in the absence of NAM. Transcriptome analysis revealed that treatment of CD34+ cells with cytokines alone (stem cell factor [SCF], thrombopoietin [TPO], IL-6, and FLT3 ligand) led to an increase in pathways responsible for cell proliferation and differentiation, apoptotic stress, and production of reactive oxygen species (ROS), and matrix metalloproteinases (MMPs), all of which were attenuated by NAM. TF enrichment analysis of NAM-upregulated genes and downregulated genes demonstrated that NAM modulated several TFs critically involved in pathways of HSC cell self-renewal, differentiation, apoptosis and migration. Specifically, NF-kB, C-Jun, LXR/RXR and PPARα/RXRα, and AMPK-mTor signaling were all reduced in NAM-treated CD34+ cells compared to controls. Reduced expression of key genes involved in the production of ROS and reactive nitrogen species (RNS) including NADPH-oxidase-related genes (CYBB, NCF2 and NCF4) and iNOS, suggested that NAM-expanded CD34+ cells were less exposed to oxygen and nitrogen free radical stress than controls. NAM also downregulated the expression of several matrix metalloproteinases (MMP) genes including MMP7, MMP9, MMP12 and MMP19. NAM-induced downregulation of MMPs may explain the increase in engraftment in patients receiving omidubicel. Pathway analysis of differentially expressed (DE) genes was conducted using ingenuity (IPA) software. IPA analysis of DE genes showed significant downregulation of growth factor activating pathways including SCF, TPO, FLT, and GM-CSF and Endothelin-1 and P2Y Purigenic Receptor, which was confirmed by a reduction in cell cycling rates of labeled cells. IPA analysis also pointed to genes in 3 key cellular pathways that were downregulated by NAM: stress induction of apoptosis, production of ROS and RNS, and production of MMPs. NAM treatment also uniquely upregulated genes linked to cellular metabolism including the Sirtuin family genes, TCA cycle genes, and HIF1a. Interestingly, NAM upregulated genes responsible for telomerase expression further validating our hypothesis that NAM preserves cell stemness. In summary, NGS transcriptome analysis revealed that ex vivo expansion of UCB derived CD34+ cells in the presence of NAM attenuated TFs responsible for proliferation and differentiation of stem cells. In addition, NAM treatment downregulated genes regulating the production ROS, RNS, and MMPs and upregulated genes controlling metabolism and senescence, thus allowing for the expansion of CD34+ cells with preserved function and long-term engraftment ability. Our gene expression data leads to a better understanding of the mechanisms by which NAM modulates CD34+ cells in omidubicel to preserve their function. These data provide further scientific rationale for the favorable clinical engraftment and patient outcomes observed in the Phase 1/2 clinical study of omidubicel.1 An international, randomized, multi-center Phase 3 study of omidubicel in patients with high-risk hematologic malignancies is underway.2 [1]Horwitz M.E., et. al., J Clin Oncol. 2019 Feb 10;37(5):367-374. [2] ClinicalTrials.gov identifier NCT02730299. Disclosures Lodie: Gamida Cell: Employment, Equity Ownership. Adams:Gamida Cell: Employment, Equity Ownership. Yackoubov:GAMIDA CELL: Employment, Other: unexecuted shares of the company . Peled:Gamida Cell: Employment, Equity Ownership.

Colorectal cancer (CRC) remains one of the most lethal human malignancies, and pursuit of new therapeutic targets for treatment has been a major research focus. Cyclin‐dependent kinase 9 (CDK9), which plays a crucial role in transcription, has emerged as a target for cancer treatment. CDKI‐73, one of the most potent and pharmacologically superior CDK9 inhibitors, has demonstrated excellent anti‐tumour efficacy against several types of cancers. In this study, we evaluated its therapeutic potential against CRC. CDKI‐73 elicited high cytotoxicity against all colon cancer cell lines tested. Cell cycle and apoptosis analysis in HCT 116 and HT29 cells revealed that CDKI‐73 induced cell death without accumulation of DNA at any phase of the cell cycle. Moreover, it caused depolarisation of mitochondrial membrane, leading to caspase‐independent apoptosis. Knockdown by shRNA demonstrated the CDK9‐targeted mechanism of CDKI‐73, which also affected the Mnk/eIF4E signalling axis. In addition, RT‐qPCR analysis showed that CDKI‐73 down‐regulated multiple pro‐survival factors at the mRNA level. Its in vivo anti‐tumour efficacy was further evaluated in Balb/c nude mice bearing HCT 116 xenograft tumours. CDKI‐73 significantly inhibited tumour growth (***P < 0.001) without overt toxicity. Analysis of the tumour tissues collected from the xenografted animals confirmed that the in vivo anti‐tumour efficacy was associated with CDK9 targeting of CDKI‐73. Overall, this study provides compelling evidence that CDKI‐73 is a promising drug candidate for treating colorectal cancer. Refereed/Peer-reviewed

// Peng Li 1 , Sarah Diab 1 , Mingfeng Yu 1 , Julian Adams 1 , Saiful Islam 1 , Sunita K.C. Basnet 1 , Hugo Albrecht 1 , Robert Milne 1 , Shudong Wang 1 1 Centre for Drug Discovery and Development, Sansom Institute for Health Research, and School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, South Australia 5001, Australia Correspondence to: Shudong Wang, email: shudong.wang@unisa.edu.au Keywords: Mnk inhibitor, acute myeloid leukemia, cytarabine, combination therapy Received: May 03, 2016 Accepted: July 11, 2016 Published: July 23, 2016 ABSTRACT Cytarabine (Ara-C) is a first line clinical therapeutic agent for treatment of acute myeloid leukemia (AML). However, this therapy is limited due to high rate of resistance and relapse. Recent research has revealed that the poor prognosis and resistance to Ara-C in AML were associated with its abnormally activated MAPK pathways. In this study, we showed a strong synergistic effect of Ara-C with either our Mnk inhibitor (MNKI-8e) or short hairpin RNA (shRNA) mediated knockdown of Mnks in MV4-11 AML cells. We investigated the underlying mechanisms for this synergism. We showed that both MNKI-8e and Mnk shRNAs enhanced the ability of Ara-C to induce apoptosis. We found that Ara-C increased the phosphorylation of Erk1/2, p38 and eIF4E, which correlated with an enhanced level of anti-apoptotic Mcl-1 protein. Inhibition of Mnk activity suppressed the Ara-C-induced MAPK activity, and thus enhanced apoptosis in MV4-11 cells. Taken together, our study suggests that MAPK-Mnk-eIF4E pathway plays a critical role in Ara-C-treated MV4-11 cells and targeting Mnk may be a promising therapeutic strategy for sensitizing leukemic cells to Ara-C therapy.

The formation of the d-homocyclopamine ring system in IPI-926 is the key step in its semisynthesis and proceeds via a chemoselective cyclopropanation followed by a stereoselective acid-catalyzed carbocation rearrangement. In order to perform large-scale cyclopropanation reactions, we developed new iodomethylzinc bis(aryl)phosphate reagents that were found to be both effective and safe. These soluble reagents can be prepared under mild conditions and are stable during the course of the reaction. Importantly, they have favorable energetics relative to other cyclopropanating agents such as EtZnCH2I. Herein, we describe the process optimization studies that led to successful large-scale production of the d-homocyclopamine core necessary for IPI-926.

We chronicle and dissect the history of the field of Experimental Microbial Evolution, beginning with work by Monod. Early research was largely carried out by microbiologists and biochemists, who used experimental evolutionary change as a tool to understand structure-function relationships. These studies attracted the interest of evolutionary biologists who recognized the power of the approach to address issues such as the tempo of adaptive change, the costs and benefits of sex, parallelism, and the role which contingency plays in the evolutionary process. In the 1980s and 1990s, an ever-expanding body of microbial, physiological and biochemical data, together with new technologies for manipulating microbial genomes, allowed such questions to be addressed in ever-increasing detail. Since then, technological advances leading to low-cost, high-throughput DNA sequencing have made it possible for these and other fundamental questions in evolutionary biology to be addressed at the molecular level.

ON01910.Na is a highly effective anticancer agent that induces mitotic arrest and apoptosis. Clinical studies with ON01910 in cancer patients have shown efficacy along with an impressive safety profile. While ON01910 is highly active against cancer cells, it has a low oral availability and requires continuous intravenous infusion or multiple gram doses to ensure sufficient drug exposure for biological activity in patients. We have identified two novel series of styrylsulfonyl-methylpyridines. Lead compounds 8, 9a, 18 and 19a are highly potent mitotic inhibitors and selectively cytotoxic to cancer cells. Impressively, these compounds possess excellent pharmaceutical properties and two lead drug candidates 9a and 18 demonstrated antitumor activities in animal models. Refereed/Peer-reviewed

1. IPI-926 is a novel semisynthetic cyclopamine derivative that is a potent and selective Smoothened inhibitor that blocks the hedgehog signal transduction pathway. 2. The in vivo clearance of IPI-926 is low in mouse and dog and moderate in monkey. The volume of distribution is high across species. Oral bioavailability ranges from moderate in monkey to high in mouse and dog. Predicted human clearance using simple allometry is low (24 L h(-1)), predicted volume of distribution is high (469 L) and predicted half-life is long (20 h). 3. IPI-926 is highly bound to plasma proteins and has minimal interaction with human α-1-acid glycoprotein. 4. In vitro metabolic stability ranges from stable to moderately stable. Twelve oxidative metabolites were detected in mouse, rat, dog, monkey and human liver microsome incubations and none were unique to human. 5. IPI-926 is not a potent reversible inhibitor of CYP1A2, 2C8, 2C9 or 3A4 (testosterone). IPI-926 is a moderate inhibitor of CYP2C19, 2D6 and 3A4 (midazolam) with KI values of 19, 16 and 4.5 µM, respectively. IPI-926 is both a substrate and inhibitor (IC50 = 1.9 µM) of P-glycoprotein. 6. In summary, IPI-926 has desirable pre-clinical absorption, distribution, metabolism and excretion properties.

Targeting tumour-infiltrating suppressive myeloid cells with a selective PI3Kγ inhibitor overcomes resistance to checkpoint blockade therapy in various mouse myeloid-rich tumour models. Therapeutic blockade of immune checkpoints with antibodies against CTLA-4 and PD-1 has proved effective against some cancer types, but clinical benefit has been limited to a subset of patients. Here Olivier De Henau et al. show that resistance to checkpoint blockade is associated with a high level of infiltration by suppressive myeloid cells in various mouse tumour models. In addition, targeting the myeloid-derived suppressor cells with a selective inhibitor of the γ isoform of phosphoinositide 3-kinase (PI3Kγ) increases sensitivity to checkpoint blockade therapy in a melanoma mouse model. Recent clinical trials using immunotherapy have demonstrated its potential to control cancer by disinhibiting the immune system. Immune checkpoint blocking (ICB) antibodies against cytotoxic-T-lymphocyte-associated protein 4 or programmed cell death protein 1/programmed death-ligand 1 have displayed durable clinical responses in various cancers1. Although these new immunotherapies have had a notable effect on cancer treatment, multiple mechanisms of immune resistance exist in tumours. Among the key mechanisms, myeloid cells have a major role in limiting effective tumour immunity2,3,4. Growing evidence suggests that high infiltration of immune-suppressive myeloid cells correlates with poor prognosis and ICB resistance5,6. These observations suggest a need for a precision medicine approach in which the design of the immunotherapeutic combination is modified on the basis of the tumour immune landscape to overcome such resistance mechanisms. Here we employ a pre-clinical mouse model system and show that resistance to ICB is directly mediated by the suppressive activity of infiltrating myeloid cells in various tumours. Furthermore, selective pharmacologic targeting of the gamma isoform of phosphoinositide 3-kinase (PI3Kγ), highly expressed in myeloid cells, restores sensitivity to ICB. We demonstrate that targeting PI3Kγ with a selective inhibitor, currently being evaluated in a phase 1 clinical trial (NCT02637531), can reshape the tumour immune microenvironment and promote cytotoxic-T-cell-mediated tumour regression without targeting cancer cells directly. Our results introduce opportunities for new combination strategies using a selective small molecule PI3Kγ inhibitor, such as IPI-549, to overcome resistance to ICB in patients with high levels of suppressive myeloid cell infiltration in tumours.

Several Hsp90 (heat shock protein 90) inhibitors are currently under clinical evaluation as anticancer agents. However, the correlation between the duration and magnitude of Hsp90 inhibition and the downstream effects on client protein degradation and cancer cell growth inhibition has not been thoroughly investigated. To investigate the relationship between Hsp90 inhibition and cellular effects, we developed a method that measures drug occupancy on Hsp90 after treatment with the Hsp90 inhibitor IPI-504 in living cells and in tumor xenografts. In cells, we find the level of Hsp90 occupancy to be directly correlated with cell growth inhibition. At the molecular level, the relationship between Hsp90 occupancy and Hsp90 client protein degradation was examined for different client proteins. For sensitive Hsp90 clients (e.g. HER2 (human epidermal growth factor receptor 2), client protein levels directly mirror Hsp90 occupancy at all time points after IPI-504 administration. For insensitive client proteins, we find that protein abundance matches Hsp90 occupancy only after prolonged incubation with drug. Additionally, we investigate the correlation between plasma pharmacokinetics (PK), tumor PK, pharmacodynamics (PD) (client protein degradation), tumor growth inhibition, and Hsp90 occupancy in a xenograft model of human cancer. Our results indicate Hsp90 occupancy to be a better predictor of PD than either plasma PK or tumor PK. In the nonsmall cell lung cancer xenograft model studied, a linear correlation between Hsp90 occupancy and tumor growth inhibition was found. This novel binding assay was evaluated both in vitro and in vivo and could be used as a pharmacodynamic readout in the clinic.

IPI-504 (retaspimycin hydrochloride) is an Hsp90 inhibitor that is the subject of multiple clinical trials for the treatment of cancer. IPI-504 is an aqueous soluble (>200 mg/ml) hydroquinone hydrochloride salt of 17-(allylamino)-17-demethoxygeldanamycin (17-AAG), a quinone derivative also undergoing clinical evaluation, albeit with suboptimal formulations that address its inferior aqueous solubility (∼50 µg/ml). IPI-504 interconverts with 17-AAG in vivo through oxidation-reduction reactions that result in a dynamic redox equilibrium. The development challenges associated with redox active molecules are significant due to the pH, oxygen, and temperature sensitivities associated with such chemotypes. The API and sterile drug product manufacturing processes thus warrant the monitoring and control of these key variables. Furthermore, the pharmaceutical development challenges associated with cancer agents that are often fast-tracked due to unmet medical needs mandate a rapid development cycle with associated regulatory hurdles. Drug Dev Res 71: 429–438, 2010. © 2010 Wiley-Liss, Inc.

The structure of aldehyde reductase (ALR1) in ternary complex with the coenzyme NADPH and [5-(3-carboxymethoxy-4-methoxybenzylidene)-2,4-dioxothiazolidin-3-yl]acetic acid (CMD), a potent inhibitor of aldose reductase (ALR2), was determined at 1.99A resolution. The partially disordered inhibitor formed a tight network of hydrogen bonds with the active site residues (Tyr50 and His113) and coenzyme. Molecular modelling calculations and inhibitory activity measurements of CMD and [5-(3-hydroxy-4-methoxybenzylidene)-2,4-dioxothiazolidin-3-yl]acetic acid (HMD) indicated that pi-stacking interactions with several conserved active site tryptophan residues and hydrogen-bonding interactions with the non-conserved C-terminal residue Leu300 in ALR2 (Pro301 in ALR1) contributed to inhibitor selectivity. In particular for the potent inhibitor CMD, the rotameric state of the conserved residue Trp219 (Trp220 in ALR1) is important in forming a pi-stacking interaction with the inhibitor in ALR2 and contributes to the difference in the binding of the inhibitor to the enzymes.

Herein is reported the synthesis of a novel class of hedgehog antagonists derived from cyclopamine. The acid sensitive D-ring of cyclopamine was homologated utilizing a sequence of chemoselective cyclopropanation and stereoselective acid-catalyzed rearrangement. Further modification of the A/B-ring homoallylic alcohol to the conjugated ketone led to the discovery of new cyclopamine analogues with improved pharmaceutical properties and in vitro potency (EC 50) ranging from 10 to 1000 nM.

Heat shock protein 90 (Hsp90) is an emerging therapeutic target of interest for the treatment of cancer. Its role in protein homeostasis and the selective chaperoning of key signaling proteins in cancer survival and proliferation pathways has made it an attractive target of small molecule therapeutic intervention. 17-Allylamino-17-demethoxygeldanamycin (17-AAG), the most studied agent directed against Hsp90, suffers from poor physical-chemical properties that limit its clinical potential. Therefore, there exists a need for novel, patient-friendly Hsp90-directed agents for clinical investigation. IPI-504, the highly soluble hydroquinone hydrochloride derivative of 17-AAG, was synthesized as an Hsp90 inhibitor with favorable pharmaceutical properties. Its biochemical and biological activity was profiled in an Hsp90-binding assay, as well as in cancer-cell assays. Furthermore, the metabolic profile of IPI-504 was compared with that of 17-AAG, a geldanamycin analog currently in clinical trials. The anti-tumor activity of IPI-504 was tested as both a single agent as well as in combination with bortezomib in myeloma cell lines andin vivoxenograft models, and the retention of IPI-504 in tumor tissue was determined. In conclusion, IPI-504, a potent inhibitor of Hsp90, is efficacious in cellular and animal models of myeloma. It is synergistically efficacious with the proteasome inhibitor bortezomib and is preferentially retained in tumor tissues relative to plasma. Importantly, it was observed that IPI-504 interconverts with the known agent 17-AAGin vitroandin vivovia an oxidation-reduction equilibrium, and we demonstrate that IPI-504 is the slightly more potent inhibitor of Hsp90.

Proteasome inhibitors, a novel class of chemotherapeutic agents, enhance the antitumor efficacy of anthracyclines in vitro and in vivo. We therefore sought to determine the maximum tolerated dose (MTD) and dose-limiting toxicities of bortezomib and pegylated liposomal doxorubicin (PegLD). Bortezomib was given on days 1, 4, 8, and 11 from 0.90 to 1.50 mg/m2 and PegLD on day 4 at 30 mg/m2 to 42 patients with advanced hematologic malignancies. Grade 3 or 4 toxicities in at least 10% of patients included thrombocytopenia, lymphopenia, neutropenia, fatigue, pneumonia, peripheral neuropathy, febrile neutropenia, and diarrhea. The MTD based on cycle 1 was 1.50 and 30 mg/m2 of bortezomib and PegLD, respectively. However, due to frequent dose reductions and delays at this level, 1.30 and 30 mg/m2 are recommended for further study. Pharmacokinetic and pharmacodynamic studies did not find significant drug interactions between these agents. Antitumor activity was seen against multiple myeloma, with 8 of 22 evaluable patients having a complete response (CR) or near-CR, including several with anthracycline-refractory disease, and another 8 having partial responses (PRs). One patient with relapsed/refractory T-cell non-Hodgkin lymphoma (NHL) achieved a CR, whereas 2 patients each with acute myeloid leukemia and B-cell NHL had PRs. Bortezomib/PegLD was safely administered in this study with promising antitumor activity, supporting further testing of this regimen.

Constitutive activation of the NF-κB pathway is required for survival of the activated B cell–like (ABC) subgroup of diffuse large B-cell lymphoma (DLBCL). Here we show that a small molecule IκB kinase (IKK) inhibitor, PS-1145, and related compounds are toxic for ABC DLBCL cell lines but not for cell lines derived from the other prevalent form of DLBCL, germinal center B cell–like DLBCL. Treatment of ABC lines with these inhibitors rapidly induced a series of gene expression changes that were attributable to cessation of constitutive IKK activity, similar to changes induced by acute expression of genetic inhibitors of NF-κB, confirming the effectiveness and specificity of this compound. Before cell death, inhibition of IKK also induced features of apoptosis and an arrest in the G1 phase of the cell cycle. To test further the specificity of this toxicity, an inducible form of NF-κB was created by fusing the p65 NF-κB subunit with the ligand-binding domain of the estrogen receptor (p65-ERD). In the presence of tamoxifen, p65-ERD reversed the toxicity of IKK inhibition and restored expression of many NF-κB target genes. Another subgroup of DLBCL, primary mediastinal B-cell lymphoma (PMBL), also expresses NF-κB target genes, and treatment of a PMBL cell line with an IKK inhibitor was toxic and induced gene expression changes of a distinct group of NF-κB target genes. These studies validate the NF-κB pathway as a promising therapeutic target in ABC DLBCL, PMBL, and other lymphomas that depend on the activity of NF-κB for survival and proliferation.

The dipeptide boronic acid analogue VELCADE (Bortezomib; formerly known as PS-341, LDP-341 and MLM341) is a potent and selective inhibitor of the proteasome, a multicatalytic enzyme that mediates many cellular regulatory signals by degrading regulatory proteins or their inhibitors. The proteasome is, thus, a potential target for pharmacological agents. Bortezomib, the first proteasome inhibitor to reach clinical trials, has shown in vitro and in vivo activity against a variety of malignancies, including myeloma, chronic lymphocytic leukemia, prostate cancer, pancreatic cancer, and colon cancer. The drug is rapidly cleared from the vascular compartment, but a novel pharmacodynamic assay has shown that bortezomib--mediated proteasome blockade is dose-dependent and reversible. Based on phase I studies demonstrating that bortezomib has manageable toxicities in patients with advanced cancers, phase II trials have been initiated for both solid and hematological malignancies.

Since the publication of the complete sequence of the genome of Saccharomyces cerevisiae, a number of comprehensive investigations have been initiated to gain insight into cellular function. The focus of these studies has been to identify genes essential for survival in specific environments or those that when mutated cause gross phenotypic defects in growth. Here we describe Ty1-based mutational approaches designed to identify genes, which when mutated generate evolutionarily significant phenotypes causing small but positive increments on fitness. As expected, Ty1 mutations with a positive fitness effect were in the minority. However, mutations in two loci, one inactivating FAR3 and one upstream of CYR1, identified in evolving populations, were shown to have small but significantly positive fitness effects.

BACKGROUND Bortezomib, a boronic acid dipeptide, is a novel proteasome inhibitor that has been shown in preclinical and phase 1 studies to have antimyeloma activity. METHODS In this multicenter, open-label, nonrandomized, phase 2 trial, we enrolled 202 patients with relapsed myeloma that was refractory to the therapy they had received most recently. Patients received 1.3 mg of bortezomib per square meter of body-surface area twice weekly for 2 weeks, followed by 1 week without treatment, for up to eight cycles (24 weeks). In patients with a suboptimal response, oral dexamethasone (20 mg daily, on the day of and the day after bortezomib administration) was added to the regimen. The response was evaluated according to the criteria ofthe European Group for Blood and Marrow Transplantation and confirmed by an independent review committee. RESULTS Of 193 patients who could be evaluated, 92 percent had been treated with three or more ofthe major classes of agents for myeloma, and in 91 percent, the myeloma was refractory to the therapy received most recently. The rate of response to bortezomib was 35 percent, and those with a response included 7 patients in whom myeloma protein became undetectable and 12 in whom myeloma protein was detectable only by immuno-fixation. The median overall survival was 16 months, with a median duration of response of 12 months. Grade 3 adverse events included thrombocytopenia (in 28 percent of patients), fatigue (in 12 percent), peripheral neuropathy (in 12 percent), and neutropenia (in 11 percent). Grade 4 events occurred in 14 percent of patients. CONCLUSIONS Bortezomib, a member of a new class of anticancer drugs, is active in patients with relapsed multiple myeloma that is refractory to conventional chemotherapy.

The proteasome is a multisubunit enzyme complex that plays a central role in the regulation of proteins that control cell-cycle progression and apoptosis, and has therefore become an important target for anticancer therapy. Before a protein is degraded, it is first flagged for destruction by the ubiquitin conjugation system, which ultimately results in the attachment of a polyubiquitin chain on the target protein. The proteasome's 19S regulatory cap binds the polyubiquitin chain, denatures the protein, and feeds the protein into the proteasome's proteolytic core. The proteolytic core is composed of 2 inner beta rings and 2 outer alpha rings. The 2 beta rings each contain 3 proteolytic sites named for their trypsin-like, post-glutamyl peptide hydrolase-like (PGPH) (i.e., caspase-like), or chymotrypsin-like activity. Inhibition of the proteasome results in cell-cycle arrest and apoptosis. In in vitro and in vivo animal studies, inhibition of the proteasome via bortezomib (VELCADE; formerly, PS-341, LDP-341, and MLN341) had antitumor activity against numerous tumor types either alone or in combination with conventional chemotherapeutic agents; these results provided the rationale for a broad clinical trial program. Bortezomib is currently in phase III trials for myeloma and is in early clinical development for numerous other tumor types.

Objective: Pilot study to assess the safety and effectiveness of Dermagraft® when used in conjunction with multi-layer compression bandage therapy (Profore™) compared with multilayer compression only in the treatment of chronic venous leg ulcers. Design: Open-label, prospective, multicentre, randomized, controlled clinical trial. Methods: Patients aged at least 18 years with leg ulceration of venous aetiology were screened for inclusion in the trial. Patients with arterial disease (ankle brachial pressure index Results: In all 53 patients were randomized, of whom 47 completed the study per protocol. At 12 weeks complete healing of the ulcer, analysed by 'intention-to-treat' (ITT) was 15% using Profore alone, 7% using single application Dermagraft and Profore (Group 3), compared with 38% using multiple applications of Dermagraft and Profore (Groups 1 and 2). At study discontinuation, the median percentage reduction in wound area was 81.4% for Group 1, 88.6% for Group 2, 59.4% for Group 3 and 78.1% for Group 4. No major safety issues were identified during the course of the study. Conclusions: The results of the pilot study indicate that four pieces of Dermagraft are the optimal application frequency to take forward to further clinical trials. Further studies are required to confirm these data, and these should be powered to detect whether there are statistical differences in healing rates and safety between different regimens.

Highly regulated intracellular proteolysis is necessary for cell-cycle progression and cell division. The ubiquitin–proteasome pathway (UPP) plays a central role in the degradation of proteins and has therefore become an important, novel therapeutic target for diseases involving cell proliferation, most notably cancer. Proteasome inhibitors were initially used as research tools in cell biology to characterise the properties of the UPP. It was later determined that proteasome inhibition induced cell-cycle arrest and programmed cell death (apoptosis) in cancer cells in vitro and could inhibit tumour growth in animal xenograft models. Several classes of molecules that have proteasome-inhibiting characteristics have been studied. The dipeptidyl boronic acid bortezomib (Velcade™ Millennium Pharmaceuticals, Inc.), formerly known as PS-341, LDP-341 and MLN-341, is a potent and specific inhibitor of the proteasome that holds promise as a potential human therapeutic. It is the first proteasome inhibitor to be exam...

Secondary brain injury due to ischemia includes the infiltration of leukocytes into the brain parenchyma mediated by activation of nuclear factor-κB (NF-κB), which is activated by proteasome degradation. Neuroprotection with the proteasome inhibitor MLN519 has previously been reported to decrease ischemic brain injury in rats. The authors used higher doses of MLN519 to evaluate the neuroprotection therapeutic window after 24 hours of brain injury in rats as correlated to proteasome levels, activated NF-κB immunoreactivity, and leukocyte infiltration. Male Sprague-Dawley rats were subjected to 2-hour middle cerebral artery occlusion (MCAO) and recovery. MLN519 or vehicle was administered after injury with a single injection given in delayed increments of 2 hours (i.e., 4, 6, or 8 hours after MCAO). Treatment with MLN519 up to 6 hours after MCAO (4 hours after reperfusion) effectively reduced neuronal and astrocytic degeneration, decreased cortical infarct volume, and increased neurologic recovery. These effects were related to >80% reductions in blood proteasome levels, reduced neutrophil infiltration, and a decrease in activated NF-κB immunoreactivity. This improved neuroprotection profile and antiinflammatory effect of MLN519 provides an exciting avenue for potential treatment of focal ischemic brain injury in humans.

PURPOSE: To determine the maximum-tolerated dose (MTD), dose-limiting toxicity (DLT), and pharmacodynamics (PD) of the proteasome inhibitor bortezomib (previously known as PS-341) in patients with refractory hematologic malignancies. PATIENTS AND METHODS: Patients received PS-341 twice weekly for 4 weeks at either 0.40, 1.04, 1.20, or 1.38 mg/m2, followed by a 2-week rest. The PD of PS-341 was evaluated by measurement of whole blood 20S proteasome activity. RESULTS: Twenty-seven patients received 293 doses of PS-341, including 24 complete cycles. DLTs at doses above the 1.04-mg/m2 MTD attributed to PS-341 included thrombocytopenia, hyponatremia, hypokalemia, fatigue, and malaise. In three of 10 patients receiving additional therapy, serious reversible adverse events appeared during cycle 2, including one episode of postural hypotension, one systemic hypersensitivity reaction, and grade 4 transaminitis in a patient with hepatitis C and a substantial acetaminophen ingestion. PD studies revealed PS-341 induced 20S proteasome inhibition in a time-dependent manner, and this inhibition was also related to both the dose in milligrams per meter squared, and the absolute dose of PS-341. Among nine fully assessable patients with heavily pretreated plasma cell dyscrasias completing one cycle of therapy, there was one complete response and a reduction in paraprotein levels and/or marrow plasmacytosis in eight others. In addition, one patient with mantle cell lymphoma and another with follicular lymphoma had shrinkage of nodal disease. CONCLUSION: PS-341 was well tolerated at 1.04 mg/m2 on this dose-intensive schedule, although patients need to be monitored for electrolyte abnormalities and late toxicities. Additional studies are indicated to determine whether incorporation of dose/body surface area yields a superior PD model to dosing without normalization. PS-341 showed activity against refractory multiple myeloma and possibly non-Hodgkin’s lymphoma in this study, and merits further investigation in these populations.

The proteasome is a multicatalytic protease, present in all eukaryotic cells, that is primarily responsible for intracellular protein degradation. By destroying regulatory proteins or their inhibitors, the proteasome influences many cellular regulatory signals and is thus a potential target for pharmacological agents. The dipeptide boronic acid analogue PS-341 is a potent and selective proteasome inhibitor in clinical trials for a variety of tumor types. In vitro and in vivo (murine xenograft) studies show that PS-341 has activity against a variety of malignancies, including myeloma, chronic lymphocytic leukemia, prostate cancer, pancreatic cancer, breast cancer and colon cancer.

The 26S proteasome is a promising new target for breast cancer therapy. The degradation of proteins by the proteasome is an essential metabolic process, and inhibition of the proteasome results in cell-cycle arrest and apoptosis. However, cancer cells and proliferating blood vessels appear to be particularly sensitive to the effects of proteasome inhibition. Studies carried out in breast cancer cells and murine xenograft models of breast cancer have demonstrated the potent antitumor effects of proteasome inhibition in this disease. Proteasome inhibition interferes with many cell signaling pathways, including those involved in the development and progression of breast cancer. The potent and selective proteasome inhibitor bortezomib (VELCADE; formerly known as PS-341) is particularly promising as a potential anticancer agent. PS-341 is the first proteasome inhibitor to be extensively studied in murine models of cancer and to progress to clinical trials in cancer patients. Preliminary clinical data from patients with a range of malignancies indicate that the drug effectively inhibits proteasome activity at doses associated with manageable toxicity. Early clinical trials are currently recruiting participants for the analysis of PS-341 activity in breast cancer.

Increasing evidence suggests that tissue transglutaminase (tTGase; type II) is externalized from cells, where it may play a key role in cell attachment and spreading and in the stabilization of the extracellular matrix (ECM) through protein cross-linking. However, the relationship between these different functions and the enzyme's mechanism of secretion is not fully understood. We have investigated the role of tTGase in cell migration using two stably transfected fibroblast cell lines in which expression of tTGase in its active and inactive (C277S mutant) states is inducible through the tetracycline-regulated system. Cells overexpressing both forms of tTGase showed increased cell attachment and decreased cell migration on fibronectin. Both forms of the enzyme could be detected on the cell surface, but only the clone overexpressing catalytically active tTGase deposited the enzyme into the ECM and cell growth medium. Cells overexpressing the inactive form of tTGase did not deposit the enzyme into the ECM or secrete it into the cell culture medium. Similar results were obtained when cells were transfected with tTGase mutated at Tyr(274) (Y274A), the proposed site for the cis,trans peptide bond, suggesting that tTGase activity and/or its tertiary conformation dependent on this bond may be essential for its externalization mechanism. These results indicate that tTGase regulates cell motility as a novel cell-surface adhesion protein rather than as a matrix-cross-linking enzyme. They also provide further important insights into the mechanism of externalization of the enzyme into the extracellular matrix.

Some retroviruses contain monoubiquitinated Gag and do not bud efficiently from cells treated with proteasome inhibitors, suggesting an interaction between the ubiquitin-proteasome system and retrovirus assembly. We examined equine infectious anemia virus (EIAV) particles and found that approximately 2% of the p9 Gag proteins are monoubiquitinated, demonstrating that this Gag protein interacts with an ubiquitinating activity. Different types of proteasome inhibitors were used to determine if proteasome inactivation affects EIAV release from chronically infected cells. Pulse-chase immunoprecipitation and time course immunoblot analyses showed that proteasome inactivation slightly decreased virus release (at most a twofold effect), while it did not affect Gag processing. These results contrast with those obtained with other viruses which are sensitive to these inhibitors. This suggests that, although its Gag is monoubiquitinated, the requirements for EIAV release are somewhat different from those for retroviruses that are sensitive to proteasome inhibitors. Lentiviruses and type C retroviruses assemble in association with the host plasma membrane, forming a bud that is released from the cell to produce a virion (46). The late assembly domain (L) within Gag is crucial for the efficient release of the budding virus from the plasma membrane (42). Three different sequences have been shown to possess L domain function: PPPY, found in Rous sarcoma virus (RSV) (51, 52), murine leukemia virus (MuLV), (54), and Mason-Pfizer monkey virus (53); PTAP, found in human immunodeficiency virus type 1 (HIV-1) (presumably P[T/S]AP for HIV-2 and simian immunodeficiency virus [SIV]) (11, 18); and YPDL, found in equine infectious anemia virus (EIAV) (34). Deletion or replacement of these sequences causes virions to mostly remain attached to the plasma membrane by a thin tether and to fail to separate from the cell. These L domain sequences can interact directly with cellular proteins (8, 9, 12, 13, 19, 35, 45), suggesting potential cellular partners for virus budding. Despite these findings, the pathway(s) used by retroviruses for budding is mostly unknown, though recent results suggest that components of the vacuolar protein sorting pathway might be used by HIV-1 (9). Experiments with several retroviruses have shown that Gag interacts with the ubiquitination pathway and that efficient budding requires active proteasomes (47). Here we examine EIAV for interactions with the ubiquitin (Ub)-proteasome system. EIAV particles contain free Ub and Ub-Gag conjugates. For

Dysregulation of cellular transcription and translation is a fundamental hallmark\ud of cancer. As CDK9 and Mnks play pivotal roles in the regulation of RNA transcription\ud and protein synthesis, respectively, they are important targets for drug development.\ud We herein report the cellular mechanism of a novel CDK9 inhibitor CDKI-73 in an\ud ovarian cancer cell line (A2780). We also used shRNA-mediated CDK9 knockdown\ud to investigate the importance of CDK9 in the maintenance of A2780 cells. This study\ud revealed that CDKI-73 rapidly inhibited cellular CDK9 kinase activity and downregulated\ud the RNAPII phosphorylation. This subsequently caused a decrease in the\ud eIF4E phosphorylation by blocking Mnk1 kinase activity. Consistently, CDK9 shRNA\ud was also found to down-regulate the Mnk1 expression. Both CDKI-73 and CDK9 shRNA\ud decreased anti-apoptotic proteins Mcl-1 and Bcl-2 and induced apoptosis. The study\ud confirmed that CDK9 is required for cell survival and that ovarian cancer may be\ud susceptible to CDK9 inhibition strategy. The data also implied a role of CDK9 in eIF4Emediated\ud translational control, suggesting that CDK9 may have important implication\ud in the Mnk-eIF4E axis, the key determinants of PI3K/Akt/mTOR- and Ras/Raf/MAPKmediated\ud tumorigenic activity. As such, CDK9 inhibitor drug candidate CDKI-73 should\ud have a major impact on these pathways in human cancers.

The 26S proteasome regulates protein turnover in eukaryotic cells. This is relevant in human cancer because the cell cycle, tumor growth, and survival are governed by a large repertoire of intracellular proteins that are regulated by the ubiquitin-mediated proteasome degradative pathway. In the development of new antitumor agents whose mechanisms are distinct from currently available therapies, we have discovered a potent, selective inhibitor of the proteasome: PS-341, a dipeptide boronic acid. Compared with normal cells, cancer cells--and specifically myeloma--treated with PS-341 are differentially sensitive to proteasome inhibition and apoptosis. A unique feature of PS-341 involves the inhibition of nuclear factor (NF)-kappaB activation through stabilization of the inhibitor protein IkappaB. Myeloma cells depend on NF-kappaB-mediated transcription of cytokine growth factor interleukin-6, angiogenesis through vascular endothelial growth factor, and the cell adhesion molecule VCAM-1 for adherence of the plasma cells to the stromal tissue in bone marrow. At low nanomolar concentrations, PS-341 is highly effective in abrogating the transcription of these genes, which are under the direct regulation of NF-kappaB. Moreover, PS-341 appears to synergize with dexamethasone in myeloma cell culture, which may prove to be of additional benefit clinically. The safety profile in phase I trials of PS-341 in patients with cancer appears encouraging. Because proteasome inhibition with PS-341 results in potent antitumor activity in vitro, PS-341 may offer a promising new approach to treating otherwise fatal malignancy.

Background and Purpose — The proteasome inhibitor PS-519 blocks activation of nuclear factor-κB, a major mediator of inflammation. We tested the hypothesis that combination treatment of recombinant human tissue plasminogen activator (rhtPA) and PS-519 extends the therapeutic window for treatment of stroke with rhtPA without increasing incidence of hemorrhagic transformation. Methods — The middle cerebral artery (MCA) of male Wistar rats (n=56) was occluded by an embolus. After embolization, animals were randomly divided into the following groups: PS-519 treatment groups: PS-519 was given at 2, 4, or 6 hours after MCA occlusion; rhtPA treatment groups: rhtPA was given at 2 or 4 hours after MCA occlusion; combination treatment groups: PS-519 and rhtPA were given at 2, 4, or 6 hours after MCA occlusion; control group: the same volume of saline was given at 2 hours after MCA occlusion. Results — Administration of PS-519 alone at 2 or 4 hours, but not 6 hours, significantly ( P P P Conclusions — Our data suggest that combination treatment with PS-519 and rhtPA extends the neuroprotective effect to at least 6 hours after embolization.

The 26S proteasome degrades proteins that regulate transcription factor activation, cell cycle progression, and apoptosis. In cancer, this may allow for uncontrolled cell division, promoting tumor growth, and spread. We examined whether selective inhibition of the 26S proteasome with PS-341, a dipeptide boronic acid analogue, would block proliferation and induce apoptosis in human pancreatic cancer. Proteasome inhibition significantly blocked mitogen (FCS) induced proliferation of BxPC3 human pancreatic cancer cells in vitro, while arresting cell cycle progression and inducing apoptosis by 24 h. Accumulation of p21Cip1-Waf-1, a cyclin dependent kinase (CDK) inhibitor normally degraded by the 26S proteasome, occurred by 3 h and correlated with cell cycle arrest. When BxPC3 pancreatic cancer xenografts were established in athymic nu/nu mice, weekly administration of 1 mg/kg PS-341 significantly inhibited tumor growth. Both cellular apoptosis and p21Cip1-Waf-1 protein levels were increased in PS-341 treated xenografts. Inhibition of tumor xenograft growth was greatest (89%) when PS-341 was combined with the tumoricidal agent CPT-11. Combined CPT-11/PS-341 therapy, but not single agent therapy, yielded highly apoptotic tumors, significantly inhibited tumor cell proliferation, and blocked NF-κB activation indicating this systemic therapy was effective at the cancer cell level. 26S proteasome inhibition may represent a new therapeutic approach against this highly resistant and lethal malignancy. J. Cell. Biochem. 82: 110–122, 2001. © 2001 Wiley-Liss, Inc.

Since its isolation in 1991, (+)-lactacystin (1) has attracted considerable attention among leading synthesis laboratories due to its highly selective and potent inhibition of the 20S proteasome. The syntheses of this molecule described herein demonstrate several important strategies in the area of acyclic stereocontrol including the use of chiral metal enolate and chiral allylmetal-based bond construction methods. Several analogs of 1 and of the related β-lactone 2 are also presented, which provide insight into the structure activity relationship relative to the molecule’s inhibition of the 20S proteasome. Additionally, an analog of 2 is discussed regarding its clinical evaluation for the treatment of cerebral ischemia and stroke.

Background and Purpose —Reperfusion brain injury after cerebral ischemia is associated with a developing inflammatory response at the site of infarction. Proteasome inhibitors block nuclear factor-κB activation and provide anti-inflammatory effects in several animal models of peripheral inflammation. We tested the novel proteasome inhibitor PS519 in a rat model of transient focal ischemia to establish its pharmacodynamics as a neuroprotection treatment and related effects on leukocyte infiltration. Methods —Rats were subjected to 2 hours of focal cerebral ischemia by means of the filament method of middle cerebral artery occlusion (MCAo). After either 22 or 70 hours of reperfusion, infarct size was measured and neurological function, electroencephalographic (EEG) activity, and/or neutrophil and macrophage infiltration was quantified. PS519 was administered in a single intravenous bolus at 2 hours after MCAo. In addition, the therapeutic window for PS519 was estimated by delaying treatment for 4 or 6 hours after MCAo. Results —Dose-response analysis of infarct volume at 24 hours revealed that PS519 neuroprotection approached 60%, and clinical evaluations showed significant improvements in neurological function and EEG activity. Neutrophil infiltration at 24 hours was also significantly decreased in cortical and striatal infarcted tissue of PS519-treated rats. Delaying the PS519 treatment up to 4 hours continued to result in significant neuroprotection. In the 72-hour injury model, infarction was reduced 40% by PS519, and significant improvements in neurological function and EEG recovery were again measured. Considerable reductions in both neutrophil and macrophage infiltration were evident. Conclusions —PS519 mitigates infarction and improves neurological recovery in brain-injured rats, an effect in part caused by a reduction in the leukocyte inflammatory response.

Background: PS-341, a selective inhibitor of the proteasome, currently is under evaluation as an anticancer agent in multiple phase I clinical trials. In animal-model studies, PS-341 was rapidly removed from the vascular compartment and distributed widely, quickly approaching the limits of detection. An accurate pharmacodynamic assay has been developed as an alternative or complement to pharmacokinetic measurements.Methods: Fluorogenic kinetic assays for both the chymotryptic and tryptic activities of the proteasome have been optimized for both whole blood and blood cells. Using the ratio of these activities and the catalytic mechanism of the proteasome, we developed a novel method of calculating percentage of inhibition, using two structurally unrelated inhibitors (PS-341 and lactacystin).Results: This ratio method was demonstrated to be sensitive (detection limit of 13% inhibition with 10 μg of cell lysate), specific to the proteasome (PS-341 provides >98% inhibition), accurate (112% analyte recovery), and precise (0% ± 5% inhibition at 0 nmol/L PS-341 and 74.5% ± 1.7% inhibition at 200 nmol/L PS-341). Using these assays, we found that both erythrocytes and leukocytes contain proteasome at 3 μmol/L. Pharmacodynamic results for PS-341 obtained from the whole-blood ratio method were comparable to those using leukocytes determined by another method.Conclusions: The described assay provides a reliable method for studying the pharmacodynamics of proteasome inhibitors and is now in use in concurrent phase I clinical trials with PS-341.

The ubiquitin proteasome pathway is a highly conserved intracellular pathway for the degradation of proteins. Many of the short-lived regulatory proteins which govern cell division, growth, activation, signaling and transcription are substrates that are temporally degraded by the proteasome. In recent years, new and selective inhibitors of the proteasome have been employed in cell culture systems to examine the anti-tumor potential of these agents. This review covers the chemistry of selected proteasome inhibitors, possible mechanisms of action in cell culture and the in vivo examination of proteasome inhibitors in murine and human xenograft tumor models in mice. One inhibitor, PS-341, has recently entered Phase I clinical trials in cancer patients with advanced disease to further test the potential of this approach.

Herein, we describe a new convergent synthesis of a more potent analogue of clasto-lactacystin β-lactone (2), PS-519 compound 4, which is currently in preclinical development for the treatment of i...

Background: Nuclear factor-κB (NF-κB) is a critical transcription factor required for the regulation of many genes involved in inflammatory responses to noxious stimuli. On activation, NF-κB induces the transcription of numerous proinflammatory cytokines, enzymes, and cellular adhesion molecules. Blockade of the proteasome with selective inhibitors attenuates the effects of NF-κB, leading to suppression of the inflammatory response. Objective: We sought to determine whether proteasome inhibitors would be active in a model of asthma. Methods: The mouse delayed-type hypersensitivity model was used to screen a panel of compounds for in vivo activity. The proteasome inhibitor, PS-519, was shown to be the most active in this model and was selected for further development. Allergen-induced pulmonary eosinophilia in Brown Norway rats was used subsequently to determine anti-inflammatory activity in an animal model. Results: Direct administration of PS-519 into the lungs significantly reduced leukocyte numbers, particularly the selective increase in eosinophils. Because steroids are the mainstay anti-inflammatory therapy in asthma, and data is available to suggest their possible interaction to suppress the activation of NF-κB, rats were also treated by inhalation with combinations of a steroid and the proteasome inhibitor. In both the delayed-type hypersensitivity and the animal eosinophil model, low doses of proteasome inhibitors were shown to be effective when given with low doses of steroids. Conclusion: Taken together, the present data suggest that proteasome inhibition may represent a novel strategy for the treatment of inflammatory lung diseases such as asthma. (J Allergy Clin Immunol 1999;104:294-300.)