Johann Leban

Design and synthesis of novel protease inhibitors. Tripeptide α′,β′-epoxyketones as nanomolar inactivators of the proteasome

Abstract Tripeptide α′,β′-epoxyketones were prepared stereospecifically starting from Boc-[S]-phenylalanine. Diastereomer 5b inhibited the chymotrypsin-like activity of porcine endothelial cell derived proteasome at low nanomolar concentrations.

4SC-101, a novel immunosuppressive drug, inhibits IL-17 and attenuates colitis in two murine models of inflammatory bowel disease†

Background: Dihydroorotate dehydrogenase (DHODH) is a key enzyme involved in pyrimidine biosynthesis. DHODH is a known target for the treatment of autoimmune diseases. 4SC‐101 is a novel immunosuppressive drug that inhibits DHODH. A goal of our study was to examine the in vitro effects of 4SC‐101 on IL‐17 production by mononuclear cells. In addition, we evaluated the efficacy of 4SC‐101 against acute TNBS (2,4,6‐tritrobenzene sulfonic acid) and chronic dextran sodium sulfate (DSS)‐induced colitis in mice. Methods: Peripheral blood mononuclear cells (PBMCs) from healthy human donors were used to evaluate cellular proliferation and cytokine (IL‐17, TNF‐&agr;) production. The oral effects of 4SC‐101 (100 or 200 mg/kg) were examined following induction of chronic colitis by the administration of 3% DSS (4 cycles) to Balb/c mice. Morphometric and histological indices of colitis were evaluated as indicators of drug efficacy. 4SC‐101 was also administered for 6 days after the intracolonic administration of TNBS (20 mg in 50% ethanol) to female Balb/c mice. The colons were analyzed for overall macroscopic damage, ulceration, total length, distal segment weight, MPO activity, and histological pathology as indicators for the effectiveness of 4SC‐101. Results: In vitro, 4SC‐101 is a potent inhibitor of human DHODH, inhibits lymphocyte proliferation, and uniquely blocks phytohemagglutinin‐stimulated IL‐17 production by lymphocytes. In vivo, oral administration of 4SC‐101 effectively improved both chronic DSS and acute TNBS colitis in mice. In these colitis models the overall efficacy profile of 4SC‐101 was similar to that of dexamethasone. Conclusions: 4SC‐101 is a novel immunosuppressive drug with excellent potential for the treatment of intestinal inflammation. (Inflamm Bowel Dis 2010)

BW2258U89 : A GRP RECEPTOR ANTAGONIST WHICH INHIBITS SMALL CELL LUNG CANCER GROWTH

The ability of reduced peptide bond analogues of gastrin releasing peptide (GRP) to antagonize small cell lung cancer (SCLC) GRP receptors was investigated. BW462U89, BW1023U90, BW2123U89 and BW2258U89 inhibited binding of (125I-Tyr4) BN to NCI-H345 cells with IC50 values of 5, 6, 140 and 10 nM respectively. The GRP analogues had no effect on basal cytosolic Ca2+ but inhibited the increase caused by 10 nM BN. BW462U89 reversibly blocked the increase in cytosolic Ca2+ caused by BN. The GRP analogues (1 microM) inhibited NCI-H345 colony formation in the absence or presence of 10 nM BN. Also, BW2258U89 (0.4 mg/kg, s.c. daily) inhibited xenograft growth in nude mice. These data indicate that BW2258U89 inhibits SCLC growth in vitro and in vivo.

SC68896, a Novel Small Molecule Proteasome Inhibitor, Exerts Antiglioma Activity In vitro and In vivo

Purpose: Glioblastomas are among the most lethal neoplasms, with a median survival of <1 year. Modulation of the proteasome function has emerged as a novel approach to cancer pharmacotherapy. Here, we characterized the antitumor properties of SC68896, a novel small molecule proteasome inhibitor. Experimental Design: Different tumor cell lines were tested by crystal violet staining for sensitivity to SC68896, given alone or in combination with death ligands. The molecular mechanisms mediating SC68896-induced cell death and changes in cell cycle progression were assessed by immunoblot and flow cytometry. An orthotopic human glioma xenograft model in nude mice was used to examine the in vivo activity of SC68896. Results: SC68896 inhibits the proliferation of cell lines of different types of cancer, including malignant glioma. Exposure of LNT-229 glioma cells to SC68896 results in a concentration- and time-dependent inhibition of the proteasome, with a consequent accumulation of p21 and p27 proteins, cell cycle arrest, caspase cleavage, and induction of apoptosis. Using RNA interference, we show that the effect of SC68896 on glioma cells is facilitated by wild-type p53. SC68896 sensitizes glioma cells to tumor necrosis factor–related apoptosis–inducing ligand and CD95 ligand and up-regulates the cell surface expression of the tumor necrosis factor–related apoptosis–inducing ligand receptor cell death receptors 4 and 5, which may contribute to this sensitization. Intracerebral glioma–bearing nude mice treated either i.p. or intratumorally with SC68896 experience prolonged survival. Conclusions: SC68896 is the first proteasome inhibitor that exerts antiglioma activity in vivo. It may represent a novel prototype agent for the treatment of malignant gliomas and warrants clinical evaluation. (Clin Cancer Res 2009;15(21):6609–18)

A novel bombesin receptor antagonist selectively blocks the satiety action of peripherally administered bombesin.

To investigate the effect of a new, specific antagonist for bombesin receptors on the satiating action of exogenous bombesin, adult male rats were adapted to a nondeprivation test regimen with daily access to a palatable liquid food. In a prefeeding paradigm, rats received intraperitoneal injections of the bombesin receptor antagonist, BW2258U89 (6.25, 25, 50, or 100 micrograms kg-1) or vehicle 20 min before, and then a second injection of either bombesin (4 micrograms kg-1), gastrin-releasing peptide (GRP; 16 micrograms kg-1), the C-terminal octapeptide of cholecystokinin (CCK-8; 4 micrograms kg-1), or vehicle 5 min before a 2-h feeding test. BW2258U89 pretreatment antagonized the satiating actions of bombesin and GRP18-27 in a very potent, dose-related manner, but did not antagonize the satiating action of CCK-8. These differential results with BW2258U89 are consistent with prior results showing the potency of this antagonist for bombesin receptor-mediated effects in visceral systems; in addition, they demonstrate the selectivity of the compound for the satiating actions of peripherally administered bombesin and bombesin-like peptides.

BW1023U90: A new GRP receptor antagonist for small-cell lung cancer cells

Abstract Gastrin-releasing peptide (GRP) receptor antagonists were synthesized and their ability to interact with small-cell lung cancer (SCLC) cells determined. [125I]BW1023U90, bound with high affinity (Kd = 2 nM) to a single class of sites (Bmax = 55 fmol/mg protein) using SCLC cell line NCI-H345. [125I]BW1023U90 binding was time dependent and reversible even at 37°C as the ligand was minimally internalized. Specific [125I]BW1023U90 binding was inhibited with high affinity by GRP as well as bombesin (BB) but not neuromedin B (NMB). BW1023U90 inhibited the ability of BB to elevate cytosolic Ca2+ and increase the growth of SCLC cells. A BW1023U90 analogue, BW2258U89 (10 μg/day, SC) slowed SCLC xenograft formation in nude mice and [125I]BW1023U90 localized to SCLC tumors 1 h after injection into nude mice. BW2258U89 (4% by weight) was placed in microspheres and slowly released over a 3-week period in nude mice bearing SCLC xenografts. The microspheres containing BW2258U89 strongly inhibited SCLC growth in vivo. A radioimmunoassay was developed for the GRP receptor antagonists and the rabbit antiserum cross-reacted totally with BW2258U89 or BW1023U90. BW2258U89 immunoreactivity (5 nM) was detected in the plasma of nude mice containing the microspheres after 1 week. These data suggest that GRP receptor antagonists bind to receptors on SCLC tumors.

Assessment of drug candidates for broad-spectrum antiviral therapy targeting cellular pyrimidine biosynthesis.

Currently available antiviral drugs frequently induce side-effects or selection of drug-resistant viruses. We describe a novel antiviral principle based on targeting the cellular enzyme dihydroorotate dehydrogenase (DHODH). In silico drug design and biochemical evaluation identified Compound 1 (Cmp1) as a selective inhibitor of human DHODH in vitro (IC50 1.5±0.2nM). Crystallization data specified the mode of drug-target interaction. Importantly, Cmp1 displayed a very potent antiviral activity that could be reversed by co-application of uridine or other pyrimidine precursors, underlining the postulated DHODH-directed mode of activity. Human and animal cytomegaloviruses as well as adenoviruses showed strong sensitivity towards Cmp1 in cell culture-based infection systems with IC50 values in the low micromolar to nanomolar range. Particularly, broad inhibitory activity was demonstrated for various types of laboratory and clinically relevant adenoviruses. For replication of human cytomegalovirus in primary fibroblasts, antiviral mode of activity was attributed to the early stage of gene expression. A mouse in vivo model proved reduced replication of murine cytomegalovirus in various organs upon Cmp1 treatment. These findings suggested Cmp1 as drug candidate and validated DHODH as a promising cellular target for antiviral therapy.

Difluoro-dioxolo-benzoimidazol-benzamides As Potent Inhibitors of CK1δ and ε with Nanomolar Inhibitory Activity on Cancer Cell Proliferation

Deregulation of CK1 (casein kinase 1) activity can be involved in the development of several pathological disorders and diseases such as cancer. Therefore, research interest in identifying potent CK1-specific inhibitors is still increasing. A previously published potent and selective benzimidazole-derived CK1δ/ε-specific inhibitor compound with significant effects on several tumor cell lines was further modified to difluoro-dioxolo-benzoimidazole derivatives displaying remarkable inhibitory effects and increased intracellular availability. In the present study, we identified two heterocyclic molecules as new CK1-specific inhibitor compounds with favorable physicochemical properties and notable selectivity in a kinome-wide screen. Being compared to other CK1 isoforms, these compounds exhibited advanced isoform selectivity toward CK1δ. Moreover, newly designed compounds showed increased growth inhibitory activity in a panel of different tumor cell lines as determined by analyses of cell viability and cell cycle distribution. In summary, presented lead optimization resulted in new highly selective CK1δ-specific small molecule inhibitors with increased biological activity.

The Novel, Proteasome-Independent NF-κB Inhibitor V1810 Induces Apoptosis and Cell Cycle Arrest in Multiple Myeloma and Overcomes NF-κB–Mediated Drug Resistance

Evidence is increasing that aberrant NF-κB activation is crucial for multiple myeloma pathophysiology and a promising target for new antimyeloma therapies. In this study, we assessed the in vitro antimyeloma activity of the novel NF-κB inhibitor V1810. Pharmacokinetics and toxicity were studied in vivo. In mice, V1810 plasma concentrations of 10 μmol/L can be reached without relevant toxicity. At this concentration, V1810 potently induces apoptosis in all four multiple myeloma cell lines assessed (IC50 = 5–12 μmol/L) as well as in primary multiple myeloma cells (IC50 = 5–40 μmol/L). Apoptosis induced by V1810 is associated with proteasome-independent inhibition of NF-κB signaling (41% relative reduction), downregulation of Mcl-1, and caspase 3 cleavage. In OPM2, U266, and RPMI-8226 cells, induction of apoptosis is accompanied by cell cycle arrest. Western blots revealed downregulation of Cdk4 as well as cyclin D1 (U266) or cyclin D2 (OPM2, NCI-H929, RPMI-8226), but not cyclin D3. Consistently, retinoblastoma protein was found to be hypophosphorylated. Furthermore, V1810 reverses NF-κB activation induced by the genotoxic drugs melphalan and doxorubicin. V1810 and melphalan synergistically decrease multiple myeloma cell viability. Taken together, the novel, proteasome-independent NF-κB inhibitor V1810 induces apoptosis and cell cycle arrest in multiple myeloma cells at a concentration range that can be achieved in vivo. Moreover, V1810 reverses NF-κB activation by alkylating drugs and overcomes NF-κB–mediated resistance to melphalan. Mol Cancer Ther; 9(2); 300–10

Hemodynamic characterization of a novel neuropeptide Y receptor antagonist.

Defining the roles of the vasoconstrictor peptide neuropeptide Y (NPY) in the cardiovascular system is difficult due to lack of availability of specific NPY receptor antagonists. We report the in vivo NPY receptor blocking actions of a novel nonapeptide dimer, 1229U91 {(IleGluProDprTyrArgLeuArgTyrNH(2)(2)}, and describe its hemodynamic effects. In anesthetized normotensive rats, 1229U91 produced significant and dose-dependent reductions in NPY-reduced hemodynamic responses. 1229U91 (3-30 nmol/kg intravenously, i.v.) attenuated the pressor response (34 +/- 6-84 +/- 1%) and the increases in renal vascular resistance (RVR, 56 +/- 9-94 +/- 2%) produced by NPY (1 nmol/kg i.v.). Intravenous norepinephrine (NE)-induced hemodynamic responses were not altered by 1229U91. 1229U91 also produced dose-dependent inhibition of NPYinduced vasoconstrictor responses in anesthetized dogs and spontaneously hypertensive rats (SHR). These data demonstrate that 1229U91 is a selective NPY receptor antagonist. 1229U91 had no effect on resting hemodynamic variables in these preparations. In conscious SHR, 1229U91 did not produce significant changes in blood pressure (BP) or heart rate (HR) over a wide dose-range (15-1,500 nmol/kg i.v.). Lack of effect of the NPY receptor antagonist in SHR suggests that NPY does not contribute to the maintenance of BP in this hypertension model.