Phase 1 trial of navitoclax and sorafenib in patients with relapsed or refractory solid tumors with hepatocellular carcinoma expansion cohort.

Navitoclax (ABT-263) is an oral BCL2 homology-3 mimetic that binds with high affinity to pro-survival BCL2 proteins, resulting in apoptosis. Sorafenib, an oral multi kinase inhibitor also promotes apoptosis and inhibits tumor angiogenesis. The efficacy of either agent alone is limited; however, preclinical studies demonstrate synergy with the combination of navitoclax and sorafenib. In this phase 1 study, we evaluated the combination of navitoclax and sorafenib in a dose escalation cohort of patients with refractory solid tumors, with an expansion cohort in hepatocellular carcinoma (HCC). Maximum tolerated dose (MTD) was determined using the continual reassessment method. Navitoclax and sorafenib were administered continuously on days 1 through 21 of 21-day cycles. Ten patients were enrolled in the dose escalation cohort and 15 HCC patients were enrolled in the expansion cohort. Two dose levels were tested, and the MTD was navitoclax 150 mg daily plus sorafenib 400 mg twice daily. Among all patients, the most common grade 3 toxicity was thrombocytopenia (5 patients, 20%): there were no grade 4 or 5 toxicities. Patients received a median of 2 cycles (range 1-36 cycles) and all patients were off study treatment at data cut off. Six patients in the expansion cohort had stable disease, and there were no partial or complete responses. Drug-drug interaction between navitoclax and sorafenib was not observed. The combination of navitoclax and sorafenib did not increase induction of apoptosis compared with navitoclax alone. Navitoclax plus sorafenib is tolerable but showed limited efficacy in the HCC expansion cohort. These findings do not support further development of this combination for the treatment of advanced HCC. This phase I trial was conducted under ClinicalTrials.gov registry number NCT01364051.

Peripheral blood blast rate of clearance is an independent predictor of clinical response and outcomes in acute myeloid leukaemia.

The day 14 bone marrow aspirate and biopsy (D14BM) is regularly used to predict achievement of complete remission (CR) with induction chemotherapy in acute myeloid leukemia (AML), however its utility has been questioned. Clearance of peripheral blood blasts (PBB) may serve as an early measure of chemosensitivity. PBB rate of clearance (PBB-RC) was calculated for treatment-naive AML patients (n = 164) undergoing induction with an anthracycline and cytarabine (7+3) and with detectable PBB at diagnosis. PBB-RC was defined as the percentage of the absolute PBB count on the day of diagnosis that was cleared with each day of therapy, on average, until D14 or day of PBB clearance. Each 5% increase in PBB-RC approximately doubled the likelihood of D14BM clearance (OR = 1·81; 95% CI: 1·24-2·64, P < 0·005). PBB-RC was also associated with improved CR rates (OR per 5% = 1·97; 95% CI: 1·27-3·01, P < 0·005) and overall survival (OS) [hazard ratio (HR) per 5% = 0·67; 95% CI: 0·52-0·87]. African American patients had poorer OS adjusted for PBB-RC (HR = 2·18; 95% CI: 1·13-4·23), while race was not associated with D14BM or CR rate. PBB-RC during induction chemotherapy is predictive of D14BM clearance, CR, and OS, and can therefore serve as a prognostic marker for clinical outcomes in AML.

Optimizing pegylated asparaginase use: An institutional guideline for dosing, monitoring, and management.

The incorporation of L-asparaginase and pegylated asparaginase into pediatric-inspired regimens has conferred a survival advantage in treatment of adults with acute lymphoblastic leukemia. Use of asparaginase products requires careful prevention, monitoring, and management of adverse effects including hypersensitivity, hepatotoxicity, pancreatitis, coagulopathy, and thrombosis. Currently, there is limited published literature to offer guidance on management of these toxicities. At the University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center, a standard of practice guideline was created to prevent and manage asparaginase-related adverse events. By sharing our long-term experience with asparaginase products and clinical management of asparaginase-induced toxicities, this article aims to improve patient safety and optimize treatment outcomes.

Relapsed Philadelphia Chromosome-Positive Pre-B-ALL after CD19-Directed CAR-T Cell Therapy Successfully Treated with Combination of Blinatumomab and Ponatinib.

Adults with relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL) treated with conventional chemotherapy have dismal outcomes. Novel immunotherapies targeting CD19, including the bispecific T-cell engager blinatumomab and chimeric antigen-receptor T (CAR-T) cells, have revolutionized the treatment of R/R B-ALL. Robust response rates to CAR-T cell therapy after blinatumomab have recently been reported, but it is unknown whether blinatumomab can be effective following failure of anti-CD19 CAR-T cell therapy. Herein, we describe a patient with Philadelphia chromosome-positive B-ALL who relapsed after CD19-directed CAR-T therapy, but subsequently responded to the combination of blinatumomab and the tyrosine kinase inhibitor ponatinib, with the achievement of a complete remission lasting 12 months.

Synthesis, characterization and antineoplastic activity of bis-aziridinyl dimeric naphthoquinone - A novel class of compounds with potent activity against acute myeloid leukemia cells.

The synthesis, characterization and antileukemic activity of rationally designed amino dimeric naphthoquinone (BiQ) possessing aziridine as alkylating moiety is described. Bis-aziridinyl BiQ decreased proliferation of acute myeloid leukemia (AML) cell lines and primary cells from patients, and exhibited potent (nanomolar) inhibition of colony formation and overall cell survival in AML cells. Effective production of reactive oxygen species (ROS) and double stranded DNA breaks (DSB) induced by bis-aziridinyl BiQ is reported. Bis-dimethylamine BiQ, as the isostere of bis-aziridinyl BiQ but without the alkylating moiety did not show as potent anti-AML activity. Systemic administration of bis-aziridinyl BiQ was well tolerated in NSG mice.

Preclinical and first-in-human phase I studies of KW-2450, an oral tyrosine kinase inhibitor with insulin-like growth factor receptor-1/insulin receptor selectivity.

Numerous solid tumors overexpress or have excessively activated insulin-like growth factor receptor-1 (IGF-1R). We summarize preclinical studies and the first-in-human study of KW-2450, an oral tyrosine kinase inhibitor with IGF-1R and insulin receptor (IR) inhibitory activity. Preclinical activity of KW-2450 was evaluated in various in vitro and in vivo models. It was then evaluated in a phase I clinical trial in 13 patients with advanced solid tumors (NCT00921336). In vitro, KW-2450 inhibited human IGF-1R and IR kinases (IC50 7.39 and 5.64 nmol/L, respectively) and the growth of various human malignant cell lines. KW-2450 40 mg/kg showed modest growth inhibitory activity and inhibited IGF-1-induced signal transduction in the murine HT-29/GFP colon carcinoma xenograft model. The maximum tolerated dose of KW-2450 was 37.5 mg once daily continuously; dose-limiting toxicity occurred in two of six patients at 50 mg/day (both grade 3 hyperglycemia) and in one of seven patients at 37.5 mg/day (grade 3 rash). Four of 10 evaluable patients showed stable disease. Single-agent KW-2450 was associated with modest antitumor activity in heavily pretreated patients with solid tumors and is being further investigated in combination therapy with lapatinib/letrozole in patients with human epidermal growth factor receptor 2-postive metastatic breast cancer.

A direct interaction between NQO1 and a chemotherapeutic dimeric naphthoquinone.

BACKGROUND: Multimeric naphthoquinones are redox-active compounds that exhibit antineoplastic, antiprotozoal, and antiviral activities. Due to their multimodal effect on perturbation of cellular oxidative state, these compounds hold great potential as therapeutic agents against highly proliferative neoplastic cells. In our previous work, we developed a series of novel dimeric naphthoquinones and showed that they were selectively cytotoxic to human acute myeloid leukemia (AML), breast and prostate cancer cell lines. We subsequently identified the oxidoreductase NAD(P)H dehydrogenase, quinone 1 (NQO1) as the major target of dimeric naphthoquinones and proposed a mechanism of action that entailed induction of a futile redox cycling. RESULTS: Here, for the first time, we describe a direct physical interaction between the bromohydroxy dimeric naphthoquinone E6a and NQO1. Moreover, our studies reveal an extensive binding interface between E6a and the isoalloxazine ring of the flavin adenine dinucleotide (FAD) cofactor of NQO1 in addition to interactions with protein side chains in the active site. We also present biochemical evidence that dimeric naphthoquinones affect the redox state of the FAD cofactor of NQO1. Comparison of the mode of binding of E6a with those of other chemotherapeutics reveals unique characteristics of the interaction that can be leveraged in future drug optimization efforts. CONCLUSION: The first structure of a dimeric naphthoquinone-NQO1 complex was reported, which can be used for design and synthesis of more potent next generation dimeric naphthoquinones to target NQO1 with higher affinity and specificity.

Disparities in black and white patients with multiple myeloma referred for autologous hematopoietic transplantation: a single center study.

BACKGROUND: Racial disparity in the incidence of multiple myeloma is well established; however, to the authors' knowledge, little is known regarding the impact of racial differences on disease characteristics, response to therapy, and clinical outcome. METHODS: The authors studied 453 patients (174 of whom were black and 279 of whom were white) who underwent transplant between 2000 and 2013. The median follow-up was 4.4 years. RESULTS: Black patients were significantly younger than white patients (median age, 54 years vs 59 years; P<.0001), more frequently presented with anemia (P = .04), had more of the immunoglobulin G isotype (P<.001), and had a borderline favorable cytogenetic risk (P = .06). Overall response to induction was similar, but deeper responses were observed in more white patients compared with black patients receiving immunomodulatory drug-based induction (P = .02). Referral for transplant was significantly delayed in black individuals (median, 1.3 years vs 0.9 years; P = .003). Overall survival from the time of transplant was similar for black and white patients, with medians of 6.2 years and 5.7 years, respectively, but survival from the time of diagnosis was significantly longer among black individuals (median, 7.7 years vs 6.1 years; P = .03). Maintenance therapy was found to positively impact progression-free survival but not overall survival, irrespective of race. CONCLUSIONS: The results of the current study confirm ethnic differences in age, referral patterns, response to therapy, and overall survival. Future validation of these disparities is urgently needed.

First-in-human phase 1 study of filanesib (ARRY-520), a kinesin spindle protein inhibitor, in patients with advanced solid tumors.

Purpose Filanesib (ARRY-520) is a highly selective, targeted inhibitor of kinesin spindle protein (KSP) inhibitor that induces mitotic arrest and subsequent tumor cell death. This first-in-human Phase 1 study evaluated dose-limiting toxicities (DLTs) and determined a maximum tolerated dose (MTD) for filanesib administered as a 1-h intravenous infusion on 2 treatment schedules in patients with advanced solid tumors. The pharmacokinetics (PK), pharmacodynamics and preliminary efficacy of filanesib were also evaluated. Methods Filanesib was administered on Day 1 of each 3-week cycle (Initial Schedule) or Days 1 and 2 of each 2-week cycle (Alternate Schedule). A standard 3 + 3 dose-escalation design was employed. An expansion cohort was conducted at the MTD of the Initial Schedule. Filanesib PK was evaluated in plasma (both schedules) and urine (Initial Schedule only). Monopolar spindle formation was evaluated in biopsies taken from patients in the expansion cohort. Results Forty-one patients received filanesib. The MTD was equivalent for both the Initial and Alternate Schedules (2.50 mg/m(2)/cycle). The prevalence of neutropenia as a DLT for both schedules necessitated adding prophylactic filgrastim to another dose escalation on the Alternate Schedule (highest tolerated dose 3.20 mg/m(2)/cycle). Neurotoxicity related to filanesib was not observed. Dose-proportional increases in filanesib exposure were observed. The half-life for filanesib was ~70 h. Monopolar spindles in patient biopsy samples indicated KSP inhibition. Stable disease was the best tumor response observed in 18 % (7/39) of evaluable patients. Conclusion Filanesib provided exposures with acceptable tolerability and evidence of target-specific pharmacodynamic effects.

Phase 1 dose-escalation, pharmacokinetic, and cerebrospinal fluid distribution study of TAK-285, an investigational inhibitor of EGFR and HER2.

INTRODUCTION: This phase 1 study assessed safety, maximum tolerated dose (MTD), pharmacokinetics, cerebrospinal fluid (CSF) distribution, and preliminary clinical activity of the receptor tyrosine kinase inhibitor TAK-285. METHODS: Patients with advanced, histologically confirmed solid tumors and Eastern Cooperative Oncology Group performance status ≤2 received daily oral TAK-285; daily dose was escalated within defined cohorts until MTD and recommended phase 2 dose (RP2D) were determined. Eleven patients were enrolled into an RP2D cohort. Blood samples were collected from all cohorts; CSF was collected at pharmacokinetic steady-state from RP2D patients. Tumor responses were assessed every 8 weeks per Response Evaluation Criteria in Solid Tumors. RESULTS: Fifty-four patients were enrolled (median age 60; range, 35-76 years). The most common diagnoses were cancers of the colon (28 %), breast (17 %), and pancreas (9 %). Escalation cohorts evaluated doses from 50 mg daily to 500 mg twice daily; the MTD/RP2D was 400 mg twice daily. Dose-limiting toxicities included diarrhea, hypokalemia, and fatigue. Drug absorption was fast (median time of maximum concentration was 2-3 h), and mean half-life was 9 h. Steady-state average unbound CSF concentration (geometric mean 1.54 [range, 0.51-4.27] ng/mL; n = 5) at the RP2D was below the 50 % inhibitory concentration (9.3 ng/mL) for inhibition of tyrosine kinase activity in cells expressing recombinant HER2. Best response was stable disease (12 weeks of nonprogression) in 13 patients. CONCLUSIONS: TAK-285 was generally well tolerated at the RP2D. Distribution in human CSF was confirmed, but the free concentration of the drug was below that associated with biologically relevant target inhibition.

The TSC2/mTOR pathway drives endothelial cell transformation induced by the Kaposi's sarcoma-associated herpesvirus G protein-coupled receptor.

The Kaposi's sarcoma-associated herpesvirus (KSHV), the infectious causative agent of Kaposi's sarcoma (KS), encodes a G protein-coupled receptor (vGPCR) implicated in the initiation of KS. Here we demonstrate that Kaposi's sarcomagenesis involves stimulation of tuberin (TSC2) phosphorylation by vGPCR, promoting the activation of mTOR through both direct and paracrine mechanisms. Pharmacologic inhibition of mTOR with rapamycin prevented vGPCR sarcomagenesis, while overactivation of this pathway was sufficient to render endothelial cells oncogenic. Moreover, mice haploinsufficient for TSC2 are predisposed to vascular sarcomas remarkably similar to KS. Collectively, these results implicate mTOR in KS initiation and suggest that the sarcomagenic potential of KSHV may be a direct consequence of the profound sensitivity of endothelial cells to vGPCR dysregulation of the TSC2/mTOR pathway.

Phase I study of UCN-01 and perifosine in patients with relapsed and refractory acute leukemias and high-risk myelodysplastic syndrome.

BACKGROUND: The PI3K-Akt pathway is frequently activated in acute leukemias and represents an important therapeutic target. UCN-01 and perifosine are known to inhibit Akt activation. METHODS: The primary objective of this phase I study was to determine the maximum tolerated dose (MTD) of UCN-01 given in combination with perifosine in patients with advanced acute leukemias and myelodysplastic syndrome. Secondary objectives included safety, pharmacokinetics, pharmacodynamics, and efficacy. Perifosine 150 mg every 6 h was given orally on day 1 followed by 100 mg once a day continuously in 28-day cycles. UCN-01 was given intravenously over 3 h on day 4 at three dose levels (DL1=40 mg/m(2); DL2=65 mg/m(2); DL3=90 mg/m(2)). RESULTS: Thirteen patients were treated (DL1, n=6; DL2, n=4; DL3, n=3) according to a traditional "3+3" design. Two patients at the DL3 experienced dose-limiting toxicity including grade 3-4 pericardial effusion, hypotension, hyperglycemia, hyperkalemia, constitutional symptoms and grade 5 pneumonitis. Other frequent toxicities were grade 1-2 nausea, diarrhea, vomiting, fatigue and hyperglycemia. The MTD was determined to be UCN-01 65 mg/m(2) with perifosine 100 mg a day. No appreciable direct Akt inhibition could be demonstrated in patients' mononuclear cells using Western blot, however, reduced phosphorylation of the downstream target ribosomal protein S6 in leukemic blasts was noted by intracellular flow cytometry. No objective responses were observed on this study. CONCLUSION: UCN-01 and perifosine can be safely administered, but this regimen lacked clinical efficacy. This approach may have failed because of insufficient Akt inhibition in vivo.

Reducing undesirable hepatic clearance of a tumor-targeted vinca alkaloid via novel saccharopeptidic modifications.

During a phase I trial of EC145 (a folate-targeted vinca alkaloid conjugate), constipation was identified as the dose-limiting toxicity, probably from a nonfolate receptor-related liver clearance process capable of releasing unconjugated vinca alkaloid from EC145 and shuttling it to the bile. Here, we report on the selective placement of novel carbohydrate segments (1-amino-1-deoxy-glucitolyl-γ-glutamate) spaced in-between the folate and vinca alkaloid moieties of EC145, which yielded a new agent (EC0489) that is equipotent but less toxic than EC145. Whereas both compounds could cure tumor-bearing mice reproducibly, EC0489 differed from EC145 with i) a shorter elimination half-life, ii) approximately 70% decrease in bile clearance, iii) a 4-fold increase in urinary excretion, and iv) improved tolerability in rodents. This combination of improvements justified the clinical evaluation of EC0489 where currently administered dose levels have exceeded the maximal tolerated dose of EC145 by approximately 70%, thereby reflecting the translational benefits to this new approach.

Preclinical studies of vorinostat (suberoylanilide hydroxamic acid) combined with cytosine arabinoside and etoposide for treatment of acute leukemias.

PURPOSE: Vorinostat [suberoylanilide hydroxamic acid (SAHA)] is a potent histone deacetylase inhibitor with promising clinical efficacy as an anticancer agent. In this preclinical study, we evaluated combining cytosine arabinoside [1-beta-D-arabinofuranosylcytosine (ara-C)] and/or etoposide with vorinostat for use in the treatment of acute leukemias. EXPERIMENTAL DESIGN: Cell survival was examined in vitro in HL-60 human myeloid leukemia cells and K562 myeloid blast crisis chronic myelogenous leukemia cells, using the 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide inner salt and/or fluorescein diacetate/propidium iodide assays. Drug interactions were analyzed by the combination index method (CalcuSyn) and by a novel statistical method that we developed (SynStat). Cell cycle phase distribution was measured by flow cytometry. RESULTS: Cytotoxic antagonism resulted when vorinostat was combined concomitantly with ara-C; however, when vorinostat was given first followed by a drug-free interval before ara-C treatment, this sequential combination was mostly synergistic. Etoposide combined with vorinostat was additive to synergistic, and the synergism became more pronounced when etoposide was given after vorinostat. Cell cycle analyses revealed that the sequence-dependent interaction of vorinostat and ara-C or etoposide reflected the arrest of cells in G1 or G2 phase during vorinostat treatment and recovery into S phase after removal of vorinostat. CONCLUSIONS: These findings using two independent methods to assess drug combination effects provide a preclinical rationale for phase I trials of the sequential combination of vorinostat followed by ara-C and etoposide in patients with advanced or refractory leukemias. CalcuSyn findings were concordant with those of SynStat, validating the use of the latter in analyzing drug interactions.

Phospho-p70S6K/p85S6K and cdc2/cdk1 are novel targets for diffuse large B-cell lymphoma combination therapy.

PURPOSE: This study aimed to identify and evaluate molecular targets for the development of a novel combination chemotherapy to treat refractory and recurrent diffuse large B-cell lymphoma (DLBCL). EXPERIMENTAL DESIGN: Lymphoma samples from 38 cases of primary and recurrent DLBCL were analyzed using real-time quantitative PCR of the RPS6KB1 and CDC2 genes, and immunohistochemistry for their gene products p70S6K/p85S6K and cdc2/cdk1. The Farage, Karpas422, Pfeiffer, and Toledo DLBCL cell lines were subsequently treated with rapamycin and UCN-01 alone or in combination. Cell proliferation, apoptosis, and cell cycle progression were analyzed after the drug treatment. In addition, the levels of several key protein kinases involved in the phosphoinositide 3'-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway, apoptosis, and cell cycle progression were analyzed in the presence and absence of the drugs. RESULTS: Amplification of the RPS6KB1 and CDC2 genes was found in both primary and recurrent DLBCL. Moreover, the vast majority of these lymphomas (approximately 94%) were strongly positive for phospho-p70S6K and cdc2/cdk1 proteins. The combination of rapamycin and UCN-01 synergistically inhibited the DLBCL cell proliferation by inducing G1 arrest as well as apoptosis by suppressing the phosphorylation of p70S6K/p85S6K and CDC2 expression. CONCLUSION: RPS6KB1 and CDC2 overexpression is common in DLBCL. Simultaneously targeting the RPS6KB1 and CDC2 products phospho-p70S6K/p85S6K and cdc2/cdk1 is very effective in inhibiting DLBCL proliferation and overcoming drug resistance. This work suggests that multilevel inhibition of the PI3K/Akt/mTOR pathway and double-block of cell cycle progression are effective strategies for DLBCL therapy.

Biodistribution of HPMA copolymer-aminohexylgeldanamycin-RGDfK conjugates for prostate cancer drug delivery.

N-(2-Hydroxypropyl)methacrylamide (HPMA) copolymer-RGD (Arg-Gly-Asp) conjugates targeting the alpha(v)beta(3) integrin present on angiogenic blood vessels and some tumor types have shown increased accumulation in solid tumors and possess properties that suggest their use for site-specific drug delivery. Geldanamycin (GDM) is a benzoquinoid ansamycin that binds to heat-shock protein 90 (HSP90), effective for the treatment of multiple cancer types including prostate, but has dose-limiting cytotoxicity. We recently reported the synthesis of HPMA copolymer-aminohexyl-geldanamycin (AH-GDM) conjugates containing RGDfK that demonstrated favorable properties of drug release, in vitro binding to the alpha(v)beta(3) integrin, cytotoxicity in human prostate cancer cells, and tolerability in nude mice greater than 2-fold equivalent free drug doses. In this study the biodistribution of 125I-radiolabeled HPMA copolymer-AH-GDM conjugates with and without RGDfK in both non-tumor-bearing and DU145 prostate tumor xenograft-bearing nude mice was evaluated. At 60 mg/kg drug equivalent polymer doses in non-tumor-bearing mice both conjugates showed fast elimination from blood and decreasing accumulation in all other organs. Kidney accumulation predominated and was higher for the conjugate containing RGDfK. In tumor-bearing mice, trace quantities of the conjugate containing RGDfK showed increased tumor accumulation as compared to the conjugate without RGDfK. Also evaluated were free drug concentrations in prostate tumor xenografts following treatments of 30 and 60 mg/kg drug-equivalent copolymer conjugates (with and without RGDfK) compared with 30 mg/kg free AH-GDM. Overall, 60 mg/kg treatment of RGDfK-containing conjugate showed significantly higher (p < 0.001) tumor drug concentrations compared with all other treatments. The targetable conjugates can effectively deliver higher amounts of geldanamycin to the tumor compared to nontargetable systems.

Targetable HPMA copolymer-aminohexylgeldanamycin conjugates for prostate cancer therapy.

PURPOSE: This study focuses on the synthesis and characterization of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-cyclo-RGD (Arg-Gly-Asp) conjugates for delivery of geldanamycin to prostate tumors. MATERIALS AND METHODS: HPMA copolymers containing aminohexylgeldanamycin (AH-GDM) with and without the targeting peptide RGDfK were synthesized and characterized. Drug release from copolymers was evaluated using cathepsin B. Competitive binding of copolymer conjugates to alpha(v)beta(3) integrin was evaluated in prostate cancer (PC-3) and endothelial (HUVEC) cell lines and in vitro growth inhibition was assessed. The maximum tolerated dose for single i.v. injections of free drug and the conjugates was established in nude mice. RESULTS: HPMA copolymers containing AH-GDM and RGDfK showed active binding to the alpha(v)beta(3) integrin similar to that of free peptide. Similarly, growth inhibition of cells by conjugates was comparable to that of the free drug. Single intravenous doses of HPMA copolymer-AH-GDM-RGDfK conjugates in mice were tolerated at 80 mg/kg drug equivalent, while free drug caused morbidity at 40 mg/kg. No signs of toxicity were present in mice receiving HPMA copolymer-AH-GDM-RGDfK over the 14-day evaluation period. CONCLUSION: Results of in vitro activity and in vivo tolerability experiments hold promise for the utility of HPMA copolymer-AH-GDM-RGDfK conjugates for treatment of prostate cancer with greater efficacy and reduced toxicity.

Identification of small molecule inhibitors of anthrax lethal factor.

The virulent spore-forming bacterium Bacillus anthracis secretes anthrax toxin composed of protective antigen (PA), lethal factor (LF) and edema factor (EF). LF is a Zn-dependent metalloprotease that inactivates key signaling molecules, such as mitogen-activated protein kinase kinases (MAPKK), to ultimately cause cell death. We report here the identification of small molecule (nonpeptidic) inhibitors of LF. Using a two-stage screening assay, we determined the LF inhibitory properties of 19 compounds. Here, we describe six inhibitors on the basis of a pharmacophoric relationship determined using X-ray crystallographic data, molecular docking studies and three-dimensional (3D) database mining from the US National Cancer Institute (NCI) chemical repository. Three of these compounds have K(i) values in the 0.5-5 microM range and show competitive inhibition. These molecular scaffolds may be used to develop therapeutically viable inhibitors of LF.