36 research outputs found
PDEPT: polymer-directed enzyme prodrug therapy
Polymer-directed enzyme prodrug therapy (PDEPT) is a novel two-step antitumour approach using a combination of a polymeric prodrug and polymer-enzyme conjugate to generate cytotoxic drug selectively at the tumour site. In this study the polymeric prodrug N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer-Gly-Phe-Leu-Gly-doxorubicin conjugate PK1 (currently under Phase II clinical evaluation) was selected as the model prodrug, and HPMA copolymer-cathepsin B as a model for the activating enzyme conjugate. Following polymer conjugation (yield of 30β35%) HPMA copolymer-cathepsin B retained ~20β25% enzymatic activity in vitro. To investigate pharmacokinetics in vivo,125I-labelled HPMA copolymer-cathepsin B was administered intravenously (i.v.) to B16F10 tumour-bearing mice. HPMA copolymer-cathespin B exhibited a longer plasma half-life (free cathepsin B t1/2Ξ±= 2.8βh; bound cathepsin B t1/2Ξ±= 3.2βh) and a 4.2-fold increase in tumour accumulation compared to the free enzyme. When PK1 (10βmg kgβ1dox-equiv.) was injected i.v. into C57 mice bearing subcutaneously (s.c.) palpable B16F10 tumours followed after 5βh by HPMA copolymer-cathepsin B there was a rapid increase in the rate of dox release within the tumour (3.6-fold increase in the AUC compared to that seen for PK1 alone). When PK1 and the PDEPT combination were used to treat established B16F10 melanoma tumour (single dose; 10βmg kgβ1dox-equiv.), the antitumour activity (T/C%) seen for the combination PDEPT was 168% compared to 152% seen for PK1 alone, and 144% for free dox. Also, the PDEPT combination showed activity against a COR-L23 xenograft whereas PK1 did not. PDEPT has certain advantages compared to ADEPT and GDEPT. The relatively short plasma residence time of the polymeric prodrug allows subsequent administration of polymer-enzyme without fear of prodrug activation in the circulation and polymer-enzyme conjugates have reduced immunogenicity. This study proves the concept of PDEPT and further optimisation is warranted. Β© 2001 Cancer Research Campaignββ http://www.bjcancer.co
A Novel Small Molecule Inhibitor of Hepatitis C Virus Entry
Small molecule inhibitors of hepatitis C virus (HCV) are being developed to complement or replace treatments with pegylated interferons and ribavirin, which have poor response rates and significant side effects. Resistance to these inhibitors emerges rapidly in the clinic, suggesting that successful therapy will involve combination therapy with multiple inhibitors of different targets. The entry process of HCV into hepatocytes represents another series of potential targets for therapeutic intervention, involving viral structural proteins that have not been extensively explored due to experimental limitations. To discover HCV entry inhibitors, we utilized HCV pseudoparticles (HCVpp) incorporating E1-E2 envelope proteins from a genotype 1b clinical isolate. Screening of a small molecule library identified a potent HCV-specific triazine inhibitor, EI-1. A series of HCVpp with E1-E2 sequences from various HCV isolates was used to show activity against all genotype 1a and 1b HCVpp tested, with median EC50 values of 0.134 and 0.027 Β΅M, respectively. Time-of-addition experiments demonstrated a block in HCVpp entry, downstream of initial attachment to the cell surface, and prior to or concomitant with bafilomycin inhibition of endosomal acidification. EI-1 was equally active against cell-culture adapted HCV (HCVcc), blocking both cell-free entry and cell-to-cell transmission of virus. HCVcc with high-level resistance to EI-1 was selected by sequential passage in the presence of inhibitor, and resistance was shown to be conferred by changes to residue 719 in the carboxy-terminal transmembrane anchor region of E2, implicating this envelope protein in EI-1 susceptibility. Combinations of EI-1 with interferon, or inhibitors of NS3 or NS5A, resulted in additive to synergistic activity. These results suggest that inhibitors of HCV entry could be added to replication inhibitors and interferons already in development
Pengembangan Lembar Kerja Peserta Didik Berbasis Problem Based Learning untuk Pembelajaran Menulis Teks Deskripsi
The purpose of this study was to explain the validity, practicality, and effectiveness of problem based learning student worksheet for learning to write description text. This type of research was the development of research with the Research and Development (R&D) methode. Products that was produced in this research was the problem based learning student worksheet for learning to write a valid, practical, and effective description text . The validity of the student worksheet was 96,87% with a valid category. The value practicalities of the student worksheet from teachers was 89,84% that was categorized as very practical. The practicalities value of the student worksheet of the students was 89,63% categorized as very practical. The resulting student worksheet was declared effective because the average value of the writing skills of students by 83,21 description text
Biochemical and behavioral effects of PDE10A inhibitors: Relationship to target site occupancy
Phosphodiesterase 10A (PDE10A) inhibitors increase the functionality of striatal medium spiny neurons and produce antipsychotic-like effects in rodents by blocking PDE10A mediated hydrolysis of cAMP and/or cGMP. In the current study, we characterized a radiolabeled PDE10A inhibitor, [3H]BMS-843496, and developed an ex vivo PDE10 binding autoradiographic assay to explore the relationship between PDE10 binding site occupancy and the observed biochemical and behavioral effects of PDE10 inhibitors in mice. [3H]BMS-843496 is a potent PDE10A inhibitor with a binding affinity (KD) of 0.15 nM and a functional selectivity of \u3e100-fold over other PDE subtypes tested. Specific [3H]BMS-843496 binding sites were dominant in the basal ganglia, especially the striatum, with low to moderate binding in the cortical and hippocampal areas, of the mouse and monkey brain. Systemic administration of PDE10 inhibitors produced a dose- and plasma/brain concentration-dependent increase in PDE10A occupancy measured in the striatum. PDE10A occupancy was positively correlated with striatal pCREB expression levels. PDE10A occupancy was also correlated with antipsychotic-like effects measured using the conditioned avoidance response model; a minimum of βΌ40% occupancy was typically required to achieve efficacy. In contrast, a clear relationship between PDE10A occupancy and catalepsy scores, a potential extrapyramidal symptom readout in rodent, was not evident
Solid Phase Synthesis of 1,5-Diarylpyrazole-4-carboxamides: Discovery of Antagonists of the CB-1 Receptor
We have developed a solid phase synthesis route to 1,5-substituted
pyrazole-4-carboxamides with three diversity points aimed at the discovery
of new compounds as potential G-Protein coupled receptor (GPCR) ligands.
The new chemistry involves acylation of a resin bound secondary amine
with a Ξ²-ketoester via transamidation, conversion of the resulting
Ξ²-ketoamide to the corresponding vinylogous amide, pyrazole
formation upon reaction with a aryl hydrzine, and cleavage of the
product from the resin. Using the reported methodology, we describe
the syntheses of multiple arrays of pyrazoles that were used collectively
to construct a library of more than 1000 analogues. Several members
of this library displayed submicromolar antagonist activities at the
cannabinoid subtype 1 (CB-1) receptor
Solid Phase Synthesis of 1,5-Diarylpyrazole-4-carboxamides: Discovery of Antagonists of the CB-1 Receptor
We have developed a solid phase synthesis route to 1,5-substituted
pyrazole-4-carboxamides with three diversity points aimed at the discovery
of new compounds as potential G-Protein coupled receptor (GPCR) ligands.
The new chemistry involves acylation of a resin bound secondary amine
with a Ξ²-ketoester via transamidation, conversion of the resulting
Ξ²-ketoamide to the corresponding vinylogous amide, pyrazole
formation upon reaction with a aryl hydrzine, and cleavage of the
product from the resin. Using the reported methodology, we describe
the syntheses of multiple arrays of pyrazoles that were used collectively
to construct a library of more than 1000 analogues. Several members
of this library displayed submicromolar antagonist activities at the
cannabinoid subtype 1 (CB-1) receptor
Solid Phase Synthesis of 1,5-Diarylpyrazole-4-carboxamides: Discovery of Antagonists of the CB-1 Receptor
We have developed a solid phase synthesis route to 1,5-substituted
pyrazole-4-carboxamides with three diversity points aimed at the discovery
of new compounds as potential G-Protein coupled receptor (GPCR) ligands.
The new chemistry involves acylation of a resin bound secondary amine
with a Ξ²-ketoester via transamidation, conversion of the resulting
Ξ²-ketoamide to the corresponding vinylogous amide, pyrazole
formation upon reaction with a aryl hydrzine, and cleavage of the
product from the resin. Using the reported methodology, we describe
the syntheses of multiple arrays of pyrazoles that were used collectively
to construct a library of more than 1000 analogues. Several members
of this library displayed submicromolar antagonist activities at the
cannabinoid subtype 1 (CB-1) receptor