16 research outputs found
GnRH-gemcitabine conjugates for the treatment of androgen-independent prostate cancer : pharmacokinetic enhancements combined with targeted drug delivery
Gemcitabine, a drug with established efficacy against a number of solid tumors, has
therapeutic limitations due to its rapid metabolic inactivation. The aim of this study
was the development of an innovative strategy to produce a metabolically stable
analogue of gemcitabine that could also be selectively delivered to prostate cancer
(CaP) cells based on cell surface expression of the Gonadotropin Releasing Hormone-
Receptor (GnRH-R). The synthesis and evaluation of conjugated molecules,
consisting of gemcitabine linked to a GnRH agonist, is presented along with results in
androgen-independent prostate cancer models. NMR and ligand binding assays were
employed to verify conservation of microenvironments responsible for binding of
novel GnRH-gemcitabine conjugates to the GnRH-R. In vitro cytotoxicity, cellular
uptake and metabolite formation of the conjugates were examined in CaP cell lines.
Selected conjugates were efficacious in the in vitro assays with one of them, namely
GSG, displaying high antiproliferative activity in CaP cell lines along with significant
metabolic and pharmacokinetic advantages in comparison to gemcitabine. Finally,
treatment of GnRH-R positive xenografted mice with GSG, showed a significant
advantage in tumor growth inhibition when compared to gemcitabine.A.G.Leventis foundation and the General Secretariat for Research & Technology of the Greek Ministry of Education (LS7- 1682/17156/6.12.10).MRC and National Research Foundation of South Africa, and the Universities of Pretoria and Cape Townhttp://pubs.acs.org/bc2015-02-28hb201
Cyanobacterial Cyclopeptides as Lead Compounds to Novel Targeted Cancer Drugs
Abstract: Cyanobacterial cyclopeptides, including microcystins and nodularins, are considered a health hazard to humans due to the possible toxic effects of high consumption. From a pharmacological standpoint, microcystins are stable hydrophilic cyclic heptapeptides with a potential to cause cellular damage following uptake via organic aniontransporting polypeptides (OATP). Their intracellular biological effects involve inhibition of catalytic subunits of protein phosphatase 1 (PP1) and PP2, glutathione depletion and generation of reactive oxygen species (ROS). Interestingly, certain OATPs are prominently expressed in cancers as compared to normal tissues, qualifying MC as potential candidates for cancer drug development. In the era of targeted cancer therapy, cyanotoxins comprise a rich source of natural cytotoxic compounds with a potential to target cancers expressing specific uptake transporters. Moreover, their structure offers opportunities for combinatorial engineering to enhance the therapeutic index and resolve organ-specific toxicity issues. In this article, we revisit cyanobacterial cyclopeptides as potential novel targets for anticancer drugs by summarizing existing biomedical evidence, presentin
Targeting Oncogenic Protein-Protein Interactions by Diversity Oriented Synthesis and Combinatorial Chemistry Approaches
We are currently witnessing a decline in the development of efficient new anticancer drugs, despite the salient efforts made on all fronts of cancer drug discovery. This trend presumably relates to the substantial heterogeneity and the inherent biological complexity of cancer, which hinder drug development success. Protein-protein interactions (PPIs) are key players in numerous cellular processes and aberrant interruption of this complex network provides a basis for various disease states, including cancer. Thus, it is now believed that cancer drug discovery, in addition to the design of single-targeted bioactive compounds, should also incorporate diversity-oriented synthesis (DOS) and other combinatorial strategies in order to exploit the ability of multi-functional scaffolds to modulate multiple protein-protein interactions (biological hubs). Throughout the review, we highlight the chemistry driven approaches to access diversity space for the discovery of small molecules that disrupt oncogenic PPIs, namely the p53-Mdm2, Bcl-2/Bcl-xL-BH3, Myc-Max, and p53-Mdmx/Mdm2 interactions
Diversity Oriented Synthesis of a Vinblastine-Templated Library of 7‑Aryl-Octahydroazonino[5,4‑<i>b</i>]indoles via a Three-Component Reaction
A vinblastine-templated library of 7-aryl-octahydroazonino[5,4-<i>b</i>]indoles was prepared by a three-component reaction from
indolizino[8,7-<i>b</i>]indoles, chloroformates, and activated
arenes via a chloroformate mediated fragmentation of the indolizinoindole
nucleus followed by insertion of an activated arene. In addition to
N3-carbamoyl-7-aryl-octahydroazonino[5,4-<i>b</i>]indoles
prepared in one step, a wide range of N3-substituted substrates were
synthesized in one pot via the derivatization of a versatile N3–H-azonino[5,4-<i>b</i>]indole intermediate generated in situ by application of
the same strategy. A subset of 308 compounds out of a virtual library
of 3216, representing 13 different chemotypes, was prepared by high
throughput solution-phase synthesis and subsequently purified by mass-triggered
high performance liquid chromatography (HPLC). A total
of 188 compounds with a minimum purity of 80% by UV<sub>214 nm</sub> and 85% by evaporative light scattering detection (ELSD) was isolated
for primary screening
Diversity Oriented Synthesis of a Vinblastine-Templated Library of 7‑Aryl-Octahydroazonino[5,4‑<i>b</i>]indoles via a Three-Component Reaction
A vinblastine-templated library of 7-aryl-octahydroazonino[5,4-<i>b</i>]indoles was prepared by a three-component reaction from
indolizino[8,7-<i>b</i>]indoles, chloroformates, and activated
arenes via a chloroformate mediated fragmentation of the indolizinoindole
nucleus followed by insertion of an activated arene. In addition to
N3-carbamoyl-7-aryl-octahydroazonino[5,4-<i>b</i>]indoles
prepared in one step, a wide range of N3-substituted substrates were
synthesized in one pot via the derivatization of a versatile N3–H-azonino[5,4-<i>b</i>]indole intermediate generated in situ by application of
the same strategy. A subset of 308 compounds out of a virtual library
of 3216, representing 13 different chemotypes, was prepared by high
throughput solution-phase synthesis and subsequently purified by mass-triggered
high performance liquid chromatography (HPLC). A total
of 188 compounds with a minimum purity of 80% by UV<sub>214 nm</sub> and 85% by evaporative light scattering detection (ELSD) was isolated
for primary screening
Diversity Oriented Synthesis of a Vinblastine-Templated Library of 7‑Aryl-Octahydroazonino[5,4‑<i>b</i>]indoles via a Three-Component Reaction
A vinblastine-templated library of 7-aryl-octahydroazonino[5,4-<i>b</i>]indoles was prepared by a three-component reaction from
indolizino[8,7-<i>b</i>]indoles, chloroformates, and activated
arenes via a chloroformate mediated fragmentation of the indolizinoindole
nucleus followed by insertion of an activated arene. In addition to
N3-carbamoyl-7-aryl-octahydroazonino[5,4-<i>b</i>]indoles
prepared in one step, a wide range of N3-substituted substrates were
synthesized in one pot via the derivatization of a versatile N3–H-azonino[5,4-<i>b</i>]indole intermediate generated in situ by application of
the same strategy. A subset of 308 compounds out of a virtual library
of 3216, representing 13 different chemotypes, was prepared by high
throughput solution-phase synthesis and subsequently purified by mass-triggered
high performance liquid chromatography (HPLC). A total
of 188 compounds with a minimum purity of 80% by UV<sub>214 nm</sub> and 85% by evaporative light scattering detection (ELSD) was isolated
for primary screening
Gemcitabine Based Peptide Conjugate with Improved Metabolic Properties and Dual Mode of Efficacy
Gemcitabine is a clinically established
anticancer agent potent
in various solid tumors but limited by its rapid metabolic inactivation
and off-target toxicity. We have previously generated a metabolically
superior to gemcitabine molecule (GSG) by conjugating gemcitabine
to a gonadotropin releasing hormone receptor (GnRH-R) ligand peptide
and showed that GSG was efficacious in a castration resistant prostate
cancer (CRPC) animal model. The current article provides an in-depth
metabolic and mechanistic study of GSG, coupled with toxicity assays
that strengthen the potential role of GSG in the clinic. LC–MS/MS
based approaches were employed to delineate the metabolism of GSG,
its mechanistic cellular uptake, and release of gemcitabine and to
quantitate the intracellular levels of gemcitabine and its metabolites
(active dFdCTP and inactive dFdU) resulting from GSG. The GnRH-R agonistic
potential of GSG was investigated by quantifying the testosterone
levels in animals dosed daily with GSG, while an <i>in vitro</i> colony forming assay together with <i>in vivo</i> whole
blood measurements were performed to elucidate the hematotoxicity
profile of GSG. Stability showed that the major metabolite of GSG
is a more stable nonapeptide that could prolong gemcitabine’s
bioavailability. GSG acted as a prodrug and offered a metabolic advantage
compared to gemcitabine by generating higher and steadier levels of
dFdCTP/dFdU ratio, while intracellular release of gemcitabine from
GSG in DU145 CRPC cells depended on nucleoside transporters. Daily
administrations in mice showed that GSG is a potent GnRH-R agonist
that can also cause testosterone ablation without any observed hematotoxicity.
In summary, GSG could offer a powerful and unique pharmacological
approach to prostate cancer treatment: a single nontoxic molecule
that can be used to reach the tumor site selectively with superior
to gemcitabine metabolism, biodistribution, and safety while also
agonistically ablating testosterone levels
Peptide-Drug conjugate gnrh-sunitinib targets angiogenesis selectively at the site of action to inhibit tumor growth
The potential to heighten the efficacy of antiangiogenic agents was explored in this study based on active targeting of tumor cells overexpressing the gonadotropin-releasing hormone receptor (GnRH-R). The rational design pursued focused on five analogues of a clinically established antiangiogenic compound (sunitinib), from which a lead candidate (SAN1) was conjugated to the targeting peptide [D-Lys6]-GnRH, generating SAN1GSC. Conjugation of SAN1 did not disrupt any of its antiangiogenic or cytotoxic properties in GnRH-R-expressing prostate and breast tumor cells. Daily SAN1GSC treatments in mouse xenograft models of castration-resistant prostate cancer resulted in significant tumor growth delay compared with equimolar SAN1 or sunitinib alone. This efficacy correlated with inhibited phosphor-ylation of AKT and S6, together with reduced Ki-67 and CD31 expression. The superior efficacy of the peptide-drug conjugate was also attributed to the finding that higher amounts of SAN1 were delivered to the tumor site (∼4-fold) following dosing of SAN1GSC compared with equimolar amounts of nonconjugated SAN1. Importantly, treatment with SAN1GSC was associated with minimal hematotoxicity and cardiotoxicity based on measurements of the left ventricular systolic function in treated mice. Our results offer preclinical proof-of-concept for SAN1GSC as a novel molecule that selectively reaches the tumor site and downregulates angiogenesis with negligible cardiotoxicity, thus encouraging its further clinical development and evaluation.</p