Novel C-ring analogues of 20(S)-camptothecin-part-2: synthesis and in vitro cytotoxicity of 5-C-substituted 20(S)-camptothecin analogues

Biological properties of pyrroloquinoline and pyrroloisoquinoline derivatives

In this review, we summarize pyrroloquinoline and pyrroloisoquinoline derivatives (PQs and PIQs) that act on a broad spectrum of biological targets and are used as bacteriostatic, antiviral, plasmodial, anticancer, antidiabetic and anticoagulant agents. Many of these compounds play important roles in the study of DNA and its interactions, the regulation of the cell cycle and programmed cell death. This review involves twenty-five types of skeletally analogical compounds bearing pyrrole and (iso)quinoline scaffolds with different mutual annelations.

Topoisomerase Inhibitors and Targeted Delivery in Cancer Therapy

DNA topoisomerases are enzymes that catalyze the alteration of DNA topology with transiently induced DNA strand breakage, essential for DNA replication. Topoisomerases are validated cancer chemotherapy targets. Anticancer agents targeting Topoisomerase I and II have been in clinical use and proven to be highly effective, though with significant side effects. There are tremendous efforts to develop new generation of topoisomerase inhibitors. Targeted delivery of topoisomerase inhibitors is another way to reduce the side effects. Conjugates of topoisomerases inhibitors with antibody, polymer, or small molecule are developed to target these inhibitors to tumor sites.

Safe approaches for camptothecin delivery: Structural analogues and nanomedicines

Twenty-(S)-camptothecin is a strongly cytotoxic molecule with excellent antitumor activity over a wide spectrum of human cancers. However, the direct formulation is limited by its poor water solubility, low plasmatic stability and severe toxicity, which currently limits its clinical use. As a consequence, two strategies have been developed in order to achieve safe and efficient delivery of camptothecin to target cells: structural analogues and nanomedicines. In this review, we summarize recent advances in the design, synthesis and development of camptothecin molecular derivatives and supramolecular vehicles, following a systematic classification according to structure-activity relationships (structural analogues) or chemical nature (nanomedicines). A series of organic, inorganic and hybrid materials are presented as nanoplatforms to overcome camptothecin restrictions in administration, biodistribution, pharmacokinetics and toxicity. Nanocarriers which respond to a variety of stimuli endogenously (e.g., pH, redox potential, enzyme activity) or exogenously (e.g., magnetic field, light, temperature, ultrasound) seem the best positioned therapeutic materials for optimal spatial and temporal control over drug release. The main goal of this review is to be used as a source of relevant literature for others interested in the field of camptothecin-based therapeutics. To this end, final remarks on the most important formulations currently under clinical trial are provided.

Perspectives on biologically active camptothecin derivatives

Camptothecins (CPTs) are cytotoxic natural alkaloids that specifically target DNA topoisomerase I. Research on CPTs has undergone a significant evolution from the initial discovery of CPT in the late 1960s through the study of synthetic small-molecule derivatives to investigation of macromolecular constructs and formulations. Over the past years, intensive medicinal chemistry efforts have generated numerous CPT derivatives. Three derivatives, topotecan, irinotecan, and belotecan, are currently prescribed as anticancer drugs, and several related compounds are now in clinical trials. Interest in other biological effects, besides anticancer activity, of CPTs is also growing exponentially, as indicated by the large number of publications on the subject during the last decades. Therefore, the main focus of the present review is to provide an ample but condensed overview on various biological activities of CPT derivatives, in addition to continued up-to-date coverage of anticancer effects.

Camptothecin and its analogues: a review on their chemotherapeutic potential

Topoisomerase I (Topo-I) is a major target for anticancer drug discovery and design. As a result, Topo-I inhibitors constitute an important class of the current anticancer drugs. To date, all of the Topo-I inhibitors that have been clinically evaluated are analogues of camptothecin (CPT), an extract of the Chinese tree Camptotheca acuminata. CPT has shown significant antitumor activity to lung, ovarian, breast, pancreas and stomach cancers. In this article the, phytochemical aspect, and various structural modifications are comprehensively reviewed as in rings A, B, C, D and E. Biological activity of camptothecin, other than anticancer, reported till the year 2003 has also been discussed.

Camptothecin: current perspectives

This review provides a detailed discussion of recent advances in the medicinal chemistry of camptothecin, a potent antitumor antibiotic. Two camptothecin analogues are presently approved for use in the clinic as antitumor agents and several others are in clinical trials. Camptothecin possesses a novel mechanism of action involving the inhibition of DNA relaxation by DNA topoisomerase I, and more specifically the stabilization of a covalent binary complex formed between topoisomerase I and DNA. This review summarizes the current status of studies of the mechanism of action of camptothecin, including topoisomerase I inhibition and additional cellular responses. Modern synthetic approaches to camptothecin and several of the semi-synthetic methods are also discussed. Finally, a systematic evaluation of novel and important analogues of camptothecin and their contribution to the current structure-activity profile are considered.

Quantitative determination of DRF-1042 in human plasma by HPLC: validation and application in clinical pharmacokinetics

A simple and sensitive high-performance liquid chromatography (HPLC) method has been developed and validated for the determination of DRF-1042, a novel orally active camptothecin (CPT) analog, in human plasma. The sample preparation was a simple deproteinization with acidified methanol yielding almost 100% recovery of DRF-1042. An isocratic reverse-phase HPLC separation was developed on a Supelcosil-LC318 column (250 x 4.6 mm, 5 microm) with mobile phase consisting of 1% v/v triethylamine acetate, pH 5.5 and acetonitrile (80:20, v/v) at a fl ow rate of 1.0 mL/min. The eluate was monitored with a fluorescence detector set at excitation and emission wavelengths of 370 and 430 nm, respectively. The standard curves were linear (r(2) > 0.999) in the concentration ranges 5.0-2004 ng/mL. The lower limit of quantification (LLQ) of the assay was 5 ng/mL. The mean measured quality control (QC) concentrations (range 5 ng/mL to 40 microg/mL) deviated from the nominal concentrations in the range of -10.5-0.08 and -14.5-7.97%, inter- and intra-day, respectively. The inter- and intra-day precisions in the measurement of QC samples at four tested concentrations, were in the range 0.64-5.89% relative standard deviation (RSD) and 0.33-14.7% RSD, respectively. The method was found to be suitable for measurement of plasma concentrations above the calibration curve after serial dilutions. Stability of DRF-1042 was confirmed in a battery of studies, viz., on bench-top, in the auto-sampler, in the stock solutions, after four quick freeze-thaw cycles, up to one month at -20 degree C in human plasma and up to 2 months in the ex vivo samples. The method is simple, sensitive and reliable and has been successfully implemented to investigate the clinical pharmacokinetics of DRF-1042 in cancer patients in a phase I clinical trial.

Novel C-ring analogues of 20(S)-camptothecin. Part 3: synthesis and their in vitro cytotoxicity of A-, B- and C-ring analogues

Several 5-substituted alkoxy 20(S)-camptothecin analogues having A- and B-ring substituents were prepared via semi-synthesis. Most of these compounds were found to exhibit potent anti-cancer activity based on their in vitro cytotoxicity data obtained against human tumor cell lines.