Antitumor activity of KW-2170, a novel pyrazoloacridone derivative

ASYMMETRIC SYNTHESIS: A GLANCE AT VARIOUS METHODOLOGIES FOR DIFFERENT FRAMEWORKS

Abstract:

Asymmetric reactions have made a significant advancement over the past few decades and involved the production of enantiomerically pure molecules using enantioselective organocatalysis, chiral auxiliaries/substrates, and reagents via controlling the absolute stereochemistry. The laboratory synthesis from an enantiomerically impure starting material gives a combination of enantiomers which are difficult to separate for chemists in the fields of medicine, chromatography, pharmacology, asymmetric synthesis, studies of structure-function relationships of proteins, life sciences and mechanistic studies. This challenging step of separation can be avoided by the use of asymmetric synthesis. Using pharmacologically relevant scaffolds/pharmacophores, the drug designing can also be achieved using asymmetric synthesis to synthesize receptor specific pharmacologically active chiral molecules. This approach can be used to synthesize asymmetric molecules from wide variety of reactants using specific asymmetric conditions which is also beneficial for environment due to less usage and discharge of chemicals into the environment. So, in this review, we have focused on the inclusive collation of diverse mechanisms in this area, to encourage auxiliary studies of asymmetric reactions to develop selective, efficient, environment-friendly and high yielding advanced processes in asymmetric reactions.

Recent advances in the asymmetric synthesis of pharmacology-relevant nitrogen heterocycles via stereoselective aza-Michael reactions

In this review, recent applications of a stereoselective aza-Michael reaction for asymmetric synthesis of naturally occurring N-containing heterocyclic scaffolds and their usefulness to pharmacology are summarized.

A phase II trial of weekly i.v. KW-2170 in advanced castrate-resistant prostate cancer

AIM

KW-2170 is a novel pyrazoloacridone derivative that intercalates nucleic acids. It has promising in vitro properties against prostate and other cancers and is active in vivo against doxorubicin-resistant cell lines. We wished to investigate its activity and toxicity profile in this Phase II trial in androgen independent prostate cancer.

METHODS

Overall 44 men were recruited to this multicenter, open label, non-randomized study, with 35 evaluable for prostatic specific antigen (PSA) response.

RESULTS

Five patients had a PSA fall greater than 50% (overall RR 14.3%, 95% CI 4.8-30.3%). Overall median survival was 16 months. In the evaluable group (n = 35), median survival was 18.9 months. The drug was very well tolerated, with the most common toxicities being hematological (anemia, leucopenia, thrombocytopenia), alopecia, fatigue, and nausea. However, most of these were National Cancer Institute Grade 1 or 2; Grade 3 neutropenia occurred in only 11% of patients, and there was no Grade 4 neutropenia. Quality of life as measured by the FACT-P scale was not compromised.

CONCLUSION

KW-2170 is a very well tolerated chemotherapy agent. It has a relatively low PSA response rate, and did not meet the pre-specified criteria for further studies.

Efficacy and toxicity of the novel chemotherapeutic agent KW-2170 in recurrent epithelial ovarian cancer

OBJECTIVES

KW-2170 is a novel DNA intercalating agent whose mechanism of action is similar to doxorubicin HCl, yet is associated with less cardiac toxicity. The objective of this study was to evaluate the activity and toxicity of this novel chemotherapeutic agent in patients with recurrent ovarian carcinoma.

METHODS

A prospective phase II trial was performed in patients with persistent or recurrent epithelial ovarian or primary peritoneal carcinoma and measurable disease. Patients could have platinum-sensitive or refractory disease and could have received any number of prior treatments. One treatment cycle consisted of KW-2170 administered at a dose of 18 mg/m(2) weekly for 3 weeks followed by a 21-day rest period. Toxicity was assessed using the NCI Common Toxicity Criteria (Version 2.0), and dose reduction was allowed for significant toxicity. Response to therapy was assessed in patients who completed at least 2 cycles using RECIST criteria.

RESULTS

A total of 28 patients were enrolled in this phase II trial at 5 separate centers. Of the 28 patients evaluated, all had stage III/IV disease at initial diagnosis. The median number of prior therapeutic regimens in these patients was 4 (range 1-8). The median number of KW-2170 cycles administered was 2 (range 1-5). Treatment-related toxicity in this heavily pretreated population was acceptable as only 6 patients (21%) had grade 3-4 neutropenia. Dose reductions occurred in 6 patients (21%) for grades 1-4 neutropenia, and no patient had febrile neutropenia. Four patients completed less than 1 cycle; 3 secondary to progressive disease, and one due to Gram-positive sepsis. Of patients receiving at least 2 full cycles, 10 patients (55%) had stable disease with a median of 4.5 months (range 3-10) to disease progression. All other patients were removed from the study after 1-2 cycles of therapy with no significant clinical effect noted.

CONCLUSIONS

Although associated with relatively little toxicity, KW-2170 at the dose and schedule evaluated demonstrated little clinical activity in this heavily pretreated population of recurrent ovarian cancer patients. Whether KW-2170 would have greater clinical activity in a more treatment naive group of patients at an increased dose awaits clinical trial evaluation.

Synthesis and evaluation of novel pyrimido-acridone, -phenoxadine, and -carbazole as topoisomerase II inhibitors

As part of a series of studies to discover new topoisomerase II inhibitors, novel pyrimidoacridones, pyrimidophenoxadines, and pyrimidocarbazoles were synthesized, and in vitro and in vivo antitumor activities and DNA-protein and/or DNA-topoisomerase II cross-linking activity as an indicator of topoisomerase II-DNA cleavable complex formation were evaluated. The pyrimidocarbazoles possessed high in vitro and in vivo potencies. Compound 26 (ER-37326), 8-acetyl-2-[2-(dimethylamino)ethyl]-1H-pyrimido[5,6,1-jk]carbazole-1,3(2H)-dione, showed in vitro growth inhibitory activity with respective IC(50) values of 0.049 microM and 0.35 microM against mouse leukemia P388 and human oral cancer KB. In vivo, this compound inhibited the tumor growth of mouse sarcoma M5076 implanted into mice with T/C values of 42% and 13% at 3.13 and 6.25 mg/kg/d respectively without significantly affecting the body weight. In addition, compound 26 (ER-37326) increased the formation of DNA-topoisomerase II cross-linking in P388 cells.

Structure-Based Virtual Screening: An Application to Human Topoisomerase II α

The eukaryotic topoisomerase II is involved in several vital processes, such as replication, transcription, and recombination. Many compounds interfering with the catalytic action of this enzyme are efficient in human cancer chemotherapy. We applied a methodology combining molecular modeling and virtual screening techniques to identify human topoisomerase II alphainhibitors. Data from structural biology and enzymatic assays together with a good background on the enzyme mechanism of action were helpful in the approach. A human topoisomerase II alpha model provided an insight into the structural features responsible for the activity of the enzyme. A protocol comprising several substructural and protein structure-based three-dimensional pharmacophore filters enabled the successful retrieving of inhibitors of the enzyme from large databases of compounds, thus validating the approach. A subset of protein structural features required for the enzyme inhibition at the protein-DNA interface were identified and incorporated into the pharmacophore models. Compounds sharing a DNA-intercalating chromophore and a moiety interfering with the protein active site emerged as good inhibitors.

Phase I and pharmacokinetic study of KW-2170, a novel pyrazoloacridone compound, in patients with malignant tumors

PURPOSE

The primary purposes of this study were to determine the dose-limiting toxicity (DLT) and maximum tolerated dose (MTD), to recommend a dose for phase II studies, and to analyze the pharmacokinetics of KW-2170. A secondary purpose was to assess tumor response to KW-2170.

EXPERIMENTAL DESIGN

KW-2170 was given as a 30-min i.v. infusion every 4 weeks. Doses were escalated from 1.0 mg/m2 according to a modified Fibonacci method.

RESULTS

A total of 45 cycles of KW-2170 were delivered to 41 patients at doses ranging from 1.0 to 53.0 mg/m2. The primary DLT was neutropenia which was observed in two of six patients treated at 32.0 mg/m2 and in two of two patients treated at 53.0 mg/m2; therefore, the MTD was 53.0 mg/m2. Although no patients showed a complete response (CR)or partial response (PR), 15 patients were evaluated a shaving freedom from progression at the 1-month time-point, with two demonstrating slight tumor shrinkage in their metastatic lesions. None of the patients experienced significant cardiotoxicity. The plasma concentration of KW-2170 declined in a triphasic manner. The half-life, total clearance (CLtot) and volume of distribution (Vdss) were nearly constant and independent of dose, and showed a relatively small interpatient variability. A linear relationship was observed between dose and maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC 0-infinity). In addition, there was a good correlation between neutropenia and AUC 0- infinity. This suggests that toxicity may be dependent on systemic exposure to the drug. Two oxi-dative metabolites were observed in the patients' plasma and urine.

CONCLUSIONS

The primary DLT of KW-2170 in this study was neutropenia, with a MTD of 53 mg/m2.A significant linear relationship was observed between neutropenia and AUC 0- infinity. We estimate the recommended dose for phase II studies to be 41.0 mg/m2.

Determination of the anticancer drug KW-2170, a pyrazoloacridone derivative, and its metabolites in human and dog plasma by high-performance liquid chromatography using an electrochemical detector

KW-2170, 5-(3-aminopropyl) amino-7,10-dihydroxy-2-(2-hydroxethyl)-aminoethyl-6H-pyrazolo [4,5,1-de] acridin-6-one dihydroxychloride, is a novel anticancer agent under clinical development. We have established a highly sensitive method which can simultaneously quantitate KW-2170 and its two metabolites, a carboxylic (M1) and hydroxylated (M2) derivative involving the 5-position, in human and dog plasma. KW-2170 and its metabolites were extracted from plasma using a weak cation-exchange cartridge and then determined by HPLC using an electrochemical detector (ED). Over the concentration range 0.1-50 ng/ml, precision and accuracy of intra- and inter-day assay were within 11% in human plasma. In dog plasma, they were within 17% at the lower quantitation limit and within 11% at other concentrations. These three compounds were stable during the assay procedure, freeze-thawing cycles and during long-term storage. Using this methodology, the pharmacokinetics of KW-2170 in a dog could be monitored over 24 h. This method is suitable for evaluation of the detailed pharmacokinetics of KW-2170 and its metabolites in humans and dogs.