Second-line treatment of small-cell lung cancer with the camptothecin-derivative GI147211: a study of the EORTC Early Clinical Studies Group (ECSG)

Efforts in Bioprospecting Research: A Survey of Novel Anticancer Phytochemicals Reported in the Last Decade

Bioprospecting natural products to find prominent agents for medical application is an area of scientific endeavor that has produced many clinically used bioactive compounds, including anticancer agents. These compounds come from plants, microorganisms, and marine life. They are so-called secondary metabolites that are important for a species to survive in the hostile environment of its respective ecosystem. The kingdom of Plantae has been an important source of traditional medicine in the past and is also enormously used today as an exquisite reservoir for detecting novel bioactive compounds that are potent against hard-to-treat maladies such as cancer. Cancer therapies, especially chemotherapies, are fraught with many factors that are difficult to manage, such as drug resistance, adverse side effects, less selectivity, complexity, etc. Here, we report the results of an exploration of the databases of PubMed, Science Direct, and Google Scholar for bioactive anticancer phytochemicals published between 2010 and 2020. Our report is restricted to new compounds with strong-to-moderate bioactivity potential for which mass spectroscopic structural data are available. Each of the phytochemicals reported in this review was assigned to chemical classes with peculiar anticancer properties. In our survey, we found anticancer phytochemicals that are reported to have selective toxicity against cancer cells, to sensitize MDR cancer cells, and to have multitarget effects in several signaling pathways. Surprisingly, many of these compounds have limited follow-up studies. Detailed investigations into the synthesis of more functional derivatives, chemical genetics, and the clinical relevance of these compounds are required to achieve safer chemotherapy.

A systematic analysis of efficacy of second-line chemotherapy in sensitive and refractory small-cell lung cancer

INTRODUCTION

Small-cell lung cancer (SCLC) patients unresponsive or relapsing within 90 days after frontline chemotherapy have poor prognosis and are treated with regimens different from the first-line regimen. Potential differences in the efficacy of second-line therapy for refractory and sensitive SCLC have not been well studied.

METHODS

Studies that enrolled sensitive and refractory (relapse < 90 days or > 90 days) SCLC patients for second-line therapy were identified using electronic databases (MEDLINE, EMBASE, and Cochrane library), and meeting abstracts databases. A systematic analysis was conducted using Comprehensive Meta Analysis (version 2.2.048) software to calculate the odds ratio of response and 95% confidence interval. Median overall survival time for sensitive and resistant SCLC patients was compared by two-sided Student's t test. We tested for significant heterogeneity by Cochran's chi-square test and I-square index.

RESULTS

Twenty-one studies published between 1984 and 2011 were eligible for this analysis with a total of 1692 patients enrolled; 912 with sensitive and 780 with refractory SCLC. The overall response rate was 17.9% with a higher response rate of 27.7% (range, 0%-77%) for sensitive SCLC versus 14.8% (range, 0%-70%) for refractory patients; p=0.0001. Pooled overall odds ratio of response was 2.235 (95% confidence interval: 1.518-3.291; p=0.001) favoring patients with sensitive disease. Median overall survival time was 6.7 months with a weighted survival of 7.7 and 5.4 months for sensitive and refractory SCLC, respectively (p = 0.0035).

CONCLUSIONS

Refractory SCLC patients derive modest clinical benefit from second-line chemotherapy. However, response and survival outcomes are superior with chemosensitive disease.

The structure-activity relationships of A-ring-substituted aromathecin topoisomerase I inhibitors strongly support a camptothecin-like binding mode

Aromathecins are inhibitors of human topoisomerase I (Top1). These compounds are composites of several heteroaromatic systems, namely the camptothecins and indenoisoquinolines, and they possess notable Top1 inhibition and cytotoxicity when substituted at position 14. The SAR of these compounds overlaps with indenoisoquinolines, suggesting that they may intercalate into the Top1-DNA complex similarly. Nonetheless, the proposed binding mode for aromathecins is purely hypothetical, as an X-ray structure is unavailable. In the present communication, we have synthesized eight novel series of A-ring-substituted (positions 1-3) aromathecins, through a simple, modular route, as part of a comprehensive SAR study. Certain groups (such as 2,3-ethylenedioxy) moderately improve Top1 inhibition, and, often, antiproliferative activity, whereas other groups (2,3-dimethoxy and 3-substituents) attenuate bioactivity. Strikingly, these trends are very similar to those previously observed for the A-ring of camptothecins, and this considerable SAR overlap lends further support (in the absence of crystallographic data) to the hypothesis that aromathecins bind in the Top1 cleavage complex as interfacial inhibitors in a 'camptothecin-like' pose.

Cancer therapies utilizing the camptothecins: a review of the in vivo literature

This review summarizes the in vivo assessment-preliminary, preclinical, and clinical-of chemotherapeutics derived from camptothecin or a derivative. Camptothecin is a naturally occurring, pentacyclic quinoline alkaloid that possesses high cytotoxic activity in a variety of cell lines. Major limitations of the drug, including poor solubility and hydrolysis under physiological conditions, prevent full clinical utilization. Camptothecin remains at equilibrium in an active lactone form and inactive hydrolyzed carboxylate form. The active lactone binds to DNA topoisomerase I cleavage complex, believed to be the single site of activity. Binding inhibits DNA religation, resulting in apoptosis. A series of small molecule camptothecin derivatives have been developed that increase solubility, lactone stability and bioavailability to varying levels of success. A number of macromolecular agents have also been described wherein camptothecin(s) are covalently appended or noncovalently associated with the goal of improving solubility and lactone stability, while taking advantage of the tumor physiology to deliver larger doses of drug to the tumor with lower systemic toxicity. With the increasing interest in drug delivery and polymer therapeutics, additional constructs are anticipated. The goal of this review is to summarize the relevant literature for others interested in the field of camptothecin-based therapeutics, specifically in the context of biodistribution, dosing regimens, and pharmacokinetics with the desire of providing a useful source of comparative data. To this end, only constructs where in vivo data is available are reported. The review includes published reports in English through mid-2009.

p53 Regulates Cellular Resistance to Complement Lysis through Enhanced Expression of CD59

It has been recently hypothesized that the CD59 gene has two putative p53-responsive elements that may be involved in defense of host cells from damage by the complement system in inflammation. Here we have examined the roles of these putative p53-binding sequences within the CD59 gene in regulation of CD59 expression. We have shown that both of these potential responsive elements bind p53 in vitro. Knocking down expression of p53 using small interfering RNA led to a 6-fold decrease in CD59 protein expression in HeLa cells. We have previously observed a decrease of CD59 in camptothecin-induced apoptotic IMR32 cells, whereas expression was increased in the surviving fraction compared with untreated cells. Here, we have shown that these changes are associated with altered expression levels and acetylation status of p53. We have also shown that acetylation status of p53 regulates CD59 expression on cells exposed to inflammatory cytokines to model inflammation. Our data suggest that p53 and in vivo positive/negative regulators of p53 could be used to modulate susceptibility of tumor cells to complement lysis in chemotherapy.

A phase I study of OSI-211 and cisplatin as intravenous infusions given on days 1, 2 and 3 every 3 weeks in patients with solid cancers

BACKGROUND

OSI-211 (also known as NX211) is a liposomal preparation of the topoisomerase I inhibitor, lurtotecan, which has shown antitumor activity in phase I and II clinical trials. Cisplatin is a widely used antineoplastic agent with activity in a broad range of tumor types. This phase I trial was conducted to determine the recommended doses of these agents, and their pharmacokinetic properties and toxicities in patients with advanced solid malignancies.

PATIENTS AND METHODS

Fourteen patients with advanced and/or metastatic solid malignancies were enrolled in this trial. The first planned dose level was OSI-211 0.9 mg/m(2) with cisplatin 25 mg/m(2) administered intravenously daily for the first three consecutive days of a 21-day cycle. Patients were evaluated for hematological and non-hematological toxicities, and pharmacokinetic studies were performed on both agents.

RESULTS

The recommended phase II dose was determined to be 0.7 mg/m(2) OSI-211 given with 25 mg/m(2) cisplatin. Dose-limiting neutropenia was seen in two of three patients at the starting dose level. Three of 11 patients at the second (lower) dose level experienced dose-limiting thrombocytopenia; febrile neutropenia was also seen in one patient. Non-hematological toxicities were generally manageable and included fatigue, nausea and vomiting. Considerable variability was seen in both hematological toxicities and pharmacokinetics. One complete response and three partial responses were seen.

CONCLUSIONS

The recommended phase II dose for this combination is 0.7 mg/m(2) OSI-211 with 25 mg/m(2) cisplatin given as an intravenous infusion on days 1, 2 and 3 of a 21-day cycle. The main toxicity was myelosuppression. Preliminary evidence of antitumor activity was seen.

Phase I and pharmacokinetic study of a low-clearance, unilamellar liposomal formulation of lurtotecan, a topoisomerase 1 inhibitor, in patients with advanced leukemia

BACKGROUND

OSI-211 is a low-clearance, unilamellar liposomal formulation of a water-soluble camptothecin analogue, lurtotecan. OSI-211 has significant activity in severe combined immunodeficient mouse models of human leukemia.

METHODS

This study was conducted to define the dose-limiting toxicities (DLT) and pharmacokinetics of OSI-211 in patients with refractory myeloid leukemias. Patients with refractory acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), or chronic myelogenous leukemia in blastic phase (CML-BP) were eligible. OSI-211 was given as an intravenous infusion over 30 minutes daily for 3 days. The starting dose was 1.5 mg/m2 per day (4.5 mg/m2 per course). The dose was escalated by 50% until Grade 2 toxicity was observed and then by 30-35% until the DLT was defined. Serial plasma and urine samples were collected, and drug levels were determined by high-performance liquid chromatography with fluorescence detection.

RESULTS

Twenty patients (18 patients [90%] with AML, and 1 patient each [5%] with MDS and CML-BP) were treated. Mucositis and diarrhea were considered to be the DLTs. The maximum tolerated dose was 3.7 mg/m2 per day. Fourteen of 18 evaluable patients (78%) with AML or MDS achieved transient bone marrow aplasia. The mean systemic clearance of lurtotecan in plasma was 0.946 +/- 1.53 L/hour/m2. Urinary recovery of lurtotecan was 6.66% +/- 5.26% (range, 1.05-18.4%).

CONCLUSIONS

Liposomal encapsulation of lurtotecan altered its metabolism significantly. There was no evident correlation between exposure, as measured by plasma pharmacokinetics of lurtotecan, and clinical response or toxicities. OSI-211 merits further study in hematologic malignancies.

Second-line chemotherapy for small-cell lung cancer: a review

Small-cell lung cancer (SCLC) is an aggressive malignancy, and only a minority of patients survive 2 years. Although this cancer is sensitive to both chemotherapy and radiotherapy, the majority of patients relapse, and second-line treatment is an option for many. Currently in the United States, the combination of cisplatin/etoposide is the standard first-line therapy in SCLC. At this time, topotecan is the only Food and Drug Administration-approved chemotherapeutic agent for second-line treatment of SCLC. In this paper, we review studies of second-line chemotherapy for SCLC.

Phase I and pharmacologic study of liposomal lurtotecan, NX 211: urinary excretion predicts hematologic toxicity

PURPOSE

To determine the maximum-tolerated and recommended dose, toxicity profile, and pharmacokinetics of the liposomal topoisomerase I inhibitor lurtotecan (NX 211) administered as a 30-minute intravenous infusion once every 3 weeks in cancer patients.

PATIENTS AND METHODS

NX 211 was administered by peripheral infusion. Dose escalation decisions were based on all toxicities during the first cycle as well as pharmacokinetic parameters. Serial plasma, whole blood, and urine samples were collected for up to 96 hours after the end of infusion, and drug levels were determined by high-performance liquid chromatography.

RESULTS

Twenty-nine patients (16 women; median age, 56 years; range, 39 to 74 years) received 77 courses of NX 211 at dose levels of 0.4 (n = 3), 0.8 (n = 6), 1.6 (n = 3), 3.2 (n = 6), 3.8 (n = 6), and 4.3 mg/m(2) (n = 5). Neutropenia and thrombocytopenia were the dose-limiting toxicities and were not cumulative. Other toxicities were mild to moderate. Nine patients had stable disease while undergoing treatment. The systemic clearance of lurtotecan in plasma and whole blood was 0.82 +/- 0.78 L/h/m(2) and 1.15 +/- 0.96 L/h/m(2), respectively. Urinary recovery (Fu) of lurtotecan was 10.1% +/- 4.05% (range, 4.9% to 18.9%). In contrast to systemic exposure measures, the dose excreted in urine (ie, dose x Fu) was significantly related to the percent decrease in neutrophil and platelet counts at nadir (P <.00001).

CONCLUSION

The dose-limiting toxicities of NX 211 are neutropenia and thrombocytopenia. The recommended dose for phase II studies is 3.8 mg/m(2) once every 3 weeks. Pharmacologic data suggest a relationship between exposure to lurtotecan and NX 211-induced clinical effects.

Topoisomerase I targeting agents in small-cell lung cancer

The topoisomerase I inhibitors such as irinotecan and topotecan are active agents against small-cell lung cancer that are effective in treating not only chemotherapy-naïve tumors but also progressed-stage tumors after treatment with cisplatin-based regimens, because their mechanism of antitumor activity differs from that of the agents included in standard chemotherapy for small-cell lung cancer. Etoposide plus cisplatin or etoposide plus cisplatin alternating with cyclophosphamide, doxorubicin, and vincristine is considered the standard regimen for small-cell lung cancer. No new standard combination chemotherapy for small-cell lung cancer has been developed over the past decade. Irinotecan with cisplatin is now established as a new standard chemotherapy for extensive-stage small-cell lung cancer based on the results of the Japan Clinical Oncology Group trial. Of course, confirmation through phase III studies will be extremely important. The Japan Clinical Oncology Group is intensively investigating other irinotecan-containing regimens and the incorporation of irinotecan into treatment of patients with limited-stage small-cell lung cancer.