Phase I trial of UCN-01 in combination with topotecan in patients with advanced solid cancers: a Princess Margaret Hospital Phase II Consortium study

A Phase 1 study of UCN-01 in combination with irinotecan in patients with resistant solid tumor malignancies

PURPOSE

UCN-01 (7-hydroxystaurosporine) is a multi-targeted protein kinase inhibitor that exhibits synergistic activity with DNA-damaging agents in preclinical studies. We conducted a Phase I study to determine the maximum-tolerated dose (MTD), dose-limiting toxicity (DLT), pharmacokinetic, and pharmacodynamic effects of UCN-01 and irinotecan in patients with resistant solid tumors.

EXPERIMENTAL DESIGN

Patients received irinotecan (75-125 mg/m(2) IV on days 1, 8, 15, 22) and UCN-01 (50-90 mg/m(2) IV on day 2 and 25-45 mg/m(2) on day 23 and subsequent doses) every 42 days. Blood for pharmacokinetics of UCN-01 and irinotecan, and blood, normal rectal mucosa, and tumor biopsies for pharmacodynamic studies were obtained.

RESULTS

Twenty-five patients enrolled to 5 dose levels. The MTD was irinotecan 125 mg/m(2) on days 1, 8, 15, 22 and UCN-01 70 mg/m(2) on day 2 and 35 mg/m(2) on day 23. DLTs included grade 3 diarrhea/dehydration and dyspnea. UCN-01 had a prolonged half-life and a low clearance rate. There was a significant reduction in SN-38 C(max) and aminopentanocarboxylic acid (APC) and SN-38 glucuronide half-lives. Phosphorylated ribosomal protein S6 was reduced in blood, normal rectal mucosa, and tumor biopsies at 24 h post-UCN-01. Two partial responses were observed in women with ER, PgR, and HER2-negative breast cancers (TBNC). Both tumors were defective for p53. Twelve patients had stable disease (mean duration 18 weeks, range 7-30 weeks).

CONCLUSION

UCN-01 and irinotecan demonstrated acceptable toxicity and target inhibition. Anti-tumor activity was observed and a study of this combination in women with TNBC is underway.

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.

The release of microparticles by Jurkat leukemia T cells treated with staurosporine and related kinase inhibitors to induce apoptosis

Microparticles (MPs) are small membrane-bound vesicles released from cells undergoing activation or cell death. These particles display potent biological activities that can impact on physiologic and pathologic processes. Previous studies with the Jurkat T leukemia cell line demonstrated that staurosporine (STS) induces the release of MPs as cells undergo apoptosis. To investigate further this process, we tested the effects of STS, its analogue, 7-hydroxystaurosporine (UCN-01), and other protein kinase C (PKC) and cyclin-dependent kinase (CDK) inhibitors. FACS analysis was used to assess MP release. Results of these studies indicate that STS and UCN-01 induce MP release by Jurkat cells; in contrast, other PKC and CDK inhibitors failed to induce comparable release, suggesting that release does not result from simple inhibition of either kinase alone. Time course experiments indicated that STS-induced particle release occurred as early as 2 h after treatment, with the early release MPs displaying low levels of binding of annexin V and propidium iodide (PI). Early-release MPs, however, matured in culture to an annexin V- and PI-positive phenotype. Together, these results indicate that STS and UCN-01 induce MPs that are phenotypically distinct and reflect specific patterns of kinase inhibition during apoptosis.

Genetic instability and mammary tumor formation in mice carrying mammary-specific disruption of Chk1 and p53

Checkpoint kinase 1 (Chk1) is a key element in the DNA-damage response pathway that is required for maintaining genomic stability. To study the potential role of Chk1 in mammary tumorigenesis, we disrupted it using a Cre/loxP system. We showed that although Chk1 heterozygosity caused abnormal development of the mammary gland, it was not sufficient to induce tumorigenesis. Simultaneous deletion of one copy of p53 failed to rescue the developmental defects; however, it synergistically induced mammary tumor formation in Chk1(+/-);MMTV-Cre animals with a median time to tumor latency of about 10 months. Chk1 deficiency caused a preponderance of abnormalities, including prolongation, multipolarity, misalignment, mitotic catastrophe and loss of spindle checkpoint, that are accompanied by reduced expression of several cell cycle regulators, including Mad2. On the other hand, we also showed that Chk1 deficiency inhibited mammary tumor formation in mice carrying a homozygous deletion of p53, uncovering a complex relationship between Chk1 and p53. Furthermore, inhibition of Chk1 with a specific inhibitor, SB-218078, or acute deletion of Chk1 using small hairpin RNA killed mammary tumor cells effectively. These data show that Chk1 is critical for maintaining genome integrity and serves as a double-edged sword for cancer: although its inhibition kills cancer cells, it also triggers tumorigenesis when favorable mutations are accumulated for cell growth.

BRCA1 as a Therapeutic Target in Sporadic Epithelial Ovarian Cancer

In sporadic epithelial ovarian cancer (EOC), the inactivation of BRCA1 through various mechanisms is a relatively common event. BRCA1 protein dysfunction results in the breakdown of various critical pathways in the cell, notably, the DNA damage response and repair pathway. Tumors from patients with BRCA1 germline mutations have an increased sensitivity to DNA damaging chemotherapeutic agents, such as cisplatin, due to defective DNA repair. Thus, inhibiting BRCA1 in sporadic EOC using novel targeted therapies is an attractive strategy for the treatment of advanced or recurrent EOC. Several classes of small molecule inhibitors that affect BRCA1 have now been tested in preclinical and clinical studies suggesting that this is a rational therapeutic approach. The aim of this paper is to provide an understanding of how BRCA1 has evolved into a promising target for the treatment of sporadic disease and to outline the main potential small molecule inhibitors of BRCA1 in EOC.

Naphthalimides induce G(2) arrest through the ATM-activated Chk2-executed pathway in HCT116 cells

Naphthalimides, particularly amonafide and 2-(2-dimethylamino)-6-thia-2-aza-benzo[def]chrysene-1,3-diones (R16), have been identified to possess anticancer activities and to induce G(2)-M arrest through inhibiting topoisomerase II accompanied by Chk1 degradation. The current study was designed to precisely dissect the signaling pathway(s) responsible for the naphthalimide-induced cell cycle arrest in human colon carcinoma HCT116 cells. Using phosphorylated histone H3 and mitotic protein monoclonal 2 as mitosis markers, we first specified the G(2) arrest elicited by the R16 and amonafide. Then, R16 and amonafide were revealed to induce phosphorylation of the DNA damage sensor ataxia telangiectasia-mutated (ATM) responding to DNA double-strand breaks (DSBs). Inhibition of ATM by both the pharmacological inhibitor caffeine and the specific small interference RNA (siRNA) rescued the G(2) arrest elicited by R16, indicating its ATM-dependent characteristic. Furthermore, depletion of Chk2, but not Chk1 with their corresponding siRNA, statistically significantly reversed the R16- and amonafide-triggered G(2) arrest. Moreover, the naphthalimides phosphorylated Chk2 in an ATM-dependent manner but induced Chk1 degradation. These data indicate that R16 and amonafide preferentially used Chk2 as evidenced by the differential ATM-executed phosphorylation of Chk1 and Chk2. Thus, a clear signaling pathway can be established, in which ATM relays the DNA DSBs signaling triggered by the naphthalimides to the checkpoint kinases, predominantly to Chk2,which finally elicits G(2) arrest. The mechanistic elucidation not only favors the development of the naphthalimides as anticancer agents but also provides an alternative strategy of Chk2 inhibition to potentiate the anticancer activities of these agents.

A phase I trial of UCN-01 and prednisone in patients with refractory solid tumors and lymphomas

PURPOSE

UCN-01 potently inhibits protein kinase C, phosphatidylinositide-dependent kinase-1, and checkpoint kinase 1, which are involved in regulating cell cycle progression. We designed a phase I study to determine the maximum tolerated dose (MTD) of UCN-01 with prednisone in patients with advanced malignancies.

METHODS

UCN-01 was administered as a continuous intravenous infusion over 72 h in cycle 1 and 36 h in subsequent cycles. Prednisone was given orally at 60 mg/m(2) per day for five consecutive days within each 28-day cycle. Standard dose escalation was employed, and MTD was defined as the dose at which no more than one of six patients experienced a dose-limiting toxicity (DLT). Plasma pharmacokinetics of UCN-01 were assessed.

RESULTS

Fifteen patients received a total of 55 courses of treatment. The MTD and the recommended phase II dose of UCN-01 in this combination is 72 mg/m(2) total dose over 72 h for cycle 1 followed by 36 mg/m(2) per cycle over 36 h. All patients experienced hyperglycemia but responded to insulin treatment. Hypophosphatemia was a DLT in two patients. There were no cumulative toxicities. No objective responses were observed, but five patients had stable disease, including two patients with lymphoid malignancies who had prolonged disease stabilizations. UCN-01 has a long terminal half-life and low clearance; there was wide inter-patient variability in peak concentrations.

CONCLUSION

UCN-01 can be safely administered in combination with prednisone without unacceptable toxicity. The prolonged stable disease in two patients with lymphoid malignancies is a proof of principle for the evaluation of cyclin-dependent kinase inhibitors in oncology.

New molecular targets in radiotherapy: DNA damage signalling and repair in targeted and non-targeted cells

Ionising radiation plays a key role in therapy due to its ability to directly induce DNA damage, in particular DNA double-strand breaks leading to cell death. Cells have multiple repair pathways which attempt to maintain genomic stability. DNA repair proteins have become key targets for therapy, using small molecule inhibitors, in combination with radiation and or chemotherapeutic agents as a means of enhancing cell killing. Significant advances in our understanding of the response of cells to radiation exposures has come from the observation of non-targeted effects where cells respond via mechanisms other than those which are a direct consequence of energy-dependent DNA damage. Typical of these is bystander signalling where cells respond to the fact that their neighbours have been irradiated. Bystander cells show a DNA damage response which is distinct from directly irradiated cells. In bystander cells, ATM- and Rad3-related (ATR) protein kinase-dependent signalling in response to stalled replication forks is an early event in the DNA damage response. The ATM protein kinase is activated downstream of ATR in bystander cells. This offers the potential for differential approaches for the modulation of bystander and direct effects with repair inhibitors which may impact on the response of tumours and on the protection of normal tissues during radiotherapy.

CHK1 inhibition as a strategy for targeting Fanconi Anemia (FA) DNA repair pathway deficient tumors

Background

DNA repair deficient tumor cells have been shown to accumulate high levels of DNA damage. Consequently, these cells become hyper-dependent on DNA damage response pathways, including the CHK1-kinase-mediated response. These observations suggest that DNA repair deficient tumors should exhibit increased sensitivity to CHK1 inhibition. Here we offer experimental evidence in support of this hypothesis.

Results

Using isogenic pairs of cell lines differing only in the Fanconi Anemia (FA) DNA repair pathway, we showed that FA deficient cell lines were hypersensitive to CHK1 silencing by independent siRNAs as well as CHK1 pharmacologic inhibition by Gö6976 and UCN-01. In parallel, an siRNA screen designed to identify gene silencings synthetically lethal with CHK1 inhibition identified genes required for FA pathway function. To confirm these findings in vivo, we demonstrated that whole zebrafish embryos, depleted for FANCD2 by a morpholino approach, were hypersensitive to Gö6976. Silencing of FA genes led to hyper-activation of CHK1 and vice versa. Furthermore, inactivation of CHK1 in FA deficient cell lines caused increased accumulation of DNA strand and chromosomal breakages. These results suggest that the functions subserved by CHK1 and the FA pathway mutually compensate in maintaining genome integrity. As CHK1 inhibition has been under clinical trial in combination with cisplatin, we showed that the FA specific tumoricidal effect of CHK1 inhibition and cisplatin was synergistic.

Conclusion

Taken together, these results suggest CHK1 inhibition as a strategy for targeting FA deficient tumors.

Centrosome-associated regulators of the G(2)/M checkpoint as targets for cancer therapy

In eukaryotic cells, control mechanisms have developed that restrain cell-cycle transitions in response to stress. These regulatory pathways are termed cell-cycle checkpoints. The G(2)/M checkpoint prevents cells from entering mitosis when DNA is damaged in order to afford these cells an opportunity to repair the damaged DNA before propagating genetic defects to the daughter cells. If the damage is irreparable, checkpoint signaling might activate pathways that lead to apoptosis. Since alteration of cell-cycle control is a hallmark of tumorigenesis, cell-cycle regulators represent potential targets for therapy. The centrosome has recently come into focus as a critical cellular organelle that integrates G(2)/M checkpoint control and repairs signals in response to DNA damage. A growing number of G(2)/M checkpoint regulators have been found in the centrosome, suggesting that centrosome has an important role in G(2)/M checkpoint function. In this review, we discuss centrosome-associated regulators of the G(2)/M checkpoint, the dysregulation of this checkpoint in cancer, and potential candidate targets for cancer therapy.

Keeping checkpoint kinases in line: new selective inhibitors in clinical trials

BACKGROUND

Checkpoint kinase 1 (Chk1), a serine/threonine kinase, functions as a regulatory kinase in cell cycle progression and is a critical effector of the DNA-damage response. Inhibitors of Chk1 are known to sensitise tumours to a variety of DNA-damaging agents and increase efficacy in preclinical models.

OBJECTIVE

The most advanced agents are now in Phase I clinical trials; the preclinical profiles of these drugs are compared and contrasted, together with a discussion of some of the opportunities and challenges facing this potentially revolutionary approach to cancer therapy.

METHODS

A review of the publications and presentations on XL-844, AZD7762 and PF-477736.

RESULTS/CONCLUSIONS

Chk kinases are part of the DNA damage recognition and response pathways and as such represent attractive targets. Agents that target checkpoint kinases have demonstrated impressive evidence preclinically that this approach will provide tumour-specific potentiating agents and may have broad therapeutic utility.

Nucleoside analogs: molecular mechanisms signaling cell death

Nucleoside analogs are structurally similar antimetabolites that have a broad range of action and are clinically active in both solid tumors and hematological malignancies. Many of these agents are incorporated into DNA by polymerases during normal DNA synthesis, an action that blocks further extension of the nascent strand and causes stalling of replication forks. The molecular mechanisms that sense stalled replication forks activate cell cycle checkpoints and DNA repair processes, which may contribute to drug resistance. When replication forks are not stabilized by these molecules or when subsequent DNA repair processes are overwhelmed, apoptosis is initiated either by these same DNA damage sensors or by alternative mechanisms. Recently, strategies aimed at targeting DNA damage checkpoints or DNA repair processes have demonstrated effectiveness in sensitizing cells to nucleoside analogs, thus offering a means to elude drug resistance. In addition to their DNA synthesis-directed actions many nucleoside analogs trigger apoptosis by unique mechanisms, such as causing epigenetic modifications or by direct activation of the apoptosome. A review of the cellular and molecular responses to clinically relevant agents provides an understanding of the mechanisms that cause apoptosis and may provide rationale for the development of novel therapeutic strategies.

Transient exposure of carcinoma cells to RAS/MEK inhibitors and UCN-01 causes cell death in vitro and in vivo

The present studies were initiated to determine in greater molecular detail how MEK1/2 inhibitors [PD184352 and AZD6244 (ARRY-142886)] interact with UCN-01 (7-hydroxystaurosporine) to kill mammary carcinoma cells in vitro and radiosensitize mammary tumors in vitro and in vivo and whether farnesyl transferase inhibitors interact with UCN-01 to kill mammary carcinoma cells in vitro and in vivo. Expression of constitutively activated MEK1 EE or molecular suppression of JNK and p38 pathway signaling blocked MEK1/2 inhibitor and UCN-01 lethality, effects dependent on the expression of BAX, BAK, and, to a lesser extent, BIM and BID. In vitro colony formation studies showed that UCN-01 interacted synergistically with the MEK1/2 inhibitors PD184352 or AZD6244 and the farnesyl transferase inhibitors FTI277 and R115,777 to kill human mammary carcinoma cells. Athymic mice carrying approximately 100 mm(3) MDA-MB-231 cell tumors were subjected to a 2-day exposure of either vehicle, R115,777 (100 mg/kg), the MEK1/2 inhibitor PD184352 (25 mg/kg), UCN-01 (0.2 mg/kg), or either of the drugs in combination with UCN-01. Transient exposure of tumors to R115,777, PD184352, or UCN-01 did not significantly alter tumor growth rate or the mean tumor volume in vivo approximately 15 to 30 days after drug administration. In contrast, combined treatment with R115,777 and UCN-01 or with PD184352 and UCN-01 significantly reduced tumor growth. Tumor cells isolated after combined drug exposure exhibited a significantly greater reduction in plating efficiency using ex vivo colony formation assays than tumor cells that were exposed to either drug individually. Irradiation of mammary tumors after drug treatment, but not before or during treatment, significantly enhanced the lethal effects of UCN-01 and MEK1/2 inhibitor treatment. These findings argue that UCN-01 and multiple inhibitors of the RAS-MEK pathway have the potential to suppress mammary tumor growth, and to interact with radiation, in vitro and in vivo.

Synthesis, checkpoint kinase 1 inhibitory properties and in vitro antiproliferative activities of new pyrrolocarbazoles

In the course of structure-activity relationship studies on granulatimide analogues, new pyrrolo[3,4-c]carbazoles have been synthesized in which the imidazole heterocycle was replaced by a five-membered ring lactam system or a dimethylcyclopentanedione. Moreover, the synthesis of an original structure in which a sugar moiety is attached to the indole nitrogen and to a six-membered D ring via an oxygen is reported. The inhibitory activities of the newly synthesized compounds toward checkpoint kinase 1 and their in vitro antiproliferative activities toward three tumor cell lines: murine leukemia L1210, and human colon carcinoma HT29 and HCT116 are described.

GSK-3 beta targets Cdc25A for ubiquitin-mediated proteolysis, and GSK-3 beta inactivation correlates with Cdc25A overproduction in human cancers

The Cdc25A phosphatase positively regulates cell-cycle transitions, is degraded by the proteosome throughout interphase and in response to stress, and is overproduced in human cancers. The kinases targeting Cdc25A for proteolysis during early cell-cycle phases have not been identified, and mechanistic insight into the cause of Cdc25A overproduction in human cancers is lacking. Here, we demonstrate that glycogen synthase kinase-3beta (GSK-3beta) phosphorylates Cdc25A to promote its proteolysis in early cell-cycle phases. Phosphorylation by GSK-3beta requires priming of Cdc25A, and this can be catalyzed by polo-like kinase 3 (Plk-3). Importantly, a strong correlation between Cdc25A overproduction and GSK-3beta inactivation was observed in human tumor tissues, indicating that GSK-3beta inactivation may account for Cdc25A overproduction in a subset of human tumors.

Synthesis and biological activities of new checkpoint kinase 1 inhibitors structurally related to granulatimide

In the course of structure-activity relationship studies on granulatimide analogues, new pyrrolo[3,4-c]carbazoles in which the imidazole heterocycle has been replaced by a five- or a six-membered ring bearing one or two carbonyl functions have been synthesized. Their checkpoint kinase 1 (Chk1) inhibitory properties and their in vitro antiproliferative activities toward three tumor cell lines-murine leukemia L1210 and human colon carcinoma HT29 and HCT116 have been determined. The results of molecular modeling in the ATP binding pocket of Chk1 are described. Among the newly synthesized compounds, compounds 13 and 16, in which the imidazole was replaced by a quinone and a hydroquinone and which bear a hydroxy group on the indole moiety, are the most potent Chk1 inhibitors in this series with IC50 values of 27 and 23 nM, respectively.

Targeting checkpoint kinase 1 in cancer therapeutics

Progression through the cell cycle is monitored by surveillance mechanisms known as cell cycle checkpoints. Our knowledge of the biochemical nature of checkpoint regulation during an unperturbed cell cycle and following DNA damage has expanded tremendously over the past decade. We now know that dysfunction in cell cycle checkpoints leads to genomic instability and contributes to tumor progression, and most agents used for cancer therapy, such as cytotoxic chemotherapy and ionizing radiation, also activate cell cycle checkpoints. Understanding how checkpoints are regulated is therefore important from the points of view of both tumorigenesis and cancer treatment. In this review, we present an overview of the molecular hierarchy of the checkpoint signaling network and the emerging role of checkpoint targets, especially checkpoint kinase 1, in cancer therapy. Further, we discuss the results of recent clinical trials involving the nonspecific checkpoint kinase 1 inhibitor, UCN-01, and the challenges we face with this new therapeutic approach.

Biochemical and cellular characterization of VRX0466617, a novel and selective inhibitor for the checkpoint kinase Chk2

VRX0466617 is a novel selective small-molecule inhibitor for Chk2 discovered through a protein kinase screening program. In this study, we provide a detailed biochemical and cellular characterization of VRX0466617. We show that VRX0466617 blocks the enzymatic activity of recombinant Chk2, as well as the ionizing radiation (IR)-induced activation of Chk2 from cells pretreated with the compound, at doses between 5 and 10 micromol/L. These doses of VRX0466617 inhibited, to some extent, the phosphorylation of Chk2 Ser(19) and Ser(33-35), but not of Chk2 Thr(68), which is phosphorylated by the upstream ataxia-telangiectasia mutated (ATM) kinase. Interestingly, VRX0466617 induced the phosphorylation of Chk2 Thr(68) even in the absence of DNA damage, arising from the block of its enzymatic activity. VRX0466617 prevented the IR-induced Chk2-dependent degradation of Hdmx, concordant with the in vivo inhibition of Chk2. Analysis of ATM/ATM and Rad3-related substrates Smc1, p53, and Chk1 excluded a cross-inhibition of these kinases. VRX0466617 did not modify the cell cycle phase distribution, although it caused an increase in multinucleated cells. Whereas VRX0466617 attenuated IR-induced apoptosis, in short-term assays it did not affect the cytotoxicity by the anticancer drugs doxorubicin, Taxol, and cisplatin. These results underscore the specificity of VRX0466617 for Chk2, both in vitro and in vivo, and support the use of this compound as a biological probe to study the Chk2-dependent pathways.

MEK1/2 inhibitors potentiate UCN-01 lethality in human multiple myeloma cells through a Bim-dependent mechanism

The role of Bim in synergistic interactions between UCN-01 and MEK1/2 inhibitors in human multiple myeloma cells was investigated. Exposure of U266 or RPMI8226 cells to UCN-01 resulted in ERK1/2 activation-associated Bim(EL) phosphorylation/down-regulation, events abrogated by MEK1/2 inhibitors. Enforced activation of ERK1/2 by transfection with constitutively active MEK1 diminished the capacity of PD98059 but not PD184352 to block UCN-01-mediated Bim(EL) phosphorylation and to potentiate apoptosis. Cotreatment with MEK1/2 inhibitors increased the association of Bim(EL) with both Bcl-2 and Bcl-x(L) in UCN-01-treated cells, leading to Bax/Bak conformational change and Bax mitochondrial translocation. Down-regulation of Bim(EL) by shRNA substantially diminished UCN-01/MEK inhibitor-mediated Bax/Bak activation and apoptosis. Furthermore, transfection of cells with S65A Bim, a mutant resistant to UCN-01-mediated phosphorylation, significantly sensitized cells to UCN-01 lethality. Conversely, ectopic expression of either Bcl-2 or Bcl-x(L) did not alter UCN-01/MEK1/2 inhibitor-mediated modifications in Bim(EL) phosphorylation but largely prevented cell death. Finally, IL-6 or IGF-1 failed to prevent MEK1/2 inhibitors from blocking UCN-01-induced Bim(EL) phosphorylation/degradation or cell death. Collectively, these findings argue that UCN-01-mediated ERK1/2 activation leads to Bim(EL) phosphorylation/inactivation, resulting in cytoprotection, and that interference with these events by MEK1/2 inhibitors plays a critical role in synergistic induction of apoptosis by these agents.

UCN-01 in combination with topotecan in patients with advanced recurrent ovarian cancer: a study of the Princess Margaret Hospital Phase II consortium

BACKGROUND AND OBJECTIVE

UCN-01 is a staurosporine analogue shown to abrogate the G2 checkpoint through inhibition of cyclin-dependent kinases. Preclinical evidence suggests synergy between UCN-01 and cytotoxic chemotherapy. Topotecan is an active agent in ovarian cancer. This phase II study was conducted to investigate the safety and efficacy of topotecan and UCN-01 in patients with advanced ovarian cancer.

METHODS

A two-stage phase II trial was designed for patients with advanced ovarian cancer with progressive disease despite prior treatment with platinum and paclitaxel. Patients with advanced ovarian cancer were treated with topotecan, 1 mg/m(2) IV, days 1 to 5, and UCN-01 70 mg/m(2) on day 1 of the first cycle, and 35 mg/m(2) on day 1 of all subsequent cycles. Treatment was repeated on a 3-week cycle. The primary objective of this study was objective response rate while secondary objectives included rates of stable disease, duration of response, progression-free and overall survival, as well as toxicity. Tumor biopsy specimens were also collected where possible for molecular correlative studies.

RESULTS

Twenty-nine patients are evaluable for toxicity and efficacy. Three patients (10%) achieved a partial response. The median time to progression was 3.3 months (95% CI 1.5-NA), and the median overall survival was 9.7 months (95% CI: 7.5-15.3). The most common grade 3-4 toxicities were neutropenia (79%), anemia (41%), thrombocytopenia (14%), hyperglycemia (10%), and pain (10%).

CONCLUSION

The combination of UCN-01 and topotecan is generally well tolerated, however, this combination is not considered to have significant antitumor activity against advanced ovarian cancer.

Inhibition of topoisomerase IIα and G2 cell cycle arrest by NK314, a novel benzo[c]phenanthridine currently in clinical trials

NK314 is a novel synthetic benzo[c]phenanthridine alkaloid that has recently entered clinical trials as an antitumor compound, based on impressive activities in preclinical models. The present investigations were directed at determining the mechanism of action of this agent. NK314 induced significant G(2) cell cycle arrest in several cell lines, independent of p53 status, suggesting the existence of a common mechanism of checkpoint activation. The Chk1-Cdc25C-Cdk1 G(2) checkpoint pathway was activated in response to 100 nmol/L NK314 in ML-1 human acute myeloid leukemia cells. This was associated with the phosphorylation of the histone variant H2AX, an action that was predominant in the G(2) population, suggesting that double-strand DNA breaks caused cells to activate the checkpoint pathway. Double-strand DNA breaks were visualized as chromosomal aberrations when the G(2) checkpoint was abrogated by 7-hydroxystaurosporine. In vitro assays showed that NK314 inhibited the ability of topoisomerase IIalpha to relax supercoiled DNA and trapped topoisomerase IIalpha in its cleavage complex intermediate. CEM/VM1 cells, which are resistant to etoposide due to mutations in topoisomerase IIalpha, were cross-resistant to NK314. However, CEM/C2 cells, which are resistant to camptothecin due to mutations in topoisomerase I, retained sensitivity. These findings support the conclusion that the major mechanism of NK314 is to inhibit topoisomerase IIalpha, an action that leads to the generation of double-strand DNA breaks, which activate the G(2) DNA damage checkpoint pathway.

Phase I and Pharmacokinetic Study of 7-Hydroxystaurosporine and Carboplatin in Advanced Solid Tumors

PURPOSE

Based on preclinical data showing synergy between 7-hydroxystaurosporine (UCN-01) and platinum agents, a phase I trial of carboplatin with UCN-01 administered as a 3 h infusion in patients with advanced solid tumors was done. The primary goals of this trial were to evaluate the tolerability of this combination and the pharmacokinetics of UCN-01 when administered over 3 h and to compare the tolerability and pharmacokinetics with previously described schedules.

PATIENTS AND METHODS

Patients with advanced solid tumors, good performance status, normal organ function, and no potentially curative therapy were eligible for the trial. Carboplatin was escalated from an area under the curve (AUC) of 3 to an AUC of 5. UCN-01 was escalated from 50 to 90 mg/m(2).

RESULTS

Twenty-three patients with advanced solid tumors (20 with prior platinum treatment) received a total of 60 cycles of therapy. Full doses of both agents (carboplatin AUC 5, UCN-01 90 mg/m(2) in cycle 1, 45 mg/m(2) in subsequent cycles) could be administered. The major toxicity noted was hypotension, which could be abrogated with the use of saline prehydration and posthydration. No responses were seen; however, seven patients were able to receive more than two courses of therapy. Of note, two of three patients with refractory, progressive small cell lung cancer were able to receive six cycles of therapy without evidence of progression. One patient experienced resolution of paraneoplastic syndrome of inappropriate antidiuretic hormone. The pharmacokinetic variables C(max) and t(1/2) of the 3 h infusion were essentially identical to those previously observed when UCN-01 was administered over 72 h. The average t(1/2) for cycle 1 was 506 +/- 301 h, and the mean C(max) for all dose levels was >30 micromol/L. The mean AUC over the dosing interval for each dose level ranged from approximately 6,000 to 9,000 micromol/L h. Thus, the AUC of UCN-01 after the 3 h infusion was lower than was observed after a 72 h infusion.

CONCLUSION

The regimen of carboplatin and UCN-01 (administered as a 3 h infusion) was well tolerated. Further development of this combination, particularly in small cell lung cancer, is warranted.

Phase I and pharmacokinetic study of UCN-01 in combination with irinotecan in patients with solid tumors

PURPOSE

7-Hydroxystaurosporine (UCN-01) is a protein kinase inhibitor that inhibits several serine-threonine kinases including PKC and PDK1. Due to the preclinical synergistic effects seen with topoisomerase I inhibitors and non-overlapping toxicity, UCN-01 and irinotecan were combined in a dose-finding study designed to determine the maximum tolerated dose (MTD), toxicity profile, and pharmacokinetics (PK) of UCN-01 and irinotecan.

METHODS

Patients with incurable solid malignancies received UCN-01 intravenously (IV) as a 3-h infusion on day 1 and irinotecan IV over 90 min on days 1 and 8 of a 21-day cycle. Doses of UCN-01 for subsequent cycles were half the starting dose. Dose level 1 (DL1) consisted of UCN-01 and irinotecan doses of 50 and 60 mg/m(2), respectively. Blood samples were collected in cycle 1 for UCN-01, irinotecan, and irinotecan metabolites.

RESULTS

A total of 16 patients were enrolled on the trial at UCN-01/Irinotecan doses of 50/60 mg/m(2) (DL1; n = 1), 70/60 mg/m(2) (DL2; n = 6), 90/60 mg/m(2) (DL3; n = 4), and 70/90 mg/m(2) (DL4; n = 5). Two dose-limiting toxicities were observed each in DL3 and DL4 (2 grade 3 hypophosphatemia, 1 grade 4 hyperglycemia and grade 3 hypophosphatemia, 1 grade 4 febrile neutropenia). Fatigue, diarrhea, nausea, and anorexia were the most prevalent toxicities. No objective responses were documented, and four patients had stable disease for at least ten cycles. The long half-life (292.0 +/- 135.7 h), low clearance (0.045 +/- 0.038 l/h), and volume of distribution (14.3 +/- 5.9 l) observed for UCN-01 are consistent with prior UCN-01 data. There was a significant decrease in C(max) of APC, AUC of APC and SN-38, and AUC ratio of SN-38:irinotecan when comparing days 1 and 8 PK.

CONCLUSIONS

APC and SN-38 exposure decreased when administered in combination with UCN-01. The MTD of the combination based on protocol criteria was defined as 70 mg/m(2) of UCN-01 on day 1 and 60 mg/m(2) of irinotecan on days 1 and 8 in a 21-day cycle.

Dissecting the roles of checkpoint kinase 1/CDC2 and mitogen-activated protein kinase kinase 1/2/extracellular signal-regulated kinase 1/2 in relation to 7-hydroxystaurosporine-induced apoptosis in human multiple myeloma cells

The functional roles of Cdc2 and checkpoint kinase 1 (Chk1) in synergistic interactions between 7-hydroxystaurosporine (UCN-01) and mitogen-activated protein kinase kinase 1/2 (MEK1/2) inhibitors [e.g., 2-(2-chloro-4-iodophenylamino)-N-cyclopropylmethoxy-3,4-difluorobenzamide (PD184352)] were examined in human multiple myeloma cells in relation to MEK1/2/ERK1/2 activation and lethality. Time course studies revealed that MEK1/2/extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation preceded Cdc2 dephosphorylation (Tyr15) after UCN-01 exposure. Furthermore, enforced expression of Cdc2 or small inducible RNA (siRNA)-mediated Cdc2 knockdown failed to modify ERK1/2 activation status in either the presence or absence of UCN-01, arguing against a causal relationship between these events. However, ectopic expression of Cdc2 sensitized cells to the lethality of UCN-01/MEK inhibitor regimen, whereas Cdc2 knockdown by siRNA significantly diminished the lethal effects of this combination. Conversely, Chk1 knockdown by siRNA enhanced lethality mediated by UCN-01/PD184352. It is interesting that Chk1 knockdown reduced basal ERK1/2 activation and antagonized the ability of UCN-01 to activate ERK1/2. Finally, ectopic expression of constitutively active MEK1 significantly protected cells from the UCN-01/MEK1/2 inhibitor regimen without modifying Cdc2 activation status. Together, these findings indicate that although UCN-01-mediated Chk1 inhibition and Cdc2 activation are unlikely to be responsible for MEK1/2/ERK1/2 activation, both of these events contribute functionally to enhanced lethality in cells coexposed to MEK inhibitors. They also suggest a role for Chk1 in UCN-01-induced ERK1/2 activation, implying the existence of a heretofore unrecognized link between Chk1 and ERK1/2 signaling.