Phase II study of CI-980 (NSC 635370) in patients with previously treated advanced soft-tissue sarcomas

Breast cancer: Muscarinic receptors as new targets for tumor therapy

The development of breast cancer is a complex process that involves the participation of different factors. Several authors have demonstrated the overexpression of muscarinic acetylcholine receptors (mAChRs) in different tumor tissues and their role in the modulation of tumor biology, positioning them as therapeutic targets in cancer. The conventional treatment for breast cancer involves surgery, radiotherapy, and/or chemotherapy. The latter presents disadvantages such as limited specificity, the appearance of resistance to treatment and other side effects. To prevent these side effects, several schedules of drug administration, like metronomic therapy, have been developed. Metronomic therapy is a type of chemotherapy in which one or more drugs are administered at low concentrations repetitively. Recently, two chemotherapeutic agents usually used to treat breast cancer have been considered able to activate mAChRs. The combination of low concentrations of these chemotherapeutic agents with muscarinic agonists could be a useful option to be applied in breast cancer treatment, since this combination not only reduces tumor cell survival without affecting normal cells, but also decreases pathological neo-angiogenesis, the expression of drug extrusion proteins and the cancer stem cell fraction. In this review, we focus on the previous evidences that have positioned mAChRs as relevant therapeutic targets in breast cancer and analyze the effects of administering muscarinic agonists in combination with conventional chemotherapeutic agents in a metronomic schedule.

Microtubule-binding agents: a dynamic field of cancer therapeutics

Microtubules are dynamic filamentous cytoskeletal proteins composed of tubulin and are an important therapeutic target in tumour cells. Agents that bind to microtubules have been part of the pharmacopoeia of anticancer therapy for decades and until the advent of targeted therapy, microtubules were the only alternative to DNA as a therapeutic target in cancer. The screening of a range of botanical species and marine organisms has yielded promising new antitubulin agents with novel properties. In the current search for novel microtubule-binding agents, enhanced tumour specificity, reduced neurotoxicity and insensitivity to chemoresistance mechanisms are the three main objectives.

A phase II study of CI-980 in previously untreated extensive small cell lung cancer: an Ohio State University phase II research consortium study

CI-980, (ethyl (S)-(5-amino-1,2-dihydro-2-methyl-3-phenylpyrido[3,4-b] pyrazine-7-yl) carbamate 2-hydroxyethansulfonate (1:1)), is a water-soluble mitotic inhibitor. It acts by binding to the colchicine-binding site on tubulin, a site different from that of the vinca alkaloids, inhibiting tubulin polymerization. Cells exposed to CI-980 accumulate in M phase and die. In preclinical tumor models, CI-980 showed a broad spectrum of activity, including in multi-drug resistant tumor cell lines, with activity at least equal to that of vincristine. Extensive small cell lung cancer, despite its responsiveness to chemotherapy, is usually an incurable disease with survival in patients of less than one year. Due to the preclinical activity of CI-980 and its similar mechanism of action to drugs effective in small cell lung cancer, a phase II trial in extensive small cell lung cancer was initiated by The Ohio State University Phase II Research Consortium. A "window of opportunity" design was chosen where a short six-week trial of the drug was given unless there was significant objective response. Twelve patients were entered in the study and underwent a total of 16 cycles of chemotherapy. The median age of the patients was 54 years old (range 34-71) and performance status was ECOG 0 (four patients), ECOG 1 (seven patients), and ECOG 2 (one patient). The patients were treated with a 72-hr infusion at a dose of 4.5 mg/m2/day. Toxicity was predominantly myelosuppression with granulocytopenia (nine episodes), and anemia (seven episodes). There were no objective responses with 11 patients being removed from study due to progressive disease. Evaluation of leukocyte microtubule structure in peripheral blood revealed microtubule depolymerization, which was seen after treatment (t = 72 hr) and was reversible within 24 hr of stopping the drug. We conclude that despite antitumor activity demonstrated in preclinical studies, CI-980 does not have biological activity in previously untreated small cell lung cancer at this dose and infusion protocol.

Phase II trial of CI-980 in patients with disseminated malignant melanoma and no prior chemotherapy. A Southwest Oncology Group study

Malignant melanoma is increasing in frequency at a rapid rate in the United States. Metastatic disease is chemoresistant with DTIC considered the most active single agent. CI-980 is a synthetic mitotic inhibitor that blocks the assembly of tubulin and microtubules. It has shown cytotoxic activity against a broad spectrum of murine and human tumor cell tines. CI-980 can cross the blood brain barrier, is effective when given orally or parenterally, and is active against multidrug resistant cell lines overexpressing P-glycoprotein. In this trial, patients with disseminated melanoma with measurable disease, SWOG performance status of 0-1, no prior chemotherapy or immunotherapy for metastatic disease, and adequate hepatic and renal function, were enrolled. Treatment with CI-980 was given by 72 h continuous i.v. infusion at a dose of 4.5 mg/m2/day, days 1-3 every 21 days. Twenty-four patients were registered on this study with no patients ineligible. They ranged in age from 33-78 with performance status of 0 in 15 patients and 1 in 9 patients. Nineteen patients had visceral disease with 12 having liver involvement. There were no confirmed responses. The overall response rate was 0% (95% CI 0%-14%). The median overall survival is eleven months (95% CI 4-14 months). The most common toxicities were hematologic and consisted of leukopenia/granulocytopenia and anemia, with nausea/vomiting and malaise/fatigue/weakness also frequent. CI-980 administered at this dose and schedule has insufficient activity in the treatment of disseminated malignant melanoma to warrant further investigation.

CI-980 in advanced melanoma and hormone refractory prostate cancer

INTRODUCTION

CI-980 is a novel chemotherapeutic agent that inhibits polymerization of tubulin. Preclinical studies have indicated a high level activity of this agent against various tumor cell lines.

METHODS

13 malignant melanoma patients who had failed prior chemotherapy and/or immunotherapy and 13 hormone refractory prostate cancer patients, including 4 who had received prior chemotherapy, were treated in 2 separate NCI-supported clinical trials. Subjects received a recommended phase II dose of CI-980 of 4.5 mg/m2/day by continuous infusion for 72 hours every 3 weeks.

RESULTS

No activity was seen in either study. Toxicity was tolerable with neutropenia being the most common, significant toxicity. Among the melanoma patients, 15% and 31% developed grade 3 and grade 4 neutropenia, while 7% and 38% of the prostate patients developed grade 3 and grade 4 neutropenia, respectively.

CONCLUSIONS

CI-980 at this dose and schedule is ineffective against malignant melanoma and hormone refractory prostate cancer.