Pancreatic ductal adenocarcinoma (PDA) is among the most lethal human cancers in part because it is insensitive to many chemotherapeutic drugs. Studying a mouse model of PDA that is refractory to the clinically used drug gemcitabine, we found that the tumors in this model were poorly perfused and poorly vascularized, properties that are shared with human PDA. We tested whether the delivery and efficacy of gemcitabine in the mice could be improved by coadministration of IPI-926, a drug that depletes tumor-associated stromal tissue by inhibition of the Hedgehog cellular signaling pathway. The combination therapy produced a transient increase in intratumoral vascular density and intratumoral concentration of gemcitabine, leading to transient stabilization of disease. Thus, inefficient drug delivery may be an important contributor to chemoresistance in pancreatic cancer.

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Inhibition of Hedgehog Signaling Enhances Delivery of Chemotherapy in a Mouse Model of Pancreatic Cancer

Breast cancer is the most common cancer and the second leading cause of cancer death in American women It was the second most common cancer in the world in 2002, with more than 1 million new cases Despite advances in early detection and the understanding of the molecular bases of breast cancer biology, about 30% of patients with early-stage breast cancer have recurrent disease To offer more effective and less toxic treatment, selecting therapies requires considering the patient and the clinical and molecular characteristics of the tumor Systemic treatment of breast cancer includes cytotoxic, hormonal, and immunotherapeutic agents These medications are used in the adjuvant, neoadjuvant, and metastatic settings In general, systemic agents are active at the beginning of therapy in 90% of primary breast cancers and 50% of metastases However, after a variable period of time, progression occurs At that point, resistance to therapy is not only common but expected Herein we review general mechanisms of drug resistance, including multidrug resistance by P-glyucoprotein and the multidrug resistance protein family in association with specific agents and their metabolism, emergence of refractory tumors associated with multiple resistance mechanisms, and resistance factors unique to host-tumor-drug interactions Important anticancer agents specific to breast cancer are described

Overview of Resistance to Systemic Therapy in Patients with Breast Cancer

Phase I clinical trials are an essential step in the development of anticancer drugs. The main goal of these studies is to establish the recommended dose and/or schedule of new drugs or drug combinations for phase II trials. The guiding principle for dose escalation in phase I trials is to avoid exposing too many patients to subtherapeutic doses while preserving safety and maintaining rapid accrual. Here we review dose escalation methods for phase I trials, including the rule-based and model-based dose escalation methods that have been developed to evaluate new anticancer agents. Toxicity has traditionally been the primary endpoint for phase I trials involving cytotoxic agents. However, with the emergence of molecularly targeted anticancer agents, potential alternative endpoints to delineate optimal biological activity, such as plasma drug concentration and target inhibition in tumor or surrogate tissues, have been proposed along with new trial designs. We also describe specific methods for drug combinations as well as methods that use a time-to-event endpoint or both toxicity and efficacy as endpoints. Finally, we present the advantages and drawbacks of the various dose escalation methods and discuss specific applications of the methods in developmental oncotherapeutics.

/pdf/dose-escalation-methods-in-phase-i-cancer-clinical-trials-5amv4ii1cc.pdf

Dose Escalation Methods in Phase I Cancer Clinical Trials

Cellular pharmacology of gemcitabine

PURPOSE: Few chemotherapy agents are active in leiomyosarcoma (LMS), particularly LMS that has progressed after doxorubicin treatment. We sought to determine the response to gemcitabine plus docetaxel among patients with LMS. PATIENTS AND METHODS: Patients with unresectable LMS of uterine (n = 29) or other (n = 5) primary sites who did not respond to zero to two prior chemotherapy regimens were enrolled onto a phase II study of gemcitabine 900 mg/m2 intravenously (IV) on days 1 and 8 plus docetaxel 100 mg/m2 IV on day 8 with granulocyte colony-stimulating factor given subcutaneously on days 9 to 15, delivered every 21 days. Patients with prior pelvic radiation received 25% lower doses of both agents. Gemcitabine was delivered over 30 or 90 minutes in cycles 1 and 2 and by 90-minute infusion in all subsequent cycles. Pharmacokinetic studies assessed in vivo differences in gemcitabine concentrations with different rates of infusion. RESULTS: Thirty-four patients (median age, 55 years; range, 32 to 74 years)...

Gemcitabine and Docetaxel in Patients With Unresectable Leiomyosarcoma: Results of a Phase II Trial

A novel deoxycytidine analog, gemcitabine (2',2'-difluorodeoxycytidine [dFdC]), has been studied in a phase I clinical and pharmacology trial. Doses ranging from 10 to 1,000 mg/m2 were administered over 30 minutes weekly times 3 weeks every 4 weeks. The maximum-tolerated dose (MTD) was 790 mg/m2. The dose-limiting toxicity was myelosuppression, with thrombocytopenia and anemia quantitatively more important than granulocytopenia. Nonhematologic toxicity was minimal. Two responses in patients with adenocarcinomas of the colon and lung were documented. The maximum dFdC plasma concentration, reached after 15 minutes of infusion, was proportional to the total dose administered. Elimination, due mainly to deamination, was rapid (terminal half-life [t1/2], 8.0 minutes) and dose independent. The deamination product 2',2'-difluorodeoxyuridine (dFdU) was eliminated with biphasic kinetics characterized by a long terminal phase (t1/2, 14 hours); it was the sole metabolite detected in urine. The concentration of dFdC 5'-triphosphate in circulating mononuclear cells increased in proportion to the dFdC dose at infusions between 35 and 250 mg/m2. No further increment in dFdC 5'-triphosphate (dFdCTP) was observed at higher doses, which resulted in plasma dFdC concentrations greater than 20 mumol/L (350 to 1,000 mg/m2), suggesting saturation of dFdC 5'-phosphate accumulation. The recommended dose for phase II clinical trials in solid tumors is 790 mg/m2/wk.

A phase I clinical, plasma, and cellular pharmacology study of gemcitabine.

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A phase I clinical, plasma, and cellular pharmacology study of gemcitabine.