A phase II study of gemcitabine and 5-fluorouracil in metastatic pancreatic cancer: an Eastern Cooperative Oncology Group Study (E3296)

Toward a rational design of peptide inhibitors of ribonucleotide reductase: structure-function and modeling studies

Mammalian ribonucleotide reductase, a chemotherapeutic target, has two subunits, mR1 and mR2, and is inhibited by AcF(1)TLDADF(7), denoted P7. P7 corresponds to the C-terminus of mR2 and competes with mR2 for binding to mR1. We report results of a structure-function analysis of P7, obtained using a new assay measuring peptide ligand binding to mR1, that demonstrate stringent specificity for Phe at F(7), high specificity for Phe at F(1), and little specificity for the N-acyl group. They support a structural model in which the dominant interactions of P7 occur at two mR1 sites, the F(1) and F(7) subsites. The model is constructed from the structure of Escherichia coli R1 (eR1) complexed with the C-terminal peptide from eR2, aligned sequences of mR1 and eR1, and the trNOE-derived structure of mR1-bound P7. Comparison of this model with similar models constructed for mR1 complexed with other inhibitory ligands indicates that increased F(1) subsite interaction can offset lower F(7) subsite interaction and suggests strategies for the design of new, higher affinity inhibitors.

The role of gemcitabine alone and in combination in the treatment of pancreatic cancer

Pancreatic cancer, one of the most frequently reported gastrointestinal tumors, has a 5-year survival of less than 5%. Despite representing only 2-3% of the total cancer incidence, it is the fifth leading cause of cancer death. This is because it is commonly only diagnosed at an advanced stage. Until recently the traditional therapy for patients with advanced disease was palliative 5-fluorouracil (5-FU)-based chemotherapy. However, the novel antinucleoside gemcitabine (Gemzar) has demonstrated a survival benefit over 5-FU, and an improvement in disease-related symptoms and quality of life in patients with advanced disease. This review presents an overview of the clinical studies of gemcitabine, either alone or in combination, with other chemotherapeutic agents and/or radiation therapy, in the treatment of these patients. A comparison of these studies is made with those using alternative treatment regimens. The data suggest that gemcitabine in combination with biomodulated 5-FU should be considered the standard palliative treatment to which other new drug combinations or combined modality chemoradiation regimens should be compared.

A combination of a fixed dose rate infusion of gemcitabine associated to a bolus 5-fluorouracil in advanced pancreatic cancer, a report from the Italian Group for the Study of Digestive Tract Cancer (GISCAD)

BACKGROUND

Laboratory evidences suggest the possibility that an infusion rate of 10 mg/m2/min may be more effective than the standard 30-min infusion of Gemcitabine (GEM).

PATIENTS AND METHODS

Thirty-four patients with histologically verified locally unresectable and/or metastatic pancreatic carcinoma received GEM at the dose of 1,500 mg/m2 with an infusion rate of 10 mg/m2/min, associated to 5-fluorouracil (5-FU) at the dose of 600 mg/m2. Both drugs were administered weekly for two consecutive weeks out of every three weeks.

RESULTS

One complete and five partial responses have been observed for an overall response rate of 17% (95% CI: 3%-27%). The time to progression was 3.7 months with a median survival of 5.7 months. A clinical benefit was obtained in 5 of 29 patients (17%). Grade 3-4 WHO toxicities included neutropenia (35%) and thrombocytopenia (10%).

CONCLUSION

It is unlikely that a fixed dose rate infusion of GEM, at least with this dose, can improve palliation in comparison with the standard 30-min infusion schedule in advanced pancreatic cancer.