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This phase I trial evaluated a high-dose, short-term infusion of zidovudine (AZT) following oral leucovorin (LV) and bolus 5-fluorouracil (FUra). Thirteen patients with metastatic cancer received 30 cycles of therapy. Plasma monitoring demonstrated a dose-dependent increase in peak plasma levels of AZT through the range of dose levels, from 104.3 +/- 8.7 microM at the 1.5 g/m2 dose of AZT to 1312.6 +/- 165.9 microM at the 11.0 g/m2 dose. While AZT did not potentiate the usual clinical toxicities of LV plus FUra, an unexpected finding of symptomatic hypotension during the AZT infusion was the dose-limiting toxicity in this trial. One partial response was observed in a previously untreated patient with metastatic colorectal cancer. The maximal tolerated dose of AZT, 7.0 g/m2 over 2 hr, is recommended for future phase II evaluation of this novel combination.

Background: The inhibition of pyrimidine metabolism by 5-fluorouracil (5-FU) enhances the anti-cancer effects of zidovudine (formerly called AZT) in in vitro and in vivo model systems without additive toxicity. Zidovudine-induced DNA damage correlates with cytotoxicity., Methods: A Phase I trial of high-dose continuous-infusion intravenous zidovudine therapy in combination with 5-FU and leucovorin therapy was performed. Eighteen patients with advanced malignant tumors were treated with 43 courses of oral leucovorin (50 mg every 4 hours); continuous-infusion 5-FU (800 mg/M2/day) for 72 hours (3 days); and zidovudine, begun 24 hours after the start of 5-FU and leucovorin, for 48 hours, and terminating with the end of the 5-FU infusion. Zidovudine plasma levels and zidovudine-induced DNA damage were assessed., Results: Zidovudine administered in doses of 2-20 g/M2/day, added no obvious toxicity to the basic chemotherapeutic treatment with 5-FU and leucovorin but resulted in a dose-dependent biologic effect manifested by an increase in DNA strand breaks in peripheral blood cells. At doses greater than 15 g/M2/day, altered plasma kinetics of zidovudine were observed; plasma zidovudine levels increased dramatically in relation to the dose of zidovudine. Limitations in drug administration restricted administration of higher intravenous doses without achieving a maximally tolerated dose. No responses were seen in this heavily pretreated population., Conclusions: Based on the results of preclinical studies, plasma zidovudine levels greater than those achieved at the maximal dose (133 microns) are required for increased anti-cancer activity with 5-FU. Additional studies using a bolus or rapid infusion as a method of achieving higher peak levels are indicated.

A phase I clinical, pharmacologic, and biochemical evaluation of escalating oral zidovudine (AZT) given over 2 days with a fixed dose of continuous-infusion fluorouracil (800 mg/m2 per day X 3 days) and oral leucovorin calcium was performed. Eighteen patients were treated with doses of AZT ranging from 1.0 to 9.0 g/m2 per day. Nausea and vomiting were dose limiting, with a maximally tolerated dose of 7.5 g/m2 per day. Rash and mucositis occurred but were not dose limiting. A dose-related increase in peak plasma levels of AZT was observed, and the alpha half-life of AZT in plasma (75 min) was unaffected by these high doses. At doses above 4.0 g/m2 per day, trough levels significantly increased, perhaps reflecting prolonged absorption from the gut. No responses were observed; however, a significant increase in DNA single-strand breaks was observed in peripheral blood cells after a threshold dose of 4.0 g/m2 per day, confirming a biological effect of AZT in this regimen. Further trials with an intravenous formulation capable of maintaining plasma levels and circumventing dose-limiting toxicity are warranted.

Lymphocytes from control donors and from cancer patients have been tested for antitumor, cell-mediated immunity against various melanoma and breast cancer target cell cultures with a microcytotoxicity assay. Control lymphocytes inhibited growth of target cells with high frequency, particularly with cell line, as opposed to short-term, cultures. Inhibition was not found for all target cells tested at a given time with a single preparation of lymphocytes. Sequential studies over a 2-year period with lymphocytes from the same control donors showed fluctuations of inhibition against the same target cells. With serial passage, the target cells also changed in their susceptibility to destruction by control lymphocytes. Lymphocytes from melanoma patients were more inhibitory than control lymphocytes for one melanoma target cell culture but not for two other melanoma cultures. Significant inhibition by lymphocytes from melanoma patients was not seen against two cultures derived from breast cancer patients. Lymphocytes from breast cancer patients were more inhibitory than control lymphocytes for 4 of 5 breast cancer cultures and they did not inhibit two melanoma cultures. Significantly specific inhibition was seen with short-term, but not cell line, breast cultures. The over-all data show specificity for target cells of the appropriate histological type. However, the high and inconstant reactivity of control lymphocytes in this assay suggests that nonspecific inhibition of tumor target cells by patient lymphocytes is found in many experiments. It is concluded that the microcytotoxicity assay is not suitable for clinical studies, since sequential data obtained in individual patients are difficult to interpret.

Clinical, pharmacologic, and immunologic effects of 2'-deoxycoformycin (dCF) were evaluated in 15 patients with advanced malignancies. Toxicity was less severe with a low dose (4 mg/m2) of dCF, but this dose still resulted in suppression of cellular adenosine deaminase activity, skin test reactivity, and lymphocyte responses to mitogens. Improvement in cutaneous T cell lymphoma plaques was seen after dCF. Further investigations of antitumor efficacy with the use of this low dosage schedule should continue in patients with hematologic neoplasms, and additional preliminary studies of the combination of an adenosine deaminase inhibitor with an adenosine analog should also be considered.

Treatment with continuous infusions of cisplatin results in increased filterable drug exposures as measured by the area under the curve (AUC) of nonprotein-bound plasma platinum levels. To determine the dose-limiting toxicity and optimal method of administration, 24 patients were treated with continuous infusions of cisplatin at a dose rate of 25 mg/M2/day in a limited Phase I trial. A total of 47 courses were given. Nine patients received 13 courses of 4 days duration, 19 received 29 courses of 5 days duration, and five received courses of 6 or 7 days duration. Dose-limiting toxicity was found to be leukopenia: 42% of patients receiving the 5-day treatment developed a nadir count of less than 3000 cells/mm3. Nausea and vomiting were easily controlled. Minimal nephrotoxicity occurred in five patients and was associated with daily volume expansion with 2 l of 0.9% NaCl solution in four patients. All other patients were given 3 l of daily volume expansion during treatment. Responses were seen in 6 of 22 evaluable patients (27%). It is concluded that continuous infusion cisplatin at a dose rate of 25 mg/M2/day can be given safely for 5 days as a single agent if concomitant volume expansion with at least 3 l of 0.9% NaCl solution is given daily. Phase III comparative trials with a conventional bolus and newer high-dose regimens for response and toxicity are indicated.

A phase I trial was conducted in 30 patients with solid tumors, using infusions of 5-fluorodeoxyuridine (5-FUdR) plus cytosine arabinoside (ara-C). Doses of 5-FUdR administered over 2 hours daily X 5 ranged from 0.02 to 1.0 mg/kg, and these doses immediately preceded a 1-hour infusion of ara-C. These schedules were selected because 5-FUdR pretreatment had been shown to sensitize L5178Y cells in culture to acute cell death by ara-C. Dose-limiting toxicity was myelosuppression. Based upon results in this study, the recommended dose of 5-FUdR to be used in phase II trials of this combination is 0.04--0.05 mg/kg (1.6--2.0 mg/m2) given prior to ara-C at a dose of 100 mg/m2. Antitumor responses were seen in patients with head and neck cancer, breast carcinoma, and carcinoid syndrome.