title: Phase I study of phosphonacetyl-L-aspartate, 5-fluorouracil, and leucovorin in patients with advanced cancer.
abstract: Low-dose phosphonacetyl-L-aspartate (PALA) may potentiate both 5-fluorouracil (5-FU) incorporation into RNA and thymidylate synthase inhibition by 5-fluorodeoxyuridylate (5-FdUMP). The gastrointestinal toxicity of 5-FU is not increased by PALA administration. Exogenous leucovorin, on the other hand, which enhances thymidylate synthase inhibition, appears to increase the clinical toxicity of 5-FU in a dose-dependent manner. As a result, the clinical use of high-dose leucovorin requires a marked dose reduction of 5-FU. Extracellular leucovorin levels of 1 microM suffice to maximize the enhancement of thymidylate synthase inhibition in several models. We conducted a trial to add leucovorin to the PALA/5-FU regimen. We chose a leucovorin dose that was predicted to yield end-infusion total reduced folate concentrations of 1 microM. The major endpoint was to determine the maximum tolerated dose of 5-FU in this combination. The regimen consisted of 250 mg/m2 PALA given on day 1 and, 24 h later, escalating 5-FU doses ranging from 1,850 to 2,600 mg/m2 admixed with 50 mg/m2 leucovorin and given by 24-h infusion. Courses were repeated weekly. A total of 24 patients with a median performance status of 1 were entered at three dose levels. Diarrhea was dose-limiting; 6/13 patients had grade II or worse diarrhea at 2,600 mg/m2. Dose modification resulted in a mean dose intensity of 2,300 mg/m2 at both the 2,600- and 2,300-mg/m2 dose levels. The 2,300-mg/m2 dose is suitable for phase II testing of this regimen. Three patients (two with breast cancer and 1 with sarcoma) had a partial remission. We measured steady-state concentrations (Css) of 5-FU in 23 patients. The mean Css increased with dose from 0.738 to 1.03 micrograms/ml. Total body clearance did not vary with dose in this range. Patients with grade II or worse diarrhea had a higher mean Css (1.10 +/- 0.19) than those with grade O or I toxicity (0.835 +/- 0.25, P < 0.02). Total bioactive folates (bound and free) were measured using a biological assay. Pretreatment values ranged from 2 to 52 nM and were not predictive of toxicity. End-infusion (23-h) values were somewhat lower than predicted and ranged from 400 to 950 nM. The risk of diarrhea was positively correlated with end-infusion total folate values. In a logistic regression analysis, total folate values obtained at 23 h were a more powerful predictor of diarrhea than were 5-FU Css values.(ABSTRACT TRUNCATED AT 400 WORDS)
authors: Fox Chase Cancer Center, Philadelphia, PA 19111.
authors: A
authors: A
authors: Hageboutros
authors: A
authors: A
authors: Rogatko
authors: E M
authors: EM
authors: Newman
authors: C
authors: C
authors: McAleer
authors: J
authors: J
authors: Brennan
authors: F P
authors: FP
authors: LaCreta
authors: G R
authors: GR
authors: Hudes
authors: R F
authors: RF
authors: Ozols
authors: P J
authors: PJ
authors: O'Dwyer
mesh_terms: D000328:Adult; D000368:Aged; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000009:adverse effects / Q000627:therapeutic use*; D001224:Aspartic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives; D003967:Diarrhea / Q000139:chemically induced; D004064:Digestive System / Q000187:drug effects; D004357:Drug Synergism; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage / Q000493:pharmacokinetics; D005492:Folic Acid / Q000097:blood; D006801:Humans; D002955:Leucovorin / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000188:drug therapy*; D009503:Neutropenia / Q000139:chemically induced; D010746:Phosphonoacetic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives; D016016:Proportional Hazards Models; D011743:Pyrimidines / Q000096:biosynthesis; D012074:Remission Induction; D012307:Risk Factors; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors
chemical_list: D000964:Antimetabolites, Antineoplastic; D011743:Pyrimidines; D001224:Aspartic Acid; C013195:sparfosic acid; D005492:Folic Acid; D013940:Thymidylate Synthase; D010746:Phosphonoacetic Acid; D002955:Leucovorin; D005472:Fluorouracil