A phase I and pharmacokinetic study of a new camptothecin derivative, 9-aminocamptothecin.
Camptothecins are the only available antitumor agents which target the nuclear enzyme topoisomerase I. 9-Aminocamptothecin (9-AC) is a water-insoluble derivative of camptothecin which has demonstrated impressive antitumor activity in preclinical models. While two other water-soluble derivatives, CPT-11 and topotecan, have successfully completed Phase I and Phase II testing, biochemical and tissue culture studies suggest that camptothecin analogues differ in characteristics which may be important in determining antitumor activity. We performed a Phase I trial of 9-AC to determine the pharmacokinetics, dose-limiting toxicity, and maximum tolerated dose of this agent when administered as a 72-h continuous i.v. infusion. Thirty-one patients with resistant solid cancers received 5-60 microgram/m2/h 9-AC for 72 h, repeated at 3-week intervals. The drug was administered in a vehicle containing dimethylacetamide, polyethylene glycol, and phosphoric acid. Blood samples were collected and the lactone (closed ring) form of 9-AC was quantitated. The maximum tolerated dose of 9-AC was determined to be 45 microgram/m2/h. Dose-limiting toxicity consisted of neutropenia. Thrombocytopenia was also prominent. There were no significant nonhematological toxicities. Minimal responses were seen in patients with gastric, colon, and non-small cell lung cancer. Although significant interpatient variation in plasma 9-AC lactone levels was observed, pooled data were fit to a two-compartment model, with a terminal half-life of 36 h. Analyses of topoisomerase protein levels in peripheral blood cells indicated decreases in topoisomerase I accompanied by increases in topoisomerase II in two of three patients. 9-AC is an active antitumor agent and may be administered safely as a 72-h infusion in patients with cancer. Although Phase II trials with a 72-h infusion of 9-AC are warranted, alternate schedules should be evaluated given the dramatic preclinical activity seen with more prolonged administrations.
Rubin
E
E
Division of Cancer Pharmacology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
Wood
V
V
Bharti
A
A
Trites
D
D
Lynch
C
C
Hurwitz
S
S
Bartel
S
S
Levy
S
S
Rosowsky
A
A
Toppmeyer
D
D
D000328:Adult; D000368:Aged; D000740:Anemia / Q000139:chemically induced; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000009:adverse effects* / Q000493:pharmacokinetics*; D002166:Camptothecin / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D004264:DNA Topoisomerases, Type I / Q000097:blood; D004250:DNA Topoisomerases, Type II / Q000097:blood; D004334:Drug Administration Schedule; D005260:Female; D006207:Half-Life; D006801:Humans; D007262:Infusions, Intravenous; D007963:Leukocytes, Mononuclear / Q000201:enzymology; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D009369:Neoplasms / Q000097:blood / Q000188:drug therapy*; D009503:Neutropenia / Q000139:chemically induced; D013921:Thrombocytopenia / Q000139:chemically induced
D000970:Antineoplastic Agents; C080125:9-aminocamptothecin; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II; D002166:Camptothecin