Phase I dose-finding and pharmacokinetic trial of irinotecan (CPT-11) administered every two weeks.
OBJECTIVE
This trial was performed to determine the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), and pharmacokinetic profile of irinotecan (CPT-11) when administered on a once-every-2-week schedule.


METHODS
CPT-11 was administered to successive cohorts of patients at progressively increasing starting doses ranging from 125 to 350 mg/m2. The MTD and DLTs were determined both for CPT-11 alone and for CPT-11 followed by filgrastim (G-CSF). Plasma samples were obtained during the first 24 hours after initial dosing to determine the total concentrations (lactone + carboxylate forms) of CPT-11; of the active metabolite SN-38; and of SN-38 glucuronide (SN-38G).


RESULTS
Neutropenic fever was the DLT for CPT-11 at the 300 mg/m2 dose level. When G-CSF was added, dose escalation beyond 350 mg/m2 could not be achieved due to grade 2-3 toxicities that prevented on-time retreatment with CPT-11. Severe, late diarrhea was uncommon on this schedule. Peak plasma concentrations of SN-38 and SN-38G were approximately 2.5% and 4.2% of the corresponding peak plasma concentration for CPT-II, respectively The harmonic mean terminal half-lives for CPT-11, SN-38, and SN-38G were 7.1 hours, 13.4 hours, and 12.7 hours, respectively. No predictive correlation was observed between CPT-11 or SN-38 peak concentration or AUC and first-cycle diarrhea, neutropenia, nausea, or vomiting. Across the range of doses studied, mean CPT-11 clearance was 14.0 +/- 4.0 l/h/m2 and volume of distribution was 146 +/- 45.9 l/m2.


CONCLUSIONS
When administered every two weeks, the recommended phase II starting dose of CPT-11 is 250 mg/m2 when given alone and 300 mg/m2 when supported by G-CSF. This every-two-week regimen offers a tolerable and active alternative to weekly or every-three-week single-agent CPT-11 therapy.
Rothenberg
M L
ML
The University of Texas Health Science Center San Antonio, USA. mace.rothenberg@mcmail.vanderbilt.edu
Kuhn
J G
JG
Schaaf
L J
LJ
Rodriguez
G I
GI
Eckhardt
S G
SG
Villalona-Calero
M A
MA
Rinaldi
D A
DA
Hammond
L A
LA
Hodges
S
S
Sharma
A
A
Elfring
G L
GL
Petit
R G
RG
Locker
P K
PK
Miller
L L
LL
von Hoff
D D
DD
D000328:Adult; D000368:Aged; D000972:Antineoplastic Agents, Phytogenic / Q000008:administration & dosage / Q000493:pharmacokinetics*; D002166:Camptothecin / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D016179:Granulocyte Colony-Stimulating Factor / Q000008:administration & dosage; D006801:Humans; D000077146:Irinotecan; D008297:Male; D020714:Maximum Tolerated Dose; D008875:Middle Aged; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism*
D000972:Antineoplastic Agents, Phytogenic; D016179:Granulocyte Colony-Stimulating Factor; D000077146:Irinotecan; D002166:Camptothecin