Phase I and pharmacokinetic study of temozolomide on a daily-for-5-days schedule in patients with advanced solid malignancies.
OBJECTIVE
To determine the principal toxicities, characterize the pharmacokinetics (PKs) and pharmacodynamics (PDs) of temozolomide (TMZ) on a daily-for-5-days schedule, and recommend a dose for subsequent disease-directed studies in both minimally pretreated (MP) and heavily pretreated (HP) patients.


METHODS
Patients received TMZ as a single oral dose daily for 5 consecutive days every 28 days. TMZ doses were escalated from 100 to 150, and 150 to 200 mg/m(2)/d in separate cohorts of MP and HP patients. PK plasma was sampled on days 1 and 5. TMZ concentrations were analyzed and pertinent PK parameters were related to the principal toxicities of TMZ in PD analyses.


RESULTS
Twenty-four patients were treated with 85 courses of TMZ. Thrombocytopenia and neutropenia were the principal dose-limiting toxicities (DLTs) of TMZ on this schedule. The cumulative rate of severe myelosuppressive effects was unacceptably high at TMZ doses exceeding 150 mg/m(2)/d in both MP and HP patients. TMZ was absorbed rapidly with maximum concentrations achieved in 0.90 hours, on average, and elimination was rapid, with a half-life and systemic clearance rate (Cl(S/F)) averaging 1.8 hours and 115 mL/min/m(2), respectively. When clearance was normalized to body-surface area (BSA), interpatient variability in Cl(S/F) was reduced from 20% to 13% on day 1 and from 16% to 10% on day 5. Patients who experienced DLT had significantly higher maximum drug concentration( )(median 16 v 9.5 microg/mL, P =. 0084) and area under the concentration-time curve (median 36 v 23 microg-h/mL, P =.0019) values on day 5.


CONCLUSIONS
Prior myelosuppressive therapy was not a determinant of toxicity. TMZ 150 mg/m(2)/d administered as a single oral dose daily for 5 days every 4 weeks is well tolerated by MP and HP patients, with higher doses resulting in unacceptably high rates of severe hematologic toxicity. TMZ doses should be individualized according to BSA rather than use of a prespecified oral dose for all individuals. TMZ is an optimal agent to develop in combination with other cytotoxic, biologic, and targeted therapeutics for patients with relevant malignancies.
Hammond
L A
LA
Institute for Drug Development, Cancer Therapy and Research Center, San Antonio, TX 78829, USA. lhammond@saci.org
Eckardt
J R
JR
Baker
S D
SD
Eckhardt
S G
SG
Dugan
M
M
Forral
K
K
Reidenberg
P
P
Statkevich
P
P
Weiss
G R
GR
Rinaldi
D A
DA
Von Hoff
D D
DD
Rowinsky
E K
EK
D000284:Administration, Oral; D000328:Adult; D000368:Aged; D018906:Antineoplastic Agents, Alkylating / Q000008:administration & dosage* / Q000009:adverse effects* / Q000493:pharmacokinetics; D019540:Area Under Curve; D003606:Dacarbazine / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D005260:Female; D006207:Half-Life; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D009369:Neoplasms / Q000188:drug therapy* / Q000473:pathology; D009503:Neutropenia / Q000139:chemically induced*; D000077204:Temozolomide
D018906:Antineoplastic Agents, Alkylating; D003606:Dacarbazine; D000077204:Temozolomide