Temozolomide: The effect of once- and twice-a-day dosing on tumor tissue levels of the DNA repair protein O6-alkylguanine-DNA-alkyltransferase

T. P. Spiro, L. Liu, S. Majka, J. Haaga, J. K V Willson, S. L. Gerson

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

Temozolomide (TMZ) is a methylating agent of the imidotetrazine class, whose cytotoxic product is O6methylguanine DNA adducts, which initiate a futile recycling of the mismatch repair pathway causing DNA strand breaks and apoptotic cell death in mismatch repair proficient cells. The DNA repair protein O6-alkylguanine DNA alkyltransferase (AGT) repairs these adducts in a suicide manner and reduces the cytotoxic action of TMZ. An antitumor threshold is reached when sufficient adducts are formed by TMZ to inactivate AGT. In this study, we evaluated the relation between TMZ dosing and AGT depletion in patients with deep visceral tumors and in peripheral blood mononuclear cells (PBMCs) to determine whether the dose of TMZ was sufficient to inactivate AGT and lead to therapeutic efficacy. To do so, we compared single dose therapy with a novel twice daily regimen in a laboratory correlate-driven Phase I dose escalation study, p.o. bolus dose TMZ 200 mg/m2 daily times five was compared with the same bolus on day 1 followed by nine doses at 12-h intervals of 50, 75, 90, or 100 mg/m2. Dose-limiting toxicity in the bid regimen (grade IV thrombocytopenia and neutropenia) was seen at 100 mg/m2, cumulative dose 1100 mg/m2, and the maximum tolerated dose was 1010 mg/m2. The degree of tumor tissue AGT activity depletion measured in biopsies before and on day 5 of therapy varied widely, between 0 (in 3 patients) and 99% (in 1), with the majority of patients (10 of 15) having 52-84% tumor AGT depletion. In contrast, AGT activity in PBMCs fell rapidly during TMZ administration to undetectable levels in all dosage groups on day 5 but did not correlate with tumor AGT depletion. TMZ pharmacokinetics were dose proportional; no accumulation occurred >5-day period in the bid regimen. Two partial responses were seen, lasting 3 and 4 months. Five additional patients achieved prolonged stabilization of disease for 4-6 monthly cycles. This is the first study to document that at maximum tolerated doses, TMZ depletes PBMC AGT but only partially and variably depletes visceral tumor AGT in most patients, even during twice daily dosing. Drug combinations or schedules designed to maximally deplete tumor AGT might improve TMZ efficacy.

Original languageEnglish (US)
Pages (from-to)2309-2317
Number of pages9
JournalClinical Cancer Research
Volume7
Issue number8
StatePublished - 2001

Fingerprint

temozolomide
DNA Repair
Neoplasms
Proteins
Blood Cells
DNA Mismatch Repair
Maximum Tolerated Dose
DNA alkyltransferase
DNA Breaks
DNA Adducts

ASJC Scopus subject areas

  • Cancer Research
  • Oncology

Cite this

Temozolomide : The effect of once- and twice-a-day dosing on tumor tissue levels of the DNA repair protein O6-alkylguanine-DNA-alkyltransferase. / Spiro, T. P.; Liu, L.; Majka, S.; Haaga, J.; Willson, J. K V; Gerson, S. L.

In: Clinical Cancer Research, Vol. 7, No. 8, 2001, p. 2309-2317.

Research output: Contribution to journalArticle

Spiro, T. P. ; Liu, L. ; Majka, S. ; Haaga, J. ; Willson, J. K V ; Gerson, S. L. / Temozolomide : The effect of once- and twice-a-day dosing on tumor tissue levels of the DNA repair protein O6-alkylguanine-DNA-alkyltransferase. In: Clinical Cancer Research. 2001 ; Vol. 7, No. 8. pp. 2309-2317.
@article{20591369054747fbaad0d340e30d0a5c,
title = "Temozolomide: The effect of once- and twice-a-day dosing on tumor tissue levels of the DNA repair protein O6-alkylguanine-DNA-alkyltransferase",
abstract = "Temozolomide (TMZ) is a methylating agent of the imidotetrazine class, whose cytotoxic product is O6methylguanine DNA adducts, which initiate a futile recycling of the mismatch repair pathway causing DNA strand breaks and apoptotic cell death in mismatch repair proficient cells. The DNA repair protein O6-alkylguanine DNA alkyltransferase (AGT) repairs these adducts in a suicide manner and reduces the cytotoxic action of TMZ. An antitumor threshold is reached when sufficient adducts are formed by TMZ to inactivate AGT. In this study, we evaluated the relation between TMZ dosing and AGT depletion in patients with deep visceral tumors and in peripheral blood mononuclear cells (PBMCs) to determine whether the dose of TMZ was sufficient to inactivate AGT and lead to therapeutic efficacy. To do so, we compared single dose therapy with a novel twice daily regimen in a laboratory correlate-driven Phase I dose escalation study, p.o. bolus dose TMZ 200 mg/m2 daily times five was compared with the same bolus on day 1 followed by nine doses at 12-h intervals of 50, 75, 90, or 100 mg/m2. Dose-limiting toxicity in the bid regimen (grade IV thrombocytopenia and neutropenia) was seen at 100 mg/m2, cumulative dose 1100 mg/m2, and the maximum tolerated dose was 1010 mg/m2. The degree of tumor tissue AGT activity depletion measured in biopsies before and on day 5 of therapy varied widely, between 0 (in 3 patients) and 99{\%} (in 1), with the majority of patients (10 of 15) having 52-84{\%} tumor AGT depletion. In contrast, AGT activity in PBMCs fell rapidly during TMZ administration to undetectable levels in all dosage groups on day 5 but did not correlate with tumor AGT depletion. TMZ pharmacokinetics were dose proportional; no accumulation occurred >5-day period in the bid regimen. Two partial responses were seen, lasting 3 and 4 months. Five additional patients achieved prolonged stabilization of disease for 4-6 monthly cycles. This is the first study to document that at maximum tolerated doses, TMZ depletes PBMC AGT but only partially and variably depletes visceral tumor AGT in most patients, even during twice daily dosing. Drug combinations or schedules designed to maximally deplete tumor AGT might improve TMZ efficacy.",
author = "Spiro, {T. P.} and L. Liu and S. Majka and J. Haaga and Willson, {J. K V} and Gerson, {S. L.}",
year = "2001",
language = "English (US)",
volume = "7",
pages = "2309--2317",
journal = "Clinical Cancer Research",
issn = "1078-0432",
publisher = "American Association for Cancer Research Inc.",
number = "8",

}

TY - JOUR

T1 - Temozolomide

T2 - The effect of once- and twice-a-day dosing on tumor tissue levels of the DNA repair protein O6-alkylguanine-DNA-alkyltransferase

AU - Spiro, T. P.

AU - Liu, L.

AU - Majka, S.

AU - Haaga, J.

AU - Willson, J. K V

AU - Gerson, S. L.

PY - 2001

Y1 - 2001

N2 - Temozolomide (TMZ) is a methylating agent of the imidotetrazine class, whose cytotoxic product is O6methylguanine DNA adducts, which initiate a futile recycling of the mismatch repair pathway causing DNA strand breaks and apoptotic cell death in mismatch repair proficient cells. The DNA repair protein O6-alkylguanine DNA alkyltransferase (AGT) repairs these adducts in a suicide manner and reduces the cytotoxic action of TMZ. An antitumor threshold is reached when sufficient adducts are formed by TMZ to inactivate AGT. In this study, we evaluated the relation between TMZ dosing and AGT depletion in patients with deep visceral tumors and in peripheral blood mononuclear cells (PBMCs) to determine whether the dose of TMZ was sufficient to inactivate AGT and lead to therapeutic efficacy. To do so, we compared single dose therapy with a novel twice daily regimen in a laboratory correlate-driven Phase I dose escalation study, p.o. bolus dose TMZ 200 mg/m2 daily times five was compared with the same bolus on day 1 followed by nine doses at 12-h intervals of 50, 75, 90, or 100 mg/m2. Dose-limiting toxicity in the bid regimen (grade IV thrombocytopenia and neutropenia) was seen at 100 mg/m2, cumulative dose 1100 mg/m2, and the maximum tolerated dose was 1010 mg/m2. The degree of tumor tissue AGT activity depletion measured in biopsies before and on day 5 of therapy varied widely, between 0 (in 3 patients) and 99% (in 1), with the majority of patients (10 of 15) having 52-84% tumor AGT depletion. In contrast, AGT activity in PBMCs fell rapidly during TMZ administration to undetectable levels in all dosage groups on day 5 but did not correlate with tumor AGT depletion. TMZ pharmacokinetics were dose proportional; no accumulation occurred >5-day period in the bid regimen. Two partial responses were seen, lasting 3 and 4 months. Five additional patients achieved prolonged stabilization of disease for 4-6 monthly cycles. This is the first study to document that at maximum tolerated doses, TMZ depletes PBMC AGT but only partially and variably depletes visceral tumor AGT in most patients, even during twice daily dosing. Drug combinations or schedules designed to maximally deplete tumor AGT might improve TMZ efficacy.

AB - Temozolomide (TMZ) is a methylating agent of the imidotetrazine class, whose cytotoxic product is O6methylguanine DNA adducts, which initiate a futile recycling of the mismatch repair pathway causing DNA strand breaks and apoptotic cell death in mismatch repair proficient cells. The DNA repair protein O6-alkylguanine DNA alkyltransferase (AGT) repairs these adducts in a suicide manner and reduces the cytotoxic action of TMZ. An antitumor threshold is reached when sufficient adducts are formed by TMZ to inactivate AGT. In this study, we evaluated the relation between TMZ dosing and AGT depletion in patients with deep visceral tumors and in peripheral blood mononuclear cells (PBMCs) to determine whether the dose of TMZ was sufficient to inactivate AGT and lead to therapeutic efficacy. To do so, we compared single dose therapy with a novel twice daily regimen in a laboratory correlate-driven Phase I dose escalation study, p.o. bolus dose TMZ 200 mg/m2 daily times five was compared with the same bolus on day 1 followed by nine doses at 12-h intervals of 50, 75, 90, or 100 mg/m2. Dose-limiting toxicity in the bid regimen (grade IV thrombocytopenia and neutropenia) was seen at 100 mg/m2, cumulative dose 1100 mg/m2, and the maximum tolerated dose was 1010 mg/m2. The degree of tumor tissue AGT activity depletion measured in biopsies before and on day 5 of therapy varied widely, between 0 (in 3 patients) and 99% (in 1), with the majority of patients (10 of 15) having 52-84% tumor AGT depletion. In contrast, AGT activity in PBMCs fell rapidly during TMZ administration to undetectable levels in all dosage groups on day 5 but did not correlate with tumor AGT depletion. TMZ pharmacokinetics were dose proportional; no accumulation occurred >5-day period in the bid regimen. Two partial responses were seen, lasting 3 and 4 months. Five additional patients achieved prolonged stabilization of disease for 4-6 monthly cycles. This is the first study to document that at maximum tolerated doses, TMZ depletes PBMC AGT but only partially and variably depletes visceral tumor AGT in most patients, even during twice daily dosing. Drug combinations or schedules designed to maximally deplete tumor AGT might improve TMZ efficacy.

UR - http://www.scopus.com/inward/record.url?scp=0034886714&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0034886714&partnerID=8YFLogxK

M3 - Article

C2 - 11489806

AN - SCOPUS:0034886714

VL - 7

SP - 2309

EP - 2317

JO - Clinical Cancer Research

JF - Clinical Cancer Research

SN - 1078-0432

IS - 8

ER -