Andrew Goetz

Marked inactivation of O6-alkylguanine-DNA alkyltransferase activity with protracted temozolomide schedules

Temozolomide, an oral DNA methylator that inactivates the DNA repair enzyme O6-alkylguanine-DNA alkyltransferase (AGAT), has demonstrated anticancer activity on protracted schedules. Protracted schedules may lead to an ‘autoenhancement’ of temozolomides inherent cytotoxic potential by cumulative reduction of the cells capacity for AGAT-mediated DNA repair and resistance. This study was undertaken to characterise AGAT inactivation and regeneration in the peripheral blood mononuclear cells (PBMCs) of patients treated on two protracted temozolomide schedules. O6-alkyl guanine-DNA alkyltransferase activity was measured in the PBMCs of patients treated on two phase I protracted temozolomide studies. Patients were treated daily for either 7 days every 2 weeks (Schedule A) or 21 days every 4 weeks (Schedule B). The effects of various temozolomide doses (75–175 mg m−2), treatment duration (7–21 days), and temozolomide plasma levels on AGAT inactivation and regeneration, as well as the relation between AGAT inactivation and toxicity, were studied. O6-alkyl guanine-DNA alkyltransferase activity in PBMCs was measured serially in 52 patients. Marked inactivation of AGAT occurred following 7 days of temozolomide treatment, with mean AGAT activity decreasing by 72% (P<0.0001). Similarly, mean AGAT activity decreased by 63 and 73% after 14 and 21 days of treatment, respectively (P<0.001 for both comparisons). O6-alkyl guanine-DNA alkyltransferase inactivation was greater after 7 days of treatment with higher doses of temozolomide than lower doses and remained markedly reduced 7 days post-treatment. However, AGAT inactivation following temozolomide treatment for 14 and 21 days was similar at all doses. On the continuous 21-day schedule, AGAT inactivation was significantly greater in patients who experienced severe thrombocytopenia than those who did not (90.3±5.5 vs 72.5±16.1%, P<0.045). In Conclusion, protracted administration of temozolomide, even at relatively low daily doses, leads to significant and prolonged depletion of AGAT activity, which may enhance the antitumour activity of the agent.

Phase I and Pharmacokinetic Study of XRP6258 (RPR 116258A), a Novel Taxane, Administered as a 1-Hour Infusion Every 3 Weeks in Patients with Advanced Solid Tumors

Purpose: To assess the feasibility of administering XRP6258, a new taxane with a low affinity for the multidrug resistance 1 protein, as a 1-hour i.v. infusion every 3 weeks. The study also sought to determine the maximum tolerated dose and the recommended dose, to describe the pharmacokinetic (PK) behavior of the compound, and to seek preliminary evidence of anticancer activity. Experimental Design: Twenty-five patients with advanced solid malignancies were treated with 102 courses of XRP6258 at four dose levels ranging from 10 to 25 mg/m2. Dose escalation was based on the occurrence of dose-limiting toxicity (DLT) at each dose level, provided that PK variables were favorable. The maximum tolerated dose was defined as the dose at which at least two patients developed a DLT at the first course. Results: Neutropenia was the principal DLT, with one patient experiencing febrile neutropenia and two others showing prolonged grade 4 neutropenia at the 25 mg/m2 dose level. Nonhematologic toxicities, including nausea, vomiting, diarrhea, neurotoxicity, and fatigue, were generally mild to moderate in severity. XRP6258 exhibited dose-proportional PK, a triphasic elimination profile, a long terminal half-life (77.3 hours), a high clearance (mean CL, 53.5 L/h), and a large volume of distribution (mean Vss, 2,034 L/m2). Objective antitumor activity included partial responses in two patients with metastatic prostate carcinoma, one unconfirmed partial response, and two minor responses. Conclusion: The recommended phase II dose of XRP6258 on this schedule is 20 mg/m2. The general tolerability and encouraging antitumor activity in taxane-refractory patients warrant further evaluations of XRP6258.

A Phase I and Pharmacokinetic Study of Pegylated Camptothecin as a 1-Hour Infusion Every 3 Weeks in Patients With Advanced Solid Malignancies

PURPOSE To assess the feasibility of administering camptothecin (CPT), the prototypic topoisomerase I inhibitor, as polyethylene glycol (PEG)-CPT, a macromolecule consisting of CPT conjugated to chemically modified PEG. The study also sought to determine the maximum-tolerated dose (MTD) of PEG-CPT, characterize its pharmacokinetic behavior, and seek preliminary evidence of anticancer activity. PATIENTS AND METHODS Patients with advanced solid malignancies were treated with escalating doses of PEG-CPT as a 1-hour intravenous (IV) infusion every 3 weeks. A modified continual reassessment method was used for dose-level assignment to determine the MTD, which was defined as the highest dose level at which the incidence of dose-limiting toxicity did not exceed 20%. RESULTS Thirty-seven patients were treated with 144 courses of PEG-CPT at seven dose levels ranging from 600 to 8,750 mg/m(2). Severe myelosuppression was consistently experienced by heavily pretreated (HP) and minimally pretreated (MP) patients at the highest dose level evaluated, 8,750 mg/m(2), whereas both HP and MP patients tolerated repetitive treatment at 7,000 mg/m(2). Cystitis, nausea, vomiting, and diarrhea were also observed but were rarely severe. A partial response was noted in a patient with platinum- and etoposide-resistant small-cell lung carcinoma, and minor responses were noted in one patient each with adenocarcinoma of unknown primary type and osteosarcoma. The pharmacokinetics of free CPT were dose proportional. Free CPT accumulated slowly in plasma, with maximal plasma concentrations achieved at 23 +/- 12.3 hours; the harmonic mean half-life (t(1/2)) of free CPT was long (t(1/2), 77.46 +/- 36.77 hours). CONCLUSION Clinically relevant doses of CPT can be delivered by administering PEG-CPT. The recommended dose for phase II studies in both MP and HP patients is 7,000 mg/m(2) as 1-hour IV every 3 weeks. The characteristics of the myelosuppressive effects of PEG-CPT, the paucity of severe nonhematologic toxicities with repetitive treatment, the preliminary antitumor activity noted, and the slow clearance of CPT enabling simulation of desirable pharmacokinetic parameters with a convenient single-dosing regimen warrant further disease-directed evaluations.

Dose-Escalating and Pharmacological Study of Oxaliplatin in Adult Cancer Patients With Impaired Renal Function: A National Cancer Institute Organ Dysfunction Working Group Study

PURPOSE This study was undertaken to determine the toxicities, pharmacokinetics, and maximum tolerated doses of oxaliplatin in patients with renal impairment and to develop formal guidelines for oxaliplatin dosing in this patient population. PATIENTS AND METHODS Thirty-seven adult cancer patients with variable renal function received intravenous oxaliplatin at 60 to 130 mg/m2 every 3 weeks. Patients were stratified by 24-hour creatinine clearance (CrCL) into four cohorts: group A (controls, CrCL > or =60 mL/min), group B (mild dysfunction, CrCL 40 to 59 mL/min), group C (moderate dysfunction, CrCL 20 to 39 mL/min), and group D (severe dysfunction, CrCL <20 mL/min). Doses were escalated in cohorts of three patients, and urine and plasma ultrafiltrates were assayed for platinum concentrations. RESULTS No dose-limiting toxicities were observed in any patient group during the first cycle of therapy. Escalation of oxaliplatin to the maximum dose of 130 mg/m2 was well tolerated in all patient groups with a CrCL > or =20 mL/min (groups A, B, and C). Pharmacokinetic analysis showed that patients with decreased CrCL had a corresponding decrease in the clearance of plasma ultrafiltrable platinum (r2 = 0.765). However, oxaliplatin-induced side effects were not more common or severe in patients with mild to moderate renal dysfunction, despite the decrease in ultrafiltrable platinum clearance. CONCLUSION Oxaliplatin at 130 mg/m2 every 3 weeks is well tolerated by patients with mild to moderate degrees of renal dysfunction. These data strongly support the recommendation that dose reductions of single-agent oxaliplatin are not necessary in patients with a CrCL greater than 20 mL/min.

Phase I and Pharmacokinetic Study of Pemetrexed Administered Every 3 Weeks to Advanced Cancer Patients With Normal and Impaired Renal Function

PURPOSE This phase I study was conducted to determine the toxicities, pharmacokinetics, and recommended doses of pemetrexed in cancer patients with normal and impaired renal function. PATIENTS AND METHODS Patients received a 10-minute infusion of 150 to 600 mg/m2 of pemetrexed every 3 weeks. Patients were stratified for independent dose escalation by measured glomerular filtration rate (GFR) into four cohorts ranging from > or = 80 to less than 20 mL/min. Pemetrexed plasma and urine pharmacokinetics were evaluated for the first cycle. Patients enrolled after December 1999 were supplemented with oral folic acid and intramuscular vitamin B12. RESULTS Forty-seven patients were treated with 167 cycles of pemetrexed. Hematologic dose-limiting toxicities occurred in vitamin-supplemented patients (two; 15%) and non-supplemented patients (six; 18%), and included febrile neutropenia (four patients) and grade 4 thrombocytopenia (two patients). Nonhematologic toxicities included fatigue, diarrhea, and nausea, and did not correlate with renal function. Accrual was discontinued in patients with GFR less than 30 mL/min after one patient with a GFR of 19 mL/min died as a result of treatment-related toxicities. Pemetrexed plasma clearance positively correlated with GFR (r2 = 0.736), resulting in increased drug exposures in patients with impaired renal function. With vitamin supplementation, pemetrexed 600 mg/m2 was tolerated by patients with a GFR > or = 80 mL/min, whereas patients with a GFR of 40 to 79 mL/min tolerated a dose of 500 mg/m2. CONCLUSION Pemetrexed was well tolerated at doses of 500 mg/m2 with vitamin supplementation in patients with GFR > or = 40 mL/min. Additional studies are needed to define appropriate dosing for renally impaired patients receiving higher dose pemetrexed with vitamin supplementation.

Oxaliplatin Pharmacokinetics and Pharmacodynamics in Adult Cancer Patients with Impaired Renal Function

Purpose: To characterize the pharmacokinetics and pharmacodynamics of oxaliplatin in cancer patients with impaired renal function. Experimental Design: Thirty-four patients were stratified by 24-h urinary creatinine clearance (CrCL) into four renal dysfunction groups: group A (control, CrCL, ≥60 mL/min), B (mild, CrCL, 40-59 mL/min), C (moderate, CrCL, 20-39 mL/min), and D (severe, CrCL, <20 mL/min). Patients were treated with 60 to 130 mg/m2 oxaliplatin infused over 2 h every 3 weeks. Pharmacokinetic monitoring of platinum in plasma, plasma ultrafiltrates, and urine was done during cycles 1 and 2. Results: Plasma ultrafiltrate platinum clearance strongly correlated with CrCL (r2 = 0.712). Platinum elimination from plasma was triphasic, and maximal platinum concentrations (Cmax) were consistent across all renal impairment groups. However, only the β-half-life was significantly prolonged by renal impairment, with values of 14.0 ± 4.3, 20.3 ± 17.7, 29.2 ± 29.6, and 68.1 h in groups A, B, C, and D, respectively (P = 0.002). At a dose level of 130 mg/m2, the area under the concentration time curve increased in with the degree of renal impairment, with values of 16.4 ± 5.03, 39.7 ± 11.5, and 44.6 ± 14.6 μg·h/mL, in groups A, B, and C, respectively. However, there was no increase in pharmacodynamic drug-related toxicities. Estimated CrCL using the Cockcroft-Gault method approximated the measured 24-h urinary CrCL (mean prediction error, −5.0 mL/min). Conclusions: Oxaliplatin pharmacokinetics are altered in patients with renal impairment, but a corresponding increase in oxaliplatin-related toxicities is not observed.

Phase 1 Study of Weekly Polyethylene Glycol-Camptothecin in Patients with Advanced Solid Tumors and Lymphomas

Purpose: To determine the maximal tolerated dose and dose-limiting toxicities (DLT) of pegamotecan (polyethylene glycol-camptothecin) in patients with advanced malignancies when administered in cycles of once weekly for 3 of 4 weeks. Experimental Design: Eligible patients had advanced solid tumors that failed to respond to standard therapy or for which no standard therapy was available, including also the following criteria: measurable disease, Eastern Cooperative Oncology Group performance status of ≤2, and acceptable organ function. Pegamotecan was administered as a 60-minute infusion, with successive patient cohorts receiving escalating doses from 800 to 4,300 mg/m2. The primary end point was to determine the maximal tolerated dose. Other end points were toxicity, pharmacokinetics, pharmacodynamics, and efficacy. Pharmacokinetic analysis measured free camptothecin. Pharmacodynamic analysis correlated drug effects with pegamotecan dose and pharmacokinetic variables. Results: Twenty-seven patients were enrolled. The maximal tolerated dose was 3,240 mg/m2. Grade 4 neutropenia, the DLT, was noted in two of four patients treated at 4,300 mg/m2. Other grade 3 and 4 toxicities were anemia, thrombocytopenia, fatigue, prolonged partial thromboplastin time, hemorrhagic cystitis, dysuria, and urinary frequency. Pharmacokinetic analysis showed the apparent terminal elimination half-life to be 46 ± 12.8 hours. Pharmacodynamic analysis showed that hematuria occurred in 8 of 15 patients with an area under the curve extrapolated to infinity (AUC0-∞) > 20 ng h/mL and 0 of 10 patients with an AUC0-∞ ≤ 20 ng h/mL. Unconfirmed partial responses were observed in two patients, one with metastatic small bowel adenocarcinoma and the other with metastatic esophageal cancer. Conclusions: The maximal tolerated dose of pegamotecan when administered weekly for 3 of 4 weeks is 3,240 mg/m2. The DLT was neutropenia. Among nonhematologic toxicities, the incidence of gastrointestinal toxicity was low, but genitourinary toxicity seems to occur in the same effective dose range as noted with native camptothecin in earlier trials (27-43 mg/m2). The observed antitumor activity suggests that pegamotecan has single-agent activity and merits further investigation in phase 2 studies.

Troxacitabine, an l-Stereoisomeric Nucleoside Analog, on a Five-Times-Daily Schedule: A Phase I and Pharmacokinetic Study in Patients With Advanced Solid Malignancies

PURPOSE To assess the feasibility of administering troxacitabine, a unique L-nucleoside that is not a substrate for deoxycytidine deaminase-mediated catabolism, as a 30-minute intravenous (IV) infusion daily for 5 days. PATIENTS AND METHODS Patients with advanced solid malignancies were treated with escalating doses of troxacitabine as a 30-minute IV infusion daily for 5 days. Plasma and urine sampling was performed to characterize the pharmacokinetics and pharmacodynamics of troxacitabine. RESULTS Thirty-nine patients received 124 courses of troxacitabine at eight dose levels ranging from 0.12 to 1.8 mg/m(2)/d. Severe neutropenia that was protracted (> 5 days) and/or associated with fever, and skin rashes were consistently experienced by heavily (HP) and minimally pretreated (MP) patients at doses exceeding 1.2 and 1.5 mg/m(2)/d, respectively. At troxacitabine doses > or = 1.2 mg/m(2)/d, treatment was often delayed 1 additional week for complete resolution of hematologic effects, resulting in lengthening of the treatment interval from every 3 to 4 weeks. Skin rash, palmar-plantar erythrodysesthesia, and thrombocytopenia were also observed and were occasionally severe, particularly at the highest doses. A patient with metastatic ocular melanoma experienced a partial response. Pharmacokinetics of troxacitabine were dose-independent; mean (SD) values for the volume of distribution at steady-state and clearance (Cl(s)) were 60 (32) L and 161 (33) mL/min, respectively, on day 1. After treatment on the fifth day, terminal half-life values averaged 39 (63) hours, and Cl(s) was reduced by approximately 20%, averaging 127 (27) mL/min. The principal mode of drug elimination was renal. CONCLUSION Recommended doses for phase II studies of troxacitabine as a 30-minute infusion daily for 5 days every 4 weeks are 1.5 and 1.2 mg/m(2)/d for MP and HP patients, respectively. Broad disease-directed evaluations of troxacitabine on this schedule and possibly less frequent schedules are warranted.

Administration of oxaliplatin to patients with renal dysfunction: a preliminary report of the national cancer institute organ dysfunction working group

Oxaliplatin is an approved agent with clinical activity in the treatment of advanced colorectal cancer. Preliminary pharmacokinetic evidence suggests that oxaliplatin is predominantly cleared by renal excretion; however, formal dosing guidelines in patients with renal impairment are lacking. The National Cancer Institute Organ Dysfunction Working Group initiated the following dose-escalation pharmacokinetic trial of oxaliplatin in patients with varying degrees of renal function. Thirty-seven patients with various solid tumor malignancies were stratified into four renal dysfunction groups based on their measured 24-hour urinary creatinine clearance (CrCL). Patients in group A (controls) all had a CrCL >or= 60 mL/min; group B patients had mild renal dysfunction with CrCLs ranging from 40 to 59 mL/min; group C patients had moderate renal dysfunction with CrCLs of 20 to 39 mL/min; and patients with a CrCL < 20 mL/min were entered into the group D severe cohort. The starting oxaliplatin dose for patients in the normal group A was 130 mg/m(2), while lower doses of 105, 80, and 60 mg/m(2) were used in groups B, C, and D, respectively. Patients received a 2-hour intravenous infusion of oxaliplatin every 3 weeks, and doses were escalated in cohorts of three patients in each renal dysfunction group in the absence of any severe dose-limiting toxicity. Oxaliplatin-associated platinum pharmacokinetics were monitored in both plasma (bound + unbound) and plasma ultrafiltrates (unbound). Full single-agent doses of oxaliplatin of 130 mg/m(2) were well tolerated by patients with normal, mild, and moderate renal dysfunction in groups A, B, and C, respectively. Only one patient was enrolled in group D. Unbound platinum clearance significantly correlated with CrCL (r =.884), but the increased systemic exposures to circulating platinum were not associated with increased clinical toxicities. These data suggest that dose reductions of single-agent oxaliplatin are not necessary in patients with CrCLs >20 mL/min.

Phase I and Pharmacokinetic Study of Sequences of the Rebeccamycin Analogue NSC 655649 and Cisplatin in Patients with Advanced Solid Tumors

Purpose: To evaluate the feasibility of administering NSC 655649, a water-soluble rebeccamycin analogue that inhibits both topoisomerases I and II, in combination with cisplatin (CDDP) in adults with solid malignancies. Major toxicologic and pharmacologic differences between the two sequences of drug administration were also assessed. Experimental Design: NSC 655649 was administered as a 60-minute i.v. infusion; CDDP was given i.v. before or after NSC 655649 on day 1. Each patient was treated with alternating drug sequences every 3 weeks; doses of each drug were escalated in separate cohorts of new patients. Sequential dose escalation of NSC 655649 or CDDP resulted in three dosage permutations of NSC 655649/CDDP: 440/50, 550/50, and 440/75 mg/m2. After the maximum tolerated dose level was determined, the feasibility of using granulocyte colony-stimulating factor to permit further dose escalation was explored. Results: Twenty patients were treated with 70 courses of NSC 655649/CDDP. Myelosuppression was the principal toxicity. The incidence of severe neutropenia, often associated with severe thrombocytopenia, was unacceptably high in minimally pretreated patients at the NSC 655649/CDDP dose level of 550/50 mg/m2 without and with granulocyte colony-stimulating factor. Major pharmacokinetic interactions between NSC 655649 and CDDP were not apparent. No relevant sequence-dependent differences in toxicity or pharmacokinetic variables occurred. Three patients had partial responses. Conclusions: NSC 655649 and CDDP were well tolerated by minimally pretreated subjects at 440 and 50 mg/m2, respectively. Neither pharmacokinetic interactions between the agents nor sequence-dependent toxicologic or pharmacokinetic effects were apparent. The tolerance and preliminary activity observed with this combination suggest that disease-directed evaluations of the regimen are warranted.