Challenges of characterizing proarrhythmic risk due to QTc prolongation induced by nonadjuvant anticancer agents.

BACKGROUND: Drug-induced QTc prolongation is becoming increasingly important in oncology since novel therapies result in prolonged survival of cancer patients already predisposed to cardiotoxicity. METHODS: We review the challenges of implementing the ICH E14 guidance in oncology and propose an integrated approach to QTc risk assessment of nonadjuvant anticancer agents (NAAs), with quantitative outcome criteria. RESULTS: We recommend informed use of non-clinical cardiac safety pharmacology results, some degree of robust ECG assessments in early phase studies, a dedicated QTc study in cancer patients conducted at the appropriate time pre-, peri-, or post-approval (with the design and timing agreed upon with regulatory agencies), and ECG monitoring in late-phase studies commensurate with the outcome of previous QTc studies. CONCLUSION: The proposed approach would facilitate risk-benefit assessment for NAAs during clinical development and regulatory review, and enable adequate labeling for safe and effective postmarketing use in cancer patients.

The effect of mild and moderate hepatic impairment on the pharmacokinetics of valdecoxib, a selective COX-2 inhibitor.

PURPOSE: This study evaluated the effects of varying degrees of hepatic impairment on the pharmacokinetics and safety of valdecoxib following single and multiple dosing. METHODS: This was an open-label, randomised, parallel group study in 12 subjects with mild hepatic impairment (Child-Pugh Class A) and in 13 with moderate hepatic impairment (Child-Pugh Class B) matched for age, weight, sex, and smoking status; there were two control groups of 12 healthy volunteers, one for each study group. All subjects received a single dose of valdecoxib 20 mg on day 1 and valdecoxib 20 mg twice daily on days 4-7, followed by a single morning dose on day 8. Plasma concentrations of free (unbound) and total valdecoxib and its active hydroxylated metabolite (SC-66905) were measured following single and multiple dosing (day 1 and day 8). Additionally, all subjects received a single intravenous dose of lidocaine 60 mg during the pretreatment period to determine plasma concentrations of monoethylglycinexylidide (MEGX) as a marker of hepatic CYP3A4 activity. RESULTS: The mean apparent oral clearance of free valdecoxib in plasma at steady state decreased by 22-25% in those with mild to moderate impairment (corresponding to a 28-33% increase in the AUC of free valdecoxib and a 19-23% decrease in the AUC of total SC-66905). The mean free fraction of valdecoxib in plasma increased by 9-38%, resulting in a mean decrease in apparent oral clearance of total valdecoxib in plasma of 0-15% (corresponding to a 0-17% increase in the AUC of total valdecoxib). Individual AUCs for free valdecoxib and total SC-66905 did not correlate well with AUCs for MEGX, indicating that decreases in intrinsic clearance of valdecoxib in those with hepatic impairment could not solely be explained by decreased CYP3A4 expression in hepatic impairment. CONCLUSIONS: In our small study sample, mild and moderate hepatic impairment appeared to have only a modest effect on valdecoxib and SC-66905 pharmacokinetics. The adjustment of valdecoxib dose or dosing regimen does not appear mandatory in subjects with mild or moderate hepatic impairment, although caution is necessary during treatment of these patients with valdecoxib.

Valdecoxib, a COX-2-specific inhibitor, does not affect cardiac repolarization.

This double-blind, four-way crossover study assessed the effect of valdecoxib on the QTc interval duration in 25 male and 9 female healthy adults. Subjects received placebo or 40 mg, 80 mg, or 120 mg valdecoxib once daily for 5 days. Serial ECGs were obtained for 24 hours before the first treatment (baseline) and on the 5th day of each treatment. The study was statistically powered to detect a difference of > or = 5.6 ms in the average daily QTc change from baseline and a > or = 7.8-ms difference in the average maximal daily change from baseline. No QTc prolongation versus placebo (Fridericia's or Bazett's correction) was observed for any valdecoxib dose. A 22% greater than proportional increase in valdecoxib AUC0-24 was observed over the 40- to 120-mg dose range, supporting the conclusiveness of the negative QTc risk assessment even at supratherapeutic doses (up to three times the maximum recommended dose of 40 mg per day) and concentrations. In conclusion, repeated administration of doses up to 120 mg valdecoxib had no effect on cardiac repolarization in healthy volunteers, suggesting that chronic administration of valdecoxib to patients would not increase the risk from cardiac arrhythmia associated with QT prolongation.

Assessment of normal and tumor tissue uptake of MAG-CPT, a polymer-bound prodrug of camptothecin, in patients undergoing elective surgery for colorectal carcinoma.

PURPOSE: MAG-camptothecin (MAG-CPT) is the lead compound of a novel drug delivery system in which an active cytotoxic moiety, camptothecin (CPT), is covalently linked to a soluble polymeric carrier (MAG) to form an inactive prodrug. The mechanism of action of CPT remains unaltered, but the delivery system is thought to allow the carrier-bound drug to accumulate in tumor tissues and release the active CPT locally. This proof-of-concept clinical study was designed to determine whether MAG-CPT was preferentially delivered to or retained in tumor tissue compared to adjacent normal tissue or plasma, and to estimate the degree of intratissue release of CPT. METHODS: This was an open, non-randomized study in ten adult patients scheduled for elective surgery for colorectal cancer. Patients received a single dose of 60 mg/m2 (CPT equivalent) of MAG-CPT 24 h, 3 days or 7 days prior to surgery. Plasma, tumor, and adjacent normal tissue samples were collected simultaneously at the time of surgery and analyzed for MAG-bound and released CPT concentrations. RESULTS: MAG-bound and free CPT concentrations in plasma, tumor, and normal tissue achieved equilibrium by 24 h after dosing, declining in parallel up to 7 days after dosing. MAG-bound CPT was delivered to similar levels to tumor and normal tissue. At 24 h after dosing, the mean+/-SD MAG-bound CPT concentrations were 861+/-216 ng/g in tumor and 751+/-215 ng/g in adjacent normal tissue, and free CPT concentrations were lower in tumor than in normal tissue (12.2+/-4.7 ng/g and 21.9+/-6.7 ng/g, respectively). At 24 h after dosing, mean+/-SD ratios of MAG-bound and free CPT in tumor and plasma were 0.13+/-0.03 and 0.22+/-0.09, respectively, and the ratios did not change for up to 7 days after dosing, indicating a lack of preferential retention of MAG-bound CPT or release of free CPT in tumor. These results are in marked contrast to previous data from animal tumor xenograft studies, where MAG-CPT levels were higher in tissue than in plasma at 3 and 7 days after a single i.v. dose. CONCLUSIONS: Delivery of CPT to the target tumor tissue is achievable by means of the MAG-CPT polymer-bound delivery system, with the equilibrium between plasma and tumor tissue concentrations of released CPT being established within 24 h after dosing. However, preferential retention of MAG-bound or released CPT in the tumor relative to normal tissue or plasma was not detected during the 7 days after dosing. The methods employed in our study could be of use in making "go/no-go" decisions on further development of anticancer drugs.

The pharmacokinetics of sumatriptan when administered with norethindrone 1 mg/ethinyl estradiol 0.035 mg in healthy volunteers.

BACKGROUND: Because the majority of migraineurs are young women in their peak reproductive years, it is important to understand the possible effects on the pharmacokinetics of both medications when sumatriptan is coadministered with an oral contraceptive (OC). OBJECTIVES: The primary objective of this study was to assess the effect of multiple dosing of the OC norethindrone 1 mg/ethinyl estradiol 0.035 mg (NE/EE) on the single-dose pharmacokinetics of sumatriptan in healthy volunteers. Secondary objectives were to determine the effect of a single dose of sumatriptan on the multiple-dose pharmacokinetics of NE and EE, and to assess the safety and tolerability of the combination. METHODS: This was an open-label, 1-sequence, crossover study in healthy women who had been receiving NE/EE for at least 3 months. Subjects received 1 cycle of NE/EE, consisting of 21 days of OC and 7 days of placebo. They also received a single dose of sumatriptan 50 mg on the last day of the OC or placebo regimen. Blood samples for the determination of plasma sumatriptan concentrations were collected on days 21 and 28, and blood samples for the determination of plasma NE and EE concentrations were collected on days 20 and 21. Treatments were compared by analysis of variance. Equivalence between treatments was to be concluded if the 90% Cl for the ratio of reference to test means for log(e)-transformed parameters (area under the plasma concentration-time curve [AUCI and maximum measured plasma concentration [C(max)]) for each analyte fell within the interval 0.80 to 1.25. RESULTS: Twenty-six women (mean age, 29.8 years; age range, 18-44 years; weight range, 52-82 kg) participated in the study. The 90% CI for the ratio of reference to test means for the AUC extrapolated to infinity (AUC(infinity)) of sumatriptan was 1.11 to 1.22, and the 90% CIs for the AUC over the dosing interval at steady state (AUC(tau)) of NE and EE were 0.96 to 1.00 and 0.91 to 0.97, respectively. The 90% CIs for the ratio of reference to test means for the C(max) of sumatriptan, NE, and EE were a respective 1.05 to 1.30, 0.76 to 0.88, and 0.88 to 1.04. Study treatments were well tolerated. Adverse events were mild or moderate, and there were no clinically significant changes in vital signs or laboratory values. CONCLUSIONS: The extent of absorption (AUC) of sumatriptan, NE, and EE was similar after oral administration of sumatriptan and NE/EE, both alone and in combination. Thus, in the opinion of the study investigators, there were no clinically relevant changes in the AUC of any of the medications when sumatriptan and NE/EE were administered concomitantly compared with administration alone. The results of this study suggest that dose adjustment is not necessary when sumatriptan is administered concomitantly with NE/EE in healthy premenopausal women.