Safgren, Stephanie L

Abstract Background: Controversy exists regarding the association between CYP2D6 enzyme activity and tamoxifen effectiveness in the adjuvant treatment of invasive breast cancer; however, this association in the primary prevention of breast cancer is unknown. Methods: We conducted a nested case–control study in the context of the NSABP P1 and P2 prevention trials to determine the impact of CYP2D6 genotype, CYP2D6 inhibitor use, and metabolizer status (CYP2D6 genotype combined with CYP2D6 inhibitor use), on breast cancer events. Women who developed breast cancer (both noninvasive and invasive) while on 5 years of selective estrogen receptor modulators therapy (cases) were matched to controls free of breast cancer. Comprehensive CYP2D6 genotyping was conducted for alleles associated with absent (*3, *4, *5, and *6), reduced (*10, *17, and *41), and increased (*1XN and *2XN) enzyme activity. Information regarding the use of CYP2D6 inhibitors was recorded. Results: A total of 591 cases were matched to 1,126 controls and DNA was genotyped in more than 97%. In patients treated with tamoxifen, there was no association of CYP2D6 genotype [OR (extensive/poor metabolizer): 0.90; 95% CI: 0.46–1.74, P = 0.74), use of a potent CYP2D6 inhibitor (OR 0.92; 95% CI: 0.575–1.486), or CYP2D6 metabolizer status (OR 1.03; 95% CI: 0.669–1.607) with breast cancer occurrence. Likewise, there was no association between any CYP2D6 metabolism parameter with breast cancer events in raloxifene-treated patients. Conclusion: In the NSABP P1 and P2 clinical trials, alterations in CYP2D6 metabolism are not associated with either tamoxifen or raloxifene efficacy. Clin Cancer Res; 17(21); 6944–51. ©2011 AACR.

Abstract Two cytidine analogues, gemcitabine (dFdC) and 1-β-d-arabinofuranosylcytosine (AraC), show significant therapeutic effect in a variety of cancers. However, response to these drugs varies widely. Evidence from tumor biopsy samples shows that expression levels for genes involved in the cytidine transport, metabolism, and bioactivation pathway contribute to this variation in response. In the present study, we set out to test the hypothesis that variation in gene expression both within and outside of this “pathway” might influence sensitivity to gemcitabine and AraC. Specifically, Affymetrix U133 Plus 2.0 GeneChip and cytotoxicity assays were performed to obtain basal mRNA expression and IC50 values for both drugs in 197 ethnically defined Human Variation Panel lymphoblastoid cell lines. Genes with a high degree of association with IC50 values were involved mainly in cell death, cancer, cell cycle, and nucleic acid metabolism pathways. We validated selected significant genes by performing real-time quantitative reverse transcription-PCR and selected two representative candidates, NT5C3 (within the pathway) and FKBP5 (outside of the pathway), for functional validation. Those studies showed that down-regulation of NT5C3 and FKBP5 altered tumor cell sensitivity to both drugs. Our results suggest that cell-based model system studies, when combined with complementary functional characterization, may help to identify biomarkers for response to chemotherapy with these cytidine analogues. [Cancer Res 2008;68(17):7050–8]

Abstract One of the key challenges in anticancer therapy is the toxicity and poor bioavailability of the anticancer drugs. Nanotechnology can play a pivotal role by delivering drugs in a targeted fashion to the malignant cells that will reduce the systemic toxicity of the anticancer drug. In this report, we show a stepwise development of a nanoparticle-based targeted delivery system for in vitro and in vivo therapeutic application in pancreatic cancer. In the first part of the study, we have shown the fabrication and characterization of the delivery system containing gold nanoparticle as a delivery vehicle, cetuximab as a targeting agent, and gemcitabine as an anticancer drug for in vitro application. Nanoconjugate was first characterized physico-chemically. In vitro targeting efficacy, tested against three pancreatic cancer cell lines (PANC-1, AsPC-1, and MIA Paca2) with variable epidermal growth factor receptor (EGFR) expression, showed that gold uptake correlated with EGFR expression. In the second part, we showed the in vivo therapeutic efficacy of the targeted delivery system. Administration of this targeted delivery system resulted in significant inhibition of pancreatic tumor cell proliferation in vitro and orthotopic pancreatic tumor growth in vivo. Tumor progression was monitored noninvasively by measuring bioluminescence of the implanted tumor cells. Pharmacokinetic experiments along with the quantitation of gold both in vitro and in vivo further confirmed that the inhibition of tumor growth was due to targeted delivery. This strategy could be used as a generalized approach for the treatment of a variety of cancers characterized by overexpression of EGFR. [Cancer Res 2008;68(6):1970–8]

PurposeWe report results of a phase I trial and pharmacokinetic study of pemetrexed (LY231514) in children and adolescents with refractory solid tumors. Pemetrexed is a novel antifolate that inhibits multiple enzymes necessary for the biosynthesis of thymidine and purine nucleotides. The purpose of this study was to determine the maximum-tolerated dose (MTD), dose-limiting toxicities (DLTs), and pharmacokinetic properties of pemetrexed in children.Patients and MethodsPemetrexed was administered as a 10-minute intravenous infusion every 21 days. Patients received vitamin B12and folic acid supplementation as well as dexamethasone prophylaxis. Cohorts of three to six children were enrolled at dose levels of 400, 520, 670, 870, 1,130, 1,470, 1,910, and 2,480 mg/m2. Pharmacokinetic studies were performed during the first course of treatment.ResultsThirty-three patients (31 assessable) with a median age of 12 years were enrolled. DLT occurred in one of six patients at 1,470 mg/m2and two of four patients at 2,480 mg/m2. The MTD was 1,910 mg/m2. The primary DLTs were neutropenia and rash. No objective antitumor responses were seen. Mean plasma clearance, half-life, and steady-state volume of distribution values were 2.3 L/h/m2, 2.5 hours, and 5.4 L/m2, respectively.ConclusionPemetrexed is well-tolerated in children with refractory solid tumors at doses similar to the MTD in adults. The recommended dose for phase II studies is 1,910 mg/m2administered every 21 days with dexamethasone, folic acid, and vitamin B12supplementation.

Abstract Purpose: To determine the recommended phase 2 dose, dose-limiting toxicities (DLT), pharmacokinetic profile, and pharmacodynamics of the heat shock protein (Hsp) 90 inhibitor, 17-allylaminogeldanamycin (17-AAG). Experimental Design: 17-AAG was administered as a 60-min infusion, on days 1, 4, 8, and 11 of a 21-day cycle at dose levels of 150, 200, 270, and 360 mg/m2/dose. Pharmacokinetic studies and evaluations for Hsp72 and Akt levels in peripheral blood mononuclear cells were done during the first course of therapy. Results: Seventeen patients (7 males), median 7 years of age (range, 1-19 years), were enrolled using a standard dose escalation scheme. No DLTs were observed. Although there were no objective responses, three patients remain on therapy at 6+, 7+, and 9+ months with stable disease. One patient with hepatoblastoma had a reduction in α-fetoprotein and stable disease over three cycles. At 270 mg/m2/dose, the Cmax and areas under the plasma concentration-time curves of 17-AAG were 5,303 ± 1,591 ng/mL and 13,656 ± 4,757 ng/mL h, respectively, similar to the exposure in adults. The mean terminal half-life for 17-AAG was 3.24 ± 0.80 h. Induction of Hsp72, a surrogate marker for inhibition of Hsp90, was detected at the 270 mg/m2 dose level. Conclusions: Drug exposures consistent with those required for anticancer activity in preclinical models were achieved without DLT. Evidence for drug-induced modulation of Hsp90 systemically was also detected. The recommended phase II dose of 17-AAG is 360 mg/m2/d. Non-DMSO–containing formulations may improve acceptance of this drug by children and their families.

Abstract Purpose: To determine the maximum tolerated dose (MTD), dose-limiting toxicity, and pharmacokinetics of 17-allylamino-demethoxy-geldanamycin (17-AAG) administered on days 1, 4, 8, and 11 every 21 days and to examine the effect of 17-AAG on the levels of chaperone and client proteins. Experimental Design: A phase I dose escalating trial in patients with advanced solid tumors was done. Toxicity and tumor responses were evaluated by standard criteria. Pharmacokinetics were done and level of target proteins was measured at various points during cycle one. Results: Thirteen patients were enrolled in the study. MTD was defined as 220 mg/m2. Dose-limiting toxicities were as follows: dehydration, diarrhea, hyperglycemia, and liver toxicity. At the MTD, the mean clearance of 17-AAG was 18.7 L/h/m2. There was a significant decrease in integrin-linked kinase at 6 hours after infusion on day 1 but not at 25 hours in peripheral blood mononuclear cells. Treatment with 17-AAG on day 1 significantly increased pretreatment levels of heat shock protein (HSP) 70 on day 4, which is consistent with the induction of a stress response. In vitro induction of a stress response and up-regulation of HSP70 resulted in an increased resistance to HSP90-targeted therapy in A549 cells. Conclusions: The MTD of 17-AAG on a twice-weekly schedule was 220 mg/m2. Treatment at this dose level resulted in significant changes of target proteins and also resulted in a prolonged increase in HSP70. This raises the possibility that HSP70 induction as part of the stress response may contribute to resistance to 17-AAG.

Purpose Polymorphisms in tamoxifen metabolizing genes affect the plasma concentration of tamoxifen metabolites, but their effect on clinical outcome is unknown. Methods We determined cytochrome P450 (CYP)2D6 (*4 and *6) and CYP3A5 (*3) genotype from paraffin-embedded tumor samples and buccal cells (living patients) in tamoxifen-treated women enrolled onto a North Central Cancer Treatment Group adjuvant breast cancer trial. The relationship between genotype and disease outcome was determined using the log-rank test and Cox proportional hazards modeling. Results Paraffin blocks were obtained from 223 of 256 eligible patients, and buccal cells were obtained from 17 living women. CYP2D6 (*4 and *6) and CYP3A5 (*3) genotypes were determined from 190, 194, and 205 patient samples and in 17 living women. The concordance rate between buccal and tumor genotype was 100%. Women with the CYP2D6 *4/*4 genotype had worse relapse-free time (RF-time; P = .023) and disease-free survival (DFS; P = .012), but not overall survival (P = .169) and did not experience moderate to severe hot flashes relative to women heterozygous or homozygous for the wild-type allele. In the multivariate analysis, women with the CYP2D6 *4/*4 genotype still tended to have worse RFS (hazard ratio [HR], 1.85; P = .176) and DFS (HR, 1.86; P = .089). The CYP3A5*3 variant was not associated with any of these clinical outcomes. Conclusion In tamoxifen-treated patients, women with the CYP2D6 *4/*4 genotype tend to have a higher risk of disease relapse and a lower incidence of hot flashes, which is consistent with our previous observation that CYP2D6 is responsible for the metabolic activation of tamoxifen to endoxifen.

Abstract Purpose: To assess the maximum tolerated dose, toxicities, pharmacokinetics, and antileukemic activity of topotecan and carboplatin in adults with recurrent or refractory acute leukemias. Experimental Design: Patients received topotecan and carboplatin by 5-day continuous infusion at nine dose levels. Patients achieving a complete remission received up to two additional courses for consolidation. Plasma topotecan and ultrafilterable platinum were assayed on days 1 to 5. In addition, pretreatment levels of various polypeptides in leukemic cells were examined by immunoblotting to assess possible correlations with response. Results: Fifty-one patients received a total of 69 courses of therapy. Dose-limiting toxicity consisted of grade 4/5 typhlitis and grade 3/4 mucositis after one course of therapy or grade 4 neutropenia and thrombocytopenia lasting >50 days when a second course was administered on day 21. Among 45 evaluable patients, there were 7 complete remissions, 2 partial remissions, 1 incomplete complete remission, and 1 reversion to chronic-phase chronic myelogenous leukemia. Topotecan steady-state plasma concentrations increased with dose. No accumulation of topotecan or ultrafilterable platinum occurred between days 1 and 5 of therapy. Leukemic cell levels of topoisomerase I, checkpoint kinase 1, checkpoint kinase 2, and Mcl-1 correlated with proliferating cell nuclear antigen but not with response. In contrast, low Bcl-2 expression correlated with response (P = 0.014, Mann-Whitney U test). Conclusions: The maximum tolerated dose was 1.6 mg/m2/d topotecan plus 150 mg/m2/d carboplatin. The complete remission rate in a heavily pretreated population was 16% (33% at the highest three dose levels). Responses seem to correlate with low pretreatment blast cell Bcl-2 expression.

Purpose We determined the maximum-tolerated dose (MTD) and the dose-limiting toxicities (DLT) of 17-allylamino-17-demethoxygeldanamycin (17-AAG) when infused on days 1, 8, and 15 of a 28-day cycle in advanced solid tumor patients. We also characterized the pharmacokinetics of 17-AAG, its effect on chaperone and client proteins, and whether cytochrome P450 (CYP) 3A5 and NAD(P)H:quinone oxidoreductase 1 (NQO1) polymorphisms affected 17-AAG disposition or toxicity. Patients and Methods An accelerated titration design was used. Biomarkers were measured in peripheral-blood mononuclear cells (PBMCs) at baseline and on days 1 and 15, and pharmacokinetic analysis was performed on day 1 of cycle 1. CYP3A5*3 and NQO1*2 genotypes were determined and correlated with pharmacokinetics and toxicity. Results Twenty-one patients received 52 courses at 11 dose levels. DLTs at 431 mg/m2 were grade 3 bilirubin (n = 1), AST (n = 1), anemia (n = 1), nausea (n = 1), vomiting (n = 1), and myalgias (n = 1). No tumor responses were seen. 17-AAG consistently increased heat shock protein (Hsp) 70 levels in PBMCs. At the MTD, the clearance and half-life (t1/2) of 17-AAG were 11.6 L/h/m2 and 4.15 hours, respectively; whereas the active metabolite 17-aminogeldanamycin had a t1/2 of 7.63 hours. The CYP3A5*3 and NQO1*2 polymorphisms were not associated with 17-AAG toxicity. The CYP3A5*3 polymorphism was associated with higher 17-AAG clearance. Conclusion The MTD of weekly 17-AAG is 308 mg/m2. 17-AAG induced Hsp70 in PBMCs, indicating that Hsp90 has been affected. Further evaluation of 17-AAG is ongoing using a twice-weekly regimen, and this schedule of 17-AAG is being tested in combination with chemotherapy.