Small intestine neuroendocrine tumors (SI-NETs) are the most common malignancy of the small bowel. Several clinical trials target PI3K/Akt/mTOR signaling; however, it is unknown whether these or other genes are genetically altered in these tumors. To address the underlying genetics, we analyzed 48 SI-NETs by massively parallel exome sequencing. We detected an average of 0.1 somatic single nucleotide variants (SNVs) per 106 nucleotides (range, 0–0.59), mostly transitions (C>T and A>G), which suggests that SI-NETs are stable cancers. 197 protein-altering somatic SNVs affected a preponderance of cancer genes, including FGFR2, MEN1, HOOK3, EZH2, MLF1, CARD11, VHL, NONO, and SMAD1. Integrative analysis of SNVs and somatic copy number variations identified recurrently altered mechanisms of carcinogenesis: chromatin remodeling, DNA damage, apoptosis, RAS signaling, and axon guidance. Candidate therapeutically relevant alterations were found in 35 patients, including SRC, SMAD family genes, AURKA, EGFR, HSP90, and PDGFR. Mutually exclusive amplification of AKT1 or AKT2 was the most common event in the 16 patients with alterations of PI3K/Akt/mTOR signaling. We conclude that sequencing-based analysis may provide provisional grouping of SI-NETs by therapeutic targets or deregulated pathways.
To determine the response rate to oral capsular fenretinide in children with recurrent or biopsy proven refractory high-risk neuroblastoma.
Patients received 7 days of fenretinide: 2475 mg/m2/day divided TID (<18 years) or 1800 mg/m2/day divided BID (≥18 years) every 21 days for a maximum of 30 courses. Patients with stable or responding disease after course 30 could request additional compassionate courses. Best response by course 8 was evaluated in Stratum 1 (measurable disease on CT/MRI +/− bone marrow and/or MIBG avid sites) and Stratum 2 (bone marrow and/or MIBG avid sites only).
Sixty-two eligible patients, median age 5 years (range 0.6–19.9), were treated in Stratum 1 (n=38) and Stratum 2 (n=24). One partial response (PR) was seen in Stratum 2 (n=24 evaluable). No responses were seen in Stratum 1 (n=35 evaluable). Prolonged stable disease (SD) was seen in 7 patients in Stratum 1 and 6 patients in Stratum 2 for 4–45+ (median 15) courses. Median time to progression was 40 days (range 17–506) for Stratum 1 and 48 days (range 17–892) for Stratum 2. Mean 4-HPR steady state trough plasma concentrations were 7.25 µM (coefficient of variation 40–56%) at day 7 course 1. Toxicities were mild and reversible.
Although neither stratum met protocol criteria for efficacy, 1 PR + 13 prolonged SD occurred in 14/59 (24%) of evaluable patients. Low bioavailability may have limited fenretinide activity. Novel fenretinide formulations with improved bioavailability are currently in pediatric Phase I studies.
fenretinide; neuroblastoma; Phase II; ANBL0321
Tamoxifen biotransformation to endoxifen, a potent antiestrogen, is catalyzed by CYP2D6. In addition, CYP2C19 and SULT1A1 have also been implicated in the metabolism of tamoxifen. We sought to evaluate the importance of SULT1A1 copy number and CYP2C19*17 on disease-free survival (DFS) in postmenopausal women randomized to tamoxifen monotherapy in North Central Cancer Treatment Group 89-30-52 from January 1991 to April 1995.
Materials & methods
We extracted DNA from paraffin-embedded tumors and determined tumor SULT1A1 copy number and CYP2C19*17 genotype. The association of genotype with DFS was determined using the log-rank test. Multivariate cox modeling was performed using traditional prognostic factors, as well as CYP2D6 genotype. SULT1A1 copy number and CYP2C19*17 genotype was determined in 190 out of 256 patients (95% Caucasian).
The median follow-up for living patients was 14 years. DFS did not differ according to SULT1A1 copy number (p = 0.482) or CYP2C19*17 genotype (p = 0.667). Neither SULT1A1 copy number or CYP2C19*17 genotype was associated with disease recurrence in this cohort.
Future studies are needed to identify whether other genetic and environmental factors which affect tamoxifen metabolism are associated with tamoxifen clinical outcomes.
breast cancer; copy number polymorphism; CYP2C19; pharmacogenomic; polymorphism; single nucleotide; SULT1A1; tamoxifen
Gemcitabine is a cytidine analogue used in the treatment of various solid tumors. Little is known about how gemcitabine and its metabolites are transported out of cells. We set out to study the efflux of gemcitabine and the possible consequences of that process in cancer cells. We observed the efflux of gemcitabine and its deaminated metabolite, 2’,2’-difluorodeoxyuridine (dFdU) using high performance liquid chromatography and tandem mass spectrometry (LC-MS/MS) after gemcitabine treatment. Non-selective ABCC-transport inhibition with probenecid significantly increased intracellular dFdU concentrations, with a similar trend observed with verapamil, a non-selective ABCB1 and ABCG2 transport inhibitor. Neither probenecid nor verapamil altered intracellular gemcitabine levels after the inhibition of deamination with tetrahydrourudine, suggesting that efflux of dFdU, but not gemcitabine, was mediated by ABC transporters. MTS assays showed that probenecid increased sensitivity to gemcitabine. While dFdU displayed little cytotoxicity, intracellular dFdU accumulation inhibited cytidine deaminase, resulting in increased gemcitabine levels and enhanced cytotoxicity. Knockdown of ABCC3, ABCC5 or ABCC10 individually did not significantly increase gemcitabine sensitivity, suggesting the involvement of multiple transporters. In summary, ABCC-mediated efflux may contribute to gemcitabine resistance through increased dFdU efflux that allows for the continuation of gemcitabine deamination. Reversing efflux-mediated gemcitabine resistance may require broad-based efflux inhibition.
Gemcitabine; Cytotoxicity; Drug Efflux; Transport
Genetic variation in Cytochrome P450 2D6 (CYP2D6) and the gene expression ratio of the homeobox 13 (HOXB13) to interleukin-17B receptor (IL-17BR) are associated with tamoxifen resistance. We sought to determine the combined effect of inherited (CYP2D6) and somatic (HOXB13/IL17BR) gene variation in tamoxifen treated breast cancer.
Retrospective analysis of women with node negative breast cancer randomized to receive 5 years of tamoxifen (NCCTG 89-30-52). CYP2D6 metabolism (extensive or decreased) was based on CYP2D6*4 genotype and presence/absence of a CYP2D6 inhibitor. RT-PCR profiles for HOXB13 and IL-17BR and the cut-point separating patients into high and low risk categories according to disease-free survival (DFS) were utilized. A risk factor (CYP2D6:HOXB13/IL17BR) representing the four categories of combining CYP2D6 metabolism (extensive or decreased) and HOXB13/IL17BR (low or high) was created. The association between CYP2D6:HOXB13/IL17BR and DFS and overall survival (OS) was assessed using the log-rank test and proportional hazards modeling.
CYP2D6 metabolism and HOXB13/IL17BR gene ratio was available in 110/160 (69%) patients. The combined CYP2D6:HOXB13/IL17BR risk factor was significantly associated with DFS (log rank p=0.004) and OS (p=0.009). Relative to women with extensive CYP2D6 metabolism and low HOXB13/IL17BR, those with either decreased metabolism or a high HOXB13/IL17BR ratio had significantly worse OS [adjusted hazard ratio (HR) =2.41, 95% confidence interval:1.08-5.37; p=0.031) whereas women with both decreased metabolism and high HOXB13/IL17BR had the shortest survival (adjusted HR=3.15, 95% CI:1.17-8.52, p=0.024).
An index comprised of inherited (CYP2D6) and tumor (HOXB13/IL17BR) gene variation identifies patients with varying degrees of resistance to tamoxifen.
Tamoxifen; Cytochrome P450 2D6; HOXB13/IL17BR; Breast cancer
The purpose of this study was to determine the maximum-tolerated dose (MTD), dose-limiting toxicities (DLT), and pharmacokinetics of vorinostat administered as a single agent and in combination 13-cis retinoic acid (13cRA) in children with refractory solid tumors; to evaluate the tolerability of the solid tumor MTD in children with refractory leukemias; and to characterize the pharmacokinetics of a vorinostat suspension in children.
Patients and Methods
Vorinostat was administered orally daily starting at 180 mg/m2/d with escalations planned in 30% increments. Pharmacokinetic studies were performed with the initial dose. Acetyl-histone (H3) accumulation was assessed by Western blotting of peripheral blood mononuclear cells (PBMC).
Sixty-four patients were enrolled on this multipart trial. In patients with solid tumors, the MTD was 230 mg/m2/d with dose-limiting neutropenia, thrombocytopenia, and hypokalemia at 300 mg/m2/d. DLTs observed with the combination of 13cRA and vorinostat included thrombocytopenia, neutropenia, anorexia, and hypertriglyceridemia, resulting in a MTD of vorinostat 180 mg/m2/d 4 times per week and 13cRA 80 mg/m2/dose twice per day, days 1 through 14 every 28 days. Wide interpatient variability was noted in vorinostat disposition, with area under the concentration-time curves at 230 mg/m2/d for the capsule (range, 1,415 to 9,291 ng/mL × hr) and oral suspension (range, 1,186 to 4,780 ng/mL × hr). Significant accumulation of acetylated H3 histone in PBMC was observed after administration of vorinostat, particularly at higher doses. One patient with neuroblastoma experienced a complete response to the combination.
In children with recurrent solid tumors, vorinostat is well-tolerated at 230 mg/m2/d, with a modest dose reduction being required when combining vorinostat with 13cRA. Drug disposition is similar to that observed in adults.
Evidence has emerged that the clinical benefit of tamoxifen is related to the functional status of the hepatic metabolizing enzyme cytochrome P450 2D6 (CYP2D6). CYP2D6 is the key enzyme responsible for the generation of the potent tamoxifen metabolite, endoxifen. Multiple studies have examined the relationship of CYP2D6 status to breast cancer outcomes in tamoxifen-treated women; the majority of studies demonstrated that women with impaired CYP2D6 metabolism have lower endoxifen concentrations and a greater risk of breast cancer recurrence. As a result, practitioners must be aware that some of the most commonly prescribed medications coadministered with tamoxifen interfere with CYP2D6 function, thereby reducing endoxifen concentrations and potentially increasing the risk of breast cancer recurrence. After reviewing the published data regarding tamoxifen metabolism and the evidence relating CYP2D6 status to breast cancer outcomes in tamoxifen-treated patients, we are providing a guide for the use of medications that inhibit CYP2D6 in patients administered tamoxifen.
In pre-clinical models, temozolomide and vincristine are additive or synergistic with irinotecan. We examined this 3-drug combination in children with relapsed solid tumors. Patients received orally administered irinotecan together with temozolomide and vincristine on two different schedules, using cefixime to reduce irinotecan-associated diarrhea.
Oral irinotecan was given daily on days 1-5 and 8-12 (Schedule A), or on days 1-5 (Schedule B). Temozolomide was given on days 1-5, with vincristine 1.5 mg/m2 administered on days 1 and 8 (Schedule A) or day 1 (Schedule B) in 21-day courses.
On Schedule A, the maximum tolerated dose of oral irinotecan was 35 mg/m2/day combined with temozolomide 100 mg/m2/day and vincristine on days 1 and 8. Dose-limiting toxicities in 4 of 12 patients included hepatotoxicity, abdominal pain, anorexia, hypokalemia and thrombocytopenia at 50 mg/m2/day. Using Schedule B, 0 of 6 patients experienced dose-limiting toxicity at the highest doses studied of oral irinotecan 90 mg/m2/day, temozolomide 150 mg/m2/day × 5, and vincristine on day 1. First-course and cumulative toxicity was greater with Schedule A. UGT1A1*28 genotype did not correlate with dose-limiting toxicity. At the irinotecan dose of 90 mg/m2/day, the mean SN-38 AUCinf was 63 ng/ml*h. Activity was seen in sarcoma patients, and overall 8 patients received ≥ 6 courses.
The 5-day schedule of VOIT was well tolerated and provided SN-38 exposures similar to those achieved with intravenous IRN. Activity on this and prior studies suggests a potential role for VOIT in a spectrum of childhood solid tumors.
temozolomide; oral irinotecan; SN-38; vincristine; cefixime
Gemcitabine and other cytidine antimetabolites require metabolic activation by phosphorylation. Deoxycytidine kinase (DCK) and cytidine monophosphate kinase (CMPK) catalyze these reactions. We have applied a genotype-to-phenotype strategy to study DCK and CMPK pharmacogenomics. Specifically, we resequenced DCK and CMPK using 240 DNA samples, 60 each from African-American, Caucasian-American, Han Chinese-American and Mexican-American subjects. We observed 28 DCK polymorphisms and 28 polymorphisms in CMPK, 33 of which were novel. Expression in COS-1 cells showed that variant allozyme enzyme activities ranged from 32 to 105% of the wild type (WT) for DCK, and from 78 to 112% of WT for CMPK – with no significant differences in apparent Km values for either enzyme except for a DCK Val24/Ser122 double variant allozyme. Relative levels of DCK and CMPK immunoreactive protein in the COS-1 cells paralleled relative levels of enzyme activity and were significantly correlated for DCK (Rp = 0.89, P = 0.0004) but not for CMPK (Rp = 0.82, P = 0.095). The results of an analysis of DCK and CMPK structural models were compatible with the observed functional consequences of sequence alterations in variant allozymes. We also confirmed that the CMPK protein expressed in COS-1 cells and in a rabbit reticulocyte lysate was 196 rather than 228 amino acids in length. In summary, we determined common sequence variation in DCK and CMPK and systematically evaluated its functional implications. These gene sequence differences may contribute to variation in the metabolic activation of gemcitabine and other cytidine antimetabolites.
Aminoflavone is a unique DNA damaging agent currently undergoing phase I evaluation in a prodrug form (AFP464). In anticipation of combination regimens, interactions between aminoflavone and several anticancer drugs were investigated in MCF-7 breast cancer cells to determine whether synergistic cancer cell killing effects were observed.
Colony formation assays were performed to assess the effect of combining aminoflavone with a variety of anticancer drugs. Changes in initial uptake, retention or efflux of aminoflavone and the second agent were compared to the behavior of drugs alone. Key features required for aminoflavone activity in cell culture models were also explored, focusing on the obligatory induction of CYP1A1/1A2 and binding of reactive aminoflavone metabolites to tumor cell total macromolecules and DNA.
Aminoflavone was synergistic when co-incubated with paclitaxel, camptothecin or SN38. Uptake of neither aminoflavone nor any of the other three compounds was altered in combination incubations. Paclitaxel did not inhibit DNA binding of aminoflavone metabolites, while camptothecin did. Aminoflavone-induced CYP1A1 induction was observed in the presence of camptothecin or paclitaxel.
Aminoflavone is a promising therapeutic agent for breast cancer due to its unique mechanism of action compared to commonly used drugs. Combined treatments utilizing aminoflavone in conjunction with paclitaxel or camptothecin may provide an even greater cytotoxic effect than achieved with aminoflavone alone.
Aminoflavone; Paclitaxel; Camptothecin; Cytochrome P450; MCF-7
Irinotecan has radiosensitizing effects and shows synergism with nitrosoureas. We performed a Phase II study of RT and irinotecan, followed by BCNU plus irinotecan in newly-diagnosed GBM. The MTD for patients receiving enzyme-inducing anticonvulsants (EIAC) was as follows: irinotecan 400 mg/m2/week on Days 1, 8, 22 and 29 during RT, followed by BCNU 100 mg/m2 Day 1, and irinotecan, 400 mg/m2 on Days 1, 8, 22 and 29, every 6 weeks. The MTD for non-EIAC patients was as follows: irinotecan 125 mg/m2/week on Days 1, 8, 22 and 29 during RT, followed by BCNU 100 mg/m2 Day 1 and irinotecan 75 mg/m2 Days 1, 8, 22 and 29, every 6 weeks. Median OS was 10.8 mos. (95% CI: 7.7–14.9); OS at 12 months was 44.6% (95% CI: 33.3–59.8) and PFS 6 was 28.6% (95% CI: 18.9–43.2). Patients went off treatment due to adverse events (7%), refusal (11%), progressive disease (48%), death (9%), and other (9%); 16% completed protocol treatment. Survival was similar in patients with variant (6/7 or 7/7) and wild-type (6/6) UGT1A1*28 genotypic alleles. Grade 3–4 toxicity was more common in non-EIAC patients with variant alleles. SN-38 Cmax and AUC in EIAC patients receiving 400 mg/m2 irinotecan were 20.9 ng/ml and 212 ng/ml h, and in non-EIAC patients receiving 125 mg/m2, 15.5 ng/ml and 207 ng/ml h. SN-38 AUC varied by UGT1A1*28 status in non-EIAC patients. This regimen was not significantly active and radiosensitization was not observed. Non-EIAC patients with UGT1A1*28 variant alleles appear particularly sensitive to toxicity from irinotecan.
Glioblastoma; BCNU; Nitrosourea; Irinotecan; NCCTG; UGT1A1; Enzyme-inducing anticonvulsant
Vorinostat, a histone deacetylase inhibitor, represents a rational therapeutic target in glioblastoma multiforme (GBM).
Patients and Methods
Patients with recurrent GBM who had received one or fewer chemotherapy regimens for progressive disease were eligible. Vorinostat was administered at a dose of 200 mg orally twice a day for 14 days, followed by a 7-day rest period.
A total of 66 patients were treated. Grade 3 or worse nonhematologic toxicity occurred in 26% of patients and consisted mainly of fatigue (17%), dehydration (6%), and hypernatremia (5%); grade 3 or worse hematologic toxicity occurred in 26% of patients and consisted mainly of thrombocytopenia (22%). Pharmacokinetic analysis showed lower vorinostat maximum concentration and area under the curve (0 to 24 hours) values in patients treated with enzyme-inducing anticonvulsants, although this did not reach statistical significance. The trial met the prospectively defined primary efficacy end point, with nine of the first 52 patients being progression-free at 6 months. Median overall survival from study entry was 5.7 months (range, 0.7 to 28+ months). Immunohistochemical analysis performed in paired baseline and post-vorinostat treatment samples in a separate surgical subgroup of five patients with recurrent GBM showed post treatment increase in acetylation of histones H2B and H4 (four of five patients) and of histone H3 (three of five patients). Microarray RNA analysis in the same samples showed changes in genes regulated by vorinostat, such as upregulation of E-cadherin (P = .02).
Vorinostat monotherapy is well tolerated in patients with recurrent GBM and has modest single-agent activity. Histone acetylation analysis and RNA expression profiling indicate that vorinostat in this dose and schedule affects target pathways in GBM. Additional testing of vorinostat in combination regimens is warranted.
The purpose of this study was to determine the dose-limiting toxicities, maximum tolerated dose, pharmacokinetics, and intratumor and brain distribution of motexafin gadolinium (MGd) with involved field radiation therapy in children with newly diagnosed intrinsic pontine gliomas. MGd was administered as a 5-min intravenous bolus 2–5 h prior to standard radiation. The starting dose was 1.7 mg/kg. After first establishing that 5 doses/week for 6 weeks was tolerable, the dose of MGd was escalated until dose-limiting toxicity was reached. Radiation therapy was administered to 54 Gy in 30 once-daily fractions. Forty-four children received MGd at doses of 1.7 to 9.2 mg/kg daily prior to radiation therapy for 6 weeks. The maximum tolerated dose was 4.4 mg/kg. The primary dose-limiting toxicities were grade 3 and 4 hypertension and elevations in serum transaminases. Median elimination half-life and clearance values were 6.6 h and 25.4 ml/kg/h, respectively. The estimated median survival was 313 days (95% confidence interval, 248–389 days). The maximum tolerated dose of MGd and the recommended phase II dose was 4.4 mg/kg when administered as a daily intravenous bolus in conjunction with 6 weeks of involved field radiation therapy for pediatric intrinsic pontine gliomas.
motexafin gadolinium; pontine glioma; radiation therapy
Metaplastic breast carcinoma, a rare tumor composed of adenocarcinomatous and nonglandular growth patterns, is characterized by a propensity for distant metastases and resistance to standard anticancer therapies. We sought confirmation that this tumor is a basal-like breast cancer, expressing epidermal growth factor receptor (EGFR) and stem cell factor receptor (KIT). EGFR activating mutations and high copy number (associated with response to tyro-sine kinase inhibitor gefitinib) and KIT activating mutations (associated with imatinib sensitivity) were then investigated. Seventy-seven metaplastic cases were identified (1976-2006); 38 with tumor blocks available underwent pathologic confirmation before EGFR and KIT immunohistochemical analyses. A tissue microarray of malignant glandular and metaplastic elements was constructed and analyzed immunohistochemically for cytokeratin 5/6, estrogen receptor, progesterone receptor, and p63, and by fluorescence in situ hybridization for EGFR and HER-2/neu. DNA isolated from individual elements was assessed for EGFR and KIT activating mutations. All assessable cases were negative for estrogen receptor, progesterone receptor, and (except one) HER2. The majority were positive for cytokeratin 5/6 (58%), p63 (59%), and EGFR overexpression (66%); 24% were KIT positive. No EGFR or KIT activating mutations were present; 26% of the primary metaplastic breast carcinomas were fluorescence in situ hybridization-positive, displaying high EGFR copy number secondary to aneusomy (22%) and amplification (4%). We report here that metaplastic breast carcinoma is a basal-like breast cancer lacking EGFR and KIT activating mutations but exhibiting high EGFR copy number (primarily via aneusomy), suggesting that EGFR tyrosine kinase inhibitors should be evaluated in this molecular subset of breast carcinomas.
1-methyl-D-tryptophan (D-1MT) reverses the immunosuppressive effect of indoleamine 2,3-dioxygenase (IDO), and it is currently being developed both as a vaccine adjuvant and as an immunotherapeutic agent for combination with chemotherapy. The present study examined the pharmacokinetics and toxicity of D-1MT in preparation for clinical trials. Incubation of D-1MT in rat plasma for 24 h produced no significant degradation, with <15% of D-1MT being bound to plasma protein. Following oral administration, D-1MT exhibited a larger AUC and Vd, longer elimination t1/2, and slower clearance in rats than in dogs. When oral doses of D-1MT exceeded levels of 600 mg/m2/day in rats, or 1200 mg/m2/day in dogs, the Cmax and AUC values decreased, resulting in a corresponding decrease in oral bioavailability. Thus, the doses were indicative of the lowest saturating doses in dogs and rats corresponding with an elimination t1/2 of 6.0 h and 28.7 h, a Tmax of 1 h and 8 h, and a bioavailability of 47% and 92%, respectively. Tissue concentrations of D-1MT in mice were highest in the kidney, followed by the liver, muscle, heart, lung, and spleen, respectively; 48 h post dosing, D-1MT was excreted in the urine (35.1%) and feces (13.5%). Oral administration of D-1MT in rats from 150 to 3000 mg/m2/day (25 to 500 mg/kg/day) and in dogs from 600 to 1200 mg/m2/day (30 and 60 mg/kg/day) for 28 consecutive days did not lead to mortality, adverse events, histopathological lesions, or significant changes in hematology, clinical chemistry, and body weight. These results suggested that 3000 and 1200 mg/m2/day were the no-observed-adverse-effect levels in rats and dogs, respectively. Mean plasma concentrations of D-1MT (600 and 1200 mg/m2/day) in dogs 1 h post dosing were 54.4 and 69.5 μg/ml on Day 1, respectively, and 53.1 and 66.6 μg/ml on Day 28, respectively; thus, indicating no increase in plasma D-1MT with a change in dose. In conclusion, D-1MT has little toxicity when administered orally to rats and dogs. Exceeding the saturating dose of D-1MT is unlikely to cause systemic toxicity, since any further increase in D-1MT plasma levels would be minimal.
1-methyl-[D]-tryptophan; indoleamine 2,3-dioxygenase; pharmacokinetics; toxicity; saturating absorption
The aims of this trial were to assess the safety and efficacy of two different dosing schedules of irinotecan (CPT-11) in recurrent glioma patients, to assess irinotecan pharmacokinetics in patients on enzyme-inducing antiepileptic drugs (EIAEDs) and steroids, and to correlate with toxicity and response to treatment.
Sixty-four recurrent glioma patients were included in this study. Schedule A patients received irinotecan weekly (125 mg/m2/w) for four out of six weeks. Schedule B patients received irinotecan every three weeks at a dose of 300 mg/m2. A 20% dose reduction was implemented for patients who had received prior nitrosureas. Treatment was continued until unacceptable toxicity, tumor progression or patient withdrawal.
There was no difference in confirmed responses between the two groups (6.3%). PFS at 6 months was 6.25% (2/32 patients) on schedule A and 18.75% (6/32 patients) on schedule B but median OS (5.1 versus 5.5 months), and survival at one year (19%) was similar for both arms. The most common grade 3–4 toxicities on schedules A/B were: thrombocytopenia (15.6%/21.9%), diarrhea (6.3%/12.5%) and nausea and vomiting (0%/15.7%). One toxic death due to infection in the absence of neutropenia occurred in schedule B. EIAEDs reduced SN-38 and CPT-11 area under the curve and increased CPT-11 cleareance. This effect was more prominent in schedule A patients. Steroids did not alter CPT-11 pharmacokinetics in either schedule.
Single agent irinotecan has modest activity in patients with recurrent gliomas, independently of the administration schedule. Irinotecan administration on an every 3 week schedule resulted in longer PFS-6, at the expense of more toxicity. EIAEDs alter CPT-11 pharmacokinetics in this group of patients, and should be taken into consideration when determining optimal dosing.
Enzyme-inducing antiepileptic drugs; Dexamethasone; Irinotecan; Pharmacokinetics; Recurrent gliomas
The cyclooxygenase-2 (COX-2) enzyme appears to be an important target for cancer chemoprevention. Given the recent emergence of potentially serious cardiovascular toxicity associated with selective COX-2 inhibitors, nonsteroidal antiinflammatory drugs (NSAIDs), which inhibit both COX-1 and COX-2, have received renewed attention as candidate chemoprevention agents. Sulindac has demonstrated consistent chemopreventive potential in preclinical studies, as well as in a limited number of clinical trials reported to date. For the current pharmacokinetic study, sulindac capsules were prepared to facilitate ample agent supplies for future intervention studies. Encapsulation of the parent compound (sulindac sulfoxide) can be readily accomplished, but the effects of alternate formulations on bioavailability have not been rigorously examined. In the present single-dose, two-period crossover trial, we conducted pharmacokinetic analyses of sulindac in capsule (test) versus tablet (reference) formulations. Overall, bioavailability appeared to be higher for the capsule compared to the tablet formulation, based on test-to-reference pharmacokinetic parameter ratios for the parent compound. However, additional analyses based on the sulfide and sulfone metabolites of sulindac with the same pharmacokinetic parameters indicated similar chemopreventive exposures between the capsule and tablet formulations. These data support the use of sulindac capsules, which can be readily prepared with matching placebos, in future blinded chemoprevention trials.
Although agents that inhibit DNA synthesis are widely used in the treatment of cancer, the optimal method for combining such agents and the mechanism of their synergy is poorly understood. The present study examined the effects of combining gemcitabine and SN-38 (the active metabolite of irinotecan), two S phase-selective agents that individually have broad antitumor activity, in human cancer cells in vitro. Colony forming assays revealed that simultaneous treatment of Ovcar-5 ovarian cancer cells or BxPC-3 pancreatic cancer cells with gemcitabine and SN-38 resulted in antagonistic effects. In contrast, sequential treatment with the two agents in either order resulted in synergistic antiproliferative effects, although the mechanism of synergy varied with the sequence. In particular, SN-38 arrested cells in S phase, enhanced the accumulation of gemcitabine metabolites and diminished checkpoint kinase 1, thereby sensitizing cells in the SN-38 → gemcitabine sequence. Gemcitabine treatment followed by removal allowed prolonged progression through S phase, contributing to synergy of the gemcitabine → SN-38 sequence. Collectively, these results suggest that S phase selective agents might exhibit more cytotoxicity when administered sequentially rather than simultaneously.
Vorinostat (V) at levels >2.5 μM enhances chemotherapy in vitro. Yet the approved oral dose of 400 mg inconsistently achieves this level in patients. We developed an intermittent oral pulse-dose schedule of V to increase serum levels. We combined V with the cyclin dependent kinase inhibitor flavopiridol (F) which increases V-induced apoptosis.
One week before combination treatment, V alone was given daily for 3d (cycle −1). Then V was given on d1-3 and d8-10, and F on d2 and d9, every 21-d. Due to neutropenia, this was modified to V on d1-3 and d15–17, and F on d2 and d16, every 28-d. Bolus and split-dose F schedules were studied.
34 patients were treated. On the 21-d schedule, the maximum tolerated dose (MTD) was V 600 mg/d and F 60 mg/m2 bolus. On the 28-d schedule, the MTD was V 800 mg/d and F 30 mg/m2 over 30 min and 30 mg/m2 over 4 h. V Cmax at the 800 mg dose was 4.8 μM (± 2.8). V Cmax ≥2.5 μM was achieved in 86% of patients at the MTD. F increased the Cmax of V by 27% (95% CI 11%–43%). F Cmax of ≥2 μM was achieved in 90% of patients. 8 patients had stable disease for on average 5.5 m (range 1.6–13.2 m).
Intermittent high dose oral V in combination with F is feasible and achieves target serum levels >2.5 μM. V concentrations higher than previously reported with oral dosing were achieved.
CDKs and CDK inhibitors; Histone deacetylase inhibitors; Phase I trials; Combination chemotherapy; Pharmacokinetics
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.
We performed a nested case-control study in the context of the NSABP P-1 and P-2 prevention trials to determine the impact of CYP2D6 genotype, CYP2D6 inhibitor use, as well as metabolizer status (CYP2D6 genotype combined with CYP2D6 inhibitor use), on breast cancer events. Women who developed breast cancer (both non-invasive and invasive) while on five years of SERM therapy (cases) were matched to controls free of breast cancer. Comprehensive CYP2D6 genotyping was performed for alleles associated with absent (*3, *4, *5, *6), reduced (*10, *17, *41), and increased (*1XN and *2XN) enzyme activity. Information regarding the use of CYP2D6 inhibitors was recorded.
591 cases were matched to 1126 controls and DNA was genotyped in >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.
In the NSABP P1 and P2 clinical trials, alterations in CYP2D6 metabolism are not associated with either tamoxifen or raloxifene efficacy.
tamoxifen; breast cancer; prevention; CYP2D6; polymorphism
Metastatic carcinoma of unknown primary (CUP) has a very poor prognosis, and no standard first-line therapy currently exists. Here, we report the results of a phase II study utilizing a combination of gemcitabine and irinotecan as first-line therapy. Treatment was with gemcitabine 1000 mg/m2 and irinotecan 75 mg/m2 weekly times four on a six week cycle (Cohort I). Due to excessive toxicity, the dose and schedule were modified as follows: gemcitabine 750 mg/m2 and irinotecan 75 mg/m2 given weekly times three on a four week cycle (Cohort II). The primary endpoint was the confirmed response rate (CR + PR). Secondary endpoints consisted of adverse events based upon the presence or absence of the UDP glucuronosyltransferase 1 family, polypeptide A1*28 (UGT1A1*28) polymorphism, time to progression, and overall survival. Thirty-one patients were enrolled with a median age of 63 (range: 38–94), and 26 patients were evaluable for efficacy. Significant toxicity was observed in Cohort 1, characterized by 50% (7/14) patients experiencing a grade 4+ adverse event, but not in cohort II. The confirmed response rate including patients from both cohorts was 12% (95% CI: 2–30%), which did not meet the criteria for continued enrollment. Overall median survival was 7.2 months (95% CI: 4.0 to 11.6) for the entire cohort but notably longer in cohort II than in cohort I (9.3 months (95% CI: 4.1 to 12.1) versus 4.0 months (95% CI: 2.2 to 15.6)). Gemcitabine and irinotecan is not an active combination when used as first line therapy in patients with metastatic carcinoma of unknown primary. Efforts into developing novel diagnostic and therapeutic approaches remain important for improving the outlook for this heterogeneous group of patients.
SR13668, an orally active AKT pathway inhibitor, has demonstrated cancer chemopreventive potential in preclinical studies. To accelerate the clinical development of this promising agent, we designed and conducted the first-ever phase 0 chemoprevention trial to evaluate and compare the effects of food and formulation on SR13668 bioavailability.
Patients and Methods
Healthy adult volunteers were randomly assigned to receive a single, 38 mg oral dose of SR13668 in one of five different formulations, with or without food. Based on existing animal data, SR13668 in a PEG400/Labrasol® oral solution was defined as the reference formulation. Blood samples were obtained pre- and post-agent administration for pharmacokinetic analyses. Area under the plasma concentration-time curve (AUC0-∞) was defined as the primary endpoint. Data were analyzed and compared using established statistical methods for phase 0 trials with a limited sample size.
Participants (N=20) were rapidly accrued over a 5-month period. Complete pharmacokinetic data were available for 18 randomized participants. AUC0-∞ values were highest in the fed state (range = 122–439 ng/mL × hours) and were statistically significantly different across formulations (p = 0.007), with Solutol® HS15 providing the highest bioavailability. SR13668 time to peak plasma concentration (3 hours; range, 2 – 6 hours) and half-life were (11.2 ± 3.1 hours) were not formulation dependent.
Using a novel, highly efficient study design, we rapidly identified a lead formulation of SR13668 for further clinical testing. Our findings support application of the phase 0 trial paradigm to accelerate chemoprevention agent development.
Cytidine drugs, such as gemcitabine, undergo rapid catabolism and inactivation by cytidine deaminase (CD). 3,4,5,6-tetrahydrouridine (THU), a potent CD inhibitor, has been applied preclinically and clinically as a modulator of cytidine analogue metabolism. However, THU is only 20% orally bioavailable, which limits its preclinical evaluation and clinical use. Therefore, we characterized THU pharmacokinetics after the administration to mice of the more lipophilic pro-drug triacetyl-THU (taTHU).
Mice were dosed with 150 mg/kg taTHU i.v. or p.o. Plasma and urine THU concentrations were quantitated with a validated LC–MS/MS assay. Plasma and urine pharmacokinetic parameters were calculated non-compartmentally and compartmentally.
taTHU did not inhibit CD. THU, after 150 mg/kg taTHU i.v., had a 235-min terminal half-life and produced plasma THU concentrations >1 µg/mL, the concentration shown to inhibit CD, for 10 h. Renal excretion accounted for 40–55% of the i.v. taTHU dose, 6–12% of the p.o. taTHU dose. A two-compartment model of taTHU generating THU fitted the i.v. taTHU data best. taTHU, at 150 mg/kg p.o., produced a concentration versus time profile with a plateau of approximately 10 µg/mL from 0.5–2 h, followed by a decline with a 122-min half-life. Approximately 68% of i.v. taTHU is converted to THU. Approximately 30% of p.o. taTHU reaches the systemic circulation as THU.
The availability of THU after p.o. taTHU is 30%, when compared to the 20% achieved with p.o. THU. These data will support the clinical studies of taTHU.
Tetrahydrouridine; THU; Bioavailability; Metabolism; Mouse; Cytidine deaminase