Antitumor activity of Z-endoxifen in aromatase inhibitor-sensitive and aromatase inhibitor-resistant estrogen receptor-positive breast cancer.

BACKGROUND: The tamoxifen metabolite, Z-endoxifen, demonstrated promising antitumor activity in endocrine-resistant estrogen receptor-positive (ER+) breast cancer. We compared the antitumor activity of Z-endoxifen with tamoxifen and letrozole in the letrozole-sensitive MCF7 aromatase expressing model (MCF7AC1), as well as with tamoxifen, fulvestrant, exemestane, and exemestane plus everolimus in a letrozole-resistant MCF7 model (MCF7LR). METHODS: MCF7AC1 tumor-bearing mice were randomized to control (no drug), letrozole (10 µg/day), tamoxifen (500 µg/day), or Z-endoxifen (25 and 75 mg/kg). Treatment in the letrozole arm was continued until resistance developed. MCF7LR tumor-bearing mice were then randomized to Z-endoxifen (50 mg/kg) or tamoxifen for 4 weeks and tumors harvested for microarray and immunohistochemistry analysis. The antitumor activity of Z-endoxifen in the MCF7LR tumors was further compared in a second in vivo study with exemestane, exemestane plus everolimus, and fulvestrant. RESULTS: In the MCF7AC1 tumors, both Z-endoxifen doses were significantly superior to control and tamoxifen in reducing tumor volumes at 4 weeks. Additionally, the 75 mg/kg Z-endoxifen dose was additionally superior to letrozole. Prolonged letrozole exposure resulted in resistance at 25 weeks. In MCF7LR tumor-bearing mice, Z-endoxifen significantly reduced tumor volumes compared to tamoxifen, letrozole, and exemestane, with no significant differences compared to exemestane plus everolimus and fulvestrant. Additionally, compared to tamoxifen, Z-endoxifen markedly inhibited ERα target genes, Ki67 and Akt expression in vivo. CONCLUSION: In endocrine-sensitive and letrozole-resistant breast tumors, Z-endoxifen results in robust antitumor and antiestrogenic activity compared to tamoxifen and aromatase inhibitor monotherapy. These data support the ongoing development of Z-endoxifen.

Mouse pharmacokinetics and metabolism of the phenylurea thiocarbamate NSC 161128.

PURPOSE: NSC 161128, a phenylurea thiocarbamate, displays activity against the NCI60 anti-cancer cell line panel and xenograft models. The metabolite N-methyl-N'-phenylurea (M10) has been detected in animal plasma; however, detection and quantification of other putative NSC 161128 metabolites have not been undertaken. The purpose of this study was to characterize the pharmacokinetics and metabolism of NSC 161128 in mice and under in vitro conditions. METHODS: An LC-MS/MS assay was developed to evaluate stability and in vitro metabolism of NSC 161128 in liver microsomes and S9 fractions. Single-dose pharmacokinetic profiles for NSC 161128 and its metabolite M10 were obtained following intraperitoneal (I.P.) administration. RESULTS: A sensitive and specific positive ionization LC-MS/MS method for measuring NSC 161128 and its metabolites was developed. HPLC separation was achieved under gradient elution using an aqueous methanol mobile phase containing 0.05% formic acid and 0.05% ammonium hydroxide. The assay was linear over the range 1.0-1000 ng/mL. NSC 161128 was stable in aqueous solution and tissue culture media, but not in plasma, where rapid degradation of NSC 161128 to the metabolite M10 was observed. Following I.P. administration of a 200 mg/kg dose to male CD1 mice, the peak plasma concentration of NSC 161128 was 255 ng/mL after 5 min with a plasma half-life of 138 min. Potential bioactivation of NSC 161128 was explored using mouse S9. CONCLUSIONS: An analytical LC-MS/MS method was successfully developed for the detection and quantification of NSC 161128 and its metabolites. These results increase the understanding of NSC 161128 pharmacokinetic and metabolic properties.

Tuning pharmacokinetics and biodistribution of a targeted drug delivery system through incorporation of a passive targeting component.

Major challenges in the development of drug delivery systems (DDSs) have been the short half-life, poor bioavailability, insufficient accumulation and penetration of the DDSs into the tumor tissue. Understanding the pharmacokinetic (PK) parameters of the DDS is essential to overcome these challenges. Herein we investigate how surface chemistry affects the PK profile and organ distribution of a gold nanoparticle-based DDS containing both a passive and active targeting moiety via two common routes of administration: intravenous and intraperitoneal injections. Using LC/MS/MS, ELISA and INAA we report the half-life, peak plasma concentrations, area under the curve, ability to cross the peritoneal barrier and biodistribution of the nanoconjugates. The results highlight the design criteria for fine-tuning the PK parameters of a targeted drug delivery system that exploits the benefits of both active and passive targeting.

Inhibiting the growth of pancreatic adenocarcinoma in vitro and in vivo through targeted treatment with designer gold nanotherapeutics.

BACKGROUND: Pancreatic cancer is one of the deadliest of all human malignancies with limited options for therapy. Here, we report the development of an optimized targeted drug delivery system to inhibit advanced stage pancreatic tumor growth in an orthotopic mouse model. METHODPRINCIPAL FINDINGS: Targeting specificity in vitro was confirmed by preincubation of the pancreatic cancer cells with C225 as well as Nitrobenzylthioinosine (NBMPR - nucleoside transporter (NT) inhibitor). Upon nanoconjugation functional activity of gemcitabine was retained as tested using a thymidine incorporation assay. Significant stability of the nanoconjugates was maintained, with only 12% release of gemcitabine over a 24-hour period in mouse plasma. Finally, an in vivo study demonstrated the inhibition of tumor growth through targeted delivery of a low dose of gemcitabine in an orthotopic model of pancreatic cancer, mimicking an advanced stage of the disease. CONCLUSION: We demonstrated in this study that the gold nanoparticle-based therapeutic containing gemcitabine inhibited tumor growth in an advanced stage of the disease in an orthotopic model of pancreatic cancer. Future work would focus on understanding the pharmacokinetics and combining active targeting with passive targeting to further improve the therapeutic efficacy and increase survival.

Modulating pharmacokinetics, tumor uptake and biodistribution by engineered nanoparticles.

BACKGROUND: Inorganic nanoparticles provide promising tools for biomedical applications including detection, diagnosis and therapy. While surface properties such as charge are expected to play an important role in their in vivo behavior, very little is known how the surface chemistry of nanoparticles influences their pharmacokinetics, tumor uptake, and biodistribution. METHOD/PRINCIPAL FINDINGS: Using a family of structurally homologous nanoparticles we have investigated how pharmacological properties including tumor uptake and biodistribution are influenced by surface charge using neutral (TEGOH), zwitterionic (Tzwit), negative (TCOOH) and positive (TTMA) nanoparticles. Nanoparticles were injected into mice (normal and athymic) either in the tail vein or into the peritoneum. CONCLUSION: Neutral and zwitterionic nanoparticles demonstrated longer circulation time via both i.p. and i.v. administration, whereas negatively and positively charged nanoparticles possessed relatively short half-lives. These pharmacological characteristics were reflected on the tumor uptake and biodistribution of the respective nanoparticles, with enhanced tumor uptake by neutral and zwitterionic nanoparticles via passive targeting.

Phase 0 clinical chemoprevention trial of the Akt inhibitor SR13668.

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. 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. On the basis of 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 (AUC(0-∞)) 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. AUC(0-∞) 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.