Evaluation of the effect of naltrexone coadministration on the pharmacokinetics of oxycodone in a randomized phase 1 clinical trial
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OBJECTIVE: Oxycodone is a centrally acting µ-opioid agonist used as a strong analgesic. The opioid receptor antagonist -naltrexone is often coadministered to healthy subjects in clinical trials evaluating the pharmacokinetics (PK) of oxycodone to minimize its pharmacodynamic opioid effects. One objective of this relative bioavailability trial in healthy subjects was to investigate the effect of naltrexone on the PK of oxycodone. MATERIALS AND METHODS: A randomized, single-dose, parallel-group, within-groups crossover, clinical trial was conducted in 24 healthy subjects. 12 subjects were to receive a new oxycodone prolonged-release (PR) tablet (test) with naltrexone (T+) and without naltrexone (T) in the fasted state. Additionally, 12 subjects were to receive an Oxygesic PR tablet (reference) with naltrexone (R+) and without naltrexone (R) in the fasted state. Naltrexone was given orally 1.5 hours prior to each oxycodone administration. Pharmacokinetics, safety, and tolerability were assessed. RESULTS: The PK parameters of either oxycodone formulation were not changed with naltrexone administration under fasted conditions (point estimate T+/T (corresponding 90% confidence interval): Cmax: 103% (88 - 119%), AUC0-t: 97% (87 - 108%), AUC: 97% (88 - 108%); point estimate R+/R (corresponding 90% confidence interval): Cmax: 104% (97 - 112%), AUC0-t: 95% (88 - 102%), AUC: 94% (87 - 100%)). The safety and tolerability of both formulations was not qualitatively affected by naltrexone coadministration; however, treatment with naltrexone coadministration showed lower frequencies of adverse events. CONCLUSION: Oral naltrexone does not affect the PK of oral oxycodone under fasted conditions. A naltrexone block can be applied in oxycodone PK trials to minimize adverse opioid effects.

Assessment of the Abuse Potential of Cebranopadol in Nondependent Recreational Opioid Users: A Phase 1 Randomized Controlled Study.

BACKGROUND: Cebranopadol is a nociceptin/orphanin FQ peptide/opioid receptor agonist with central antinociceptive activity. We hypothesize that this novel mechanism of action may lead to a lower risk of abuse compared with pure µ-opioid peptide receptor agonists. METHODS: We conducted a single-dose, nested-randomized, double-blind crossover study in nondependent recreational opioid users to evaluate the abuse potential of single doses of cebranopadol relative to hydromorphone immediate release and placebo. The study consisted of a qualification phase and a 7-period treatment phase (cebranopadol 200, 400, and 800 µg; hydromorphone 8 and 16 mg; and 2 placebos). The primary end point was the peak effect of drug liking at this moment, measured by visual analog scale (VAS). Various secondary end points (eg, VAS rating for good drug effects, high, bad drug effects, take drug again, drug similarity, and pupillometry) were also investigated. RESULTS: Forty-two subjects completed the study. Cebranopadol 200 and 400 µg did not differentiate from placebo on the abuse potential assessments and generated smaller responses than hydromorphone. Responses observed with cebranopadol 800 µg were similar to hydromorphone 8 mg and smaller than hydromorphone 16 mg. The maximum effect for VAS drug liking at this moment was delayed compared with hydromorphone (3 and 1.5 hours, respectively). Cebranopadol administration was safe; no serious adverse events or study discontinuation due to treatment-emergent adverse events occurred. CONCLUSIONS: These results confirm our hypothesis that cebranopadol, a nociceptin/orphanin FQ peptide/opioid receptor agonist, has lower abuse potential than hydromorphone immediate release, a pure µ-opioid peptide agonist.

Correction to: Clinical Pharmacokinetic Characteristics of Cebranopadol, a Novel First-in-Class Analgesic.

For each simulation, PK profiles from 1000 subjects were simulated based on a titration scheme.

Clinical Pharmacokinetic Characteristics of Cebranopadol, a Novel First-in-Class Analgesic.

BACKGROUND AND OBJECTIVES: Cebranopadol is a novel first-in-class analgesic acting as a nociceptin/orphanin FQ peptide and opioid peptide receptor agonist with central analgesic activity. It is currently in clinical development for the treatment of chronic pain conditions. This trial focuses on the clinical pharmacokinetic (PK) properties of cebranopadol after oral single- and multiple-dose administration. METHODS: The basic PK properties of cebranopadol were assessed by means of noncompartmental methods in six phase I clinical trials in healthy subjects and patients. A population PK analysis included two further phase I and six phase II clinical trials. RESULTS: After oral administration of the immediate-release (IR) formulation, cebranopadol is characterized by a late time to reach maximum plasma concentration [C max] (4-6 h), a long half-value duration [HVD] (14-15 h), and a terminal phase half-life in the range of 62-96 h. After multiple once-daily dosing in patients, an operational half-life (the dosing interval resulting in an accumulation factor [AF] of 2) of 24 h was found to be the relevant factor to describe the multiple-dose PKs of cebranopadol. The time to reach steady state was approximately 2 weeks, the AF was approximately 2, and peak-trough fluctuation (PTF) was low (70-80%). Dose proportionality at steady state was shown for a broad dose range of cebranopadol 200-1600 µg. A two-compartment disposition model with two lagged transition compartments and a first-order elimination process best describes cebranopadol data in healthy subjects and patients after single- and multiple-dose administration. CONCLUSIONS: Cebranopadol formulated as an IR product can be used as a once-daily formulation; it reaches C max after only 4-6 h, and has a long HVD and a low PTF. Therefore, from a PK perspective, cebranopadol is an attractive treatment option for patients with chronic pain.

Efficient telomerase inhibition in human non-small cell lung cancer cells by liposomal delivery of 2'-O-methyl-RNA.

The antisense oligonucleotide 2'-O-methyl-RNA is a selective telomerase inhibitor targeting the telomerase RNA component and represents a potential candidate for anticancer therapy. The poor cellular uptake of 2'-O-methyl-RNA is a limiting factor that may contribute to the lack of functional efficacy. To improve delivery of 2'-O-methyl-RNA and consequently antitumoral efficiency in human lung cancer cells, we have investigated several transfection reagents. The transfection reagents DOTAP, MegaFectin 60, SuperFect, FuGENE 6 and MATra-A were tested for intracellular delivery. A FAM-labeled 2'-O-methyl-RNA was used to assess the intracellular distribution by confocal laser scanning microscopy in A549 human non-small cell lung cancer cells. Telomerase activity was measured using the telomeric repeat amplification protocol. Cell viability after transfection was quantified by the MTT assay. All transfection reagents enhanced 2'-O-methyl-RNA uptake in A549 cells but the cationic lipid reagents DOTAP and MegaFectin 60 were most efficient in the delivery of 2'-O-methyl-RNA resulting in telomerase inhibition. Among both DOTAP exhibited the lowest cytotoxicity. Our experiments show that DOTAP is the most suitable transfection reagent for the delivery of 2'-O-methyl-RNA in human lung cancer cells according to its relatively low cytotoxicity and its ability to promote efficient uptake leading to the inhibition of telomerase.

Screening of telomerase inhibitors.

Shortening of telomeres prevents cells from uncontrolled proliferation. Progressive telomere shortening occurs at each cell division until a critical telomeric length is reached. Telomerase expression is switched off after embryonic differentiation in most normal cells, but it is expressed in a very high percentage of tumors of different origin. Thus, telomerase is regarded as the best tumor marker and a promising novel molecular target for cancer treatment. Therefore, different strategies to inhibit telomerase have been developed. However, systematic screening of telomerase inhibitors has not been performed to compare their therapeutic potential. We propose a suitable strategy for estimation of the therapeutic potential of telomerase inhibitors, which is based on a systematic screening of different inhibitors in the same cell system. From the long list of compounds discussed in the literature, we have selected four telomerase inhibitors of different structure and mode of action: BRACO19 (G-quadruplex-interactive compound), BIBR1532 (non-nucleosidic reverse transcriptase inhibitor), 2'-O-methyl RNA, and peptide nucleic acids (PNAs; hTR antisense oligonucleotides). To determine minimal effective concentrations for telomerase inhibition, telomerase activity was measured using the cell-free telomerase repeat amplification protocol (TRAP) assay. We also tested inhibitors in long-term cell-culture experiments by exposing A-549 cells to non-cytotoxic concentrations of inhibitors for a period of 99 days. Subsequently, telomerase activity of A-549 cells was investigated using the TRAP assay, and telomere length of samples was assessed by telomere restriction fragment (TRF) Southern blot analysis.

Optimization of the TRAP assay to evaluate specificity of telomerase inhibitors.

Telomerase inhibition represents a promising approach to anticancer treatment. In order to clarify the therapeutic potential of telomerase inhibitors we examined different substances (small molecule compounds BIBR1532 and BRACO19, as well as hTR antisense oligonucleotides 2'-O-methyl RNA and PNA) in A-549, MCF-7, and Calu-3 cell lines in a cell-free TRAP assay. We demonstrated that each of the tested agents inhibited telomerase in all used cell lines and that the antisense oligonucleotides represent the most potent inhibitors. Interestingly, upon evaluating the specificity of telomerase inhibitors we found out that not all agents acted specifically against telomerase. We observed that BRACO19 and PNA had an inhibitory effect also on PCR amplification of the TSR8 oligonucleotide which is provided in the TRAP(EZE) kit as a PCR control. By modifying the experimental protocol and using a different reverse primer we were able to enhance PNA selectivity, although the PCR inhibition of the TSR8 control template by BRACO19 could not be prevented. We propose an explanation for the lack of target specificity and suggest caution when testing putative telomerase inhibitors, as it appears that some of those substances may not affect specifically telomerase or telomeric G-rich sequences and thus can lead to the misinterpretation of experimental results.

Tumorigenic conversion of endothelial cells.

Tumors of endothelial origin develop rarely. Until now, only two angiosarcoma (AS)-derived endothelial cell lines have been be isolated, ISO-HAS and AS-M. Both AS-derived endothelial cell lines presented the typical endothelial characteristics, such as the expression of CD31 and von Willebrand factor, but differed from normal endothelial cells in a nuclear expression of p53, in a delayed angiogenic reaction, and a reduced expression of caveolin. In addition, differences in the expression of cytokines and cell adhesion molecules responsive to proinflammatory stimuli were observed. While AS-M showed an expression pattern similar to that of human umbilical vein endothelial cells (HUVEC), ISO-HAS clearly differed from primary endothelial cells by a constitutive expression of E-selection, granulocyte macrophage colony-stimulating factor, and vascular endothelial cell adhesion molecule-1. Even though the telomeres of both AS-derived established cell lines were longer than telomeres of freshly isolated HUVEC, neither transcripts encoding telomerase nor telomerase activity were detected, suggesting that the tumor cells of endothelial origin may use a telomerase-independent mechanism for maintaining the telomere length. This observation has implications for development of therapeutic approaches for angiosarcoma.

Telomerase activity in cell lines of pediatric soft tissue sarcomas.

Telomeres and their maintenance by telomerase have been implicated to play an important role in carcinogenesis. As almost all malignant tumors express telomerase (in contrast to normal somatic cells), assessment of its activity has been proposed as a diagnostic and prognostic tool. To test the prognostic value of telomerase in pediatric soft tissue sarcoma (STS), we analyzed telomere length (by telomere restriction fragment analysis), telomerase activity (by modified telomerase repeat amplification protocol assay), and expression of human telomerase reverse transcriptase (hTERT) mRNA (by TaqMan technique) in cell lines of different types of STS from 12 children and adolescents. Telomere length (3.7-9.0 kb) showed a very heterogeneous pattern, independent of subtype of STS or the age of the patients, and it was not associated with expression of hTERT mRNA. In contrast, there was a trend of an association between hTERT and telomerase activity. The three tested cell lines of embryonal rhabdomyosarcomas demonstrated no or low (n = 2) telomerase activity, which was confirmed in two cases by a very low expression of hTERT mRNA. Thus, we suggest that the significant difference (p < 0.01) in the less aggressive clinical behavior of embryonal rhabdomyosarcomas in comparison to other subtypes may be due to differences in telomerase expression. Taken together, our cell line experiments imply that telomerase activity might be a biologic marker for stratification between STS with different clinical prognosis.

Telomerase activity in chronic inflammatory bowel disease.

Patients with ulcerative colitis have an increased risk of developing colorectal cancer. Telomerase appears to be associated with cellular immortality and might serve as a diagnostic and prognostic marker in carcinogenesis. To test this hypothesis we measured telomerase by a score from 0 (no activity) to 4 (very high activity) in specimens obtained surgically from seven patients with adenocarcinoma of the colon. Intraindividual comparison was made among normal tissue (mean score +/- SD: 0.7 +/- 1.0), tissues adjacent to the tumor (2.7 +/- 0.8), and the tumor center (3.0 +/- 1.0). In addition, from 18 patients with ulcerative colitis, 10 patients with Crohn's disease, and 14 patients without chronic inflammatory bowel disease, biopsies were collected from normal and inflamed areas of the colon. Independent of the duration (0-32 years), grade, and location of the diseases, the telomerase activities were comparable, ranging from 0.4 to 1.0 in ulcerative colitis and from 0.3 to 0.6 in Crohn's disease and averaging 0.4 in controls. Apparently low telomerase activities are present in the mucosa of all patients and the enzyme is not yet upregulated in the potentially premalignant state of active ulcerative colitis, dismissing its prognostic value as an early tumor marker for this disorder.