Mass Balance and Metabolic Pathways of Eliapixant, a P2X3 Receptor Antagonist, in Healthy Male Volunteers.

BACKGROUND: Overactive adenosine triphosphate signaling via P2X3 homotrimeric receptors is implicated in multiple conditions. To fully understand the metabolism and elimination pathways of eliapixant, a study was conducted to assess the pharmacokinetics, mass balance, and routes of excretion of a single oral dose of the selective P2X3 receptor antagonist eliapixant, in addition to an in vitro characterization. METHODS: In this single-center open-label non-randomized non-placebo-controlled phase I study, healthy male subjects (n = 6) received a single dose of 50 mg eliapixant blended with 3.7 MBq [14C]eliapixant as a PEG 400-based oral solution. Total radioactivity and metabolites excreted in urine and feces, and pharmacokinetics of total radioactivity, eliapixant, and metabolites in plasma were assessed via liquid scintillation counting and high-performance liquid chromatography-based methods coupled to radiometric and mass spectrometric detection. Metabolite profiles of eliapixant in human in vitro systems and metabolizing enzymes were also investigated. RESULTS: After administration as an oral solution, eliapixant was rapidly absorbed, reaching maximum plasma concentrations within 2 h. Eliapixant was eliminated from plasma with a mean terminal half-life of 48.3 h. Unchanged eliapixant was the predominant component in plasma (72.6% of total radioactivity area under the curve). The remaining percentage of drug-related components in plasma probably represented the sum of many metabolites, detected in trace amounts. Mean recovery of total radioactivity was 97.9% of the administered dose (94.3-99.4%) within 14 days, with 86.3% (84.8-88.1%) excreted via feces and 11.6% (9.5-13.1%) via urine. Excretion of parent drug was minimal in feces (0.7% of dose) and urine (≈ 0.5%). In feces, metabolites formed by oxidation represented > 90% of excreted total radioactivity. The metabolites detected in the in vitro experiments were similar to those identified in vivo. CONCLUSION: Complete recovery of administered eliapixant-related radioactivity was observed in healthy male subjects with predominant excretion via feces. Eliapixant was almost exclusively cleared by oxidative biotransformation (> 90% of dose), with major involvement of cytochrome P450 3A4. Excretion of parent drug was of minor importance (~ 1% of dose). CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov: NCT04487431 (registered 27 July 2020)/EudraCT number: 2020-000519-54 (registered 3 February 2020), NCT02817100 (registered 26 June 2016), NCT03310645 (registered 16 October 2017).

Eliapixant is a drug that acts on structures in the body called P2X3 receptors that are involved in several conditions, including chronic cough, overactive bladder, and endometriosis-related pain. When evaluating a new drug, it is important to know how it is being removed from the body by natural mechanisms. We performed a study in which six healthy male volunteers took a single dose of eliapixant, and we investigated what happened to the drug after it was taken. We measured the amount of eliapixant in the volunteers' blood, urine, and feces, and also measured the compounds formed when eliapixant was broken down naturally by the body ("metabolites"). We also used human cells in the laboratory to investigate how the different metabolites of eliapixant are formed. Almost three-quarters of eliapixant in the blood had not been broken down at all, while the remaining one-quarter had been converted into many different metabolites. A total of 2 weeks after taking eliapixant, almost all of it had been converted to metabolites and eliminated from the body (mostly in feces, but also a small amount in urine). The most important organ for breaking down eliapixant is the liver. The information from this study will help doctors determine whether eliapixant is likely to interfere with other drugs taken simultaneously, and whether patients with liver or kidney problems might take longer than healthy people to remove it from their bodies.

Assessment of the safe and efficacious dose of the selective progesterone receptor modulator vilaprisan for the treatment of patients with uterine fibroids by exposure-response modelling and simulation.

AIMS: We report population pharmacokinetic (popPK) and exposure-response (E-R) analyses for efficacy (induced amenorrhoea [IA]) and safety (unbound oestradiol [E2] concentrations) of the selective progesterone receptor modulator vilaprisan. Results were used to inform the dose for the Phase 3 programme in patients with uterine fibroids. METHODS: A popPK model was developed using data from Phase 1 and 2 studies (including ASTEROID 1 and 2). The relationship between vilaprisan exposure (steady-state AUC) and IA after oral administration of 0.5, 1, 2 or 4 mg/day over 3 months was analysed in ASTEROID 1 using logistic regression and qualified in ASTEROID 2 by comparing simulated and observed probability for IA after 2 mg/day. The exposure-E2 relationship was analysed visually. RESULTS: Vilaprisan clearance was 22.7% lower in obese vs non-obese patients. The E-R relationship for IA in ASTEROID 1 was steep and consistent with ASTEROID 2, with a maximum probability (Pmax ) of 59% (95% CI: 49-68%). The exposure at which 50% of Pmax is obtained was 36.9 µg*h/L (95% CI: 27.7-48.7 µg*h/L). Simulations showed that 36% of the patients will be below 90% of Pmax for IA after 1 mg/day compared to 2% after 2 mg/day. E2 levels tended to decrease with increasing exposure. While E2 levels remained largely within the physiologic follicular phase range, the clinical relevance of this decrease will be evaluated in long-term studies. CONCLUSIONS: A 2 mg/day dose was selected for Phase 3 as E-R analyses show this dose results in a close to maximum probability for IA, without any safety concerns noted.

Clinical Pharmacokinetics and Pharmacodynamics of the Selective Progesterone Receptor Modulator Vilaprisan: A Comprehensive Overview.

Vilaprisan is a highly potent selective progesterone receptor modulator in development for the treatment of symptomatic uterine fibroids and endometriosis. Its pharmacokinetics are characterized by rapid absorption, almost complete bioavailability, and dose-proportional exposure. The intrinsic factors of age, bodyweight, and race have no clinically relevant effect on the pharmacokinetics and pharmacodynamics of vilaprisan and do not warrant a dose adjustment. Similarly, vilaprisan can be used in patients with mild or moderate renal or hepatic impairment without dose adjustment, but its use is not recommended in patients with severe organ impairment. Vilaprisan has no perpetrator potential on cytochrome P450 (CYP) enzymes or transporters and therefore restrictions in the concomitant use of their substrates are not required. Nonetheless, because it is a sensitive CYP3A4 substrate itself, concomitant use of vilaprisan with strong CYP3A inhibitors or inducers is not recommended. However, there is no risk for QTc prolongation when vilaprisan and a strong CYP3A inhibitor are administered concomitantly, as indicated by a vilaprisan concentration-QTc response analysis across all studies with triplicate electrocardiogram measurements. Furthermore, due to its mode of action, vilaprisan is also not recommended to be used together with progestin-containing oral contraceptives. Vilaprisan shows a steep exposure-response relationship for inducing amenorrhea in patients with uterine fibroids experiencing heavy menstrual bleeding. Based on simulations, a dose of 2 mg/day is expected to induce a maximum bleeding reduction and was thus selected for phase III.

Pharmacokinetics and Safety of the Selective Progesterone Receptor Modulator Vilaprisan in Chinese Healthy Postmenopausal Women.

Vilaprisan is a novel selective progesterone receptor modulator for the long-term treatment of uterine fibroids and endometriosis. This study investigated the pharmacokinetics, safety, and tolerability of vilaprisan in healthy Chinese postmenopausal women. Twelve participants received multiple doses of vilaprisan once daily over 14 days as a 2-mg tablet. Plasma vilaprisan concentrations were determined using liquid chromatography-tandem mass spectrometry. The main pharmacokinetic parameters of vilaprisan were assessed with noncompartmental analysis, including maximum observed concentration (Cmax ), systemic exposure (area under the plasma concentration-time curve), time to reach Cmax and terminal half-life. Safety assessments include the documentation of adverse events, measurement of clinical/anthropometric parameters and vital signs, electrocardiogram, and physical and gynecologic examination. The participants had a mean age of 53.3 (± 4.2) years and a body mass index of 23.8 ± 2.8 kg/m2 . Median time to reach Cmax was 1.5 hours after both single and multiple vilaprisan administration. Mean Cmax values obtained after multiple dosing (23.3 µg/L [standard deviation (SD) = 6.73]) were 1.92-fold (SD = 0.554) higher compared to single dosing (12.5 µg/L [SD = 3.04]). Mean area under the plasma concentration-time curve in the dosing interval increased with an accumulation factor of 2.98 (SD = 0.767) between single (91.3 µg · h/L [SD = 20.4]) and multiple dosing (276 µg · h/L [SD = 109]). The mean terminal half-life of vilaprisan was 44.5 hours (SD = 10.3) after multiple dosing. Mild to moderate adverse events were observed similar to previous studies. Overall, daily oral administration of the therapeutic dose of 2 mg of vilaprisan over 14 days was safe and well tolerated by all participants.

The effects of vilaprisan on the pharmacodynamics and pharmacokinetics of a combined oral contraceptive-A randomized controlled trial.

AIMS: The primary objective was to explore whether the suppression of ovarian activity induced by a combined oral contraceptive (COC) is influenced by the simultaneous intake of the selective progesterone receptor modulator (SPRM) vilaprisan (VPR). METHODS: In this exploratory randomized, double-blind, parallel-group study, 71 healthy premenopausal women were randomized (1:1) to receive either 2 mg/d VPR or placebo for 3 months. Concomitantly, a COC (0.15 mg levonorgestrel, 0.03 mg ethinyloestradiol) was administered in a cyclic regimen. Ovarian activity (Hoogland score based on follicle size and hormone concentrations), cervical function (Insler score), bleeding pattern and endometrial thickness/histology were assessed before treatment, in treatment cycle 3 and during follow-up. RESULTS: The known COC-driven suppression of ovarian activity was mildly affected by VPR. COC+VPR group: 22, 0 and 6% of the subjects had Hoogland scores of 4 (active follicle-like structures), 5 or 6 (ovulation). COC+placebo group: 14% of the subjects had a score of 4 and none a score of 5 or 6 (Bayesian analysis for Hoogland score = 4, median difference in response rate: 7.5%; 90% credible interval [-8.5; 23.5%]). COC effects on cervical function were moderately affected (mucus more sperm permeable under COC+VPR). COC withdrawal bleeding, in contrast, was absent in 81% of the subjects receiving COC+VPR vs 0% receiving COC+placebo. CONCLUSION: The SPRM VPR interfered with the pharmacodynamic effects of the COC. Therefore, full contraceptive effectiveness cannot be assumed without final judgement by a Pearl index study. Women on SPRMs should be advised to use nonhormonal contraception methods.

Discovery of Vilaprisan (BAY 1002670): A Highly Potent and Selective Progesterone Receptor Modulator Optimized for Gynecologic Therapies.

Progesterone plays an important role in the female reproductive system. However, there is also evidence that gynecologic disorders/diseases such as uterine fibroids and endometriosis are progesterone-dependent. Steroidal and non-steroidal selective progesterone receptor modulators (SPRMs) have shown potential for the treatment of such diseases. Steroidal SPRMs, including mifepristone and ulipristal acetate, have proven effective in clinical trials. However, several steroidal SPRMs containing a dimethylamino substituent have been associated with elevated liver enzymes in patients. An earlier drug discovery program identified lonaprisan as a highly selective SPRM that did not show drug-related change in liver enzyme activity. Building on data obtained from that work, here we describe the research program that culminated in the discovery of a novel steroidal SPRM, vilaprisan, which combines an extremely high potency with very favorable drug metabolism and pharmacokinetic properties. Vilaprisan has entered clinical development and is currently undergoing phase 3 clinical trials.

CYP3A4-mediated effects of rifampicin on the pharmacokinetics of vilaprisan and its UGT1A1-mediated effects on bilirubin glucuronidation in humans.

AIMS: The primary aim of the present study was to quantify the effects of rifampicin, a strong cytochrome P450 (CYP) 3A4 inducer, on the pharmacokinetics of the new selective progesterone receptor modulator, vilaprisan. In addition, the effects of rifampicin on the glucuronidation of bilirubin, an endogenous UDP-glucuronosyltransferase family 1 member A1 (UGT1A1) substrate, were explored. METHODS: This was an open-label, two-period study in 12 healthy postmenopausal women. Subjects received a single oral dose of vilaprisan 4 mg in each period. In period 2, administration of vilaprisan was preceded and followed by rifampicin 600 mg day-1 . A subtherapeutic dose of midazolam (1 mg) was coadministered with vilaprisan to monitor CYP3A4 induction. Details of the administration and sampling schedule were optimized by means of a physiologically based pharmacokinetic model. Plasma concentrations of vilaprisan, midazolam, and 1'- hydroxy-midazolam were measured and rifampicin-associated changes in the glucuronidation of bilirubin were determined. RESULTS: As predicted by our model, the coadministration of rifampicin was associated with a substantial decrease in exposure to vilaprisan and midazolam - indicated by the following point estimates (90% confidence intervals) for the area under the plasma concentration-time curve from zero to the time of the last quantifiable concentration ratio with or without rifampicin: 0.040 (0.0325, 0.0505) for vilaprisan and 0.144 (0.117, 0.178) for midazolam. Further, it was associated with an increase in bilirubin glucuronidation, indicating that UGT1A1 was induced. CONCLUSIONS: The exposure to vilaprisan was reduced by 96%. Such a reduction is likely to render the drug therapeutically ineffective. Therefore, it is recommended that the use of strong CYP3A4 inducers is avoided when taking vilaprisan.

Effect of the Novel Selective Progesterone Receptor Modulator Vilaprisan on Ovarian Activity in Healthy Women.

This randomized, double-blind, parallel-group study in healthy young women investigated the effect of treatment with vilaprisan (0.5, 1, 2, or 4 mg/day for 12 weeks) on ovarian function by assessing the Hoogland score, which is based on the size of follicle-like structures as determined by transvaginal ultrasound and on estradiol and progesterone serum concentrations. Ovulation inhibition (ie, Hoogland score <6 in treatment weeks 1-4 and 8-12) was observed in >80% of the subjects receiving vilaprisan ≥1 mg/day. The effect was dose dependent. With a Bayesian approach, the percentage of subjects with ovulation inhibition was estimated to increase from 37% in subjects receiving 0.5 mg/day vilaprisan to 76%, 86%, and 88% in subjects receiving 1, 2, and 4 mg/day, respectively. Follicle growth was not suppressed during treatment. The majority of subjects receiving ≥1 mg/day had a Hoogland score of 4 (active follicle-like structures, ie, follicle diameter >13 mm, estradiol >27.2 pg/mL, no progesterone increase) both at beginning and end of treatment. Mean average estradiol as well as mean maximum progesterone concentrations were noticeably decreased during treatment with vilaprisan ≥1 mg/day compared to pretreatment, but estradiol concentrations remained >80 pg/mL. Both hormones returned to pretreatment levels after the end of treatment, indicating a rapid resumption of normal ovarian activity. Amenorrhea occurred in the majority of subjects during treatment at dosages ≥1 mg/day. The adverse events observed in this study confirm the known safety profile of vilaprisan. All in all, the results of this study support the development of vilaprisan for the long-term treatment of uterine fibroids.

Pharmacokinetics and safety of the selective progesterone receptor modulator vilaprisan in healthy postmenopausal women
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OBJECTIVES: Vilaprisan is a novel, potent, and highly selective progesterone receptor modulator, which might offer a promising option for the treatment of uterine fibroids. METHODS AND MATERIALS: In this randomized, placebo-controlled, parallel-group phase 1 study, the pharmacokinetics and safety of vilaprisan were investigated in healthy postmenopausal women. Subjects received a single oral dose of vilaprisan (1, 5, 15, or 30 mg) or placebo and - after a wash-out period - daily doses of the same strength over 28 days. Safety assessments included vital signs, ECGs, clinical laboratory tests, and adverse events. Blood samples for pharmacokinetic (PK) profiles were collected over 14 days after single dose (sd) and multiple dose (md; day 28). RESULTS: Vilaprisan was well tolerated. Mild to moderate adverse events occurred with similar frequency at all dose levels. Following single dose, maximum vilaprisan concentrations were observed 1 - 2 hours post-dose. Terminal half-lives ranged from 31 to 38 hours. Maximum concentrations of vilaprisan (Cmax) and exposure to vilaprisan (AUC) increased roughly dose-proportionally from 3.74 µg/L (1 mg) to 68.6 µg/L (30 mg) and 58.5 µg×h/L to 1,590 µg×h/L, respectively. With daily dosing, accumulation consistent with the long terminal half-life was observed (AUC(0-24)md/AUC(0-24)sd ratios: 1.9 to 3.2). The ratio AUC(0-24)md/AUCsd increased with dose from ~ 1 (1 mg) to 1.5 (30 mg). CONCLUSIONS: Exposure to vilaprisan increased roughly dose-proportionally in the dose range studied and accumulated after multiple dosing as expected based on t1/2, indicating linear pharmacokinetics of vilaprisan in the expected therapeutic dose range.
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Model-Based Dose Selection for Intravaginal Ring Formulations Releasing Anastrozole and Levonorgestrel Intended for the Treatment of Endometriosis Symptoms.

Pharmacokinetics (PK) of anastrozole (ATZ) and levonorgestrel (LNG) released from an intravaginal ring (IVR) intended to treat endometriosis symptoms were characterized, and the exposure-response relationship focusing on the development of large ovarian follicle-like structures was investigated by modeling and simulation to support dose selection for further studies. A population PK analysis and simulations were performed for ATZ and LNG based on clinical phase 1 study data from 66 healthy women. A PK/PD model was developed to predict the probability of a maximum follicle size ≥30 mm and the potential contribution of ATZ beside the known LNG effects. Population PK models for ATZ and LNG were established where the interaction of LNG with sex hormone-binding globulin (SHBG) as well as a stimulating effect of estradiol on SHBG were considered. Furthermore, simulations showed that doses of 40 µg/d LNG combined with 300, 600, or 1050 µg/d ATZ reached anticipated exposure levels for both drugs, facilitating selection of ATZ and LNG doses in the phase 2 dose-finding study. The main driver for the effect on maximum follicle size appears to be unbound LNG exposure. A 50% probability of maximum follicle size ≥30 mm was estimated for 40 µg/d LNG based on the exposure-response analysis. ATZ in the dose range investigated does not increase the risk for ovarian cysts as occurs with LNG at a dose that does not inhibit ovulation.

Pharmacodynamics and safety of the novel selective progesterone receptor modulator vilaprisan: a double-blind, randomized, placebo-controlled phase 1 trial in healthy women.

STUDY QUESTION: Does administration of vilaprisan (VPR) to healthy women for 12 weeks reduce menstrual bleeding? SUMMARY ANSWER: In this 12-week proof-of-concept phase 1 trial, most women (30/33, 90%) who received VPR at daily doses of 1-5 mg reported the absence of menstrual bleeding. WHAT IS KNOWN ALREADY: Vilaprisan (BAY 1002670) is a novel, highly potent selective progesterone receptor modulator that markedly reduces the growth of human leiomyoma tissue in a preclinical model of uterine fibroids (UFs). STUDY DESIGN, SIZE, DURATION: In this double-blind, parallel-group study, of the 163 healthy women enrolled 73 were randomized to daily VPR 0.1 mg (n = 12), 0.5 mg (n = 12), 1 mg (n = 13), 2 mg (n = 12), 5 mg (n = 12) or placebo tablets (n = 12) for 12 weeks. Participants were followed up until the start of the second menstrual bleeding after the end of treatment. Trial simulations were used to determine the minimum sample size required to estimate the non-bleeding rate (i.e. self-assessed bleeding intensity of 'none' or 'spotting') using Bayesian dose-response estimation with incorporated prior information. It was estimated that 48 participants in the per-protocol analysis population would be sufficient. PARTICIPANTS/MATERIALS, SETTING, METHODS: Women aged 18-45 years who had been sterilized by tubal ligation were enrolled between November 2011 and May 2012. Participants kept a daily diary of bleeding intensity. Blood and urine samples were taken, and transvaginal ultrasound was performed before treatment, during treatment and follow-up. Endometrial biopsies were obtained during the pretreatment cycle, at the end of the treatment period and during the follow-up phase. The primary outcome was the estimated dose-response curve of the observed non-bleeding rate during Days 10-84 of treatment, excluding the endometrial biopsy day and 2 days after biopsy. Secondary outcomes included return of bleeding during follow-up, size of follicle-like structures and serum hormone levels. Safety assessments included adverse events (AEs), endometrial thickness and histology, laboratory parameters, vital signs and 12-lead electrocardiography. MAIN RESULTS AND THE ROLE OF CHANCE: All 73 randomized participants received at least one dose of study medication and were included in safety analyses; six participants were excluded from the per-protocol analyses. A total of 69 completed the study. Observed non-bleeding rates increased with VPR dose: 0.1 mg (0%; 90% confidence interval [CI]: 0-23.8), 0.5 mg (27.3%; 90% CI: 7.9-56.4), 1 mg (80.0%; 90% CI: 49.3-96.3), 2 mg (100%; 90% CI: 77.9-100), 5 mg (90.9%; 90% CI: 63.6-99.5), compared with 0% (90% CI: 0-22.1) in the placebo group. Maximal non-bleeding rates were reached at doses of 2 mg and higher. Return of menstrual bleeding was observed in all women ≤52 days after VPR discontinuation. No treatment-emergent critical endometrial findings occurred. Follicular growth was not suppressed and minimum average estradiol levels remained above 40 pg/ml. No serious treatment-emergent AEs or study discontinuations due to AEs were reported. Clinically relevant changes in laboratory parameters or vital signs were not evident. LIMITATIONS, REASONS FOR CAUTION: The results of this small proof-of-concept study will need to be confirmed in larger trials in patients with UFs to establish the potential therapeutic benefits and safety of VPR. WIDER IMPLICATIONS OF THE FINDINGS: The high rates of non-bleeding (80-100% at VPR doses of 1-5 mg) support further evaluation of VPR in patients with UFs and heavy menstrual bleeding. STUDY FUNDING/COMPETING INTERESTS: This study was funded by Bayer Pharma AG. B.S., A.K., M.-H.S.M., C.S. and B.R. are employees of Bayer Pharma AG. B.S., A.K. and M.-H.S.M. are listed as inventors of an issued patent related to this work, and received payment for this from Bayer Pharma AG. D.B. is the founder of Biokinetic Europe Ltd, UK, which received funding for this study from Bayer Pharma AG. M.K. is an employee of Nuvisan GmbH, Germany, which received funding for this study from Bayer Pharma AG. TRIAL REGISTRATION NUMBER: Clinicaltrials.gov identifier: NCT01816815. TRIAL REGISTRATION DATE: 20 March 2013. DATE OF FIRST PATIENT'S ENROLMENT: 28 November 2011.

From adults to children: simulation-based choice of an appropriate sparse-sampling schedule.

BACKGROUND: According to the International Conference on Harmonisation guideline E11, pharmacokinetic (PK) bridging studies can be applied to support pediatric drug development. However, for PK studies in infants and children the sampling schedule needs to be optimized to minimize the number of blood samples per individual. OBJECTIVE: The aim of this study was to describe how clinical trial simulations (CTS) based on adult data were used to select an appropriate sparse-sampling schedule for a future pediatric population PK (popPK) study. METHODS: A popPK model for gadobutrol (Gadovist®) was developed using data from a phase I study in adults. This model was used for CTS to select the most appropriate sparse-sampling schedule that met predefined acceptance criteria. This sampling schedule was applied in a pediatric clinical phase I/III study. Non-linear mixed-effects modeling was used for PK modeling and simulations. RESULTS: An appropriate sampling schedule requiring only three blood samples per patient was selected and successfully applied in a pediatric study with a gadobutrol standard dose of 0.1 mmol/kg bodyweight. A popPK analysis was performed to determine individual PK parameters in the pediatric study population. CONCLUSIONS: A priori evaluation of selected sampling schedules by simulation from adult data provides a useful tool for efficient planning of pediatric studies.

Evaluation of possible drug-drug interaction between gadoxetic acid and erythromycin as an inhibitor of organic anion transporting peptides (OATP).

PURPOSE: To evaluate if erythromycin compromises liver-specific enhancement of gadoxetic acid; both compounds competing in organic anion transporting peptides (OATP) -mediated hepatocytic uptake. MATERIALS AND METHODS: The study was approved by institutional review board. Twelve healthy subjects (nine men, three woman; mean age, 38.7 years) were examined twice by MR imaging with prior administration of NaCl solution (placebo) or 1000 mg of erythromycin following a randomized sequence. Gadoxetic acid (0.025 mmol/kg body weight) was administered 15 min after the end of infusions. Pre- and 20 min postcontrast two-dimensional gradient-recalled-echo sequences were acquired. Relative enhancements of liver parenchyma and ratio of means were calculated from signal intensity measurements. Plasma levels of gadoxetic acid and erythromycin were determined and given in geometric means and coefficients of variation (CV). RESULTS: Concentration of erythromycin directly after end of infusion was 13.9 mg/L (CV 14.9%). Gadolinium plasma concentrations 5 min after gadoxetic acid administration were 138.7 µmol/L (CV 20.4%) after erythromycin infusion and 129.6 µmol/L (CV 22.8%) after placebo. Mean relative enhancements of liver parenchyma were 88.1 (SD 24.9%) after erythromycin infusion and 92.6 (SD 17.9%) after placebo. Ratio of relative enhancements was 0.951 (95% confidence interval, 0.833; 1.061; statistically not significant). CONCLUSION: Coadministration of erythromycin has no effect on gadoxetic acid enhanced liver MR imaging.

Evaluation of gas-filled microparticles and sonoporation as gene delivery system: feasibility study in rodent tumor models.

PURPOSE: To evaluate the feasibility of gene delivery mediated with diagnostic ultrasound and plasmid DNA (pDNA) encapsulated in gas-filled microparticles (GFMP) in rodent tumor models. MATERIALS AND METHODS: This study was performed according to a protocol approved by the regional animal research committee. The model plasmid UT651 (pUT651) that contained the Escherichia coli LacZ gene for beta-galactosidase was used to demonstrate the feasibility of ultrasound-mediated gene delivery in CC531 liver tumors in rats. In preliminary experiments, a single injection of pUT651-containing GFMP was administered intraarterially (n=4) or intravenously (n=6) with simultaneous sonication (color Doppler mode, maximum mechanical index) of the GFMP passing through the capillaries of the tumors. All animals were sacrificed 2-5 days later, and liver tumors were examined for beta-galactosidase expression histochemically. Subsequently, potential medical usefulness of this delivery system was tested in nude mice bearing Capan-1 tumors (adenocarcinoma of the human pancreas) by using the plasmid RC/CMV-p16 (pRC/CMV-p16), which contains tumor suppressor gene p16. The tumor suppressor gene p16 is deleted in Capan-1 cells. Twenty-five tumor-bearing mice were classified into five groups (four to six mice per group, one treatment group, four control groups) at random. All mice were treated once weekly for 5 weeks with intravenous infusion of p16-containing GFMP or control substances with simultaneous tumor sonication with color Doppler mode ultrasound and maximum mechanical index or without ultrasound treatment. The therapeutic effect of p16 was measured as an increase in tumor volume doubling time. Data were analyzed with analysis of variance. Results were considered significant at the 5% critical level (P < .05). RESULTS: A clear expression of pDNA was found in tumors in rats treated with a combination of pUT651-containing GFMP and ultrasound; relevant controls showed a significantly lower expression of marker gene. The controlled ultrasound-triggered release of pRC/CMV-p16 from GFMP leads to a strong tumor growth inhibition, which is significant (P < .002), compared with that in controls. CONCLUSION: A combination of GFMP and ultrasound provides an effective approach for nonviral gene therapy-based cancer treatment.

Pharmaceutical evaluation of gas-filled microparticles as gene delivery system.

PURPOSE: To produce and characterize a nonviral ultrasound-controlled release system of plasmid DNA (pDNA) encapsulated in gas-filled poly(D,L-lactide-co-glycolide) microparticles (PLGA-MPs). METHODS: Different cationic polymers were used to form pDNA/polymer complexes to enhance the stability of pDNA during microparticle preparation. The physico-acoustical properties of the microparticles, particle size, pDNA integrity, encapsulation efficiency and pDNA release behavior were studied in vitro. RESULTS: The microparticles had an average particle size of around 5 microm. More than 50% of all microparticles contained a gas core, and when exposed to pulsed ultrasound as used for color Doppler imaging create a signal that yields typical color patterns (stimulated acoustic emission) as a result of the ultrasound-induced destruction of the microparticles. Thirty percent of the pDNA used was successfully encapsulated and approximately 10% of the encapsulated pDNA was released by ultrasound within 10 min. CONCLUSIONS: Plasmid DNA can be encapsulated in biodegradable gas-filled PLGA-MPs without hints for a structural disintegration. A pDNA release by ultrasound-induced microparticle-destruction could be shown in vitro.