Determination of Leuprolide-Fatty Acid Conjugate in Rat Plasma Using LC-MS/MS and Its Pharmacokinetics after Subcutaneous Administration in Rats.

Leuprolide is a synthetic nonapeptide drug (pyroGlu-His-Trp-Ser-Tyr-d-Leu-Leu-Arg-Pro-NHEt) that acts as a gonadotropin-releasing hormone agonist. The continuous administration of therapeutic doses of leuprolide inhibits gonadotropin secretion, which is used in androgen-deprivation therapy for the treatment of advanced prostate cancer, central precocious puberty, endometriosis, uterine fibroids, and other sex-hormone-related conditions. To improve the pharmacokinetic properties of peptide drugs, a fatty acid was conjugated with leuprolide for long-term action. In this study, we developed a simple ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous determination of leuprolide and leuprolide-oleic acid conjugate (LOC) levels. The developed method was validated in terms of linearity, precision, accuracy, recovery, matrix effect, and stability according to the US Food and Drug Administration guidelines, and the parameters were within acceptable limits. Subsequently, the pharmacokinetics of leuprolide and LOCs were evaluated. In vivo rat subcutaneous studies revealed that conjugation with fatty acids significantly altered the pharmacokinetics of leuprolide. After the subcutaneous administration of fatty-acid-conjugated leuprolide, the mean absorption time and half-life were prolonged. To the best of our knowledge, this is the first study showing the effects of fatty acid conjugates on the pharmacokinetics of leuprolide using a newly developed UPLC-MS/MS method for the simultaneous quantification of leuprolide and LOCs.

Pharmacokinetic and pharmacodynamic evaluation of the new prolonged-release leuprorelin acetate microspheres for injection compared with Enantone® in healthy Chinese male volunteers.

PURPOSE: To compare the pharmacokinetics, pharmacodynamics and safety of the new prolonged-release leuprorelin acetate microspheres for injection (3.75 mg) with the reference product Enantone® (3.75 mg). METHOD: 48 healthy male volunteers were enrolled and randomly received a single 3.75 mg dose of the test drug or Enantone®. RESULTS: There were no significant differences in Cmax, AUC0-t and AUC0-48 between the test group and reference group (P > 0.05). The 90% confidence intervals of the two groups were 87.49%~112.74%, 97.15%~154.25%, and 80.85%~109.01%, respectively. Twenty-eight days after administration, both groups reached 100.0% castration level; there was no difference in the time from administration to reaching castration level between the two groups (P > 0.05); However, the difference between the two groups in the duration of castration level was statistically significant (P < 0.05). There were no major or serious adverse events, and the severity was mild to moderate. CONCLUSION: The pharmacokinetic characteristics of leuprorelin in two groups were consistent. The two groups exhibited similar inhibitory effects on testosterone and more subjects in the test group maintained a longer castration time than those in the reference group.

Initial Leuprolide Acetate Release from Poly(d,l-lactide-co-glycolide) in Situ Forming Implants as Studied by Ultraviolet-Visible Imaging.

The initial drug release from in situ forming implants is affected by factors such as the physicochemical properties of the active pharmaceutical ingredient, the type of the excipients utilized, and the surrounding environment. The feasibility of UV-vis imaging for characterization of the initial behavior of poly(d,l-lactide-co-glycolide) (PLGA)/1-methyl-2-pyrrolidinone (NMP) in situ forming implants was investigated. The in vitro release of leuprolide acetate (LA) and implant formation in real time were monitored using dual-wavelength imaging at 280 and 525 nm, respectively, in matrices based on agarose gel and hyaluronic acid (HA) solution emulating the subcutaneous matrix. Three hours upon injection of the pre-formulation, approximately 15% of the total amount of LA administered was found in the agarose gel, while 5% was released from the implant into the HA solution. Concurrently, more extensive swelling of the implants in the HA solution as compared to implants in the agarose gel was observed. Transport of both LA and the solvent NMP was investigated using UV-vis imaging in a small-scale cell where the geometry of the formulation was controlled, showing a linear correlation between drug release and solvent escape. Light microscopy showed that the microstructures of the resulting implants in agarose gel and HA solution were different, which may be attributed to the different solvent exchange rates. UV imaging was also used to examine the interaction of LA with the release medium by characterizing the diffusion of LA in agarose gel, HA solution, and phosphate buffered saline. The reduced LA diffusivity in HA solution as compared to agarose gel and the LA distribution coefficient in the agarose gel-HA system indicated the presence of interactions between LA and HA. Our findings show that the external environment affects the solvent exchange kinetics for in situ forming implants in vitro, resulting in different types of initial release behavior. UV-vis imaging in combination with biorelevant matrices may offer an interesting approach in the development of in situ forming implant delivery systems.

Phase 3 Trial of a Small-volume Subcutaneous 6-Month Duration Leuprolide Acetate Treatment for Central Precocious Puberty.

CONTEXT: Gonadotropin-releasing hormone agonists (GnRHas) are standard of care for central precocious puberty (CPP). A 6-month subcutaneous injection has recently been approved by the Food and Drug Administration. OBJECTIVE: Determine efficacy, pharmacokinetics, and safety of 6-month 45-mg subcutaneous leuprolide acetate for CPP. DESIGN: Phase 3 multicenter, open-label, single-arm study. SETTING: 25 sites in 6 countries. SUBJECTS: 64 GnRHa-naïve children with CPP (age: 7.5 ± 0.1 years) received study drug: 59 completed the study. INTERVENTION(S): 2 doses of 45-mg subcutaneous leuprolide acetate (0.375 mL) at 0 and 24 weeks; children were followed for 48 weeks. MAIN OUTCOME MEASURE(S): Percentage of children with serum luteinizing hormone (LH) <4 IU/L 30 minutes following GnRHa stimulation at week 24. RESULTS: 54/62 (87%) children achieved poststimulation LH <4 IU/L at week 24; 49/56 (88%) girls and 1/2 boys maintained peak LH <4 IU/L at week 48. Mean growth velocity decreased from 8.9 cm/year at week 4 to 6.0 cm/year at week 48. Mean bone age was advanced 3.0 years beyond chronological age at screening and 2.7 years at week 48. Breast pubertal stage regressed or was stable in 97% of girls and external genitalia development regressed in both boys. Adverse events were mild and did not cause treatment discontinuation. CONCLUSIONS: A small volume of 45-mg subcutaneous leuprolide acetate administered at a 6-month interval effectively suppressed pubertal hormones and stopped or caused regression of pubertal progression. This long-acting GnRHa preparation of leuprolide acetate is a new, effective, and well-tolerated therapy for children with CPP.

Solid lipid nanocarriers diffuse effectively through mucus and enter intestinal cells - but where is my peptide?

Peptides are therapeutic molecules with high potential to treat a wide variety of diseases. They are large hydrophilic compounds for which absorption is limited by the intestinal epithelial border covered by mucus. This study aimed to evaluate the potential of Hydrophobic Ion Pairing combined with Solid Lipid Nanoparticles (SLN) and Nanostructured Lipid Carriers (NLC) to improve peptide transport across the intestinal border using Caco-2 cell monolayers (enterocyte-like model) and Caco-2/HT29-MTX co-cultured monolayers (mucin-secreting model). A Hydrophobic Ion Pair (HIP) was formed between Leuprolide (LEU), a model peptide, and sodium docusate. The marked increase in peptide lipophilicity enabled high encapsulation efficiencies in both NLC (84%) and SLN (85%). After co-incubation with the nanoparticles, confocal microscopy images of the cell monolayers demonstrated particles internalization and ability to cross mucus. Flow cytometry measurements confirmed that 82% of incubated SLN and 99% of NLC were internalized by Caco-2 cells. However, LEU transport across cell monolayers was not improved by the nanocarriers. Indeed, combination of particles platelet-shape and HIP low stability in the transport medium led to LEU burst release in this environment. Improvement of peptide lipidization should maintain encapsulation and enable benefit from nanocarriers enhanced intestinal transport.

PEGylated leuprolide with improved pharmacokinetic properties.

Leuprolide, a gonadotropin-releasing hormone (GnRH) agonist widely used in androgen deprivation therapy for the treatment of advanced prostate cancer, suffers from a short circulating half-life like other peptide therapeutics. As an attempt to improve its pharmacokinetic properties, two PEGylated leuprolides with different molecular weight were synthesized utilizing N-hydroxysuccinimidyl (NHS) conjugation chemistry. The reaction conditions, including reaction temperature, reaction time and feed ratio of the reactants, were optimized to obtain a higher yield. Reverse-phase high performance liquid chromatography (RP-HPLC) characterization indicates a high purity of the resulting conjugates. Matrix-assisted laser desorption mass spectrometry (MALDI-MS) characterization suggests a 1:1 PEGylation. 1H NMR study reveals that the reaction occurs on the imidazolyl group on the histidine residue and the conjugates are stable in pH7.4 aqueous solutions. The in vitro bioactivity of the conjugates was evaluated using both hormone-sensitive and hormone-insensitive cell lines. It was found that the PEGylated peptides can still counteract the stimulatory action of androgens and the mitogenic action of epidermal growth factor on cell proliferation. The in vivo bioactivity of the conjugates was also tested. Like the unmodified peptide, administration of the conjugates to male rats leads to an initial testosterone surge, followed by a suppression of testosterone secretion. Pharmacokinetics of the drugs after i.v. and s.c. administrations were determined. In both cases, a prolonged circulating half-life, an increased AUC, and a decreased Cl_F were observed for the PEGylated drugs.

Hydrophobic H-bond pairing: A novel approach to improve membrane permeability.

The aim of the present study was to develop hydrophobic H-bond pairs (HHPs) of leuprolide (LEU) with non-ionic surfactants to improve its membrane permeability. LEU was lipidized via hydrophobic H-bond pairing (HHP) with the sucrose esters (SEs) sucrose laurate HLB 15 (SLA-15), sucrose palmitate HLB 16 (SPA-16), sucrose stearate HLB 11 (SST-11) and sucrose stearate HLB 15 (SST-15). HHPs were evaluated regarding precipitation efficiency in water, zeta potential, log Pn-octanol/water and dissociation behavior at various pH over time. Cytotoxic potential of HHPs of LEU with SST-11 was investigated on Caco-2 cells. Subsequently, ex vivo permeation studies were carried out across freshly excised Sprague-Dawley rat intestinal mucosa. At a molar ratio of LEU to SEs of 1:≥1 a precipitation efficiency of above 50% was achieved. Zeta potential of complexes was neither influenced by the type nor the amount of added surfactants. Log Pn-octanol/water of LEU was up to 250-fold increased due to HHP utilizing SST-11. Dissociation studies showed that HHPs of LEU with SST-11 dissociate up to 20% in gastrointestinal (GI) pH conditions within 4 h. Moreover, HHPs of LEU with SST-11 exhibited no cytotoxicity. Ex vivo permeation studies revealed 2-fold improved membrane permeation of HHPs of LEU with SST-11 compared to free LEU. Findings of this study show that HHP can be considered as a promising strategy to improve membrane permeation.

Development of Level A in vitro-in vivo correlations for peptide loaded PLGA microspheres.

Peptide loaded PLGA microsphere products are more complex in terms of manufacturing, drug release characteristics as well as release mechanism compared to small molecule loaded PLGA microsphere products. This is due to the complex structure of peptides, their hydrophilicity, charged state, large size and potential for instability. Moreover, therapeutic peptides are highly potent and therefore, any unintended change in the microsphere release profile may lead to undesirable side effects and toxicity. Accordingly, the objectives of the present work were: 1) to evaluate the impact of minor manufacturing changes on the quality and performance of peptide microspheres; and 2) to investigate the feasibility of developing Level A in vitro-in vivo correlations (IVIVCs) for peptide microspheres. Compositionally equivalent leuprolide acetate (LA) microspheres prepared with minor manufacturing changes (solvent system/homogenization speed) showed significant differences in their physicochemical properties (such as pore size, total porosity, particle size and surface distribution of peptide on the prepared microspheres). This, in turn, resulted in significant alteration in the release characteristics. Peptide-polymer interaction, in vitro degradation and microsphere morphology studies were conducted to facilitate understanding of the differences in the drug release characteristics. A rabbit model was used to determine the pharmacokinetic profiles of all the prepared formulations. The obtained in vivo release profiles showed the same rank order as the in vitro release profiles but with low burst release and overall faster in vivo release rates. The low in vivo burst release is considered to be due to the masking effect of the absorption phase from the intramuscular site, and this complicated the development of an IVIVC. Despite these challenges, an affirmative Level A IVIVC over the entire release profile was successfully developed in a rabbit model for peptide microspheres for the first time. The developed IVIVC was also predictive of the RLD product, Lupron Depot®. This work highlights the feasibility of developing IVIVCs for complex parenteral drug products such as peptide microspheres. In conclusion, these results indicate the sensitivity of peptide release, and hence, the safety and efficacy of highly potent peptide microspheres, to minor manufacturing changes. Accordingly, development of IVIVCs for such complex drug products is highly desirable.

A New Sustained-release, 3-Month Leuprolide Acetate Formulation Achieves and Maintains Castrate Concentrations of Testosterone in Patients With Prostate Cancer.

PURPOSE: This clinical trial investigated the effectiveness, pharmacokinetic properties, and safety profile of leuprolide acetate 22.5-mg depot, a new 3-month leuprolide depot formulation, as androgen deprivation therapy for patients with prostate cancer. METHODS: A Phase III, open-label, multicenter study design for patients with prostate cancer, with patient inclusion assessed by the investigative site as patient's appropriate for androgen deprivation therapy. Patients received 2 separate intramuscular injections of leuprolide acetate 22.5-mg depot for a 3-month depot interval of therapeutic effect. Plasma testosterone concentrations were determined throughout the study. The primary efficacy analysis was the percentage of patients who achieve and maintain castrate testosterone levels (≤50 ng/mL) from days 28-168. Secondary end points included luteinizing hormone, follicle-stimulating hormone, prostate-specific antigen, and safety assessments. A pharmacokinetic study was also conducted in a subset of 30 patients. FINDINGS: All 163 patients enrolled in the study received at least 1 dose of study drug; 162 of them were fully evaluable and 151 completed the study. Castrate levels of testosterone were achieved and maintained from days 28-168 in 96.8% (95% CI, 92.5%-98.7%) of patients. Five patients presented with sporadic testosterone levels >50 ng/dL. By day 28, of the 161 patients, 150 (99.4%) had achieved castrate levels, and 127 (78.9%) had achieved testosterone concentrations ≤20 ng/dL. At study end, 149 of 151 patients (98.7%) patients achieved castrate testosterone levels, with 142 of 151 (94.0%) having testosterone levels ≤20 ng/dL. At study end, mean luteinizing hormone and follicle-stimulating hormone concentrations had decreased from baseline to below the lower limit of quantitation and below baseline levels, respectively, whereas mean serum prostate-specific antigen was reduced by 94.7% from baseline. Most patients (>96%) had no change in their World Health Organization/Eastern Cooperative Oncology Group score, whereby 84.0% of patients had a baseline score of 0. Bone pain, urinary pain, and urinary symptoms were infrequent and remained so throughout the study. After administration, leuprolide concentrations increased rapidly. The peak was followed by a decline up to day 28, maintaining sustained drug levels until the following dose on day 84. The most common related treatment-emergent adverse events, detected in >5% of patients, were hot flushes, fatigue, and injection site pain reported by 77.3%, 9.8%, and 9.2% of patients, respectively. IMPLICATIONS: Leuprolide acetate 22.5-mg depot was effective in achieving and maintaining testosterone suppression. Safety and tolerability profiles were consistent with established profiles of androgen deprivation therapy. Clinical Trials.gov identifier: NCT01415960.

Population pharmacokinetic-pharmacodynamic modelling of the relationship between testosterone and prostate specific antigen in patients with prostate cancer during treatment with leuprorelin.

AIMS: This investigation aimed to quantitatively characterize the relationship between the gonadotropin-releasing hormone agonist leuprorelin, testosterone (T) and prostate specific antigen (PSA) concentrations over time, to aid identification of a target T concentration that optimises the balance of the benefits of T suppression whilst reducing the risk of side effects related to futile over-suppression. METHODS: Data from a single dose study to investigate the effect of leuprorelin in a 6-month depot formulation on T and PSA in prostate cancer patients were analysed using a population pharmacokinetic-pharmacodynamic modelling approach. The developed model was qualified using external data from 3 studies, in which the effect of different formulations of leuprorelin on T and PSA was evaluated in prostate cancer patients. RESULTS: The effect of leuprorelin on the relationship between T and PSA was adequately characterized by the Romero model with minor modifications, combined with a turnover model to describe the delay in response between T and PSA. The data were significantly better described when assuming a minimum PSA level that is independent on the treatment-related reduction in T, as compared to a model with a proportional reduction in PSA and T. CONCLUSIONS: The model-based analysis suggests that on a population level, reducing T concentrations below 35 ng/dL does not result in a further decrease in PSA levels (>95% of the minimal PSA level is reached). More data are required to support this relationship in the lower T and PSA range.

Reverse Engineering the 1-Month Lupron Depot®.

The 1-month Lupron Depot® (LD) encapsulating water-soluble leuprolide in poly(lactic-co-glycolic acid) (PLGA) microspheres is a benchmark product upon which modern long-acting release products are often compared. Despite expiration of patent coverage, no generic product for the LD has been approved in the USA, likely due to the complexity of components and manufacturing processes involved in the product. Here, we describe the reverse engineering of the LD composition and important product attributes. Specific attributes analyzed for microspheres were as follows: leuprolide content by three methods; gelatin content, type, and molecular weight distribution; PLGA content, lactic acid/glycolic acid ratio, and molecular weight distribution; mannitol content; in vitro drug release; residual solvent and moisture content; particle size distribution and morphology; and glass transition temperature. For the diluent, composition, viscosity, and specific gravity were analyzed. Analyzed contents of the formulation and the determined PLGA characteristics matched well with the official numbers stated in the package insert and those found in literature, respectively. The gelatin was identified as type B consistent with ~ 300 bloom. The 11-µm volume-median microspheres in the LD slowly released the drug in vitro in a zero-order manner after ~ 23% initial burst release. Very low content of residual moisture (< 0.5%) and methylene chloride (< 1 ppm) in the product indicates in-water drying is capable of removing solvents to extremely low levels during manufacturing. The rigorous approach of reverse engineering described here may be useful for development of generic leuprolide-PLGA microspheres as well as other new and generic PLGA microsphere formulations.

Differential effects of depot formulations of GnRH agonist leuprorelin and antagonist degarelix on the seminiferous epithelium of the rat testis.

Despite their pharmacologically opposite actions, long-acting depot formulations of both GnRH agonists and antagonists have been clinically applied for treatment of androgen-sensitive prostate cancer. Sustained treatment with GnRH analogues commonly suppresses both the synthesis and release of gonadotropins, leading to depletion of testicular testosterone. To clarify the underlying differences in the effects of GnRH agonists and antagonists on spermatogenesis, we compared histological changes in the seminiferous epithelium after administration of depot formulations of GnRH agonist leuprorelin and antagonist degarelix to male rats. Testicular weight had markedly declined by 28 days after administration of both GnRH analogues, although the testicular weight was decreased more promptly by leuprorelin compared with degarelix. Shortly after administration, massive exfoliation of premature spermatids and anomalous multinucleated giant cells was observed in seminiferous tubules of leuprorelin-treated rats, probably via the initial hyperstimulatory effects on the hypothalamic-pituitary-testicular axis, whereas no discernible changes were found in those of degarelix-treated rats. Long term treatment with both types of GnRH analogues similarly induced a marked reduction in the height of the epithelium and deformation of apical cytoplasm in Sertoli cells, resulting in premature detachment of spermatids from the epithelium. Lipid droplets had accumulated progressively in Sertoli cells, especially in those of degarelix-treated rats. These findings clearly demonstrate the differences in the effects of GnRH agonists and antagonists on the spermatogenic process. This study suggests that an appropriate choice of GnRH analogues is necessary to minimize their adverse effects on spermatogenesis when reproductive functions should be preserved in patients.

Pharmacokinetic-Pharmacodynamic Model for the Testosterone-Suppressive Effect of Leuprolide in Normal and Prostate Cancer Rats.

This study developed the pharmacokinetic (PK)-pharmacodynamic (PD) model of the testosterone-suppressive effect of leuprolide for evaluation of the sustained release (SR) depot and leuprolide solution in rats with or without prostate cancer. Six groups of rats were divided by the routes of administration (intravenous and subcutaneous injection) and kinds of formulation (vehicle, leuprolide solution, and SR depot). The PK profile after subcutaneous injection of leuprolide solution could be well-described by the one-compartment model. The absorption rate constant, the total body clearance, and the volume of distribution were estimated at 16.67 h-1, 514.46 mL/h, and 487.40 mL. Using PK parameters in the solution-administered group, the PK model for the SR depot was developed. The PK-PD model was constructed by describing the testosterone-suppressive effect of leuprolide using the feedback turnover model. The response of testosterone after administration of each formulation was well described using this PK-PD model for the estimation of PD parameters (EC50, Emax, h) and systemic parameters (kin, kout, kf on, kf off). The developed PK-PD model containing an inhibitory feedback system could successfully describe the testosterone-suppressive effect of leuprolide in the type of formulation. The PK-PD model developed would be useful for evaluating the formulation of similar drugs whose effect is regulated through the feedback mechanism.

Formulation of 99mTechnetium-labeled leuprolide loaded liposomes and its biodistribution study in New Zealand white female rabbits for assessment of its uterine targeting efficiency.

Leuprolide acetate (LPA), a GnRH analogue, is drug of choice for treatment of uterine fibroids and endometriosis. The current marketed formulations of LPA show severe systemic side effects. This project aims to formulate LPA loaded liposomes to be administered by vaginal route for uterine targeting. Liposomes were prepared by thin film hydration method using 1:1 M ratio of DSPC: Cholesterol and characterized for vesicle size, zeta potential, entrapment efficiency, and loading. Radiolabeling of LPA was performed by direct labeling with reduced technetium-99m. Binding affinity of 99mTc-labeled complexes was assessed by diethylenetriaminepentaacetic acid (DTPA) challenge test. Biodistribution study was done in New Zealand white female rabbits by administering the formulation via vaginal route. Spherical and discrete vesicles of size 189 nm were seen in TEM results with entrapment efficiency and loading of 74.36% and 9.29%w/w, respectively. Liposomes were able to sustain the drug release for 5 days. 99mTc-labeled complexes showed high labeling efficiency and stability both in saline and serum. DTPA challenge test confirmed low transchelation of 99mTc-labeled complexes. Biodistribution study by gamma scintigraphy revealed the preferential uptake of the formulation by uterus when administered vaginally. Compared to plain drug, liposomes concentrated and were retained within the uterus for a longer period of time. Uterine targeting of liposomal LPA indicates its potential to overcome the limitations of presently available formulations. Hence, this seems to be a promising approach for targeting the drugs, whose site of action is uterus.

The in vivo transformation and pharmacokinetic properties of a liquid crystalline drug delivery system.

A liquid crystalline (LC) system, composed of phosphatidylcholine, sorbitan monoleate, and tocopherol acetate, was investigated to understand the in vivo transformation after subcutaneous injection, coupled with the physicochemical and pharmacokinetic properties of the formulation. The rat model was utilized to monitor a pseudo-time course transformation from a precursor LC formulation to the LC matrix, coupled with the blood concentration profiles of the formulations containing leuprolide acetate. Three formulations that result in the HII phase, demonstrating dissimilar in vitro release profiles, were used. The formulation showing the highest AUC, Cmax and Tmax, also displayed the greatest release rate in vitro, the lowest viscosity (LC matrix), and an earlier transformation (LC precursor to matrix) in vivo. A potential link between viscosity, phase transformation, and drug release properties of a liquid crystalline system is described.

Efficacy and safety of leuprorelin acetate 6-month depot, TAP-144-SR (6M), in combination with tamoxifen in postoperative, premenopausal patients with hormone receptor-positive breast cancer: a phase III, randomized, open-label, parallel-group comparative study.

BACKGROUND: Leuprorelin acetate, a luteinizing hormone-releasing hormone agonist, is used worldwide in premenopausal women with hormone receptor-positive breast cancer. This study was conducted to assess the non-inferiority of the 6-month depot formulation, TAP-144-SR (6M) 22.5 mg to the 3-month depot formulation, TAP-144-SR (3M) 11.25 mg in postoperative, premenopausal patients with hormone receptor-positive breast cancer. METHODS: This was a 96-week phase III, randomized, open-label, parallel-group comparative study. All patients concomitantly received oral tamoxifen (20 mg daily). The primary endpoint was the suppression rate of serum estradiol (E2) to the menopausal level (≤30 pg/mL) from Week 4 through Week 48. RESULTS: In total, 167 patients were randomized to receive TAP-144-SR (6M) (n = 83) or TAP-144-SR (3M) (n = 84) and the E2 suppression rate was 97.6 and 96.4 %, respectively. The estimated between-group difference was 1.2 % (95 % confidence interval -5.2 to 7.8). The non-inferiority of TAP-144-SR (6M) to TAP-144-SR (3M) for E2 suppression was confirmed. As for safety, common adverse events were hot flush and injection site reactions including induration, pain, and erythema in both treatment groups, which were of ≤Grade 2 in severity and not serious. No significant between-group differences in safety profiles and tolerability were observed. CONCLUSIONS: TAP-144-SR (6M) was not inferior to TAP-144-SR (3M) for its suppressive effect on serum E2. TAP-144-SR (6M) was also as well tolerated as TAP-144-SR (3M).

Comparative in vitro release and clinical pharmacokinetics of leuprolide from Luphere 3M Depot, a 3-month release formulation of leuprolide acetate.

A 3-month depot formulation of leuprolide acetate (Luphere 3M Depot) with a mean microsphere diameter of 22.3 µm was prepared aseptically by spray-drying glacial acetic acid solution of the drug and polylactic acid, and lyophilization in a d-mannitol solution. The encapsulation efficiency and loading content of the drug in the Luphere 3M Depot were 94.7% and 9.92% (w/w), respectively. The in vitro release of leuprolide from the depot was substantially delayed and the release profile was similar to that of Lucrin Depot (Abbott Korea, Korea). The safety and pharmacokinetics of leuprolide were investigated over a period of 42 days in 20 prostate cancer patients following a subcutaneous injection of Luphere 3M or Lucrin Depot suspensions (leuprolide acetate dose of 11.25 mg) in a multi-center, randomized, single dose, parallel study. Both formulations were well tolerated by the patients and no serious adverse effects were observed during and after the study. No significant differences were observed in the maximum serum concentration (Cmax) and area under the curve (AUClast) of leuprolide between the two formulations. The results suggest comparable safety and efficacy profiles of Luphere 3M Depot and Lucrin Depot in clinical situations.

Validation of a cage implant system for assessing in vivo performance of long-acting release microspheres.

Here we describe development of a silicone rubber/stainless steel mesh cage implant system, much like that used to assess biocompatibility of biomaterials [1], for easy removal of injectable polymer microspheres in vivo. The sterile cage has a type 316 stainless steel mesh size (38 µm) large enough for cell penetration and free fluid flow in vivo but small enough for microsphere retention, and a silicone rubber shell for injection of the microspheres. Two model drugs, the poorly soluble steroid, triamcinolone acetonide, and the highly water-soluble luteinizing hormone-releasing hormone (LHRH) peptide superagonist, leuprolide, were encapsulated in PLGA microspheres large enough (63-90 µm) to be restrained by the cage implant in vivo. The in vitro release from both formulations was followed by ultra-performance liquid chromatography (UPLC) with and without the cage in a standard release media, PBS pH 7.4 + 0.02% Tween 80 + 0.05% sodium azide, at 37 °C. Pharmacokinetics (PK) in rats was assessed after SC injection or SC in-cage implantation of microspheres with plasma analysis by LC-MS/MS or EIA. Tr-A and leuprolide in vitro release was largely unaffected after the initial burst irrespective of the cage or test tube incubation vessel and release was much slower than observed in vivo for both drugs. Moreover, Tr-A and leuprolide pharmacokinetics with and without the cage were highly similar during the 2-3 week release duration before a significant inflammatory response was caused by the cage implant. Hence, the PK-validated cage implant provides a simple means to recover and evaluate the microsphere drug carriers in vivo during a time window of at least a few weeks in order to characterize the polymer microsphere release and erosion behavior in vivo. This approach may facilitate development of mechanism-based in vitro/in vivo correlations and enable development of more accurate and useful in vitro release tests.

In situ-forming PLGA implants loaded with leuprolide acetate/ß-cyclodextrin complexes: mathematical modelling and degradation.

Drug release mechanism of in situ-forming implants (ISIs) based on poly(lactic acid-co-glycolic acid) (PLGA) loaded with leuprolide acetate/ß-cyclodextrin (LA/ß-CD) complexes via fitting with four diffusion-based semi-empirical models were studied. The release rate constants and release exponent of ISIs were calculated. The main drug release mechanism was Fickian diffusion. The LA diffusion coefficient and release constant were decreased via increasing the portion of ß-CD in complexes. The release curve was parabolic, with a higher initial slope and then consistent with the exponential. All ISIs containing LA/ß-CD complexes better fitted with the Korsmeyer-Peppas, Weibull and Peppas-Sahlin models rather than first-order model. Furthermore, the effect of LA/ß-CD complexation on the degradation of ISIs was studied through scanning electron microscopy (SEM). Results showed that hydrophilic nature of ß-CD facilitated the surface erosion of PLGA chains, however after 18 d, ISI-1/10 had still a proper structural strength, due to no hydrolytic degradation of ß-CD in this implant.

Impact of lipases on the protective effect of SEDDS for incorporated peptide drugs towards intestinal peptidases.

AIM: The aim of this study is the development of self-emulsifying drug delivery systems (SEDDS) differing in amounts of ester substructures and to evaluate their stability in presence of pancreatic lipase and protective effect against luminal enzymatic metabolism using leuprorelin as model peptide drug. METHODS: Hydrophobic leuprolide oleate was incorporated into three different SEDDS formulations and their stability towards pancreatic lipases was investigated utilizing a dynamic in vitro digestion model. Protective effect of SEDDS in respect to peptide drug stability against proteolytic enzymes, trypsin and α-chymotrypsin, was determined via HPLC. RESULTS: Results of in vitro digestion demonstrated that 80% of SEDDS containing the highest amount of ester linkages was degraded within 60min. In comparison to that, SEDDS without ester bonds showed no degradation. With increasing oil droplets hydrolysis the remaining amount of peptide encapsulated into formulation decreased. Furthermore, after 180min incubation with trypsin up to 33.5% and with α-chymotrypsin up to 60.5% of leuprolide oleate was intact while leuprorelin acetate aqueous solution was completely metabolized by trypsin within 120min and by α-chymotrypsin within 5min. Protective effect in environment containing lipases was lower due to oil phase degradation, however, the amount of peptide in ester-free SEDDS was remarkably higher compared to SEDDS susceptible to lipases. CONCLUSION: The present study revealed that SEDDS stable towards hydrolysis is able to exhibit a protective effect for oral peptide delivery.