Therapeutic effects of leuprorelin microspheres on endometriosis and uterine leiomyomata

Advances in encapsulating gonadotropin-releasing hormone agonists for controlled release: a review

Gonadotropin-releasing hormone (GnRH) agonists are peptides consisting of nine or ten amino acid residues. GnRH agonists have been applied in the therapy of sexual hormone disorders like prostate cancer, endometriosis, uterine myoma, central precious puberty, and in-vitro fertility. Treatment is achieved by continuous hormone intake and long-term agonists administration, which is usually associated with poor patient compliance. Because GnRH agonists that are administered with the parenteral route are broken down by peptidase, their half-life is short. As a result, developing sustained release for the drug delivery system is significant. Even though some drugs have been successfully delivered with long-acting release microspheres and approved by the Food and Drug Administration (FDA), some challenges remain. This review highlighted current approaches to encapsulate GnRH agonists into delivery systems and strategies encountered during the loading process. Moreover, the following sections provide strategies to improve the release profile, and animal and human studies were summarised.

Enhancing the therapeutic efficacy of adenovirus in combination with biomaterials

With the reason that systemically administered adenovirus (Ad) is rapidly extinguished by innate/adaptive immune responses and accumulation in liver, in vivo application of the Ad vector is strictly restricted. For achieving to develop successful Ad vector systems for cancer therapy, the chemical or physical modification of Ad vectors with polymers has been generally used as a promising strategy to overcome the obstacles. With polyethylene glycol (PEG) first in order, a variety of polymers have been developed to shield the surface of therapeutic Ad vectors and well accomplished to extend circulation time in blood and reduce liver toxicity. However, although polymer-coated Ads can successfully evacuate from a series of guarding systems in vivo and locate within tumors by enhanced permeability and retention (EPR) effect, the possibility to entering into the target cell is few and far between. To endow targeting moiety to polymer-coated Ad vectors, a diversity of ligands such as tumor-homing peptides, growth factors or antibodies, have been introduced with avoiding unwanted transduction and enhancing therapeutic efficacy. Here, we will describe and classify the characteristics of the published polymers with respect to Ad vectors. Furthermore, we will also compare the properties of variable targeting ligands, which are being utilized for addressing polymer-coated Ad vectors actively.

Add-back therapy use and its impact on LA persistence in patients with endometriosis

OBJECTIVES

Persistence and compliance in women with endometriosis who are receiving gonadotropin-releasing hormone agonists (GnRH-a) may be limited by its hypoestrogenic side effects. Use of concomitant therapy with norethindrone acetate (NA), estrogen, estrogen/progestin combinations, or other progestin (i.e., 'add-back therapy' [ABT]) is recommended to alleviate these side effects. This retrospective study evaluated ABT utilization and its effect on compliance and persistence in patients with endometriosis taking the GnRH-a leuprolide acetate (LA) depot suspension.

METHODS

A retrospective analysis of a large pharmacy claims database identified patients who started LA therapy from 2002 to 2004 for the treatment of endometriosis. Patients were identified as having received ABT if they started 7 days before, or within 45 days of the last LA fill.

RESULTS

A total of 1285 women with endometriosis who began using LA were identified with 12 months of evaluable data: 211 (16.4%) used concomitant NA therapy, 116 (9.0%) used concomitant estrogen-based therapy, 28 (2.2%) used concomitant combination estrogen- and progestin-based therapies, 56 (4.4%) used concomitant progestin-based therapy, and 874 (68.0%) did not use any ABT. Mean (+/-SD) LA persistence in women receiving NA-based ABT was 5.83 +/- 2.98 months, compared with 4.25 +/- 2.62 months for those not using ABT (P < 0.0001). Average medication possession ratio was 0.43 +/- 0.20 for women receiving NA-based ABT versus 0.32 +/- 0.18 for those not receiving any ABT (P < 0.0001). Patients < 30 years of age were most likely to continue therapy longer and have greater compliance compared with the older age group cohorts (P < 0.01). Patients who used ABT continued to do so for 3.79 +/- 3.21 months.

LIMITATIONS

Limitations of this study include those associated with the use of retrospective claims databases: It does not include any information regarding the patient's pain symptoms, disease severity, or other factors, which could correlate to compliance and persistence.

CONCLUSIONS

Among women using LA therapy for endometriosis, only 32% used any type of ABT, and these patients had significantly higher persistence and compliance with LA therapy compared to no ABT user group.

Zinc-leuprolide complex: preparation, physicochemical characterization and release behaviour from in situ forming implant

Leuprolide acetate (LA) has been accepted as treatment for prostatic cancer and is currently also being evaluated in phase II clinical trials for the treatment of Alzheimer's disease. In this study, the zinc complex of leuprolide was prepared and its structure determined by Fourier-transform infrared (FTIR), differential scanning calorimetry (DSC), UV, X-ray diffraction (XRD), atomic absorption spectroscopy, elemental analysis, and compared with these parameters for leuorolide acetate. Also, the in vitro release profile of leuprolide and its complex form in situ forming implant (ISFI) in comparison to a commercial formulation (Eligard) was investigated. These studies indicate that the zinc complex can be effectively synthesized and influenced on tri-phasic pattern after burst release of LA from the ISFI and shifts this trend to a continuous release profile. Non-linear regression test confirmed this transformation as a zero-order release profile as well.

Nanoparticles as potential oral delivery systems of proteins and vaccines: a mechanistic approach

Peptides and proteins remain poorly bioavailable upon oral administration. One of the most promising strategies to improve their oral delivery relies on their association with colloidal carriers, e.g. polymeric nanoparticles, stable in gastrointestinal tract, protective for encapsulated substances and able to modulate physicochemical characteristics, drug release and biological behavior. The mechanisms of transport of these nanoparticles across intestinal mucosa are reviewed. In particular, the influence of size and surface properties on their non-specific uptake or their targeted uptake by enterocytes and/or M cells is discussed. Enhancement of their uptake by appropriate cells, i.e. M cells by (i) modeling surface properties to optimize access to and transport by M cells (ii) identifying surface markers specific to human M cell allowing targeting to M cells and nanoparticles transcytosis is illustrated. Encouraging results upon in vivo testing are reported but low bioavailability and lack of control on absorbed dose slow down products development. Vaccines are certainly the most promising applications for orally delivered nanoparticles.