Studies On The Fixed Dose Combination Pulmonary Delivery System Of Salmeterol Xinafoate And Mometasone Furoate

BackgroundPulmonary delivery system, as a topical route of administration in the treatment of respiratory diseases, has been widely used in clinical. Compared with other routes of administration, the lung tissue has a large surface area for drug absorption (about 100m2), and is rich of vessels that help the drug be rapidly absorbed into the blood circulation and avoid the first-pass effect. Pulmonary delivery is the main administration way to treat asthma, bronchitis and cystic fibrosis. Inhaled corticosteroid (ICS) is recommended by asthma management guidelines as first-line controller therapy for all kinds of asthma, either as mono therapy or as combination therapy in order to achieve additional control. For patients who are not controlled on ICS alone, United States and European guidelines recommend the addition of a long acting beta-agonist (LABA). Due to a noted safety risk, FDA guidelines recommend that LABAs could not be used as mono therapy in asthma but preferably be combined with ICS in a fixed dose combination device. Though salmeterol xinafoate (Serevent,50μg) and mometasone furoate (Asmanex Twisthaler, 220μg) are usually administered together in clinical to overcome the phenomena mentioned above, however there are still some disadvantages:(1) Currently available products containing two APIs are produced by blending discrete micronized particles of both APIs with a carrier and loading into a device. Few researches are carrying on with fixed dose combinations of SX and MF by now. (2) The operations of inhalation device could affect the drug delivery significantly, so it is hard to promise that the two drugs would still be in effective ratios after administered to the body. (3) It is almost impossible to keep the drugs deposited into the same part of lung tissue (co-deposition) by taking drugs separately. (4) Micronized API particles can possess different crystallography and morphology, resulting in differences in aerodynamic performance. In the case of this particular combination, SX is sparingly soluble and MF is practically insoluble in water. Their low solubility affects the absorption and bioavailability perhaps by limiting dissolution in pulmonary fluids and slowing/decreasing therapeutic activity. If a combination product was available, it might be more efficacious as a composite formulation, give the ability of LABA to prime glucocorticosteroid receptors improves the activity of inhaled corticosteroids. Improved efficacy of inhaled same-particle combinations could be attributed to co-deposition within the lungs, since this synergy occurs at the cellular/molecular level. Thus, how to simplify the administration process, how to keep drugs co-deposited within lungs, and how to increase the solubility and bioavailability of both drugs in order to decrease the side effects are full of challenges.Co-amorphous systems are single-phase composite materials composed of two or more different molecules (API-API or API-excipient) typically formed via non-covalent bonding in a certain stoichiometric ratio. Co-amorphous systems have been used to stabilize the amorphous morphology. The extent to which APIs are mixed homogeneously at the molecular level depends on the miscibility of one API in the other.Thin film freezing (TFF) is an evolution of freezing process, which could be used to produce solid dispersion composed with more than one drug. The rapid freezing process prevents segregation and heterogeneity of the solutes. For preparation of pharmaceutical co-amorphous systems, thin film freezing (TFF) has been successfully applied to enhance the solubility and bioavailability of several poorly water-soluble APIs. Particle engineering technologies spray drying, also allow for the formulation of multiple actives into a single inhalable particle, although elevated temperature and drying energy may lead to instability of sensitive APIs. TFF may be more suitable for the compounds which are unstable during the drying process.ObjectiveThe objective of this study is to produce respirable co-amorphous fixed dose combination of salmeterol xinafoate and mometasone furoate by Thin Film Freezing (TFF), with or without adding excipients, in order to improve the solubility and bioavailability of both drugs and also realize the two drugs co-deposition. We hypothesize that the fixed dose combination would bring more convenient to patients and increase the drug efficacy.MethodsThere are three parts in this study.(1) The preformulation study of salmeterol xinafoate and mometasone furoate. We established an HPLC-UV method for in vitro drugs analysis, and found a chiral HPLC-UV method for identifying the chirality of raw SX. XRPD was employed to evaluate the morphology of the raw SX and raw MF. Melting point analysis of raw API materials were conducted using modulated temperature DSC. TGA was employed to study the thermal stability of APIs. The established HPLC-UV was used to investigate the solubility of SX and MF in different solvents.(2) The development and evaluation of co-amorphous fixed dose combination of salmeterol xinafoate and mometasone furoate. Thin Film Freezing technology was used to produce respirabile fixed dose combination of SX/MF dry powders. Thermal analysis of TFF-processed dry powders and each of their micronized components were conducted using modulated temperature DSC, and the glass transition temperature (Tg) and melting point were selected as the response variable to optimize the formulations. The crystallinity properties of the same set of samples were evaluated by wide angle XRPD. Karl Fischer moisture titration and loss on drying analysis (LOD) were employed to study the residues of water and organic reagents of fixed dose combinations. Scanning electron microscopy (SEM) and Brunauer-Emmet-Teller (BET) were employed to evaluate the surface morphology of both micronized and TFF powders. FTIR measurements were carried out to gain insight into possible molecular level interactions, between SX, MF and excipients in co-amorphous forms. Water sorption profiles were determined for brittle matrix TFF powders using Dynamic Vapor Sorption (DVS). A Next Generation Pharmaceutical Impactor (NGI) was used to determine the influence of DPI devices and to compare aerodynamic properties of co-amorphous TFF and crystalline micronized powders. However, the stability study was carried out by storing at ambient conditions for 6 months.(3) The pharmacokinetic study of co-amorphous fixed dose combination of salmeterol xinafoate and mometasone furoate in rats. HPLC-MS/MS was utilized to detect the concentrations of salmeterol xinafoate and mometasone furoate in rat plasma, lung tissue and BAL after the pulmonary delivery of TFF processed co-amorphous fixed dose powders and micronized physical mixtures. WinNonlin 2.1 was used to simulate the best-fit compartment model and to calculate and compare the pharmacokinetic parameters and bioavailability of both APIs in rats.Results(1) Established a rapid HPLC-UV method for in vitro drugs analysis and an easy chiral HPLC-UV method for the detecting the chirality of SX. However, raw SX is a mixture of racemates. XRPD patterns showed that the crystallography of raw materials were all crystalline. The melting points detected in this study were in accordance with literature. As shown in TGA results, the degradation temperature of SX and MF was 120℃ and 210℃, separately. It meant both APIs started to degrade at the melting point. SX, MF and pharmaceutical excipients were dissolved in a co-solvent mixture of tertiary butanol,1,4-dioxane, acetonitrile and purified water.(2) The fixed dose combinations were successfully produced by TFF. In brief, the ratio of salmeterol xinafoate to mometasone furoate was 50 to 220 by mass that corresponded to the clinical dose; while the ratio of APIs to excipient was controlled at a 1:1 molar ratio.The solid loading rate was 0.5%(w/v). Single glass transition temperatures (Tg) was assessed by differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD) results indicated that the fixed dose combinations were co-amorphous when processed without excipient or with lactose (Lac) and trehalose (Tre); glycine (Gly) and mannitol (Man) were partially remaining crystalline after TFF. The SEM showed that the fixed dose combinations exhibited large porous particles containing a sponge-like matrix, which appeared homogeneous and brittle. The SSA of TFF fixed dose combination was improved about 30 times. Fourier transform infrared spectroscopy (FTIR) found that even though a molecular mixture was achieved with all TFF formulations, no molecular interactions between the drugs were detected. The DVS suggests that the BMP SXMFLac and BMP SXMFTre were hygroscopic, while the others were not. Aerodynamic evaluation was carried out by next generation pharmaceutical impactor (NGI) with two marketed DPI devices Handihaler(?) and Miat monodose inhaler(?), which was effected by devices and excipients. For the same formulations, the FPF and MMAD were improved by working with Miat; while for the same device, the TFF SXMF and TFF SXMFGly performed better than others. Compared with the micronized mixtures, TFF powders performed better by working with Miat. Moreover, the dispersion of SX in TFF powders showed highly consistent with MF compared to micronized physical mixtures due to its molecular homogenous structure, suggesting that both APIs were co-deposited after inhaled in vitro. The XRPD patterns exhibited no changes in peak intensity of TFF SXMF and TFF SXMFTre over 6 month period for each composition, while TFF SXMFLac was slightly recrystallized at 294.21 indicating the peaks of SX. Based on the data observed above, TFF SXMF was selected for further in vivo study.(3) Following single dose insufflation into rats, both drugs followed 2-compartment model. After pulmonary administration with micronized SXMF mixtures(Reference), the AUCo-24h of SX in plasma and lung tissue were 124.656ngh/mL and 6.863μg·h/g; with TFF SXMF fixed dose combination, the AUCo-24h values of SX were 288.207ng-h/mL and 104.686μgh/g, which was significant increased separately. Similarly, the AUCo-24h of MF was increased as well. Following single dose of TFF SXMF fixed dose combination, the kio of SX was decrease from 0.353h-1 to 0.187h-1, indicating that the elimination rate of SX was slower and the lung tissue retention time was longer. Furthermore, the distribution ratio of SX and MF in rats was consistent, which showed the good performance of co-deposition.CONCLUSION(1) In this study, an amorphous fixed dose combination for co-deposition containing salmeterol xinafoate and mometasone furoate was successfully prepared by thin film freezing technology. Though no interactions were founded within formulations, better store stability was observed. These brittle particles exhibited better physicochemical characteristics, which were suitable for dry powder inhalation cooperated with marketed DPI device. The TFF processed combinations displayed more favorable aerodynamic properties as micronized blends in vitro, and the highly consistent performances of TFF powders suggested that both APIs were co-deposited in vitro.(2) We demonstrated that the fixed dose combination SX/MF displayed more favorable pharmacokinetic parameters in lung tissue and blood by performing higher AUCo-24h values. Moreover, TFF SXMF powders presented a significantly higher lung levels compared to micronized blend both in vivo.SIGNIFICANCE(1) We prepared respirable fixed dose combination sameterol xinafoate/mometasone furoate by TFF for the first time. Currently available products containing two APIs are produced by blending discrete micronized particles of both APIs with a carrier and loading into a device. However, there is no fixed dose combination product marketed or studied for inhalation containing SX and MF.(2) Co-amorphous system is becoming a hot topic recently. Normal amorphous formulation is composed of one drug and one excipient due to the limitation of traditional technics. We produced a respirable co-amorphous fixed dose combination of SX and MF for the first time, which only contained APIs and corresponded to the clinical dose. Additionally, this formulation strategy would improve convenience and compliance for patients.(3) Different from the traditional technics, a novel technology was chosen to prepare fixed dose combination for pulmonary delivery. The in vivo study proved that the lung levels of both APIs were significantly improved, and the drug retention time in lung tissue was prolonged as well. Furthermore, highly consistent performances of both APIs in the TFF formulations indicated that the goal of co-deposition was attained, which may increase the ability of the LAB A to prime glucocorticosteroid receptors.(4) Thin film freezing (TFF) is patented by Dr.Williams at University of Texas at Austin. The TFF technics has been successfully applied to enhance the solubility of several poor water-soluble APIs, including fenofibrate, danazol, tacrolimus and rapamycin. However, using TFF to produce a respirable co-amorphous fixed dose combination of two drugs is setting a precedent.