Aggregates with increased deformability, comprising at least three amphipats, for improved transport through semi-permeable barriers and for the non-invasive drug application in vivo, especially through the skin

The present application is a continuation of U.S. application Ser. No. 10/357,618 filed on Feb. 4, 2003, which claims the benefit of U.S. provisional application No. 60/417,847 filed on Oct. 11, 2002, each of which is incorporated herein by reference in its entirety.

The invention relates to aggregates with extended surface (extended-surface aggregates, ESAs) with increased deformability and improved barrier penetration capability, said ESAs being suspendable in a suitable liquid medium and comprising at least three amphipats (amphipatic components) and being capable to improve the transport of actives through semi-permeable barriers, such as the skin, especially for the non-invasive drug application in vivo by means of barrier penetration by such aggregates. The three amphipats include at least one membrane forming compound (MFC), which can form the membrane of said ESAs, and at least two membrane destabilising compounds (MDC₁ and MDC₂) differentiated by their capability of forming smaller aggregates (with no extended surfaces) by either themselves or else in combination with each other and/or characterized by their relatively high solubility in said suitable liquid medium. The ESAs are loaded with at least one biologically active compound, which can be one of the at least three amphipats.

The invention relates also to preparations comprising extended surface aggregates (ESAs), that can penetrate barriers even when the typical ESAs radius (when an ESA is considered to be spherical) is at least 40% (and preferably at least 50% or even more) greater than the average radius of a pore in the barrier before and after the ESAs have penetrated the barrier.

Administration of active ingredients frequently is limited by natural barriers, such as the skin, which prevent adequate absorption of the active molecules due to the low barrier permeability for such ingredients.

Availability and use of preparations that can overcome this barrier impermeability problem and allow non-invasive active ingredient administration would be advantageous in many cases. In humans and animals, for example, a percutaneous administration of such preparations would protect the active ingredients against decomposition in the gastrointestinal tract and possibly would result in a modified, therapeutically attractive distribution of the agent in the body; such non-invasive administration could also affect the pharmacokinetics of the active ingredient and permit less frequent and/or simpler disease treatment (G. Cevc. Exp. Opin. Invest. Drugs (1997) 6: 1887-1937.). In the case of plants, improved penetration through or into the cuticle could lower the concentration of active ingredient that is required for the desired effect and, in addition, could significantly decrease contamination of the environment (Price, C. E. (1981) in: The Plant Cuticle (D. F. Cutler, K. L. Alvin, C. E. Price, Publisher), Academic, New York, pp. 237-252).

Many methods for increasing the skin permeability have been discussed (see, for example, G. Cevc, 1997, op. cit.). Most prominent are jet injection (for a classical review see Siddiqui & Chien Crit. Rev. Ther. Drug. Carrier Syst. (1987) 3: 195-208), the use of electrical (Bumette & Ongpipattanakul J. Pharm. Sci. (1987) 76: 765-773) or accoustic (Vyas et al., J Microencapsul (1995) 12: 149-54) skin perturbation or else the use of chemical additives, such as certain solvents or surfactants. Such chemicals generally act as the skin permeation enhancers by increasing the partitioning and/or diffusivity of the active ingredient in the skin lipids.

Most often used permeation enhancers are non-ionic short or long-chain alcohols and uncharged surfactants etc., anionic materials (particularly fatty acids), cationic long-chain amines, sulfoxides, as well as various amino derivatives, and amphoteric glycinates and betaines. None of these, however, solves the problem of active ingredient transport through the skin or mucous barrier to general satisfaction.

An overview of the measures, which have been used for the purpose of increasing active ingredient penetration through plant cuticles, is summarised in the work of Price (1981, op. cit.).

Epidermal use of one or several amphipatic substances in the form of a suspension or an O/W or W/O emulsion, has also brought about too little improvement. An extensive review written by G. Cevc (1997, op. cit.) explains why liposomes, at best, can modify drug retention time or stability on the skin and or improve transcutaneous drug transport by partly occluding the skin surface. Japanese patent application JP 61/271,204 A2 (86/27 1204) provides an example for stabilizing effect of liposomes on the skin, relying on hydroquinone glucosidal as stabilizing material.

The use of lipid vesicles loaded with an active ingredient combined with a gel-forming agent in the form of “transdermal patches” was proposed in WO 87/1938 A1. However, the ability of the active ingredient to permeate the skin was not appreciably increased. Massive use of permeation-promoting polyethylene glycol and of fatty acids, together with lipid vesicles, was required by Gesztes and Mezei (1988, Anesth. Analg. 67, 1079-1081) to attain only a moderate local analgesia with lidocaine-containing formulations applied for several hours under occlusion on the skin.

U.S. Pat. No. 6,193,996 describes a pressure sensitive skin adhesive that uses skin permeation enhancers. European Patent applications EPA 102 324 and EPA 0 088 046, and U.S. Pat. No. 4,619,794, all by H. Hauser, describe methods for preparing unilamellar vesicles using a single membrane destabilising component. The vesicles may be used as carriers for different drugs. However, such vesicles are not used on the skin or for transport through semi-permeable barriers. European Patent application EPA 0 152 379 by Muntwyler and Hauser similarly describes the preparation of unilamellar vesicles. However, these vesicles often need to be separated from the residual multilamellar liposomes, facilitated by the presence of charged drugs, for final use of the former for treating human or animal body. The authors also point the potential need to neutralize the drug during vesicle preparation to obtain the desired unilamellar liposomes. Further, such vesicles are not used for transport of drugs through a semi-permeable barrier.

European patent EP 0475 160, corresponding U.S. Pat. No. 6,165,500 and Canadian patent 2,067,754, all with the title “Preparation for the application of agents in mini-droplets”, describe special preparations related to the suspensions described in this application. These documents report the use of different agents associated with minuscule droplets or, in particular, with the vesicles consisting of one or a few membrane-like amphiphile assemblies for overcoming semi-permeable barriers including the skin. These references describe preparations having a single membrane destabilising component. WO 98/17255 and AU 724218, likewise, describe vesicles for the transport of a variety of drugs through the skin.

In two relatively early reports on dermal liposomal tetracaine (Gesztes A, Mezei M. “Topical anesthesia of the skin by liposome-encapsulated tetracaine.” Anesth. Analg. (1988), 67:1079-1081) and lidocaine (Foldvari M, Gesztes A, Mezei M. “Dermal drug delivery by liposome encapsulation: clinical and electron microscopic studies.” J Microencapsul (1990), 7:479-489), Mezei\'s group reported anaesthetic performance of such locally used drugs and corresponding autoradiography data. Drug was found in the epidermis and in dermis of humans and guinea pigs when the skin was treated under an impermeable (occlusive) coating with the liposome-encapsulated anaesthetics. The formulations always contained multilamellar soybean phosphatidylcholine vesicles. However, the reports demonstrate no liposome-mediated drug transport through the skin. (Foldvari M. “In vitro cutaneous and percutaneous delivery and in vivo efficacy of tetracaine from liposomal and conventional vehicles.” Pharm Res (1994) 11:1593-1598) and with an additional oily ingredient (Foldvari M. “Effect of vehicle on topical liposomal drug delivery: petrolatum bases.” J Microencapsul (1996), 13:589-600). This conclusion is supported by the fact that the reported maximum transported drug dose (5.3%) was more than 20-times higher than the reported transported lipid dose (0.2%) (Foldvari, 1994). Further, Foldvari\'s formulations evidently were not optimised for adaptability but rather for best drug retention/release.

P. Gonzalez, M. E. Planas, L. Rodriguez, S. Sanchez, and G. Cevc in an article on “Noninvasive, percutaneous induction of topical analgesia by a new type of drug carriers and prolongation of the local pain-insensitivity by analgesic liposomes” (Anesth. Analg. (1992), 95: 615-621) report the results of investigations with surfactant-containing formulations, typically loaded with lidocaine (2%, as a free base) in a mixed lipid 4-8% suspension (w/v). Lipid aggregates were prepared from a 4/1 mol/mol phosphatidylcholine/sodium cholate mixture, starting with an ethanolic lipid solution (7-3 w-% EtOH in the final product) for easier manufacturing. However, all the tested suspensions were reported by Planas et al. to be unstable. Further, Planas et al. failed to disclose how a stable drug formulation could be prepared, which would be suitable for transdermal drug delivery.

Peters and Moll (1995) (“Pharmacodynamics of a liposomal preparation for local anaesthesia”. Arzneimittelforschung (1995), 45:1253-6, describe permeation of a topically applied drug through the skin. The permeation is enhanced by ethanol, is based on diffusion, and is achieved under occlusion.

Carafa and colleagues describe the use of surfactant-based, phospholipid-free vesicles (Carafa et al., 2002 (“Lidocaine-loaded non-ionic surfactant vesicles: characterisation and in vitro permeation studies.” Int J Pharm (2002), 231:21-32). However, such vesicles do not simultaneously include both a MFC and a MDC, and are unsatisfactory.

Applicants have discovered that incorporation of a surfactant into a bilayer membrane that is built from another less soluble amphipat, such as a phospholipid, can increase the flexibility of the resulting complex membrane. This promotes the capability of complex aggregates in the form of droplets covered by the bi-component membranes to cross pores in a semi-permeable barrier that otherwise would prevent comparably large aggregates from crossing. Further, the use of aggregates with highly deformable membrane coating can mediate agent transport into and/or across mammalian skin. This can be achieved by selecting a surfactant, which is a membrane destabilising component (=MDC), and a less soluble amphipat, which is the membrane forming component (=MFC), so as to maximize the mixed membrane flexibility and the mixed aggregate stability. Further the surfactant can be selected to increase bilayer membrane adaptability. Patent applications by applicant, especially WO 92/03122 and WO 98/172550 describe basic requirements for the use of lipid/surfactant mixtures for transbarrier transport.

It is an objective of the invention to provide preparations that can transport active ingredients through a barrier in the form of vesicles or other extended surface aggregates (ESAs) comprising said actives, said preparations having improved permeation capability through semi-permeable barriers.