delivery system.

Description

The present invention relates to a preparation for the local delivery of drugs. Local delivery of drugs has been accomplished by conjugating a drug to biocompatible or biodegradable macromolecules, e.g. poly- saccharides, proteins, lectins including albumin and immuno- globulines, which have a particular receptor specificity. In this way the drug can be transferred to a particular part of the human body which is subject to treatment with the particular drug. For example, R.C. Oppenheim et al. discloses in U.S. Patent 4,107,288 a process for the preparation of drug containing gelatine particles having a diameter mainly below 500 nm which can be administered parenterally. Solid serum albumin spherules having 5 to 30 % by weight of an entrapped drug are disclosed by A.F. Yapel, Jr., in U.S. Patent 4,147,767. The spherules are particularly suited for intravenous injection into the human body whereafter the drug is released from the spherule in a biphasic manner having an initial fast-release phase followed by a slow release phase.

A method of preparing aqueous suspensions of drug containing spherules comprising a phospholipid has been described by A. Suzuki et al. in U.S. Patent 4,016,100. These spherules, which are suitable for injection as well as oral administration, give controlled release of the entrapped drug after administration.

Although the particles and spherules described above can be used to deliver a drug to a particular part of the body, e.g. the lungs or the liver, a local and site specific actively controlled release of the drug contained by said particles and spherules has not be achieved in the prior art. In a mammal, i.e. a human or ani¬ mal, the release of the drug contained by said particles and spherules is determined by the biological processes and functions of

the mammalian body, i.e. the biodegradation of the particles, and can not be influenced actively and/or in a site specific manner.

It is therefore not unlikely that while being transferred to the desired area in the mammalian body by the blood circulation, these particles and spherules may be partly inactivated or even disintegrated. Obviously this will give rise to serious consequences for the patient, especially when drugs are used which are highly toxic to the mammalian body. Consequently, the efficacy of the methods described above for treating a certain disorder can be con- sidered to be rather low.

In addition, the prior art does not provide a method for monitoring the release of a drug neither in space nor in time. Hence, the effective concentration of the drug in the desired area of the mammalian body can therefore not be determined. Biocompatible or biodegradable macromolecules labelled with solid gold particles, e.g. gold-albumin, have found application as cytochemical markers in electron microscopy. Solid gold particles bind the macromolecule irreversibly whereby the macromolecule generally preserves its specific biological activity. Because of their high electron density, these gold particles can be observed by electron microscopy enabling the detection of intercellulair loca¬ tions of the macromolecule. Such systems have been described by M. Horisberger et al., Histochem. 80, 1984, 13 - 18, and by Slot et al., Eur. J. Cell Biol. 38, 1985, 87 - 93. However, neither Horis- berger et al. nor Slot et al. do describe or suggest that these gold-albumin particles can be used as local drug delivery systems.

Particles prepared from biocompatible or biodegradable materials, which can be detected by ultrasonic imaging are known as well. These particles comprise so-called microparticles, micro- bubbles, microspheres or microcapsules containing gaseous components capable of reflecting ultrasonic waves. W0-9-H2.823 discloses a process for preparing such particles comprising the formation of water-dispersable, preferably proteinaceous, microcapsules having a liquid or solid core by conjugation of oil/water bubbles with bio- compatible or biodegradable materials, e.g. albumin, followed by the removal of at least some of said liquid or solid to create a micro- capsule containing a gas. The microcapsules are preferably 0.1 to

500 μm in diameter. In W0-9.112.823 it is neither described nor suggested that such particles can be used for the active and controlled delivery of a drug to a specific area of the mammalian body. The problems which are encountered when the above described systems are used for the local delivery of a drug can be summarized as follows:

1) the release of the entrapped drug from the local drug delivery system can not be controlled actively and/or in a site specific manner,

2) before the systems reach the area in the mammalian body to be treated they might be inactivated or even disintegrated, and

3) the release and/or the effective concentration of the drug in the area to be treated can not be determined, The present invention offers a solution for these problems by providing a local drug delivery system containing a drug as well as a method for the active and site specific alteration of the release properties of said local drug delivery system, once said delivery system has been administered to the mammalian body. According to the invention, this is carried out by means of electromagnetic and/or mechanical vibrations. The invention further provides such a method which enables the monitoring of said release.

The present invention therefore relates to a local drug delivery system comprising a) a local and site specific drug delivery system, comprising b) a material which reflects or absorbs or emits electromagnetic and/or mechanical vibrations enabling the monitoring of said material by imaging techniques and c) a drug. A local and site specific drug delivery system is intended to be a system comprising biocompatible or biodegradable materials, which is capable of transfering or carrying a drug to a specific area or site, e.g. an organ or organella, at which specific area or site said system releases said drug in an active and controlled manner enabling the interaction of said drug with said specific area or site, when -after administration of the drug delivery system to the human or animal body- said site is treated with electromagnetic

and/or mechanical vibrations.

In this application electromagnetic and/or mechanical vibra¬ tions are intended to comprise vibrations or waves, which are reflected or absorbed or emitted and propagated in the form of energy through a space or through a material medium. Examples of such vibrations or waves are cosmic rays, gamma rays, X-rays, ultra¬ violet-, visible and infrared waves, sound waves, e.g. microwaves and radiowaves, streams of sub-atomic particles, e.g. alpha-rays en beta-rays and photons, and the like. Preferably, said vibrations are not harmful to the mammalian body as will be clear to a man skilled in the art, although it is possible to use vibrations (radiation) which also have therapeutic value, e.g. in cytostatic treatment.

The expression imaging techniques is intended to encompass techniques by which said electromagnetic and/or mechanical vibra¬ tions can be detected or monitored, and such techniques will described hereinbelow and/or will be clear to a man skilled in the art. In principle, any usual imaging technique for use in medical procedures can be used to follow the drug, its concentration at specific sites of the body, and/or the release of the drug there¬ from.

Although the invention is not limited to this mechanism, preferably the interaction of the vibrations with the drug delivery system will lead to or trigger the degradation of the delivery system at the specific site treated with the vibrations, or make the delivery system more susceptible to biological degradation, thereby providing for the local and site specific release of the drug. Said degradation and thereby said release can then be followed by means of the abovementioned imaging techniques. It will furthermore be clear to a man skilled in the art that the site of the release of the drug can be controlled by controlling the vibrations, i.e. by only treating those sites at which release of the drug is desired. Furthermore, in most cases -and preferably- the rate of degradation and thereby the rate of release is controlled by the amount of vibrations used, i.e. by controlling the intensity or the time of the treatment.

The local and site specific delivery system will therefore

comprise a material that can interact with electromagnetic and/or mechanical vibrations, causing alteration of the release properties of said system. Said interaction preferably leads to an enhancement of the release properties, so that by means of the vibrations the release of the drug contained in said system can be effected in a local and site specific manner. For instance, the interaction of the vibrations can lead to or trigger the partial destruction of the walls of the delivery system, or make it more susceptible to bio¬ logical degradation, as described hereinabove. Although the preparation of the invention will usually comprise b) a material which reflects or absorbs or emits electro¬ magnetic and/or mechanical vibrations enabling the monitoring of said material by imaging techniques, it will be clear to a man skilled in the art that component b) can be omitted when component a) -i.e. the local and site specific drug delivery system- itself is made of a material that reflects or absorbs or emits electromagnetic and/or mechanical vibrations, enabling the monitoring of said system by imaging techniques.

Additionally, according to the invention, the release of the drug can be monitored without simultaneously altering the release properties of the drug delivery system, for instance when two types of vibrations are used, e.g. a first type for altering the release properties and a second type for the subsequent monitoring of the release of the drug. It is also possible to follow the biological release from the delivery system.

Furthermore, it is possible to alter the release properties and monitor the release of the drug at the same time, using the same or different vibrations for achieving these two objectives.

According the present invention the preparation described above is preferably administered by a catheter based intravasculair delivery system. Local intravasculair administration by means of a catheter is a common technique in medical practice. For example, catheters as double balloon, porous balloon, microporous balloon, stent in a balloon, hydrogel, dispatch and iontophoresis may be used.

For intravenous injection in mammals the preparation according the invention must be smaller than 10 μm because otherwise

they can not pass the capillary circulation of various organ systems. For direct intra arterial injections, however, the prepara¬ tion according the invention may be larger, although it is preferred that their size does not exceed 50 μm. Consequently, to ensure safe parenteral administration the size of the preparation according the invention is determined by their intended use (parenteral intra¬ venous or parenteral intra arterial).

Preferably, the present invention provides a preparation that comprises as constituent of component a) and/or as component b) a material that can be monitored by ultrasonic imaging and/or an ultrasonic contrast agent, respectively.

In the description of this application an ultrasonic contrast agent comprises a material, which is a chemical substance or compound, either in the gaseous, liquid or solid state, or a particle comprising biocompatible or biodegradable materials such as polysaccharides, proteins, lectins including albumin and immuno- globulines and which may be in the form of a microparticle, micro- bubble, microsphere or microcapsule, or a particle comprising syn¬ thetic or natural polymers, and the like, and which is capable of reflecting vibrations, preferably ultrasonic vibrations. This description of an ultrasonic contrast agent is, however, not intended to be limited to ultrasonic vibrations reflecting materials only, but also to include materials capable of reflecting or absorbing or emitting other electromagnetic and/or mechanical vibra- tions. The preparation of the present invention preferably reflects ultrasonic waves, which can be monitored by ultrasonic imaging.

Preferably, the preparation of the present invention comprises a material, wherein said material which reflects or absorbs or emits electromagnetic and/or mechanical vibrations, preferably ultrasonic vibrations, can be monitored by clinical 2 DEcho imaging, including Doppler flow, color Doppler and color tissue imaging methods as well as ultrasound imaging based on tech¬ niques using the high frequency imaging (Rf signal) by reflected backscatter, color imaging, Doppler imaging or phenomena based on frequency shifts and second harmonic imaging.

The preparation of the present invention can be used for inducing and monitoring local and site specific drug delivery for

use in medical procedures. The preparation releases a drug upon ir¬ radiation of said preparation with electromagnetic and/or mechanical vibrations and can be imaged ultrasonically. The preparation is in particular irradiated with ultrasonic waves in a predetermined area and can be imaged ultrasonically in an area including said pre¬ determined area. Consequently, the drug can be imaged ultrasonically in an area including said predetermined area enabling the determina¬ tion of the rate of the release of said drug as function of space and time. Preferably, the preparation of the present invention comprises albumine particles containing a drug. According to this embodiment, the albumine also serves as component b) . The albumine particles, when exposed to harmless ultrasonic vibrations at suffi¬ cient intensity or during a sufficient period, change their release properties, such as by degradation, thereby releasing the drug. Concurrently, the albumine particles as such as well as said release can be monitored by means of ultrasonic imaging techniques, using the same harmless ultrasonic vibrations - reflected or absorbed/emitted - that are used for changing the release properties. Because of these advantageous properties, which were not known from the prior art, albumine particles are preferred. Suitable albumine particles will be clear to a man skilled in the art on the basis of the present description, and are for instance descibed in the prior art mentioned hereinabove. According to another preferred embodiment, the preparation comprises solid gold albumin particles, such as the solid gold albumin particles described hereinabove, and at least one drug. According to this embodiment, the gold-component will serve as component b) , as will be clear to a man skilled in the art. The size of the albumine and/or solid gold albumin particles will be 1 - 1000 nm, preferably 5 - 100 nm and more preferably 10 - 20 nm. Depending on their use, i.e. intravenous or intra arterial, the particles will most preferably have a diameter no larger than 10 μm or 0 μm, respectively. The preparation of the present invention may also comprise preparations in the form or microparticles, microbubbles, micro- spheres or microcapsules and at least one drug. The size of these

θ microparticles, microbubbles, microspheres or microcapsules will preferably be 1 - 50 μm. Depending on their use, i.e. intravenous or intra arterial, the particles will most preferably have a diameter no larger than 10 μm or 50 μm, respectively. These microparticles, microbubbles, microspheres or micro¬ capsules will usually comprise as component b) a material preferably selected from the group comprising gases, aqueous solutions of a contrasting agent and optionally a drug, biocompatible and bio¬ degradable materials. Although in principle any drug compatible with the components a) and b) can be used as component c), the drug comprised by the above mentioned preparation is preferably elected from the group comprising oncological agents, viral vectors, growth factors, anti¬ biotics, antihypertensive drugs, calcium-instream inhibitors, anti- thrombosis agents and corticosteroids. The preparation may also be used to administer drugs, e.g. antineoplastic drugs, which are highly toxic to health as well as malignant tissue.

Although not limited thereto, the drug will be usually be contained inside the preparation or bound thereto, such as by covalent bonds, as will be known to a man skilled in the art.

The present invention also provides a method for treating specific sites in a mammal comprising the steps of: i. injecting a drug delivery system into a mammal to thereby altering the acoustic properties of a predetermined area, ii. optionally inducing the release of a drug from said drug delivery system by irradiating said system with electro¬ magnetic and/or mechanical vibrations, and iii. imaging ultrasonically an area including said predetermined area so that an image of said predetermined area is obtained and, when a drug is released, the rate of said release can be determined as function of space and time by said ultrasonic imaging.

By using the preparation of the present invention according to the method described above, drugs can be administered. These drugs may be selected from the group comprising oncological agents, viral vectors, growth factors, antibiotics, antihypertensive drugs, calcium-instream inhibitors, anti-thrombosis agents and

corticosteroids, although any drug known in the art may be selected. The preparation may also be used to administer drugs, e.g. antineoplastic drugs for the treatment of tumours, which are highly toxic to health as well as malignant tissue. The present invention also provides a method for monitoring the local release of a drug comprising changing of the release properties from an already injected drug delivery system as described hereinabove by irradiating said system with electro¬ magnetic and/or mechanical vibrations, and then imaging ultrasonically the area where the drug is released as function of space and time.

Additionally, the present invention provides a method for altering the release properties of an already administered local and site specific drug delivery system of the invention, in which said delivery system is treated with electromagnetic and/or mechanical vibrations, as described hereinabove. Preferably, the release properties are enhanced. Thus, the local and site specific drug delivery system containing a drug is administered to a mammal, such as by injection or another suitable method, whereafter it is trans- ferred to the area to be treated by biological mechanisms using the farmacological properties of the system. As soon as the local and site specific drug delivery system has arrived at the area to be treated with the vibrations, its release properties are altered through local and site specific irradiation with said electro- magnetic and/or mechanical vibrations, as described hereinabove.

According to a further embodiment, this method further comprises the monitoring of the release of the drug as described herein.

The present invention also provides a method for monitoring the delivery of a drug contained by a local and site specific drug delivery system of the invention in an area in a mammal which is subject to treatment with said drug, by using a suitable monitoring technique, e.g. NMR tomography, X-ray imaging, preferably ultrasonic imaging, enabling the determination of the effective concentration of said drug in space and time in the area which is subject to treatment with said drug.

Preferably, the electromagnetic and/or mechanical vibrations

used for altering the release properties of a local and site specific drug delivery system of the invention are also used for the monitoring the delivery of a drug contained by said local and site specific drug delivery system in an area in a mammal which is subject to treatment with said drug.

The present invention finally provides a method for monitoring the delivery of a drug contained by a local and site specific drug delivery system of the invention by forming an image of the area, which is subject to treatment with said drug and where- in the already administered local and site specific drug delivery system is already present, by using a suitable imaging technique, preferably ultrasonic imaging.

For these methods the same embodiments, preferences and advantages as described hereinabove with respect to the delivery system itself apply mutatis mutandis. Also, said methods are carried out on an already injected delivery system of the invention. Furthermore, according to specific embodiments of the methods and/or method-claims of the invention descibed hereinabove, no exclusive rights are claimed for the administration of the delivery system or the biological transport thereof to the specific area to be treated. According to further embodiments of said methods and/or method claims, also no exclusive rights are claimed are for the release of any drug contained in said system.

The following examples will further illustrate the present invention. It is, however, to be understood that these examples do not restrict the scope of the invention.

Example 1

Commercially available albumin microspheres having a diameter in the range of 5 to 30 μ were administered parenterally by direct intra arterial injection. In this particular example injections were conducted into the left atrium of a pig's heart. Continuous ultra¬ sonic imaging of the heart was performed during the experiment using a commercially available ultrasonic machine (Hewlett Packard Sonos 1000) .

The images were recorded on videotape. After 3 to 5 beats after injection an increased video intensity was observed in the

left ventricle and thereafter in the muscle of the heart which indicated the pressure of the albumin microspheres in this myocardium. This was also confirmed by an increased video intensity. After one to two hours the video intensity gradually decreased indicating the biodegradation of the albumin microspheres.

In Figure 1 the relation between acoustic pulse pressure and reflected backscatter is displayed when a 2.5 MHz transducer was used. Below 0.05 MPa (1 Mpa = 10° Pa - 10 atm.) the backscatter intensity was linearly related to the acoustic pressure. Above 0.05 Mpa, however, the backscatter remained constant at higher acoustic pressures showing that the albumin microspheres were destroyed.

Example 2

The experiment of Example 1 was repeated with a 3-75 MHz transducer from Hewlett Packard Sonos 1000 and a 5 Mhz transducer from Ving ed. Identical results were obtained, i.e. the microspheres were destroyed at the same pressures.

Example A closed tube containing water was placed in a water containing reservoir. A 2.5. 3-75 or a 5 Mhz transducer was placed in the container and acoustic pressure was applied. An image was visualized by using a television set and the image was subsequently videotaped. Reflections of both edges of the tube were visible which clearly showed the presence of the tube. Because both the container and the tube contained the same fluid, no contrast difference was observed.

Next, the tube was filled with water containing commercially available albumin gold particles having a diameter in the range of 10 to 20 nm and placed in the container. On applying acoustic pressure, the image showed a contrast difference between the water contained by the reservoir and that contained by the tube (Figure 2).