Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1995-06-07
2002-09-03
Jaworsid, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C424S450000, C424S009510
Reexamination Certificate
active
06443898
ABSTRACT:
BACKGROUND OP THE INVENTION
1. Field of the Invention
This invention relates to therapeutic delivery systems, and more specifically, to gaseous precursor-containing microspheres comprising a therapeutic compound. The invention further relates to methods for employing such microspheres as therapeutic delivery systems.
2. Background of the Invention
Targeted therapeutic delivery means are particularly important where the toxicity of a drug is an issue. Specific therapeutic delivery methods potentially serve to minimize toxic side effects, lower the required dosage amounts, and decrease costs for the patient. The present invention is directed to addressing these and/or other important needs in the area of therapeutic delivery.
A variety of imaging techniques have been used for detection and diagnosis of diseases in animals and humans. X-rays represent one of the first techniques used for diagnostic imaging. The images obtained through this technique reflect the electron density of the object being imaged. Contrast agents, such as barium or iodine, have been used over the years to attenuate or block X-rays such that the contrast between various structures is increased. X-rays, however, are known to be somewhat dangerous, since the radiation employed in X-rays is ionizing, and the various deleterious effects of ionizing radiation are cumulative.
Another important imaging technique is magnetic resonance imaging (MRI). This technique, however, has various drawbacks, such as expense and shear size of an MRI scanner rendering it stationary which prohibits portable examination. In addition, MR1 is not available at many medical centers.
Radionuclides, employed in nuclear medicine, provide a further imaging technique. In employing this technique, radionuclides such as technetium labeled compounds are injected into the patient, and images are obtained from gamma cameras. Nuclear medicine techniques, however, suffer from poor spatial resolution and expose the animal or patient to the deleterious effects of radiation. Furthermore, the handling and disposal of radionuclides is problematic.
Ultrasound is another diagnostic imaging technique which is unlike nuclear medicine and X-rays since it does not expose the patient to the harmful effects of ionizing radiation. Moreover, unlike magnetic resonance imaging, ultrasound is relatively inexpensive and may be conducted as a portable examination. In using the ultrasound technique, sound is transmitted into a patient or animal via a transducer. When the sound waves propagate through the body, they encounter interfaces from tissues and fluids. Depending on the acoustic properties of the tissues and fluids in the body, the ultrasound sound waves are partially or wholly reflected or absorbed. When sound waves are reflected by an interface they are detected by the receiver in the transducer and processed to form an image. The acoustic properties of the tissues and fluids within the body determine the contrast which appears in the resultant image.
Advances have been made in recent years in ultrasound technology. However, despite these various technological improvements, ultrasound is still an imperfect tool in a number of respects, particularly with regard to the imaging and detection of disease in the liver and spleen, kidneys, heart and vasculature, including measuring blood flow. The ability to detect and measure these regions depends on the difference in acoustic properties between tissues or fluids and the surrounding tissues or fluids. As a result, contrast agents have been sought which will increase the acoustic difference between tissues or fluids and the surrounding tissues or fluids in order to improve ultrasonic imaging and disease detection.
The principles underlying image formation in ultrasound have directed researchers to the pursuit of gaseous contrast agents. Changes in acoustic properties or acoustic impedance are most pronounced at interfaces of different substances with greatly differing density or acoustic impedance, particularly at the interface between solids, liquids and gases. When ultrasound sound waves encounter such interfaces, the changes in acoustic impedance result in a more intense reflection of sound waves and a more intense signal in the ultrasound image. An additional factor affecting the efficiency or reflection of sound is the elasticity of the reflecting interface. The greater the elasticity of this interface, the more efficient the reflection of sound. Substances such as gas bubbles present highly elastic interfaces. Thus, as a result of the foregoing principles, researchers have focused on the development of ultrasound contrast agents based on gas bubbles or gas containing bodies and on the development of efficient methods for their preparation.
Ryan et al., in U.S. Pat. No. 4,544,545, disclose phospholipid liposomes having a chemically modified cholesterol coating. The cholesterol coating may be a monolayer or bilayer. An aqueous medium, containing a tracer, therapeutic, or cytotoxic agent, is confined within the liposome. Liposomes, having a diameter of 0.001 microns to 10 microns, are prepared by agitation and ultrasonic vibration.
D'Arrigo, in U.S. Pat. Nos. 4,684,479 and 5,215,680, teaches a gas-in-liquid emulsion and method for the production thereof from surfactant mixtures. U.S. Pat. No. 4,684,479 discloses the production of liposomes by shaking a solution of the surfactant in a liquid medium in air. U.S. Pat. No. 5,215,680 is directed to a large scale method of producing lipid coated microbubbles including shaking a solution of the surfactant in liquid medium in air or other gaseous mixture and filter sterilizing the resultant solution.
WO 80/02365 discloses the production of microbubbles having an inert gas, such as nitrogen; or carbon dioxide, encapsulated in a gellable membrane. The liposomes may be stored at low temperatures and warmed prior and during use in humans. WO 82/01642 describes microbubble precursors and methods for their production. The microbubbles are formed in a liquid by dissolving a solid material. Gas-filled voids result, wherein the gas is 1.) produced from gas present in voids between the microparticles of solid precursor aggregates 2.) absorbed on the surfaces of particles of the precursor, 3.) an integral part of the internal structure of particles of the precursor, 4.) formed when the precursor reacts chemically with the liquid, and 5.) dissolved in the liquid and released when the precursor is dissolved therein.
In addition, Feinstein, in U.S. Pat. Nos. 4,718,433 and 4,774,958, teach the use of albumin coated microbubbles for the purposes of ultrasound.
Widder, in U.S. Pat. Nos. 4,572,203 and 4,844,882, disclose a method of ultrasonic imaging and a microbubble-type ultrasonic imaging agent.
Quay, in WO 93/05819, describes the use of agents to form microbubbles comprising especially selected gases based upon a criteria of known physical constants, including 1) size of the bubble, 2) density of the gas, 3) solubility of the gas in the surrounding medium, and 4) diffusivity of the gas into the medium.
Kaufman et al., in U.S. Pat. No. 5,171,755, disclose an emulsion comprising an highly fluorinated organic compound, an oil having no substantial surface activity or water solubility and a surfactant. Kaufman et al. also teach a method of using the emulsion in medical applications.
Another area of significant research effort is in the area of targeted drug delivery. The methods and materials in the prior art for introduction of genetic materials to, for example, living cells is limited and ineffective. To date several different mechanisms have been developed to deliver genetic material to living cells. These mechanisms include techniques such as calcium phosphate precipitation and electroporation, and carriers such as cationic polymers and aqueous-filled liposomes. These methods have all been relatively ineffective in vivo and only of limited use for cell culture transfection. None of these methods potentiate local release, delivery and integration of genetic material to the tar
Fritz Thomas A.
Matsunaga Terry
Ramaswami VaradaRajan
Unger Evan C.
Wu Guanli
Imarx Pharmaceutical Corp.
Jaworsid Francis J.
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
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