Presentation on theme: "BONE MARROW TARGETING AND TARGETING TO LYSOSOMAL DISEASESBy SOMESHWAR.K SOMESHWAR.K M.PHARM. M.PHARM. II - SEMESTER II - SEMESTER Department of Pharmaceutics."— Presentation transcript:
BONE MARROW TARGETING AND TARGETING TO LYSOSOMAL DISEASESBy SOMESHWAR.K SOMESHWAR.K M.PHARM. M.PHARM. II - SEMESTER II - SEMESTER Department of Pharmaceutics Department of Pharmaceutics University College of Pharmaceutical Sciences, KAKATIYA UNIVERSITY Warangal
CONTENTS Introduction Physiology of bone marrow Bone marrow targets for drug delivery Colloidal carriers for bone marrow targeting Nanospheres / nanoparticles Liposomes Lysosomal storage diseases Targeting exogenous enzymes Conclusion References
INTRODUCTION The main problems currently associated with systemic drug administration are: 1.Even biodistribution of pharmaceuticals throughout the body; 2.The lack of drug specific affinity toward a pathological site; 3. The necessity of a large total dose of a drug; 4. Non-specific toxicity and other adverse side-effects.
Drug targeting Targeted drug delivery (TDD) is an event where, a drug-carrier complex or conjugate delivers the drug(s) exclusively to preselected cells in a specified manner. TDD implies for selective and effective localization of pharmacologically active moiety at a predetermined target in a therapeutic concentration, while restricting its access to non-target normal cellular linings, thus minimizing the toxic effects and maximizing therapeutic index.
The concept of drug targeting includes a coordinated behavior of three components: (a) Drug; (b) Targeting moiety - cell, tissue, inside of a cell, etc. (c) Pharmaceutical carrier - colloidal carriers, cellular carriers, polymer based systems, macromolecular carriers.
LEVELS OF TARGETING Passive targeting Inverse targeting Active targeting - First order targeting - Second order targeting - Third order targeting Physical targeting Dual targeting
PHYSIOLOGY OF BONE MARROW Bone marrow is the flexible tissue found in the hollow interior of bones. In adults, marrow in large bones produces new blood cells. It constitutes 4% of total body weight, i.e. approximately 2.6 kg in adults. There are two types of bone marrow: - Red marrow - Yellow marrow
Red bone marrow consists of hematopoietic or blood forming tissue which produces white blood cells and red blood cells. Within the marrow haemopoietic progenitor cells at various stages of development replenish the peripheral blood cells populations. The major vascular constituents of bone marrow are called as sinuses. These blood vessels are relatively large forming a barrier i.e. Marrow Blood Barrier (MBB) between the Hematopoietic compartment and the circulation. The walls of MBB consists of continuous endothelium and a discontinuous adventitial cell layer. The MBB serves to control cellular traffic in and out of the marrow.
BONE MARROW TARGETS FOR DRUG DELIVERY The RES of organism is usually very effective in removing small foreign colloidal particles administered intravenously. The kupffer cells of liver and the macrophages of the spleen constitute 80-95% of phagocytic cells of this system and it is here that the particles are normally deposited. For the particles to reach the bone marrow this uptake by kupffer cells and macrophages should be prevented. 1. Reticuloendothelial system (RES)
The endothelium of bone marrow sinusoids removes particulate materials from the blood. The endothelium is not only capable of phagocytic uptake and storage of particles but also provides for the transmural passage of particulate material to the extra vascular spaces where the particles are phagocytosed by central macrophages. 2. Sinusoidal capillaries
. Capillary endothelial barrier
MARROW (STEM CELL) TRANSPLANTATION The homing of progenitor cells to the marrow has provided the basis for treatment of certain diseases of haemopoietic origin by bone marrow transplantation. Certain genetic diseases which are characterised by a generalized absence of a specific enzyme such as adenosine deaminase (ADA) deficiency in severe combined immunodeficiency, and glucose cerebrosidase deficiency in Gaucher’s disease are treated.
COLLOIDAL CARRIERS FOR BONE MARROW TARGETING The ability of the bone marrow to remove the particulate matters from the circulation, opens up an idea for the delivery of therapeutic agents by means of colloidal drug carrier systems such as Liposomes Nanospheres Emulsions Microspheres
With all these carrier systems a high proportions of the dose still reaches the liver and spleen within few minutes after intravenous administration. Since intravenously administered colloidal particles are normally removed efficiently by RES cells of liver and spleen, only a small fraction of these particles reaches the bone marrow. Modification of the surfaces of the particles by a polymer in order to provide a hydrophilic barrier minimize the uptake of the plasma components. E.g. poly(ethylene oxide) (PEO), polysorbate (Tween-80) and lauryl ethers (Brij-35).
NANOSPHERES / NANOPARTICLES Poloxomer 407 Non-ionic block copolymer. It contains a central block of hydrophobic polyoxypropylene ( POP) flanked by blocks of hydrophilic polyoxyethylene (POE). Polystyrene microspheres are surface labeled with iodine- 131.these labeled particles are incubated for 24hours with a 2% w/v solution of poloxomer 407. This provides a coating layer over the particles
Both the coated and uncoated particles were administered intravenously to rabbits. The blood samples were taken and radioactivity was measured using gamma counter. Gamma camera scans of rabbits clearly demonstrated that the uncoated polystyrene particles were largely taken up by liver and spleen after injection while the Poloxomer 407 coated particles were apparently deposited in bone marrow. The uptake of uncoated particles by liver/spleen region occurred rapidly and efficiently with 90% of the particles being deposited in these organs within 2 min. The Poloxomer 407 coated particles showed a marked decreased liver/spleen activity.
Polyalkylcyanoacrylate nanoparticles (Gibaud Et al., 1999) Doxorubicin & stimulating growth factor (rhG-CSF) are the model compounds Histological studies showed rapid capture of nanoparticles by bone marrow macrophages as soon as 15 min after injection Doxorubicin nanoparticles administered were more toxic than free doxorubicin on all blood and marrow cells
LIPOSOMES Phospholipids vesicles (Liposomes) have been widely investigated as potential carriers for drugs, genes, proteins because their capsular structure permits encapsulation of various therapeutic agents. Advantage of using Liposomes as drug delivery carriers is that their pharmacokinetics can be controlled by modifying surface characteristics. Liposomes composed of equimolar amounts of cholesterol and either saturated phospholipids or sphingomyelin exhibited low tendency for accumulation in kupffer cells following intravascular administration.
Their uptake from blood to spleen and bone marrow remains relatively high. 25% of the injected dose of vesicles, formed from equimolar amounts of cholesterol and disteroyl phosphatidylcholine, were localized in rat bone marrow 72 hours post intravenous administration. Immunoliposomes Liposomes appended with antibodies or their fragments, as target oriented moieties are known as immunoliposomes. Immunoliposomes bearing poly-(ethylene glycol)- coupled monoclonal antibody linked via cleavable disulphide bond can be used for ex vivo applications as sorting of hematopoietic stem cells
LYSOSOMAL STORAGE DISEASES Lysosomal storage diseases (LSDs) are a group of approximately 40 rare inherited metabolic disorders that result from defects in lysosomal function. LSDs are caused by lysosomal dysfunction usually as a consequence of deficiency of a single enzyme required for the metabolism of lipids, glycoproteins (sugar containing proteins) or mucopolysaccharides. Like other genetic diseases, individuals inherit lysosomal storage diseases from their parents. Although each disorder results from different gene mutations that translate into a deficiency in enzyme activity, they all share a common biochemical characteristic – all lysosomal disorders originate from an abnormal accumulation of substances inside the lysosome.
Based on the chemical nature of the accumulating materials LSDs are categorized into: Lipid storage disorders (Sphingolipidoses) - Sphingolipidoses are caused by genetic defects in a series of lysosomal enzymes and other proteins essential for the catabolism of sphingolipids. E.g. Gaucher’s disease, Niemann -Pick disease, Fabry’s disease, Tay-sach’s disease. Mucopolysaccharidoses - Mucopolysaccharidoses are caused by genetic enzymatic defects in the degradation of carbohydrate chains of glycosaminoglycans. E.g. Hurler Syndrome, Hunter syndrome, Mucolipidosis. Glycogen storage disorders - Glycoprotein disorders result from defects in lysosomal hydrolases. E.g. Pompe disease, Sialidosis.
DISEASESIGNS AND SYMPTOMS MAJOR LIPID ACCUMULATION ENZYME DEFECT Faber’s disease Mental retardation, dermatitis ceramideceramidase Gaucher’s disease Spleen and liver enlargement, erosion of long bones glucoceribrosideGlucoceribroside β- glucosidase Niemann - pick disease Spleen and liver enlargement sphingomyelinsphingomyelinase Fabry’s disease Reddish purple skin rashes, kidney failure ceramidetrihexosideCeramidetrihexoside α- galactosidase Tay-sach’s disease Red spot in retina, blindness, muscular weakness gangliosideHexosaminidase A Principal manifestations, stored lipids in sphingolipidoses
TARGETING EXOGENOUS ENZYMES Direct the major portion of enzymes to the storage cells. Intracellular trafficking of the enzyme.
Conclusion Improvement of existing approaches to diagnosis and treatment of various diseases involving bone marrow. Combination with gene delivery and controlled expression of enzymes and carrier proteins is a promising strategy.
References S.P.Vyas and Roop K. Khar; targeted & Controlled drug delivery: Novel Carrier Systems, S.P.Vyas and V.K.Dixit; pharmaceutical biotechnology, James Swarbrick and James C.Boylan; Encyclopedia of pharmaceutical technology; third edition; volume2, Garret M. Ihler; methods of drug delivery.
S.M. Moghimi; Exploiting bone marrow microvascular structure for drug delivery and future therapies; Advanced Drug Delivery Reviews 17 (1995) 61-73, P.B. Malafaya, G.A. Silva, E.T. Baran, R.L. Reis; Drug delivery therapies I: General trends and its importance on bone tissue engineering applications; Current Opinion in Solid State and Materials Science 6 (2002) 283–295