ANTIBODIES FOR DRUG DELIVERY(TARGETED DRUG DELIVERY SYSTEM

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this ppt describes about antibodies mediated site specific drug delivery in order to minimize side effects and to increase therapeutic efficacy of drug.

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ANTIBODIES FOR DRUG DELIVERY(TARGETED DRUG DELIVERY SYSTEM):

ANTIBODIES FOR DRUG DELIVERY( TARGETED DRUG DELIVERY SYSTEM) PSIT,KANPUR RajRahul Singh,M.pharm PSIT,KANPUR

WHAT IS ANTIBODY?:

WHAT IS ANTIBODY? ANTIBODIES(ALSO KNOWN AS IMMUNOGLOBULINS) ARE PROTEINACIOUS IN NATURE AND ARE PRODUCED IN RESPONSE TO AN INVASION OF FOREIGN SUBSTANCE IN THE BODY CALLED ANTIGEN. . Antibodies are of two types: 1. They are produced without apparent antigenic stimulate Natural antibodies = antigen stimulant. 2. Those arising only on exposure to certain antigens. Acquired antibodies = exposure and certain antigens .

STRUCTURE:

STRUCTURE ANTIBODIES ARE HEAVY (~150 KDa ), Y-SHAPED GLYCOPROTEINS COMPOSED OF TWO CHAINS :two long HEAVY or H CHAINS and two short LIGHT or L CHAINS. The end of these chains together constitutes a variable region (also known as ANTIGEN BINDING SITE) consisting of 110 to 130 amino acids. The amino acid sequence in the variable region gives antibody its specificity for binding to a variety of antigens.

Monoclonal antibodies:

Monoclonal antibodies MAbs produced from a single clone of B cells Monoclonal antibodies all have identical antigen-binding sites. Thus they all bind to the same epitope with the same affinity Mostly produced by fusing a B cell secreting the desired antibody with a myeloma cell capable of growing indefinitely in tissue culture

HYBRIDOMA TECHNOLOGY:

HYBRIDOMA TECHNOLOGY 1) Immunize animal (mouse or rabbit) 2) Isolate spleen cells (containing antibody-producing B cells) 3) Fuse spleen cells with myeloma cells (e.g. using PEG - polyethylene glycol) 4) Allow unfused B cells to die 5) Add HAT culture to kill unfused myeloma cells 6) Clone remaining cells (place 1 cell per well and allow each cell to grow into a clone of cells) 7) Screen supernatant of each clone for presence of the desired antibody (ELISA) 8) Grow the chosen clone of cells in tissue culture indefinitely. 9) Harvest antibody from the culture supernatant.

PowerPoint Presentation:

WHAT IS POLYCLONAL ANTIBODY? Polyclonal antibodies are a mixture of antibodies with different antigen binding sites that may bind to different epitopes or antigens of the immunizing agent with varying affinities. They may be of different antibody classes. The serum obtained from an immunized animal is referred to as a polyclonal antiserum. A polyclonal antiserum contains antibody to different epitopes and different antigens that were present in the immunizing inoculum .

MONOCLONAL ANTIBODIES AS ACTIVE TARGETING MOIETIES:

MONOCLONAL ANTIBODIES AS ACTIVE TARGETING MOIETIES Paul Ehrlich (1908)coined phrase “MAGIC BULLETS AND POISONED ARROWS” :use of antibodies to specifically target toxic substances to pathogens. Monoclonal antibodies recognize the protein (antigen) on the surface of the Cancer cell and lock onto it. NEED: To achieve a desired pharmacological response at a selected sites without undesirable interaction at other sites, there by the drug have a specific action with minimum side effects & better therapeutic index. Ex- in cancer chemotherapy and enzyme replacement therapy.

MONOCLONAL ANTIBODIES IN CANCER TREATMENT:

MONOCLONAL ANTIBODIES IN CANCER TREATMENT IMMUNOCONJUGATES Immunoconjugates combine the targeting power of mabs and cytotoxic activity of drugs IMMUNOCONJUGATES

MONOCLONAL ANTI ACT BY SEVERAL MECHANISM:

MONOCLONAL ANTI ACT BY SEVERAL MECHANISM ADCC(ANTIBODY DEPENDENT CELL MEDIATED CYTOXICITY) RADIOIMMUNOTHERAPY ADEPT(ANTIBODY MEDIATED ENZYME PRODRUG THERAPY) IMMUNOLIPOSOMES IMMUNOTOXINS ANTIBODY DRUG CONJUGATES

ADCC ::

ADCC : Immunoglobulin's clustered on the surface of the targeted cells and exposes its tail {F c} region, to be recognized by the Fc receptors present on the surface of the macrophages and neutrophils . This causes Lysis of tumor cell

RADIOIMMUNOTHERAPY :

RADIOIMMUNOTHERAPY RADIOIMMUNOTHERAPY Involves the use of radioactively conjugated murine antibodies against cellular antigens. Emitted radiation causes tumor cell lysis . More applicable to lymphomas as they are highly radiosensitive malignancies Radionuclide attached to antibody Usually ß-emitters.

ADEPT (Antibody mediated Enzyme prodrug therapy): :

ADEPT (Antibody mediated Enzyme prodrug therapy): An antibody developed against a tumor antigen is linked to a drug -activating enzyme and injected to the blood subsequent systemic administration of non-toxic agent or prodrug results in its conversion to a toxic drug & results in cytotoxic effect

IMMUNOLIPOSOMES: :

IMMUNOLIPOSOMES: These are antibody conjugated liposome's Liposome's can carry drugs or therapeutic nucleotides and when conjugated with monoclonal antibodies, deliver the entrapped drug or toxin specially to the target cells

IMMUNOTOXINS: :

IMMUNOTOXINS: Immunotoxins are proteins that contain a toxin along with an antibody that binds specifically to target cells. All protein toxins are work by enzymatically inhibiting protein synthesis. Various plant & biological toxins have been genetically fused/chemically conjugated with the antibodies that bind to cancer cells.

Antibody drug conjugates::

Antibody drug conjugates: Antibody drug conjugates are monoclonal antibodies ( mAbs ) attached to biologically active drugs by chemical linkers with liable bonds Reduces side effects and show wide therapeutic window Doxorubicin, Duanomycin , Chlorambucil etc. can be conjugated with monoclonal antibodies

PowerPoint Presentation:

Targeting antibodies with drugs involve the following steps: Identification of the antigen produced by the tumor cells. Production of antibody monoclonally against the identified antigen. Formation (or) producing drug antibody conjugate or complexes. These complexes concentrate at the tumor site and deliver the drug. Drug antibody conjugate advantage : There are several advantages when drugs are delivered as antibody conjugates. The conjugates can specifically reach the target cells without causing any damage to the normal tissue. The drug antibody conjugate could be expected to be the ideal agents for drug targeting in chemotherapy.

DRUG LOADING: :

DRUG LOADING: Generally, a higher number of drug molecules are attached to a single targeting antibody. But as the number of drug molecules attached per antibody molecule increases, the target binding activity of the antibody decreases. To overcome this problem, carriers like dextran , hydroxymethylpropylamineacrylamine (HPMA), and serum albumin can be used to attach more number of drug molecules per targeting antibody. Antibody with 2-3 drug molecules shown satisfactory tumour binding site

Bispecific antibodies: :

Bispecific antibodies: Bispecific antibodies It consists of two antibodies with specificity for distinct antigens and immune effectors Cell Of the 2 paratopes , one can Be directed against a tumor Antigen and other against a T-lymphocyte. The Fc region additionally binds to a Fc receptor present on a macrophage/a natural killer cell. This mechanism cause tumor cell lysis

Problems of delivery of monoclonal antibodies::

Problems of delivery of monoclonal antibodies: slow elimination of monoclonal antibodies from the blood poor vascular permeability low and heterogeneous tumor uptake Cross reactivity with normal tissues Metabolism of monoclonal antibody conjugates

PowerPoint Presentation:

May bind with the targeted epitopes present on other tissues, which may lead to the damage of normal cells Antibody-drug conjugates may induce their own immunogenicity and be removed from the system before interacting with the target Diseased cells may alter their expression of ligand thereby rendering targeting more difficult

PowerPoint Presentation:

Tumor uptake may be increased through administering high doses Use of certain agents to increase tumor vascular permeability Tumor retention of antibody conjugates may be improved by inhibition of metabolism, by using more stable linkages Alternatively, normal tissue retention may be decreases through the use of metabolisable chemical linkages inserted between the antibody and conjugated moiety

MABs in transporting therapeutic drugs across the blood–brain barrier:

MABs in transporting therapeutic drugs across the blood–brain barrier Transferrin receptor (TR) The function of the TR is to provide iron to cells. Drug targeting tothe TR can be achieved by using the endogenous ligand transferrin , or by using antibodies directed against the TR. Insulin receptor Pardridge et al. have extensively documented the use of the insulin receptor for the targeted delivery of drugs to the brain using specific antibodies directed against the IR (Coloma et al., 2000). For example, using the 83-14 mouse MAb against the human insulin receptor (HIR) in rhesus monkey, shows that total uptake of the MAb is 4%, which corresponds to 0.04%/g brain tissue 3 h after iv injection Liposomes coated with targeting molecules such as antibodies, Trojan Horses Liposomes (THL)

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