Peptide & Proteins

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INTRODUCTION• Proteins and peptides are most abundant

components of biological cells not onlystructural components but also functionalmoieties.

• Amino acids linked together in a sequentialmanner by peptide bond resulting theformation of protein.

INTRODUCTION• PROTEINS : Proteins are the large

organic compounds made of amino acidsarranged in a linear chain and joinedtogether by polypeptide bonds.

• PEPTIDES: These are short polymersformed from the linking, in a definedorder of amino acids.

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STRUCTURE OF PROTEINThere are four types.

Primary structure- The amino acid sequence.

Secondary structure- Regularly repeating local structures

stabilized by hydrogen bond.

Tertiary structure-Three dimensional structure of

polypeptide

Quaternary structure-The structure formed by several

protein molecules (polypeptide chains).

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Classification of ProteinsAccording to their biological roles

Transport proteins- i.e. Haemoglobin oferythrocytes

Contractile or Motile proteins- i.e. Actin andMyosin

Structural proteins- i.e. Collagen in bones Defense proteins- i.e. Immunoglobulin's and

Antibodies Regulatory proteins- i.e. insulin Nutrient and storage proteins -i.e. Ovalbumin

WHY PROTEIN AND PEPTIDE DRUGS ?

• The protein and peptides are veryimportant in biological cells.

• Lack of proteins and peptides causesdiseases like Diabetes mellitus.–Diabetes mellitus is caused due to

the lack of protein called INSULIN.

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Advantages of protein & peptide DDS

Erythropoietin used for production of RBC. Tissue plasminogen activator is used for Heart

attack, Stroke. Oxytocin maintain labor pain. Bradykinin increases the peripheral circulation. Somatostatin decrease bleeding in gastric ulcer. Gonadotropin induce ovulation. Insulin maintain blood sugar level.

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Advantages of protein and peptide drugs

The mode of delivery is convenient, i.e., eye drops. Systemic absorption is extremely rapid. Avoid first-pass metabolism. The formulation can be designed to prolong drugaction and/or reduce drug concentrations to achieveconsistent drug action with least side effects. Drug delivery can be controlled precisely.

DISADVANTAGES OF PROTEIN AND PEPTIDE

• Large molecular size• Susceptibility to enz. Degradation• Short plasma half life• Immunogenicity• Aggregation• Denaturation

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Stability problems:(in vivo – in the body)

Elimination by B and T cellsProteolysis by endo/exo peptidasesSmall proteins filtered out by the kidneys very

quicklyUnwanted allergic reactions may develop

(even toxicity)Loss due to insolubility/adsorption

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DRUG DELIVERY CLASSIFICATION

Pulmonary Parenteral Transdermal

Implants Ocular Nasal

Miscellaneous Oral

Route of Administration

PEGylation Pro-drug Polymer depot

Drug Modification

Drug Delivery

Protein &peptide Drug Delivery

ROUTES OF ADMINISTRATION• PARENTERAL NON PARENTERAL

I.M ORALI.V BUCCAL

S.C NASALRECTALTRANSDERMALPULMONARY

PARENTRAL ROUTES

• parentral route is most efficient way for systemicdelivery of proteins and peptides

• This is the best choice to achieve therapeuticactivity.

• Mainly 3 routes of administration are used.

INTRAVASCULAR

INTRAMUSCULAR

SUBCUTANEOUS

Advantages &Disadvantages • Advantages

– Fast absorption

– Avoid First pass effect.

– Route of delivery for 95% of proteins• Disadvantages

– Short duration of their biological action

– Stimulate immunogenic response

– Problems with overdosing, necrosis– Local tissue reactions/hypersensitivity– Everyone hates getting a needle

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IV route• Advantages: Drugs that are highly

metabolized and are highly bound totissues by IM route are basically given bythis route.

• EX: INSULIN, INTERFERONS,ANTIBIOTICS.

• Disadvantages: Causes pain, tissuenecrosis and thrombopenia.

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Intramuscular route:• The drug is injected in the muscle. Various drugs

that are used for making depots are alsoadministered by this route.

• Advantages: Drugs that are administered for makingdepots and Better bioavailability for proteinbound drugs.

• Disadvantages: This route is not used for drugs thatare metabolized at the site of administration.

• Ex. of the drugs given by this route are LHRH, GH &LONG ACTING INSULIN

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Subcutaneous route:• Drugs are administered under the fold of skin. In

case of proteins and peptides, implantedpolymeric devices are used. These devices aremade by crosslinking the polymers and thesepolymers must be biocompatible andbiodegradable.

• Examples: Poly(d,l- lactide co-glycoside), Poly• lactic acid Some of the drugs used are

ACTH, CALCITONIN, INSULIN, BOVINE19

Parenteral drug delivery systems:

• Polymer based drug delivery system.• Liposome based drug delivery system.• Hydro gel based drug delivery system.• Emulsion based drug delivery system.• Pumps :

1) Implantable infusion pumps2) Mechanical pumps

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Polymer based drug delivery system:

• Polymers are used as carriers in this drugdelivery system.

• Characters of polymers:

• It should be biodegradable.• It should be bio compatible.• And non-toxic.• Two types of polymers are used widely• 1)natural polymers• 2)synthetic polymers

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Liposome based drug delivery:

• Liposome's are microscopic vesicles composed ofone or more aqueous compartments.

• Liposome’s in Proteins delivery :• Example: Lecithin used in controlled drug release.• Liposome’s in peptide drug delivery:• Bleomycin : A peptide with anti tumor activity,

reduces normal tissue toxicity.• Negatively charged liposome's produces a

prolonged hypoglycemic effect in diabetic drugs,which are injected by subcutaneous injection.

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Advantages of liposome drug delivery system

• Soluble in both organic and aqueous media.• Liposome’s are important for targeting drugs

directly to the liver, and brain. Lipsosomeseasily crosses blood brain barrier.

• Disadvantages:– Less stable , easily susceptible to oxidation.

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Hydro gel based drug delivery system:

• Hydro gels are polymers which have theability to swell in water . Biodegradablehydro gels are used, due to itsbiocompatibility .

• Disadvantage: Difficulty to achievedegradation.

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Emulsions based delivery:

• Emulsions can be used for parenteraldrug delivery of proteins and peptidesused to prolong the release of drug.

• e.g. subcutaneous administration of muramyldipeptide in a w/o emulsion. It is used to potentiateimmune system .

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Pumps:

• Pumps :• Types of pumps:• 1) Implantable infusion pumps: Drug is implanted

subcutaneously, and delivered by I.V infusion.• Pumps are filled with drug through a septum with a needle.• Pumps deliver drugs to central vein for 7-14 days a constant

rate.• 2) Mechanical pumps: Easily manipulated to deliver protein

and peptide drugs.• Example: insulin has been successfully delivered by portable

syringe.

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NON-PARENTRAL ROUTES

• ORAL ROUTE OF ADMINISTRATION

Most popular route of drug delivery

• Advantages:

convenience

patient compliance

acceptability

• Disadvantages

• potential degradation by proteolytic enzymes, strong

acids

• Very low permeability across gastrointestinal

mucosa.

• First pass metabolism

Oral route:

• Encapsulated peptides or proteins inmicrosphere of approximately 10 micronin diameter , used for oral delivery.

• Example : Insulin and heparin.• Orally administered insulin produces

hypoglycemic effect .

• Disadvantages: Acid catalyzed degradationin stomach.

• Proteolysis in GIT.29

BUCCAL ROUTE OF ADMINISTRATION

• The drugs are absorbed through oral mucosamainly through the non-keratinized regions

• ADVANTAGES:• It can be attached or removed without any

discomfort and pain• Well acceptability by patients• Drugs are absorbed rapidly

• DISADVANTAGES:

• Administration time is limited

• Drug loss by accidental swallowing

• Drugs administered by this route are insulin,

vasopressin, oxytosine

NASAL ROUTE OF ADMINISTRATION

• The nasal route has been employed forproducing local action on the mucosa which ismore permeable compared to oral mucosa.

• Nasal absorption is through passive diffusionEX: Insulin, human growth hormone.

• ADVANTAGES:Rapid onset of actionFirst pass metabolism can be avoidedBetter drug absorption

• DISADVANTAGES:Long-term usage causes toxicity

Size of proteins and peptide drugs reduces systemic bioavailability.

TRANSDERMAL ROUTE OF ADMINISTRATION

• This is topical medication.• Drug is absorbed through the skin.

EX:Insulin, vasopressin

• ADVANTAGES:Controlled administration of drug is possible.Improved patient compliance.Drugs with short half lives can be administered.

• DISADVANTAGES:

• High intra and inter patient variability

• Low permeation because of high molecular weight

• Hydrophilicity and lipophilicity of stratum corneum

PULMONARY ROUTE OF ADMINISTRATION

• Lungs are attractive site for systemicdelivery of proteins and peptides because oftheir enormous surface area(70 sq.m)

• Alveoli and lungs are the absorption sites.

• Drugs are absorbed through lungs bysimple diffusion,carrier mediated transport.

• ADVANTAGES:• Decrease in dose requirement.• Fast absorption• Increased patient compliance

• DISADVANTAGES:• Inflammation may be observed in lungs.• Degree of bioavailability was less due to

hydrolytic enzymes present in lungs.

RECTAL ROUTE

• Rectum is highly vascularised body cavity

• Rectal mucosa is devoid of villi

• Drugs are in form of suppositories, gel, drypowders.

• EX:Insulin,calcitonin

• ADVANTAGES:

• Reduced proteolytic degradation• Improved systemic bioavailability with co-

administration of absorption enhancers.EX:surfactants

• Large dose can be administered

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Formulation aspects:

Storage:

Refrigeration

Packaging

Additives

Freeze-Drying

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Protein Formulations

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• Protein sequence modification (site directed mutagenisis)

• PEGylation

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• Proteinylation

• Microspher encapsulation

3• Formulating with permeabilizers

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PEGylation

PEG is a non-toxic, hydrophilic, FDA approved, uncharged polymer Increases in vivo half life Decreases immunogenicity Increases protease resistance Increases stability

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