1. Proteins and Peptides
drug delivery system
Presented by
G.Ramya
Mpharm(phceutics)
256212886041
MRCP
Under the guidance of
Mrs.Yasmin Begum
Mpharm(PhD)

2. Contents
 Protein & Peptides
 Structure of protein
 Classification of protein
 Stability problems
 Marketed formulations
 Conclusion
 References

3. Protein & Peptide
Proteins: These are large organic compounds made of amino
acids arranged in a linear chain and joined together by peptide
bonds.
Protein > 50 amino acids
Peptides: These are short polymers formed from the linking, in
a defined order, of α-amino acids.
peptide < 50 amino acids

4. STRUCTURE OF PROTEIN
 Each peptide or protein molecule is a polymer chain with α
aminoacids linked together in a sequential manner by peptide
bonds.
 The peptide chains in a protein molecule are often folded into
a specific three dimensional structure to fulfill a certain
biological function.
 The functional groups on each of the aminoacids and the
sequence of the aminoacids in the peptide chains determine
the conformation of the protein.

5. STRUCTURE OF PROTEIN
 Based on their conformation proteins are classified as
 Fibrous proteins
Eg: collagen, keratin, elastin.
 Globular proteins: insulin

6. STRUCTURE OF PROTEIN
There 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).

8. Lactate Dehydrogenase:
Mixed α /β
Immunoglobulin
Fold: β
Hemoglobin B Chain:
α
Protein Structure

9. FUNCTIONS
 Transport and storage of small molecules.
 Coordinated motion via muscle contraction.
 Mechanical support from fibrous protein.
 Generation and transmission of nerve impulses.
 Enzymatic catalysis.
 Immune protection through antibodies.
 Control of growth and differentiation via hormones.

10. Classification of Proteins
According to their biological roles
 Enzymes – Catalyses virtually all chemical reactions i.e.
6GDH
 Transport proteins i.e. Haemoglobin of erythrocytes
 Contractile or Motile proteins i.e. Actin and Myosin
 Structural proteins i.e.Collagen in bones
 Defense proteins i.e. Immunoglobulins and Antibodies
 Regulatory proteins i.e. insulin
 Nutrient and storage proteins i.e. Ovalbumin

11. Protein and Peptide drugs
 Management of illness through medication is entering a new
era in which a growing number of biotechnology produced
peptide and protein drugs are available for therapeutic use.
 Ailments that can be treated effectively by this new class of
therapeutic agents include cancers, memory impairment,
mental disorders, hypertension.

12. Disadvantages
 Short biological half-life
 Very large and unstable molecules.
 Structure is held together by weak noncovalent forces.
 Easily destroyed by relatively mild storage conditions and
gastric juices.
 Hard to obtain in large quantities.

13. Problem with Proteins
(in vivo – in the body)
 Elimination by B and T cells
 Proteolysis by endo/exo peptidases
 Small proteins filtered out by the kidneys very quickly
 Unwanted allergic reactions may develop (even toxicity)
 Loss due to insolubility/adsorption
 First-pass elimination in liver

15. Protein instabilities
Physical instability Chemical instability
Denaturation Deamidation
Adsorption Oxidation and reduction
Aggregation Proteolysis
Precipitation Disulfide exchange
Racemization
β-elimination

16. Denaturation
 Denaturation refers to any nonproteolytic modification of the
unique structure of a native protein that affects definite
changes in physical, chemical and biological properties.
 Denaturation leads to rearrangement and loss of quarternary
and tertiary structure and the hydrophobic and hydrogen
bonds are broken.
 Conditions include:
 Solvent changes
 pH change
 Alteration in ionic strength
 Temperature rise

17. Common Protein Denaturing agents
Category Mechanism Examples
Polar and protic
chemicals
Surfactants
Disrupt H-bonds
Hydrophobic
disruption and charge
group separation
Urea, Guanidine HCL,
Alcohol, Acetic acid
Sodium dodecyl sulphate,
Polyethylene glycol,
Dodecyl ammonium
chloride

18. Adsorption
 Proteins and peptides tend to absorb at interfaces such as air-water
and air-solid.
 This leads to conformational rearrangement which may cause
loss or change in the biological activity.
 It posses limitations with the drug delivery systems where
protein content of formulation may remain adhered to the
containers or drug delivery devices.
 Overcome by addition of surfactants such as Pluronic F68 and
Tween80.

19. Aggregation and Precipitation
 Mechanism of protein aggregation involves protein
denaturation and noncovalent association via hydrophobic
residues.
 Aggregation on a macroscopic scale leads to precipitation.
 Conditions favour include:
 Large air-water interface
 Agitation of the solution
 Presence of large headspace within the confines of
container.
 Increase in thermal motion of the molecules due to
agitation.

20. Deamidation
 It involves the hydrolysis of the side chain amide linkage of an
aminoacid residue leading to formation of free carboxylic
acid.
 Asparagine, glutamine, serine, glycine.
 Human growth harmone(hGH), bovine growth
harmone(bGH), prolactin, insulin, lysozyme and secretin.
 It leads to lowering of biological activity and alteration in
function.

21. Deamidation of L-Asparagyl residue

22. Oxidation
 Methionine, cysteine, tryptophan and tyrosine.
 Commonly occurs during isolation, synthesis and storage of
proteins.
 Leads to loss in biological activity as observed in calcitonin,
corticotrophin, gastrin.
 Oxidising agents like hydrogen peroxide, dimethylsulphoxide
and iodine oxidise met to Met-sulphoxide.
Methionyl residue Methionyl sulfone residue

23. Proteolysis
 Hydrolysis of peptide bonds within the polypeptide or protein
destroys or reduces the activity.
 It may occur on prolonged exposure of proteins to extreme pH
range, high temperature or proteolytic enzymes.
 Bacterial contamination is the most common source of
proteases.

24. Disulfide Exchange
 Disulfide bonds may break and reform with incorrect pairings
which results in alteration of 3-dimensional structure followed
by change in biological activity.
 HSR’ + R-S-S-R ---- > R-S-S-R’
 Peptide chain with more than one disulfide can enter into
disulfide exchange reactions leading to scrambling of disulfide
bridges and thereby change in alteration.

25. Racemization
 Alteration of L-aminoacids to D,L-mixtures.
 Except gly, all the mammalian aminoacids are chiral at the
carbon bearing chain and are susceptible to base catalysed
racemization.
 This reaction can be catalysed in neutral and alkaline media
by thiols which may arise due to hydrolytic clevage of
disulfides.

26. β-elimination
 The mechanism is similar to racemization which forms a
carbonium intermediate.
 Higher elimination rate under alkaline conditions leads to loss
of biological activity.
 Cys, Lys, Phe, Ser, and Thr

27. Photodegradation
 Tryptophan, Tyrosine and Cysteine are susceptible to
nonionizing radiation such as UV light.
 Photoionisation can be either through direct interaction with
aminoacid or indirectly via various sensitizing agents such as
oxygen.
 Photodegradation products include:
 S-S bond fission
 Conversion of tyrosine to DOPA
 Conversion of tryptophan to kynurenine and n- formyl-
Kynurenine.

28. Commonly used excipients For
solving physical and chemical stability problems
Excipients Functions Examples
Surfactants Prevent denaturation
and aggregation
Polysorbate 20, 80
Albumin Antiaggregatory Serum albumin
Sugars Stabilize protein against
denaturation
Mannitol, propylene
glycol, Sucrose,
Lactose
Cryoprotectants Stabilize protein against
very cold condition
Sugars, Amino acids,
Amines, polyols,
Salts

29. Osmolarity agent Stabilize pH Phosphate, Citrate
Buffer
Preservatives Prevent from
microbes
Phenol, benzyl
alcohol
Antioxidants Prevent oxidation Ascorbic acid,
sulphites, cysteine,
chelating agent
Solubility
enhancing agent
Increase solubility
of protein
Amino acids,
detergent,
cyclodextrin
Lyoprotectants Stabilize protein
during freeze drying
Sugars

30. Applications
Protein/peptide drugs Biomedical applications
CVS active
Angiotensin 2 antagonist
Bradykinin
Captopril
Lowering blood pressure
Improving peripheral
circulation
Heart failure management
CNS active
Cholecystokinin
Β-endorphin
Suppressing appetite
Relieving pain

31. Applications
GI-active
Gastrin antagonist
Pancreatic enzymes
Reducing secretion of gastric acid
Digestive supplement
Immunomodulating
Bursin
Cyclosporin
Interferon
Selective B-cell differentiatingharmone
Inhibits functions of T-lymphocyte
Enhancing activity of killer cells
Metabolism
modulating
Insulin
Vassopressin
Treating diabetes mellitus
Treating diabetes insipidus

32. MARKETED PROTEINS IN FREEZE DRIED
Product Formulation Route Indication
Metrodin FSH 75 IU i.m. Induction of
ovulation
Pergonal FSH and LH i.m. infertility
Profasi HCG i.m. Infertility
Elspar Asparginase i.m. i.v. Leukemia
Glucagon Glucagon i.m. i.v. s.c. Hypoglycemia
Acthar Corticotropin i.m. i.v. s.c. Hormone
Deficiency
FORMULATIONS

33. MARKETED PEPTIDES IN READY TO USE
FORMULATIONS
Product Formulation Route Indication
Pitressin 8-Arginine
Vasopressin
i.m. s.c. Post operative
abdominal
distension
Lupron Leuprolide s.c. Prostatic
cancer
Syntocinon Oxytocin i.m. i.v. Labour
induction
Sandostatin Octreotide s.c. Intestinal
tumour
Calcimar Salmon
s.c. hypercalcemia

34. SUSTAINED RELEASE DOSAGE FORMS
Product Formulation Route Indication
Lupron Leuprolide i.m. Prostatic
cancer
H.P.Acthar
gel
ACTH i.m. s.c. Antidiuretic
Pitrressin
tannate in oil
Vasopressin
tannate
i.m. Endocrine
cancer

35. Conclusion
 Protein and peptide based pharmaceuticals are rapidly
becoming a very important class of therapeutic agents and are
likely to replace many existing organic based pharmaceuticals
in the very near future.
 Peptide and protein drugs will be produced on a large scale by
biotechnology processes and will become commercially
available for therapeutic use.

36. Conclusion
 This poses an urgent challenge to the pharmaceutical industry
to develop viable delivery systems for the efficient delivery of
these complex therapeutic in biologically active form.
 Much work needs to be done on the development of viable
delivery systems for non parenteral administration to make
peptide and protein pharmaceuticals commercially viable and
therapeutically useful.

37. REFERENCES
 Controlled drug Delivery Concepts and Advances By Vyas,
Roop Khar, Proteins and Peptides Delivery Considerations
Page No: 503-511.
 Advances in Controlled and Novel Drug Delivery By
N.k.Jain, Oral delivery of protein and peptides Page no: 232-
235.
 Novel Drug Delivery System By Yie.W.Chein, Systemic
Delivery of Peptide based pharmaceuticals Page no:631-637.
 Drug Stability Principles and practices By J.Carstensen,
Stability of Polypeptides and Proteins Page no:560-572