Radiolabelled peptides and hormones

Presented by:

Sumra Idrees (574)

Presented to:

Sir Tanveer bukhari

GCUF

Peptides have an important role in fundamental body

functions as cell signaling and homeostasis

Recently these are focused of much interest as are being

used in diagnostic radiopharmaceuticals

Peptides show a logical radiopharmaceutical

development

Introduction

Introduction conti……

• For tumor imaging these receptors are considered prospective molecular targets

• as well as targeted radiotherapy by the help of radiolabeled peptides

• In neuroendocrine tumors (NETs), somatostatin (SST) is the finest exemplar receptor overexpression which are presently being embattled effectively by SST analogs, n-DTPA-octreotide

Introduction conti…….

• The high level expression of SST receptors on a variety of cancers has given the molecular root for the achievement of In-OctreoScan

• like a tumor targeting peptide and it opens fresh avenues for the growth of other tumor-specific peptides through potential utilize in nuclear oncology

Tremendously high affinities (nano- or subnanomolar

range)

for cell-surface receptors are shown by naturally

happening peptides

Introduction conti……

Types of peptides

1. Gastrin-releasing peptides and bombesin

2. Vasoactive intestinal peptide

3. Glucagon-like peptide

4.Natural Biologically active Peptides

Gastrin-releasing peptides and bombesin

• Gastrin-releasing peptide (GRP) and bombesin can fasten to G-coupled GRP receptors which are ubiquitous on cells of numerous frail somebody types

• such as endocrine, tit and pancreatic house and small-cell lung carcinoma

• Bombesin is a dwarfish neuropeptide of 14 radical acids which has been unaccompanied from frogs,

• whereas GRP, the earthborn writing of this bombesin, consists of 27 alkane acids

Both peptides pretense have same natural behavior in humans, which can be explained by only infinitesimal structural differences between the two molecules

The protection computer of bombesin consists of figure amino resolvent residues

And in the literature peptides which incorporate this octapeptide are ordinarily termed bombesin

Gastrin-releasing peptides and bombesin

Vasoactive intestinal peptide

• Vasoactive enteral peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP), which are both Secretin like peptides,

• Are neuropeptides which determine a catholic spectrum of life activities

• including vasodilatation,

• stimulation of secretion of different hormones,

• immunomodulation and advancement of cadre proliferation

Vasoactive intestinal peptide

• VPAC1 is verbalized in the mentality and most epithelial tissues

• VPAC2 is only inform in suave tough

• The VPAC1 receptor is the only VIP/PACAP receptor saved on neoplasm cells of neuroendocrine origin and neuroblastomas

• But in medullary endocrine cancers, VIP/PACAP receptors are gone

Vasoactive intestinal peptide

• Latterly a many lasting 64Cu-labelled VIP analog has been formed for neuroendocrine

• And manlike face tumours, that shows a higher tumour uptake than the 99mTc-labelled VIP linear

Glucagon-like peptide 1 (GLP-1) receptors belong to the G coupled accelerator organ set

Physical organ reflection in humans is controlled to the endocrine organ, duodenum and pancreas

The operate of these GLP-1 receptors is not yet completely comprehended

But receptor information seems to lead in humour of insulin

calcitonin and augmented proliferation of tumour cells with inhibited apoptosis

Glucagon-like peptide

Recent studies tally shown the clinical

voltage of the GLP-1 receptor

Antimicrobial peptides

which are mainly produced by

phagocytes and endothelial cells

Are heavy factor of the innate immune

group, providing security against microorganism

attacks

Glucagon-like peptide

Glucagon-like peptide

• Manlike neutrophile peptide 1-3 (HNP 1-3) is a defending that induces the creation of lymphokines

• And promotes T-cell and antigen-specific body production

• This peptide is apace improved from the circulation via the kidneys and vesica with low reflex

• But growth in the gallbladder and the intestine makes it unfavorable ammunition for the espial of abdominal infectionsion in the liver

Natural Biologically active Peptides

• Peptides are obligatory elements in solon basic life processes than any added category of corpuscle

• For ideal, peptides role as hormones, neurotransmitters, neurornodulators, ontogenesis and ontogeny forbiddance factors and cytokines

Natural Biologically active Peptides

• The molecular weights of biologically active peptides are extremely different

• Ranging from 3 to 5 residues in TRH, enkephalins and bacterial chemoattractant peptides to over 200 residues in ontogenesis hormone

• For instance in PTH and ACTH, biological reflection is given by the N-terminal sequence

Two major categories of methods for synthesizing peptides:

1.solution-phase in addition to solid-phase peptid

2.Merrifield’s SPPS Method

Peptide synthesis

solution-phase in addition to solid-phase peptid

• The ‘‘traditional’’ solution-phase synthesis procedure has some degree of applications in modern fast emergent peptide fielde synthesis

• This method frequently requires complex and lengthy purification process that’s why it is difficult, expertise exhaustive

• as compared to this method, Merrifield’s SPPS is at this time the favored process for peptide synthesis

It requires fewer purifications and minimal optimization of the reaction condition that’s why SPPS is a speedy and trouble-free approach

The significant development in the field of peptide formation

over the preceding numerous years has brought innovation of a large diversity of bioactive peptides

Merrifield’s SPPS Method

FIG: scheme of peptide labeling

How radiolabeleled peptides are used for diagonastic propose

• The scrutiny specialism of atomic medication focuses on the application of radiolabelled tracers for scintigraphic imaging

• or radionuclide therapy of disease

• The modern phylogeny of knowledge in molecular accumulation has resulted in new targets to find weak somebody specifically

How radiolabeleled peptides are used for diagonastic propose

• New developments in (broadcasting) immunology someone landscaped molecular transfer of radionuclides to disease-target sites

• Consequently this has resulted in the breeding of novel tracers

• Specialised developments in scintigraphic instruments and recollection software feature restored picturing modalities

• allowing small-animal scintigraphic

How radiolabeleled peptides are used for diagonastic propose

• A auspicious possibleness for atomic applications in oncology lies in the utilization of radiolabelled peptides that point receptors for picturing and therapy

• Linked to apropos therapeutic radionuclides these peptides can also be utilized as radiotherapeutics in peptide organ radionuclide therapy (PRRT)

Fig: peptides as diagnostic tools

Radio labeling of peptides

• Attaching an immense chelating moiety or a prosthetic group to small size peptides

• and adding a radiolabel can manipulate the fastening affinity and pharmacokinetic properties of a peptide

• That’s why, for flourishing radio labeling with the preferred radionuclide a watchful variety of a chelating group and site-specific radio labeling is essential

An extensive range of prosthetic groups and chelating agents have been made in current years

for the suitable radio labeling of peptides with a variety of radionuclides

Several radionuclides, either therapeutic (177Lu, 90Y)

or diagnostic (18F, 64Cu, 111In, 123I, 68Ga, 99mTc), have been used for radio labeling

Radio labeling of peptides

Peptides are made up of the similar basic structural blocks as proteins, therefore techniques which have been developed for

radio labeling

as peptides have smaller number of amino acid residues as compared to proteins therefore there are fewer sites vacant for

labeling

RADIOLABELING TECHNIQUES

RADIOLABELING TECHNIQUES

• Definite activity becomes a serious element in the synthesis of radiolabeled peptides

• due to the elevated influence of numerous peptides and the small tissue concentrations of their target receptors

• Varieties of methods for labeling proteins with radioisotopes of carbon, fluorine, iodine, technetium, gallium and iridium have been developed for the time of more than ten years

It is the most broadly utilized technique for radio labeling of peptides

For in-vitro applications of radioabeled peptides initially it was developed,

such as in RIA assays, radio iodination have great applications for imaging purposes

For all this to happen there is the need of isotopes like Iodine-123 and Iodine-124, as well as Iodine-131

Iodination

Iodination

• For direct iodination Reagents are available including the commonly used agents, like iodine monochloride N-bromosuccinimide, Iodogenand and Chlorarnine T

• we can achieve Quantitative labeling with most peptides by changing the conditions of reaction

• and the elimination of unnecessary radioactive by-products

Iodination• chromatographic techniques like ion

exchange and reverse-phase are used for purification of the radiolabeled peptide

• One probable disadvantage of radio labeling using iodine for peptides is the examining in vivo of speedy dehalogenation

N-succinimidyl- 4 Iodobenzoate N-succinimidyl -3-Iodobenzoate

N-succinimidyl -5 -Iodo-3-pyridine carboxylates

In common, these reagents express larger in vivo strength as

compared to directly labeled polypeptides and also trialkyl

stannyl precursors are building blocks of these reagents

Radio labeling reagents

Radio labelling techniques

• For lowering in vivo dehalogenation the structural necessities has been seen it includes (a) the linkage nature of polypeptide (b) length of alkyl chain and (c) the substituent’s of ring

• for scintigraphic imaging of peptides Iodine-131

• High radiation, high cost, the limited availability and the reduced imaging behavior of Iodine-123 are now linked with Iodine 131 Iodine-123 have been used

Technetium-99m

• Because of its low cost

• comprehensive ease of use,

• outstanding imaging characters, and encouraging dosimetry technetium-99 is a perfect radionuclide for peptide labeling

• More ever, Tc-99m can too be obtained at sky-scraping definite action

• Tc-99m labeling chemistry is enhanced definite and additional expected by using the bifunctional chelate or indirect method

Group III metal Iridium-l11 has a chemistry and half-life which

makes it perfect for radio labeling integral immunoglobulin

The PE isotope, Gallium-68 was used for radio labeling chemo

tactic peptides

and a somatostatin analog using DTPA and desferrioxamine as

bifunctional chelates, correspondingly

Indium-111 and Gallium-68

Development of a peptide-based Radiopharmaceutical

• To build up a new radiopeptide, a natural or synthetic peptide should be radiolabeled competently with high precise radioactivity

• and be constant under physiological situation

• The new peptide should be able to exhibit an elevated tumor uptake and maintenance in vivo with low environment radioactivity

Continue……….

• A pure negatron emitter

• Medium- or high-energy particle

• Moderately long effective half-life

• High target-nontarget ratio

• Readily available and inexpensive

• Minimal radiation dose to personnel

• - Provides high linear energy transfer -Decreases radiation dose to adjacent normal tissues

• - Energies greater than 1 maximum beta-energy (meV)

• - Typically in days - Easy to control dosimetry

• - Decreases exposure of normal tissues - Provides selective delivery of radiation

• - Increases use at many institutions

• - Easy to control with negatron emitters

Tumor imaging peptide radiopharmaceuticals

To make radiolabeled peptide clinically functional for tumor imaging it should have following properties:

(i) high precise uptake and preservation in tumors

(ii) tall in vivo stability

(iii) effortlessness of preparation

(iv) elevated affinity for the target receptor

The victorious utilization of radiolabelled peptides like radio

diagnostics has been translated into the expansion of peptide receptor

radionuclide therapy

The dictatorial peptide has also been radiolabelled for finding targets in

vivo as their receptors are repeatedly over articulated in a diversity of nasty

tumours

Applications of polypeptides as imaging probes

The most excellent outcome so far have been achieved in comparatively

radiosensitive lymphomas

Clinical trials correspondingly can be made effective, which can decrease the number

of effected people treated with unsuitable doses

Applications of polypeptides as imaging probes

Positron emission tomography as the imaging technique

• Positron emission tomography is an in vivo tomographic imaging method

• Its base is actually the finding of anti-parallel 511 keV photons emitted throughout the total destruction of positrons with electrons

• The positrons approach from the decompose of positron-emitting nuclides

Fig PET

Advantages and limitations of peptide-based Radiopharmaceuticals

• Advantages

• Minute peptides are important tools for peptide receptor radiotherapy and tumor diagnosis

• Easy to synthesize and manipulated molecularly to make their affinity sure for a meticulous receptor and to exhibit a more specific biodistributionoutline

Advantages

• capability to go through into tumors sooner than monoclonal antibodies.

• capability to bear the cruel conditions like pH, temperature, etc. of chemical alteration or radio labeling

Disadvantages

• The enzymatic annihilation can be repressed by molecular changes:

• the replacement of D-amino acids for logically occurring L-amino acids the amalgamation of amino alcohols, the insertion of unnatural amino acid or side chains or amidation

• Peptides may be capable to persuade pharmacologic special effects even in low amounts

Disadvantages

• failure of binding likeness upon combination with a chelator .

• Problem can be decreased by site-directed radio labeling that can be achieved by inserting a spacer group between the binding series and the chelating moiety

• No doubt radiolabelled peptides have their on importance but there are drawbacks too as nothing are unique in this universe.

Conclusion

• Radiolabelled peptides know tremendous possibleness for clinical good

• In oncology many (new) peptides are existence mature and evaluated for both characteristic and therapeutic use

• An intriguing usage is the usage of sharp peptides, which strength is real reusable in precise growth targeting