The Protein
Presented By
Dr. Shazzad Hosain
Asst. Prof. EECS, NSU
Proteins
 Proteins do the nitty-gritty jobs of every living cell.
• Proteins are made of
long strings of
individual building
blocks known as
amino acids.
Connection between DNA and Protein
Exon
Intron
DNA Transcription and Translation
mRN
A
tRN
A
mRNA
 mRNA is read in triplets, called codon
 Four different nucleotides, thus 43 = 64 possible codon
 However, there are only 20 different amino acids
 Thus genetic code is degenerate i.e. multiple codon produce same protein
The Genetic Code of RNA
The codon AUG for Methionine acts as start codon
Protein Functions
Proteins
• Make up about 15% of the cell
• Have many functions in the cell
–
–
–
–
–
–
–
–
–
Enzymes
Structural
Transport
Motor
Storage
Signaling
Receptors
Gene regulation
Special functions
Folded proteins are placed into two
general categories
Fibrous proteins
globular proteins
Fibrous proteins have polypeptide chains
organized in long fibers or sheets
 Water insoluble
 Very tough physically, may
be stretchy
Functions of fibrous proteins
 Structural proteins function
in support
 Insects and spiders use silk
fibers to make cocoons and
webs
 Collagen and elastin are
used in animal tendons and
ligaments
 Keratin is the protein in
hairs, horns and feathers
Functions of fibrous proteins
 Contractile proteins
function in movement
 Actin and myosin
contract to create the
cleavage furrow and
to move muscles
 Contractile proteins
move cilia and flagella
Globular proteins have their chains folded
into compact, rounded shapes
 Easily water soluble
Functions of globular proteins
 Storage proteins function in the
storage of amino acids
 Ovalbumin is the protein in egg
whites
 Casein is the protein in milk,
source of amino acids for baby
mammals
Functions of globular proteins
 Transport proteins function in the movement of other
substances
 Hemoglobin, the iron containing protein in blood,
transport oxygen from lungs to other parts of the body
(C3032H4816O872N780S9Fe4)
 Membrane transport proteins such as channels for
potassium and water
Functions of globular proteins
 Hormone proteins function as cellular messenger
molecules that help maintain homeostasis
 Insulin: sends message “allow sugar into cells” (when blood
glucose levels are high, cells will transport glucose into the
cells for use or storage)
 Glucagon: sends message “we need more sugar in the
blood” (when blood glucose is too low, cells will release
glucose)
Functions of globular proteins
 Receptor proteins allow cells to respond to
chemical stimuli
 Growth factor receptors initiate the signal
transduction pathway when a growth hormone
attaches
Functions of globular proteins
 Protective proteins function as protection
against disease
 Antibodies combat bacteria and viruses
Functions of globular proteins
 Enzymes speed up chemical reactions
 Amylase and other digestive enzymes hydrolyze
polymers in food
 Catalase converts hydrogen peroxide H2O2 into
water and oxygen gas during cellular respiration
Protein Structures
Peptide Bonds join amino acids
It’s a condensation reaction
(meaning that H20 (or some other small
molecule) is released when the
bond is formed).
Two amino acids form a
DI-PEPTIDE
POLYPEPTIDES
are formed from more
than two amino acids
bonded together
Polar R groups make the amino acid hydrophilic
Non-polar R groups make the amino acid hydrophobic
Ionic R groups make the amino acid hydrophilic
Polar vs Nonpolar Amino Acids
Hydrophilic
Hydrophobic
There are 20 commonly occurring amino
acids that are found in proteins










alanine - ala - A
arginine - arg - R ***
asparagine - asn - N
aspartic acid - asp - D
cysteine - cys - C
glutamine - gln - Q
glutamic acid - glu - E
glycine - gly - G
histidine - his - H ***
isoleucine - ile - I
•
•
•
•
•
•
•
•
•
•
leucine - leu - L
lysine - lys - K
methionine - met - M
phenylalanine - phe - F
proline - pro - P
serine - ser - S
threonine - thr - T
tryptophan - trp - W
tyrosine - tyr - Y
valine - val - V
“Essential Amino Acids”
are those that must be ingested in the diet
(our body can’t make them)
*** essential in certain cases
Proteins have four levels
of organization
Primary structure
is the
amino acid
sequence
The amino acid
sequence is
coded for by
DNA and is
unique for
each kind of
protein
The amino acid
sequence
determines how
the polypeptide
will fold into its
3D shape
Even a slight change in the amino
acid sequence can cause the
protein to malfunction
For example,
mis-formed hemoglobin causes sickle cell disease
Proteins have four levels
of organization
Secondary structure results from hydrogen
bonding between the oxygen of one amino acid
and the hydrogen of another
Red = oxygen
Black = Carbon
Blue = Nitrogen
Green = R
The alpha helix is a coiled secondary
structure due to a hydrogen bond every
fourth amino acid
The beta pleated sheet is formed by
hydrogen bonds between parallel parts of
the protein
A single polypeptide may have portions
with both types of secondary structure
Proteins have four levels
of organization
Tertiary structure depends on the interactions
among the R group side chains
Types of interactions
 Hydrophobic interactions: amino acids with
nonpolar side chains cluster in the core of the
protein, out of contact with water
= charged
= hydrophobic
Types of interactions
 Hydrogen bonds between polar side chains
Types of interactions
 Ionic bonds between positively and negatively
charged side chains
Types of interactions
 Disulfide bridge (strong covalent bonds) between
sulfur atoms in the amino acid cysteine
Link to video
Keratin is a family of fibrous structural proteins
Proteins have four levels
of organization
Quaternary structure results from
interactions among separate polypeptide
chains into a larger functional cluster
For example, hemoglobin is composed of
4 polypeptide chains
Proteins have four levels
of organization
The folding of proteins is aided by other
proteins, called chaperones
 Act as temporary braces as proteins fold into their
final conformation
 Research into chaperones is a
area of research in biology
Denaturation results in disruption of the
secondary, tertiary, or quaternary structure
of the protein
Denaturation may be due to changes in
pH, temperature or various chemicals
Protein function is lost during denaturation,
which is often irreversible
Protein Folding
What is Protein Folding ?
• Protein folding is the process by which a protein
assumes its functional shape or conformation.
Random Coil
Native conformation
Why is the “Protein Folding” so important
 Most of the proteins should fold in order to function
 Misfolding cause some diseases.
 Cystic Fibrosis, affects lungs and digestive system
and cause early death
 Alzheimers’s and Parkinson's disease
 It may help us to understand the structure of proteins
which has not been known
LEVINTHAL PARADOX
 Let have Protein composed of 100 amino acids.
 Assume that each amino acid has only 3 possible
conformations.
 Total number of conformations = 3100 ~= 5x1047 .
 If 100 psec (100x10-12 sec) were required to convert from
a conformation to another one, a random search of all
conformations would require
5x1047 x 10-10 sec = 1.6 x 1030 years.
However, folding of proteins takes place in msec to sec
order.
Forces that stabilize protein structure
 Interactions between atoms within the protein chain
 Interactions between the protein and the solvent
 Electrostatic Interactions
 Interaction of charged side chain with the opposite
charged side chain.
 Hydrogen Bonds & van derWaals forces
 Hydrophobic interactions
The kinetic Theory of Protein Folding
Folding proceeds through a definite series of steps or a
Pathway.
A protein does not try out all possible rotations of
conformational angles, but only enough to find the pathway.
Energy Landscape
Protein folding models
 The Framework Model
 Hydrophobic collapse
 Nucleation Model
The Framework Model
 Local interactions are main determinants of protein structures
unfolded state
Transition state
native state
Hydrophobic Collapse
 Hydrophobic core forms first.
collapse
unfolded state
native state
Hydrophobic Collapse
 Formation of hydrophobic globule may hinder the
reorganization of both side chains and whole protein
Nucleation Model
 Unites hydrophobic collapse and frame work model
unfolded state
formation of
a nucleus
native state
Nucleation Model
 Substantial expulsion of water from the burial of non polar
surfaces
 Good correlation between decrease in hydrodynamic volume
and increase in secondary structure
Disease caused by Protein Mis-folding
Diseases caused by the defect in protein folding:
Cystic fibrosis: Defect in the folding of cystic fibrosis Tran membrane
conductance regulator protein.
Diseases caused by misfolding of Prion proteins:
Kuru Disease
Creutzfedlt-Jakob Disease
Scrapie Disease in sheep
Mad cow disease
Misfolded prion protein act as infectious agents.
They act as chaperons which can multiply by binding to normal PrP and
folding it to dangerous form similar to itself.
Mechanisms of the functions of normal prions and the dangerous ones
are still not clear.
Stained section from the cerebral cortex from a patient with Creutzfedlt-Jakob
disease indicating spongiform patahlogy
Non-local contacts = High contact order
contacts between residues in the primary sequence:
NEARBY
A
B
B
A
FAR APART
B
A
A
B
ordering many more residues at once
= selecting from more conformational states
-> How is aggregation avoidance encoded?
How do high CO structures form co-translationally?
in vitro:
in vivo:
ribosome
B
A
A
A
B
• What conformations does A adopt
before B appears?
• How much native structure can be
formed co-translationally?
ordering many more residues at once
= selecting from more conformational states
-> How is aggregation avoidance encoded?
Drug Discovery
How are drugs discovered and developed?
 Choose a disease
 Choose a drug target
 Identify a “bioassay”
bioassay = A test used to determine biological activity.
 Find a “lead compound”
“lead compound” = structure that has some activity against the
chosen target, but not yet good enough to be the drug itself.
 If not known, determine the structure of the “lead compound”




Synthesize analogs of the lead
Identify Structure-Activity-Relationships (SAR’s)
Synthesize analogs of the lead
Identify Structure-Activity-Relationships (SAR’s)
 Identify the “pharmacophore”
pharmacophore = the structural features directly responsible
for activity
 Optimize structure to improve interactions with target
 Determine toxicity and efficacy in animal models.
 Determine pharmacodynamics and pharmacokinetics of the drug.
 Pharmacodynamics explores what a drug does to the body, whereas
pharmacokinetics explores what the body does to the drug.
 Patent the drug
 Continue to study drug metabolism
 Continue to test for toxicity
 Design a manufacturing process
 Carry out clinical trials
 Market the drug
Choosing a
Disease
 Pharmaceutical companies are commercial enterprises
 Pharmaceutical companies will, therefore, tend to avoid
products with a small market (i.e. a disease which only
affects a small subset of the population)
Choosing a
Disease
 Pharmaceutical companies will also
avoid products that would be
consumed by individuals of lower
economic status (i.e. a disease which
only affects third world countries)
Choosing a Disease (cont.)
 Most research is carried out
on diseases which afflict “first
world” countries: (e.g.
cancer, cardiovascular
diseases, depression,
diabetes, flu, migraine,
obesity).
The Orphan Drug Act
 The Orphan Drug Act of 1983 was passed to encourage
pharmaceutical companies to develop drugs to treat diseases
which affect fewer than 200,000 people in the US
 Under this law, companies who develop such a drug are entitled to
market it without competition for seven years.
 This is considered a significant benefit, since the standards for
patent protection are much more stringent.
Identifying a Drug Target
 Drug Target = specific macromolecule, or biological system,
which the drug will interact with
 Sometimes this can happen through incidental observation…
Identifying a Drug Target (cont.)
 Example: In addition to their being able to inhibit the uptake of
noradrenaline, the older tricyclic antidepressants were observed to
“incidentally” inhibit serotonin uptake. Thus, it was decided to prepare
molecules which could specifically inhibit serotonin uptake. It wasn’t clear
that this would work, but it eventually resulted in the production of fluoxetine
(Prozac).
HO
NH2
N
N
CH3
H3C
Imipramine
(a classical tricyclic antidepressant)
N
H
serotonin
F3C
HN
O
prozac
The mapping of the human genome
should help!
 In the past, many medicines (and lead compounds) were
isolated from plant sources.
 Since plants did not evolve with human beings in mind, the
fact that they posses chemicals which results in effects on
humans is incidental.
 Having the genetic code for the production of an
enzyme or a receptor may enable us to overexpress that protein and determine its structure and
biological function. If it is deemed important to
the disease process, inhibitors (of enzymes), or
antagonists or agonists of the receptors can be
prepared through a process called rational drug
design.
Simultaneously, Chemistry is Improving!
 This is necessary, since, ultimately,
plants and natural sources are not
likely to provide the cures to all
diseases.
 In a process called “combinatorial
chemistry” large numbers of
compounds can be prepared at one
time.
 The efficiency of synthetic chemical
transformations is improving.
Selectivity is Important!
 e.g. targeting a bacterial enzyme, which is not present in
mammals, or which has significant structural differences
from the corresponding enzyme in mammals
The Standards are Being Raised
 More is known about the biological chemistry of living systems
 For example: Targeting one subtype of receptor may enable the
pharmaceutical chemist to avoid potentially troublesome side
effects.
Problems can arise
 Example: The chosen target, may over time, lose its
sensitivity to the drug
 Example: The penicillin-binding-protein (PBP) known to the
the primary target of penicillin in the bacterial species
Staphylococcus aureus has evolved a mutant form that no longer
recognizes penicillin.
Choosing the Bioassay
 Definitions:
 In vitro: In an artificial environment, as in a test tube or culture media
 In vivo: In the living body, referring to tests conductedin living animals
 Ex vivo: Usually refers to doing the test on a tissue taken from a living
organism.
Choosing the Bioassay (cont.)
In vitro testing
 Has advantages in terms of speed and requires relatively small
amounts of compound
 Speed may be increased to the point where it is possible to
analyze several hundred compounds in a single day (high
throughput screening)
 Results may not translate to living animals
Choosing the Bioassay (cont.)
In vivo tests
 More expensive
 May cause suffering to animals
 Results may be clouded by interference with other biological
systems
Finding the Lead
Screening Natural Products
 Plants, microbes, the marine world, and animals, all provide
a rich source of structurally complex natural products.
 It is necessary to have a quick assay for the desired biological
activity and to be able to separate the bioactive compound
from the other inactive substances
 Lastly, a structural determination will need to be made
Finding the Lead (cont.)
Screening synthetic banks
 Pharmaceutical companies have prepared thousands of
compounds
 These are stored (in the freezer!), cataloged and screened on
new targets as these new targets are identified
Finding the Lead (cont.)
Using Someone Else’s Lead
 Design structure which is similar to existing lead, but different
enough to avoid patent restrictions.
 Sometimes this can lead to dramatic improvements in biological
activity and pharmacokinetic profile. (e.g. modern penicillins are
much better drugs than original discovery).
Finding the Lead (cont.)
Enhance a side effect
O
H2N
S
NH2
O
sulphanilamide
(an antibacterial with the side effect of
lowering glucose levels in the blood and also
diuretic activity)
N
Cl
O
O
S
NH
O
NH
tolbutamide
(a compound which has been optimized to only
lower blood glucose levels. Useful in the treatment
of Type II diabetes.)
O
H2N
NH
S
S
O
O
O
Chlorothiazide
(a compound which has been optimized to only display diuretic
activity.)
Use structural similarity to a natural ligand
NH2
N(CH3)2
H
N
HO
H3C
S
O
N
H
5-Hydroxytryptamine (5-HT)
Serotonin (a natural neurotransmitter
synthesized in certain neurons in the CNS)
O
N
H
Sumatriptan (Imitrex)
Used to treat migrain headaches
known to be a 5-HT1 agonist
Computer-Assisted Drug Design
 If one knows the precise molecular structure of the target
(enzyme or receptor), then one can use a computer to design a
perfectly-fitting ligand.
 Drawbacks: Most commercially available programs do not allow
conformational movement in the target (as the ligand is being
designed and/or docked into the active site). Thus, most
programs are somewhat inaccurate representations of reality.
Serendipity: a chance occurrence
 Must be accompanied by an experimentalist who understands
the “big picture” (and is not solely focused on his/her immediate
research goal), who has an open mind toward unexpected
results, and who has the ability to use deductive logic in the
explanation of such results.
 Example: Penicillin discovery
 Example: development of Viagra to treat erectile dysfunction
Finding a Lead (cont.)
Sildenafil (compound UK-92,480) was synthesized by a group of
pharmaceutical chemists working at Pfizer's Sandwich, Kent research
facility in England.
It was initially studied for use in hypertension (high blood pressure) and
angina pectoris (a form of ischaemic cardiovascular disease).
Phase I clinical trials under the direction of Ian Osterloh suggested that
the drug had little effect on angina, but that it could induce marked
penile erections.
Pfizer therefore decided to market it for erectile dysfunction, rather than for
angina.
The drug was patented in 1996, approved for use in erectile dysfunction by the
Food and Drug Administration on March 27, 1998, becoming the first pill
approved to treat erectile dysfunction in the United States, and offered for sale
in the United States later that year.
It soon became a great success: annual sales of Viagra in the period 1999–2001
exceeded $1 billion.
Finding a Lead (cont.)
O
N
N
N
NH
O
O
S
O
N
N
viagra
(Sildenafil)
Structure-Activity-Relationships (SAR’s)
 Once a lead has been discovered, it is important to understand
precisely which structural features are responsible for its
biological activity (i.e. to identify the “pharmacophore”)
The pharmacophore is the precise section of the molecule
that is responsible for biological activity
 This may enable one to prepare a more active molecule
 This may allow the elimination of “excessive” functionality, thus reducing the
toxicity and cost of production of the active material
 This can be done through synthetic modifications
 Example: R-OH can be converted to R-OCH3 to see if O-H is involved in an
important interaction
 Example: R-NH2 can be converted to R-NH-COR’ to see if interaction with
positive charge on protonated amine is an important interaction
Link
Next step: Improve Pharmacokinetic
Properties
 Improve pharmacokinetic properties.
pharmacokinetic = The study of absorption, distribution,
metabolism and excretion of a drug (ADME).
 Video
 exercise=MedicationDistribution&title=Medication%20
Absorption,%20Distribution,%20Metabolism%20and%
20Excretion%20Animation&publication_ID=2450
Metabolism of Drugs
 The body regards drugs as foreign
substances, not produced naturally.
 Sometimes such substances are referred
to as “xenobiotics”
•Body has “goal” of removing such xenobiotics from system by excretion in the urine
•The kidney is set up to allow polar substances to escape in the urine, so the body tries to
chemically transform the drugs into more polar structures.
Metabolism of Drugs (cont.)
 Phase 1 Metabolism involves the conversion of nonpolar
bonds (eg C-H bonds) to more polar bonds (eg C-OH
bonds).
 A key enzyme is the cytochrome P450 system, which
catalyzes this reaction:
RH + O2 + 2H+ + 2e– → ROH + H2O
Mechanism of Cytochrome P450
Phase I metabolism may either detoxify
or toxify.
 Phase I reactions produce a more polar molecule that is
easier to eliminate.
 Phase I reactions can sometimes result in a substance more
toxic than the originally ingested substance.
 An example is the Phase I metabolism of acetonitrile
The Liver
 Oral administration frequently brings the drugs (via the
portal system) to the liver
Metabolism of Drugs (cont.)
 Phase II metabolism links the drug to still more polar molecules to
render them even more easy to excrete
UDP Glucuronic Acid
Glucuronic Acid
HO
O
HO
O
O
P
O
P
O
O
O
NH
O
glucuronosyltransferase
enzyme
N
HO
OH
OH
O
Drug
O
HO
R
O
HO
HO
O
O
HO
OH
OH
OH
More easily excreted than ROH itself
R
OH
Drug
Metabolism of Drugs (cont.)
 Another Phase II reaction is sulfation (shown below)
NH2
N
O
O
R
OH
S
O-
N
O
O
P
O
N
O
O-
SO3-
N
R
Drug
O
O
P
OH
O-
O-
3'-Phosphoadenosine-5'-phosphosulfate
O
Sulfated Drug
(more easily excreted)
Phase II Metabolism
 Phase II reactions most commonly detoxify
 Phase II reactions usually occur at polar sites, like COOH,
OH, etc.
Manufacture of Drugs
 Pharmaceutical companies must make a profit to continue to exist
 Therefore, drugs must be sold at a profit
 One must have readily available, inexpensive starting materials
 One must have an efficient synthetic route to the compound
 As few steps as possible
 Inexpensive reagents
 The route must be suitable to the “scale up”
needed for the production of at least tens of
kilograms of final product
 This may limit the structural complexity and/or
ultimate size (i.e. mw) of the final product
 In some cases, it may be useful to design
microbial processes which produce highly
functional, advanced intermediates. This type of
process usually is more efficient than trying to
prepare the same intermediate using synthetic
methodology.
Toxicity
 Toxicity standards are continually becoming tougher
 Must use in vivo (i.e. animal) testing to screen for toxicity
 Each animal is slightly different, with different metabolic systems, etc.
 Thus a drug may be toxic to one species and not to another
Example: Thalidomide
Thalidomide was developed by German pharmaceutical company
Grünenthal. It was sold from 1957 to 1961 in almost 50 countries under at
least 40 names. Thalidomide was chiefly sold and prescribed during the late
1950s and early 1960s to pregnant women, as an antiemetic to combat
morning sickness and as an aid to help them sleep. Before its release,
inadequate tests were performed to assess the drug's safety, with catastrophic
results for the children of women who had taken thalidomide during their
pregnancies.
Antiemetic = a medication that helps prevent and control
nausea and vomiting
Birth defects
caused by use of thalidomide
Example: Thalidomide
From 1956 to 1962, approximately 10,000 children were born with severe
malformities, including phocomelia, because their mothers had taken thalidomide during
pregnancy. In 1962, in reaction to the tragedy, the United States Congress enacted laws
requiring tests for safety during pregnancy before a drug can receive approval for sale in
the U.S.
O
N
O
NH
O
O
Thalidomide
Phocomelia presents at birth very short or absent long bones and flipper-like
appearance of hands and sometimes feet.
Example: Thalidomide
Researchers, however, continued to work with the drug. Soon after its
banishment, an Israeli doctor discovered anti-inflammatory effects of
thalidomide and began to look for uses of the medication despite its
teratogenic effects.
He found that patients with erythema nodosum leprosum, a painful skin
condition associated with leprosy, experienced relief of their pain by taking
thalidomide.
Teratogenic = Causing malformations in a fetus
Thalidomide
Further work conducted in 1991 by Dr. Gilla Kaplan at Rockefeller University in
New York City showed that thalidomide worked in leprosy by inhibiting tumor
necrosis factor alpha. Kaplan partnered with Celgene Corporation to further
develop the potential for thalidomide.
Subsequent research has shown that it is effective in multiple myeloma, and it is now
approved by the FDA for use in this malignancy. There are studies underway to
determine the drug's effects on arachnoiditis, Crohn's disease, and several types of
cancers.
Clinical Trials
 Phase I: Drug is tested on healthy volunteers to
determine toxicity relative to dose and to screen for
unexpected side effects
Clinical Trials
 Phase II:
Drug is tested on small group of patients to see if
drug has any beneficial effect and to determine the dose level
needed for this effect.
Clinical Trials
 Phase III: Drug is tested on much larger group of
patients and compared with existing treatments and with
a placebo
Clinical Trials
 Phase IV: Drug is placed on the market and patients are monitored
for side effects
Assigned Reading
 Haffner Marlene E; Whitley Janet; Moses Marie Two decades of orphan product





development. Nature reviews. Drug discovery (2002), 1(10), 821-5. Link
Franks Michael E; Macpherson Gordon R; Figg William D Thalidomide. Lancet
(2004), 363(9423), 1802-11. Link
Abou-Gharbia, Magid. Discovery of innovative small molecule therapeutics.
Journal of Medicinal Chemistry (2009), 52(1), 2-9. Link
Paul, S. M. et al. How to improve R&D productivity: the pharmaceutical industry’s
grand challenge. Nature Reviews Drug Discovery (2010), 9: 203-214.
Jorgensen, W. L. The many roles of computation in drug discovery. Science (2004)
303: 1813-1818.
Butcher, E. C. et al. Systems biology in drug discovery. Nature biotechnology
(2004) 22(10): 1253-1259.
Optional Additional Reading
 Bartlett J Blake; Dredge Keith; Dalgleish Angus G The evolution of
thalidomide and its IMiD derivatives as anticancer agents. Nature reviews.
Cancer (2004), 4(4), 314-22. Link
 Cragg, G. M.; Newman, D. J. Nature: a vital source of leads for anticancer
drug development. Phytochemistry Reviews (2009), 8(2), 313-331. Link
 Betz, U. A. K. et al. Genomics: success or failure to deliver drug targets?
Current Opinion in Chemical Biology (2005), 9: 387-391
 Sams-Dodd, F. Target-based drug discovery: is something wrong? Drug
Discovery Today (2005) 10: 139-147.
Homework Questions
 What is an ‘orphan drug’. Why has the Orphan Drug Act been successful?
 Thalidomide is actually a mixture of two compounds. Draw their structures




and list the physiological effects of each.
What does ADMET stand for?
List several possible reasons for poor efficacy of drug candidates in in vivo
models.
Explain how structure-based design was used to develop an inhibitor with
improved selectivity for TACE over MMP-1 and MMP-9.
How can the pharmaceutical industry increase the probability of technical
success (p(TS))? What are the major causes of Phase II and III attrition?
Reference
 Mostly from Web