19- Fragment-Based Drug Discovery (S2E4)

Welcome to our deep dive into the world of fragment
-based drug discovery. Today, we're going to
be exploring how scientists are building new
drugs piece by piece, almost like assembling
a puzzle, starting with these tiny chemical pieces
called fragments. Yeah, you know, it's a really
clever approach that's been changing how we think
about discovering and developing your medications.
You know, if you think about it, most drugs work
by interacting with very specific proteins in
our bodies, and these proteins are like these
tiny machines with very specific shapes. And
the drug molecule, we call it a ligand, needs
to fit just right in a certain spot on that protein
to have the effect that we're looking for. Okay,
I think I'm starting to get the picture. So instead
of searching for a fully formed drug molecule
right from the beginning, scientists start with
these smaller pieces, these fragments, and see
how they interact with the protein. Exactly.
It's a bit like starting with, you know, those
corner and edge pieces of a puzzle, right, and
building from there. Traditional high throughput
screening or HTS is kind of like rummaging through
a warehouse full of complete puzzles. It can
be very overwhelming, and you might miss those
crucial pieces. Fragment -based drug discovery
is much more targeted. Wait, so you're saying
they don't even start with a complete drug molecule?
Yeah. That's really fascinating. How do they
even know where to begin if they're just working
with these tiny fragments? Well, that's where
the real ingenuity comes in. Scientists use a
variety of techniques to screen these fragments
and see which ones actually bind to that protein
that we're targeting. And they don't necessarily
need to find a perfect fit right away. So they're
not looking for love at first sight with these
fragments. Not exactly. Think of it more as a
first date situation. You're looking for a spark
of interaction that you can then build upon.
I like that analogy. Yeah, these initial fragments
might bind weakly, but that's okay. The beauty
of this approach is that scientists can then
optimize these fragments, tweaking their structure
bit by bit to improve that binding and ultimately
improve their effectiveness. That sounds amazing.
But I imagine linking those pieces together isn't
always straightforward. What are some of the
challenges that scientists face in that process?
You're right. It's not always just a simple snap
them together scenario. Sometimes linking those
fragments can change their overall shape in unexpected
ways, affecting how they then interact with that
protein. Other times, the link itself might be
unstable or it might interfere with the drug's
ability to actually reach its target in the body.
So it's a delicate dance of chemistry and structural
biology. So it's kind of like trying to fit puzzle
pieces together, but those pieces can warp or
break apart if you're not careful. That's a great
analogy. It really highlights the need for careful
design and optimization at every single step.
And that's where those powerful imaging techniques
you mentioned earlier come in. Right. We were
talking about X -ray crystallography in NMR before
we started recording. Can we dive into how those
techniques are used in fragment -based drug discovery?
Absolutely. X -ray crystallography allows scientists
to get a higher resolution, three -dimensional
view of the protein ligand complex. It's like
taking a snapshot of the puzzle pieces perfectly
fitted together. Okay, so you get this 3D snapshot,
but how do scientists use that information to
actually guide the design of those better fragments?
Are there specific things they look for in those
images? There are. They're looking for clues
about how that fragment is interacting with the
protein at the atomic level. Where are the hydrogen
bonds? Are there hydrophobic interactions? Are
there any areas of what we call steric clash
where atoms are bumping into each other? All
of this information helps them to understand
why a fragment binds well or why it doesn't and
how they can actually tweak its structure to
improve that interaction. So it's like having
a blueprint for building the perfect puzzle piece.
Precisely. And NMR spectroscopy complements x
-ray crystallography because it provides information
about the dynamics of the interaction. It's like
watching the puzzle pieces kind of wiggle and
shift as they interact, revealing how stable
that interaction is and how it changes over time.
So x -ray crystallography gives you the static
picture and NMR shows you the movie. Got it.
And by combining these techniques, scientists
can gain a really detailed understanding of how
these fragments are interacting with their target
protein, which is essential for guiding the design
of more potent and effective drugs. This is all
incredibly complex, but also really elegant.
I'm starting to see the power of this fragment
-based approach. But all this talk about puzzles
and blueprints makes me wonder, are there real
-world examples of drugs that have been developed
using this method? Oh, absolutely. There are
some remarkable success stories that really highlight
the power of fragment -based drug discovery.
One classic example straight out of an introduction
to medicinal chemistry is the development of
captopril, which is a medication used to treat
high blood pressure. Okay, tell me more about
that. How did fragment -based drug discovery
play a role in developing CAPTA -PRO? Well, research
has started with a simple dipeptide fragment
that's just two amino acids linked together.
They knew this fragment bound weakly to the target
enzyme, but it wasn't potent enough on its own
to be a useful drug. So they used a combination
of x -ray crystallography, NMR, and other techniques
to systematically add more fragments, essentially
growing the puzzle piece outward, until they
arrived at the structure of Captoprol. Wow. So
they literally built the drug molecule step -by
-step, testing and refining each modification
along the way, guided by these imaging techniques.
That's incredible. It really is. And Captoprol
went on to become a groundbreaking medication,
and it really demonstrated the potential of fragment
-based drug discovery to create effective treatments
for really serious diseases. So are there other
examples of drugs where this approach has been
successful? There are ADM -enabling technologies
in drug design and development. It describes
how understanding drug transporters, which are
proteins that help move drugs throughout the
body, played a key role in optimizing the antibiotic
Cifadroxal. They were actually able to use information
from studying what we call knockout mice that
lack a specific transporter protein to understand
how C -fidroxyl moves through the body. Wait,
so by studying mice that were missing a specific
transporter protein, they were able to figure
out how to make the drug work better in humans.
How does that work? It's a fascinating process.
By comparing how C -fidroxyl behaved in these
knockout mice versus normal mice, they could
really pinpoint the role of that transporter
protein in the drug's journey. This revealed
crucial details about how Cifadroxyl is reabsorbed
in the kidneys and how much of it actually reaches
the brain. This is all vital information for
ensuring the drug's effectiveness and safety.
That's amazing. So they're not just building
the drug molecule itself, but they're also figuring
out how to optimize its journey through the body,
almost like planning the best route for a delivery
truck. Exactly. And this kind of optimization
is essential for making sure the drug reaches
its target at the right concentration and with
minimal side effects. I'm really starting to
grasp the incredible complexity of drug discovery.
It's not just about finding the right puzzle
pieces, but it's also about understanding how
they fit together, how they move, and how they
ultimately reach their destination. You got it.
And that's just the tip of the iceberg. Oh, I
have a feeling we're just getting started. This
is already blowing my mind. Yeah, it really is
a multi -faceted process. We've talked about
building drugs from fragments, optimizing them,
and even understanding how they're distributed
in the body. But what about potential problems?
Could these fragments or the drugs built from
them have unexpected side effects? That's a great
point. It sounds like there's so much to consider
when developing a new drug. Are there any kind
of red flags scientists look out for during the
process? Absolutely. One crucial aspect is considering
what we call reactive metabolites. As drugs are
metabolized by the body, they can sometimes produce
byproducts that are, let's say, a bit unpredictable.
So these are like unexpected puzzle pieces that
don't quite fit in. And if you force them in,
they can actually damage the puzzle. Exactly.
And just like forcing in that extra piece could
damage the puzzle, these reactive metabolites,
if not carefully considered, can sometimes lead
to unwanted side effects or even toxicity. That
makes sense. Yeah. So, how do scientists identify
these reactive metabolites? Are there specific
tests or experiments they do? And, you know,
what kind of modifications can they make to the
drug structure to avoid these problems? ADME
-enabling technologies in drug design and development
really highlights the FDA's emphasis on early
assessment of these reactive metabolites. It's
like checking for potential troublemakers before
completing the entire puzzle. Scientists use
a variety of in vitro and in vivo tests to see
if a drug or its fragments produce these reactive
metabolites. So they're testing early and often
to catch these potential issues. What happens
if they find a problematic metabolite? Do they
have to scrap the whole drug? Not necessarily.
Sometimes they can modify the drug structure
to reduce or eliminate the formation of that
reactive metabolite. This might involve changing
a functional group, tweaking the molecule shape,
or even adding a new piece altogether. So they're
constantly problem -solving, going back to the
drawing board and fine -tuning those puzzle pieces
to make them safer and more effective. Precisely.
It's an iterative process, and sometimes it takes
a lot of trial and error to find that perfect
balance. This all makes me think about that time
I had to take. you know, antibiotics. I never
really considered how complex those little pills
actually are. Yeah, it's easy to take medications
for granted, but each one really represents years
of research development and careful optimization.
And even when a drug makes it through development
and is deemed safe and effective, there are other
factors that could affect its effectiveness.
Like what? Well, one fascinating aspect is the
concept of polymorphs. These are different crystal
structures of the same drug. Wait, so even if
you have all the right pieces, how you put them
together can still matter. That's wild. It is.
Evaluation of drug candidates for preclinical
development points out that these different crystal
structures can significantly impact a drug's
properties, like its solubility and absorption.
It's like realizing that arranging the puzzle
pieces one way makes them fit more snugly and
hold together better than another arrangement.
So scientists need to not only find the right
fragments, but also make sure they come together
in the most stable and effective way possible.
Absolutely. Polymorph screening is a crucial
step in drug development. Scientists use various
techniques to identify and characterize these
different polymorphs, ensuring they select the
most suitable one for the final drug formulation.
So even though we've made all these incredible
advancements in drug discovery, it sounds like
predicting the ultimate success of a drug built
from fragments is still incredibly challenging.
You're absolutely right. There are countless
factors that play from subtle changes in molecular
interactions to the intricate workings of the
human body. It's a complex puzzle with many moving
parts. It really highlights the incredible dedication
and expertise of the scientists who are working
so hard to develop these life -saving medications.
I couldn't agree more. They're constantly pushing
the boundaries of science and innovation to improve
human health. Speaking of innovation earlier,
we touched on artificial intelligence and drug
development as a source. I'm curious to explore
this further. Are these new technologies changing
how we solve the drug discovery puzzle? That's
a fantastic question and one that deserves its
own deep dive. The use of AI in drug discovery
is rapidly evolving and it has the potential
to really revolutionize the field. I'm all ears.
Tell me more about how AI is being used in drug
discovery. Well, AI algorithms can analyze these
huge amounts of data, identify hidden patterns,
and even predict how a drug might behave in the
body, all at a speed and scale that surpasses
human capabilities. It sounds like something
straight out of science fiction. Is this technology
already being applied or is it more of a future
possibility? It's happening right now. While
the field is still in its early stages, there
have already been some really remarkable achievements.
AI is being used to screen these virtual libraries
of millions of compounds, identify promising
drug targets, optimize lead compounds, and even
predict potential side effects. Wow, that's mind
-blowing. I never realized how much AI is already
impacting the drug discovery process. It's a
game changer, for sure. And by combining the
power of AI with fragment -based drug discovery,
scientists are really poised to make even greater
strides in developing new and innovative therapies.
That's incredibly exciting. I'm eager to see
what breakthroughs emerge from this fusion of
cutting -edge technology and scientific ingenuity.
Me too. It's an exciting time to be involved
in drug discovery. It sounds like we've covered
a lot of ground in our exploration of fragment
-based drug discovery. We've gone from building
drugs like Puzzles to understanding the challenges
of reactive metabolites and polymorphs. But before
we wrap up, I'm curious to hear your final thoughts.
So what's the big takeaway? you know, for our
listener who's now had this incredible introduction
to fragment -based drug discovery. Well, I think
the key takeaway is that fragment -based drug
discovery really represents a paradigm shift
in how we approach drug development. It's a move
away from this brute force screen towards a more
rational and targeted approach, guided by a deep
understanding of these molecular interactions
and, you know, an ever -growing toolkit of these
powerful technologies. That sounds revolutionary.
But I'm also hearing that it's not a guaranteed
success. Are there cases where this approach
just doesn't work? Yeah, that's a great question.
And you're right, it's not a magic bullet. There
are certainly cases where fragment -based drug
discovery faces challenges. Sometimes the fragments
just don't bind well enough to the target or
they're very difficult to link together. Other
times the resulting drug molecule might have
what we call poor pharmacokinetic properties,
meaning it doesn't get absorbed or distributed
very effectively in the body. So it's not like
a one -size -fits -all solution. Exactly. It's
another tool in the drug discovery toolbox. And
its success really depends on a whole host of
factors, including the nature of the target,
the availability of suitable fragments, and the
ingenuity of the scientists involved. Well, this
all underscores the importance of continued research
and innovation in this field. The more we understand
about these intricacies of drug target interactions
and the nuances of human biology, the better
equipped we'll be to design these safer and more
effective medications. I couldn't agree more.
And that brings us back to the potential of AI
and computational methods, which I think are
going to be huge game changers in this field.
It's exciting to think about all the possibilities.
AI seems to have this huge potential to revolutionize
so many aspects of our lives, including how we
discover and develop new drugs. Imagine being
able to virtually screen millions of potential
drug fragments. optimize their structures, and
even predict their potential for side effects,
all before setting foot in the laboratory. It's
incredible to think about, isn't it? And it's
not just science fiction anymore. The progress
being made in this area is really remarkable,
and I'm very confident that this convergence
of fragment -based drug discovery with AI and
computational methods holds a lot of promise
for the future of medicine. Well, on that note
of optimism and scientific advancement, we'll
have to wrap up our deep dive into the world
of fragment -based drug discovery. I think our
listeners walking away with a newfound appreciation
for the ingenuity, the dedication, and the sheer
complexity involved in bringing new medications
to the world. Absolutely. It's such a fascinating
field that's constantly evolving. And I encourage
our listeners to continue exploring and learning
about it. Who knows, maybe someday they'll even
be part of the next big breakthrough in drug
discovery. And on that note, thank you for joining
us on the Deep Dive. We'll see you next time
for another fascinating exploration into the
world of science and discovery.