All right, let's jump right in, shall we? Today
we are talking about preclinical research. Preclinical
research. It's a crucial stage in drug development,
but often overlooked. Absolutely. It's where
scientists really figure out if a drug is safe.
Right. And if it's effective. And how effective.
Before it ever even gets near a human being.
Yes, before it even gets into like first in human
studies. Exactly. This is all the work that happens
before then. And we are going to be your guides.
Yeah. Through this. intricate process today.
All right, buckle up. We'll uncover how researchers
use a combination of lab studies. Like in vitro.
In vitro. In glass. And animal studies. In vivo.
In vivo to build that solid foundation. So make
sure that when we do get to humans, we're doing
it as safely as possible. It's like being a detective
for drug molecules. It is. But let's start at
the very beginning. OK. What exactly is the purpose
of preclinical research? To gather information
about a drug's safety and efficacy before it's
given to a human, scientists want to know, how
does the drug behave in a living organism? Oh,
interesting. Does it reach the target tissue?
How is it broken down, eliminated? And most importantly,
does it cause any harm along the way? So it's
a bit like a dress rehearsal. Yeah, exactly.
Before the big opening night. Before we get on
stage. making sure everything runs smoothly and
there are no wardrobe malfunctions. For sure.
And the first act of this dress rehearsal takes
place in the lab. Right. With in vitro testing.
In vitro, yeah, in glass. In glass. So we're
talking about things that happen in test tubes
and petri dishes. OK. It allows researchers to
look at the drug in a very controlled environment.
So they're basically testing the drug's potential.
Yeah. Before introducing all the complexities
of a living organism. Right. Exactly. What are
some of the key tests they use at this stage?
Well, one important test is called the CACO2
permeability assay. CACO2 permeability assay.
So permeability, we're going to talk a lot about
permeability. OK. This is a specific type of
cell line derived from a human colon cancer cell.
Interesting. That allows us to create a model
of the intestinal lining. So it's like a mini
gut in a petri dish. Yeah. Basically, it's a
way for researchers to see, OK, if I dose this
drug orally, How well can it cross that intestinal
lining and get into the bloodstream? Oh, that's
so cool. Another one is called PAMPE. PAMPE?
Parallel Artificial Membrane Permeability Assay.
OK. I'm going to need you to break that down
for me. So it's a simplified model of a cell
membrane that helps researchers see how well
a drug can pass through a barrier. Got it. And
it has to pass through barriers to reach its
target in the body. I'm sensing a theme here.
Yes. Permeability. Permeability is super important.
Okay. It's all about how quickly... a drug can
get to where it needs to go in the body. So a
drug with high permeability is going to be absorbed
much more easily. Interesting. If a drug has
low permeability, it's going to take a lot longer
to get absorbed. So even if a drug is effective
in the lab, if it has low permeability, it might
not be so effective in the real world. Exactly.
That's really interesting. Which is one of the
reasons why in vitro testing is so valuable.
It helps identify these potential problems early
on. OK, so we've seen seeing the drug perform
on a cellular level. On a cellular level. What's
next? After the lab, we move on to animal studies.
or in vivo testing. In vivo. This is a really,
really crucial step because it allows us to bridge
that gap between the petri dish and the complexities
of a living organism. Right, because cells in
a dish can only tell us so much. They can only
tell us so much. In vivo testing, let scientists
observe how a drug behaves in a more realistic
setting. That makes sense. And to learn about
things like ADME, absorption, distribution, metabolism.
excretion. Like a drug's itinerary through the
body. Yeah, exactly. But choosing the right animal
model must be crucial. Super important. Different
animal models have different strengths and weaknesses.
Okay. And the choice depends on the specific
drug and the research question. Interesting.
So rodents are often used because they're small
and easy to work with. Makes sense. while larger
animals like pigs or primates might be used for
studies where their physiology is more similar
to humans. Interesting. Different animals for
different investigations. Yeah, exactly. Okay,
so we've established that a drug needs to get
to where it's going in the body. Yes. But how
does that actually happen? Right. I mean, when
we swallow a pill, it's not like it instantly
dissolves in our stomach. No, it does not. Like
an elka seltzer, right? More complicated than
that. Okay. The process of a solid drug breaking
down into smaller pieces and dissolving in a
liquid is called dissolution. Dissolution. An
only dissolved drug can be absorbed into the
bloodstream. OK. So dissolution is kind of like
unlocking the drug's power. Unlocking the drug's
power. And a key factor in how quickly a drug
dissolves is its particle size. OK, now you've
got my attention. Yeah. Particle size. Particle
size, yeah. How does that work? Think about it
like this. OK. If you want sugar to dissolve
quickly in your tea, do you use sugar cubes or
granulated sugar? Granulated sugar. Granulated
sugar, right. Why? More surface area. More surface
area? Dissolves faster. Dissolves faster, exactly.
The smaller the particles, the greater the surface
area and the faster it dissolves. So scientists
are practically playing with... microscopic building
blocks. It's kind of like that, yeah. To make
sure these medicines work properly. Right. I
never would have guessed that something as tiny
as particle size could have such a huge impact.
It's really interesting, yeah. Like it never
even crossed my mind. And scientists even have
an equation for it. Oh really? Called the noise
Whitney equation. The noise Whitney equation.
Which helps them understand and even predict
how different factors influence dissolution.
Okay, no need to go full chemistry professor
on us. I won't, don't worry. But give us the
gist. Yeah. How does this equation translate
to the real world? Well, it helps us understand
things like why a crushed pill works faster than
a whole pill. Oh, interesting. Crushing it increases
the surface area. Makes sense. Which speeds up
dissolution. Okay. And scientists can even use
this equation to model how a drug will dissolve
and be absorbed in the body. So it's like a scientist's
secret code for figuring out a drug's potential.
It's a tool in their toolbox, for sure. And you
mentioned some real -world examples, like Dagoxin
and Grizovina. How does particle size affect
them? So Dagoxin is a heart medication. And it's
a great example of how particle size can make
a difference in a drug's effectiveness. Studies
have shown that if you can reduce digoxin's particle
size, you can increase its bioavailability. Bioavailability.
How much of that drug gets into the bloodstream
to do its job. So in digoxin's case, smaller
particles means faster dissolution, which leads
to more of the drug being absorbed and ultimately
a better therapeutic effect. Makes sense. is
an anti -fungal medication. And it has very,
very low solubility. So it's hard for the body
to absorb. Right. Got it. But by reducing its
particle size, scientists have been able to improve
its dissolution and bioavailability. So even
though it's not very soluble. Right. They found
a way to make it work better. To make it work
better, yeah. It's like they outsmarted the drug's
inherent limitations. Exactly. This is all incredibly
fascinating. It is. It really highlights the
incredible ingenuity and attention to detail
that goes into drug development. For sure. It's
a meticulous process with many moving parts and
we've only just scratched the surface. Really?
There's more. Oh, yeah. This is amazing. There's
a lot more to come. OK, well, I can't wait to
hear all about it. You know, it's amazing how
much we can learn about a drug even before it
reaches a human being. Right. But all this preclinical
research is really just the beginning of a much
larger journey. You're talking about the journey
to getting a drug approved. Yeah. for use in
people, right? Well, exactly. The ultimate goal.
The ultimate goal. OK. And before a drug can
even be considered for human testing, researchers
have to submit a ton of information to the regulatory
authorities. Like the FDA. Like the FDA, yeah.
OK. It's called an Investigational New Drug Application,
or IND. IND. IND. It's like a drug's resume.
Yeah, it is. Before its big interview. Before
the big interview. Highlighting all its qualifications.
All of its qualifications. It includes a massive
amount of information about the drug, summarizing
everything that's been learned during the preclinical
phase. So like toxicology data, toxicology data,
ADME properties, ADME properties, dose finding
studies, dose finding studies, manufacturing
details. Manufacturing details. All of it. Wow.
That sounds pretty intense. It's a lot. What's
the purpose of all this scrutiny? Safety. Safety,
OK. The regulatory agencies want to make sure
that any drug entering human trials has a solid
foundation of evidence supporting its safety
and potential effectiveness. So they're basically
the gatekeepers. They are. Protecting the public
from potentially harmful or ineffective medications.
Exactly. OK. Makes sense. Yeah. So let's break
down some of these key components. OK. You mentioned
toxicology first. Yeah, toxicology. What kinds
of studies are done to evaluate a drug's safety?
So toxicology studies are designed to identify
any potential red flags, any harmful effects
the drug might have. And these studies are typically
conducted in animals using a range of doses and
durations of treatment. To really see what's
going on. To assess the impact on different organs.
So they're basically trying to find the drug's
breaking point? Yeah, you could say that. The
dose at which it starts to cause problems Right.
Researchers want to know how the drug behaves
at different levels of exposure, from those low
doses that might be used in humans to much higher
doses to reveal potential toxicity thresholds.
So they're really trying to understand the full
spectrum. The full spectrum, yeah. Of the drug's
effects. Yes. And what kind of signs are they
looking for in these studies? Looking for anything
out of the ordinary. OK. So changes in organ
function. OK. Liver or kidney damage, effects
on blood cells. Right. Even behavioral. changes
could be an indicator of toxicity. So if a drug
causes serious side effects in animals, that's
a pretty big red flag, right? It's a huge red
flag. And that's why these toxicology studies
are so important. They allow us to weed out those
potentially dangerous compounds before they even
get close to human testing. Got it. It's a big
deal. OK, so toxicology is all about making sure
a drug is safe. Right. But we also need to know
that it can actually do its job right. That's
where those ADME properties come in. Exactly.
ADME, absorption, distribution, metabolism, and
excretion. Like a drugs travel itinerary. Exactly.
So how do scientists actually study these properties
in the preclinical phase? They use a variety
of techniques. Okay. Sometimes even radio labeled
drug molecules. Wow. To track the drugs movement
throughout the body. So they can literally see
where it goes. They can see where it goes. That's
amazing. They study how it's absorbed from the
gut, how it's distributed to different tissues,
how it's metabolized by the liver, and how it's
excreted. So they're really following the Drugs
every move they're following it. Yeah Wow And
this information is crucial for understanding
how the drug will behave in humans Okay, how
long it will stay active in the body and what
might happen to it along the way, right? So it's
not just about will it work or not? Right also
about understanding all the nuances of how it's
interacting all the nuances. Yeah with the body
That's fascinating. It also helps determine the
appropriate dose for human studies. Oh, right
because too high of a dose could be dangerous.
Maybe very dangerous. And too low of a dose might
not be effective. Might not be effective at all.
So how do researchers figure out the right dose?
to use in humans. Dose finding studies. Dose
finding studies, okay. In animals, testing different
doses. Okay. To find that optimal range. To find
that sweet spot. Yeah, that sweet spot. Where
the drug is both effective and safe. Exactly.
Okay. And these studies also help determine how
often the drug needs to be administered. Oh,
okay, so like - Once a day. Once a day. Twice
a day or more frequently. Wow, so many factors
to consider. It's a lot. And then all of this
information. toxicology, ADME, dose finding gets
packaged up and sent off to the regulatory agencies
in the IND. In the IND, right? Right. But there's
more. Oh, there's more. We also need to understand
how the drug is broken down in the body. Oh.
And that's where metabolite profiling comes in.
Metabolite profiling. Sounds a bit like forensic
science. It kind of is. It involves identifying
and characterizing the different metabolites.
The breakdown products. The breakdown products,
right? That are formed when the drug is metabolized.
Exactly. So it's like analyzing a drug's fingerprints.
Yeah, it's like that. After it's been processed
by the body. Right. And those fingerprints can
tell us a lot about the drug's safety and effectiveness.
So it's not just about the drug itself, but also
about what it becomes. What it becomes in the
body. In the body. Some metabolites might be
inactive, while others could be active, and contribute
to the drug's overall effects. So some drugs
might actually become more potent. More potent,
yeah. After they're broken down. Exactly. While
others might produce metabolites that have unwanted
side effects. Right, so it's important to understand
that whole metabolic profile. The whole picture.
The whole picture, yeah. Before it moves on to
human tests. It's amazing how much complexity
there is. There is. In something that seems so
simple like taking a pill. It seems so simple.
Like a whole hidden world of chemistry happening
inside us. It is. It's a fascinating process.
It really is. And we're constantly learning more
about how drugs interact with the body. Okay,
so we've talked about toxicology, ADME, dose
finding, and metabolite profiling. We have. What
else goes into the IND? Well, we also need to
make sure that the drug is stable. Stable? Doesn't
degrade over time. OK. And that's where stability
testing comes in. Stability testing. Researchers
test the drug under various conditions. Like
temperature, humidity, that kind of. Temperature,
humidity, light. OK. To see how it holds up.
So even if a drug passes all the other tests
with flying colors. Right. It could still be
a no go if it doesn't have good shelf life. Exactly.
Yeah, makes sense. Yeah, we don't want a drug
that's losing potency before it reaches the patient.
And alongside stability testing, we also have
early analytical development. Early analytical
development. What exactly is that? This involves
developing methods to accurately measure the
drug in various samples, like blood or urine.
Interesting. And this is crucial for understanding
how much drug is present. Okay. During those
preclinical studies. So they're creating tools.
Yeah, they're creating tools. Subtract the drug's
journey. Exactly. And make sure it's behaving
as expected. Behaving as expected. It's incredible
how much work and detail goes into this preclinical
phase. It's a lot of work. It's like building
a case. It is. For a drug's potential. Yeah.
Gathering all the evidence to support its advancement
to human trials. You got it. It's a rigorous
process, but essential for ensuring the safety
and efficacy of new drugs. Absolutely. Well,
we are learning so much today. I'm glad. About
all the complexities of drug development. It's
really mind -boggling to think about all that
goes into preclinical research. It's a lot. Before
a drug even has the chance to be tested in humans.
Right? It's amazing. It really highlights the
dedication of all the scientists who are working
to bring new medicines to the world. Absolutely.
And there's one more tool that we use in preclinical
research that we haven't talked about yet. OK,
what's that? And that's the biopharmaceutics
classification system, or BCS. Oh yeah, the BCS.
The BCS. I remember you mentioning it earlier.
I did. Can you remind me what that's all about?
So the BCS is a way of categorizing drugs based
on their solubility and permeability. Oh. Remember
those two properties we talked about? Yes. Solubility
is how well a drug dissolves. Right. And permeability
is how easily it can pass through those cell
membranes. You got it. And those are both really
important. Hugely important. For a drug to be
effective. For a drug to work. OK. So the BCS
takes those two properties and uses them to classify
drugs into four different categories. Oh, cool.
OK, walk me through the categories. All right,
so class one drugs are the stars of the show.
OK. They have high solubility and high permeability.
Which generally means they're absorbed really
well. OK. Then we have class two drugs, which
have low solubility but high permeability. Their
absorption is often limited. by how well they
dissolve. So that's something that researchers
often try to optimize. Okay, so it's like class
one drugs are natural born athletes. Yeah. And
class two drugs need a little bit of coaching.
A little coaching, yeah. To reach their full
potential. To get where they need to go. OK,
what about the other two classes? So class three
drugs have high solubility, but low permeability.
OK. Their absorption is limited by their ability
to cross -cell membranes. Right. So getting them
to where they need to go in the body can be a
bit trickier. Yeah, I can see that. And finally,
we have class four drugs. OK. The problem children.
The problem children, all right. They have low
solubility and low permeability, making them
very challenging to develop. Right, so the BCS
is like a quick reference guide. Yeah, it is.
That helps researchers understand a drug's absorption
potential. Right. And identify any potential
challenges early on. Exactly. I like that. And
you know, the BCS isn't just used by researchers.
Oh, really? Regulatory agencies also rely on
it. Oh, wow. To make decisions about... bioequivalence
testing. Bioequivalence. Now there's another
term I need a refresher on. So bioequivalence
basically means that two different formulations
of the same drug are absorbed into the bloodstream
at the same rate and to the same extent. So they're
essentially interchangeable. Interchangeable,
yeah. From a clinical standpoint. Exactly. So
if I take a generic version of a medication,
it should work the same way as the brand name
version. Exactly, because they're bioequivalent.
Because they're bioequivalent. Oh, it's interesting.
And for those Class 1 drugs, The stars of the
show. The stars of the show with high solubility
and permeability, the FDA actually allows for
what's called a bio waiver. A bio waiver. What's
that? So that means they don't require those
extensive clinical studies to prove bioequivalence.
Interesting. So in vitro dissolution testing
can actually be enough. Wow. So for these well
-absorbed drugs, Lab tests can sometimes provide
enough evidence to show that they'll behave similarly
in the body. That seems like a huge win for drug
development. It is. Saving both time and resources.
Absolutely. And ultimately getting those drugs
to patients faster. Which is the goal. That's
really cool. The BCS is a great example of how
scientific understanding can be used to streamline
drug development and ultimately benefit patients.
Well this has been an incredible deep dive into
the world of preclinical research. I agree. I
feel like I've gained a whole new appreciation.
I'm glad. For the complexity and importance of
this stage of drug development. It's an important
stage. It's amazing how much goes on behind the
scenes. There's a lot that happens. Before a
drug even gets to the point of being tested in
humans. Yeah, most people don't even realize
it's happening. It's a whole hidden world. It
is. And for our listeners who want to continue
exploring this world. Yeah. Here's a final thought
to ponder. Imagine a world where we could perfectly
predict how any drug would behave in the human
body. That would be amazing. Based solely on
lab and animal data. Right. What advancements
in medicine would that unlock? Huge advancements,
I imagine. Could this be the key to personalized
medicine? It very well could be. Tailoring treatments
to each individual's unique biology. It's an
exciting possibility. It's an exciting possibility
for sure. It is. Until next time, keep diving
deep.