68 - Regulatory Review: What the FDA Expects (S5E8)

You know, bringing a new drug to market. Well,
it's not just about the science, right? You need
to navigate a pretty intricate regulatory landscape.
That's right. It's years of research, tons of
money invested. The ultimate goal is to help
patients. Exactly. And understanding what the
FDA expects can make or break the whole thing.
It really can. Now, for our listeners out there
who are maybe knee deep in this world or... Just
curious about how new medications are developed.
Today's deep dive is all about demystifying what
the FDA is looking for in that all -important
review process. You got it. And whether you're
preparing a submission or just fascinated by
the journey of a new drug from the lab to the
pharmacy, we're going to break down those key
data points. That's right, the presentation formats,
those crucial review criteria. Everything you
need to know to align with FDA standards. We'll
also unpack the review process itself, shed light
on those complete response letters, and see what
insights we can glean from the FDA's public review
and approval documents. So think of this as your
guide to understanding those FDA expectations.
To really get a comprehensive view, we've dug
into a bunch of sources. Yeah, case studies from
the world of drug discovery. the fundamentals
of medicinal chemistry, the ins and outs of pharmacokinetics,
how the body processes the drug, and, of course,
the essential regulatory documents like the Code
of Federal Regulations, the CFR. All right. So
let's get down to brass tacks here. Sure. When
a company is putting together their application
for a new drug, what kind of information does
the FDA really want to see? Well, The core of
it is understanding how the drug moves through
the body and what it does once it's there. OK,
so pharmacokinetics. Yeah, PK and pharmacodynamics,
or PD. Right, right. PK is all about how the
body interacts with the drug. Think absorption,
distribution, metabolism, excretion. That's ADME.
Right. And PD is about how the drug interacts
with the body. Gotcha. So it's a two -way street.
Now, it's kind of surprising how even small changes
in how the drug is formulated can have a big
impact on its PK properties, right? I was reading
about OSI -906. Oh, absolutely. They found that
using water or a pH -adjusted saline solution
for OSI -906 resulted in much better PK than
using a PEG solution. Interesting. So it highlights
how even seemingly minor formulation tweaks can
make a huge difference in how the drug behaves.
And that can directly impact its efficacy and
the likelihood of getting FDA approval. Right,
right. And I guess when it comes to showing how
a drug is eliminated from the body visual aids
are helpful. For sure. You'll often see data
presented in two types of plots. rectilinear
and semi -logarithmic. So rectilinear would show
the total amount of drug eliminated over time.
Exactly. And semi -logarithmic plots use a special
scale. It helps visualize the rate of elimination
and helps calculate the drug's half -life. That's
the time it takes for the drug concentration
in the body to be cut in half. This is crucial
for determining the right dosing frequency. Makes
sense. What about the concept of apparent volume
of distribution? Yeah, that's an important one.
It's not a real physical space, but think of
it this way. It tells you how widely a drug spreads
throughout the body compared to the bloodstream.
Interesting. Imagine dissolving a teaspoon of
sugar in a glass of water versus in a bathtub.
The sugar in the bathtub scenario would have
a much larger apparent volume, even though it's
the same amount of sugar. Right. So for drugs,
a large apparent volume of distribution means
it's getting into tissues, not just staying in
the blood. Gotcha. That's crucial because it
affects the initial concentration you can expect
in the blood after you give a dose. So if a drug
spreads more widely, you might need a higher
dose to begin with. Exactly, and then there's
the dosage regimen. How often you give the drug
the route of administration. Is it a single shot,
a continuous infusion, or multiple doses over
time? Right, that makes sense. All these factors
influence the drug's concentration in the blood
over time. Okay, so it's not just how it gets
in and out, but maintaining the right levels
for it to be effective without causing too many
side effects. Now, we've talked about measuring
drug levels, and this is where bioanalytical
method validation comes in. and making sure that
our tools are up to snuff. Precisely. The assays
we use to measure drug concentrations, especially
those using antibodies, those are called amino
assays. They need rigorous validation. OK. If
your measuring stick is off, any measurement
you take will be off too. So robust bioanalytical
validation ensures that the measuring stick for
drug concentrations is accurate and precise.
Right. That makes sense. I know the ICH guidelines
Q2A and Q2B. are important here? Definitely.
Specificity is a big one. It means the assay
is measuring only the drug of interest and not
getting confused by other substances in the sample.
Right. Now, for antibody -based assays, the acceptable
levels of accuracy and precision might differ
from traditional chemical tests. Interesting.
They're evaluated on a sample -to -sample basis.
So there's a little more wiggle room, I guess.
Yeah, acknowledging the inherent variability.
But you still need to demonstrate that the results
are reliable. Absolutely. Another important point
is that antibody -based assays often don't have
a straightforward linear relationship between
the amount of drug and the signal they produce.
You need a good number of calibrators. These
are samples with known drug concentrations to
accurately define the curve used to determine
the unknown drug levels in patient samples. Right,
right. And crucially, you have to make sure your
assay isn't reacting to the drug's metabolites
or any communications. Gotcha. That could throw
off your measurements. Now let's switch gears
a bit and talk about how the drug is actually
manufactured, chemistry, manufacturing, and controls.
CMC. It sounds like a whole world unto itself.
Oh, it definitely is. The FDA is very focused
on CMC information. They want to be sure each
batch of the drug is consistently produced at
a high standard of quality. Right. Makes sense.
Starting with the plant equipment, which needs
to be well designed, right? Made of suitable
materials that can be easily cleaned and prevent
contamination. You know, all that's detailed
in CFR 21 part 110. So it's not just about the
fancy equipment, but the practicalities of maintenance
and cleaning. Exactly. Thorough cleaning procedures
are crucial. And then you have the lab facilities,
the quality control processes. Right. All that
ensures that both the starting materials and
the final product meet their specifications,
which is covered in CFR 21 part 111. OK. What
about packaging and labeling? Seems like an area
where errors could be disastrous. Absolutely.
CFR 21 parts 211 and 202 outline the need for
specific procedures for all packaging and labeling
operations. The goal is to prevent mix -ups,
making sure the correct drug and dosage are packaged
accurately. Okay, so it's not just about the
drug itself, but the whole process of getting
it to the patient safely. We often hear about
GRP and GMP. Yeah. How do they fit into this
CMC world? Good laboratory practice, GLP, ensures
the quality and reliability of those preclinical
safety studies. You know, those foundational
studies before human testing. Good manufacturing
practice, or GMP, applies to the entire process
of making both the active drug and the final
product. Gotcha. It's a comprehensive set of
guidelines that ensure the drug is produced and
controlled according to strict quality standards.
OK, so GLP for the initial safety studies, GMP
for the whole manufacturing process. And what
about those newer technologies like PT and automation
and manufacturing? Are they on the FDA radar?
Process analytical technology, PT, and automation
are gaining ground. They allow for real -time
monitoring and control of the manufacturing process.
Right. While not always required, using these
technologies shows the FDA that you're committed
to improving efficiency and quality consistency.
OK, so that's a plus. Yeah. We've covered how
the drug acts in the body, how we measure it,
and how it's manufactured. Let's move on to the
preclinical phase. Sure. What does the FDA look
for in those initial studies? This is where we
establish initial safety and gather the first
evidence of efficacy before giving the drug to
humans. The FDA will be scrutinizing the toxicology
program. They want to see a clear rationale behind
the animal species chosen for those studies.
Right. So you can't just test on any animal.
You have to show why that species is relevant
to humans. Absolutely. Then you have the in vivo
models used to evaluate the drugs activity. In
cancer research, they often use rodent models
with implanted tumors like the colon 38 or MAM16C.
They even have orthotopic models where the tumor
is placed in the same organ as it would naturally
occur and metastatic models to study how cancer
spreads. That's fascinating. Yeah, and techniques
like using fluorescent tags like GFP allow researchers
to actually visualize this spread. Amazing. And
how do scientists initially identify potential
drug candidates in preclinical research? There
are a couple of common strategies. Ligand -based
screening uses knowledge of existing active compounds
to find new molecules with similar properties.
And they use techniques like QSRR, which relates
a molecule structure to its activity, or pharmacophore
modeling, which focuses on the essential 3D features
needed for binding to the target. Interesting.
Structure -based screening uses the known 3D
structure of the drug's target protein to design
molecules that might fit and interact with it.
Gotcha. reading that, understanding how the body
breaks down a drug is important. Oh absolutely.
The FDA wants to know if a drug is transformed
into toxic metabolites, especially through CYP
metabolism in the liver. Right. Formation of
reactive metabolites can be a big concern. They
could damage organs. OK, so the liver's role
in breaking down the drug is closely examined.
It is. And even something as basic as the drug's
physical form can matter, like whether it's a
powder or a solid. The solid state properties
of a drug, like polymorphism, or whether it's
amorphous or crystalline, can affect its solubility
and how quickly it dissolves. A drug has to dissolve
to be absorbed. So these properties can affect
how much of the drug is actually available to
the body? So it's about more than just the molecule
itself. It is. We built the foundation with preclinical
data. Now it's time for clinical trials in humans.
What are the FDA's expectations for this phase?
Well, the FDA expects well -designed and controlled
trials. They need to show substantial evidence
of the drug's efficacy and provide more information
about its safety profile in humans. Right. Clear
and precisely defined primary and secondary endpoints
are a must. Right, the primary endpoint being
the main outcome the trial was designed to measure.
That's right. Now, how many trials are usually
needed to provide substantial evidence of efficacy?
Typically, the FDA looks for positive results
from at least two well -controlled phase three
studies. They want consistent, reproducible evidence
of benefit. One trial could be a fluke, right?
Right, right. But it's not a hard and fast rule.
Sometimes a single, large, very persuasive trial
with supporting evidence might be enough. When
analyzing trial results, I've come across the
terms intention to treat and protocol analysis
populations. What's the difference and why do
they matter to the FDA? Intention to treat or
ITT analysis includes all participants who are
randomly assigned to a treatment group, whether
they actually receive the treatment or finish
the study. It helps preserve the benefits of
randomization and provides a more conservative
estimate of the treatment effect. PER protocol
analysis only includes data from participants
who stuck to the study protocol. OK, so it's
a stricter selection of participants. Right.
The PER protocol analysis gives a clearer picture
of efficacy in those who took the treatment as
intended, but it can introduce bias by excluding
patients who may be dropped out for reasons related
to the treatment. So the FDA looks at both types
of analyses, but might emphasize the ITT results,
especially in superiority trials. Right, because
those trials aim to show that a new treatment
is better than a control. Gotcha. Now, what about
those expedited pathways? Oh, yeah. I'm talking
about breakthrough therapy designation and accelerated
approval. These are really important. They speed
up the development and review of drugs that address
serious unmet medical needs. So if there's no
good treatment for a disease, These pathways
can help get promising new drugs to patients
faster. Exactly. That's great for patients who
are waiting for new treatment options. It is.
Shifting gears a bit. Sure. What are the key
criteria the FDA uses to evaluate a new drug?
The big four are safety, efficacy, quality and
the risk benefit assessment. Makes sense. Safety
comes first. They'll scrutinize all the safety
data from preclinical and clinical studies. They're
looking at potential risks, things like organ
toxicity, harmful metabolites. Right. Even if
a drug shows great efficacy, safety concerns
could derail approval. Absolutely. So what about
efficacy? Well. The drug must show a meaningful
benefit. Okay. They'll be looking for statistically
significant and clinically relevant results from
those well -controlled trials. Right, right.
And quality, of course, ties back to the CMC
information. Exactly. They need to be confident
that the drug can be manufactured consistently
at a high standard. And the risk -benefit assessment.
It sounds like a careful weighing of pros and
cons. It is. The FDA carefully considers the
potential benefits for the target patients against
potential risks. Gotcha. And remember, even drugs
with side effects can be approved if the benefits
outweigh the risks. Right. It's always about
that balance, right? It is. And finally, the
labeling. Oh, the labeling is crucial. It's got
to accurately communicate the drug's risks and
benefits, and it's got to have clear instructions
for its use. Right, and that's covered in CFR
21 part 202. Now, our sources don't go into detail
about specific successful submissions, but it
sounds like everything we've talked about so
far is what contributes to a positive review
from the FDA. Right. Optimizing the drug's PKPD,
ensuring accurate measurements, strong pre -clinical
and clinical data, robust manufacturing processes,
these are the cornerstones of a successful regulatory
submission. And those expedited pathways also
suggest that there have been successful submissions
under those frameworks. Exactly. Okay, so let's
talk about the FDA review process itself. What
happens once a company submits all the information?
Well... For a traditional drug, it's the new
drug application, or NDA. Right. And for a biologic
drug, it's the biologics license application,
or BLA. OK, gotcha. And then what? The FDA has
teams of experts who examine all that data, from
lab studies to clinical trials, manufacturing
details, the whole nine yards. So physicians,
pharmacologists, chemists, statisticians? All
of them. It's a really thorough process. And
the FDA can also have meetings with the company
throughout the development process. Right, like
those pre -phase three meetings. Exactly. They
can discuss their plans for the pivotal trials
and get feedback from the FDA. OK, so it's not
just a one -way submission. There's back and
forth. That's right. And for over -the -counter,
or OTC, drugs, there's a specific process called
a filing determination outlined in CFR 21 Part
330. The FDA first checks if the initial submission
is complete enough to begin a full review. Gotcha.
Now, sometimes an application doesn't get approved
right away. What happens then? Then the company
might receive a complete response letter, a CRL.
OK, what does that mean? It basically means the
FDA can't approve the application in its current
state. The CRL outlines the specific deficiencies
that need to be addressed. What kind of deficiencies
are we talking about? It could be anything. They
might need more clinical data, more safety information,
or maybe there are issues with the manufacturing
process or quality control. OK, so it's not necessarily
the end of the road. No, not at all. It's a setback,
but the company gets valuable feedback. They
can address the FDA's concerns, maybe do more
studies, revise their manufacturing, or analyze
existing data differently. Right. And then they
can resubmit the application. OK. You mentioned
earlier that the FDA often makes summaries of
their review process. and approval letters available
to the public. Why are those documents so important?
They offer a glimpse into the FDA's thinking.
They often highlight the key data they considered,
the reasons for their decisions, and any conditions
attached to an approval. It's a learning opportunity.
It is. Companies going through the process can
learn from those who've gone before, you know?
Right. See what worked, what didn't. Exactly.
It's a wealth of information that can help future
applicants prepare stronger submissions. Okay,
so for our listeners out there, the key takeaway
here is that robust data is essential across
the board, how the drug works, how it's made,
how it's tested in animals and humans. It's not
just about having the data, it's about presenting
it clearly and in a way that the FDA expects.
And above all, demonstrating that the drug is
safe, effective, and consistently high quality.
Understanding these expectations is key to successfully
navigating the regulatory maze. Absolutely. And
as a final thought, consider this. Science and
technology are advancing rapidly. You know, we've
seen AI make its way into drug discovery. The
methods for generating and presenting data will
evolve. But the need to show that a drug is safe,
effective, and consistently manufactured to a
high standard, those will always be the cornerstones
of regulatory review. That's a great point. It
seems like we're on the brink of major changes
in how medicines are discovered and developed.
The regulatory landscape will have to adapt.
This has been a really informative deep dive.
It has. Thanks so much for your expertise. Yeah.
And to our listeners, we encourage you to explore
those publicly available FDA resources. Dig deeper
into those case studies. Until our next deep
dive, keep exploring the fascinating world around
us.