Chapter 46: Immunopharmacology, Biologicals, and Gene Therapy

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Welcome back to The Deep Dive.

Today we are shifting gears into high intensity mode.

We certainly are.

We're continuing our Last Minute Lecture series and this one is designed specifically for the college student who has a pharmacology exam looming on the horizon.

Right.

And you need to download a massive amount of information without suffering through a monotone reading of the textbook.

It is the break glass in case of emergency study tool.

But honestly, even if you aren't cramming, today's topic is, well, it's arguably the most exciting section of the entire curriculum.

I think so too.

We are looking at Chapter 46 of Brenner and Steven's Pharmacology, sixth edition.

The title of the chapter is Immunopharmacology, Biologicals and Gene Therapy.

And I have to admit, when you first glance at the syllabus, those words look incredibly dense.

They do.

It feels like we're leaving the world of, you know, traditional aspirin and beta blockers and entering a science fiction novel.

That is actually a very fair assessment.

I mean, for most of the history of medicine, pharmacology was the study of small molecules.

Right.

Chemicals.

We synthesize chemicals in a lab, press them into pills and, you know, hope they would float into a cell and tweak an enzyme.

But Chapter 46 represents the modern era.

We are talking about biologicals.

These aren't synthesized.

They are grown.

They are massive, complex proteins that mimic or manipulate the immune system with

sniper -like precision.

And looking at the source material here, the scope is just breathtaking.

We aren't just treating symptoms anymore.

Not at all.

We were talking about drugs that can hunt down cancer cells based on their genetic signature.

Vaccines that program your own cells to build viral proteins.

And, well, therapies that literally rewrite the DNA in a patient's body to cure blindness.

It is the rock star chapter.

It really is.

These are the drugs that make the headlines.

But for the student listening, it also presents a new challenge because the rules of administration,

the side effect profiles, and even the naming conventions are completely different from what you learned in the cardiovascular or autonomic chapters.

So our mission today is to decode Chapter 46.

We are going to break down the explosion of monoclonal antibodies, those famous Mab drugs.

Yep, the Mabs.

We will look at how they are revolutionizing cancer treatment from solid tumors to leukemias.

We'll look at how they've crossed over into treating asthma, cholesterol, and migraines.

Then we will tackle the essentials of vaccines, organ transplant drugs, and finally, the frontier of gene therapy.

It is a lot of ground to cover, but if you understand the underlying physiology, the why, the drug names will stick.

Let's start with that big picture then.

The test describes an explosion of monoclonal antibodies or Mabs entering the market.

Why has this specific class of drug taken over medicines so aggressively?

It really comes down to one word,

specificity.

Specificity.

Think about traditional chemotherapy.

What does it do?

It targets rapidly cells that attacks the tumor, sure, but it also attacks your hair follicles, your gut lining, and your bone marrow.

It's a shotgun approach.

It's a total shotgun approach.

Monoclonal antibodies are different.

They are proteins designed to bind to one specific sequence of amino acids on an antigen.

So instead of bombing the whole city, we are sending a special ops team to one specific address.

Precisely.

That's a great analogy.

And the targets are usually cell surface antigens receptors sitting on the outside of a cancer cell,

or free floating cytokines, which are the signaling proteins the immune system uses to communicate.

But there is a huge physiological constraint that the text highlights right at the beginning, and this is absolutely crucial for anyone taking a test on administration.

You are referring to the fact that you cannot take these as a pill.

Right.

Students often miss this.

These are proteins.

I mean, if you swallow a monoclonal antibody,

your stomach acid and your proteolytic enzymes will treat it exactly like a piece of steak.

They will chop it up into amino acids and the drug is destroyed before it ever reaches the blood.

So logically, every single drug we discussed today in this category must be administered parentally.

Correct.

They are almost exclusively intravenous, so IFE or intradermal.

They have to bypass the gastrointestinal tract completely to remain intact.

There is another general principle mentioned in the intro regarding safety because these are large, often foreign proteins being injected directly into the bloodstream.

They carry a specific risk profile that small molecules usually don't.

Hypersensitivity.

Absolutely.

Even with the best engineering, you are introducing a large biological structure into the body.

Right.

The immune system is trained to recognize self versus non -self.

If it flags the drug as non -self, you can get anything from a mild infusion, reaction like fever, chills, a rash to full -blown anaphylaxis.

Wow.

That is a universal monitoring requirement for this class.

Okay, let's get into the structure then.

The text mentions the fab fragment.

For a visual learner, how should we picture these molecules?

Imagine the classic capital letter Y.

That is the shape of an antibody.

The stem of the Y is the constant region that interacts with the immune system's machinery.

But the tips of the two arms of the Y, that is the fab region,

it stands for fragment antigen binding.

So the ticks of the Y are the sticky parts.

They are the sticky parts.

They're the lock that fits only one specific key.

That fab region is engineered to bind to the target antigen with incredible affinity.

And once it binds, it can do a few things.

Like what?

It might just sit there and block a receptor -like jamming gum into a keyhole so the real key can't get in.

Okay, a physical block.

Or it might act like a beacon flagging the cell for destruction by other immune cells.

Before we start throwing drug names around, we have to address the elephant in the room.

Names?

The names.

They look like someone just fell asleep on a keyboard.

Rituximab, Trastuzumab, Bavitizumab.

The text claims there is a logic to this.

There is absolutely a logic and it is super high yield for exams.

If you learn the code, you can tell what a drug is and where it came from without ever having seen it before.

Let's crack the code.

The suffix is obviously enashmab.

Right.

Anamab simply stands for monoclonal antibody.

Sometimes you'll see onmonab, but it's usually just nomab.

The real story is told in the syllables preceding the suffix.

Okay.

Let's start with the source.

This tells us how the antibody was manufactured.

And this connects back to the history of the technology.

The text mentions we started with mice.

We did.

The first generation of these drugs were purely marine.

They came from mice.

The code letter for that is O.

So if the drug ends in omab.

It is 100 % mouse protein, muromonab is an example.

And the problem with mouse antibodies is that the human immune system hates them.

It recognizes them as foreign immediately and attacks, leading to severe hypersensitivity reactions and a short half -life because the body just clears them out so fast.

So scientists had to make them look more human.

Exactly.

They started swapping out parts of the humi protein.

If you see upside, that means it is chimera.

Think of the chimera from mythology, a lion with a goat's head.

In this case, it's usually about say 25 to 30 % mouse, mostly the sticky fab tips, and the rest is human.

So AC is the mix.

And then we have ZOO.

ZOO stands for humanized.

This is even better.

It's about 90 to 95 % human with only the tiniest part of the mouse antigen binding site remaining.

And finally, if you see U, it is fully human.

So the progression from O to C to ZOO to U basically represents the evolution of safety and reduced immunogenicity.

Precisely.

Now look at the syllable before the source code.

That tells you the disease target.

This is the part that actually helps you guess the clinical use.

Yep.

If you see E2, it targets a tumor.

Easy enough.

If you see BT, it targets a virus.

And if you see EC or EC, it targets the circulatory or cardiovascular system.

Okay.

So let's test this.

Take the drug Roteximab.

Okay.

Break it down from the end.

E -smabe means monoclonal antibody.

EC means it is chimeric.

So it's a mouse -human hybrid.

And two is buried in the middle there telling us it targets a tumor.

So Roteximab is a chimeric monoclonal antibody used against cancer.

You nailed it.

And knowing that it is chimeric, the Echaia tells you that it carries a higher risk of infusion reaction than a fully human one.

So you'd want to monitor that patient very closely.

That is incredibly useful.

Now the text includes a diagram, figure 46 .1, detailing the hybridona technique.

This explains how we actually manufacture these things.

It seems like a lot of trouble just to get a protein.

It is a brilliant solution to a biological problem.

I mean, here's the issue.

To make a specific antibody, you need a B cell.

Right.

B cells are the factories.

But if you take a B cell out of a mouse and put it in a petri dish to farm it, it dies.

It has a short lifespan.

Oh, I see.

It divides a few times and then it just quits.

So you have the factory, but the workers keep dying before they can produce enough product to sell.

Exactly.

So the scientists ask, what kind of cell lives forever and divides infinitely?

A cancer cell.

Right.

Specifically, a myeloma cell, a cancer of plasma cells.

So here is the recipe in figure 46 .1.

Step one, inject a mouse with the antigen you want to target.

Okay.

Let the mouse's immune system get angry and build B cells against it.

Step two.

Harvest the spleen of the mouse.

Isolate those activated B cells.

And step three is the sci -fi part.

You fuse the healthy B cell with the immortal myeloma cell.

You physically merge them into a single new cell type called a hybridoma.

Wow.

This new cell has the genetic instructions from the B cell to make the specific antibody, but it has the immortality and aggressive growth of the cancer cell.

It's an undead antibody factory.

It is.

You then clone that hybridoma and it will churn out unlimited quantities of that specific monoclonal antibody forever.

That is how we mass produce these drugs.

That is fascinating.

Okay.

Let's move from the factory to the clinic.

We're going to explore the high yield drugs mentioned in the chapter, starting with targeted cancer therapies.

The techs groups these by their mechanism.

The first group targets the grow signal.

Right.

The EGFR inhibitors, epidermal growth factor receptor.

Let's establish the physiology first.

What does EGFR actually do in a healthy cell?

Think of EGFR as a receiver dish on the surface of a cell.

When a growth factor floats by and hits the dish, it sends a signal down into the cell that says divide.

Okay.

So it's a gas pedal.

It's a gas pedal for cell proliferation.

And in cancer.

In many cancers, specifically colorectal and head and neck cancers, this receptor is massively overexpressed.

The cell has thousands of these receiver dishes.

It becomes hypersensitive to growth signals, causing it to divide uncontrollably.

So the drug cetuximab enters the picture.

Cetuximab is an antibody that binds directly to the EGFR dish.

It physically covers it up.

Okay.

This prevents the growth factor from docking, but it does something else too.

It prevents the receptor from dimerizing.

Bimerization.

That's when two receptors pair up, right?

Yes, exactly.

For the signal to go through, two EGFRs usually have to hug.

Cetuximab stops the hug.

No hug, no signal.

No hug, no signal transduction, no cell division.

The cancer cell eventually triggers apoptosis and dies.

However, there is a massive B -U -T here.

The text puts a big warning sign around the RAS mutation.

This is something that traps students all the time.

This is critical.

You have to understand the pathway.

The EGFR is the button on the outside of the cell.

Right.

But that button is connected to a wire inside the cell that carries the message to the nucleus.

The first part of that wire is a protein called ROS.

Okay, so EGFR connects to ROS, which passes the signal down.

Correct.

Now imagine you have a patient with colon cancer.

You give them cetuximab.

You block the button on the outside.

But the patient has a mutation in the RAS gene.

What does the mutation do to the RAS protein?

It locks it in the on position.

The wire is sparking and sending grow signals on its own, regardless of what the button on the outside is doing.

So blocking the EGFR with the drug is completely useless because the signal is originating downstream of the block.

Exactly.

It's a perfect way to put it.

If the RAS is mutated, cetuximab will not work.

It is physiologically impossible.

Therefore, the text emphasizes you must test for the KRES mutation before prescribing this drug.

You can only use it on wild type or normal RAS patients.

That is a perfect example of why you can't just memorize drug names.

You have to know the pathway.

Right.

Before we leave EGFR, let's quickly touch on the adverse effects.

If I block epidermal growth factor,

what happens to my epidermis?

Your skin gets angry.

The most common side effect by far is an acneform rash.

It looks like bad acne on the face and chest.

Oh, interesting.

Interestingly, clinical studies have shown that patients who get the rash often have better cancer outcomes.

It's a sign the drug is hitting its target.

Moving on to another growth factor receptor, but this time for breast cancer.

This is the HER2 story.

HER2.

It stands for human epidermal growth factor receptor 2.

It's a cousin of EGFR.

And box coming with 6 .1 in the text outlines a case study that really humanizes this.

We have a 47 -year -old woman who discovers a breast mass.

The biopsy shows invasive ductal adenocarcinoma.

Right.

And standard procedure now is to test the genetics of that tumor.

In her case, the report comes back, HER2 positive 3 plus 3.

This means her cancer cells are coated in these HER2 receptors, way more than normal.

About 20 to 30 % of breast cancers are HER2 positive.

And historically, those were bad.

Historically, these were the aggressive, scary cancers with poor survival rates.

But then they treated her with trastuzumab, which is widely known as herceptin.

Yes.

Trastuzumab is a monoclonal antibody that targets that HER2 receptor.

In the case study, this patient actually had metastasis to the liver, a grim prognosis.

But they started her on trastuzumab combined with pachlotexel, which is a chemotherapy agent.

And the result?

Complete remission.

The text notes she is still disease -free five years later.

Trastuzumab turned a death sentence into a manageable and often curable condition.

How does it work?

It binds to HER2, blocks the signaling, and it also flags the cancer cells for the immune system to come and eat them.

But like C -tuzumab, there is a specific organ toxicity we have to watch for.

And it is not the usual chemo -nausea.

No, it is cardiotoxicity.

Trastuzumab can damage heart muscle cells.

It can lead to a decrease in the left ventricular ejection fraction, which is basically heart failure.

Why the heart?

It turns out normal heart muscle cells also have some HER2 receptors that play a role in their maintenance and repair.

I see.

So any patient on Trastuzumab needs regular echocardiograms to monitor their heart function.

The text also briefly mentions Pertuzumab.

Is this just Trastuzumab 2 .0?

It's a partner.

Remember dimerization, the receptors hugging?

HER2 loves to hug other receptors, like HER3.

Pertuzumab specifically blocks that heterodimerization.

Often oncologists will use Trastuzumab and Pertuzumab together, it's called the double blockade, to hit the receptor from two different angles.

Let's shift mechanisms.

We've talked about blocking the grow signal.

Now let's talk about starving the tumor.

Angiogenesis inhibitors.

This is the drug Bevacizumab, or Avastin.

The concept here relies on the fact that tumors are metabolically expensive.

They grow so fast, so they need a massive amount of oxygen and sugar.

So they need blood.

They need a blood supply.

So a growing tumor releases a distress signal called VEGF, vascular endothelial growth factor.

This protein floats out and tells the nearby blood vessels, hey, sprout new branches and grow towards me.

So the tumor builds its own supply lines.

Exactly.

Bevacizumab is an antibody that does not bind to a cell.

It binds to the VEGF protein itself while it is floating in the circulation.

It just mops up the signal.

So the command to build blood vessels never reaches the endothelial cells.

The supply lines are cut and the tumor starves.

That is the mechanism.

But think about the side effects.

If you shut down the body's ability to make new blood vessels, when is that a problem?

When you are trying to heal a wound.

Exactly.

Wound healing relies on angiogenesis.

So the major risks with Bevacizumab are wound adhesons.

So surgical wounds popping open and bleeding.

Wow.

You absolutely cannot give this drug for at least 28 days before or after a major surgery.

It also carries a risk of GI perforation holes forming in the gut because the gut lining needs constant repair.

That is a very high yield contraindication.

Okay, let's move to part three of our outline.

The immune checkpoint revolution.

The text calls this a quiet revolution, but frankly, it's been pretty loud.

It has.

This work won a Nobel Prize.

And it deserved it.

It deserves it.

This changed everything.

The old way of thinking was stimulate the immune system to attack cancer, but it never worked well.

Right.

The new way of thinking is the immune system wants to attack the cancer, but the cancer is holding it back.

Let's cut the restraints.

Let's unpack the checkpoint analogy.

Your T cells, the killer cells of the immune system, are like attack dogs, but you don't want them biting your own healthy organs.

So the body has built -in leashes or checkpoints.

These are receptors that, when pressed, tell the T cell to go to sleep or relax.

And cancer exploits this.

Cancer is very smart.

It reaches out and presses those off buttons.

It tricks the T cell into thinking the tumor is safe.

The checkpoint inhibitors block that interaction.

They cut the leash.

They cut the leash.

They take the brakes off the T cell.

The first one mentioned is epilimumab.

Epilimumab targets a receptor called CTLA4.

CTLA4 is a down regulator that happens early in the T cell's life cycle, in the lymph node.

By blocking CTLA4, epilimumab keeps the T cell primed and active.

It was a massive breakthrough for melanoma.

Then we have the PD -1 inhibitors, nivolumab and pembrolizumab.

These seem to be everywhere now.

They are.

PD -1 stands for programmed death protein 1.

It's a receptor on the T cell.

Normally, if a cell touches PD -1, the T cell shuts down or dies.

Cancer cells often coat themselves in the ligand, which is called PD -L1, to press that button.

So nivolumab covers up the PD -1 receptor so the cancer can't press it.

Exactly.

It's like putting a cover over the off switch.

The T cell remains active, recognizes the cancer, and kills it.

These drugs are now used in lung cancer, kidney cancer, Hodgkin lymphoma.

I mean, the Lyft grows every year.

But there is no free lunch in pharmacology.

If we take the brakes off the immune system to kill cancer, what is the logical fallout?

The immune system starts attacking you.

Autoimmunity.

Autoimmunity.

The adverse effects are all itis colitis, which is inflammation of the colon, pneumonitis in the lungs, thyroiditis, hepatitis.

It can look like Crohn's disease or rheumatoid arthritis.

So you are trading cancer for an autoimmune condition.

In a way, yes.

But autoimmune conditions are usually treatable with steroids.

Metastatic lung cancer wasn't.

It's a trade -off most patients are willing to make.

Let's switch gears from solid tumors to hematologic cancers.

The liquid tumors.

Leukemias and lymphomas.

The text introduces the concept of CD markers.

CD stands for Cluster of Differentiation.

Just think of them as IDM badges on the surface of white blood cells.

Every type of white blood cell wears a different badge.

And the most famous badge is CD20.

CD20 is worn by B cells.

And you have to remember, B cells are the source of non -Hodgkin lymphoma and CLL.

So we have the drug Rituximab, which we decoded earlier.

It binds to CD20.

And what happens when it binds?

It triggers complement -dependent cytotoxicity.

Basically, it punches holes in the B cell membrane and pops it.

It just wipes out the B cells.

The text also mentions Doritumumab for multiple myeloma.

Right.

So myeloma is a cancer of plasma cells.

Plasma cells don't wear CD20.

They wear CD38.

So Doritumumab targets CD38.

It's the same concept.

Find the badge, bind to it, and signal the immune system to eat the cell.

Now here is where it gets really, I don't know, video game style.

Antibody drug conjugates, or ADCs.

The text calls these smart bombs.

I love this technology.

So we discussed how antibodies are great at finding targets.

But sometimes, just binding isn't enough to kill the cell.

So scientists thought, what if we use the antibody as a delivery truck and strap a nuclear warhead to the back?

So you chemically link a chemotherapy poison to the antibody.

Exactly.

Look at Trastuzumab emtansine.

We know Trastuzumab finds the HER2 breast cancer cell.

Right.

Emtansine is a super potent microtubule inhibitor.

It stops cells from dividing.

But it's way too toxic to just inject into the blood.

It would kill the patient.

So you attach it to the Trastuzumab.

The antibody guides it directly to the cancer cell.

The cell swallows the antibody, a process called internalization.

Once inside, the chemical linker breaks, releasing the poison directly into the heart of the tumor cell.

Wow.

It spares the healthy cells that don't have the marker.

Another example is Ibrutumumab tucatan.

This one is even wilder.

It targets CD20 for lymphoma.

But the payload is yttrium -90.

That sounds radioactive.

It is.

It's a radioactive isotope.

It delivers radiation therapy.

But instead of beaming it through the skin and burning everything in its path, it delivers the radiation point blank to the surface of the cancer cell.

So it fries the tumor from the inside out.

That's a good way to put it, yes.

Incredible.

OK.

We have spent a lot of time on cancer.

But the critique we received from listeners, and rightly so, is that we often rush the non -cancer applications.

That's fair.

But chapter 46 makes it clear.

MABs are taking over all of medicine.

Hmm.

Let's do a proper deep dive into table 46 .2.

Let's do it.

Let's start with cholesterol.

The drug is evilacumab.

To understand this, we need to understand how the liver clears cholesterol.

OK, paint the picture.

Your liver cells have receptors on their surface called LDL receptors.

Think of them as catcher's mitts.

OK.

They reach into the blood, grab a passing LDL, the bad cholesterol particle, and pull it into the liver to be destroyed.

That is good.

We want lots of mitts.

Enter the protein PCSK9.

PCSK9 is a protein that naturally circulates in your blood.

Its job, unfortunately, is to bind to those catcher's mitts and degrade them.

It destroys the LDL receptors.

So PCSK9 reduces the liver's ability to clean the blood.

Exactly.

It's a regulatory feedback loop.

But in patients with high cholesterol, we don't want that regulation.

We want maximum cleaning power.

So evilacumab is an antibody that binds to PCSK9.

It handcuffs the shredder.

Right.

It inhibits PCSK9.

This means the LDL receptors, the mitts, are spared.

They stay on the surface of the liver.

The result is a dramatic increase in the liver's ability to pull LDL out of the blood.

I see.

We see massive drops in cholesterol levels, even in people where statin stopped working.

It's category.

Asthma.

The drug mentioned is omelizumab.

But again, let's start with the physiology.

What happens in an allergic asthma attack?

It starts with an allergen, say cat dander.

Your body makes an antibody called IgE specific to that dander.

These IgE antibodies go and sit on the surface of mast cells in your lungs.

They act like landmines.

So the mast cell is loaded with explosives like histamine, and the IgE is the trigger.

Perfect analogy.

When you breathe in the dander again, it lands on the IgE.

It cross -links them.

This pulls the pin.

The mast cell degranulates.

It explodes, releasing histamine, leukotrienes, and cytokines.

That causes the airway constriction and mucus production of asthma.

So how does omelizumab stop this?

It is an anti -IgE antibody.

It binds to the IgE while it is still floating in the blood before it can attach to the mast cell.

It disarms the landmine before it is planted.

If the IgE is bound by the drug, it cannot fit onto the mast cell receptor.

No trigger, no explosion, no asthma attack.

It is highly effective for severe allergic asthma.

The text also mentions mepilizumab for eosinophilic asthma.

That's a different pathway.

Eosinophils are white blood cells that cause inflammation in late -stage asthma.

Right.

They feed on a cytokine called interleukin -5, or IL -5.

Mepilizumab binds to IL -5 and neutralizes it.

It starves the eosinophils and their numbers drop.

Moving to migraine.

This is a relatively new class.

The CGRP antagonists.

This is fascinating physiology.

We used to think migraines were just about blood vessels dilating.

Now we know it's a neurological event involving the trigeminal nerve.

When that nerve is irritated, it releases a peptide called CGRT calcitonin gene -related peptide.

And CGRP transmits pain.

CGRP is a potent vasodilator and a pain signal transmitter.

It creates that throbbing, blinding pain.

The new drugs galcanizumab, erinumab, are antibodies.

Some bind to the CGRP molecule itself, just mopping it up.

And others?

Others, like erinumab, bind to the CGRP receptor to block it.

Either way, you're interrupting the pain signal.

And unlike tryptans, which you take during an attack, these are injected once a month to prevent the attacks from happening.

For chronic migraine sufferers, this is life -changing.

Let's talk autoimmune.

This is the blockbuster category containing Humira, a dolomumab.

This targets TNF -alpha, or tumor necrosis factor alpha.

In diseases like rheumatoid arthritis, Crohn's disease, and psoriasis, the immune system is hyperactive.

The master commander of this inflammation is TNF -alpha.

So drugs like a dolomumab and infliximab are simply soaking up that commander.

They bind to TNF -alpha and neutralize it.

It turns down the volume on the entire inflammatory response.

But again, safety check.

If you turn down the immune system, what is the risk?

Infection.

Specifically, the text warns about tuberculosis.

Beepy.

Right.

TNF -alpha is the key cytokine your body uses to keep latent TB walled off in the lungs.

If you block TNF -alpha, the TB can wake up and spread.

You must screen for TB before starting these drugs.

The text also lists some very specific interleukin inhibitors for psoriasis and eczema.

We are getting more precise than just blocking TNF.

For psoriasis, the silvery scales, the key drivers are IL -12, IL -23, and IL -17.

So we have drugs like eustachinomab, which blocks IL -12 and 23.

Okay.

And cecachinomab, which blocks IL -17.

And for eczema, or atopic dermatitis.

That is driven by IL -4 and IL -13.

The drug dupolumab blocks that specific pathway.

It clears up the itchy red skin without suppressing the entire immune system as heavily as steroids do.

Finally, osteoporosis.

Dinosumab.

This is a different mechanism entirely.

It connects to bone physiology.

Your bones are constantly being remodeled.

You have osteoblasts that build bone and osteoclasts that eat bone.

And in osteoporosis, the eaters are winning.

Correct.

The signal that tells osteoclasts to mature and start eating is a protein called r -a -n -k.

So dinosumab targets r -a -n -g.

It binds to r -a -n -g -p -e -l -o.

It mimics the body's natural stop signal, which is a protein called osteoporotorin.

By blocking r -a -n -k -l, the osteoclasts never activate.

Bone breakdown stops and bone density improves.

It is amazing.

We can map a specific protein to a specific disease and just turn it off.

Okay.

Let's zoom out to part six.

Biologicals vaccines.

You cannot talk about immunopharmacology without the original biologicals.

The text gives a great overview of the four main types of vaccines.

Let's run through them with examples because this helps clarify what is actually in the syringe.

Okay.

Type one.

Live attenuated.

This is the closest to the real thing.

It is a live virus that has been weakened or attenuated in the lab so it can't make you sick theoretically.

And examples would be?

MMR measles, mumps, rubella, and varicella for chickenpox.

Because it is live, it generates a massive lifelong immune response.

But you generally cannot give these to immunocompromised patients, like those on chemo we discussed, because the weak virus could still overwhelm them.

Right.

Type two.

Inactivated.

This is a killed virus.

It's dead.

It's safer, but the immune response is weaker so you often need boosters.

The polio shot and hepatitis A are examples.

Type three.

Subunit or recombinant.

Here, we don't even use the whole virus.

We just take a piece of it, a protein or a sugar, and inject that.

The hep B vaccine is a surface antigen.

The Pneumovax is just the sugar coating of the bacteria.

This is very safe.

Very safe, but again, often requires boosters.

Type four.

Toxoid.

This is for bacteria that hurt you by releasing a toxin like tetanus or diphtheria.

We aren't fighting the bacteria, we are fighting the poison.

So the vaccine is a deactivated version of the toxin.

It trains your body to neutralize the poison.

Let's look at the vaccination schedule highlights in tables 46 .3 and 46 .4.

What are the must -knows for the exams?

For infants.

Hepatitis B.

It is usually the very first vaccine given, often in the delivery room.

Why so early?

Is a baby really at risk for hep B?

It is all about the consequences.

If an infant contracts hep D, say, via vertical transmission for mom, their immature immune system can't clear it.

They have a 90 % chance of becoming chronic carriers, which can lead to liver cancer or failure by their 20s or 30s.

We vaccinate at birth to close that window immediately.

And for the elderly population, over 65.

Two big ones.

First, pneumococcal or pneumovax.

Pneumonia is a leading cause of death in seniors.

This vaccine covers 23 different serotypes of the bacteria.

And the second.

Shingles or herpes zoster.

This is the reactivation of the chicken pox virus.

Right.

The virus hides in your nerve roots for decades.

As your immunity wanes with age, it wakes up and causes a blistering, agonizing rash along a nerve dermatome.

And there is a distinction made between Shingrix and Zostavax.

Zostavax was the old live vaccine.

It was OK, but not great.

Shingrix is the new recombinant or subunit vaccine.

It is vastly superior, over 90 % effective.

So Shingrix is the one to know.

The text explicitly states Shingrix is now the preferred agent.

We have to touch on the COVID -19 section, as the text includes a snapshot of this technology.

It highlights the difference between the mRNA vaccines, like Pfizer and Moderna, and the adenovirus vector vaccines, like J &J and AstraZeneca.

Explain the mRNA mechanism using the printer analogy.

OK.

So mRNA is just an instruction strip.

The vaccine is a lipid bubble containing the instructions for the spike protein of the virus.

It enters your cell, your cell's ribosomes, which are like 3D printers.

They read the strip and print the spike protein.

So your body makes the viral part itself.

Exactly.

Then your cell displays that spike protein on its surface.

The immune system sees it, says that's alien, and builds antibodies against it.

The mRNA itself is degraded very quickly.

It never enters the nucleus or touches your DNA.

And the adenovirus vector.

Same goal, different delivery.

Instead of a lipid bubble, they use a hollowed out, harmless cold virus, an adenovirus, to carry the DNA instructions into the cell.

The cell turns the DNA to mRNA, prints the protein, and the process continues from there.

Part seven, preventing organ rejection.

This is the induction phase.

This is interesting because until now, we've been trying to boost the immune system or guide it.

Now we want to knock it out.

Exactly.

If you get a kidney transplant, that kidney is an allograft.

It's foreign tissue.

Your T cells will recognize it and try to kill it.

We have to stop that activation.

The heavyweights here are the calcinerin inhibitors, cyclosporine, and tacrolimus.

This mechanism is complex.

So walk us through the T cell activation pathway.

OK.

Visualize the inside of a T cell.

When the T cell recognizes the foreign kidney, calcium rushes inside the cell.

That calcium binds to calmodulin, which activates an enzyme called calcinerin.

What does calcinerin do?

Calcinerin removes a phosphate from a transcription factor called NFAT.

This allows NFE to march into the nucleus and turn on the gene for IL -2, interleukin -2.

And IL -2 is the GO signal.

IL -2 is the proliferation signal.

It tells the T cell to clone itself into an army.

So cyclosporine and tacrolimus enter the cell and block calcinerin.

No calcinerin means NFA stays in the lobby.

No message goes to the nucleus.

No IL -2 is made.

No army is formed.

And the kidney is safe.

That is the pathway.

But calcinerin is found in other cells too, specifically in the kidney itself.

So the major irony of these drugs is that they are nephrotoxic.

The drug you give to save the kidney transplant can actually damage the kidney.

If the dose is too high, yes.

It's a very fine line.

The text also warns about a specific drug food interaction with cyclosporine.

CYP3A4.

Cyclosporine is metabolized by this liver enzyme.

Grapefruit juice contains chemicals that inhibit CYP3A4.

So if you drink grapefruit juice, you stop breaking down the drug.

The levels in the blood skyrocket to toxic ranges, destroying your kidneys.

Transplant patients are strictly forbidding from consuming grapefruit.

There is another class called MTOR inhibitors, serolimus, also known as rapamycin.

This works slightly later in the chain.

Even if some IL -2 is made, serolimus blocks the signal that IL -2 sends.

It inhibits MTOR, which stands for mammalian target of rapamycin, and that stops the cell cycle.

The text mentions a non -transplant use for serolimus that is really common.

Drug eluding stents.

When a cardiologist puts a metal stent in a coronary artery, scar tissue tries to grow over it.

Right.

By coating the stent in serolimus, we stop that local cell growth and keep the artery open.

Finally, the anti -proliferative agents.

Mycophenolate.

This relies on a metabolic quirk of T cells.

Most cells in your body can scavenge parts to make DNA.

That's the salvage pathway.

But T cells are picky.

They need to make their guanine nucleotides from scratch.

The de novo pathway.

And mycophenolate blocks that de novo synthesis.

Yes.

So it effectively starves the T cells of the building blocks for DNA replication, while the rest of the body cells use the salvage pathway and are fine.

It's a targeted starvation.

We have arrived at the final frontier, part eight, gene therapy.

This section feels like the year 3000.

It does.

We are moving beyond drugs.

We are editing the source code of life.

First up, mRNA targeting, or anti -sensile ligonucleotides.

Think of this as jamming the printer.

Sometimes a disease is caused because you are making a bad protein.

Mipomersyn is used for a rare genetic high cholesterol.

It is a synthetic strand of DNA that is complementary to the mRNA for ApoB, the bad protein.

It sticks to the mRNA.

It sticks like Velcro.

The ribosome cannot read the mRNA because it's double stranded now.

Enzymes come by and destroy it.

No protein is made.

Then there is Nusnersyn spinraza for spinal muscular atrophy, SMA.

SMA is a devastating disease where motor neurons die.

Nusnersyn modifies the splicing of the mRNA to produce a functional survival protein.

It is injected directly into the spinal canal.

It halts a disease that used to be fatal in infancy.

But even wilder than blocking mRNA is CAR -RT therapy, Tysogen Leclusyl.

This is cellular gene therapy.

We take the patient's blood and filter out their T cells.

We send those T cells to a lab.

And what happens in the lab?

We use a viral vector to insert a new gene into the T cells.

This gene builds a chimeric antigen receptor, or CRR, on the surface that targets CD19, which is found on leukemia cells.

So you are upgrading the T cells with a homing beacon.

We are.

We grow millions of them and infuse them back into the patient.

These Robocop T cells hunt down the leukemia and wipe it out.

It is a potential cure for refractory acute lymphoblastic leukemia.

And lastly, gene replacement using AAV vectors.

This is for when a gene is missing entirely.

Vordegene, or Luxterna.

This is for a specific type of genetic blindness where the RPE65 gene is broken.

We use an adeno -associated virus, or AAV, to carry a working copy of the gene.

You inject the virus into the eye.

Yes.

The virus infects the retinal cells, drops off the good gene, and the cells start making the protein required for vision.

It literally restores sight.

And Zolgensma for SMA.

Same concept.

It delivers a working SMN1 gene to the motor neurons of a baby.

A single 5E infusion can save the child's life and allow them to walk.

It is the most expensive drug in the world, but it fixes the root cause.

It's truly mind -blowing.

We've gone from mouse antibodies causing allergic reactions to genetically modified viruses restoring sight.

It is the most rapidly evolving field in medicine.

The pharmacology of Chapter 46 is not static.

It changes every month.

So for the students sweating over their notes, let's wrap this up with a synthesis.

What are the key takeaways from this deep dive?

OK, number one, decode the name.

Use the suffixes.

TaxMab is antibody.

Tax is chimeric.

Two is tumor.

That gives you the answer.

Number two, know the targets.

EGFR blockers like cetuximab stop the growth signal, but watch for the rise mutation.

HER2 blockers like Trastizumab save breast cancer patients, but watch the heart.

Right.

Three, checkpoints.

PD1 and CTLA -4 inhibitors don't kill cancer directly.

They take the breaks off the immune system.

And the cost is autoimmunity.

Four, rejection.

It's all about IL -2.

Calcinerian inhibitors like cyclosporine stop IL -2 production.

And finally, five, safety.

These are proteins, 5E only.

Watch for hypersensitivity.

That is your roadmap for Chapter 46.

It's a dense chapter, but remember, these are the tools that are actually curing the incurable.

It is worth the effort to learn them.

Thank you for listening to this last -minute lecture.

Good luck with your studies.

Go crush that exam.

And we will see you on the next deep dive.