Theraputics Exam 1

IND Enabling Studies I - Pharmacology and ADME/PK

What is the main goal of the Lead Optimization stage in drug discovery?

To systematically modify the chemical structure of an initial lead compound to optimize its potency, selectivity, safety, and ADME/PK profile into a candidate suitable for human clinical trials.

What physical and biological properties are typically improved during lead optimization?

Target potency, target selectivity, solubility, metabolic stability, tissue permeability, bioavailability, and overall safety/toxicity.

IND-Enabling Studies

The mandatory preclinical package of testing (pharmacology, PK/ADME, toxicology, and manufacturing quality) required to file an IND application with the FDA.

NOAEL (No-Observed-Adverse-Effect-Level):

The highest dose of a drug tested in animals that produces no significant toxic or harmful side effects. This value determines safe starting doses for human clinical trials.

Genotoxicity

The ability of a chemical substance to damage genetic material (DNA) inside cells, potentially causing mutations or cancer.

CMC (Chemistry, Manufacturing, and Controls):

The regulatory section proving that the drug's manufacturing process consistently yields a pure, stable, and high-quality product.

What is the primary purpose of conducting IND-enabling studies during drug development?

To gather sufficient safety, pharmacological, and manufacturing data to prove to regulatory agencies (like the FDA) that a drug candidate is reasonably safe for initial testing in human clinical trials.

Which three vital body systems are evaluated in Safety Pharmacology studies?

The Cardiovascular system (heart/blood vessels), Central Nervous System (brain/CNS), and Respiratory system (lungs).

What is the focus of Chemistry, Manufacturing, and Controls (CMC) in an IND submission?

Ensuring the drug candidate can be manufactured with consistent purity, quality, stability, and batch-to-batch reproducibility.

Pharmacology Studies Focuses on what?

Determining how well a drug candidate hits its intended biological target and checking for any unintended off target interactions

Before giving a drug candidate to humans, scientists run pharmacology tests to make sure the chemical actually does what it was designed to do (primary effects) and check whether it accidentally messes with other parts of the body (secondary effects).

Explain Primary Pharmacodynamic and what Key factors are evaluated?

Evaluates desired, main medical effects of the drug candidate acting through its specific intended target. so it answers does this drug actually do what we want it to do?

Key factors evaluated: Target binding, enzyme/receptor inhibition, full mech of action, and target engagement

Explain secondary pharmacodynamics and what it evaluates?

Evaluates any drug activity occurring outside of the intended target. So it answers what unintended things does the drug do that were unanticipated?

Key focus: Identifying off-target effects to catch potential side effects early.

What is the primary difference between Primary Pharmacodynamics and Secondary Pharmacodynamics?

Primary pharmacodynamics measures desired therapeutic effects on the intended target, while secondary pharmacodynamics measures off-target effects on non-intended targets.

Why are cell culture experiments categorized as in vitro rather than in vivo?

Because the cells are grown and tested outside of a whole living organism within an artificial, controlled lab environment (like culture flasks or plates).

What animal species are commonly used to perform in vivo pharmacology studies?

Rats, mice, rabbits, and dogs.

What tests do In vitro assays- Biochemical show for drugs?

Biochemical assays tests how a drug candidate interacts with an isolated pure proiein or enzyme in a simple artificial lab environment without whole cells present

What questions should Biochemical Assays answer?

They should answer : does the drug actually grab onto the target protein (binding assays); does it stop or slow down the target enzymes activity(enzyme assyas)

What is the fundamental difference between a biochemical assay and a cell-based assay?

Biochemical assays test drugs against isolated targets in an artificial environment (no cells present), whereas cell-based assays test drugs inside intact living cells.

In virtro assay - biochemical :

What are the two primary types of biochemical assays, and what question does each answer?

Binding assays (Does the compound bind to the target?) and 2) Enzyme assays (Does the compound inhibit enzyme activity?).

In virtro assay - biochemical :

What critical quantitative measurements are first determined using biochemical assays in early drug discovery?

Target potency, binding affinity, and target selectivity.

In virtro assay - biochemical :

How are biochemical assay experiments typically designed to measure drug potency?

By testing multiple concentrations of the drug candidate against the isolated target and graphing the results to calculate exact potency values.

In virtro assay - biochemical :

How can binding assay be measured?

Using dissociation constant Kd, which predicts how strongly a drug candidate (ligand) binds to its target

In virtro assay - biochemical :

What does Kd represent?

represents the exact drug concentration required to occupy half (50%) of all available binding sites on that target. Because Kd measures how easily a drug falls off or stay unattached, a smaller Kd = stronger binding affinity; larger Kd = weaker binding affinity

In virtro assay - biochemical :

If Compound A has a Kd of 10nm and Compound B has a Kd of 500nm, which compound has a higher binding affinity for the target?

Compound A, because a lower Kd indicates a stronger binding affinity.

In virtro assay - biochemical :

On a receptor occupancy vs. drug concentration graph, how do you visually find the $K_d$ value?

Find $50\%$ on the Y-axis (receptor occupancy), trace horizontally to the curve, and read the corresponding drug concentration on the X-axis.

In virtro assay - biochemical :

What does an enzyme assay use and to measure what?

Uses IC50 (inhibitory Concentration) to measure how well a lead compound blocks or stops the biological activity of a target enzyme.

How is IC50 measured?

In virtro assay - biochemical :

When developing a drug to block a harmful enzyme, scientists measure how much of the drug is needed to cut that enzyme's activity in half (50%). IC50 measures the amount of drug needed to slow the enzyme so

smaller IC50 value = potent/active = very little dose required to achieve 50% inhibition

larger IC50 value = less active = more dose required to achieve 50% inhibiton

In virtro assay - biochemical :

Is a drug candidate with an $\text{IC}_{50}$ of $5\text{ nM}$ more active or less active than a drug candidate with an $\text{IC}_{50}$ of $5\mu\text{M}$?

It is more active, because a lower $\text{IC}_{50}$ value means a much smaller concentration is needed to achieve $50\%$ inhibition

In virtro assay - biochemical :

Is the $\text{IC}_{50}$ metric used exclusively for enzyme assays?

No, $\text{IC}_{50}$ is used across many different biological assays to measure general target inhibition.

In Vitro Assays - Cellular

How do cell-based assays evaluate a drug?

Evaluate how a drug candidate work inside intact living cells, providing a realistic ‘natural’ environment to test its biological performance

How does the cellular assays help biological assay?

This stage confirms that the biological effect seen in the lab dish directly matches the action of the drug on its target inside a real cellular environment.

What are some key consideration and goals breakdown?

• Membrane Permeability: Checks if the drug molecule can physically diffuse through outer and inner cell membranes to reach its target.

• Intracellular Stability: Tests whether the compound remains stable enough inside the cell to bind its target before cell processes break it down.

• Multi-Target / Off-Target Checks: Determines whether the compound interacts with multiple unintended targets inside a complex cell.

• Target Engagement: Proves that the drug physically binds to its intended target inside the cell and confirms that the cellular changes (biological/phenotypic effects) are caused specifically by hitting that target.

• Initial Selectivity: Assesses whether the drug candidate prefers its target over other proteins present within a living cell environment.

Why are cell-based assays performed after initial biochemical assays in drug discovery?

Because cell-based assays evaluate whether the drug can cross cell membranes, stay stable, and engage its target inside a complex, natural cellular environment.

What is Target Engagement in the context of cellular assays?

It is proof that a drug candidate physically binds to its intended target inside the cell and that the observed biological/phenotypic effects are directly caused by this interaction.

What primary barrier must a drug candidate overcome to reach an intracellular target during a cell-based assay?

It must be able to diffuse through the cell's lipid membrane(s).

Biochemical assays account for cell membrane permeability and intracellular drug stability.

False; cell-based assays are required to evaluate membrane permeability and intracellular stability because biochemical assays only use isolated targets in test tubes.

What more does target engagement do?

Finding a drug candidate that binds a protein in a clean test tube is only step one. Target engagement tests if the drug can still find, grab, and alter that target inside a complex, crowded living cell. It proves that the physical or biological changes seen in the cell (phenotypic effects) are genuinely caused by the drug locking onto its intended target, rather than by random off-target side effects.

Why is target engagement tested in cell-based assays rather than just biochemical assays?

Because target engagement must prove the drug candidate can enter a living cell and physically bind its target in a complex, real-world cellular environment.

What critical link does target engagement provide between PK (Pharmacokinetics) and PD (Pharmacodynamics)?

• It directly links drug dose/concentration to target occupancy and resulting biological/phenotypic effects.

What does target engagement confirm regarding a drug's phenotypic effects on a cell?

It proves that the observed cellular changes are caused specifically by the drug binding its intended target, rather than by random off-target toxicity.

Target engagement studies can help identify whether a drug candidate has off-target interactions inside cells.

True; target engagement provides essential information about drug selectivity and on-target vs. off-target binding.

What is an example of Target Engagement Assays?

CESTA: cellular thermal stability assay which is the original engagement assay

• Proteins are stabilized to heat-induced
  degradation if they are bound to a small
  molecule

• Analyze melting temperature of target
  protein from cells treated with or without
  compound

Late-Stage Development - Clinical Trails, Patents, and the Approval Process

What three major topics make up late-stage drug development?

Clinical trials, patents, and the FDA approval process.

When does late-stage development occur in the drug discovery timeline?

After early-stage discovery and animal (preclinical) testing are completed.

What is the primary question answered during Phase I clinical trials?

Is the drug safe in humans?

What do generic drugs have to prove to get FDA approval without repeating Phase I–III trials?

Bioequivalence to the original brand-name drug

Which clinical trial phase takes place after the drug is officially approved and on the market?

Phase IV (Post-marketing surveillance).

What dose size is given to participants in a Phase 0 clinical trial?

A sub-therapeutic dose (microdose).

How many participants typically take part in a Phase 0 trial?

Fewer than 10 patients ($n < 10$)

Why would a drug company perform a Phase 0 trial?

To de-risk inconclusive animal data or choose the best candidate molecule before starting Phase I.

Who are the typical participants in a standard Phase I trial?

Healthy human volunteers.

What is the Maximum Tolerable Dose (MTD)?

The highest drug dose associated with acceptable toxicity levels.

What does RP2D stand for, and how is it chosen?

Recommended Phase 2 Dose; it is chosen based on Phase I safety data to use in Phase II trials.

NOAEL (No Observed Adverse Effect Level):

The highest dose tested in animal studies that produces no toxic side effects.

HED (Human Equivalent Dose):

An animal dose converted mathematically to match human body size and surface area.

MRSD (Maximum Recommended Starting Dose)

The safe starting dose calculated for the very first human trial.

How many volunteers are typically tested in Phase 1b trials?

20 to 200 volunteers

What animal metric is used as the starting point to calculate safe human starting doses?

NOAEL (No Observed Adverse Effect Level)

What does MRSD stand for in First-in-Human clinical trials?

Maximum Recommended Starting Dose.

What is the primary goal of Phase II clinical trials?

To determine if the drug is effective in treating the target disease, assess short-term safety, and identify dosing regimens.

Who participates in Phase II trials compared to Phase I trials?

Actual sick patients participate in Phase II, while healthy volunteers participate in Phase I.

What do control group patients receive in Phase II trials if a placebo is unethical?

The standard of care (current market-standard treatment)

Approximately how many patients are enrolled in Phase III clinical trials?

Back: Up to ~2,000 patients

Back: Up to ~2,000 patients

Why are Phase III trials conducted over long periods (~3 years) in diverse populations?

To detect rare side effects and prove the drug is safe and effective across different races, genders, and ages.

Where must Phase III trial sites be located if a company wants to market its drug internationally?

In international trial locations.

When do Phase IV clinical trials take place?

Post-approval, after the drug is available on the consumer market.

What is another term for Phase IV clinical trials?

Post-Marketing Surveillance Trials.

What is the primary purpose of Phase IV trials?

To monitor real-world long-term safety, rare side effects, and drug interactions across the general public.

Randomized Controlled Trial (RCT):

Patients are randomly split into treatment or control groups.

Parallel

Group A gets the new drug while Group B gets placebo/standard treatment at the exact same time

Crossover

Group A gets the drug first, then switches to placebo. Group B gets placebo first, then switches to the drug. Everyone receives both, just at different times.

Randomized Withdrawal

Everyone starts on the drug. Mid-way, half are randomly switched to a placebo to see if their disease comes back.

Factorial Design

Testing combinations of multiple drugs or different doses at the exact same time.

Adaptive Design:

A flexible setup where researchers can change rules mid-trial (like adding more patients or changing doses) based on early incoming data.

What are considered endpoints?

Primary (main therapeutic effect goal)

Secondary (analyzed after trial)

Surrogate (biological endpoint correlated to clinical outcome)

Composite (multiple endpoints)

How long does the FDA have to decide whether to file an NDA after receiving it?

60 days

What does the FDA evaluate during the facility inspection step?

The manufacturing facilities where the drug will be produced to ensure proper quality controls.

What two outcomes can occur at Step 12 (FDA Decision)?

Approval or issuance of a response letter (rejection/request for more data).

What percentage of submitted NDAs receive a "Refuse-to-File" decision during initial filing review?

10-12%

What is a Complete Response Letter (CRL)?

An official FDA response indicating an NDA cannot be approved in its current form.

How long does a drug company typically spend preparing an NDA post-Phase III trials?

6-12 mnths

How long does the standard FDA approval take?

around 2 years

Why did the FDA create fast track programs?ex: Accelerated approval

For drugs treating serious disease

What type of endpoint is used to grant FDA Accelerated Approval?

A surrogate endpoint

What must a company do after receiving Accelerated Approval?

Conduct required post-approval clinical trials to confirm the drug's actual clinical benefit.

What can happen if post-approval confirmatory trials fail to prove clinical benefit?

The FDA can withdraw the drug from the market

What factors are considered for expedited process?

• drugs being developed to treat a serious disease and has been showing promise in early trials

• Conditon approval before end of preplanned clincal trials if promising result shows

• Surrogate Endpoint : a result midway of trials that can predict overall efficacy

• Drugs enter this pathway during clincal trials

Explain conditions for Fast Track Designation?

Treats serious conditions + adresses unmet medical need (no treatments like this one or this one is just so much better)

Can enter before or during clinical trails

Explain conditions for Breakthrough Therapy

Treats serious conditions + human data proves substantial improvement over current treatments

like if it reduced number of deaths or sever symptoms

What data is required for Breakthrough Therapy designation that is not strictly required for Fast Track?

Preliminary human clinical data showing substantial improvement.

What does "unmet medical need" mean in Fast Track eligibility?

A disease with no approved treatment, or a drug that provides significant advantages over existing therapies.

When can a company apply for Fast Track designation?

Before or during clinical trials.

Priority Review (Expedited Approvals III)

Priority Review: drugs that completed clinical trails + significant improvement in safety/effectiveness over current therapy

• Shortens review timeline

• Guarantees FDA review in 6 months (vs 10)

Regenerative Medicine Advanced Therapy (RMAT)

drugs for serious condition + initial clinical data suggesting substantial improvement over the existing ones

• similar to breakthrough

• but specific to regenerative therapies like cell or gene therapies (not small molecules)

Why might a drug that passed Phase I–III trials safely still get pulled from the market post-approval?

Real-world use in millions of patients over long periods exposes rare toxicities or chronic side effects missed in trials.

Who can initiate a market drug withdrawal?

Either the FDA or the drug manufacturer.

What manufacturing issue can trigger a drug recall?

Unintended toxic impurities or quality failures during large-scale manufacturing.

Why are drugs withdrawed?

from prolonged use, toxisites or side effects can occur that are dangerous and maybe even its imapcting a specific population that was not detected in the trails.