Molecular targting drug design and development

What is the primary mechanism of action for traditional chemotherapy drugs like alkylating agents and microtubule inhibitors?

They selectively kill cells during the process of cell division.

Why do traditional chemotherapy treatments often exhibit a very small therapeutic window?

They target all rapidly dividing cells in the body, including healthy tissues like bone marrow and the gastrointestinal tract.

Which specific protein is often referred to as the 'guardian of the genome' due to its role in detecting genetic stress and triggering apoptosis?

P53

What is the biological consequence of a cell losing functional P53 activity?

The cell can survive highly stressed conditions and introduce additional mutations without undergoing apoptosis.

In which type of cancer are RAF inhibitors most commonly used as a targeted therapy?

Melanoma

What is a major clinical challenge associated with the use of first-generation RAF inhibitors?

The rapid emergence of secondary resistance, often leading to cancer recurrence within six months.

How do tumors typically utilise the PD-1/PD-L1 pathway to survive?

They express PD-L1 to suppress the host's T-cell immune response against the tumor.

Why has KRAS historically been considered an 'undruggable' target in cancer drug discovery?

It binds GTP extremely tightly, making it difficult for inhibitors to compete with the natural ligand.

The enzymatic activity of RAS proteins acts as an 'off switch' by hydrolysing GTP into _____.

GDP

Which specific KRAS mutation was successfully targeted by the first approved direct RAS inhibitor, sotorasib?

G12C

what is a PROTAC

Proteolysis Targeting Chimera; a bifunctional molecule that recruits an E3 ligase to a protein of interest to trigger its degradation.

What are the three essential structural components of a PROTAC molecule?

• A ligand for an E3 ligase

• a chemical linker

• a ligand for the protein of interest.

In the context of PROTACs, what is the role of the E3 ligase?

It conjugates ubiquitin molecules onto the target protein, marking it for destruction by the proteasome.

How does 'event-driven' pharmacology in PROTACs differ from 'occupancy-driven' pharmacology in traditional inhibitors?

PROTACs act catalytically to degrade multiple target molecules, whereas inhibitors require constant binding to maintain their effect.

What is the main physical disadvantage of PROTACs compared to traditional small-molecule drugs?

They have a high molecular weight (often near 1000 Da), which limits their oral permeability and solubility.

what is an Antibody-Drug Conjugate (ADC)

A therapeutic agent consisting of a monoclonal antibody linked to a cytotoxic payload for targeted delivery to tumor cells.

Following surface antigen binding, what is the next step in the cellular mechanism of an ADC?

Internalisation into the cell via endosomes and lysosomes.

Why might an ADC cause non-specific toxicity even if its antibody is highly selective for a tumor antigen?

Premature release of the cytotoxic payload in the plasma or antibody recycling in the liver.

Which advanced ADC was developed to be effective in breast cancer patients with low levels of HER2 expression?

Trastuzumab deruxtecan (Enhertu)

Which receptor-ligand pair is being researched to target leukaemic monocytes in Chronic Myelomonocytic Leukaemia (CMML)?

CCR2 and CCL2

What is the metabolic consequence of inhibiting the enzyme NAMPT in cancer cells?

Depletion of NAD levels, leading to mitochondrial failure and a lack of ATP.

Why are NAMPT inhibitors particularly useful as payloads for targeting non-dividing tumor cells?

Their cytotoxic effect is cell-cycle independent, relying on metabolic depletion rather than interrupting division.

How does molecular radiotherapy (peptide radio conjugates) differ from systemic beam radiotherapy?

It delivers radionuclides specifically to metastatic sites throughout the body via targeted ligands like peptides.

Which antigen is the primary target for radioligand therapy in advanced prostate cancer?

Prostate-Specific Membrane Antigen (PSMA)

What is a significant logistical hurdle in the clinical use of peptide radio conjugates?

The short half-life of the radionuclides requires a rapid supply chain from manufacture to patient administration.

Compared to ADCs, what is a key advantage of Peptide Drug Conjugates (PDCs)?

They have a smaller size, which can lead to improved tissue and tumor penetration.

Why is the bone marrow often a difficult site for conventional ADCs to reach effectively?

Large antibodies often have poor penetration into certain tissues like the bone marrow compared to smaller peptides.

What happens to a protein once it has been 'poly-ubiquitinated' by the cell's internal machinery?

It is funneled into the proteasome for degradation and removal.

How do antibody-degrader conjugates attempt to improve upon the limitations of standard PROTACs?

They utilise the antibody's long half-life and selectivity to deliver the PROTAC payload specifically to tumor cells.

Which E3 ligase is involved in the cell's natural response to hypoxia and is frequently hijacked by PROTACs?

VHL (Von Hippel-Lindau)

What is the primary function of the chemical 'linker' in an Antibody-Drug Conjugate?

To maintain stability in circulation while allowing for controlled release of the toxin inside the tumor cell.

The use of siRNA and CRISPR-Cas9 in early drug discovery primarily helps researchers to _____.

Identify and validate which genes are essential for cancer cell survival.

Why is hormonal therapy for breast cancer (like targeting estrogen signaling) limited in its application?

It is only effective for tumors that remain under the control of natural hormonal signaling processes.

What property of BRAF V600E mutations makes them vulnerable to targeted inhibition?

The mutation causes the protein to become constitutively active, signaling for cell division without upstream stimulation.

In therapeutic terms, what is the primary purpose of an alpha-particle-emitting radionuclide in a radio conjugate?

To cause direct DNA damage and generate reactive oxygen species to destroy the cancer cell.

How does the 'bystander effect' (implied in ADC literature) potentially allow ADCs to kill nearby cancer cells that lack the target antigen?

The released cytotoxic payload can diffuse out of the original target cell into the surrounding tumor microenvironment.

Why do cancer cells with defective DNA damage response pathways show specific vulnerability to certain inhibitors?

They cannot repair the additional DNA stress caused by the drug, leading to selective cell death.

What is the major challenge of using LNPs to deliver genetic material to solid tumors compared to their use in vaccines?

Tumors have poor vascularisation and complex biological barriers that impede LNP uptake.

Which E3 ligase recruiter, derived from thalidomide, is used in the most clinically advanced PROTACs?

CRBN (Cereblon)

Which protein acts as the downstream effector of RAS in the signaling pathway that drives proliferation in melanoma?

RAF

What complex process allows CAR-T cell therapy to be considered 'personalised' medicine?

T-cells are removed from a patient, genetically engineered to recognise their specific tumor, and then re-infused.

In terms of drug potency, why do peptide drug conjugates often require more potent payloads than ADCs?

The smaller delivery vehicle usually supports a lower Drug-to-Antibody (or Peptide) Ratio (DAR).

What clinical outcome was observed in the first phase 3 readout of an estrogen receptor PROTAC for breast cancer?

It successfully degraded the receptor and improved patient outcomes, but simple oral degraders proved equally effective.