Biomolecular Therapeutics

Question 1

Give some examples of biological therapeutics.

Answer 1

• Vaccines.
• Antibodies (part of the immune system).
• Proteins (cytokines, interleukins, colony-stimulating factors).
• Oligoinucleotides (antisense, gene therapy).

Question 2

What is angiostatin?

Answer 2

This is an internal fragment of plasminogen approximately 38kDa. It inhibits endothelial cell proliferation.

Question 3

Describe the tolerability and efficacy of angiostatin.

Answer 3

It is well tolerated by patients and has high efficacy.

Question 4

Angiostatin is currently in phase 3 clinical trials. Why might it not have much use in the clinic?

Answer 4

It may not have much use in the clinic because of its instability.

Question 5

What is endostatin?

Answer 5

This is a 20kDa fragment of the c-terminus of collagen XVII. It works by blocking mitogen activated protein kinase (MAPK) in endothelial cell proliferation.

Question 6

How much more potent than angiostatin is endostatin?

Answer 6

30x.

Question 7

What does endostatin have potential use in?

Answer 7

Endostatin has potential uses in patients with sarcoma, melanoma, and neuroendocrine tumours.

Question 8

Why might endostatin not have much use in the clinic?

Answer 8

It may not have much use in the clinic based on its instability.

Question 9

How does avastin (bevacizumab) work?

Answer 9

Avastin is an anti-VEGF monoclonal antibody which works by sequestering VEGF, preventing receptor activation. Because it is an antibody it binds very tightly and specifically to VEGF.

Question 10

What is avastin (bevacizumab) used to treat?

Answer 10

It is licensed for the treatment of colorectal, lung, breast (outside the USA), glioblastoma (USA only), kidney, and ovarian cancers.

Question 11

What are the side effects of avastin (bevacizumab)?

Answer 11

• Heightened bleeding risk.
• Hypertension.
• Exacerbation of CAD.
• Artery diseases.

Question 12

What is immunotherapy?

Answer 12

These are therapies which exploit one’s own immune system for therapeutic benefit.

Question 13

Give some examples of immunotherapy.

Answer 13

• Vaccination.
• Therapeutic antibodies/targeting of therapies.
• Activation of the immune system (NK, LAK, CTL, DC).
• Bone marrow transplantation.

Question 14

What are prophylactic vaccines, with respect to cancer treatment?

Answer 14

Prophylactic vaccines for cancer are often vaccines that build immunity to viral infections which have been linked to certain cancers. There are also vaccines to bacteria that may be linked to cancer.

Question 15

Give examples of infections which have vaccines against them and that are linked to cancer.

Answer 15

• HPV (viral).
• HepB (viral).
• Helicobacter pylori (bacterial).

Question 16

Why do viruses have the potential to induce cancer?

Answer 16

Viruses have the potential to induce cancer through their method of reproduction. Because viruses reproduce by inserting their genes into the cellular machinery of a host cell, hijacking this machinery to produce more viruses. This can lead to the induction of oncogenes, leading to cancer.

Question 17

What do therapeutic vaccines for cancer require?

Answer 17

Therapeutic vaccines for cancer require the identification of cancer specific immunogenic proteins. These proteins should preferably be on the cell surface to aid targeting; they are usually unique to one cancer.

Question 18

What is the main downside of requiring specific immunogenic proteins for therapeutic cancer vaccines?

Answer 18

Because they are unique, they are expensive and can’t be used for multiple different cancers.

Question 19

When making therapeutic cancer vaccines, the difficulty is to find tumor specific antigens rather than tumour associated antigens. What are tumour associated antigens?

Answer 19

Antigens associated with changes that the tumour induces.

Question 20

Give some examples of tumour associated antigens?

Answer 20

• EBV.
• HPV.
• Glycoproteins.
• Glycolipids.
• α-fetoprotein.

Question 21

Explain the idea of vaccines based on cells.

Answer 21

This is the idea of modifying normal cells to be active against a certain cancer.

Question 22

How are vaccines based on cells made? How do they work?

Answer 22

In this therapy immune cells are taken from the patient, stimulated to identify the cancer, and then put back into the patient for therapeutic effect.

Question 23

Are unwanted immune responses likely with vaccines derived from cells? Why?

Answer 23

They are the patient’s own cells so an unwanted immune response (e.g. anaphylaxis) is very unlikely.

Question 24

Explain how classical anticancer therapies are much less targeted than vaccines based on cells.

Answer 24

Classical anticancer therapies are much less targeted. For example, alkylating agents which target DNA will target the DNA of all cells which contain DNA (all cells bar erythrocytes); this leads to damage being done to all these cells. Furthermore, this leads to the side effects seen when these agents are used.

Question 25

Give an example of a vaccine based on cells; including its use and how it is made.

Answer 25

An example of this is the ‘Provenge’ (Sipulecel-T, APC0815) therapy which is used for hormone refractory metastatic prostate cancer. The patient’s antigen presenting cells (DCs) are extracted and activated (with prostatic acid phosphate found on a very high proportion of prostate cancer cells) and granulocyte-macrophage colony stimulating factor then returned to the patient.

Question 26

Into what two mail classes do therapeutic antibodies fall?

Answer 26

• Antibodies that reply on the host immune system (naked).

* Antibodies conjugated to an anticancer agent (drug, radioactivity, or toxin).

Question 27

How are therapeutic antibodies made?

Answer 27

Antibodies are raised to proteins that are uniquely present on the surface of cancer cells, for example CD-52 in leukaemia. They are usually produced from mice and then humanised to ‘hide’ the change made from the immune system – reducing the likelihood of adverse immune reactions.

Question 28

What was the first mAb used for cancer?

Answer 28

The first mAb used for cancer was Rituximab (1997) which was raised for CD20 in non-Hodgkin’s lymphoma.

Question 29

In what two ways can naked antibodies act?

Answer 29

• Binding to cell proteins and activating the host immune response, resulting in killing the cell. Recruitment of immune factors.
• Prevent ligand binding to, or activation of, cell surface receptor to modulate cellular signalling.

Question 30

Give examples of naked antibodies that recruit immune factors.

Answer 30

o	Alemutzamab (CD52 in CLL).
o	Rituximab (CD33, NHL).

Question 31

Give examples of naked antibodies that prevent ligand binding or receptor activation.

Answer 31

o	Cetuximab (EGFR) prevent ligand binding.
o	Bevacizumab (Avastin) (VEGF-A) prevents activation.

Question 32

What are conjugated antibodies?

Answer 32

Conjugated antibodies (ADCs (Antibody-Drug Conjugates)) carry a toxic cargo to the cell.

Question 33

What may conjugated antibodies carry?

Answer 33

• Radioisotopes (radioimmunotherapy) e.g. ibrituomab tiuxetan (90Y).
• Enzyme prodrug therapy (ADEPT and others).
• Immunoconstructs – targeted drugs (Brentuximab vedotin – CD30/MauristatinE).
• Immunoliposomes.

Question 34

How can conjugated antibodies help to reduce toxicity?

Answer 34

These conjugated antibodies can help to reduce the toxicity of a drug as the drug is tethered to the antibody so can’t go off to bind to or act at other receptors.

Question 35

What is the main downside to conjugated antibody technology?

Answer 35

This cargo needs to be released at the site of action and this can be hard.

Question 36

What is ADEPT therapy?

Answer 36

ADEPT stands for antibody direct enzyme prodrug therapy. This is where an enzyme is conjugated to the antibody and this conjugate is administered with a prodrug. The enzyme is taken to the desired site of action and here it metabolises the prodrug into active drug, then it has its effect.

Question 37

What is the benefit of ADEPT therapy?

Answer 37

The benefits of this is that the prodrug has little toxicity and adverse effects. The active drug only works at the desired site of action, further reducing the likelihood of adverse effects.

Question 38

Explain the use of growth factors in cancer therapy.

Answer 38

These include colony stimulating factors (e.g. granulocyte colony stimulating factor, G-CSF) and they are often used to combat side effects of other therapies.
Examples include:
•	Bone marrow (Lenogastrim, Filgrastim).
•	Erythrocytes (erythropoietin).
•	Platelets (interleukin 11).

Question 39

Give examples of growth interleukins and interferons used in cancer treatment.

Answer 39

• IL-2 – growth and activity of immune cells (e.g. lymphocytes).
o Melanoma, kidney.
• INFα – stimulate immune system and slow cancer growth.

Question 40

Explain how viral therapies can be used to combat cancer.

Answer 40

With this technology, a virus is raised that is selective for cancer cells; this can be via invasion or a virus that only replicated in cancer cells. One should choose a virus that causes lysis (adenovirus, vaccinia, herpes). It may also be possible to produce viruses to produce anticancer proteins (e.g. GM-CSF).