Targeting TNF and Co-stimulation

Question 1

What is Tumour necrosis factor?

Answer 1

• Important pro-inflammatory cytokines
• Low concentrations activate host defense
• High concentrations cause organ damage
• Released as trimers of 17 kDa monomers:
  1. TNFa
  2. Lymphotoxin a (formerly TNFb)
  3. Lymphotoxin b
• Cleaved from the membrane by TNFa converting enzyme (TACE).

Question 2

What are the TNF receptors?

Answer 2

• Both TNF and LT bind to a family of receptors
• TNF receptor 1 (TNFR1, p55, CD120a):
  1. Constitutive on all cells except RBC
• TNF receptor 2 (TNFR2, p75, CD120b
  1. Inducible on endothelial & haematopoietic cells
• LTb receptor binds LT only

Question 3

What are the key actions attributed to TNF-A?

Answer 3

Question 4

How is TNF inhibited?

Answer 4

1. Via three approaches:
   - Bind to receptor and block TNF binding
   - Bind to TNF and block binding to receptor
   - Block TNF synthesis
2. No inhibitors of receptor
   -Which receptor to inhibit?
3. Thalidomide blocks TNF synthesis
4. Targeting TNF is main strategy

Question 5

Discuss the Anti-TNF therapies.

Answer 5

1. Anti-TNF monoclonal antibodies:
   - Infliximab (25% murine/ 75% human).
   - Adalimumab (100% human)
2. Soluble TNF receptors:
   - Etanercept (100% human).

Question 6

What are TNF biologics?

Answer 6

• TNF inhibitors.
• Drugs that help stop inflammation.

Question 7

Give example of TNF inhibitors.

Answer 7

1. Etanercept
   - Human TNFR2-Fcg fusion
2. Infliximab
   - Chimeric whole antibody
3. Adalimumab & golimumab
   - Whole human antibodies
4. Certolizumab
   - Humanised Fv conjugated with PEG
   *Typically 60-70% response rate

Question 8

What is the connection of Anti-TNF therapy to infection?

Answer 8

• Increases risk of infection.
• TB is a serious issue in Etanercept and Infliximab patients.
• Pre- screening of patients is recommended.

Question 9

What is the effect of antibody formation on anti-TNF drugs?

Answer 9

• Antibodies reduce efficacy of Moabs
• Reflected in loss of efficacy
• Requires dose escalation
• Not a problem with etanercept

Question 10

Discuss the clinical use of Anti- TNF agents.

Answer 10

• Used for treatment of a number of autoimmune diseases (not all agents approved for all indications):
  1. Rheumatoid arthritis
  2. Poly-articular juvenile idiopathic arthritis
  3. Psoriatic arthritis
  4. Psoriasis
  5. Ankylosing spondylitis
  6. Crohn’s disease
  7. Ulcerative colitis

Question 11

What is co-stimulation and what is co-inhibition?

Answer 11

1. Co-stimulation: co- stimulatory receptors triggering T cell receptor activation:
   - CD28 activation is also required
   - APC B7-1 (CD80) & B7-2 (CD86) are CD28 ligands
   - Activated T-cells express CTLA-4 which inhibits T-cell activation and Ligands are B7-1 & B7-2.
2. Co-inhibition:
   - Activated T-cells also express Programmed Death (PD)-1
   - Bind PD-Ligand 1 (PD-L1)
   - Inhibits T-cell activation

Question 12

Discuss the structure of B7/CD28 family.

Answer 12

• Structures are modelled on the crystal determinations.
• Loops have been added to one end of the IgV domains to emphasise the orientation of the CDR-like loops and their interaction with ligand or lack thereof.

Question 13

What is Progressive multifocal leukoadenopathy (PML)?

Answer 13

• A disease of the white matter of the brain.
• Caused by a virus infection that targets cells that make myelin neurons.
• Viruses:
  1. Re-activation of JC virus in the brain
  2. Herpes virus 6 re-activation also seen
• High mortality rate.

Question 14

What is Systemic Inflammatory Response Syndrome (SIRS)?

Answer 14

1. Categorised as having 2 or more:
   - Fever of > 38°C or < 36°C
   - Hr > 90 beats per minute
   - Respiratory rate of more than 20 breaths/min or PaCO2<32 mm Hg
   - Abnormal WBC (>12,000/mL or <4,000/mL)
2. Infectious or non-infectious
3. Due to activation of pro-inflammatory cytokines
   - TNF
   - IL-1,6&8
   - IFNg

Question 15

Discuss CTLA-4 fusion proteins: Abatacept & Belatacept.

Answer 15

• Binds to B7-1&2 preventing their interaction with CD28.
• Reduces TNFa, IFNg and IL-2 secretion.
• Abatacept has higher affinity for B7-1 (CD80) than B7-2 (CD86):
• Approved for RA and not transplantation
• Belatacept differs from abatacept in two amino acids and has higher affinity for CD86:
• Approved for organ transplantation (2011)

Question 16

Discuss immunotherapy in Cancer.

Answer 16

• Potential for immune system to deal with cancer.
• However, tumours can circumvent the immune system.
• Drugs that block the inhibitory pathways can be used to enhance anti-tumour activity.
• Known as checkpoint inhibitors.

Question 17

Give examples of immunotherapy drugs used in cancer.

Answer 17

• Ipilimumab is a monoclonal antibody that binds to CTLA-4 and blocks the inhibitory pathway.
• Nivolumab and pembrolizumab bind PD-1.
• Atezolizumab binds PD-L1.
• Primarily used for melanoma and lung cancer.

Question 18

Discuss adaptive immune system resistance.

Answer 18

• Adaptive up-regulation of PD-L1 is mediated predominantly by IFNγ through activation of the STAT proteins.
• The adaptive expression of PD-L1 has been observed in the surface of cancer cells, stromal cells, and infiltrating immune cells, including T cells.

Question 19

What is CD2?

Answer 19

• Another co-stimulatory receptor on T-cells.
• It binds LFA-3 on antigen presenting cells.

Question 20

Discuss fusion protein: Alfacept.

Answer 20

• Blocks LFA-3 on APC and Fc portion of IgG1
• Approved for use in plaque psoriasis
• Binds to CD2 on memory T-cells preventing activation
• Triggers NK cell-mediated apoptosis of activated T-cells.
• Withdrawn.

Question 21

Discuss a Anti-CD28 Antibody (TGN1412).

Answer 21

• Superagonist antibody
• Activates immune system
• In animal models increases type 2 helper cells and regulatory T cells
• Showed benefit in animal autoimmune disease models
• In human study serious adverse effects
  1. Cytokine storm
  2. Systemic inflammatory response syndrome (SIRS)
• Withdrawn.

Question 21

Discuss a Anti-CD28 Antibody (TGN1412).

Answer 21

• Superagonist antibody.
• Activates immune system.
• In animal models increases type 2 helper cells and regulatory T cells.
• Showed benefit in animal autoimmune disease models.
• In human study serious adverse effects:
  1. Cytokine storm
  2. Systemic inflammatory response syndrome (SIRS)
• Withdrawn.

Question 22

What is the role of adhesion molecules?

Answer 22

• Immune cells must adhere to target to be effective.
• Full activation often requires adhesion.
• Adhesion is mediated by families of adhesion receptors:
  1. Integrins
  2. Immunoglobin superfamily

Question 23

What are Integrins?

Answer 23

• Family of cell adhesion molecules.
• All are a/b dimers.
• Involved in many cellular functions:
  1. GPIIb/IIIa (aIIbb3) on platelets.
  2. b2 integrins on lymphocytes.
• Ligands are usually proteins.

Question 24

Discuss Integrin activation.

Answer 24

Question 25

Discuss the MOA of Efalizumab.

Answer 25

• Monoclonal antibody to aLb2 (LFA-1, CD11a)
• Blocks T-cell binding to endothelial cells
• Used in the treatment of psoriasis
• Withdrawn from the market due to PML (Progressive multifocal leukoadenopathy).

Question 26

Discuss the MOA of Natalizumab (Tysabri).

Answer 26

• Monoclonal antibody
• Binds to a4 integrins (a4b7 & a4b1)
• Thought to block binding of inflammatory cells to endothelium
• Prevents infiltration by lymphocytes into brain
• Shows some benefits in MS
• Causes PML (2 per 1000 cases).

Question 27

Compare RMP & REMS.

Answer 27

1. REMS: Risk evaluation and mitigation strategy
   - Tysabri Outreach Unified Commitment to Health (TOUCH).
   - FDA REMS uses specific company communication plans.
2. RMP: Risk Management Plan.
   - EMA equivalent .
   - Uses summary of product characteristics (SMP) to communicate precautions with drugs.

Question 28

Discuss other a4b7 antagonists.

Answer 28

• Vedozilumab is an antibody that binds to a4b7.
• Etrolizumab is an anti-b7 antibody.
• Both are approved for Crohn’s disease and ulcerative colitis.