BBB L4

Question 1

What are the Advantages of using Ab or biologic therapeutics?

Answer 1

• High specificity –> target single aspect of disease e.g.
• Reduce amyloid peptide production
• Reduce tau neurofibrillary tangles
• Apoptosis
• Deliver growth factors
• few s/e elsewhere in the body

Question 2

What are the Disadvantages of using Ab or biologic therapeutics?

Answer 2

Very large, 150 kDa - hard to cross BBB

Question 3

Why is there a lack of success for these molecules and what evidence shows this poor success

Answer 3

• results poor for crossing BBB

- no previous/current trials targeting BBB

Question 4

How can we optimise Ab delivery for the BBB? (2 approaches)

Answer 4

1) Ab and RMT approach - use ‘trojan Ab’

2) Bi-Specific i.e. Trojan and Therapy in one Ab

Question 5

How is the Ab that targets RMT made?

Answer 5

Using human TfR –> put into rabbit –> rabbit expresses Ab against TfR –> harvest Ab for TfR –> use as trojan

Question 6

Give an example of a formulation made for Ab-RMT and the disease it targets

Answer 6

HIR (Human Insulin Receptor) with GDNF (Glial cell Derived Neurotrophic Factor)

Targeting Parkinson’s Disease

Ab attaches to the HIR at the BBB - enables transcytosis and delivery of cytotoxic payload

This showed off-target effects due to accumulation in the liver and spleen - little in the lungs = beneficial.

Question 7

What were the effects of HIR + GDNF Ab?

Explain why.

Answer 7

• Pacreatic toxicity
• Fibrosis and lesions

Even with low doses = due to abundance of insulin receptors in the pancreas

Question 8

What is a Bispecific Ab?

Given an example and what does this treat?

Answer 8

One = trojan, One side = therapeutic

• Trojan = TfR
• Therapy = BACE1 enzyme (for breakdown of amyloid protein)
• Treats Alzheimers disease

Question 9

How are the bispecific Ab made?

Answer 9

Combine two Ab - Heavy and Light chains from each of Ab’s with Trojan and Therapy

Question 10

What problems are encountered with use of Trojan Antibody therapy?

Answer 10

• too high affinity

therefore they get stuck in vesicles upon endocytosis, as well as stuck in the blood-side of the BBB = not reach cell.

Question 11

How is the problem of too high affinity resolved for Trojan Ab therapy?

Answer 11

Reduce the affinity BUT still need efficacy, therefore, balance:

• Lower affinity
• High brain uptake

i.e. low affinity but not too much so doesn’t bind TfR, but need enough affinity to still allow therapeutic action

Question 12

What were the effects seen in the optimised TfR/BACE1 Bi-specific Ab?

Answer 12

• Increased BACE1 levels in brain = decreased amyloid protein (by approx. half)
• reduced amyloid = shows restoration of cognitive ability - due to threshold of amyloid = regain cognition

Question 13

What are the limitations with use of Ab therapy?

Answer 13

• Very expensive
• Need high synthesis rate
• Only administered IV = compliance issue (need to be in hospital)
• Cannot administer large depot = due to protein overload = need to give over hours