Immunogenicity

Question 1

what is immunogenicity

Answer 1

the ability of any molecule to provoke an adaptive immune response
- the outcome of interplay between biological systems and the biophysical/chemical properties of the protein itself
- always mediated by T cells
- such responses are vital to protect from disease or are induced by vaccination

Question 2

what do anti drug antibodies cause

Answer 2

cause the biologic to be less effective or can even provoke immunogenicity

Question 3

what is immunogenicity in the context of biologics

Answer 3

an unwanted immune response and must be avoided as much as possible

Question 4

what are the immune system properties

Answer 4

1. immune tolerance
2. MHC class II haplotype
3. patient immunosuppression

Question 5

what are the immune system physicochemical properties

Answer 5

1. delivery and treatment
2. manufacturing
3. storage
4. formulation
5. expression system

Question 6

what can affect immunogenicity

Answer 6

effector T cells and regulatory T cells impact immunogenicity
- it is the balance between T effector and Treg cells that control immunogenicity

Question 7

what is immune tolerance

Answer 7

a state in which a T cell can no longer respond to an antigen

Question 8

what is the role of HLA genes

Answer 8

1. encode MHC II structures that present parts of therapeutic protein peptides on the surface of an APC to a T cell
2. the MHC II/peptides bind with high affinity to the naive T cell receptor and induce over activation and over proliferation of that T cell
3. the population of T effector cells created will induce antibody responses against that therapeutic protein

Question 9

how are HLA genes associated with immunogenicity

Answer 9

because they encode MHCs that bind these immunodominant epitopes very tightly

Question 10

what does HLA stand for

Answer 10

human leukocyte antigen

Question 11

explain the impact of immunosuppression on immunogenicity

Answer 11

1. if a patient is immunosuppressed due to:
   - age
   - taking immunosuppressive medicine
   - undergoing chemo/radiotherapy
   - HIV
   - Autoimmune disease
2. there is a high risk of immunogenicity due to their compromised immune system
   - but this doesn’t mean they have no T cells

Question 12

describe how route of administration affects immunogenicity

Answer 12

1. skin/mucosal surfaces show marked differences compared to blood
   - they have a lot of APCs and extra types of T cells
2. injecting therapeutic proteins sc or intradermally is more likely to induce immunogenicity
3. therapeutic proteins are often administered IV if other risk factors are apparent

Question 13

describe the effect of drug dose, frequency and duration of treatment on immunogenicity

Answer 13

1. short term treatment is less likely to cause an immune response than long term
2. products given continuously are less likely to be immunogenic than if given intermittently
   - maintenance of trough levels
3. re-exposure after a long interval is often associated with an enhanced immune response
4. lower dose of infliximab is more immunogenic than higher dose

Question 14

give examples of manufacturing issues that may impact immunogenicity

Answer 14

1. 3d structure of mAB- biologic may change during manufacturing process
2. contaminants- endotoxins, breakdown products
   - can become incorporated into the product
3. all contaminants can act as adjuvants, altering the immune response to the therapeutic MAB in an uncontrolled manner

Question 15

describe the issue of aggregation during storage

Answer 15

1. therapeutic mabs are very prone to aggregation which can be caused by manufacturing process/storage
2. mabs must be carefully stored
3. aggregated mabs create new epitopes and may become highly immunogenic

Question 16

what are the 3 main expression systems used

Answer 16

1. bacterial
2. mammalian cells
3. transgenic animals

Question 17

describe the characteristics of the bacterial expression system

Answer 17

will not link heavy and light antibody chains, so can only be used to provide antibody fragments

Question 18

describe the characteristics of the mammalian cell expression system

Answer 18

will express full size, correctly folded, glycosylated IgG at high yield
- fully biologically active
- majority of approved HumAbs expressed in CHO

Question 19

describe the characteristics of transgenic animal expression systems

Answer 19

will express full size, correctly folded, biologically active, glycosylated IgG in milk

Question 20

explain how formulation can affect immunogenicity

Answer 20

1. the nature of excipients, buffers and adjuvants used with therapeutic protein can change its structure
2. silicon leaching from a vial closure altered structure of an experimental HIV therapeutic vaccine
   - even the infusion diluent and infusion device materials can have an effect

Question 21

describe the reactivity to Fab fragment of bDMARDS

Answer 21

1. Fab fragment of infliximab, adalimumab, golimumab and certolizumab have a neutralising capacity and interfere with binding of antibody to TNFa
   - expected with chimeric infliximab and humanised certolizumab
   - but not expected with fully human adalimumab and golimumab

Question 22

what is anti-idiotype reactivity

Answer 22

reaction of immune system to any novel antibody

Question 23

describe the reactivity to Fc fragment of bDMARDS

Answer 23

1. can form immune complexes with the drugs
   - enhance the rate of clearance by scavenging macrophages
2. ADAs can develop abatacept and etanercept

Question 24

describe what humanisation studies show

Answer 24

1. relationship between successful RA treatment with infliximab/adalimumab and the presence of ADAs
2. no association between ADAs and clinical response for etanercept, abatacept, certolizumab or golimumab as much lower risk of ADAs being induced
3. infliximab/adalimumab more immunogenic than other bDMARDs
4. humanisation is not a universal panacea for preventing immunogenicity

Question 25

outline other factors inducing ADAs during bDMARD therapy

Answer 25

1. high amount of TNF targets at baseline can consume a large proportion of the bDMARD
   - low trough levels of the drug= occurrence of ADAs
2. use of methotrexate reduced proportion of patients with ADAs by 41%
3. maintenance of a constant trough level of the biologic is best method for preventing ADA development
4. temporary withdrawal of treatment favours immunogenicity
5. obese patients have higher incidence of ADAs

Question 26

how can immunogenicity be tested and predicted

Answer 26

1. can’t use animal models to predict immunogenicity in humans
   - as we are interested in human recombinant proteins, these will almost certainly be immunogenic in any animal
2. human clinical trials- gold standard to detect and characterise ADAs
   - testing in double blind randomised trials
   - samples need to be taken for a period after the therapeutic protein has been eliminated
   - highest affinity antibodies will be bound to drug first
   - trials should continue for 6-12 months to monitor variation in immune responses