antibody based approaches to cancer therapy

describe the structure of chimeric antibodies and their % relationship with human antibodies?

they have the mouse variable regions but human constant region. 60% related

describe the structure of humanized antibodies and their % relationship with human antibodies?

they have mouse hypervarible region, with human constasnt region. 95% related

how were human monoclonal antibodies produced through mice?

the human IGg gene was inserted into the mouse

what were the key issues associated with murine antibodies?

low cytotoxicity to cancers, immunogenic, short half life

how does trastuzumb work to interfer with cell signalling in the treatment of breast cancer?

HERT2 is a growth factor that is over expressed in breast tumors. trastuzumab is antibody made agaisnt HERT 2 receptors which prevents the downstream signalling action of HERT which inhibits the growth of the tumor. it can also interfere with dimerisation of the HERT 2.

what are the two mechanism of cell killing for naked MAbs?

activation of t-cells, or natural killer cells OR through complement.both processes result in the apoptosis of cells

what growth factor can be targeted by antibodies to interfere with vasculature of tumors?

VEGFR

what are immune checkpoints and what is their purpose?

receptors that sit on the surface of t cells that prevent the over activation of the immune system when bound to

For a t-cell to become activated what two activation signals does it need?

1. binding of the antigen through the MHC C1 complex

2. binding of the B7 to the CD28 receptor.

how does CTL4 acts as a immune check point?

it binds more tightly to the B7 proteins which prevents binding of the CD28 receptors, thus preventing activation. acts like a brake

how do the ctla-4 inhibitors works in the treatment of cancer as check point inhibitors?

ctla 4 is highly expressed in the tcells of tumors, so by inhibiting these, the antibody is reactivating the immune system by allowing the binding of cd28.

what is an example of ctla4 inhibitor?

ipilimumab

how do bi specific monoclonal antibodies work?

they target two different types of antigens, and can physically bring together a tumor and a t cell

what is an example of a bi specific antibody and what receptors does it bind to?

blinatumomab- binds to CD19 which is over expressed in leukemia and CD3 which is on tcells.

what are the three components in antibody drug conjugates( ADC)?

antibody, linker, drug aka payload

what is the bystander effect in ADC? and why is this helpful?

phenomenon where cancer cells that are not targets to the antibody are also killed as they are in close contact to where the payload was released, and the payload has not yet been taken up by the tumor cell.

what does the drug antibody ratio( DAR) tell us?

how many molecules of payload can be attacked to an antibody.

why is balancing the DAR important?

must be high enough to be efficacious but not high enough to cause systemic toxicity

what is thiol conjugation in DAR loading?

antibodies are reduced in mild reducing conditions which leads to breaking of some disulphide bridges which can react with functional groups in the linker, to attach the payload.

what are some issues associated with thiol conjugation?

there is no way to control the the number of exposed sulfur so binding of the payload will vary from antibody to antibody

give examples of some payload release mechanisms?

protease sensitive, pH dependent- tumors are more acidic,

what is a main issue in conjugating payloads?

they are highly hydrophobic so it makes them difficult to conjugate.