Biologics and advanced formulations I

what are the three components of an antibody drug conjugate

• tumour specific monoclonal antibody

• linker - cleavable (chemical or enzymatic), non-cleavable (undergo catabolism), plasma stability

• cytotoxic payload. Conventional, intracellular targets tubulin or DNA, unconventional eg TOPO inhibitors, immune stimulations, Drug t antibody ratio

what are benefits of ADCs

• they limit the toxicity of small molecule drugs used for chemotherapy and off target effect with specific targeting of monoclonal antibodies

what are the three regions of an antibody

• Fab region - binds to specific antigens

• CDR region - found within the fab region, actual part that makes contact with the antigen, give the antibody its specificity

• hinge region for flexibility

• FC region involved with antibody recycling

what is the DAR

• it reflects the number of cytotoxic payloads that are attached to one monoclonal antibody

how many ADCs are approved and what is an example

• 1000s in the pipeline but only 12 are approved globally

• 2 approved for Trastuxumab (Herceptin that targets HER2) positive breast metastatic cancers

• TDM-1 DAR 3.5

• T-Dxd DAR 8

why do hydrophobic drugs make purification and formulation difficult

• they aggregate

what mode of action do ADCs follow

• they follow the mode of action of the MAB then the payload of the small drug

what are the 3 ways in which the cytotoxic drug is released

• when released the cytotoxic drug relies on 3 mechanisms

• microtubule polymerisation inhibition

• topoisomerase 1 inhibition

• DNA alkylation

what is the basic mechanism of action of an ADC

• bind to target antigen on cancer cells

• uptaken into the cell

• the antibody component is degraded

• cytotoxic drug is released

what effect should an ADC have on the maximum tolerated dose

• idea that ADC would improve the MTD and decrease effiacious dose

• however trials suggest that ADCs do not increase the MTD of conventional chemotherapeutics

• when the MTD is converted to normalised cytotoxin content ADCs are similar to conventional cytotoxic drug

• ADCs with lower DAR have higher antibody doses but normalised cytotoxin remains the same

what are the two types of linkers and how do they work

• cleavable, release drug via proteolysis, reduction, pH

• non-cleavable, follow full catabolism

what are the two types of instabilities that are related to linkers

• linker-drug (expected release of drug, linker attached to antibody and drug released)

• mab- linker (more problematic, linker and drug go separately from the mab )

what are examples of improved ADC’s

• all are cleavable

• 7 use thiomalemide conjugation and 4 conjugated to lyseine

• maldemide caproyl linkers: rapid release 50% in one week

• malemide propionyl linker only 20% of the drug is released over one week

what happens if the malemide linker drug (antibody drug conjugate) undergoes hydrolysis

• the conjugate is stable

what happens if the malemide linker drug (antibody drug conjugate) undergoes deconjugation

• the malemide linker drug can then react with albumin in the circulation to form an albumin drug conjugate

• albumin-malemide-linker-drug

• albumin FC region is recycled

how do DM1 and Dxd cleave

• DM1 cleaves, linker and drug and drug is released in solution

• DXd linker drug reacts with albumin

how have ADCS shown efficacy

• in clinics they have shown improved efficacy

• showed efficacy in patients with tumour type that did not show significant response rates with chemotherapeutics

• no randomised trials comparing ADCs with their direct administered payload

• T-DXd experience 42% overall response rate to physicians choice of chemotherapeutic

how are ADCs distributed using radiolabelled mab trastuzumab

• on tarhey on tumour typically less than 1%

• off target including on target off tumour >99%

• 1/3 in circulation

• 15% in the liver

• 4% in the spleen and kidney

• 5-7% in adipose tissue

• <1% in tumour lesions

what are the possibilities that could happen with an ADC

• ADC goes on target on the tumour, if it goes well during metabolism drug is released, drug goes to tumour. ,

• Linker instability - may happen in circulation, two types of instability (antibody linker instability, linker drug instability). ADC with lower DAR and have free linker floating around that can react with albumin. Off tumour cellular uptake drug then released inside the tumour cell

• Linker drug lower DAR and free drug, free drug behave same as cytotoxic free drug, can act on the tumour but on all the other cells in the body

• Normal tissue uptake on target off tumour cellular uptake, may find receptor somewhere else, release drug, normal metabolism in normal cells 

what factors affect the toxicity of ADCs

• payload potency and drug linker properties often correlate with target independent side effects

what toxicities can mysansinoid ADC’s (TMD-1) cause

• may induce neuropathy, liver toxicity and thrombocytopenia

do ADCs improve toxicity of cancer therapies

• ADCs have not yet delivered on improving the safety of anticancer treatments

• most ADCs harbour similar or worse toxicity

• pre targetting with mAb before use of ADC: trastuzumab for TDM-1 or Dxd reduces off target toxicity

how does target expression influence the response to ADCs

• certain ADCs exhibit superior efficacy in patients with high target expression

• no correlation was found between response rate and target expression

• influence site and rate of deposition

can you use in sequence 2 adc’s

• if use 2 adcs in sequence that share the same target but different payloads it does not produce significant cross-resistance

• testes with patients first treated with TDM1 then with either T-DXd or an inhibitor

what are mRNA vaccines used for

• they are used to induce or boost (antitumour) immune response

• synthetic mRNA encoding tumour associated or tumour-specific antigens

• non approved so far

what are advantages of mRNA vaccines

• well tolerated

• easily degraded

• do not integrate into the host genoome

• mRNA molecules are non-infectious

• production can be fast and inexpensive

Delivery can be

• non formulated

• formulated (mostly lipid based)

• via dendritic cells (autologous GT)

what is the mode of action of mRNA vaccines

• the formulated vaccine is internalised by endocytosis

• mRNA is transported in the cytoplasm to undergo antigen processing

• ribosome translates mRNA into proteins

• activation of CD4+/ CD8+ T cells

what are components of mRNA vaccines

• lipid nanoparticles around 100nm

• particles made of 4 components plus mRNA mixed rapidly in microluidic systems

• cationic ionisable lipid (MC3 or others)

• cholesterol (or other sterol)

• phospholipid (DOPE or DSPC)

• pegylated lipid (DMG-PEG2000)

what can fine tuning modification ratios allow

• can improve the potency of the formulation

• modify organ targeting

what is release from the vaccine triggered by

• pH triggered during endosomal maturation, change of lipid arrangements and release of mRNA

what does PEG ensure

• ensures colloidal stability and reduces plasma adsorption on the lipid nanoparticle

why is a cationic ionizable liquid used in mRNA vaccines

interacts with the mRNA, then when it becomes unionized the mRNA will be released

describe the properties of mRNA based dendritic cell vaccines

• unique ability not only to initiate immunity but also to control and regulate the type of immune response

• generate an ex-vivo population of antigen loaded dendritic cells able to stimulate robust and long lasting cd8+ and cd4+ T cell responses in patients with cancer

what is a disadvantage of mRNA dendritic vaccine

• obtaining a source of dendritic cells and their ex-vivo manipulation are laborious and time consuming

• induce modest T-cell response and have low clinical efficacy

how can mRNA vaccines be used as personalised medicines

• by identifying tumour specific mutations or non-conforming sequences and predicting corresponding neoepitopes for individual HLA alleles

• need for rapid large scale good manufacturing practice

why is the IM route good for distribution

-it is highly vascularised and has less injection site reactions

how does the IV route impact distribution

• IV allows the vaccine to reach numerous lympoid organs and lead to a robust CD8+ T cell response

what are mrna vaccines

• therapeutic rather than prophylactic

what are challenges to mrna vaccines

• storage is problematic

• challenges in personalised medicine and production

can therapeutic vaccines succeed in combination with other immunotherapeutic methods

• less likely to succeed