WEEK 4 - Antibody Drug Conjugates and mRNA vaccines for cancer treatment Flashcards
(25 cards)
What are ADCs: structure, aim
ADCs - Antibody Drug Conjugates
ADCs are mAbs
Structure:
- 2 antigen binding sites:
- FaB region + Fc region
- makes ADC tumour specific
- Fc region - recycles antibody
- Linker - can be cleavable or non-cleav.
- cleaveble: chemical or enzymatic reaction, pH changes
- Cytotoxic payload - attached to ADC by linker
Aim:
- limit toxicity
- limit off-target effects for drugs used in chemo (is tumour specific)
- improve maximum tolerated dose
= kill more cancer cells + ↓ pt SE
- improves pt efficacy
- e.g. in tumour unresponsive to chemo
What is the MoA of ADCs
- Binds to specific receptor on surface of tumour cell
- has high affintiy for tumour
- ADC is endocytosed (internalised) into cell
- Changes in pH (in endosome) linker cleaved
- Cytotoxic payload is released (in endosome)
- Drug moves to DNA / other areas = apoptosis of cancer cell
Cytotoxic Payload MoA:
1. Cause DNA alkylation
2. Cause TOPO1 ihibition
3. Microtubule polymerisation inhibtion
NOTE: has high circulation time (compared to small molecule drugs)
Give an example of an ADC
Transtuzumab (Herceptin)
- targets HER-2 in positive MBC
Transtuzumab has 2 approved ADCs:
1. Transtuzumab Emtansine (TDM-1)
- DAR of 3-5
2. Transtuzumab deruxtecan (T-Dxd)
- DAR of 8 (but has lower cytotoxicity)
- Preffered over TDM-1
Why is DAR
Drug to Antibody Ratio
Reflects the no. of cytotoxic payloads attached to 1 mAb (ADC)
NOTE:
- higher no. doesnt always mean more cytotoxic
- drugs with ↓ DAR have ↑ antobody dose
Explain the type of instabilities ADCs suffer and their distribution
- Linker-drug Instability
- linker remians attached to ADC + drug is released
- PREFFERED - mAb-Linker Instability
- linker AND drug de-attach from ADC
- if de-conjugation occurs = off target effects (as linker+drug is in circulation)
- linker+drug can bind to albumin = albumin drug conjugate = problem (don’t know how this behaves)
All approved ADCs are cleavble
- Maleimide propionyl linker
- Maleimide caproyl linkers
- Malemide linkers are cleaved by hydrolysis
- Complex to purify sample (need to remove non-attached linkers + payload)
Explain toxixities of ADCs and how to manage
- On-target but off-tumour
- receptor is highly expressed by tumour BUT still expressed in other areas
Off target effects
- mAb-linker instability = in circulation
- can form albumin drug conjugates
Management:
- Before using ADC, can pre-target with mAb
- mAb (has no payload)
- Fine tune ADCs
- improve pH dependency, binding affinity, PK, slectivity, tolerability
How can ADCs be optomised
- Change payload volume (DAR)
- attach 1 or more payloads
- Change Payload potency
- higher payload = higher potencies
- ca]hanges toxicity
- Linker
- make polar or lipophilic
- changes conditions it will be cleaved
- Antibody
- is it bidning to specific target for tumour cell
What are the potential of these therapies (ADCs)
- limit toxicity
- limit off-target effects for drugs used in chemo (is tumour specific)
- improve maximum tolerated dose
= kill more cancer cells + ↓ pt SE - improves pt efficacy
- e.g. in tumour unresponsive to chemo
BUT
- requires a lot of optimisation due to toxicities from instability
What are mRNA vaccines (in relation to cancer mgmt.)
NOTE: no approved cancer mRNA vaccines
Induce / boost anti-tumour immune resposne
NOTE: usually used therpaeutically rathern than prophylatically
How are mRNA vaccines formulated
- Include synthetic mRNA encoding for tumour-specific antigens
- need to know biomakers / antigens specific tumour has to produce accurate mRNA
Can be delivered in 3 ways:
1. Non-formulated = not ideal, easily degraded
2. Formulated = lipid nanoparticles
3. via Dendritic cells = cell-engine therapy
What are the 4 components in Lipid NP mRNA vaccine formulations
NP = nanoparticles
- SIZE: 100nm
- Fine tuning 4 components = ↑ potency + target dif. organs
4 Components:
1. Cholesterol
- solidifies particles
2. Phospholipid
3. PEGylated lipid
- ensures collodial stability
- ↓ albumin adsorption
- make oarticle less recognisable to immune system
4. Cationic ionizable lipid
- un/ionisation depends on pH
PLUS the mRNA
What are mRNA based dendritic cell vaccines
Proccess, DIsadvantages
Can initiate immunity AND control / regulate type of immune response
Proccess:
- Generate ex-vivo antigen-loaded dendrirtic cells
- Dendritic cels stimulate long-lasting CD8+, CD4+ and T cell response
Disadvantages:
- Time consuming process
- Obtaining right source of dendritic cell
- Has low clincial effciacy
What is the MoA of mRNA vaccines
- Synthesised mRNA is internalsied by endocytosis
- mRNA is transported in cytoplasm
- mRNA undergoes antigen processing
- mRNA is released + enters ribosome
- Ribosome produces proteins
- Proteins activate MHC 1 and 2 systems
- CD4+ and T cells activated = immune response against tumour antigens
- Allows immune system to rediscover tumour + mount resposne
What are the advantages of mRNA vaccines
- Well tolerated, non-infectious
- Degrades easily
- Do NOT integrate into host genome
- Production is fast + inexpensive
What are the challenges for mRNA vaccines
- Need to KNOW ALL specific antigens produced by tumour cell
- if miss some antigens = wont stop disease targetted
- Administration = IM or IV
- IM = less injection site reaxtion
- IV = can reach many lymphoid organs = robust CD8+ T cell response - Storage of produced vaccine
Cell and Gene Therapy
What are ATMPs are and their associated landscape
ATMPs - Advanced Therapy Medicinal Products
Can include GT, SC and GE
NOTE: newer therapy, recently approved
Define:
1. GT
2. SC
3. TE
Gene and Cell therapy
- GT - Gene Therapy
- SC - Somatic Cell Therapy
- TE - Tissue Engineering Therapy
List the 3 different type of cell and gene therapy
What it is, consists off, use
- GT
- Consists of recombinant nucleic acid
- Uses viral therapy
- Is used in humans
- Regulates, repairs, replaces, adds, deletes genetic sequencing
- Can be used: theraputically (treat), prophylatically (prevent) or diagnostically - SC
- Cells that have been maniupulated substantially to have altered characteristics / phsiological function
- Can be used: treat, prevent and daignose in humans
- Requires GT to modify cell
- Cells: adult stem cells, cartilage, embryonic, dendritic, immunotherapy - TE
- Enginereed cells or tissues (human or animal)
- Tissues selected can be viable or non-viable
- Requires GT to create new tissues
- Used in / admisntered ti gumans
- Regenerates, repairs, replaces human tissue
How is SC therapy achieved and the 2 types of SC
Process:
1. Extract cells from pt donor
2. Using microscope select correct cells + modify them
3. Grow modified cells till sufficient amount
4. New cells are given to pt
NOTE: requires GT
2 Types:
1. Autologous = take cells from in pt, select correct cells, modify them, grow them, then re-inject them back into patient
2. Allogenic = find healthy donor with right type of cells, then inject them into pt
How is TE therapy achieved
- Take cells from pt
- Modifiy + grow till sufficent amount
- Administer to pt to replace organs / part of organ etc.
NOTE: requires GT
List the 4 viral aprticles that can be used in gene therapy
Viral vectors
- Adenovirus
- Non-integrating: preffered as it has no interference with human Genome
= cant cause host damage
- Non-integrating: preffered as it has no interference with human Genome
- AAV
- Non-integrating: preffered as it has no interference with human Genome
- gamma-Retrovirus
- Used for ex vivo studies
- integrates inot genome = stable expression
- Lentivirus
- Used for ex vivo studies
- integrates inot genome = stable expression
NOTE:
- all viruses have diff. sizes, genome sequence, expression, immunogenecity
How is CAR T cells used in gene and cell therapy
CAR - Chimeric Antigen Receptor | MoA
MoA
1. Extract T cells from pt blood
2. Genetically modify T cell with viral vector (Lentivirus / gammavirus)
3. Collect host T cells + mix with virus
4. Host T cell will grow artificial antigen receptors e.g. CAR
5. CAR T cells are growin in lab till reah sufficicent no.
6. Once reached, CAR T is given back to pt via IV
7. CAR T cells track cancer cell, bind to antigen on cell = cell death
8. CAR T moves onto next sample
CAR T: Approved products
Excipients
- Kymirah
- a geneticially modified autogolous cell-based prosuct
- contains CAR T
- packaged in 1 or more infusion bags
- Excipients: glucose, NaCl, Dimethyly sulfoxide, Potassoum chloride
- STORAGE: ≤120ºC (low temps)
- Yescarta
- Zolge
What are the toxicities of CAR T
- Causes release of interleukin-6 cytokines (when CAR T interacts with leukemia cells)
- cause cytokine release syndrome
- syndrome: 1st line treatment = mAb
