Cispaltin And Analogues Flashcards

1
Q

What is the mechanism of action for cisplatin and its analogues

A

Formation of platinum-DNA adducts
Activate various signal transactions pathways

Involve cross-linking of 2 nucleotides

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2
Q

What 2 nucleotides are usually affected by cisplatin and its analogues

A

Guanine and adenine

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3
Q

What is the mechanism of action for cisplatin

A

Kill tumour cells as a direct consequence of the damage caused by their reaction w DNA
Correlated closely with covalent binding to nuclear DNA

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4
Q

What do the most active platinum compounds have in common

A

2 labels bonds to platinum atom
= can from 2 bonds w cellular target molecules

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5
Q

What is the metabolism of cisplatin

A

Cisplatin -> squealed platinum complex -> DNA cross links

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6
Q

What is the rate limiting step in the reaction of platinum

A

Intracellular hydrolysis

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7
Q

Describe the metabolism of carboplatin

A

Carboplatin -> monofunctional adduct -> bifunctional adduct

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8
Q

Why does carboplatin have a lower interaction with DNA compared to cisplatin

A

Due to the slow loss of the second arm of the bidentate ligand

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9
Q

What is the major difference bwteeen cisplatin and carboplatin

A

Kinetics of adduct formation not the nature of the reaction with DNA

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10
Q

What is the most common type of cisplatin adduct formation

A

Intrastrand cross links
Less than 10% interstrand and DNA-protein cross-links

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11
Q

Why are testicular cancer cells limes hypersensitive to cisplatin

A

Reduced DNA-repair activity in response to adducts
Low constitutive nucleotide excision repair pathway
Low DNA repair capability = cisplatin induced apoptosis

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12
Q

What are the two classes of resistance to platinum agents

A

Reduced access of drug to target DNA i.e decreased uptake into cells, changes in tumour vasculature
Increased repair or tolerance of DNA damage

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13
Q

What is the mechanism of resistance to cisplatin when there is insufficient DNA binding

A

Related to decreased drug uptake by CTR1
Increased levels of cytoplasmic thiol-containing species

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14
Q

What is the mechanism of resistance to cisplatin when there is resistance mediated after DNA binding

A

Increased DNA-repair capacity
Increased tolerance to platinum-induced DNA damage through loss of MMR pathway = decreased apoptosis
Decreased expression of apoptotic signalling pathway

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15
Q

What is the DNA-repair pathways that is known to remove cisplatin lesions from DNA

A

Nucleotide - excision repair (NER)

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16
Q

How can the influx and efflux of cisplatin in tumour cells be affected

A

Influx: CTR1
Efflux: ATP7a/b

17
Q

What are the different strategies used to circumvent cisplatin resistance

A

Increased delivery of platinum to the tumour
Platinum resistance modulators
Combination of platinum drugs with molecularly targeted agents
Novel platinum drugs targeting resistance mechanism

18
Q

What have in vitro studies shown to be the major cause of cisplatin resistance

A

Reduced drug uptake

19
Q

What malignancies can cisplatin be used to treat

A

Germ cell tumours
Ovarian cancers
Head and neck cancers
Bladder cancers
Childhood cancers

20
Q

What are some severe acute and long-term toxicities of cisplatin

A

Nephrotoxicity
Neurotoxicity
Ototoxicity
Nausea and vomiting

21
Q

What malignancies can carboplatin be used to treat

A

Germ cell tumours
Ovarian cancers
Childhood cancers
High dose chemotherapy regimes

22
Q

What are some of the severe acute and long-term toxicities of carboplatin

A

Haematological toxicities e.g thrombocytopenia and neutropenia
Nausea and vomiting

23
Q

What does measuring ultrafilterable platinum show

A

Non-protein bound platinum species with anti tumour and toxic properties

24
Q

What does measuring the total platinum show

A

Protein bound and ultrafilterable platinum species

25
Q

How are platinum compounds usually administered

A

IV infusion with variable infusion times

26
Q

Describe the current approaches to carboplatin dosing

A

Renal function based carboplatin dosing
Almost all drug elimination via kidenys
Rest remains protein bound

27
Q

What is the formula used to calculate dose of carboplatin to achieve a particular exposure

A

Total dose = target AUC x (GFR + 25)

Target AUC values commonly 5-7mg/ml.min

28
Q

Name 4 alternative platinum complexes

A

Oxaliplatin
Satraplatin
Picoplatin
BBR3464

29
Q

Describe oxaliplatin

A

Superior anti-tumour effect and reduced toxicity vs cisplatin
Lack of cross-resistance w other Pt agents

Neurotoxicity and nausea/vomiting

30
Q

Describe satraplatin

A

Oral administration
Comparable activity w carboplatin/cisplatin
Lack off cross resistance w cisplatin
Reduced inactivation by thiol containing species

No nephro/neurotoxicity

31
Q

Describe picoplatin

A

First oral and IV drug
Activity in carboplatin/cisplatin resistant tumours
Steric hindrance to inactivation by thiol-containing species

Myelosuppresion

32
Q

Describe BBR3436

A

Adducts formed may be less susceptible to repair i.e persist longer than those formed by cisplatin
Activity in tumours resistant to cisplatin