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Ama - Part 4 PM4B > Advanced drug delivery 4 - PDC > Flashcards

Advanced drug delivery 4 - PDC Flashcards

1
Q

General considerations for polymeric drugs

A
  1. Inert and non-toxic
  2. Polycations generally more haemolytic and cytotoxic than polyanions
  3. Polyanions generally less cytotoxic but can cause anticoagulant activity
  4. Toxicity is affected by MW
  5. Many polymers can be immunogenic
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2
Q

Effect of MW of polymeric drugs on elimination from body

A
  • Renal threshold of MW for elimination = ~40K Da

Biodegradable polymer:
- Can get broken down in the body so we can go above the renal threshold.

Non-biodegradable polymer:
- MW must be below renal threshold so that it can be excreted.
- Prevent accumulation of polymer in body

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3
Q

Ringsdorfs model

A

3(+1) model

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4
Q

What is a polymer drug conjugate

A
  • Drug delivery which involves a polymer covalently conjugated to a drug
  • API is low MWt
  • Each polymeric chain carries several drug molecules
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5
Q

Discuss the Ringsdord model of PDC 3(+1)

A

PDCs consist of 3(+1 optional)

Components
- Hydrophilic polymeric backbone
- Several low MW drug molecules
- Biodegradable linker that joins these
- Optional: targeting group

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6
Q

HPMA copolymer-DOX

A
  • First synthetic PDC to undergo clinical evaluation
  • Drug: doxorubicin, anthracycline
  • Drug delivery system designed to improve efficiency of doxorubicin while reducing toxicity to healthy cells
  • The HPMA copolymer acts as a carrier for doxorubicin while reducing its toxicity
  • Cardiac toxicity
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7
Q

What are angiogenic tumour vessels

A

Blood vessels formed in response to growth of a tumour

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8
Q

Tumour vessels <1-2mm

A
  • No induction blood supply
  • Obtains nutrients & O2 by diffusion
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9
Q

Tumour vessels >1-2mm

A
  • Tumour grows
  • Induction of angiogenesis
  • Blood vessels formed in cancer are somewhat different to normal blood vessels: endothelium is disorganised and poorly formed
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10
Q

> 200 mm3

A
  • Hypoxia and necrosis
  • observed in ~ 20 % of tumour volume
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11
Q

What is angiogenesis

A
  • Formation of new blood vessels
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12
Q

What is the Enhanced Permeability and Retention (EPR) Effect in tumour targeting?

A
  • Enhanced permeability = PDC accumulates in tumour tissue due to leaky angiogenic tumour vessels - these are only found in tumour tissue NOT healthy tissue.
  • Enhanced retention = due to less lymphatic drainage.
  • PDC is able to permeate and accumulate causing retention in tumour tissue to a higher extent than in healthy tissue.
  • Increased tolerable dose threshold
  • Higher concentration of PDC in tumour which is the main rationale of suggesting PDC for cancer therapy
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13
Q

EPR effect and dose thresholds for free dox and HMPA-copolymer-dox

A

Max tolerated dose for free dox: 60-80mg/m2

Max tolerates dose of HMA-dox: 320mg/m2

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14
Q

Define lysosomotropic

A

Drug that is able to penetrate the lysosomes of particular cell types

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15
Q

PDC for lysosomotropic delivery

A
  1. INJECTION: Inject PDC into the bloodstream (IV/SC)
  2. CIRCULATION: PDC circulates in the bloodstream and is extravasated through leaky blood vessels
  3. PDC accumulates in tumour tissue via EPR effect
  4. Once in interstitial space, the polymer has to enter the cell
  5. TARGETING: A normal low MW free drug can cross the barrier through passive diffusion and act as its target, but polymer cannot
  6. It is internalised by endocytosis
  7. UPTAKE: Once PDC reaches cancer cells, it would be taken up by the cell and transported to intracellular compartments e.g. lysosomes
  8. Lysosomes are acidic (pH ~5.5) and breaks down internalised material via acidic pH and enzymes
  9. RELEASE: Once inside the lysosomes the PDC would release the drug
  10. CLEARANCE: the polymer is cleared: renal/hepatic
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16
Q

Why can a polymer not diffuse through the barrier in lysosomotropic delivery

A

Because of its size and physicochemical properties polymer cannot cross cell barrier

17
Q

6 Advantages of PDC

A
  1. EPR effect
  2. Decreased toxicity so increased dose threshold
  3. Active tumour targeting if targeting moiety present
  4. Solubilisation of API (polymer helps solubilise)
  5. Prolonged circulation time because excretion is slowed down
  6. Overcomes some drug resistance mechanisms e.g. MDR because polymer masks drug
18
Q

Requirements for drug

A

Needs to be potent in relation to polymer carrying capacity

19
Q

Requirements for biodegradable linker

A
  • Suitable functional group that is stable during transport
  • Degradable within target environment to ensure minimal off target binding and ensure correct activity of drug
20
Q

Requirements of polymer

A
  • Non toxic, non immunogenic
  • Suitable for industrial scale manufacture
  • Biodegradable or if not then below renal threshold for elimination
  • Carrying capacity: needs to be able to carry multi drug molecules in single polymeric chain.
21
Q

Requirements for targeting group

A

Be specific for a target

22
Q

General toxicity considerations for PDC

A
  • Polymer has to be inert and non toxic
  • Ensure polymer is not immunogenic
  • Toxicity is affected by MW
  • Toxicity of conjugate may be different from toxicity of polymer alone
23
Q

Movantik

A
  • Only PDC on market
  • Contains PEGylated naloxone
  • Oral opioid antagonist derivative
  • Approved for treatment of opioid induced constipation
24
Q

Why does Movantik violate the rules for PDC

A

Violates general rules for PDC
- Has a non-biodegradable linker
- Oral whereas PDC normally given IV

25
Q

What is the dose of Movantik?

A

OD

26
Q

Movantik MoA

A

Antagonises morphine induced peripheral effects in GIT without affecting CNS effects

27
Q

Dextrin-2 sulphate

A
  • Polymeric drug
  • MW 25kg/mol
  • Tested intraperitoneally in AIDS patients
28
Q

What is Capaxone

A
  • Polymeric drug
  • Random copolymer of 4 amino acids
  • MW 5-11kg/mol
  • Administered s/c
  • Used for treatment of MS
29
Q

Capaxone MoA

A

Mimics myelin to slow down disease progression

30
Q

Passive tumour targeting

A

Responsible for the accumulation of polymer-drug conjugates in the tumour tissue

31
Q

Active tumour targeting

A

Responsible for accumulation of PDSC in tumour tissue due to:
- Polymer
- Drug
- Linker
- Targeting moiety

Ama - Part 4 PM4B (69 decks)

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