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Oncology Exam 3 > Anti-Metabolites Lapinsky > Flashcards

Anti-Metabolites Lapinsky Flashcards

1
Q

What type of drugs are the anti metabolites?

A

CCS drugs (S Phase)

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2
Q

What is the rate limiting step in overall DNA synthesis?

A

Thymidylate Synthase

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3
Q

What enzyme does methotrexate inhibit?

A

DHFR

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4
Q

What is the active metabolite of 5-FU?

A

5F-dUMP

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5
Q

What does 5F-dUMP function as?

A

Irreversible, covalent inhibitor of Thymidylate Synthase

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6
Q

Why can’t cancer cells tell the difference between dUMP and 5-FdUMP?

A

The size of F and H are roughly the same

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7
Q

The bond strength of C5-F is __C5-H

A

> >

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8
Q

What does the natural mechanism of Thymidylate synthase involve?

A

Enzyme breaking the C5-H bond

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9
Q

What bond can Thymidylate synthase (TS) not break?

A

C5-F

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10
Q

When should you give leucovorin with 5-FU?

A

Give 60 mins before 5-FU

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11
Q

What is the cofactor needed for TS to work?

A

Business folate (5,10-CH2THF)

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12
Q

What is leucovorin a precursor of?

A

Business folate

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13
Q

What is needed for TS and 5-FdUMP to work?

A

Business folate

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14
Q

5-FU drug action= cancer cells are said to die a “__________”

A

Thymine-less death

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15
Q

How is capecitabine taken?

A

Orally

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16
Q

How is Floxuridine and 5-Fluorouracil taken?

A

By injection

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17
Q

True or false: normal healthy cells have more thymidine phosphorylase than cancer cells

A

False

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18
Q

What does capecitabine display better than floxuridine and 5-fluorouracil?

A

Selective toxicity

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19
Q

What enzyme is responsible for carrying out the natural detoxifying metabolite of fluoro-pyrimidine?

A

DihydroPyrimidine Dehydrogenase (DPD)

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20
Q

What gene codes for DPD?

A

DPYD

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21
Q

What can patients experience if they don’t have the DPYD gene?

A

5-FdUMP mediated toxicity (myelosuppression)

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22
Q

What does methotrexate antagonize or block the actions of?

A

Folic acid (folate)

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23
Q

Folic acid derivatives are generally used in what kind of reactions?

A

One carbon transfer reactions

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24
Q

What is folic acids primary function in the body?

A

Acts as a cofactor for enzymes that catalyze one carbon transfer reactions

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25
Q

What 2 amino acids can act as anti-folates and inhibit protein and enzyme synthesis?

A
  1. Serine
  2. Methionine
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26
Q

What 2 things can act as anti-folates and inhibit DNA and RNA synthesis and repair?

A
  1. Thymidine
  2. Purines (A,G)
27
Q

The anti folates work by targeting and inhibiting what enzyme?

A

DHFR (dihydrofolate reductase)

28
Q

Anti folates are cytotoxic during what phase?

A

S phase (DNA and RNA synthesis)

29
Q

What can leucovorin also be referred to as?

A

Folinic acid

30
Q

True or False: Leucovorin can go to a business folate only if DHFR is intact

A

False

31
Q

Methotrexate binds to DHFR _____ times stronger than the natural substrates folic acid and dihydrofolate

A

1,000

32
Q

What 3 things is DHFR involved in the synthesis of?

A
  1. dTMP
  2. Purines and pyrimidines
  3. Select amino acids
33
Q

High dose methotrexate therapy is traditionally followed by what?

A

Leucovorin rescue

34
Q

What does leucovorin get directly converted to?

A

Tetrahydrofolate (THF)

35
Q

Methotrexate kills via what theory?

A

Rate theory

36
Q

True or false: leucovorin does not show selectivity in its “rescue” properties

A

True

37
Q

What cannot be used as rescue therapy after high dose methotrexate treatment?

A

Folic acid

38
Q

What can be used in accidental cases of methotrexate overdoses?

A

Leucovorin

39
Q

The more biologically active enantiomer of leucovorin

A

Levoleucovorin

40
Q

True or false: methotrexate doses used for treating cancer are much lower than those used for RA or psoriasis

A

False

41
Q

What is the frequency of MTX doses for treating RA or psoriasis given?

A

Weekly

42
Q

How is MTX given in order to treat cancer?

A

Intrathecally

43
Q

What formulation should you use when administering MTX?

A

Preservative free

44
Q

What are two ADRs for MTX?

A
  1. Nephrotoxicity
  2. Crystalluria
45
Q

Where are high dose anti folates generally cleared?

A

In the kidneys

46
Q

What 2 things must be given to patients that are on high dose MTX therapy?

A
  1. Hydration
  2. IV sodium bicarbonate
47
Q

The unionized form of MTX has a ___ H2O solubility

A

Decrease

48
Q

The unionized form of MTX has a ___ risk for MTX crystalluria

A

Increased

49
Q

The ionized form of MTX has a ___ H2O solubility

A

Increased

50
Q

The ionized form of MTX has a ___ risk for MTX crystalluria

A

Decreased

51
Q

What is the MTX antidote last resort?

A

Glucarpidase

52
Q

Glucarpidase

A

VORAXAZE

53
Q

How is Voraxaze cleared?

A

By the liver

54
Q

What is the disadvantage to VORAXAZE?

A

Expensive

55
Q

What are 5 drug interactions associated with high dose methotrexate?

A
  1. High dose Salicylate NSAIDs
  2. PPIs
  3. Sulfonamides
  4. Beta lactam antibiotics
  5. Probenacid
56
Q

Organic acids can compete with MTX in the kidney for what?

A

Organic Acid Transporter Proteins (OATs)

57
Q

What can the organic acid drugs do to the clearance of MTX?

A

Decrease the renal clearance of MTX and increase MTX nephrotoxicity

58
Q

What drug is clinically indicated for the treatment of mesothelioma?

A

Pemetrexed

59
Q

What 3 enzymes does pemetrexed inhibit?

A
  1. TS
  2. DHFR
  3. Garftase
60
Q

What 2 things should be supplemented with pemetrexed?

A
  1. Vitamin b12
  2. Folic acid
61
Q

What should be given in the day prior, the day of, and the day after the use of pemetrexed?

A

Dexamethasone

62
Q

Pemetrexed

A

Alimta

63
Q

What drug is traditionally the top selling anti-folate?

A

Pemetrexed

Oncology Exam 3 (6 decks)

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