Therapeutics Exam 1 (Wendt and Dykhous) PT. 2 Flashcards
(200 cards)
Uridine Analogs:
FdUMP mimics _____ and will bind to the active site of _________
mimics dUMP (hint the F is the fluorouracil that is screws everything up for DNA)
active site of: thymidylate synthase
Uridine Analogs:
FdUMP will form a ternary complex with _____ and ______
enzyme (synthase) and reduced folate cofactor (aka the methyl donor!!)
Uridine Analogs:
when FdUMP is in the ternary complex – the reaction cannot go to completion because why?
the F present (is usually an H) prevents the reaction to completing and letting the enzyme detach – enzyme is trapped!
Uridine Analogs:
5-FU leads to _____ depletion and leads to the inhibition of DNA synthesis (via a “_______ death”)
TMP depletion
thymineless death
Uridine Analogs:
5-FU is also converted to F-UTP and will affect _______
RNA processin and function
5-FU resistance can occur by what 2 mechanisms?
downregulation of activating enzymes
upregulation of thymidylate synthase
Thymidine and 5-FU drug interaction:
5-FU THEN thymidine = “_____” cytotoxic effect
Thymidine then 5-FU = “______” cytotoxic effect
then thymidine: is rescuing
thymidine 1st = enhances effect (giving this first will cause the cell to down regulate thymidine synthase!!)
the drug _____ can be given with 5-FU and increase the efficacy by increasing the stability of the synthase complex
Leucovorate
Leucovorate is a stable _____ cofactor and gets converted to _______ intracellularly
folate; tetrahydrofolate
______ breaks down 5-FU (~5% of the population has a polymorphism and has a deficiency of this enzyme)
*deficiency of this enzyme can lead to a life threatening 5-FU
DPD (dihydropyrimidine dehydrogenase)
who is FUdR (fluroreoxyuridine) different than 5-FU
FUdR is the deoxyribonucleoSIDE of 5-FU (aka FUdR has a sugar)
Capecitabine is a orally active prodrug of _____
5-FU
benefit of Capectiabine being a prodrug of 5-FU
longer 1/2 life!/can build up in tissues more
prodrug strategy generates higher levels of 5-FU selectively w/in some tumors
Cytosine analogs:
primarily inhibit _______
DNA synthesis
what bases are pyrimidines?
C & T
what drugs are cytosine analogs?
Cytosine arabinoside…
Gemcitabine
Cytosine arabinoside
is so structurally similar to deoxycytidine but the _______ makes it wack
B-OH at sugar 2’ (sugar is inverted somewhere)
Cytosine arabinoside
gets converted to _____ intracellularly and then acts as a competitive inhibitor to _________
Ara-CTP
DNA polymerase alpha
(Ara-CTP will also get incorporated into DNA and make it wack)
_________ will convert cytosine arabinoside to non-toxic uracil arbinoside
cytidine deaminase
Cytosine arabinoside:
cytidine deaminase is low in the ______ therefore this drug is good to use for these types of cancer: ______ and ______
CNS!!!
meningeal leukemia and lymphoma (aka cancers in lining of brain and spinal cord)
resistance mechanisms to cytosine arabinoside?
downregulation of deoxycytidine kinase (? - apparently an activating enzyme..)
upregulation of cytidine deaminase
downregulation of transport to move drug into cells
Gemcitabine:
gets phosphorylated to ____ and ____ intracellularly
______ will inhibit ribonucleotide reductase (inhibits DNA synthesis)
___ gets incorporated in DNA and halts further chain elongation
dFdCDP; dFdCTP
dFdCDP
dFdCTP
what drugs are used to stop purine biosynthesis
6-mercaptopurine
6-thioguanine
what drugs are used to stop DNA and RNA incorporation of purine analogs
fludarabine
Nelarabine
Cladribine