Chemo III: Antitumor drugs Flashcards
Doxorubicin:
Cycle cycle specific?
What is its mechanism of action?
What is an important characteristic factor of this drug?
Cell cycle NON-specific
Intercalates between DNA strands (sugar part of molecule binds to the phosphate backbone) –> introducing DNA protein breaks in the strand
RED in solution
What drug in another class shares similar MOA to donamycin and doxyrubicin?
Etoposide; in relation with topoisomerases
What is the important function of topoisomerases?
What is the role between topo I and topo II? How can drugs interfere with this process?
Topoisomerase resolve conformation and topological changes in the DNA –> release stress and supercoiling
Topo I: introduces transient protein bridged DNA breaks in one strand of the DNA –> drug-DNA-enzyme complex, thus arrests repair at the replication fork –> single strand break
Topo II: binds both strands-introduces transient protein bridged DNS breaks in BOTH strands of the DNA –> drugs binds TPII –> ds-break
–> total cell death
intercalating and non-intercalating topo II inhibitors and tubulin inhibitors (vinca alkaloids) are all cross-resistant due to _____
How can resistance be reversed? (2)
Have these methods proved to be beneficial?
intercalating and non-intercalating topo II inhibitors and tubulin inhibitors (vinca alkaloids) are all cross-resistant due to MULTI-DRUG RESISTANCE
P-glycoprotein is a memebrane bound efflux pump that confers resistance - giving these drugs as continuous infusions may downregulate the P-glycoprotein and reverse resistance
Giving drugs that block the efflux pump (quinine, verapamil, cyclosporine) may also reverse resistance and enhance efficacy of drug
This has NOT made a huge impact on response rate because there are other mxns of resistance
What are some anti-cancer drugs (7 categories) and other agents (7) to which MDR cells are resistant to:
Anti-cancer:
Vinca alkaloids (vinblastine, vincristine), anthracyclines (daunorubicin, doxorubicin, mitroxantrone), Epipodophyllotoxins (etoposide, teniposide), mitomycin C, actinomycin D, taxol, topotecan
Other agents:
Colchicine, puromycin, podophyllotoxin, ethidium bromoide, emetine, gramicidin D, valinomycin
Doxorubicin:
Cell cycle specific?
MOA?
When is dose reduction required?
AEs (4)
Dose limiting factor?
What is one extra exam that is required prior to giving therapy and why?
Cel cycle NON-SPECIFIC
Intercalates into DNA and inhibits TOPO II –> DS-DNA breaks
Dose reduction: presence of jaundice, because it is excreted as a thiol adduct into bile
AEs: N/V, hair loss, stomatitis
Dose-limitaiton: myelosuppression
MUST OBTAIN AN EJECTION FRACTION –> there is cumulative toxicity as cardiomyopathy
What is cumulative toxicity?
What limitation does this have on doseage?
what is an example of cumulative toxicity?
The higher the drug you’re given over time, the greater irreversible damage to an organ there will be
With repeated administratinos of drug, the damage accumulates and after a certain dose is reached, the total damage results in organ dysfunction
–> total LIFETIME dose!
Ex) doxorubicin – cumulative toxicity to heart; after about 550 mg/M2 total dose ~ 10% of patients will have CHF
What is schedule dependent toxicity?
what is an example?
The toxicity depends on the length of the infusion of hte dose of the drug
ex) doxorubicin
probability of developing CHF is a function of the length of the infusion of the dose – a 96 hour infusion of drug is associated with much LESS cardiotoxicity than the same dose administered over 30 minutes
What is schedule independent cytotoxicity?
example:
Altering the schedule of administration DOES NOT alter the ANTI-TUMOR effect of the drug
example) doxorubicin effect on tumor is NOT dependend on how the dose is administered (30 mins vs 96 hour –>same cytotoxic effect)
What cumulative toxicity does doxorubicin display?
What is the maximum life dose?
This toxicity is seen most w/what type of schedule?
What could be done to prevent this toxicity? (2)
Doxorubicin cumulative toxicity is cardiomyopathy
Max life time dose: 400 mg/M^2
Cardiac toxicity is SCHEDULE DEPENDENT –>
shorter infusion times = more cardiac toxic than longer infusion times
You can either:
- Pretreat with dexraxoxane; an iron chelator - thought that free radicals made by the drug complexes with iron –> cardiac tox
- SInce anti-tumor effect is schedule INDEPENDENT (same effect whether given long or short infusion times) and the toxicity effect is schedule DEPENDENT (greater toxicity with shorter infusion times) , increasing infusion times could decrease the cardiotox – [free radical] won’t peak and cause cardiac damage as fast
How does Irinotecan work?
What is its indication?
Cell cycle NON-specific
Irinotecan is a topoisomerase I inhibitor
BIOACTIVATION IS NECESSARY:
Parent compound: CPT 11 (some activity) –> carboxylesterase converts to 7-ethyl-10-hydroxycamptothecin (SN38) –> active compound hat produces single strand breaks
Colon cancer (second line to cisplatin)
Irinotecan:
What is its dose limiting factor?
AEs (6)..are there specific treatments that may help alleviate?
When is dose reduction necessary?
What is significant about its metabolism and possible effects with certain disease?
Dose-limiting factor: myelosuppression
AEs: N/V, hair loss, stomatitis, early cholinergic diarrhea (tx atropine), late secretory diarrhea (tx imodium + hydration)
Dose reduction with w/jaundice (significant hepatic metabolism)
UGTIAI is responsible for the clearance by glucuronidation of drug and bilirubin
genetic polymorphisms in the UGT1A1 promoter that lead to enz underexpression –> impairment of bilirubin metabolism via reduced glucuronidation (GILBERTS syndrome) –>irinotecan toxicity and cause severe myelosuppression/neutropenia
Bleomycin:
how does it function?
What’s its indication?
Damages DNA, mxn UNKNOWN - free radical damage to DNA –> single and DS breaks…bleomycin-iron fomr
Cell cycle SPECIFIC (G2-M phase)
FOR: part of BET treatment for testicular cancer; hodgkins
When is a dose reduction indicated for bleomycin?
AEs (2)
Dose limiting?
Cumulative toxicty?
Dose reduction necessary in pt with renal insufficience since 50% of the drug is excreted in the urine
AEs- associated with lung and skin
Hyperpigmentation of vein if given periphery (gets better with time) due to there being bleomycin hydrolase in the liver and kidney that inactivase the drug but this enzyme NOT at lungs and skin!
Lung - SOB, cough, interstitial fibrosis, restricting ventilation
Dose-limiting: pulmonary toxicity (CUMULATIVE TOXICITY)
What is important to monitor when giving bleomycin?
What should be avoided when administrating bleomycin?
MONITOR PULMONARY FUNCTION!!
Obtain diffuse capacity of carbon-monoxide DLCO at base line, before administration of therapy
AVOID admin of high oxygen concentration, could lead to ARDS
couldn’t detox lungs, and high amounts of oxygen could lead to increas amounts of free radicals
