Anti-cancer drugs Flashcards
Log Kill hypothesis?
Action of chemo follows 1st order kinetics - a given dose of chemo kills a constant FRACTION of available tumor cells. Repeated doses of chemo agents are needed to be administered.
[administer chemo to prevent tumor cell number to reach 10^9 - 10^12]
Common adverse effects of chemo tx?
- Nausea and vomiting (treated with 5HT3 blockers [ex. ondansetron] and NK1 inhibitors).
- Stomatitis
- Alopecia
- Myelosuppression (Filgrastim [G-CSF stimulator] is used to treat neutropenia).
Categorize chemotherapeutic agents into strong, moderate and mild myelosuppression?
Strong - Cytarabine, alkylating agents, doxorubicin, Daunorubicin, Vinblastin
Moderate - Carboplatin, methotrexate, 5-FU
Mild - Bleomycin, Vincristine, asparaginase [use in pt who is already at risk of developing myelosuppression]
Specific AE of Doxorubicin, Cyclophosphamide, Ifosphamide, bleomycin?
Doxorubicin - cardiotoxicity
Cyclophosphamide and Ifosphamide - hemorrhagic cystitis
Bleomycin - pulmonary fibrosis
Use of what agents most commonly leads to treatment-induced neoplasms?
alkylating agents
What drugs can be used to rescue bone marrow, reduce hemorrhagic cystitis, reduce anthracycline-induced cardiotoxicity, reverse neutropenia and reduce renal toxicity caused by cisplatin?
- Leucovorin rescues bone marrow from methotrexate.
- Mesna reduces hemorrhagic cystitis caused by cyclophosphamide and ifosfamide.
- Dexrazoxane reduces anthracycline-induced cardiotoxicity.
- Filgrastim reverses neutropenia caused by many anticancer agents.
- Amifostine is a cytoprotective agent that reduces renal toxicity caused by cisplatin.
Primary vs acquired resistance?
Primary - no response to drug on 1st exposure
Acquired - single drug resistance (increased expression of one or more genes) or multidrug resistance (resistance emerges to several different drugs after exposure to a single agent)
cell cycle specific vs cell cycle nonspecific drugs?
cell cycle specific - drug that exert action ONLY on cells going through cell cycle [hematologic malignancies - high growth fraction only]
cell cycle non-specific - can kill tumor cells whether they are cycling through cell cycle or resting in the Go compartment [hematological and solid tumors - low or high growth-fraction]
Methotrexate?
folate analog active against cells in S phase of cell cycle (DNA replication)
MTX to MTX polyglutamate intracellularly – MTX polyglutamate then binds and inhibits dihydrofolate reductase (DHFR) enzyme. Inhibiting this enzyme inhibits synthesis of THF involved in de novo synthesis of Deoxythymidylate nucleotides (inhibition DNA synthesis) and Purine nucleotides (inhibition DNA and RNA synthesis). No available pyrimidine or purine nucleotides are present to form the DNA.
AE:
• Common: Stomatitis, mucositis, myelosuppression (drug also affects normal cells therefore administer with Leucovorin), alopecia, nausea, vomiting.
• Hepatic fibrosis and cirrhosis.
• Pneumonitis.
• Neurologic Toxicities (with IT administration).
• Renal Damage: Uncommon. Complication of high-dose methotrexate.(MTX precipitates in the tubular lumen causing damage)
Leucovorin?
Leucovorin is a folinic acid derivative that is used in combination with methotrexate to revive some folate in the normal tissues. Leucovorin circumvents the inhibition of DHFR. [Antidote to drugs that decrease levels of folic acid]
6-Mercaptopurine
Purine analog of Hypoxanthine
- 6-MP to TIMP via HGPRT (salvage pathway)
- Thio-IMP inhibits first step of de novo purine ring biosynthesis [PRPP to IMP]
- Thio-IMP also blocks formation of AMP and GMP from IMP [IMP to AMP and GMP]
- TIMP can also be converted to TGTP incorporating in to RNA leading to dysfunctional RNA, OR TdGTP incorporating in to DNA leading to dysfunction
Clinical Application - ALL (CHILDHOOD acute leukemia)
AE - nausea, vomiting, diarrhea (b/c chemo drugs are toxic to rapidly dividing cells in the mucosa/GI tract), hepatotoxicity, bone marrow suppression
6-mercaptopurine metabolism?
6-MP to 6-methylmercaptopurine via thiopurine methyltransferase
*can be altered due to genetic deficiency (1:300 people have mutant alleles) of the enzymes, therefore you don’t want accumulation of 6-MP therefore decrease 6-MP dose
6-MP to oxidized metabolite via xanthine oxidase
- if pt is on allopurinol, it will inhibit the xanthine oxidase enzyme therefore a reduced 6-MP dose is required b/c you do not want 6-MP to accumulate to toxic levels
- *give allopurinol with 6-MP due to increased breakdown of cells/RNA/DNA that mostly end up producing uric acid
6-Thioguanine
Purine analog similar to 6-MP
- 6-TG to TGMP via HGPRT
- TGMP to TGTP and TdGTP
- TGMP inhibits amidotransferase (converst PRPP to IMP) and GMP to GDP conversion
- TGTP can be incorporated to RNA making it unstable
- TdGTP can be incorporated in to DNA making it unstable
Clinical Application - Non-lymphocytic leukemias
AE - nausea, vomiting, diarrhea, hepatotoxicity, bone marrow suppression
- unlike 6-MP Allopurinol does not affect metabolite production therefore reduction is not required (deamination no oxidation)
- genetic deficiency of thiopurine methyltransferase causing an increase in 6-TG concentration and therefore you require a decreased dose of 6-TG [very similar to 6-MP]
5-fluorouracil?
Pyrimidine analog
- 5-FU to 5-FdUMP via Dihydropyrimidine dehydrogenase (DPD)
- 5-FdUMP inhibits thymidylate synthase – thereby inhibiting DNA synthesis [dUMP can’t be converted to dTMP]
- 5-FU is also converted to 5-FUTP and incorporated into RNA interfering with RNA processing and function
*Leucovorin administration would produce N5-N10-methylene-THF which would potentiate the inhibition of the thymidylate synthase - enhance cytotoxicity in the tumor cells (different from its actions with methotrexate when it actually skips the inhibition and saves the cells)
Tx - colorectal cancer
AE - nausea, vomiting, alopecia, bone marrow, depression, HAND-FOOT SYNDROME (erythematous desquamation of palms and soles seen after extended infusion - location of the apocrine sweat glands)
*pts with partial or complete deficiency of DPD may lead to severe toxicity (myelosuppression, neurotoxicity, life-threatening diarrhea)
Capecitabine?
Pyrimidine analog
Oral prodrug that is converted to 5-FU via 3 enzymatic steps [1st step occurs in liver, last step occurs in tumor when it is catalyzed by thymidine phosphorylase - this enzyme is in much higher concentration in tumor cells than normal cells]
*used in management of metaststic colorectal and breast cancer due to increased concentration of the enzyme
AE - diarrhea, hand-food syndrome, myelosupression, etc (less toxic compared to 5-FU)
Cytarabine?
Deoxycytidine analog
Cytarabine to cytarabine triphoshate which..
- competitively inhibits DNA polymerase-a (blocks DNA synthesis)
- competitive inhibits DNA polymerase-B (blocks DNA repair)
- incorporated into RNA and DNA leading to interference with chain elongation and defective ligation of fragments of newly synthesized DNA
Tx - hematologic malignancies - NOT active against solid tumors
AE - Ocular toxicity, cerebellar toxicity and peripheral toxicity, then myelosupression, mucositis, nausea, vomiting
Gemicitabine?
Deoxycytidine analog
Phosphorylated to nucleoside di and triphosphate which leads to inhibition of DNA synthesis. Inhibition causes ribonucleotide reductase inhibition via diphosphate and chain termination via gemcitabine triphosphate incorporation.
AE - flu-like syndrome, nausea, vomiting, myelosuppression (neutropenia), renal microangiopathy syndromes, HUS and TTP (rare)
Broad-spectrum activity against solid tumors as well as hematologic malignancies (ex. non-hodgkin’s lymphoma)
Vinca alkaloids?
Microtubule inhibitors
Metabolized in the liver via P450, excreted in the feces
MOA - alkaloids bind B-tubulin disrupting assembly of microtubules therefore mitotic spindles (why they are active with cells in cell cycle). Inhibiting microtubules also prevents movement phagocytosis and axonal transport.
AE - neurotoxiciy (esp peripheral toxicity)
Vinblastine?
Vinca alkaloid (microtubule inhibitor)
Use for: Hodgkin’s and non-hodgkin’s lymphomas, breast cancer and germ cell cancer
AE - bone marrow suppression, alopecia, peripheral neuropathy, nausea and vomiting, potent vesicant (local tissue destruction therefore administer with extra are) [MYELOSUPPRESSION!!!]
Vincristine?
Vinca alkaloid (microtubule inhibitor)
Use for hematologic malignancies as well as PEDIATRIC TUMORS (rhabdomyosarcoma, neuroblastoma, Wilm’s tumor)
AE - neurotoxicity WITH peripheral neuropathy, paralytic ileus, optic atrophy, MILD myelosuppression, alopecia, SIADH (known mechanism) [NEUROPATHY!!!]
Taxans?
Microtubule inhibitors - Paclitaxel and Docetaxel
Metabolized in liver via P45- system and excreted via hepatobiliary route
MOA - binds B-tubulin at site different from vinca alkaloids promoting microtubule polymerization and INHIBIT DEPOLYMERIZATION leading to cell damage, cell arrest and cell death
Paclitaxel?
Taxans (Microtubule inhibitors)
Used against SOLID TUMORS
AE - HSN rxn, myelosuppression, peripheral neuropathy, alopecia
HSN rxn is reduced by premedication with dexamethazone, diphenhydramine and H2 BLOCKER (Ranitidine).
Abraxane
Albumin bound form of PACLITAXEL that DOES NOT cause HSN rxn that does not require premedication. It also causes less myelosuppression than traditional paclitaxel.
Docetaxel
Taxans (Microtubule inhibitors)
Used as 2nd line therapy for advanced breast cancer and NSCLC as well as solid tumors.
AE - myelosuppression, FLUID RETENTION, NEUROTOXICITY (not as frequent as Paclitaxel), mucositis, alopecia, HSN
Pre-treat with Dexamethasone to prevent fluid retention.
Epipodophyllotoxins?
Etoposide and Teniposide
Inhibit topoisomerase II resulting in DNA damage through strand breakage by blocking cells in late S-G2 phase.
Etoposide - used for testicular cancer and SCLC
Teniposide - used for refractory childhood ALL
AE - nausea, vomiting, alopecia, myelosuppression
*associated with increased risk of secondary tumors
Camptothecins?
Topotecan and Irinotecan
Inhibits activity of topoisomerase I causing DNA damage @ 2-G2