anti neoplastics 1 Flashcards
mechanism of resistance
- inc rate of DNA repair
- formation of trapping agent
- change in drug sensitivity to target enzyme
- decreased activation of prodrugs
5.inactivation of anticancer drugs
decreased drug accumulation
chemoherapy treatment strategies
- multi drug combo
- max individual dose
- avoid overlap in toxicities
- manage toxicities
alkylating agents mechanism of action
- interfere with DNA integrity and may induce apoptosis in :
rapidly proliferating tissues-alkylation occurs in lare G1 and S phases and express in G2
Non dividing cells-cells blocked in G1/S interface
cell death relies on -> activation of DNA repair system creates DNA strand breaks by repair enzymes-> triggers apoptotic response
resistance to alkylating agents
- dec cell permeability to drug
- inc detoxification capability
- inc dna repair processes
- inc rate of metabolic degradation
- impaired apoptotic pathway
- defective checkpoint
alkylating toxicities
- bone marrow supression
- mucosal toxicity
- nausea/vomiting
- neurotoxicity-altered mental state seizure
- extravasation from injection site:ulcerations
- pulmonary fibrosis
- veno occlusive disease o fliver-obstruction of small hepatic veins
- reproductive system toxicity
- leukemogenesis
- pregnancy-teratogenic
cyclophosphamide/ifosfamide
- cytotoxic metabolite
- metabolite activation via CYP2B6
- hydroycyclophsphamide->aldophosphamide->phosphamide mustard->acrolein
cyclophosphamide/ifosfamide resistance
- aldehyde dehydrogenase- inc rates of metabolic degradation to inactivate keto and carboxy metabolites
- gluthathione transferases-detoxification of most alkylating intermediates
cyclophosphamide/ifosfamide therapeutic uses
cyclophosphamide;
- broad use-solid tumors,hematologic cancers
- potent immunosuppressive properties-treatment of autoimmune disorders (RA, nepritic syndrome, wegeners granulomatosis)
Ifosphamide; testicular cancer lymphomas bone tissue sarcoma bladder cervical ovarian lung cancer
cyclophosphamide toxicity
-hemorrhagic cystitis(acrolein)
-IV hydration+mesna conjugates/inactivates
acrolein->dec in toxicity
-CHF; nephrotoxicity, bladder cancer
-SIADH reported
platinum analog
Cisplatin, carboplatin, oxaliplatin
IV,poor CNS penetration, renal clearence
dose adjustment in renal impairment
platinum analog mechanism
- passive diffusion and CU active transporter
- activation
- reacting with purine (mostly G) on same or neighboring DNA aka dna cross linking
- cell cycle arrest
- strand break
- apoptosis
- replication inhibition
resistance to platinum analogs
decreased uptake;
-CTR1 copper transporter down regulation and decreased expression= decreased uptake. predominant mechanism of resistance
efflux;
ATP7A and ATO7B transporters remove excess copper from cell
inactivation; inc intracellular levels of 1.gluthione 2.metallothionein 3.other sulfhydryls...molecules bind and inactivate drugs
repair; overexpression of 1.nuceotide excision repair 2. base excision repair 3.mismatch repair
cross resistance may occur btw cisplatin and carboplatin
platinum analogs therapeutic effect
cisplatin
major anti tumor activity broad range solid tumors
carboplatin
broad spectrum activity against a wide rage of solid tumors
oxaliplatin
colorectal and gastic cancer
first line therapy in advanced colorectal cancer
toxicities of platinum analogs
cisplatin vomiting myelosuppression ototoxicity nephrotoxicity-dose dependent- vigorous chloride dieursis with saline and diuretic (furosemide or mannitol)
carboplatin
less severe myleosuppression but similar toxicity ro cisplatin
oxiplatin
similar to cisplatin but less peripheral neuropathy(exacerbated by cold)
ALL have leukemia and pulmonary fibrosis month-years later
platinum drug interaction
platinum analog+taxane
platinum analog->dec taxane clearance=
administer taxane before platinum
folate antagonist methotrexate
- narrow therapeutic window. drugs that displace methotrxate from albumin inc risk of severe myelosuppression
- poor CSF distribution, distributes in body water
- enter cell via folate transporter
methotrexate mode of action
- dec fh4 synthesis->dec purine nucleotides and thymidylate
- ultimately impair synthesis of purine nucleotides and thymidylate
- dec dna and RNA synthesis
- induces p53 and cell cyle arrest
mtx resistance
- impaired transport into cell
- dec ability to synthesize methotrexate polyglutamates
- inc conc. of DHFR
- inc expression of drug efflux
- production of altered DHFR with reduced affinity for mtx
mtx therapy
- broad spectrum liquid and solid tumor
- ALL
- methotrexate can be curative
- immunosuppressant
- abortifacient
MTX toxicity
acute: -myleosuppression rash neurotoxicity-seizure,coma pneumonitis mucositis
delayed nephrotoxicity impaired fertility oppurtunisitc infection lymphome encephalopathy hepatoxicity
-leucovorin..converted to methylene FH4-> rescue from toxicity but does not reverse neurotoxicity