Sweatman Cytotoxic Chemotherapy Agents Flashcards
3 majors MOA’s through which Chemotherapy drugs work
- Action on DNA
- Action on Mitotic Spindle
- Hormonal Agents
Action on DNA can be broken up into (2)
- damage to DNA
2. inhibition of DNA synthesis
Action on mittotic spindle can be further subdivided into (1)
Microtubule Inhibition
Hormonal agents can be broken up into (2)
- agonists (prednisone)
2. antagonists (tamoxifen)
Most toxic pharmaceutic agents
anti-cancer drugs
DNA damage can be subdivided into 2 types
- alkylation (cyclophosphamide)
2. free radical formation (doxorubicin)
Inhibition of DNA synthesis or function can be divided into two categories
- Antimetabolites (methotexate)
2. Topoisomerase (etoposide)
Anti-cancer drugs that target cells undergoing cycling
Cell-Cycle Specific drugs (CCS)
*cannot kill drugs that are in the G0 phase
Anti-Cancer drugs that kill tumor cells in both the cycling and resting phases
Cell-Cycle Non-Specific (CCNS)
*can kill cells which are in G0 phase
CCS drugs are particularly effective when
larger proportion of cells within a tumor are proliferating (cycling)
Fraction of cells within a tumor hat are actively dividing
Growth fraction
Log-Kill hypothesis
Chemotherapeutic agents work via First order kinetics–> a constant proportion of cells are killed per log-dose, NOT a constant NUMBER of cells.
1 log dose will decrease the tumor cell population by
one order of magnitiude (90%)
rescue therapy
administration of endogenous metabolites to counteract the effects of anticancer drugs on normal tissues
Vesicant example
mechloethamine (an alkylating agent)
Vesicant definition
drugs that causes blisters when it contacts tissues–> damaging to the veins if administered in high enough concentrations into small vessels…
M phase inhibitors
Vinca Alkyloids
G2 phase inihibotor
Bleomycin
and podophyllotoxins
G2 and S phase inhibitors
Podophyllotoxins
S phase inhibitors
Methotrexate
and Podophyllotoxins
Resistance mechanism especially important for alkylating agents
Increased DNA repair
MOR important to Bleomycin, CIsplatin, and Anthracyclins
*all of which form electrophillic species
Formation of trapping agents
–>increase production of thiol trapping agents which interact with these drugs
MOR important to Methotexate
Change in target enzyme
and Increased synthesis of enzyme
*DHFR
examples of purine antimetabolites
mercaptopurine
thioguanine
pyrimidine antimetabolites
cytarabine
flourouracil
MOR involving purine/pyrimidine antimetabolites
> decreased activity of tumor cell enzymes to CONVERT PRODUGS INTO CYTOTOXIC METABOLITES
another MOR involving puring/pyrimidine antimetabolites
Increased inactivation of these prodrugs results in decreased effect
MOR involving many Anti-cancer drugs
decreased drug accumulation/increased efflux
> upregulation of MDR1 (pGP)
Alkylating agents are CCS or CCNS?
CCNS
Alkylating agents MOA
–>form reactive molecular species that alkylate nucleophillic groups on DNA, particularly N-7 position of guanine–>leads to CROSS LINKING, ABNORMAL BASE PAIRING AND DNA BREAKAGE
RESISTANCE TO ALKYLATING AGENTS OCCURS VIA
INCREASED DNA REPAIR MECHANISMS
DECREASED DRUG PERMEABILITY
PRODUCTION OF TRAPPING THIOLS
nitrogen mustards (alkylating agents)
cyclophosphamide
mechlorethamine (a vesicant)
CYP450 break down of cyclophosphamide results in
acrolein ( a breakdown product)
CYP450 break down is required for anti-tumor capabilities
Hemorrhagic Cystitis is brought on by ________ and releived by ____________.
acrolein build up following cyclophosphamide tx
mesna and intense hydration