Onc Pharma Flashcards
Polyfunctional alkylating agents
Break H-bonding in DNA and then erroneously cross-link DNA, most mutagenic CTX
- Busulfan: CML / Myeloablation. SE: MS(Myelosuppression), Pulmonary fibrosis, hyperpigmentation.
- Mustards / Nitrosoureas (Carmustine, Lomustine, Semustine, Streptozocin): Require bioactivation and cross BBB, so used in brain tumors. SE: CNS toxicity
- Cyclophos / Ifos:
a. Cross-link at Guanine N7 site
b. Require bioactivation in liver via P450
c. Metabolized by kidneys into Acrolein –> cause uroepithelial necrosis —> Hemorrhagic cystitis –> prevented by Mesna. - Cis(renal)platin / Car(kan)boplatin
- Dacarbazine / Procarbazine
Amifostine
- Reduce the incidence of neutropenia-related fever and infection induced by alkylating agents 2. Decrease the cumulative nephrotoxicity associated with platinum-containing agents.
- Reduce the incidence of xerostomia by radiotherapy for head and neck cancer
Alkaloids
- Paclitaxel / Docetaxel: Prevent depolymerization in M phase and prevent Anaphase to occur. SE: Neuropathy.
- Vincristine / Vinblastine: bind b-tubulin and inhibit polymerization (M phase arrest). SE: Vinc; neuropathy. Vinblas; blasts bone marrow.
Topoisomerase II inhibitors
Etoposide / Tenoposide: Topoisomerase II inhibitors –> inc DNA degradation
(II sides)
Topoisomerase I inhibitors
Irinotecan / Topotecan: Topoisomerase I inhibitors –> inc DNA degradation.
(I CAN)
Antitumor Antibiotics
- Anthracyclins (Doxorubicin or Adriamycin/ Daunorubicin / Epirubicin / Idarubicin): generate free radicles –> interfere with DNA replication by breaking DNA —> Dilated cardiomyopathy –> CHF –> Dexrazoxane is used to prevent cardiotoxicity and is an iron chelating agent.
- Dactinomycin or Actinomycin D: intercalate in DNA grooves –> inhibit RNA polymerase attachment –> inhibit cell growth. Used in childhood tumors.
- Bleomycin / Mitomycin / Plicamycin: generate free radicles –> interfere with DNA replication by breaking DNA. The only one which is G2 specific. SE: Pulmonary fibrosis.
Antimetabolites (classification)
- Purine antagonists
- Pyrimidine antagonists
- Antifolic acid synthesis
- Amino acid synthesis antagonists.
- Purine antagonists
- Azathioprine / 6-Mercaptopurine (6MP) / 6-Thioguanine (6TG):
a. Purine (thiol) analogs –> Dec de novo purine synthesis.
b. Activated by HGPRT (Aza is converted to 6MP)
c. Is used to wean patients off steroids & to treat steroid-refractory chronic diseases.
d. Affect Liver and cause Myelosuppression. Aza and 6MP are metabolized by Xanthine oxidase; thus both have inc toxicity with Allopurinol or Febuxostat. - Cladribine (2CDA) / Fludarabine / Pentostatin:
a. Purine analogs —> break DNA strands and inhibit DNA polymerase
b. Rx for Hairy cell leukemia, SE: Nephro and Neurotoxicity
- Pyrimidine antagonists
- Fluorouracil (5-FU):
a. Pyrimidine analog bioactivated into 5-FUMP –> covalently i.e. irreversibly bonds with B9 (THF) –> this complex inhibits Thymi-dylate Synthase –> dec TMP –> dec DNA synthesis.
b. Myelosuppression which is not reversible by Leucovorin (Folinic acid), rather its cytotoxic effects are enhanced by folinic acid - Cytarabine (ARA-C) / Azacitidine:
a. pYrimidine analog –> inhibit DNA polymerase
b. SE: Pancytopenias
- Antifolic acid synthesis
Methotrexate (MTX):
a. B9 (DHF) analog —> competitively inhibits Dihydrofolate reductase —> dec THF production –> dec TMP production —> Dec DNA synthesis.
b. Myelosuppression which is reversible with Leucovorin (Folinic acid) i.e. Rescue. Hepatotoxicity, Pulmonary fibrosis, Mucositis
- Amino acid synthesis antagonists.
Azaserine
Log Kill / Fractional kill hypothesis
Defined chemo —> defined dose —> at defined day —> will kill a constant percentage or fraction of cancer cell population rather fix number.
1st order kinetics –> applied on tumors of high Ki67%, not on solid tumors
Rationale for chomo combination and to precent chemo resistance to develop
Drugs that don’t cause myelosuppression
Belo, Vinc , Cisplatin
Cytokines,
IL 2, IL 11, GCSF, GMSF,
a. Aldesleukin (IL-2) –> inc NK cells and lymphocyte diff –> Renal cell carcinoma and Metastatic melanoma
b. IL-11 –> inc platlet formation
c. Filgrastim GCSF —> granulocytes recovery
Which factor determines the upper limit of chemo tolerability
Bone marrow suppression