PHARMACOLOGY CANCER CHEMOTHERAPY

1. PHARMACOLOGY CANCER CHEMOTHERAPY Heny Ekowati Pharmacy Departement Faculty of Medicine and Health Sciences Unsoed-2013 heny240377@gmail.com

2. Cancer is many diseases – common feature: abnormal cell growth; Shift in control mechanisms for growth and differentiation; cancer cells infiltrate into organs; interfere with normal functioning; no single cure Cancer (Neoplastic Disease) Second leading cause of death in the US (500,000/yr) Males: lung; prostate; colon and rectum Females: lung; breast; colon and rectum; uterus

3. Types of Cancers Hematologic Malignancies Leukemias Lymphomas Hodgkin’s Disease Non-Hodgkin’s Lymphoma Solid Tumors Carcinomas Sarcomas

4. Hematologic Malignancies Tumors of blood forming organs and cells • Leukemias: Proliferation of immature progenitors which circulate in blood • Acute lymphocytic leukemia (ALL, BM lymphblasts) • Chronic lymphocytic leukemia (CLL- immature B cells) • Acute myelocytic leukemia (AML, BM myeloid cells) • Chronic myelocytic leukemia (CML, myeloid cells; Philadelphia chromosome) • Lymphomas: Lymph System • Hodgkin’s Disease: lymph nodes • Non-Hodgkin’s lymphoma: lymphocytes (CLL)

5. Solid Tumors Can occur in any organ or tissue; malignant (metastatic and invasive) • Carcinomas: Arises from epithelial cells; malignant by definition eg., squamous cell carcinoma (basal cells of skin); glandular epithelial cells of breast • Sarcomas: Cancer of connective or supportive tissue (bone, cartilage, fat, muscle, blood vessels) and soft tissue eg., osteogenic sarcoma (osteoblasts, chondroblasts, fibroblasts)

6. Cancer Chemotherapy I. Goal II. Selective Toxicity III. Immune System IV. Kinetics of killing

7. Goal • CCT: Kill as many tumors cells as possible without killing too many normal cells; tumor regression, increased patient survival time, alleviation of symptoms

8. Selective Toxicity • CCT: Only quantitative differences between normal and neoplastic cells; differences in growth rate treatment is nonselective

9. Immune System • CCT: Minimal immune response; tumors not recognized as different, can overwhelm immune system; effective CCT- need total cell kill since a single malignant cell can give rise to sufficient progeny to kill the host

10. Kinetics First order kinetics: each regimen of CT kills constant % (log kill) CCT: very effective treatment kills 99.9% cells (3 log kill) 1012 cells  109 cells

11. Tumor Cell Killing: First Order Kinetics 1012 Stationary phase Tumor burden 109 New steady state 106 Time

12. Total Tumor Burden (Size) - Clinical detectable tumor: 109 cells (1 cm); lethal tumors: 1012 cells - The larger the tumor the harder it is to kill -more difficult for drugs to penetrate (poor vascularization) -many cells not proliferating (less sensitive CCT) -increased incidence of metastasis -incr. time of CCT required  incr. toxicity tumor size susceptibility to CCT

13. Cell Cycle M (2%) G2 (20%) G1 (40%) S (40%) **CCT

14. Cell Cycle Phase Tumors: consist of heterogeneous populations of cells, some growing, some dormant; in different phases of cell cycle Phases of Cell Cycle • M (mitosis, 2%) – some CCT • G1 (gap 1, 40%) - determines length of cell cycle, varies: G0 - dormant cells, differentiation • S (DNA synthesis, 40%) – most susceptible phase for CCT • G2 (gap 2, 20%) – RNA and protein synthesis Ideal CCT: Kill all cancer cells Practical: Kill all growing cells

15. Cell cycle control

16. Cancer Chemotherapy Cell Cycle Specific Agents (self limiting) Antimetabolites Bleomycin peptide antibiotics Podophyllin alkaloids Vinca alkaloids Cell Cycle Nonspecific Agents Alkylating Agents Antibiotics (actinomycin) Cisplatin Nitrosoureas

17. Drug Resistance Mechanisms vary with drug Decreased drug uptake Increased drug inactivation Mutations in activating enzymes Increased drug extrusion Multidrug resistance (MDR) p-glycoprotein (p53)- transmembrane protein; grabs drug and effuses it (doxorubicin, actinomycin D, VCR, VBL, eptoposide, taxol, mithramycin); not routinely tested for

18. Host Determinants General health status of patients -ability to tolerate drugs and side effects -nutritional state -infections -renal and bm function Immune status -natural antitumor defense mechanisms (macrophages, T cells, NK cells) Site of Tumor and blood supply

19. General Considerations Cancer Chemotherapy Choice of Drug Depends on tumor type and location CCT Regimens: intermittent high dose therapy to permit normal cell recovery, tumor cells also recover Combination Chemotherapy Guidelines: select drugs with different mech. action and minimal overlapping toxicity Ex., adriamycin, cyclophosphamide, vincristine, prednisone (Lymp. Hodgkins) Ex., vincristine, methotrexate, 6-mercaptopurine, prednisone (acute childhood lymphoblastic leukemia)

20. Adjuvant Therapy Use drugs as adjuvants to surgery and radiation therapy Remove localized tumor, then use CCT to get rid of remaining tumor cells and any metastatic cells Immunotherapy – use drugs to nonspecifically stimulate immune system

21. Drug Toxicity Most CCT agents: therapeutic index = 1 (therapeutic dose = toxic dose) Cytotoxic agents- kill all rapidly growing cells, nonselective • Bone marrow • GI tract • Hair follicles • Tissues undergoing repair

22. Side Effects of Anticancer Drugs • Bone marrow Leukopenia, lymphopenia (infections); Imunosuppression, thrombocytopenia (hemmorhage), anemia • Digestive tract Oral and intestinal ulceration; vomiting and diarrhea • Hair follicles Alopecia • Tissues under- going repair Impaired wound healing • Tumor mass Hyperuricemia adenine + inosine = hypoxanthine HX X uric acid kidney damage XO mediated (allopurinol)

23. Cancer Chemotherapeutic Agents Inhibitors of DNA synthesis -Alkylating agents -Antifolates (MTX) -Antibiotics Antimetabolites -Purine analogs (6-MP, 6-TG) -Pyrimidine analogs (5-FU, Ara-CTP) Microtuble inhibitors -Vinca alkaloids -Paclitaxal (Taxol) and Docetaxel Chromatin function inhibitors -Podophyllotoxins (etoposide, teniposide) -Camptothecin

24. Alkylating Agents History: first used in WW I (1917) as nerve gas (nitrogen mustards); extremely irritant, vesicant, produced leukopenia, bm aplasia, GI ulceration; 1942: used clinically to treat lymphosarcoma Mechanism of Action: mono- and bifunctional; all contain highly reactive alkyl groups; form covalent bonds with nucleophilic groups which become alkylated; targets: amino acids, carboxyl, sulfhydryl and imidazole groups in proteins and nucleic acids

25. Mechanism of Action CH2-CH2-Cl CH2-CH2-Cl R-N R-N--------CH2 CH2-CH2-Cl CH2 (Immonium ion) CH2-CH2-Cl N-7 Guanine R-N-CH2-CH2+ (Carbonium ion) Alkylated DNA Immonium ion Carbonium ion Reaction with N7 guanine Cross-linked DNA

26. Mechanism of Action Results of DNA alkylation: cross linking strands, mutations, disruption of base pairing; depurination of DNA, strand breaks Alkylation inhibits a variety of biochemical events in nucleic acid and protein synthesis Evidence in mammalian cells: cytotoxicity at therapeutic levels due to inhibition of DNA synthesis Bi-functional: more toxic can cross link DNA Resistance: excision/DNA repair enzymes; get rid of alkylated DNA

27. Mechanism of Action Cell cycle nonspecific Can interact with DNA of resting (G0) and proliferating cells; more toxic to growing cells; dormant cells (G0) can repair alkylation damage Proliferation dependent Amount of damage dependent on growth fraction of tumor Drug resistance Decreased drug uptake Increased repair of drug defect Cross resistance between drugs

28. Classes of Alkylating Agents Nitrogen Mustards • Side effects: immunosuppression; acute nausea, vomiting; alopecia, amenorrhea; • Cyclophosphamide: Most commonly used; **immunosuppresion, • Others: • Mechlorethamine- 1st anticancer drug used • Chlorambucil • Melphalan (L-PAM)

29. Classes of Alkylating Agents Nitrosoureas • Very reactive chemically; Non cross-reactive (resistance) • Lipophilic: penetrate CNS • Examples: BCNU; CCNU; methyl-CCNU • Side effects: nausea, vomiting, BM depression (delayed leukopenia)

30. Classes of Alkylating Agents Streptozotocin Naturally occurring nitrosourea Antibiotic isolated from Streptomyces Specifically retained in b cells of pancreas Low bone marrow toxicity Severe nausea and vomiting, insulin shock Used for metastatic islet cell carcinoma

31. Classes of Alkylating Agents Methane sulfonate esters (Alkyl sulfonates) Busulfan (Myleran): bifunctional; less active than nitrogen mustards; very selective depression of BM granulocytes; used clinically for CGL Triazenes Dicarbazine (DTIC) – Structural analog of intermediate in purine synthesis; cytotoxicity due to alkylation; acute severe nausea and vomiting, BM depression used for malignant melanoma, Hodgkin’s diseases

32. Classes of Alkylating Agents Ethyleneimines (Aziridines) Contain 3-membered ethyleneimmonium rings Triethylenemelamine (TEM) Triethylenethiophosphamide (thiotepa) More reactive at acid pH BM depression Bladder cancer (direct installation)

34. Classes of Alkylating Agents Platinum VIIIb transition metal; cell cycle nonspecific; direct interaction with DNA; forms GpG adducts; cross links DNA, induces apoptosis Analogs: Cisplatin, carboplatin, oxaliplatin Toxicity: nephrotoxicity (limits use); GI**, ototoxicity (hearing loss), alopecia

37. Folic Acid Analogs-Antifolates Folic acid (FH2) -essential vitamin required in diet (spinach) -required for the transfer of 1-carbon (CH3) units during nucleic acid and protein synthesis FH2 FH4 (1 carbon unit acceptor, acts as a coenzyme) Methotrexate,Aminopterin, Amethoperin- analogs of FH2 DHFR MTX NADPH NADP

38. MethotrexateMechanism of Action -Competitive inhibitors of dihydrofolic acid reductase (DHFR) -Bind tightly to DHFR “pseudo-irreversible” -Inhibit all one carbon transfer reactions; involved in the synthesis of thymidylate (dTMP), purines, glycine and methionine; results in inhibition of DNA, RNA and protein synthesis -S phase specific

39. Cytotoxic Effects of Inhibiting DHFR Inhibition of thymidylate synthetase (dUMP dTMP) Inhibition of de novo purine synthesis: blocks two steps in pathway that require one carbon transfer reactions Inhibiton of protein synthesis: MET; SER GLY Inhibition of protein and RNA synthesis slows entry of cells into S phase- self limiting Mechanisms of cell killing: “ Thymineless Death”- depletion of thymidine and purines TS

40. Leucovorin Rescue MTX binds equally well to normal and tumor cell DHFR Selectively based on differences in growth fraction, transport rates, DHFR levels, DHFR synthesis rates, and folate coenzyme pool sizes MTX most effective against rapidly proliferating cells; use intermittent high dose therapy of short duration to kill tumor cells; rescue normal cells with leucovorin (citrovorum factor, folinic acid); transported into normal cells, converted into FH4, bypasses MTX block FH2 FH4 methylene-FH4 FH2 MTX Follic acid CH3 Leucovorin

41. Resistance to Methotrexate -Decreased transport into cells (active) -Production of altered DHFR with decreased affinity for drug -Increased amount of DHFR (gene amplification); cells make more enzyme

42. Use and Toxicity Used with leucovorin rescue Combination chemotherapy Adjuvant to surgery Toxicity: BM depression GI toxicity (depends on dose)

43. Antimetabolites Interfere with nucleic acid biosynthesis

44. Nucleic Acids RNA- ribose sugars, phosphate, bases (A-U, C-G) DNA –deoxyribose sugars, phosphate, bases ( A-T, C-G) double helical structure -s--P—s—P—s—P—s– B B B B B B -s--P—s—P—s—P—s--

45. Purine and Pyrimidine Bases Purines NH2 R = none: adenine R = NH2: guanine N HN Base pairing: AT or AU, GC R NH N R1 Pyrimidines R1: (=O) uracil, thymine (-NH2) cytosine R2: (-CH3) thymine R2 HN NH

46. Nucleic Acid Biosynthesis DE NOVO SALVAGE C, H, N, O S-Base sugar + base DNA + ribose sugar(nucleoside) 5’PRPP catabolism phosphorylase RNA S-Base-MP (nucleotide) nucleotide-TP nucleotide-DP ribonucleotide reductase deoxynucleotide-DP RNA deoxynucleotide-TP DNA

47. DNA Synthesis Salvage Pathways Reuse degraded DNA products (sugars, bases and phosphates) Type I (purines and pyrimidines) Base + 5’PRPP nucleotide MP Type II (pyrimidines only) (specific kinases) Base + ribose-1-P nucleoside nucleotide HGPRT phosphorylase kinase

48. Purine Analogs 6-mercaptopurine (6MP) 6-thioguanine (6TG), cladribine; fludarabine Used mainly to treat leukemia and lymphomas Must be converted to nucleotides to be active cytotoxic agents; lethal synthesis: converted to nucleotides by salvage pathways

49. Purine Analogs Mechanisms of Cytotoxicity Inhibition of first step in de novo purine synthesis; negative feedback mechanism “pseudo –feedback inhibitors” Inhibition later steps in purine synthesis; purine-RP (eg., 6MPRP) structural analog inosinic acid (IMP), covalent binding to enzyme Incorporation of active purine-RP into DNA

50. De Novo Purine Biosynthesis 5’PRPP 5’PR-amine 6MP-RP (pseudofeedback) Adenylocuccinic acid AMP ADP ATP DNA IMP 6MP-RP Xanthylic acid GMP GDP GTP