Pharmacology of Antineoplastic Agents

1. Pharmacology of Antineoplastic Agents Outline of Lecture Topics: • Background • Antineoplastic Agents: classification • a. Cell Cycle Specific (CCS) agents • b. Cell Cycle Non-Specific (CCNS) agents • c. Miscellaneous (e.g., antibodies) agents • Mechanisms of action • Side Effects • Drug Resistance Kishore Wary, Ph.D. Dept Pharmacology kkwary@uic.edu

2. PART I • Background • Antineoplastic Agents • a. Cell Cycle Specific (CCS) agents • b. Cell Cycle Non-Specific (CCNS) agents • c. Miscellaneous (e.g., antibodies) agents

3. Cancer Definition: Cancer* is a term used for diseases in which abnormal cells divide without control and are able to invade other tissues. Cancer cells can spread to other parts of the body through the blood and lymph systems, this process is called metastasis. Categorized based on the functions/locations of the cells from which they originate: Carcinoma - skin or in tissues that line or cover internal organs. E.g., Epithelial cells. 80-90% reported cancer cases are carcinomas. Sarcoma - bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia - White blood cells and their precursor cells such as the bone marrow cells, causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma - cells of the immune system that affects lymphatic system. Myeloma - B-cells that produce antibodies- spreads through lymphatic system. Central nervous system cancers - cancers that begin in the tissues of the brain and spinal cord. (*National Cancer Institute, NCI)

4. Cancer Therapeutic Modalities (classical) Surgery Radiation Chemotherapy 1/3 of patients without metastasis Respond to surgery and radiation. If diagnosed at early stage, close to 50% cancer could be cured. 50% patients will undergo chemotherapy, to remove micrometastasis. However, chemotherapy is able to cure only about 10-15% of all cancer patients. Cancer Chemotherapy Chapter 55. B.G. Katzung

5. New types of cancer treatment • Hormonal Treatments: These drugs are designed to prevent cancer cell growth by preventing the cells from receiving signals necessary for their continued growth and division. E.g., Breast cancer – tamoxifen after surgery and radiation Specific Inhibitors: Drugs targeting specific proteins and processes that are limited primarily to cancer cells or that are much more prevalent in cancer cells. Antibodies: The antibodies used in the treatment of cancer have been manufactured for use as drugs.E.g., Herceptin, avastin Biological Response Modifiers: The use of naturally occuring, normal proteins to stimulate the body's own defenses against cancer. E.g., Abciximab, rituxmab Vaccines: Stimulate the body's defenses against cancer. Vaccines usually contain proteins found on or produced by cancer cells. By administering these proteins, the treatment aims to increase the response of the body against the cancer cells. Cancer Chemotherapy Chapter 55. B.G. Katzung

6. Cancer Chemotherapy (Background) • Most of the recent progress using antineoplastic therapy is based on: • Development of new combination therapy of using existing drugs. • Better understanding of the mechanisms of antitumor activity. • Development of chemotherpeutic approaches to destroying micrometastases • Understanding the molecular mechanisms concerning the initiation of tumor growth and metastasis. • Recognition of the heterogeneity of tumors • B. Recently developed principles which have helped guide the treatment of neoplastic disease • A single clonogenic cell can produce enough progeny to kill the host. • 2. Unless few malignant cells are present, host immune mechanisms do not play a significant role in therapy of neoplastic disease. • 3. A given therapy results in destruction of a constant percentage as opposed to a constant number of cells, therefore, cell kill follows first order kinetics.

7. Cancer Chemotherapy • C. Malignancies which respond favorably to chemotherapy: • choriocarcinoma, • Acute leukemia, • Hodgkin's disease, • Burkitt's lymphoma, • Wilms' tumor, • Testicular carcinoma, • Ewing's sarcoma, • Retinoblastoma in children, • Diffuse histiocytic lymphoma and • Rhabdomyosarcoma. D. Antineoplastic drugs are most effective against rapidly dividing tumor cells.

8. E. The Main Goal of Antineoplastic Agents IS to eliminate the cancer cells without affecting normal tissues (the concept of differential sensitivity).  In reality, all cytotoxic drugs affect normal tissues as well as malignancies - aim for a favorabletherapeutic index (aka therapeutic ratio). LD50 ----- ED50 Therapeutic Index = A therapeutic index is the lethal dose of a drug for 50% of the population (LD50) divided by the minimum effective dose for 50% of the population (ED50). Cancer Chemotherapy Chapter 55. B.G. Katzung

9. F. The effects of tumor burden, scheduling, dosing, and initiation/duration of treatment on patient survival. Untreated patients Infrequent scheduling of treatment courses. Prolongs survival but does not cure. More intensive and frequent treatment. Kill rate > growth rate. Early surgical removal of the primary tumor decreases the tumor burden. Chemotherapy will remove persistant secondary tumors. Cancer Chemotherapy Chapter 55. B.G. Katzung

10. General rules of chemotherapy • Aggressive high-dose chemotherapy • Dose-limiting is toxicity towards normal cells • Cyclic regimens - repeated administrations with appropriate intervals for regeneration of normal cells (e.g., bone marrow cells) • Supportive therapy - to reduce toxicity hematotoxicity – bone marrow transplantation, hematopoietic growth factors Specific antagonists: antifolate (methotrexate) – folate (leucovorin) MESNA- donor of –SH groups, decreased urotoxicity of cyclophosphamide. Detoxifying agent. dexrazoxane: chelates iron, reduced anthracycline cardiotoxicity amifostine: reduces hematotoxicity, ototoxicity and neurotoxicity of alkylating agents

11. General rules of chemotherapy • Combination of several drugs with different mechanisms of action, different resistance mechanisms, different dose-limiting toxicities. • Adjuvant therapy:Additional cancer treatment given after the primary treatment to lower the risk that the cancer will come back. Adjuvant therapy may include chemotherapy, radiation therapy, hormone therapy, targeted therapy, or biological therapy. • Neoadjuvant therapy:Treatment given as a first step to shrink a tumor before the main treatment, which is usually surgery, is given. Examples of neoadjuvant therapy include chemotherapy, radiation therapy, and hormone therapy. It is a type of induction therapy.

12. General rules of chemotherapy • Supportive therapy: -Antiemetics (5-HT3 -antagonists) -Antibiotic prophylaxis and therapy (febrile neutropenia) -Prophylaxis of urate nephropathy (allopurinol) -Enteral and parenteral nutrition -Pain – analgesic drugs -Psychological support Cancer Chemotherapy Chapter 55. B.G. Katzung

13. Antineoplastic Agents

14. Chemotherapy: classification basedon the mechanism of action Antimetabolites: Drugs that interfere with the formation of key biomolecules including nucleotides, the building blocks of DNA. Genotoxic Drugs: Drugs that alkylate or intercalate the DNA causing the loss of its function. Plant-derived inhibitorsof mitosis:These agents prevent proper cell division by interfering with the cytoskeletal components that enable the cell to divide. Plant-derived topoisomerase inhibitors:Topoisomerases unwind or religate DNA during replication. Other Chemotherapy Agents: These agents inhibit cell division by mechanisms that are not covered in the categories listed above.

15. Cancer Chemotherapy Chapter 55. B.G. Katzung

16. Cell cycle specificity of Anti-Neoplastic Agents Vincristine, Vinblastine Paclitaxel, Docetaxel Cyclophosphamide Bleomycin Actinomycin D M G 0 resting G Hydrocortisone G 2 1 G0 = resting phase G1 = pre-replicative phase G2 = post-replicative phase S = DNA synthesis M = mitosis or cell division S Actinomycin D Purine antagonists 5-Fluorouracil Methotrexate Cytosine arabinoside Cyclophosphamide Methotrexate 5-Fluorouracil 6-Mercaptopurine Cytosine arabinoside 6-Thioguanine Daunomycin

17. Pharmacology of Antineoplastic Agents PART II • Mechanisms of action • Side Effects • Drug Resistance Cancer Chemotherapy Chapter 55. B.G. Katzung

18. Topoisomerase Inh. Alkylating agents Antimetabolites Asparaginase Tubulin binders Chemotherapy: Mechanisms of Action 1 DNA Purines and Pyrimidines RNA Protein tubulin Cancer Chemotherapy Chapter 55. B.G. Katzung

19. Major Clinically Useful Alkylating Agents Cancer Chemotherapy Chapter 55. B.G. Katzung Bis(mechloroethyl)amines Nitrosoureas Aziridines

20. An Example of DNA Crosslinking Crosslinking: Joining two or more molecules by a covalent bond. This can either occur in the same strand (intrastrand crosslink) or in the opposite strands of the DNA (interstrand crosslink). Crosslinks also occur between DNA and protein. DNA replication is blocked by crosslinks, which causes replication arrest and cell death if the crosslink is not repaired.

21. Alkylating Agents (Covalent DNA binding drugs) The first class of chemotherapy agents used. They stop tumour growth by cross-linking guaninenucleobases in DNA double-helix strands - directly attacking DNA. This makes the strands unable to uncoil and separate. As this is necessary in DNA replication, the cells can no longer divide. Cell-cycle nonspecific effect Alkylating agents are also mutagenic and carcinogenic T A G C C G G A T C G Cancer Chemotherapy Chapter 55. B.G. Katzung

22. E.g., Mechlorethamine (Nitrogen Mustards) Cancer Chemotherapy Chapter 55. B.G. Katzung

23. Cyclophosphamide • Cyclophosphamide is an alkylating agent. It is a widely used as a DNA crosslinking and cytotoxic chemotherapeutic agent. • It is given orally as well as intravenously with efficacy. • It is inactive in parent form, and must be activated to cytotoxic form by liver CYT450 liver microsomaal system to 4-Hydroxycyclophamide and Aldophosphamide. • 4-Hydroxycyclophamide and Aldophosphamide are delivered to the dividing normal and tumor cells. • Aldophosphamide is converted into acrolein and phosphoramide mustard. • They crosslink DNAs resulting in inhibition of DNA synthesis

24. Cyclophosphamide Metabolism Inactive

25. Cyclophosphamide Clinical Applications: • Breast Cancer • Ovarian Cancer • Non-Hodgkin’s Lymphoma • Chronic Lymphocytic Leukemia (CLL) • Soft tissue sarcoma • Neuroblastoma • Wilms’ tumor • Rhabdomyosarcoma Cancer Chemotherapy Chapter 55. B.G. Katzung

26. Cyclophosphamide Major Side effects Nausea and vomiting Decrease in PBL count Depression of blood cell counts Bleeding Alopecia (hair loss) Skin pigmentation Pulmonary fibrosis Cancer Chemotherapy Chapter 55. B.G. Katzung

27. Ifosphamide • Mechanisms of Action • Similar to cyclophosphamide • Application • Germ cell cancer, • Cervical carcinoma, • Lung cancer • Hodgkins and non-Hodgkins lymphoma • Sarcomas • Major Side Effects • Similar to cyclophosphamide

28. A. Alkylating agents Cancer Chemotherapy Chapter 55. B.G. Katzung

29. A. Alkylating agents

30. A. Alkylating agents Cancer Chemotherapy Chapter 55. B.G. Katzung

31. Summary Cancer Chemotherapy Chapter 55. B.G. Katzung

32. Tubulin Binding Agents e.g., Vincristine, Vinblastine, VindesineVinorelbine: Inhibition of mitotic spindle formation by binding to tubulin. M-phase of the cell cycle. Polymerization Vincristine  tubulin a e.g., Paclitexal: binds to tubulin, promotes microtubule formation and retards disassembly; results in mitotic arrest. Depolymerization Paclitexal (taxol)

33. B. Natural Products 1. Antimitotic Drugs 2. Antimitotic Drugs

34. 3. Epipodophyllotoxins (These are CCS) Act on Topoisomerase II Accumulation of single- or double-strand DNA breaks, the inhibition of DNA replication and transcription, and apoptotic cell death. Etoposide acts primarily in the G2 and S phases of the cell cycle

35. 4. Antibiotics (CCS) Inhibit DNA and RNA syntheses Cancer Chemotherapy Chapter 55. B.G. Katzung

36. 5. Enzymes: L-asparaginase Cancer Chemotherapy Chapter 55. B.G. Katzung

37. MTX polyglutamates Are selectively retained In tumor cells. C. Antimetabolites (Folic acid analog) Folic acid is a growth factor that provides single carbons to the precursors used to form the nucleotides used in the synthesis of DNA and RNA. To function as a cofactor folate must be reduced by DHFR to THF. Reduced Folate Carrier protein * * * * * MTX Kills cells during S-phase Cancer Chemotherapy Chapter 55. B.G. Katzung

38. C. Antimetabolites Cancer Chemotherapy Chapter 55. B.G. Katzung

40. 6. Drug Resistance • One of the fundamental issue in cancer chemotherapy is the development of cellular drug resistance. It means, tumor cells are no longer respond to chemotherapeutic agents. For example, melanoma, renal cell cancer, • brain cancer often become resistant to chemo. • A few known reasons: • Mutation in p53 tumor suppressor gene occurs in 50% of all tumors. This leads to resistance to radiation therapy and wide range of chemotherapy. • Defects or loss in mismatch repair (MMR) enzyme family. E.g., colon cancer no longer respond to fluoropyrimidines, the thiopurines, and cisplatins. • Increased expression of multidrug resistance MDR1 gene which encodes P-glycoprotein resulting in enhanced drug efflux and reduced intracellular accumulation. Drugs such as athracyclines, vinca alkaloids, taxanes, campothecins, even antibody such as imatinib. Cancer Chemotherapy Chapter 55. B.G. Katzung

41. Summary • The main goal of anti-neoplastic drug is to eliminate the cancer cells without affecting normal tissues. • Log-Kill Hypothesis states that a given therapy kills a percentage of cells, rather then a constant number, therefore, it follows first order kinetics. Aim for a favorable therapeutic index. • Early diagnosis is the key. • Combination therapy and adjuvant chemotherapy are effective for small tumor burden. • Two major classes of antineoplastic agents are: • a. Cell Cycle Specific and • b. Cell Cycle Non-Specific agents • Because chemotherapeutic agents target not only tumor cells, but also affect normal dividing cells including bone marrow, hematopoietic, and GI epithelium. Know what the side effects are. • Drug resistance is often associated with loss of p53 function, DNA mismatch repair system, and increased MDR1 gene expression.