Antineoplastic Agents: Part II

1. Antineoplastic Agents: Part II Ujjwala Shenoy

2. Antineoplastic medications: drugs used to treat cancer, also called cancer drugs, cytotoxic agents and anticancer drugs. Cancer • Along with heart disease, cancer is the largest cause of death in the developed world • Cancer affects 1 in 3 people and is responsible for 25% of all deaths • Cancer is an unregulated proliferation of cells due to loss of normal controls, resulting in unregulated growth, lack of differentiation, local tissue invasion, and, often, metastasis. • Cancer can develop in any tissue or organ at any age. There is often an immune response to tumor. • Many cancers are curable if detected at an early stage, and long-term remission is often possible in later stages. Causes of Cancer: 1. 30 % is due to smoking: lung, mouth, pharynx, larynx, esophagus, urinary bladder, pancreas, and kidney cancers. 2. Lifestyle – diet, alcohol consumption, reproductive behavior, sexual behavior, exposure to sunlight, etc. 3. At least 15% are related to viruses, e.g. cervical cancer caused by human papillomavirus.

3. Types of Tumors: -Benign: non cancerous and not an immediate threat to life, even though treatment eventually may be required for health. -Malignant: tending to worsen and cause death, invasive and metastasis Characteristics of cancer cells: • Persistent cell proliferation • Invasive growth • Metastases (a tumor may shed cells into the circulation. Although most circulating tumor cells die as a result of intravascular trauma, a tiny number adhere to the vascular endothelium and penetrate into surrounding tissues, generating independent tumors (metastases) at distant sites.) Etiology of Cancer • Genetics • Viruses • Occupational and Environmental Carcinogens • Radiation

4. Etiology of Cancer : Genetic • Genetic mutations are largely responsible for the generation of malignant cells. Two major categories of mutated genes are oncogenes and tumor suppressor genes. ONCOGENES Oncogenes are abnormal forms of normal genes (proto-oncogenes) that regulate cell growth. Mutation of these genes may result in direct and continuous stimulation of the molecular biologic pathways that control cellular growth and division. For example, the ras gene encodes the Ras protein, which regulates cell division. Mutations may result in the inappropriate activation of the Ras protein, leading to uncontrolled cell growth and division.

5. Etiology : Genetic: Tumor suppressor genes Tumor suppressor genes are inherent genes that play a role in cell division and DNA repair and are critical for detecting inappropriate growth signals in cells. If these genes, as a result of inherited or acquired mutations, become unable to function, genetic mutations in other genes can proceed unchecked, leading to neoplastic transformation. • Another important regulatory protein, p53, prevents replication of damaged DNA in normal cells and promotes cell death (apoptosis) in cells with abnormal DNA. Inactive or altered p53 allows cells with abnormal DNA to survive and divide. The p53 gene is defective in many human cancers. • Telomeres are nucleoprotein complexes that cap the ends of chromosomes and maintain their integrity. Telomere shortening occur with aging .Telomerase is an enzyme that provides for telomere synthesis and maintenance, thus telomerase may potentially allow for cellular immortality. Telomerase activity may promote tumors through multiple, complex mechanisms, especially by subverting the normal DNA synthetic checkpoints.

6. Etiology Cancer: Viruses • Viruses contribute to the pathogenesis of human malignancies through the integration of viral genetic elements into the host DNA. These new genes are expressed by the host; they may affect cell growth or division, or disrupt normal host genes required for control of cell growth and division. Alternatively, viral infection may result in immune dysfunction, leading to decreased immune surveillance for early tumors. E.G. :Epstein-Barr, nasopharyngeal carcinoma -Hepatitis B virus, hepatocellular carcinoma -HIV Kaposi's sarcoma.

7. Etiology Cancer: Immune System • Immune system dysfunction as a result of genetic mutation, acquired disease, aging, or immunosuppressants interferes with normal immune surveillance of early tumors and results in higher rates of cancer. • Known cancer-associated immune disorders include : immune deficiency secondary to immunosuppressants or HIV infection (Kaposi's sarcoma)& rheumatologic conditions, such as Rheumatoid Arrhythrities (B-type lymphoma).

8. Etiology Cancer: Radiation • Carcinogenesis can result from ionizing radiation and may develop from 2 different mechanisms 1. Direct ionization – damages DNA and other molecules can cause direct somatic mutations 2. Secondary effectors such as oxygen radicals can be formed by interaction with ionizing radiation. Oxygen free radicals can damage and kill cells and also induce mutations.

9. Pathogenesis of Neoplasia : Cancer development can begin with a brief exposure (hours or days) to a chemical into an activated form and the chemical need not be present ever again. However, DNA is altered via mutagens including chemical carcinogens, viruses, and radiation. This mutations is inherted by at least one cell division (intiation). This mutation mainly lead to activation of proto-oncogene into oncogenes (leading to uncontrolled cell proliferation) and/or inactivation of tumor suppressor genes (leading to resistance to apoptosis.) Upon exposure to other epigenetic factors (hormones, co- carcinogens, immunosuppressant…which themselves are non carcinogenic) tumor growth is promoted (promotion)

10. • Initiation - point at which an irreversible alteration, usually genetic, is introduced into a target cell. Initiation: (1) is essentially irreversible (2) caused only by carcinogenic compounds (3) occurs rapidly after carcinogen exposure (4) alone does not result in tumor formation

11. • Promotion is the process whereby an initiated tissue or organ develop focal proliferations and it requires the presence of continuous stimulation. Promotion (1) reversible (2) acts only after exposure to an initiating agent (3) requires repeated administration of a promoter (4) is not carcinogenic in itself

12. Etiology and Pathogenesis of NeoplasiaInitiation and Promotion

14. Problems associated with chemotherapy1-Resistance to chemotherapy Resistance to chemotherapy may develop by several mechanisms: • Decrease in the amount of drug uptake by cancer cells E.G. Methotrexate • Increase in the amount of drug removed by cancer cells. (Transporters=P-glycoprotein). E.G. Vinblastine ,doxorubicin, bleomycin ,etapsoid…. • Decrease or alteration in target molecule sensitivity – this is caused by mutation in the molecule targeted by the drug E.G. Methotrexate,Mercaptopurine,doxorubicin • Increase in DNA repair ability of the cell via an increased expression of DNA repairing enzymes. E.G. Alkylating agent

15. 2-Toxicity and side Effects of Antineoplastic Agents Normal cells in the body that tend to be injured the most due to chemotherapy are those which have a high growth fraction. Those are bone marrow, GI Tract ,hair follicles, reproductive organs .Leading to the followings: • Alopecia- hair loss • Myelosuppression-bone marrow loss • Emetic potential: disruptive to cells in stomach which causes: Nausea/vomiting • Low WBC count- low immunity, high secondary infections

16. Treatment of Chemotherapy Toxicity

17. 3-Treatment-induced tumor Many anticancer drugs are mutagens and can cause the rise of neoplasm ten or more years after the original cancer was cured.

18. Cell cycle Scientists have determined that cell cycle can be divided into:. Gap 0 (G0): There are times when a cell will leave the cycle and quit dividing. This may be a temporary resting period or more permanent. An example of the latter is a cell that has reached an end stage of development and will no longer divide (e.g. neuron). Gap 1 (G1): Cells increase in size in Gap 1, produce enzymes needed for DNA synthesis S Phase: To produce two similar daughter cells, the complete DNA instructions in the cell must be duplicated. DNA replication occurs during this S (synthesis) phase. Gap 2 (G2): It is the gap between DNA synthesis and mitosis, the cell will continue to grow and produce new proteins & RNA. Mitosis or M Phase: Cell growth and protein production stop at this stage in the cell cycle. All of the cell's energy is focused on the complex and orderly division into two similar daughter cells.

19. Cell-cycle specific, or phase-specific agents; Cell-cycle nonspecific or phase-non-specific agents

20. Cancer chemotherapeutic agents They are classified into: • Cell-cycle non specific agents(CCNS): are cytotoxic in any phase of the cycle even on G0 phase and so are more effective against large slowly growing tumors. E.G.Bleomycin. • Cell-cycle specific (CCS): are cytotoxic on all phases but not on cells out of the cycle(at G0 ) and so are more effective against rapidly growing tumors. Work better in combination than alone E.G. Mitomycin, doxorubicin,….etc. • Phase specific : act on specific phase of the cycle E.G.Vinca alkaloids act more in M-phase, antimetabolites (mainly act on S-phase.)

21. Anticancer Drugs: Classification There are three Major Groups of Anticancer Drugs: 1) Cytotoxic Drugs (largest group) A-Alkylating agents B-Antimetabolites C-Antitumor antibiotics D-Plant alkaloids E-Miscellaneous cytotoxic drugs 2) Hormones and hormone antagonists These are among the best-tolerated chemotherapeutics because they target specific receptors, and thus only specific cell types e.g. Tamoxifen 3) Immunomodulators -Immunosuppressant -Immunostimulants, including interferons and interleukins -antibodies 4) Radio-isotopes

22. Treatment possibilities for cancer: 1) surgery, 2)radiotherapy, and 3)chemotherapy. Some cancers where chemotherapy works very well: • Childhood leukemia • Retinoblastoma • Osteosarcoma • Testicular cancer • Hodgkin’s Disease • Some lymphomas • Some early breast cancers Cancers that are very difficult to treat with chemotherapeutics (need surgery or radiotherapy first): • Colon • Lung • Late stage breast cancer • Pancreatic cancer

23. 1-Cytotoxic Drugs

25. A-Alkylating Agents(CCNS) Mechanism of Alkylating Agents • These drugs work by alkylation with nucleophilic substitution . They alkylate a variety of cellular constituents, such as cell membranes, proteins, and most importantly DNA. More specifically, the nitrogenous bases of DNA are what get alkylated. • The drugs start off as pro-drugs that become activated when a chlorine atom is extracted. A carbonium ion is thus formed. This “carbonium ion” is very electrophilic and will then attack any free pair of electrons (i.e. on the N7 of guanine). This electrophilic attack results in a bond being formed between the drug and the guanine of DNA. As a result of this “alkylation”, there are a few consequences: 1) Miscoding (In transcription) 2) Cross linking- this only occurs if the drug is bifunctional The net result is cancer cell undergo apoptosis.

26. Alkylating agents contd Highly reactive, substitute alkyl groups for hydrogen atoms of organic compounds (ex. DNA). Five classes: 1. Nitrogen mustard derivatives 2. Ethylenimine derivatives 3. Alkyl sulfonates 4. Triazine derivatives 5. Nitrozoureas Most of them contain more than one alkylating group and therefore considered polyfunctional alkylating agents. As a class alkylating agents are considered to be cell-cycle nonspecific

27. Alkylating Agents(CCNS)

28. Cross linking

29. Subgroups of Alkylating Agents • 1) Nitrogen mustards • 2) Nitrosoureas • 3) Alkyl sulfonates • 4) 4-Platinum Coordination Compounds 1-Nitrogen Mustards E.G.: Mechlorethamine, cyclophosphamid, melphalan & chlorambucil a-Mechlorethamine - first alkylating agent employed clinically - bifunctional, thus can crosslink DNA - extremely unstable and is inactivated within a few minutes following administration. Thus it is given IV. Clinical Uses -Hodgkin’s Disease -Non-Hodgkin’s Lymphoma Toxicity/ Side Effects - Dose limiting toxicity is bone marrow depression - Nausea/ Vomiting - Alopecia - Diarrhea - Sterility

30. b-Cyclophsphamid -It acts as cytotoxic and immunosuppressor agent. - Prodrug which must be activated by the cytochrome p450 system, which turns it into a nitrogen mustard. - bifunctional agent -most widely used alkylating agent Clinical Uses • - Hodgkin’s Disease • - Non-Hodgkin’s lymphoma • - Solid tumors of head, neck, ovaries, and breast • - frequently used in combination with methotrexate (anti-metabolite) or doxorubicin (anti-tumor antibiotic), or fluorouracil as adjuvant therapy post breast cancer surgery • - Organ transplant recipients (due to immunosuppressive actions) Toxicity/ Side Effects • - bone marrow depression • - severe nausea and vomiting • - acute hemorrhagic cystitis and renal damage???? (can be minimized via high fluid intake/infusion) • - sterility • - hypersensitivity reactions

31. 2-Nitrosoureas • - bifunctional • - active against broad spectrum of neoplastic disease • - inhibits synthesis of both DNA and RNA, as well as proteins • - These drugs are highly lipophilic, so they can easily cross blood-brain-barrier, and are great for CNS tumors. • - Big problem in this class is that they are highly mutagenic and highly carcinogenic. • - Major toxicity is DELAYED bone marrow depression& Pulmonaryfibrosis. Clinical uses - primary and metastasis tumors of the brain - Hodgkin’s Disease - Non-Hodgkin’s lymphoma - Adenocarcinoma of stomach, colon, and rectal cancer - Hepatocarcinoma E.G.: a-Carmustine b-Lomustine

32. 3-Alkyl Sulfonates Busulfan Clinical uses Great effect on for Chronic granulocytic Leukemia Toxicity/ Side Effects - Dose limiting toxicity is bone marrow depression. - Pulmonary infiltrates and pulmonary fibrosis - Tonic-clonic seizures in epileptics - Nausea and vomiting - Alopecia - Sterility - Skin hyper pigmentation - Cataracts - Hepatitis

33. 4-Platinum Coordination Compounds E.G.: Cisplatin • forms crosslinks within DNA strands. Cis-platin is not really an “alkylating” agent, but since it operates via the same mechanism as the alkylating agents, it is placed within that group. Clinical Uses - Very powerful against TESTICULAR CANCER - Also good for carcinomas of ovary, bladder, head, and neck Toxicity/ Side Effects - Renal tubular damage (minimized via massive hydration coupled with anti-emetics) - Ototoxicity and peripheral neuropathy - VERY SEVER vomiting( Ondanosetron…?) Carboplatin: is a derivative of cisplatin with less nephero- ,neuro- & ototoxicity.

34. Classes of agents Antimetabolites • Analogues of normal metabolites. The interact with enzymes • and damage cells by: • 1. Substituting for a metabolite normally incorporated into a key • molecule • Competing successfully with a normal metabolite for • occupation of the catalytic site of a key enzyme • Competing with a normal metabolite that acts at an enzyme • regulatory site to alter the catalytic rate of the enzyme

35. B-Antimetabolites(CCS) • An antimetabolite is a chemical with a similar structure to a metabolite required for normal biochemical reactions, yet different enough to interfere with the normal functions of cells, including cell division. • All antimetabolites are used in cancer treatment, as they interfere with DNA production and therefore cell division and the growth of tumors (mainly in S-phase specific). • They are classified into: 1- Folic acid analogues 2- Purine analogues 3- Pyrimidine analogues • Purin and pyrimidine antagonists are phosphorelated inside the body into nucleotid form in order to be cytotoxic Uses • leukemia. • non-Hodgkin's lymphoma • inflammatory bowel disease such as Crohn's Disease and ulcerative colitis • It is widely used as immunosuppressant in transplantations to control rejection reactions.

36. 1-Folic acidanalogues Methotrexate: -A folic acid analogue, prevents the formation of tetrahydrofolate, essential for purine and pyrimidine synthesis, by inhibiting dihydrofolate reductase. This leads to inhibition of production of DNA, RNA and proteins (as tetrahydrofolate is also involved in the synthesis of amino acids as serine and methionine). • It is actively taken up into the cells by the same transport system for folate (resistance…..?) • The most common toxicity is nepherotoxicity (pptn of the drug in renal tubule.)

37. Cont: Folic acid analogues1-Methotrexate compete with folic acid for DHFR and inhibits it . Therefore, it inhibits the synthesis of DNA, RNA and proteins.2-Also,DHFR catalyses the conversion of dihydrofolate to the active tetrahydrofolate which is needed for the de novo synthesis of the deoxynucleoside thymidine phosphate DTMP ( required for DNA synthesis)DEXOURIDIN MONO PHOSPHATE TO DEXO THYMIDIN MONO PHOSPHATE

38. 2-Purine analogues Mercaptopurine (6−mercaptopurine, or 6−MP) : -It is immunosuppressive cytotoxic substance. It is widely used in transplantations to control rejection reactions. -It is acts as a purine analogue and once enter the cell, it is converted to 6-MP-ribosephophate and can be incorporated into RNA&DNA resulting in non functioning RNA & DNA &finally inducing cell cycle arrest and apoptosis. -It also inhibits purine ring biosynthesis Adverse reactions • Diarrhea, nausea, vomiting, loss of appetite, • Allergic reaction include rash, itching, swelling, dizziness, trouble breathing. • Mercaptopurine cause myelosuppression. Those taking mercaptopurine should get permission from a doctor in order to receive immunizations and vaccinations. Azathioprine: It is one of the mainimmunosuppressive cytotoxic substance. It is widely used in transplantations to control rejection reactions. It is nonenzymatically cleaved to 6 - M P that acts as a purine analogue and inhibits DNA synthesis

39. 3-Pyrimidine analogues 5-flurouracil (5-FU) • It act as a uracil analogue, it is transformed inside the cell into 5-FU deoxynucleotide which compete with deoxyuridine monophosphate DUMP for thymidylate synthase leading to inhibition of deoxythymidine monophosphate DTMP synthesis inhibition of DNA synthesis (Not RNA or protien) • Also it is incorporated into DNA non functioning DNA . • finally inducing cell cycle arrest and apoptosis by inhibiting the cell's ability to synthesize DNA. • It is an S-phase specific drug • 5−FU may be used in combination with other chemotherapy agents to treat cancers of the breast, stomach,colon, rectum, and pancreas. Side effect 1- Most unwanted effect is GIT epithelial damage, diarrhea and mouth ulcers. 2-the most dangerous side effect is bone marrow suppression Cytarabine It is analogue to 2-deoxycytidine and in the body it is converted into cytosine triphosphate and inhibit DNA polymerase thus inhibiting DNA synthesis.

40. 5-flurouracil (5-FU)

41. Antibiotics The clinically useful antibiotics are natural products of various strains of the soil fungus Streptomyces. The directly bind DNA, and inhibit DNA and RNA synthesis As a class they behave as cell-cycle nonspecific agents. Examples: Doxorubicin, Actinomycin D, Bleomycin, Mitomycin C

42. C-Antitumor antibiotics (CCNS) 1-Dactinomycin • is isolated from soil bacteria of the genus Streptomyces. • It was the first antibiotic shown to have anti-cancer activity and used in treatment of a variety of cancers. • It inhibits transcription by binding to DNA at the transcription initiation complex and preventing elongation by RNA polymerase. • As it can bind DNA duplexes, it can also interfere with DNA replication 2-Doxorubicin (adriamycin) Mechanism of action • Doxorubicin is anthracyclin antibiotic interferes with the cells' production of DNA and RNA by inserting itself between adjacent base pair causing local uncoiling thus blocking DNA and RNA synthesis. • Also its antitumor effect is related to its inhibition of topoisomerase II enzyme (responsible for DNA repair). • CYTP 450 catalyzes the conversion of Dox. into semiquinone free radicals which produce superoxide ion & H2O2 that mediate single strand scission in DNA

43. Uses • Multiple cancers includingbreast, bone, ovarian & leukemia. • Acute lymphocytic leukemia (ALL). • Non−Hodgkin's lymphoma Side effects • A major problem with the use of doxorubicin is that it cause irreversible heart problems specially heart failure • Hypersensitivity, myelosuppression • Nausea, vomiting & diarrhea • Urine and tears may take on a red color. 3-Mitomycin−C • Mitomycin−C is an antitumor antibiotic. Mechanistically however, it belongs to DNA alkylating agents. • Upon bioactivation inside the cell ,it preferentially alkylates O6 of guanine base in DNA leading to cross linking of DNA. • It also degrade DNA through formation of free radicals. Side effects -mitomycin−C may cause bone marrow suppression. -Lung fibrosis may occur. If these lung problems do occur, corticosteroids may provide effective therapy. Stopping mitomycin−C therapy may also be recommended.

44. 4-Bleomycin • It is cytotoxic in any phase of the cycle even on G0 phase • Bleomycin degrade preformed DNA causing chain fragmentation and release of free bases through the formation of free radicals (superoxide and hydroxyl radicals). Uses -Bleomycin is used in the treatment of a number of different cancers, including cancer of the head and neck, skin, esophagus, lung, testis, and genitourinary tract. -In addition, it is used in the treatment of Hodgkin's disease and non−Hodgkin's lymphomas. Side effects • Pulmonary fibrosis • Raynaud's phenomenon (which affects the fingers and toes, may involve pain, pale color, and abnormal sensation as burning) • In addition, headache, and nausea and vomiting may occur.

45. 5-Procarbazine • Procarbazine is an anticancer agent inhibits DNA and RNA synthesis in cells • interfering with mitosis. Uses • Procarbazine is used in the treatment of various cancers, although the best established usage is with Hodgkin's disease. • Other cancers in which procarbazine is sometimes used include lymphomas, brain tumors, skin cancer, lung cancer, and multiple myeloma. Side effects • it decreases the white blood cells and the platelet cells. • The most severe side effect is nausea and vomiting. • There may be neurological side effects such as confusion, sleepiness, depression, nightmares, agitation, and nervousness (it is weak MAOI………hypertension???)

46. Classes of agents Plant Alkaliods Vinca alkaloid. Produced from the common periwinkle plant. The clinically useful alkaloids are large complex molecules that exert their antitumor effect by binding to cellular microtubular proteins and inhibiting microtubular polymerization, the essential compounds of the mitotic spindle. Effect - mitotic arrest. Taxanes - products of the yew tree. The toxicity of the leaves or bark is caused by alkaloids taxanes. Paclitaxel – is a natuarla product, a new class of antineoplastic agents, the taxanes, that targets the microtubules. The taxanes are potent microtubule-stabilizing agents, promoters of microtubule assemly. This is in contrast to vinca. They block cells in G2/M phases of the cell cycle.

47. E-Miscellaneous cytotoxic drugs 1-Crisantaspase • It is a preparation of asparaginase which kills cancer cells by breaking down certain protein (L−asparagine) that is necessary for survival and growth of certain tumors incapable of forming such protein e.g. acute lymphoblastic leukemia ALL. • Fortunately, normal cells are not dependent on L−asparagine for survival. • Asparaginase is mainly given in combination with vincristine and steroids (either prednisone or dexamethasone). 2-Mitotan • effective in the treatment of adrenocortical carcinoma. • As a chemical, mitotane resembles the insecticides DDD and DDT, although mitotane does not harm people as these do. Scientists do not understand why, but the drug causes damage to the adrenocortex in such a way as to be helpful for some patients with adrenocortical tumors. In addition, mitotane restricts the ability of the gland to produce steroids.

48. Hormones • Breast and Prostate cancers frequently demonstrate hormone-dependent growth (at least in early stage disease) • In hormone therapy toxicities tend to be more mild. Classification • Corticosteroids • Estrogens • Progestins • Antiestrogens • Androgens • Antiandrogens • Gonadotropin releasing hormone analogs

50. Summary – Hormone Drugs