Pharmacology of Chemo/Anticancer Drugs PDF

Pharmacology of Chemo /Anticancer Drugs Rakesh Tiwari, Ph.D. Associate Professor WesternU/COMP-NW Lebanon, OR Email: rt...

Pharmacology of Chemo /Anticancer Drugs Rakesh Tiwari, Ph.D. Associate Professor WesternU/COMP-NW Lebanon, OR Email: [email protected] Phone: (541) 259-0318 (Questions: Discussion Board) This morning, our topic is Chemotherapy and Anticancer Drugs used to treat different types of cancer. Given that we are in FOM6, our primary focus will be on hematological cancers, such as leukemias and lymphomas. However, we will also cover all major types of chemotherapeutic agents to provide you with a broader understanding of these drugs, which you can apply during your rotations and in your practice. Since these are some of the most toxic drugs that are prescribed for patients, it is important that you to know the adverse effects of these drugs. 1  Learning Objectives Explain the general principles of cancer and its treatment. Identify and differentiate major classes of Anticancer Agents. Explain the general mechanism of action (MOA) of Anticancer Agents. Analyze the pharmacological effects of each class of Anticancer Agents. Explain the use of sodium thiosulfate, filgrastim, sargramostim, mesna, leucovorin, allopurinol, dexrazoxane, tocilizumab, etc. with anticancer agents. We will first cover some general principles of tumors and cancer cells to understand how antineoplastic agents are used to treat cancers. We will next cover some general pharmacological properties of the antineoplastic agents before talking about the major classes of drugs that are used to treat cancers. Finally, I will cover the pharmacological properties of the individual agents in each of the major classes. 2  Types of Cancers (Biochemistry-Cancer Genetics (The Immunology Cancer lecture by Dr. Rai on October 28, 2024) and Immunology-Autoimmunity lecture on October 28, 2024, by Dr. Thrush) ¤ Carcinomas ¤ Sarcomas ¤ Lymphomas ¤ Leukemias (Myelomas) ¤ Myelomas Non-Hematological Cancers (on the left and lower right) Carcinomas arise from the cells that cover external and internal body surfaces. They are the most common type of cancers. Sarcomas arise from cells found in the supporting tissue of the body (bone, cartilage, fat connective tissue and muscle). Hematological Cancers: Leukemias are cancers of the immature blood cells that grow in the bone marrow and tend to accumulate in large numbers in the bloodstream. Lymphomas arise in the lymph nodes and tissues of the body’s immune system. Myelomas are a cancer of plasma cells (i.e., bone marrow cancer), a type of white blood cell responsible for producing antibodies. 3  Principles of Cancer: Causes ¤ Cancer is characterized by the uncontrolled multiplication and spread of abnormal forms of the body’s own cells ACQUIRED INHERITED (Proto-oncogenes) Mutations may be INHERITED (e.g., defective Rb gene in the familial form of retinoblastoma) or they may be ACQUIRED as a result of viral infection or damage to cellular DNA caused by carcinogens [e.g., chemicals in cigarette smoke, asbestos, radiation (UV, radon gas, X-rays]. It is also possible for mutations to occur as RANDOM ERRORS during cell division. DNA repair is the cellular mechanism that protects the cell from these random errors during cell division. If DNA repair is defective, it could result in the replication of mutations in the cell progeny. Proto-oncogenes are genes that regulate cell growth. When a proto-oncogene mutates or there are too many copies of it, it is permanently TURNED ON or ACTIVATES the cell cycle. When this happens, the cell grows out of control, which can lead to cancer. A mutated proto-oncogene is called an ONCOGENE. Tumor suppressor genes are genes that normally regulate cell division, repair DNA damage, or tell cells when to die (i.e., apoptosis). When tumor suppressor genes are inactivated, cells can grow out of control, which can lead to impaired apoptosis and cancer. An important difference between ONCOGENES and TUMOR SUPPRESSOR GENES is that oncogenes result from the ACTIVATION (turning on) of proto-oncogenes, but tumor suppressor genes cause cancer when they are INACTIVATED (turned off). 4  Principles of Cancer: Cellular Mechanism* (Protein synthesis) (vs Proto-oncogenes) Go (resting) * https://www.youtube.com/watch?v=1mo80kTZgW4 There is an excellent Youtube video that explains the role of protooncogenes and tumor suppressor genes on the regulation of cell growth and division and their role in cancer. I strongly suggest you look at this video (https://www.youtube.com/watch?v=1mo80kTZgW4). CELL CYCLE PHASES: 1) Go = Cell Cycle arrest; 2) G1 = Cellular contents (Protein synthesis, excluding the chromosomes are duplicated (Cells Grow, carry out normal functions, and replicate their organelles), 3) S= Each of the 46 chromosomes is duplicated by the cell (i.e., DNA SYNTHESIS), 4) G2 = The cell checks the duplicated chromosomes for errors, making any needed repair (i.e., Growth and Repair), 5) M= Cell division (MITOSIS) into 2 daughter cells. CELL CYCLE CHECKPOINTS (tumor suppression genes) control mechanisms within a cell that ensures proper division of a cell. At cell cycle checkpoints, cells check for DNA damage. If damage is found, the cell either waits to repair the damage or, if mistakes are irreversible, the cell goes through apoptosis. This prevents the damaged DNA from turning into mutations during DNA synthesis (S-Phase). DNA repair and and cell cycle checkpoints have been intimately linked with cancer due to their functions regulating genome stability and cell progression, respectively. ****** The three key checkpoints of the cell cycle are: 1) cell restriction or growth checkpoint (G1) (controlled by cyclins and CDKs), the DNA synthesis checkpoint (G2) and the mitosis or metaphase checkpoint (M). Tumor suppressor genes are normal genes that slow down cell division, repair DNA mistakes, or initiate apoptosis or programmed cell death. Tumor suppressor genes act likes brakes in a car. While the gas pedal (cell proliferation) is controlled by proto-oncogenes. SUPPLEMENTAL INFORMATION Cell Cycle in Cancer The cell cycle, the process by which normal cells progress and divide. In normal cells, the cell cycle is controlled by a complex series of signaling pathways by which a cell grows, replicates its DNA and divides. This process also includes mechanisms to ensure errors are corrected (DNA repair genes), and if not, the cells commit suicide (apoptosis). In cancer, as a result of genetic mutations, this regulatory process malfunctions, resulting in uncontrolled cell proliferation. ONCOGENES arise from the mutation of proto-oncogenes (regulate normal cell growth). They resemble proto-oncogenes in that they code for the production of proteins involved in growth control. However, oncogenes code for an altered version (or excessive quantities) of these growth- control proteins, thereby disrupting a cell's growth-signaling pathway. By producing abnormal versions or quantities of cellular growth-control proteins, oncogenes cause a cell's growth-signaling pathway to become hyperactive. To use a simple metaphor, the growth-control pathway is like the gas pedal of an automobile. The more active the pathway, the faster cells grow and divide. The presence of an oncogene is like having a gas pedal that is stuck to the floorboard, causing the cell to continually grow and divide. A cancer cell may contain one or more oncogenes, which means that one or more components in this pathway will be abnormal. TUMOR SUPPRESSOR GENES are normal genes whose ABSENCE can lead to cancer. In other words, if a pair of tumor suppressor genes are either lost from a cell or inactivated by mutation, their functional absence might allow cancer to develop. Individuals who inherit an increased risk of developing cancer often are born with one defective copy of a tumor suppressor gene. Because genes come in pairs (one inherited from each parent), an inherited defect in one copy will not lead to cancer because the other normal copy is still functional. But if the second copy undergoes mutation, the person then may develop cancer because there no longer is any functional copy of the gene. 5 What is the target of Anticancer Drug? 6  General Pharmacology: Log Kill Hypothesis ¤ DFN: A given dose kills a CONSTANT PROPORTION (FIRST ORDER KINETICS) of a cell population vs. a constant number of cells usually by three orders of magnitude ¤ Repeated doses must be given to continue reducing size of tumor ¤ Most applicable for: acute leukemias & aggressive high -grade lymphomas Cancer cell killing by chemotherapeutic drugs follows first order kinetics (i.e., a fixed fraction of cancer cells are killed during each cycle of chemotherapy = LOG KILL HYPOTHESIS). Cytotoxic drugs act by first-order kinetics; that is, at a given dose, they kill a constant fraction of tumor cells rather than a fixed number of cancer cells. For example, a drug dose that would result in a three-log cell kill (i.e., 99.9% cytotoxicity) would reduce the tumor burden of a patient with 108 leukemic cells to 105 cells. This killing of a fraction of cells rather than an absolute number per dose is called the log cell kill hypothesis. LOG KILL HYPOTHESIS is among the many important discoveries of how chemotherapeutics kill tumors. Since the growth of a tumor is exponential—increasing by a constant fraction of itself every fıxed unit of time—then anticancer drugs in effect shrink tumors by a constant fraction. The connection to “log” is that a constant fraction is a constant logarithmic amount. For example, a 90% kill reduces the cell number by one log to the base ten, a “one-log kill.” This concept explains why cancer patients need to be given frequent doses of chemotherapeutics (i.e., multiple cycles) to reduce the size of a tumor. If one combines two or more drugs (COMBINATION CHEMOTHERAPY) that do not interfere with each other, the log kills are ADDITIVE. For example if one drug can kill 90% of the cells and another can also kill 90% of the cells, using them both would kill 99%, a two-log kill. Since tumor cells can repopulate between cycles, administration of chemotherapeutic agents is closely spaced (i.e., serial induction cycles) and combo drugs are administered to achieve maximum cell killing. 7  General Pharmacology : Drug Classes Chemotherapy Pharmacology Targeted Therapy Chemotherapeutics Act on cell cycle Inhibit more Not very specific specific cell targets Mostly IV, some Many oral agents oral agents Cytostatic & Cytotoxic Cytotoxic Targeted therapy is a ‘smart bomb’ vs. Chemotherapy, which is a ‘cluster bomb’ for killing cancer cells. Targeted therapy is quite often much more efficient than other more conventional treatments such as Chemotherapy or radiation. Targeted therapy has a lot less long-term Adverse effects than Chemotherapy because they do not usually damage healthy cells like chemotherapy does. 8  General Pharmacology : Chemotherapy Act during specific phase of cell cycle (CCS) Active throughout the cell cycle (CCNS) Chemotherapy can be further classified based on the interaction of this class of drugs with the cell cycle. Cell cycle specific drugs (CCS) are very effective for treating hematological cancers (i.e., leukemia, lymphoma). Cell cycle non-specific drugs (CCNS) are effective for both slow growing solid tumors and hematological cancers. 9  General Pharmacology : Drug Resistance (e.g., p-glycoprotein) Mechanisms of Multi-drug resistance (MDR) towards antineoplastic agents. Cancer cells can develop RESISTANCE to drugs by multiple mechanisms including (a) decreased uptake of drug, (b) reduced intracellular drug concentration by efflux pumps, (c) altered cell cycle checkpoints, (d) altered drug targets, (e) increased metabolism of drug and (f) induced emergency response genes to impair apoptotic pathway. P-glycoprotein (P-gp) is an ATP-dependent drug efflux pump for xenobiotic compounds with broad substrate specificity. It is responsible for decreased drug accumulation in multidrug-resistant cells. 10  General Pharmacology : Combo Chemotherapy ¤ Dfn- Combining agents with differing toxicities & mechanisms of action - overcomes limited cell killing by a single anti- neoplastic agent. ¤ 3 ADVANTAGES: 1) Maximal CELL KILL with drugs of different MOA 2) REDUCE INJURY to normal cells by using drugs with non- overlapping toxicities 3) SUPPRESSION of DRUG RESISTANCE ¤ COMMON Chemotherapy Combinations: o MOPP (Mechlorethamine, Vincristine, Procarbazine, Prednisone) o CHOP (Cyclophosphamide, Doxorubicin, Vincristine, Prednisone) o ABVD (Doxorubicin, Bleomycin, Vinblastine, Dacarbazine) For HIGH GROWTH FRACTION cancers (e.g., acute leukemia) phase specific drugs are first used to kill S- or M-Phase cells, and then phase non-specific drugs are used to kill tumor cells in other phases. These two cycles of drugs are repeated once again to kill new cells in G0. MOPP (M stands for mechlorethamine; O for oncovin or vincristine; P for procarbazine and P for prednisone). MOPP is used in patients with Stage III and IV Hodgkin’s lymphoma. This regimen results in high complete response rates (80-90%) with cures in 60% patients. CHOP (C stands for cyclophosphamide; H for hydroxydaunorubicin or doxorubicin; O for oncovin or vincristine; and P for prednisone or prednisolone. CHOP has been used in CLL. ABVD (A stands for adriamycin or doxorubicin; B for bleomycin; V for vinblastine and D for dacarbazine). ABVD has been shown to be more effective and less toxic (incidence of infertility and secondary malignancies) than MOPP for treating patients with Stage III and IV Hodgkin’s lymphoma. This treatment regimen results in high response rates (80-90%) with cures in 60% patients. 11 The most common toxicities produced during chemotherapy are: A- CNS depression & gingival hyperplasia B- Hemorrhagic cystitis & peripheral neuropathy C- Nausea, vomiting, & hair loss D- Pulmonary & cardiac toxicity 12  General Pharmacology: Common Toxicities Because of cytotoxic action on rapidly dividing cancer cells antineoplastic agents are toxic to actively dividing healthy cells. Nausea & Vomiting (40%) Bone marrow depression Alopecia (hair loss) Hyperuricemia (tumor lysis syndrome) Gonads: Oligospermia, impotence, Fetus: Abortion, death, teratogenicity Carcinogenicity Immunosupression Hazards to staff * Gupta, A and Moore JA. (2018) JAMA Oncol. 4(6):895. doi:10.1001/jamaoncol.2018.0613 Bone Marrow Suppression (Myelosuppression)- Chemotherapy drugs often stop the bone marrow from making enough Leucocytes to fight infection, Erythrocytes to carry oxygen, and Thrombocytes to help the blood to clot and prevent bleeding. The manifestations of chemotherapy-induced myelo-suppression include anemia, which causes fatigue; thrombocytopenia, which causes increased bleeding; and neutropenia, which increases the risk of potentially fatal infections, with the degree of that risk related directly to the severity and duration of the neutropenia. Mucositis- chemotherapy induced damage to the epithelium of the oral cavity and GI tract. In the oral cavity, it is due to damage of the rapidly dividing basal cells of the oral mucosa. It occurs in 40% of patients on standard-dose chemotherapy. Alopecia: chemotherapy-induced hair loss occurs with an estimated incidence of 65%. Combination therapy consisting of two or more agents usually produces more severe hair loss, when compared with monotherapy. Generally, hair loss is reversible, with hair regrowth typically occurring after a delay of 3 to 6 months. In some patients, the new growth shows changes in color and/or texture. TUMOR LYSIS SYNDROME occurs in cancer patients with tumors that have a high cell turnover rate and rapid growth rate following chemotherapy treatment. It is characterized by high blood potassium (hyperkalemia), phosphorus (hyperphosphatemia), uric acid (hyperuricemia), low blood calcium (hypocalcemia) and higher than normal levels of blood urea nitrogen (BUN) and other nitrogen containing compounds. The changes in blood electrolytes (i.e., K+ ,, Ca2+, PO4) and metabolites (i.e., uric acid) are a result of the release of cellular contents of dying cells into the bloodstream from breakdown of cells. The most common tumors associated with this syndrome are poorly differentiated lymphomas (e.g., Burkitt’s lymphoma, NHL, ALL, AML, CLL CML). 13 The most common toxicities produced during chemotherapy are: A- CNS depression & gingival hyperplasia B- Hemorrhagic cystitis & peripheral neuropathy C- Nausea, vomiting, & hair loss D- Pulmonary & cardiac toxicity 14 Chemotherapeutic drugs: Major Classes 1. Alkylating Agents (CCNS) 2. Platinum Analogs (CCNS) 3. Antimetabolites (S phase) 4. Taxanes & Vinca alkaloids (M phase) 4. Topoisomerase inhibitor (G1–S phase, and G2-M) 4. 4. Anthracyclines (CCNS) Natural Products 4. Antitumor antibiotics (G2-M phase) 5. Targeted cancer therapies - PARP inhibitors - Tyrosine kinase inhibitors - mTOR pathway inhibitors 6. Cancer immunotherapy - immune checkpoint inhibitors: anti CTLA-4R, anti PD-1 and anti PD-1L - anti CD20 7. Chimeric antigen receptor T-cell therapy (CAR T cells) 8. Bi-specific T-cell engager (BiTE) 15  1. Alkylating Agents (CCNS)* Busulfan, cyclophosphamide, carmustine, lomustine, chlorambucil, dacarbazine, ifosfamide, mechlorethamine MECHLORETHAMINE (Nitrogen Mustard) § Potent vesicant (blistering and tissue necrosis) ---TX: Sodium Thiosulfate (topical or IV) § MOA: Crosslinks DNA strands- disrupts DNA replication & transcription (Guanine) § USE: Hodgkin’s & NHL § ADVERSE EFFECTS: Severe N&V, phlebitis, alopecia, myelosuppression ( Infection), menstrual irregularities, teratogenic & carcinogenic (acute leukemia) CCNS = Cell Cycle Non-Specific Antineoplastic agents. These agents act at ALL PHASES of THE CELL CYCLE. 16 (For illustration purpose only) 17  1. Alkylating Agents (cont’d) CYCLOPHOSPHAMIDE and Ifosfamide § Wide spectrum and NON-VESICANT § MOA: PRO-DRUG metabolized to Aldophosphamide ALDOPHOSPHAMIDE (Crosslinks DNA Strands) & Acrolein (Urotoxic Metab)- TX: Hydrate & MESNA § ADVERSE EFFECTS: Severe N&V, alopecia, amenorrhea, hemorragic cystitis, ( ) sperm count, pulmonary toxicity (HIGH DOSES- organ rejection) Mercaptoethanesulfonate carcinogenic, mutagenic, teratogenic, Leukopenia (MESNA) (low WBC, risk of infection)- (TX: Filgrastim /Sargramostim) Hemorrhagic cystitis is the sudden onset of hematuria combined with bladder pain and irritative bladder symptoms. The amount of blood in the urine can range from a minute amount that occurs occasionally to frank bright red blood that occurs continuously. MESNA (PO or IV) is a medication used to treat patients taking cyclophosphamide or ifosfamide to decrease the risk of bleeding from the bladder. Mechanism: The sulfhydryl group of MESNA reacts with the carbonyl group of acrolein to detoxify the cyclophosphamide metabolite. Leukopenia is a very serious Adverse effect of Cyclophosphamide that can increase infection in cancer patients. Filgrastrim and Sargramostim are Granulocyte Stimulating Factors (G-CSF Receptors) that can be given to patients on cyclophosphamide to boost their immune system by increasing the proliferation of neutrophils or granulocytes and macrophages. Therapy is usually begun 24 to 72 hours after cessation of chemotherapy. 18  1. Alkylating Agents (cont’d) CYCLOPHOSPHAMIDE (cont’d) (Extra slide for explanation) § ADVERSE EFFECTS (cont’d): Leukopenia increased risk of infection- TX: Filgrastim or Sargramostim - FILGRASTIM (granulocyte colony stimulating factor, G-CSF) – stimulates the proliferation & differentiation of neutrophil progenitor cells - SARGRAMOSTIM (granulocyte macrophage colony stimulating factor, GM-CSF) stimulates proliferation & differentiation of granulocytes, macrophages, megakaryocytes & erythrocytes (multilineage) Filgrastrim and Sargramostim are Granulocyte Stimulating Factors (G-CSF Receptors) that can be given to patients on cyclophosphamide to boost their immune system by increasing the proliferation of neutrophils or granulocytes and macrophages. Therapy is usually begun 24 to 72 hours after cessation of chemotherapy. 19  1. Alkylating Agents (cont’d) NITROSOUREAS (Carmustine, Lomustine) § Highly lipophilic (x-BBB) § MOA: NON-ENZYMATIC decompose to alkylate (DNA) & carbamoylate (protein) § USE: Hodgkin’s & NHL, (glioblastomata) § ADVERSE EFFECTS: Severe N&V, delayed myelosuppression (4-6 wks post TX), Pulmonary fibrosis (ONLY Carmustine); nephrotoxicity, hepatotoxicity (Put nitro in your Mustang and travel the globe) 20 2. Platinum Analogs 21  2. Platinum Analogs Cisplatin, Carboplatin, Oxaliplatin Mechanism of action: – Kill cells in all stages of the cell cycle – Similar to alkylating agents: primary N7 of guanine -> strand cross- links Therapeutic use: Cisplatin: Testicular carcinoma, breast, ovarian & bladder cancer. Carboplatin: Advanced Ovarian Carcinoma Oxaliplatin: colorectal cancer (In combination: FOLFOX) Adverse effects: o Nephrotoxicity, myelosuppression, and ototoxicity o Severe emesis o Nephrotoxicity and ototoxicity are less with carboplatin and oxaliplatin o Oxaliplatin: peripheral sensory neurotoxicity 22 Which alkylating agent requires activation and is used with sodium 2- mercaptoethane sulfonate (MESNA)? A-Cyclophosphamide B- Lomustine C- Mechlorethamine D-Carmustine 23 Which alkylating agent requires activation and is used with sodium 2-mercaptoethane sulfonate (MESNA)? A- Cyclophosphamide B- Lomustine C- Mechlorethamine D-Carmustine 24  3. Antimetabolites (A class of agents that are analogues of endogenous folates, purines, and pyrimidines, and that function as inhibitors of the enzymes (E) of nucleotide synthesis) prodrugs -> multiple-step biotransformation -> nucleotide analogues -> inhibit DNA and RNA de novo synthesis a. FOLIC ACID ANALOGS (Methotrexate, Pralatrexate) Methotrexate (MTX) § Uptake into cell (folate carrier) & polyglutamated (trapped) § MOA: Inhibits DIHYDROFOLATE reductase- depletes intracellular pools of tetrahydrofolate (FH4) – essential for purine & thymidylate synthesis of DNA § USE: ALL, Lymphoma, Breast, Head & Neck, bladder cancer Antimetabolite drugs and folate pathway inhibitors are S-PHASE SPECIFIC Inhibitors. In rheumatoid arthritis (RA) and other disorders, MTX is administered as long-term, low-dose therapy, usually 7.5 to 25 mg weekly, unlike its use for treatment of malignant disease, where it is may be administered in a cyclic fashion in doses of 1 gram or more. Methotrexate (MTX) enters the cell through the reduced folate carrier (a) using an endocytic pathway activated by a folate receptor (b). After entering the cell, methotrexate is POLYGLUTAMATED (Glu) by the the enzyme folylpolyglutamate synthase (c). METHOTREXATE and its POLYGLUTAMATES inhibit the enzyme dihydrofolate reductase (d), thereby blocking the conversion of dihydrofolate (FH2) to tetrahydrofolate (FH4). As tetrahydrofolate stores are depleted, thymidylate (TMP) synthesis (e) is reduced,which ultimately inhibits DNA synthesis (f). Long-chain polyglutamates of MTX have the same affinity as MTX for the target enzyme dihydrofolate reductase, but have MARKEDLY INCREASED INHIBITORY effects on both thymidylate synthesis (e) and purine biosynthesis (f), which is required for RNA PRODUCTION. RED CIRCLES: High plasma MTX is used to overcome drug resistance due to increased DHFR or altered enzyme binding (transport). However, high doses are toxic to healthy cells. 25  3. Antimetabolites Methotrexate (MTX) (cont’d) § Adverse Effects: HIGH DOSE (overcome resistance) is toxic to GI and BM cells – Leucovorin (FH4 derivative) used to RESCUE healthy cells; renal tubular obstruction, neurotoxicity (Intrathecal) Pralatrexate (IV ONLY; refractory lymphoma) b. PYRIMIDINE ANALOGS Cytarabine (Cytosine Arabinoside) § Sugar is Arabinose vs. Ribose Deoxycytidine Cytosine Arabinoside § MOA: Incorporates into DNA in place of dCTP --- steric hindrance & inhibition of DNA CHAIN ELONGATION ---- DNA fragmentation § USE: AML, ALL, CML (blast crisis) Rationale for Leucovorin Rescue —MTX has little selectivity for tumor cells, and its effectiveness is limited by toxicity to normal tissue, particularly the gastrointestinal (GI) epithelium and bone marrow. LEUCOVORIN is administered AFTER MTX to ‘rescue’ by REPLETING intracellular FH4 pools of healthy > malignant cells. May compromise anti-tumor activity if it is given too early. It is given 24 to 36 h following methotrexate as part of a total chemotherapeutic plan, where it may protect against bone marrow suppression or gastrointestinal mucosa inflammation. Pralatrexate is an intravenously administered antifolate agent for the treatment of refractory lymphomas (aggressive forms). It has a similar adverse effects profile as methotrexate. Cytarabine (Ara-C) is a S-phase specific antineoplastic agent that is metabolized to ara-CTP, which is incorporated into DNA (vs. deoxycytidine). Incorporated ara-CTP competitively inhibits DNA polymerases to disrupt DNA CHAIN ELONGATION. This interference leads to defective ligation of the newly synthesized DNA fragments resulting in DNA fragmentation. Since DNA polymerases also have a role in DNA repair, ara-CTP also inhibits DNA REPAIR. 26  3. Antimetabolites Cytarabine (cont’d) § Adverse Effects: N&V, dose-limiting myelosuppression with neutropenia and thrombocytopenia, Cerebellar ataxia (HIGH DOSES) § DepoCyt- liposomal prep (intrathecal) for treating Lymphomatous meningitis; Adverse: same as cytarabine 5-Fluorouracil MOA: -interfere with uracil (RNA) and thymine (DNA) production. -used for colorectal cancer and also many other solid tumors: breast, stomach, pancreas, esophagus, liver, head, neck and anus. Adverse Effects: Photosensitivity, Neurotoxicity DepoCyt (Cytarabine liposome) is a long-acting (sustained-release) drug used to treat cancer in the area around the spinal cord (lymphomatous meningitis). It works by slowing or stopping the growth of cancer cells. It increases the half life of cytarabine from lipophilic than Etoposide - faster uptake & longer retention (Renal excretion) § MOA: TOPO II Inhibitor (G1-S) § USE: Hodgkin’s & NHL § Adverse Effects: Etoposide- dose-limiting Leukopenia & mild thrombocytopenia (reversible); CAUTION: Renal disease patients Irinotecan and topotecan: camptothecin MOA:(inhibitor of topoisomerase I (G2-M)) Use Irinotecan: metastatic carcinoma of the colon or rectum Topotecan: ovarian cancer, small cell lung cancer, or cervical cancer Adverse Effects: diarrhea, myelosuppression ETOPOSIDE forms a ternary complex with DNA and Topoisomerase II (which aids in DNA unwinding), prevents re-ligation of the DNA strands, and by doing so causes DNA strands to break. Cancer cells rely on this enzyme more than healthy cells, since they divide more rapidly. Therefore, this causes errors in DNA synthesis and promotes apoptosis of the cancer cell. 34  4. Natural Products d. Anthracyclines Daunorubicin (Daunomycin), Doxorubicin (Adriamycin) isolated from Streptomyces - inhibits topoisomerase II - generation of semiquinone & oxygen free radicals - DNA intercalation -> blockade of DNA and RNA synthesis - alterations in cell membrane transport Use § daunorubicin: acute myelocytic leukemia § doxorubicin: wide variety of solid tumors and hematologic malignancies Adverse effects: myocardial toxicity: potentially fatal CHF Severe myelosuppression -> infection or hemorrhage (CARDIOTOXICITY, TX: dexrazoxane – Fe3+ chelator) The most dangerous Adverse effect of DOXORUBICIN is CARDIOTOXICITY (i.e., dilated cardiomyopathy) that can lead to congestive heart failure (CHF). Symptoms of cardiotoxicity include shortness of breath, swelling ankles/feet, unusual tiredness, and unusual/sudden weight gain. The rate of cardiomyopathy is dose- dependent ranging from 4% to 36%. Eventually, heart failure can result, which carries a 50% mortality rate. The drug dexrazoxane may be used to decrease the risk of doxorubicin's cardiotoxicity in certain cases. Dexrazoxane is an iron chelation drug. By binding to iron complexes (Fe3+) before anthracyclines enter cells, dexrazoxane prevents the formation of the Fe- anthracycline complex that causes free radical release. Dexrazoxane was designated by the FDA as an orphan drug for prevention of cardiomyopathy for children and adults 0 through 16 years of age treated with anthracyclines (doxorubicin, daunorubicin). Dexrazoxane is used to protect the heart against the cardiotoxic Adverse effects of daunorubicin or doxorubicin or other chemotherapeutic agents. 35  4. Natural Products e. Antibiotics (Bleomycin) § Glycoprotein that contains a DNA-binding region & Fe+-binding domain (from Streptomyces verticillus) § MOA: DNA binding- induces DNA SSBs and DSBs via oxygen free radicals – Cell cycle specific (G2) § USE: Hodgkin’s lymphoma, NHL, head & neck cancers § Adverse Effects: PULMONARY FIBROSIS – dry cough, rales, diffuse infiltrates; CUTANEOUS - hyperpigmentation, hyperkeratosis, erythema ulceration; TOXIC MECH: hydrolase activity- lungs & skin - oxygen free radical-induced damage Bleomycins are a group of glycopeptides from Streptomyces which were first isolated in Japan from soil coming out of a coal mine. The bleomycins are widely used chemotherapeutic agents to treat different kinds of cancer (e.g. head and testicular cancer, electrochemotherapy of skin metastasis of breast cancer). Bleomycins form complexes with metals like iron, copper, zinc and cobalt. Especially the iron hydroperoxide complex of bleomycin reacts in a sequence selective manner with DNA leading to double-strand breaks (DSBs). This DNA damage mechanism is the major cause for the activity of bleomycins as chemotherapeutic agents. Bleomycin A2 (Structure in Figure) is a chemical endonuclease which cleaves DS- DNA in a sequence selective fashion by damaging the sugar residues of the DNA via a RADICAL-BASED MECHANISM. It is an antibiotic agent that produces cytotoxicity by induction of free radicals, which causes breaks in DNA, leading to cell death. Its inactivating enzyme, bleomycin hydrolase, is relatively deficient in the lungs and skin, which predisposes to toxic manifestations predominantly in these sites. 36  4. Natural Products f. Enzymes (L-Asparaginase, Pegasparaginase) § L-Asparaginase is protein isolated from E.Coli § MOA: Inhibits protein synthesis – hydrolyzes Asparagine (ASN) in leukemic cells to aspartic acid & NH4 CAUTION: halts cell cycle – interferes other drugs § USE: ALL § Adverse Effects: ANAPHYLAXIS (foreign protein), HYPERGLYCEMIA – reduced ASN- decreases insulin synthesis; BLEEDING- decrease synthesis of clotting factors § Pegaspraginase is PEG form of L-Asparaginase § USE: ALL patients with L-Asparaginase allergy Asparaginase hydrolyzes L-asparagine to L-aspartic acid and ammonia in leukemic cells, resulting in the depletion of asparagine, inhibition of protein synthesis, cell cycle arrest in the G1 phase, and apoptosis in susceptible leukemic cell populations. Asparagine is critical to protein synthesis in leukemic cells; some leukemic cells cannot synthesize this amino acid de novo due to the absent or deficient expression of the enzyme asparagine synthase. Pegasparaginase is typically reserved for cases of asparaginase hypersensitivity. 37 A 43-year-old man with Hodgkin's disease was treated with the MOPP drug regimen (mechlorethamine + vincristine + procarbazine + prednisone) followed by ABVD (adriamycin + bleomycin + vinblastine + dacarbazine). Four years later he develops a cardiomyopathy, followed by CHF. The drug in his treatment regimen that was most likely responsible for causing this is: A- Adriamycin (doxorubicin) B- Bleomycin C- Dacarbazine D- Mechlorethamine E- Prednisone F- Procarbazine G- Vinblastine H- Vincristine 38 A patient being treated with the ABVD drug regimen for Hodgkin's disease presents to the Emergency Department with the chief complaint of shortness of breath upon exertion & a nagging dry cough. A chest Xray indicates the presence of pulmonary infiltration. Which of the drugs in this patient's regimen is the most likely cause & should be discontinued? A- Doxorubicin B- Bleomycin C- Vinblastine D- Dacarbazine 39  5. Targeted Cancer Therapies Olaparib, Niraparib, Rucaparib Mechanism of action: poly (ADP-ribose) polymerase (PARP) inhibitors BRCA1/2 deficient tumor cells cannot repair DNA breaks -> cell death Therapeutic use: variety of cancer with BRCA1/2 mutations 40  5. Targeted Cancer Therapies PROTEIN KINASE INHIBITORS (Imatinib, Ponatinib, Ibrutinib) § ABL1 gene (chromosome 9) normally codes for a tyrosine kinase that regulates cell differentiation & division § CML patients have a 9:22 reciprocal translocation (Philadelphia chromosome) that produces an abnormal tyrosine kinase (Bcr-Abl fusion protein) – dysregulation of differentiation & cell division Philadelphia chromosome. c-Abl oncogene (on 9) translocated to BCR (on 22), which is transcribed into an aberrant protein that drives the disease. The de-regulated tyrosine kinase activity of the BCR-ABL fusion protein has been established as the causative molecular event in chronic myelogenous leukaemia (CML) patients. The Philadelphia chromosome (Ph) is the (9;22) translocation which is transcribed into an aberrant protein that drives the disease. The fused BCR-Abl protein interacts with the interleukin-3 receptor beta(c) subunit. Thus, the BCR-ABL tyrosine kinase is an ideal target for pharmacological inhibition to treat CML. The tyrosine kinase activity of BCR-Abl is elevated relative to wild-type ABL. Since ABL activates a number of cell cycle-controlling proteins and enzymes, the BCR-Abl fusion protein speeds up cell division. It also INHIBITS DNA REPAIR, causing genomic instability and potentially causing the feared blast crisis in CML. SUPPLEMENTAL INFORMATION: In the late 1950s Peter Nowell and David Hungerford found a small abnormality in the chromosomes of patients with chronic myelogenous leukemia (CML). At the time techniques for imaging chromosomes were still crude, but it appeared that a small portion of one copy of chromosome 22 was missing. They dubbed this the"Philadelphia" chromosome, since that is where they discovered it. This provided further weight to the idea that genetic alterations (mutations) could be involved in the occurrence of cancers. 41  5. Targeted Cancer Therapies a. Imatinib § MOA: BCR-Abl Inhibitor- binds to closed conformation of BCR-Abl tyrosine kinase fixing it in a nonfunctional state (key diagnosis: cytogenetic: Philadelphia chromosome) b. Ponatinib § MOA: PAN BCR-Abl Inhibitor - BCR-Abl mutations § USE: Resistant CML § Adverse Effects: Arterial Thrombosis & Hepatotoxicity c. Ibrutinib § MOA: Bruton’s tyrosine kinase (BTK) inhibitor; Blocks B-cell receptor signaling pathway (B-cell Proliferation & migration) § USE: B-Cell Lymphomas § Adverse Effects: NVD, headache, muscle cramps, joint & musculoskeletal pain, rash edema; Pulmonary fibrosis, thrombocytopenia, neutropenia (RARE) Ponatinib was intended to target not only native BCR-ABL, but also ISOFORMS of BCR ABL that carry mutations that confer resistance to treatment with existing tyrosine kinase inhibitors. Bruton’s tyrosine kinase (BTK) is an essential element of the B-cell receptor (BCR) signaling pathway that is required for tumor EXPANSION and PROLIFERATION. BTK is a kinase that plays a crucial role in B-cell development. BTK is mutated in B cell lymphomas. Ibrutinib blocks BCR signaling, removing growth and activation signals and inducing apoptosis. ibrutinib blocks BCR signaling, which drives cells into apoptosis and/or disrupts cell migration and adherence to protective tumour microenvironments. 42 5. Targeted Cancer Therapies PROTEIN TYROSINE KINASE INHIBITORS d. Lapatinib; e. Neratinib Mechanism of action: small molecules inhibitor of the tyrosine kinase activity of human epidermal growth factor receptor -2 (HER-2) inhibit autophosphorylation and downstream pathway inhibit cell proliferation Therapeutic use: breast cancer overexpressing HER2 Adverse effects: fatigue, headache skin reactions gastrointestinal disturbances: diarrhea, nausea, vomiting… hepatotoxicity 43 5. Targeted Cancer Therapies f. Erlotinib g. Gefitinib Mechanism of action: small molecules inhibitor of the tyrosine kinase activity of EGFR inhibit downstream pathway and inhibit cell proliferation Therapeutic use: certain small cell lung cancers advanced metastatic pancreatic cancers. Adverse effects: fatigue, headache, skin reactions, GI disturbances: diarrhea, nausea, vomiting…partial hair loss 44 5. Targeted Cancer Therapies h. Sunitinib i. Sorafenib j. Axitinib k. Cabozantinib Mechanism of action: Inhibitor of VEGF receptors tyrosine kinase: inhibition of angiogenesis Other cell surface receptor tyrosine kinases and intracellular kinases -> decrease in tumor growth, metastatic progression Therapeutic use: multiple GI tumors, kidney and thyroid tumors Adverse effects: hepatic and cardiac toxicity, thrombotic events 45 5. Targeted Cancer Therapies Tyrosine kinase inhibitors Trastuzumab, Pertuzumab human epidermal growth factor receptor 2 protein (HER2) receptor inhibitor Mechanism of action: monoclonal antibody -> extracellular domain of HER-2 inhibit proliferation of cells which overexpress HER-2 Therapeutic use: HER-2-overexpressing cancers Adverse effects: nausea, diarrhea, alopecia cardiotoxicity neurotoxicity: pain, chills, headache, insomnia risk of infections 46 5. Targeted Cancer Therapies Tyrosine kinase inhibitors (indirect) Bevacizumab Mechanism of action: binds to VEGF-and prevents activation of its receptors: -> inhibition of neovascularization -> regression of tumor blood vessels -> reduce tumor growth and metastasis Therapeutic use: Carcinomas of the colon, rectum, breast, and lung Adverse effects: gastrointestinal perforations surgery and wound healing complications, hemorrhage 47  5. Targeted Cancer Therapies mTOR pathway inhibitors Everolimus, Temsirolimus derivative of sirolimus (rapamycin produced by Streptomyces hygroscopicus ) Mechanism of action: bind to FK binding protein (FKBP-12) and inhibit mTOR -> antiproliferative and antiangiogenic actions inhibit vascular endothelial growth factor (VEGF) and hypoxia-inducible factor (HIF-1) expression Therapeutic use: advanced renal cell carcinoma (RCC) Everolimus: prophylaxis of organ rejection in renal transplantation Adverse effects: profound myelosuppression (esp. thrombocytopenia) increased susceptibility to infection & possible development of malignancies Hepatotoxicity, diarrhea, hypertriglyceridemia, headache 48 One of the most common forms of leukemia is Chronic Myelogenous Leukemia (CML). In most cases these leukemic cells contain a chromosomal abnormality that is a "target" for drug therapy that is not seen in non-leukemic white blood cells. A current treatment of choice for this form of cancer is: A- bleomycin B- imatinib C- mechlorethamine D- tamoxifen E- trastuzumab 49  6. Cancer Immunotherapy Ø GOAL: Enhance immune response or alter cell differentiation 1. MONOCLONAL ANTIBODIES (Alemtuzumab,90Y- Ibritumomab tiuxetan, Rituximab) a. Alemtuzumab – a chimeric rat/human IgG variant § USE: B-cell CLL and MS § MOA: Binds CD52 Antigen on B & T lymphocytes causing lysis via two cellular processes: Antibody-Dependent Cell mediated Cytotoxicity (ADCC) Complement-Dependent Cytotoxicity (CDC) ADCC (antibody-dependent cell-mediated cytotoxicity): An immune response in which Monoclonal Antibodies coat cancer cells, making them vulnerable to attack by immune cells (NK, macrophages, neutrophils). CDC (complement-dependent cytotoxicity) is an immune response that kill cancer cells by damaging their membranes without the involvement of cells of the immune system. One or more membrane attack complexes (MAC) causes lethal colloid-osmotic swelling. Complement-dependent cytotoxicity (CDC) is an effector function of IgG and IgM antibodies. When they are bound to surface antigen on a target cell (e.g., B-cells), the classical complement pathway is triggered by bonding to protein C1q to these antibodies, resulting in formation of a membrane attack complex (MAC) and target cell lysis. ADVERSE EFFECTS: Cytopenia, Serious/Fatal Infusion Reactions (hypoxia, pulmonary infiltrates, acute respiratory distress, myocardial infarction, ventricular fibrillation, or cardiogenic shock), Infections. 50  6. Cancer Immunotherapy b. 90Y-Ibritumomab tiuxetan (Radioimmunotherapy) § Binds CD20 antigen on most B-cell neoplasms § USE: B-cell NHL § MOA: a chelator binds 90Y & covalently bound to ibritumomab (Antibody) - induces apoptosis; 90Y: emits b-particles that destroy cells from inside § Adverse Effects: Serious/Fatal Infusion reactions, Severe Mucocutaneous Reactions Ibritumomab tiuxetan binds specifically to the CD20 antigen (human B- lymphocyte-restricted differentiation antigen, Bp35). The CD20 antigen is expressed on pre-B and mature B lymphocytes and on > 90% of B-cell non- Hodgkin's lymphomas (NHL). The chelate tiuxetan, which tightly binds Y-90, is covalently linked to ibritumomab. The beta emission from Y-90 induces cellular damage by the formation of free radicals in the target and neighboring cells. COMMON ADVERSE EFFECTS (Ibritumomab tiuxetan & Rituximab): Serious/Fatal Infusion Reactions (hypoxia, pulmonary infiltrates, acute respiratory distress, myocardial infarction, ventricular fibrillation, or cardiogenic shock), Severe Mucocutaneous Reactions (erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, bullous dermatitis, and exfoliative dermatitis). 51  6. Cancer immunotherapy c. Rituximab, Rituximab-abbs (biosimilar) monoclonal Antibody anti CD20 Mechanism of action: CD20 regulates B-cell cycle initiation at the cell surface: -> activating complement-dependent B-cell cytotoxicity; -> human Fc receptors, mediating cell killing through an antibody-dependent cellular toxicity. Therapeutic use: - chronic lymphocytic leukemia - non-Hodgkin lymphomas B cells - rheumatoid and autoimmune conditions Adverse effects: fatal infusion reactions tumor lysis syndrome severe mucocutaneous reactions viral reactivation: Hepatis B, JC virus: progressive multifocal leukoencephalopathy (PML) 52 Infusion-Related Reactions (IRRs):Common during the first infusion, symptoms can include fever, chills, itching, nausea, and hypotension (low blood pressure). Severe IRRs, such as bronchospasm, angioedema (swelling of the face and throat), and even anaphylaxis, though rare, can occur. These reactions are primarily due to cytokine release upon initial B-cell depletion. Infections: Rituximab causes B-cell depletion, increasing the risk of infections, particularly respiratory infections and reactivation of latent infections such as hepatitis B virus (HBV) and tuberculosis (TB). Progressive multifocal leukoencephalopathy (PML), a rare but severe brain infection caused by the JC virus, has been reported in some cases, particularly in immunocompromised patients. Cardiovascular Effects: Hypotension, arrhythmias, and in rare cases, myocardial infarction, may occur, particularly in patients with pre-existing heart disease. Hematologic Reactions: Rituximab can cause cytopenias (low blood cell counts), particularly neutropenia and lymphopenia, which may require monitoring and management. 52  6. Cancer immunotherapy d. Ipilimumab, Tremelimumab (Immune checkpoint inhibitors) monoclonal Antibody Mechanism of action: binds to the Cytotoxic T-Lymphocyte-Associated Protein 4 (CTLA-4) receptor -> blocks the interaction with its ligands CD80/CD86 expressed on the surface of antigen presenting cells. -> T cell activation and proliferation including tumor infiltrating T-effector cells Therapeutic use: melanoma and metastatic colorectal cancers Adverse effects: (Overactivation of immune response (inflammation)) pneumonitis (cough & shortness of breath) colitis (watery diarrhea) endocrinopathy (hypothyroidism, hypopituitarism) rash 53 53  6. Cancer immunotherapy e. Nivolumab, Pembrolizumab monoclonal Antibody (more specific to tumor) Mechanism of action: Binds to programmed cell death-1 (PD-1) receptor on T-cells -> reverse T-cell suppression and induce antitumor responses (tumor cells) Therapeutic use: large variety of tumors Adverse effects: immune-related adverse events: - Pneumonitis (cough & shortness of breath) - Colitis (watery diarrhea) - Endocrinopathy (hypothyroidism, hypopituitarism) - Rash 54 54  6. Cancer immunotherapy f. Avelumab, Durvalumab, Atezolizumab humanized Monoclonal Antibody Mechanism of action: Binds to the PD-L1 ligand (Programmed Cell Death ligand 1) and prevents its interaction with its receptors PD-1 and B7.1 (CD80) -> blocking PD-1 and B7.1 interactions restores antitumor t-cell function Therapeutic use: Several advanced stage and metastatic carcinoma Adverse effects: immune-related adverse events - pneumonitis (cough & shortness of breath) - colitis (watery diarrhea) - endocrinopathy (hypothyroidism, hypopituitarism) - hepatotoxicity 55 55  Immune checkpoint inhibitors (summary) Mechanism of action of immune checkpoint inhibitors. Notes: T regs depend on the activity of CTLA-4, PD-1, and PD-L1 to induce immunosuppression. ipilimumab and tremelimumab are monoclonal antibodies that inhibit CTLA-4, while nivolumab, pembrolizumab, atezolizumab, and durvalumab inhibit PD-1 and PD-L1. These drugs act by reducing immuno checkpoint activity on a T reg -rich microenvironment, thus diminishing tumor evasion. Abbreviations: T regs , regulatory T-cells; TCR, T-cell receptor; MHC, major histocompatibility complex. 56  7. Chimeric Antigen Receptor (CAR)T-Cell Therapy Isolate T-cells from Patient Genetically modify T-cells in culture Expand modified T-cells Reintroduce modified T-cells into Patient Chimeric antigen receptor T cell (CAR T) therapy is used in the treatment of patients with relapsed or refractory ALL and NHL. It is the first approved GENE THERAPY. CAR T cells are administered by infusion as a single dose or multiple doses over 1-3 days. Patients may be admitted to the hospital for monitoring for treatment-related toxicities. Once inside the body, the CAR-modified T cells expand exponentially and are available to spread throughout the circulation. There they attack targeted cells and differentiate into MEMORY T CELLS. These memory cells may live in the body and potentially establish immune memory. Expansion and persistence in the body are linked to several factors, including co- stimulatory signaling domain (ie, 4-1BB vs CD28), cell lineage/state of differentiation, cell product composition, cell dose, tumor burden, and the conditioning regimen used to provide lymphodepletion and may impact the efficacy and safety profile of CAR T cell therapy. 57  7. CAR T-Cell Therapy: Mechanism* * https://www.youtube.com/watch?v=hAbk7ggXzVg Mechanism involves engineering of a patient’s T-cells so that they recognize tumor cells (e.g., ALL, NHL). The basic objective of CAR T-Cell design is to develop recombinant receptors that contain both a TUMOR ANTIGEN-BINDING (ligand recognition domain –single chain variable fragment, SCFV) and T-CELL ACTIVATING FUNCTIONS (cytotoxic signal peptide- CD 3 zeta). Tumor cells have abnormal T-cell activation due to: 1) Decreased tumor associated antigen, 2) major hisocompatability down-regulation, 3) Co-stimulation down- regulation, 4) TCR signaling blockade. See YouTube video (https://www.youtube.com/watch?v=hAbk7ggXzVg) by Creative Biolabs for a comprehensvie review of CAR T-Cell therapy. 58  7. CAR T-Cell Therapy a. Tisagenlecleucel (Kymriah®) § Autologous T cell immunotherapy § USE: B-cell ALL (relapsing/refractory;