Chapter 23 topoisomerase inhibitors

general oncology from devita presentation

1. TOPOISOMERASE INTERACTING AGENTS

2. Topoisomerases are ubiquitous and essential for all organisms as they prevent and resolve DNA and RNA entanglements and resolve DNA supercoiling during transcription and replication. Topoisomerase I Topoisomerase II

3. Type I Topoisomerase enzymes binds to a DNA molecule, it cuts one strand , simultaneously generating a covalent phosphoester bond between the released 5′ phosphate on the DNA & a tyrosine residue in the enzyme. Formation of phosphotyrosine bond does not require ATP or another source of energy. The free 3′-hydroxyl end of the DNA is held noncovalently by the enzyme. The DNA strand that has not been cleaved is then passed through the single-stranded break. The cleaved strand is then resealed & thus removes negative supercoils .

4. TOPOISOMERSE INTERACTING AGENTS Topoisomerase I Inhibitor: CAMPTOTHECINS: - Irinotecan - Topotecan

5. CAMPTOTHECINS Mechanism of Action: Camptothecins are called topoisomerase "poisons “ Kill cells not by inhibiting topoisomerase catalysis, but by stabilizing the normally transient reaction intermediate in which the enzyme (Top1) is covalently linked to DNA.

6. Addition of camptothecin results in the formation of the ternary complex (Drug-Top1-DNA) & prevents relegation of DNA These lesions are reversible and disappear with removal of the drug Collision between advancing replication fork with the ternary complex leads to DNA damage and cell death. This may also account for S phase specificity of cell cycle of camptothecin cell toxicity.

7. Mechanism Of Resistance: Decreases Expression of top I Mutation in top I enzyme with decreased affinity for the drug. Increased expression of multidrug resistance phenotype with over expression of P glycoprotein. Results in enhanced efflux of drug and decreased intracellular accumulation of drug Decreased formation of the cytoxic metabolite SN 38 through decreased activity and /or expression of carboxylesterase enzyme.

8. IRINOTECAN It is a prodrug Active metabolite : SN-38 Pharmacokinetic: 50 % protein bound, SN-38 shows extensive protein binding : 95 % Half life (t1/2) irinotecan : 6-12 hrs, SN-38: 10-20 hrs Renal excretion accounts for 25 % of administered dose Remaining is eliminated by hepatic metabolism and biliary excretion DOSE : Administered intravenously as a weekly infusion of 125 mg/m2 for 4 weeks with a 2 -week rest period or, alternatively, 240 to 350 mg/m2 every 3 weeks

9. USES : 1. Stage IV or relapsed colorectal cancer

10. 2. Small Cell Lung Cancer - Cisplatin / Carboplatin + Irinotecane combination in extensive stage 3. Non small cell lung cancer 4. Locally Advanced or Metastatic Gastric cancer - FOLFIRI regimen as first line therapy - Irinotecane as single agent ( preffered ) or in combination with other cytotoxic drugs ( cisplatin or docetaxel or Capcetabine ) are used in second line or third line settings. 5. Recurrent or Metastatic Cervical cancer : Second line therapy

11. Side effects : Myelosupression Diarrhea : two mechanism : 1. Acute Cholinergic Effects (< 24 hrs) ----- treatment : ATROPIN (0.25- 1mg I/V) 2. Mucosal Cytoxicity : ( > 24 hrs) ----- treatment : LOPERAMIDE (4mg P/O as loading dose  2 mg every 2 hrs  can be stopped if pt. is diarrhoea free for 12 hrs) SN- 38 is glucuronidated in the liver by UGT 1 A 1 , and deficiencies in this pathway may increase the risk of diarrhea and myelosuppression Nausea, vomiting, Mild Alopecia Dose adjustment is recommended for: Patients who are homozygous for UGT1A1 * 28 allele Hepatic dysfunction

12. TOPOTECAN Pharmacokinetics: 30 % protein bound 40% oral bioavailability; Topotecan penetration into the CNS is greater than that of other camptothecins , CSF drug levels reach 30 % of plasma levels T1/2 : 2-3 h (IV) or 3-6 h (oral) Renal excretion is the major route of elimination of the drug and its metabolites Dose Adjustment: 50 % dose reduction is recommended for patients with mild renal impairment ( creatinine clearance 40 to 60 mL /min). Renal Dysfunction

13. Uses Metastatic ovarian cancer Cervical cancer (Stage IV B, recurrent disease) Small cell lung cancer Non-small cell lung cancer AML, MDS Dose : Administered intravenously at a dose of 1.5 mg/m2 as a 30-minute infusion daily for 5 days, followed by a 2-week period of rest

14. Side effects: Myelosuppression M/C (especially neutropenia ) Thrombocytopenia and moderate to sever anaemia are less common Nausea , vomiting, Diarrhoea , Low grade fever, fatigue, alopecia, skin rash---- Milder toxicities Microscopic Hematuria (< 10 %)

15. New formulations of Camptothecin New formulations of camptothecin conjugates and analogs are currently in clinical development in an effort to improve the therapeutic index

16. Topoisomerase II Inhibitor : ANTHRACYCLINS : - Doxorubicin - Liposomal Doxoruibicin - Daunorubicin - Epirubicin - Idarubicin ANTHRACENEDIONES : - Mitoxantrone DACTINOMYCIN EPIPODOPHYLLOTOXINS : - Etoposide - Teniposide DNA Intercalaters Non- Intercalaters

17. Type II topoisomerase enzymes function as homo- or heterodimers and require ATP for catalysis. Topoisomerase dimer binds to DNA, forming a double-strand DNA break in which the proteins are covalently bound to the 5 ' end of broken DNA strands to form the Top2 cleavable complex. In this state the protein dimer is stabilized, forming a gate in the DNA through which a second DNA double-helix strand can pass in an energy-dependent fashion and finally broken DNA is relegated DNA is unable to relegate,leading to double-strand DNA breaks & cell death

18. ANTHRACYCLINS Anthracyclines are natural products derived from Streptomyces peucetius variation caesius MOA : Intercalation in the DNA : The drugs insert nonspecifically between adjacent base pairs and bind to the sugar-phosphate backbone of DNA. This causes local uncoiling and, thus, blocks DNA and RNA synthesis Inhibits transcription: Inhibits topo II by forming a cleavable complex with DNA and topII . Creates uncompensated DNA helix torsional tension, leading to eventual DNA breaks. The quinone structure of anthracyclines enhances the catalysis of oxidation-reduction reactions, thereby promoting the generation of oxygen free radicals , which may be involved in antitumor effects as well as toxicity associated with these drugs .

19. Mechanism of Resistance Increased expression of the multidrug resistance gene with elevated P glycoprotein levels, which leads to incresed drug efflux and decreased intracellular drug accumulation Decrease expression of top II Mutation in top II with decrease binding affinity for doxorubicin Increase expression of sulfhydryl proteins, including glutathione and glutathione dependent protein

20. Doxorubicin & liposomal Doxorubicin Doxorubicin differs from daunorubicin by a single hydroxyl group at C 14 Doxorubicin is also available in a polyethylene glycol (PEG) ylated liposomal form--  Liposomal Doxorubicin Protected from chemical and enzymatic degradation, reduced plasma protein binding, and decreased uptake in normal tissues. Penetrates tumour tissue in to which doxorubicin is released.

21. Pharmacokinetic : 75 % of doxorubicin and its metabolites are bound to plasma protien . Half life T1/2: 20 to 48 hrs Metabolized in the liver to active hydroxylated metabolite doxorubicinol and 40-50 % of drug eliminated via bile excretion in feces . Urinary excretion of doxorubicin and other anthracyclines is low, comprising less than 10 % of the administered dose. Dose Adjustment : Doxorubicin dose may be reduced by 50 % for plasma bilirubin concentrations ranging from 1.2 to 3.0 mg/ dL , by 75 % for values of 3.1 to 5.0 mg/ dL , and withheld for values greater than 5 mg/ dL .

22. USES : Breast Cancer Adjuvant CT Regimen in Her2 Negative Disease All regimens are Cat 1

23. Adjuvant CT Regimen in Her2 Positive Disease

24. USES REGIMENS Hodgkins Lymphoma ABVD (M/C) BEACOPP, Escalated BEACOPP Standford V Non Hodgkins Lymphoma (DLBCL) R- CHOP ( Rituximab , Cyclophosphamide , Hydroxyldaunrubicin i.e doxorubicin, Vincristin , Prednisone) Ewings Sarcoma Localized disease : VAC/ IE ( Vincrist , Doxo , Cyclo alternating with ifosfamide , Etoposide ) Metastatic : VAdriaC Osteosarcoma (first line therapy for primary / Neoadjuvant / Adjuvant / Metastatic) Cisplatin and Doxorubicin MAP (high dose Mtx , doxorubicin, cisplatin ) MAP + ifosfamide Muscle invasive bladder cancer ( neoadjuvant / adjuvant) Metastatic bladder cancer ddMVAC ( Mtx , Vinblastin , Doxorubicin, Cisplatin ) with Growth factor support

25. Other uses : ALL, AML, CLL, Non small cell lung cancer NHL, Mantle Cell Lymphoma, Mycosis fungoides , Gastric Ca., Thyroid Ca. Nephroblastoma , Neuroblastoma , Wilms Tumour Recurrent ovarian cancer (After Failure of platinum based chemotherapy) Carboplatin + Liposomal Doxorubicin (CAT 1) Advance Kaposis Sarcoma Liposomal Doxorubicin (Response rate 51-76 %) Multiple Myeloma Liposomal Doxorubicin in combination with Bortezomib

26. DOSE: - Doxorubicin : 30 to 75 mg/m2 every 3 weeks intravenously - Liposomal Doxorubicin : 20 to 60 mg/m2 every 3 weeks intravenously

27. SIDE EFFECTS: Myeosuppresion Mucositis Alopecia (usually reversible in 3mths after termination of treatment) Nausea & vomiting Diarrhea Potent vesicant : Extravasation can lead to sever necrosis of skin and local tissues (Longer infusions are recommended by Central Venous Catheter) Acute Treatment : Ice & dimethyl sulfoxide Extensive treatment : Surgical debridemnt and skin grafts (sever cases) Flare reaction ( erythema ) at infusion site Red orange discolouration of urine, Hyperpigmentation of nails Radiation Recall (inflammatory reaction at sites of previous radiation and can lead to pericarditis , Pleural effusion, skin rash) Secondary Leukemia Cardiac toxicity

28. Liposomal Doxorubicin : Side effects Associated with less nausea / vomiting and mild myelosuppression . Hand-foot syndrome Acute infusion reaction manifested by flushing, dyspnea , edema , fever, chills, rash, bronchospasm and hypertension

29. DAUNARUBICIN Daunorubicin is similar in structure doxorubicin More lipid soluble then doxorubicin Pharmacokinetic: Extensively binds to plasma protein (60 -70 %) Metabolized in liver and also undergoes substantial elimination by the kidneys . Half life (t1/2) : 18.5 hrs Dose reduction for hepatic and renal dysfunction is recommended

30. Uses FDA approved : ALL and AML. Also used in Ewing's sarcoma, nephroblastoma , CML, NHL. Dose : administered intravenously 30 to 45 mg/m2 on 3 consecutive days in combination chemotherapy . Side effects : Myelosuppression , Nausea, vomiting, diarrohea Mucositis , Alopecia (usually reversible within 5-7 weeks after termination of treatment) Cardiac toxicity ( Cummulative dose of > 550 mg/ m2) Strong Vesicant

31. EPIRUBICIN DOSE : 60 to 120 mg/m2 every 3 to 4 weeks given intravenously (Incidence of N/V , alopecia, cardiac toxicity is less with epirubicin compared to doxorubicin)

32. Idarubicin Idarubicin is a synthetic derivative of daunorubicin , lacking the 4-methoxy group . Uses : AML , ALL DOSE : 12 mg/m2 given I/V for 3 consecutive days . Idarubicin has similar toxicities as daunorubicin , including myelosuppression , nausea, vomiting, alopecia, cardiac toxicity, and tissue necrosis in cases of extravasation 50 % dose reductions are recommended for Sr bilirubin of 2.6 to 5 mg/ dL and it should not be given if the bilirubin is greater than 5 mg/ dL .

33. CARDIAC TOXICITY Acute cardiotoxicity : Reversible Develops during or within days of anthracycline infusion Clinical signs include tachycardia, hypotension, electrocardiogram changes, and arrhythmias-  may result in transient congestive heart failure ( CHF) Incidence of which has been significantly reduced by slowing doxorubicin infusion rates. It is rarely a fatal

34. Chronic cardiotoxicity : It is the most common type of anthracycline damage and is irreversible. Dose dependent Peaks at 1 to 3 months but can occur even years after therapy. Clinical signs include fatigue, dyspnea on exertion, orthopnea , sinus tachycardia, S3 gallop rhythm, pedal edema /pleural effusions, and elevated jugular venous distention …. dilated cardiomyopathy with CHF Fatal

35. Mechanism of Anthracycline Cardiotoxicity The production of free radicals generated during cardiomyocyte anthracycline metabolism results in membrane lipid peroxidation , with the consequent activation of the extrinsic and intrinsic apoptotic pathways. Free radicals are generated by enzymatic reduction of the anthracycline quinone ring and by formation of iron anthracycline complexes . The intrinsic antioxidant defense of the cardiomyocyte is more limited than other organs, leading to its apparent selective toxicity profile.

36. Incidence of anthracycline cardiomyopathy depends on Cumulative dose: Cummulative dose Incidence of Cardiotoxicity Doxorubicin : 400 -450 mg / m2 Daunarubicin : 900 mg/m2 Epirubicin : 800 -935 mg/ m2 Idarubicn : 223 mg / m2 5 %

37. Predisposition to cardiac damage includes Previous H/O coronary artery disease, other valvular or myocardial conditions, and hypertension Mediastinal irradiation Older ( > 70 years) or younger ( < 4years ) age, Prior use of anthracyclins or other cardiac toxins Co administration of other chemotherapy agent ( eg Paclitaxel , cyclophosphamide ) Concurrent trastuzumab appears to potentiate anthracycline cardiotoxicity

38. Sequential administration of paclitaxel  doxorubicin in breast cancer patients is associated with cardiomyopathy at total doxorubicin doses above 340 to 380 mg/m2, whereas the reverse sequence of drug administration did not yield the same systemic toxicities Doses of epirubicin below 1,000 mg/m2 and daunorubicin below 550 mg/m2 are considered safe. Liposomal doxorubicin is associated with less cardiac toxicity. In pediatrics , it is important to be aware that conduction disturbances ( second-degree atrioventricular block) and arrhythmias ( both supraventricular and ventricular) may be detected during therapy, but have no known acute/chronic consequence.

39. Monitoring of Cardiac function during treatment: Electrocardiography (Include sinus tachycardia, low voltage, poor R wave progression, and nonspecific T wave changes ) Serial non invasive monitoring of LVEF: A. Echocardiography : Left ventricular diastolic dysfunction  left ventricular systolic dysfunction, particularly affecting the septal motion. With full development of cardiomyopathy , there is global hypokinesis and muscle wall thinning. B. Radionuclide scans. (MUGA Scan) Biomarkers: Sr cardiac troponin T levels : measure of active myocardial myocyte necrosis Brain natriuretic peptide levels : peptide synthesized in the ventricles correlate with degree of heart failure

40. Percutaneous Endomyocardial biopsy (Rare): Multifocal areas of patchy and interstitial fibrosis ( stellate scars) and occasional vacuolated myocardial cells ( Adria cells) Myocyte hypertrophy and degeneration, loss of cross-striations, and absence of myocarditis are also characteristic of this diagnosis

41. Numerous studies demonstrate the danger of embarking on anthracycline therapy in patients with underlying cardiac disease (e.g., a baseline LVEF of less than 50 % ) and of continuing therapy after a documented decrease in ejection fraction by more than 10 % ( if this decrease falls below the lower limit of normal ) . A low LVEF is a contraindication for anthracycline therapy

42. Schwartz  et al . have developed a monitoring algorithm with scheduled frequent ejection fraction measurements, that, when used, has demonstrated a four-fold reduction in the risk of congestive heart failure Schwartz et al Am J Med 1987; 82:1109. High Risk : known heart disease, ECG Abnormalities, RT, Cyclophosmaide therapy or EF < 40 %

43. In a small prospective study, Nousiainen et al. reported that it was possible to distinguish patients likely to develop cardiactoxicity from others by LVEF measures at baseline and at 200 mg/m2 doxorubicin. A fall of 10 % or more at this low cumulative dose had 72 % specificity and 90% sensitivity in detecting later cardiotoxicity

44. Prevention of Cardiotoxicity Altering Infusional Protocol When doxorubicin is given by a low-dose weekly regimen ( 10 to 20 mg/m2/wk) or by slow continuous infusion over 96 hours, cumulative doses of more than 500 mg/m2 can be given Alternate anthracycline derivatives Liposomal analogoues ( liposomal Doxorubicin) Angiotensin -converting enzyme inhibitors, β -blockers, statins and diuretics are used

45. Dexrazoxane Dexrazoxane is FDA approved to prevent anthracycline induced cardiotoxicity in women with metastatic breast cancer who have received a total cumulative dose of doxorubicin of 300 mg/m2 & would benefit from continued treatment. MOA : Dexrazoxane chelates iron and copper, thereby interfering with the redox reactions that generate free radicals and damage myocardial lipids Recommended dose is to give dexrazoxane I.V. 30 minutes before doxorubicin at a ratio of dex:dox of 10:1

46. MITOXANTRONE Mitoxantrone is the only clinically approved anthracenedione . MOA : DNA intercalator and stabilizes the Top2- DNA complex, leading to double-strand DNA breaks Relative to anthracyclines , mitoxantrone is less likely to undergo oxidation-reduction reactions and form free radicals, thereby decreasing its cardiac toxicity. Pharmacokinetic: Extensively bound to plasma protein (78 %) Metabolized in liver by microsomal P450 system Elimination is mainly by H-B route , 25 % is excreted in feces Renal clearance 10 % Half life (t1/2 ) : 75 hrs (median)

47. USES : Advanced, Hormone refractory prostate cancer (used in combination with pednisone as initial therapy) AML ALL Metastatic breast cancer Liver cancer NHL

48. Toxicities: Myelosuppression Nausea,vomiting , alopecia, and mucositis are less common compared to doxorubicin. Cardiac toxicity is generally seen at cumulative doses greater than 160 mg/m2 Vesicant Blue discolouration of fingernails ,sclera and urine (for 1-2 days after treatment) Use with caution in pts with abnormal LFT (dose modification should be considered)

49. Dactinomycin Actinomycins were the first anticancer antibiotics isolated from Streptomyces The derivative presently in use is dactinomycin . Structurally, dactinomycin is a " chromopeptide ," consisting of a planar phenoxazone ring (which produces the yellow-red color of the drug), attached to two peptide side chains . MOA : Dactinomycin can intercalate into DNA between adjacent guanine-cytosine bases, thereby poisoning Top2 and leading to lethal double-strand DNA breaks.

50. Mechanism of resistance : Increased expression of the multidrug resistant gene with elevated P-glycoprotein levels leads to increase drug efflux and decrease intracellular accumulation Pharmacokinetic Clinical pharmacology not well characterized Metabolized only to some extent Most of the drug is eliminated in unchanged form by biliary (50 %) and renal (20 %) excretion Half life (T1/2) : 36 hrs

51. USES: Wilms tumour Rhabdomyosarcoma Ewings Sarcoma Gestational trophoblastic disease Germ cell tumour

52. Side Effetcs : Myelosuppression , Nausea, vomiting, Alopecia, Erythema , and acne. Radiation recall Veno -occlusive disease of the liver Severe tissue necrosis in cases of extravasation .

53. EPIPODOPHYLLOTOXIN: ETOPOSIDE Glycoside derivatives of podophyllotoxin , an antimicrotubule agent extracted from the mandrake plant Primarily function as Top2 poisons rather than through antimicrotubule mechanisms MOA : Inhibits Top II by stabilizing the Top II DNA complex and preventing unwinding of DNA Cell cycle specific agent with activity in late S and G2 phase

54. Mechanism of resistance : Increased expression of the multidrug resistance gene with elevated P glycoprotein levels, which leads to increased drug efflux and decreased intracellular drug accumulation Decrease expression of top II Mutation in top II with decrease binding affinity to drug Enhanced activity of DNA repair enzyme

55. Pharmacokinetic: 90 – 95% is protein bound mainly to albumin 25-75 % Bioavailability (I/V) Half life t1/2 : 3-12 hrs Majority of etoposide is cleared unchanged by the kidneys (40-60 %) 25 % dose reduction is recommended in patients with a creatinine clearance of 15 to 50 mL /min. And 50 % in patients with a creatinine clearance less than 15 mL /min.

56. Etoposide USES Small cell carcinoma Testicular carcinoma USES Regimens Small Cell Lung Carcinoma Testicular Cancer (First line therapy) Metastatic testicular ca Oral Etoposide

57. USES Regimens Hodgkins Lymphoma BEACOPP Escalated BEACOPP Stanford V Ewings Sarcoma (Local / metastatic) VAC/IE ( Vincristine , Doxorubicin, Cyclophosphamide alternating with ifosfamide , Etoposide ) VIDE Osteosarcoma : Second line (relapsed/ refractory/ metastatic ) Etoposide in combination with cyclophosphamide / Ifosfamide and other cytotoxic drugs Other uses includes : ALL, AML NHL, Primary cutaneous T cell Lymphoma Myelodysplastic syndrome Multiple Myeloma Endometrial, Ovarian germ cell tumour, Gestational Trophoblastic Neoplasm, NSCLC, Retinoblastoma

58. SIDE EFFECTS Myelosuppression (Thrombocytopenia is less common than leukopenia ) Mild to moderate nausea, vomiting, diarrhea , mucositis , and alopecia , metallic taste during infusion of drug Among the Top2 poisons, epipodophyllotoxins are associated with the greatest risk for development of secondary malignancies  4% 6-year cumulative risk. Myelomonocytic (FAB M4 ) and monoblastic (FAB M5 ) variants of AML are the most common presentations of epipodophyllotoxin -related leukemia resulting from balanced translocations affecting the breakpoint cluster region of the MLL gene at chromosome 11 q23

59. Teniposide Teniposide contains a thiophene group in place of the methyl group on the glucose moiety of etoposide USES : FDA approved for refractory pediatric acute lymphoid leukemia (165 – 250 mg/ m2 weekly or twice weekly) Also used in adult neuroblastoma and NHL Dose: Adults: ranges from 30 to 100 mg/m2 intravenously, used either alone or in combination chemotherapy Side Effects : Same as Etoposide Associated with greater hypersensitivty reaction Dose adjustment for hepatic and renal dysfunction

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