cytotoxic agents : class 1: alkylating drugs, class 2: anti-metabolites

1. B Y
D R . H AR S H I K A PAT E L
M E D B 3 3 5 B AS I C P H AR M A C O L O G Y AN D
TO X I C O L O G Y
CANCER CHEMOTHERAPY:
ALKYLATING AGENTS
&
ANTIMETABOLITES

2. ALKYLATING AGENTS
History
• Sulfur mustard gas – potent vesicant
• Clinical trials with SMG – penile tumor
• Gillman and his colleagues work on nitrogen mustard
against murine lymphoma
• In 1942, clinical trials began  pt with lymphoma 
treated by i.v. NM
• Launching modern era of cancer chemo

3. ALKYLATING AGENTS
• Nitrogen Mustards (MCI) –
Meclorethamine, Melphalan,
Chlorambucil, Cyclophosphamide,
Ifosfamide (M2C2I )
• Ethyleneimine : Thio-tepa
• Alkyl Sulfonate: Busulfan
• Nitrosoureas – Carmustine,
lomustine, Streptozocin
• Triazine /DNA methylating drugs -
-procarbazine,temozolomide,
dacarbazine
Platinum
compound……
Cisplatin
Carboplatin
Oxaliplatin
Other group
of cytotoxic
drugs

5. Highly reactive
intermediate –
carbonium ions

6. meclorethamine
melphalan
Chlorambucil
Structure activity
relationship

7. MECHANISMS OF RESISTANCE OF
ALKYLATING AGENTS
• Acquired resistance –to alkylating agents
• Mechanism: involved in
 Inc’ capability to repair DNA lesions,
 Dec’ permeability of the cell to drug,
 Inc’ production of glutathione* (cause
higher metabolism rate)

8. PHARMACOLOGICAL ACTIONS
• Cytotoxic action – vesicant property
• Hemopoietic system highly susceptible
• Chlorambucil
more against lymphoid series
• Busulfan
more against myeloid series
Epithelial tissues, hair follicles
Spermatogenesis , Foetopathic effect
• Immunosuppressant action
• Miscellaneous – Severe nausea & vomiting – i.v. – 5HT 3
rec antagonist – prior to apply
• Known as radiomimetic drugs

9. NITROGEN MUSTARDS
• Mechlorethamine
• Melphalan
• Chlorambucil
• Cyclophosphamide
• Ifosfamide

10. MECHLORETHAMINE (MUSTINE)
• Very irritant drug (potent vesicant)
• Dose = 0.4 mg/kg single or divided i.v.
• PK: highly unstable, solution prepare before administration
• Uses – Haematological cancers , lymphomas , solid tumors – Hodgkins
as part of MOPP
• CML, CLL
• MOA: slide 5
• Adverse effects
Anorexia, nausea, vomiting (rx by antiemetic with dexamethasone)
Bone marrow depression, aplasia
Menstrual irregularities
Latent viral infection (herpes zoster) - supressed immunity
Extravasation – (infiltrate with isotonic sod. Thiosulfite to inactivate)
• Estramustine is a combination of estradiol with nitrogen mustard.

12. MELPHALAN
• Phenylalanine derivatives (nitrogen mustard)
• PK: orally active, plasma conc varies from pt to pt due
to variation in intestinal absorption and metabolism
• Very effective in MULTIPLE MYELOMA
• Less irritant locally , less alopecia
• Dose: 0.25 mg/kg daily for 4 days every 4-6 weeks
Dose should be adjusted by monitoring platelets and
WBCs count
• Adverse Effects :
– Bone marrow Depression: Infections (low WBC), low platelets
count bleeding
– pancreatitis
-- N/V, oral ulceration

13. CYCLOPHOSPHAMIDE
• Most commonly used alkylating
agent as a prodrug
• Cytotoxic effect generate after
formation of their alkylating
species
• Broad spectrum: used single/
as part of a regimen
PK: both cyclophosphamide &
ifosfamide orally active
• After administration, parent drug
excreted into feces by biliary
transporter

15. Mesna* used with cyclophosphamide and ifosfamide to
decrease the risk of haemorrhagic cystitis (in high dose
regimen)

16. USES OF CYCLOPHOSPHAMIDE
• Neoplastic conditions
– Hodgkins and non hodgkins lymphoma
– ALL, CLL, Multiple myeloma
– Burkits lymphoma
– Neuroblastoma , retinoblastoma
– Ca breast , adenocarcinoma of ovaries
• Non neoplastic conditions
– Control of graft versus host reaction
– Rheumatoid arthritis
– Nephrotic syndrome

17. ADVERSE EFFECTS
• Hemorrhagic cystitis,
• alopecia,
• nausea & vomiting,
• SIADH
• hepatic damage : Veno-occlusive diseases
Dose:
2-3 mg/kg/day oral
10-15 mg/kg IV every 7-10 days
It can be administered thr’ IV, IM, IP, intrapleurally,
Intraarterialy, directly into tumor
Effects on the germ cells:
amenorrhea,
testicular atrophy,
aspermia,
sterility

18. IFOSFAMIDE
• Congener of cyclophosphamide
• Longer half life than cyclophosphamide
• Less alopecia and less emetogenic than
cyclophosphamide
• Can cause hemorrhagic cystitis and severe neurological
toxicity (at high dose)*
• Used for germ cell testicular tumors and adult sarcomas

19. CHLORAMBUCIL (LEUKERAN)
• Bifunctional alkylating agent*
• Slowest acting and least toxic alkylating agent
• Main action on lymphoid series produces marked lympholytic
action
• DOC for long term maintenance therapy of CLL
• Dose: 0.1-0.2 mg/kg daily for 3-6 weeks then 2 mg daily for
maintenance
• AD: moderate GI upset and haematologic toxicity

20. Mustard agents
Drugs Dose Acute toxicity Delayed toxicity
Mechlorethamine 0.4 mg/kg IV
in single or
divided doses
Nausea and
vomiting,
myelosuppression
Moderate depression of
peripheral blood count;
excessive doses produce
severe bone marrow depression
with leukopenia,
thrombocytopenia, and
bleeding; alopecia and
hemorrhagic cystitis
occasionally occur with
cyclophosphamide; cystitis
can be prevented with adequate
hydration; busulfan is
associated with skin
pigmentation, pulmonary
fibrosis, and adrenal
insufficiency
Melphalan 0.25 mg/kg/d
orally for 4
days every 4–
6 weeks
Nausea and
vomiting,
myelosuppression
cyclophosphamide 3.5–5 mg/kg/d
orally for 10
days; 1 g/m2
IV as single dose
Nausea and
vomiting,
myelosuppression
Chorambucil 0.1–0.2 mg/kg/d
orally; 6–12
mg/d
Nausea and
vomiting,
myelosuppression
Ifosphamide Nausea and
vomiting,
myelosuppression

21. THIOTEPA
• Triethylene phosphoramide (TEPA)
• Both thiotepa and its desulfurated primary metabolite, TEPA 
rapidly converted by hepatic CYPs, form DNA cross-links 
aziridine rings open after protonation of the ring-nitrogen 
reactive species which gives cytotoxic effects
• Active intravesicular agent
• Topically applied in superficial bladder cancer
• Not well absorbed orally so given IV
• Highly neurotoxic leads to seizure and coma
uses

22. BUSULFAN (MYLERAN)
• Depresses bone marrow with selective action on myeloid
series
• Primarily used in Chronic myelogenous leukemia
• In high dose regimen
2-6 mg/day, t1/2 : 2-3 hours
• Adverse effect:
– Interstitial pulmonary fibrosis
– Veno-occlusive disease of liver
– Hyperuricaemia
– Sterility
--CNS toxicities: seizure – anti convulsant drug*  always
useful in high dose regimen of buslfan (0.8mg/kg, every 6hours
for 4 days)

23. NITROSOUREAS
• Highly lipid soluble, Cross BBB
• No cross resistance with other alkylating
agents
• Required biotransformation (by
nonenzymatic decompositions)
• Metabolites: bifunctional activities*
ACTION: cross linking thr alkylation of DNA
• More effective against plateau phase than
expontially growing phase
• PK: orally active (lomustine)
• Metabolites : peak plasma level appear
within1-4 hrs
• CNS cons reach 30-40 % (present activity)
• Initial t1/2: 6hrs ; second t1/2 : 1-2 days

24. CONTD…
Uses : Meningeal / Brain tumours
Dose :150-200 mg/m2 BSA every 6 wks
(Carmustine)
Adverse Effects:
• Delayed bone marrow suppression
• Visceral fibrosis, renal damage
Streptozocin : sugar containing nitrosourea
• Minimal BM toxicity
• treatment of insulin-secreting islet cell carcinoma
of the pancreas

25. TRIAZENES
• Procarbazine (methylhydrazine), oral drugs
• Combination regimens to rx Hodgkin's & non Hodgkin's lymphoma, brain
tumor
• leukemogenic , teratogenic, mutagenic
MOA: uncertain, still these are mechanism works:
1. inhibits the synthesis of DNA, RNA, and protein; prolongs interphase; and
produces chromosome breaks.
2. Oxidative metabolism  by microsomal enzymes  azo-procarbazine and
H2O2 DNA strand scission.
3. Variety of this drug’s metabolites have cytotoxic activity
one metabolite, is act as MAO inhibitor *
• Higher risk to cause secondary cancer as a form of acute leukemia,
• Even it carcinogenic activity higher than other alkylating agents

26. TRIAZENES
Dacarbazine
Parenterally active, non schedule-
dependent
Use : malignant melanoma , Hodgkin's
diseases , soft tissue sarcoma
ADR: Nausea, vomiting, flu-like symptoms,
neuropathy and myelosuppression
• Metabolic activation by liver microsomal
enzymes oxidative N-demethylation to the
monomethyl derivative
• Spontaneous decomposes to 5-
aminoimidazole-4-carboxamide (Excreted) and
diazomethan
• Later metabolite forms methyl carbonium ion
which believes that to be cytotoxic

27. TRIAZENE
Temozolamide
• New alkylating agent
• Approved for use against treatment-resistant gliomas and
anaplastic astrocytoma's*
• Rapidly absorbed after oral absorption & crosses BBB
• Unlike dacarbazine, temozolamide:
does not require cytochrome P450 system for metabolic
transformation  chemical transformation under normal
physiological pH
property of inhibiting the repair enzyme, O6-guanine-DNA-
alkyltransferase
taken orally and has excellent oral bioavailability
• taken for five consecutive days and repeated every 28 days
• same toxicity profile as previous drug

28. ALTRETAMINE
• Home exercise..?

29. PLATINUM COORDINATION COMPLEXES
• Inorganic metal complex
• Serendipitous drugs*
• Broad activities
• Synergistic action with other anticancer agents
• Treat ovarian, head neck, bladder, esophagus, lung and
colon cancers

30. CISPLATIN

31. N7 of guanine adenine and
cytosine
Form plt adducts
Replication and transcription

32. CISPLATIN
• Uses
• Testicular cancer (85% - 95 % curative )
• Ovarian cancer, bladder cancer
• Other solid tumors: lung (small & non small), esophagus,
gastric
• nonseminomatous testicular cancer (combination regimens)
Adverse effects
– Emesis
– Nephrotoxicity (red’ by hydration with i.v. saline infusion /
saline & mannitol/ other diuretics)
– Peripheral neuropathy
– Ototoxicity

33. CARBOPLATIN
• Second generation platinum analogues with Better
tolerability
• Nephrotoxicity , ototoxicity , neurotoxicity  low
• Less emetogenic, but thrombocytopenia and leukopenia
may occur (dose liming toxicities)
• Less plasma protein binding
• Vigorous i,.v. hydration not required
• Used in place of Cisplatin
• Use: solid tumours
– primarily in ovarian cancer of epithelial origin
– Squamous cell carcinoma of head and neck

34. OXALIPLATIN
• 3rd generation diaminocyclohexane platinum analogues
• No cross-resistant to cancer cells that are resistant to
cisplatin or carboplatin on the basis of mismatch repair
defects
• Approved for : second-line therapy in metastatic
colorectal cancer  following treatment  5-
fluorouracil-leucovorin and irinotecan
• First line drug for this disease
• Neurotoxicity : dose-limiting, peripheral sensory
neuropathy(worsened upon cold exposure), cumulative
COLD
DYSESTHESIA

35. Alkylating Related drugs
Drug Doses Acute toxicity Delayed toxicity
Carmustine (BCNU) 200 mg/m2 IV
every 6 weeks
N/V Leukopenia,
thrombocytopenia, and
rarely hepatitis
Lomustine (CCNU) 150 mg/m2 orally every 6
weeks
Altretamine 10 mg/kg/d for 21 days Leukopenia,
thrombocytopenia, and
peripheral neuropathy
Procarbazine 50–200 mg/d
orally
N/V, flu-like
syndrome, drug
interactions
BMD, CNS depression,
leukomogenic
Dacarbazine 300 mg/m2 daily IV for 5
days
N/V BMD
Cisplatin 20 mg/m2/d IV for 5 days or
50–70 mg/m2 as single
dose every 3 weeks
N/V, myelosuppression Nephrotoxicity, peripheral
sensory neuropathy,
ototoxicity, nerve
dysfunction. (*)
Carboplatin AUC 5–7 mgxmin/mL Rarely: peripheral
neuropathy, renal toxicity,
and hepatic dysfunction
Oxaliplatin 130 mg/m2 IV
every 3 weeks
or 85 mg/m2
IV every 2
weeks
N/V, laryngopharyngeal
dysesthesias
Peripheral sensory
neuropathy, diarrhea,
myelosuppression, and renal
toxicity

36. ANTI-METABOLITES
Folate Antagonists
Methotrexate
Purine Antagonists
6 Mercaptopurine, 6
Thioguanine, Azathioprine
Pyrimidine antagonists
5 Fluorouracil, cytarabine,
gemcitabine

37. INTRODUCTION
•They interfere with the availability
of normal purine and pyrimidine
nucleotide precursors either by
inhibiting their synthesis or by
competing with them in DNA or
RNA synthesis

38. FOLATE ANTAGONISTS
METHOTREXATE
• Folic acid essential dietary component
• Tetrahydrofolate (FH4) reduced form  provide the
methyl grp for the synthesis of DNA(thymidylate, purine),
RNA(purine)
• Interference in FH4 metabolism reduced the cellular
capacity of one-carbon transfer, and methylation
reactions in the synthesis of purine ribonucleotides and
TMP
• Inhibiting DNA replication
• Mtx also inhibits IL 6 and IL-8 and TNF alpha

40. Mechanism Of Action
• It is structurally related
to folic acid, and act as
an antagonist of that
vitamin by binding at
its active catalytic site
and inhibit their action.
• the enzyme that
converts folic acid to
its active , coenzyme
form, tetrahydrofolic
acid

41. PHARMACOKINETICS
• Absorbed orally  50% protein bound
• Disappears rapidly from blood , remains in tissue longer than folate
thus causes prolonged inhibitory effect
• at pH 6.0, virtually no dissociation of the enzyme-inhibitor complex
occurs  which cause high affinity  and become potent inhibitor
• At physiologic pH  reversible competitive kinetics occur with
same inhibition constant
• Intracellular formation of polyglutamate derivatives  vital for
therapeutic action of drug.
• The polyglutamates of methotrexate are selectively retained within
cancer cells  have increased inhibitory effects on enzymes
involved in folate metabolism, making them important
determinants of the duration of action of methotrexate

42. CLINICAL USES
Antineoplastic
• Choriocarcinoma and tropoblast tumor
15 -30 mg/day orally for 5 days
• Remission of ALL in children 2.5 to 15
mg/day
• breast, head & neck, bladder, ovarian
cancers
Immuno-supressive
• Rheumatoid arthritis, resistant
asthma
• Crohns disease, wegeners
granulomatosis
• Prevention of graft versus host
reaction
Psoriasis
Medical termination of
pregnancy

43. ADVERSE EFFECTS
• Megaloblastic anemia
• Myelosuprresion* (prolonged in renal compromised pt, renal
CrCl monitored)
• Orallly can cause intestinal ulcer(ulcerative stomatitis),
diarrhoea,
• Alopecia , liver damage, nephropathy, pulmonary fibrosis
• CNS toxicities with intrathecal adminstration
Treatment of methotrexate toxicity
• Folinic acid (citrovorum factor, N5 Formyl THF)
• IM/IV 8 to 24 hrs after initiation of methotrexate
• 120 mg in divided doses in first 24 hrs, then 25 mg oral/IM 6
hrly for next 48 hrs

44. RESISTANCE
(1) decreased drug transport,
(2) decreased polyglutamate formation,
(3) synthesis of increased levels of DHFR through
gene amplification,
(4) altered DHFR with reduced affinity for
methotrexate

46. CONTRAINDICATION
•Teratogenic
•Excreted renally so avoid in severe
renal impairments
•Avoid in patients with liver diseases

47. PURINE ANTAGONISTS
6 Mercaptopurine,
6 Thioguanine,
Azathioprine
Fludarabin phosphate
Cladribine
6 thiopurines

48. 6-MERCEPTOPURINE (6MP)
• Thiol analogs of hypoxanthines
• Closely related analog:
Azathioprine* (immunosupressants)
• Remission in ALL(childhood) and
• 6-MP & analogs also used in the rx
of crohn’s diseases
MOA: major steps affect in
synthesis of purine:
1. Nucleotides formation
2. Inhibition of purine synthesis
3. Incorporation into nucleic acid
PLEASE REFER BOOK TO
ELABORATE THESE
MECHANISM

49. PHARMACOKINETICS
• Orally given and absorption :
erratic and incomplete
• Thioguanylic acid and 6-
Methylmercaptopurine
ribotide (MMPR) 
metabolites have same anti
cancer action
• Once reached blood
circulation  widely
distributed in thr’ body
(except CNF)
• Bio avb: reduced by first
pass metabolism in liver
• Excreted in urine

50. RESISTANCE
• An inability to biotransform 6-MP to the
corresponding nucleotide because of
decreased levels of HGPRT (eg , in Lesch-
Nyhan syndrome deficiency of this
enzyme)  acute leukemia inc’ the conc of
alkaline phosphate by alternative mechanism,
as results
• dephosphorylation of thiopurine nucleotide
• cellular loss of the resulting ribonucleoside.
• Overexpression of TPMP

51. USES & ADVERSE EFFECTS
Uses:
• ALL, crohn’s disease,
choriocarcinoma
AE:
• Bone marrow & GIT mainly
• Hepatic necrosis rarely
• Hyperuricaemia
• Jaundice

52. 6-THIOGUANINE
•Primarily used in the rx of acute
nonlymphocytic leukemia (acute myeloid
leukemia (AML))  combination with
daunorubicin, cytarabine ( adult leukemia )

53. MOA & PK
• Same as 6MP
PK:
• Like 6MP  activate after reaching
blood circulation
• Peak plasma conc: 2-4 hours after
ingestion
• S-methylation products appear in
urine by the TPMTase* enz
• Homozygous deletion / mutation in
enz cause severe toxicities
• TPMT genotyping is necessary
before treatment
• Allopurinol administration required
no dose reduction of 6TG
• Long term use caused liver toxicity
and jaundice

54. FLUDARABINE
• Phosphorylates intracellularly to form triphosphate
• Inhibits DNA polymerase and gets incorporated to form
dysfunctional DNA
• Resistance: reduced uptake, lack of deoxycytidine kinase, dec’d
affinity for DNA polymerase
• Effective in slow growing tumors
Use: – CLL and non hodgkins recurring after treatment, hairy cell
leukemia
With thymoglobuline used in the tx of stem cell transplant may be
associated with gonadal failure  risk is least for rejection
Adverse events: – chills, fever, opportunistic infection,
myelosupression
At high doses: progressive encephalopathy, blindness, and death

55. CLADIRABINE
MOA
• Like fludarabine converted to triphosphate,Incorporated into
DNA, Inhibits DNA polymerase and thus inhibits DNA
synthesis and repair
• Distributed thr’out the body, even penetrate the CSF
USES: Hairy cell leukemia, CLL and low grade lymphomas ,
multiple sclerosis
AD: severe bone marrow suppression, Peripheral neuropathy
C/I: Has teratogenic effect

56. PYRIMIDINE ANALOGUES
5 Fluorouracil
Cytarabine
Gemcitabine

57. 5-FU
• Pyridine analogue, has stable
flourine atom
MOA : in the diagram
Resistance :
• when cell lost their ability to convert
to 5- FdUMP from 5-FU
• Altered or increased thymidylate
synthase levels
PK:
• Administered IV, topically in the case
of skin cancer
• Penetrate into all body parts
including CNS
• Metabolised in lung, kidney, liver*
• Excreted via urine
• Dose must be adjust in the case of
impaired hepatic functions

58. AD
• nausea, vomiting, diarrhea
• alopecia,
• severe ulceration of the oral and GI mucosa,
• bone marrow depression (with bolus injection),
• anorexia
• allopurinol mouthwash: used to reduce oral toxicity
• Dermopathy
Uses
• Primarily used in the rx of slowly growing tumors (colorectal, breast,
ovarian, pancreatic, and gastric carcinomas)
• Superficial basal cell carcinomas.

59. CAPECITABINE
• newer, oral fluoropyrimidine carbamate
• metastatic breast cancer that is resistant to first-line drugs
(approved)
• Currently used in colorectal cancer rx
• After being absorbed undergoes a series of enzymatic
reactions the last of which is hydrolysis to 5-FU

60. CONTINUED…
PK
• Unlike 5-FU, orally well absorded
• Metabolised into fluoro-b-alanine and
CO2
• Excreted in urine
AD
• GI toxicities
• Caution with renal & kidney function
impaired pt
C/I:
• pregnant and lactating women
• Pt. who r taking coumarin
anticoagulant/ phenytoin  monitored
coagulation parameters and drug level
respectively  why?

61. FLOXURIDINE
• 5-FU analog
• When administered Intra arterial route  rapidly catabolites
into 5-FU
• MOA: Primarily interfere with DNA syn and some extent
inhibits RNA formation
• Metabolism and excretion same as 5-FU.
• Uses: palliative management of GI adenocarcinoma that
has metastasized to the liver
• AD: nausea, vomiting, diarrhea, enteritis, stomatitis, and
localized erythema

62. CYTARABINE
(CYTOSINE ARABINOSIDE, OR ARA-C)
• analog of 2'-deoxycytidine in which the natural ribose
residue is replaced by D-arabinose
• acute nonlymphocytic (myelogenous) leukemia
• In combination therapy 6-TG and daunorubicin
• MOA: enter through carrier-mediated process, sequentially
phosphorylated by deoxycytidine kinase and other nucleotide
kinases to cytosine arabinoside triphosphate(Ara- CTP)*
inhibitor of DNA polymerase (compitetive)
incorporated into nuclear DNA
Retard chain elongation
• S – phase specific inhibitor
Retention of Ara-c in the cell
is lethally to malignant cells

63. Phosphorylate
d
by
Deoxycyti
dine
kinase
Ratio of anabolic and
catabolic enz is very imp for
cytotoxicity

64. • Cytarabine is S phase specificity
• The drug is highly schedule-dependent and
must be given either by continuous infusion
or every 8–12 hours for 5–7 days
• AR:
• Nausea and vomiting
• bone marrow depression
• Stomatitis
• Cerebellar ataxia

65. GEMCITABINE
• Analog of nucleotide deoxycytidine
• Drug of choice for locally
advanced or metastatic
adenocarcinoma of the pancreas
• non-small cell lung cancer
and bladder cancer
• Resistance :
 inability to be converted to a
nucleotide
 increased levels of endogenous
deoxycytidine
• PK: infused IV, deaminated to
difluorodeoxyuridine, excreted via
urine
*
Norm
al
dCTP
lacks
MOA
only one additional nucleotide can be added
to the growing DNA strand, resulting in chain
termination.

66. REFERENCES
• Goodman & Gillman, pharmacologic basis of
therapeutics, edition 12th, part VIII, chapter: 60,
• Lippincott’s illustrated reviews, edition 4th, chap-
39.
• Katzung Pharmacology
• Internet sources.

67. THANK YOU
?