Antineoplastic
Agents

Cancer, one of the major challenges which concern the
medical community all over the world. The diversity of
tumor types and the great similarity to normal cells are the
main obstacle preventing the reach of an ultimate remedy.
Cancers could be classified based on their nature and
location throughout the human body into two main
categories:
 Solid tumors, which found in tissues and organs such as
glandular tissue cancers (carcinomas) and connective tissue
cancers (sarcomas) which could disseminate to other body
parts through the blood circulation and the lymphatic system.
Solid tumors are difficult to treat due to the lack of vascularity
and blood supply inside the tumor, which prevents any drug
from reaching the core of the tumor mass.
 Malignant hematologic diseases, such as lymphatic ganglia
cancers (lymphomas) and blood cancers (leukemias).

The rate of cell division is the only sensible difference (found so
far) which distincts cancer cell from normal cell, tumor cell is
rapidly proliferating. This rapid proliferation comprises another
difficulty in combating cancer. The lack of obvious difference
makes it difficult for any chemotherapeutic agent to distinguish
between cancer cell and any healthy cell, especially those which
are naturally of rapid cell division, as for example bone marrow
cells and the mucosa lining the walls of the gastrointestinal tract.

Tumors can be classified according to their locations into:






Carcinoma
→ Glandular tissue cancers.
Sarcoma
→ Connective tissue cancers.
Lymphoma → Lymphatic ganglia cancers.
Leukemia
→ Blood cancers.
Cell proliferation is the only difference between normal and
cancer cell, cancer cell is rapidly proliferating.
How could the anticancer agents be selectively toxic to
cancer cell?
 Tumor cell is more rapidly proliferating than normal cell so it will
consume more of the drug.
 The drug is highly toxic to the organs which is normally rapidly
proliferating such as bone marrow, hair, GIT.

Anticancer agents could be classified based on type of
activity into three main groups:
1) Growth inhibitors: Drugs which inhibit the growth of cancer cells
into 50%.
GI50: Molar concentration which inhibit net cell growth to 50%. (median
growth inhibitory concentration).

2) Cytostatic agents: Drugs which totally inhibit the growth of cancer
cells.
TGI: Molar concentration which cause total inhibition of cell growth
(total growth inhibitory concentration).


3) Cytotoxic agents: Drugs which cause 50% killing of the original no.
of cancer cells.
 LC50: Molar concentration which cause 50% killing of the initial
cell level (median lethal concentration).
NH2
N
5' end
O
P
N
A
O
O
O
N
N
NH2
O
O
P
N
C
O
O
O
N
O
O
O
O
P
N
NH
G
O
N
O
N
O
NH2
O
DNA Structure
O
H3C
O
P
O
NH
O
O
N
O
T
O
O
P
O
3' end



It is well established and documented that the difference
between normal and cancerous cell lies in the cell nucleus
which controls cell division and rather more, it might reach
the gene level.
Most of the antineoplastic agents are designed to interfere
with the protein synthesis followed by the inhibition of cell
vital processes leading to cell death.
Anticancer agents could be classified based on their mode
of action into:
 1.2.1 DNA Interactive Drugs (DID)
 1.2.2 Antimetabolites
 1.2.3 Hormones

DNA alkylators are those class of compounds which
proved to alkylate the nucleophilic centers at the
nucleic acid bases (guanine, thymine … etc.) leading to
the formation of deformed DNA which will affect
protein synthesis causing cell death.

DNA alkylators could be classified into:
 Nitrogen mustard and its analogs.
 Ethylenimines.
 Epoxides.
 Sulphonic acid esters.
 Miscellaneous.
H3C N
Cl
Cl
N,N-Bis-(β-chloroethyl)methylamine HCl
N-Methyl-bis(2-chloroethyl)amine HCl

Mechlorethamine is the only aliphatic nitrogen mustard
currently on the U.S. market and its use is limited by
extremely high reactivity, which leads to rapid and
nonspecific alkylation of cellular nucleophiles and
excessive toxicity.


It is an example of nitrogen mustard containing an aromatic ring.
It is active intact and also undergoes β-oxidation to provide active
phenylacetic acid which is responsible for antineoplastic activity.
Cl
Cl
COOH
N
Cl

COOH
Chlorambucil
(Active)
N
Cl
Phenylacetic acid mustard
(Active)
It is used in chronic lymphocytic leukemia, malignant lymphoma
and Hodgkin’s disease.
Synthesis
NH2
OH
N
OH
+
COOCH3
2
O
Ethylene oxide
SOCl2
Methyl p-aminophenylbutyrate
N
Cl
COOCH 3
Cl
N
Cl
Cl
hydrolysis
COOH
4-[Bis-(2-chloroethyl)amine] phenylbutyric acid.
COOCH3
2
3
O
N
H
O
Cl
N
P
1
Cl
N,N-Bis(2-chloroethyl)tetrahydro-2H-1,3,2-oxazaphosphorin-2-amine-2-oxide.


It is a prodrug that requires activation by metabolic and non metabolic process.
This need for metabolic activation means decrease in GI toxicity and less non
specific toxicity if compared with other alkylators.
Metabolism
H
H
HO
N
O
N
Cl
P
N
O
Hydroxylation
O
P
Cl
N
O
(inactive)
Cl
4-Hydroxy-derivative Cl
(inactive)
CHO
H
HN
O
P
Cl
N
O
Cl
H 2N
HO
Strained
P
H2N
N
HO
O
Cl
Active alkylating agent
Alcophosphamide deriv.
(unstable)
P
Cl
N
O
Cl
Cl
N
NH2
H2
C C COOH
H
Cl
It is also known as L-phenylalanine mustard or L-PAM, is
nitrogen mustard chemically linked to a natural amino acid.
It is also attached to aromatic ring so it is less reactive with
decreased incidence of side effects.
It is used in inoperable malegnancies.
Cl
R
DNA 1 (Nu)
N
R
Cl
N
Cl
Aziridinium cation
DNA1
R
N
Cl
DNA1
R
N
DNA1
DNA2
DNA2
Intrastrand cross linked DNA
Alkylated DNA  cell death
R
N
N
2,4,6-Tris (1-aziridinyl)-s-triazine.
Synthesis
N
N
N
Cl
OH
SOCl2
N
N
N
N
Cl
HO
N
N
N
N
N
N
N
Cl
OH
Cyanuric acid
+
N
N
H
N
Ethylenimine
N
O
N P N
N
S
N P N
N
Triethylene phosphoramide Triethylene thiophosphoramide
thio TEPA
TEPA
O
4
1
3
2
O
1,2,3,4-Diepoxybutane
Synthesis
H 2O 2
Ag+
1,3-Butadiene
O
4
1
3
2
O
R
N
DNA or
RNA
+
R
H
N
or
DNA
or
O
DNA
OH
R
R
O SO2 CH3
O SO2 CH3
1,4-Bis(Methansulphonyloxy)butane.
Tetramethylene-bis(methane sulphonate)
Busulfan is classified as an alkyl sulfonate; one or both of the
methylsulfonate ester moieties can be displaced by the
nucleophilic N7 of guanine, leading to monoalkylated and crosslinked DNA.
Synthesis
CH3SO2Cl +
OH
OH
Methane
sulphonyl
chloride
1,4-Dihydroxybutane
Pyridine
O SO2 CH3
O SO2 CH3
Metabolism and Mode of Action
O SO2 CH3
O SO2 CH3
+
Inactive
AND
H 2 COOH
HS C CH
NHR
Glutathion
or cysteine
H 2 COOH
S C CH
NHR
DNA
H 2 COOH
S C
NHR
Cyclic sulfonium ion
(Alkylating agent)
HO
S
O
O
3-Hydroxythiolane-1,1dioxide
O
3
N
4
1N
5
2
H
NH 2
N 3 CH 3
N 2 N
1
CH 3
5-(3,3-Dimethyl-1-triazenyl)-imidazole-
4-carboxamide
Metabolism and Mode of Action
O
O
N
N
H
NH 2 14
N
CH3
N
N
14CH 3
Oxidative
dealkylation
N
Cytochrome
P-450
N
H
Monomethyl
derivative
O
N
14
H 3C N N
+
N
H
Diazomethane
cytotoxic (moiety)
14
N N CH 3
NH 2 14
N
CH3
N
N
H
NH 2
Amino imidazole
carboxamide
O
HN
N
H 2N
N
N
N
DNA
-N2
N
N
H
NH 2
O
O
HN
N
H 2N
N
14
N
H
NH 2
14
N
CH3
N
Monomethyl
derivative
CH 3
N
N
DNA
alkylated DNA
Cell
death
O
H
N
CH 3
CH 3
H
N N CH 3
H
N-(Isopropyl)-4-(2-methylhydrazinomethyl)benzamide
HCl.
Mode of Action
O
O
H3CHN
N
H
P450 or
CNHCHMe2 spontaneous
H2
C
H3CN
B
H
C
N
H
CNHCHMe2
H
B
O
H3C
H
N
NH2 +
O
H
C
CNHCHMe2
H2O
O
H3CHN
N
H
C
CNHCHMe2
O
H3C
H3C
N
N
N
DNA
N
N
NH
CH3 + N2
H2N
CH3
N
N
DNA

Cisplatin, Platinol:
Cl +2 NH 2
Pt
NH2
Cl
Cis-diaminedichloroplatinum
H2 N
Pt
NH2
O
HN
N
H2 N
N
O
N+
N
DNA
N+
N
DNA
NH
N
N
NH 2
Interstrand cross links in DNA.
 Carboplatin
O
O
NH 3
Pt
O
NH 3
O
It is a less potent chemotherapeutic agent. Suppression
of platelets and white blood cells is the most significant
toxic reaction of carboplatin use.
Cl
O
N C N
H
NO
Cl
Carmustine (BCNU)
1,3-Bis(2-chloroethyl)-1-nitrosourea

Cl
O
N C N
H
NO
Lumustine (CCNU)
1-(2-chloroethyl)-3-cyclohexyl1-nitrosourea
Duration of Action:
 BCNU: t ½ = 90 min.
 CCNU: t ½ = 16 hr.


Nitrosoureas possess high lipid solubility which allows BBB
crossing, so they used mainly to treat Brain tumors and Hodgkin’s
disease.
Mode of Action: alkylating agents.
Cl
O H
N C N
N O
(CCNU)
Cl
N NOH
H
+
O C N
-N2 , OH
NH2-lysin of protein
Cl-CH 2-CH 2
Guanine-DNA
protein
Cl
O
N
N
H2 N
N
N
DNA
Alkylated DNA
O H
N C N
H
Carbamoylated protein

Polycyclic plannar compounds have the ability to insert or intercalate
through the grooves of the base pairs of the DNA double helix.

This insertion process will activate topoisomerase I & II enzymatic system
which catalyzes DNA strand cleavage.

Acridines such as amsacrine proved to possess this DNA intercalation
activity.

Figure 1, shows how the tyrosinyl moiety carried by topoisomerases could
catalyze such DNA cleavage.
3
CH3 O
H
8
2
1
N
1
9
2
7
6
5
NHSO2 Me
4
N
10
H
3
4
9-[(2-Methoxy-4-methylsulphonylamino)aniline]acridine.
O
CH 2OCONH 2
OCH3
CH 3
N
O

7
NH
HO CH
2
O
HO
HO
OH
NH
OC N CH 3
8
NO
Natural products such as bleomycins, mitomycins (7) and streptozotocin
(8) are characterized by their ability to intercalate into the DNA duplex
and initiate a series of free radical destruction of the DNA strand
preventing the process of mitosis and consequently preventing cell
division.

Those Natural products are:
• Antibiotics
 Bleomycins
 Daunorubicins
 Mitomycins
 Streptozotocin
• Vinca Alkaloids
 Vinblastine
 Vincristine
 Mode
of Action of Strand Breakers
Fe(III) + BLM
DNA strand
scission
e
Fe(III)
BLM
DNA
Fe(II)
Activated
BLM
BLM
O2
e-
Fe(II)
BLM
O2
Cycle of events involved in DNA cleavage by bleomycin (BLM)
O
OH
O
HO
O
CH 2R
HO
OH
OH
HO
NH
C
O
N
R
OCH 3
N
H 3C
O
O
Daunorubicin, R = H
Doxorubicin, R = OH
CH 2OCONH 2
X
OH
NO
Streptozotocin; R = CH3
Chlorozotocin; R = CH 2CH2 Cl
O
OCH3 O
NY
O
Mitomycin A; X = CH3 O, Y=H
Mitomycin C; X= NH2 , Y=H
CH 3
NH 2
O
OH
CH2OCONH2
X
OH
N
H3 C
O
Mitomycin B; X = CH 3O
Mitomycin D; X= NH 2
NCH 3
A. Daunorubicin Analogs
O
OH
OH
OH
OH
OH
O
R
O
R
NADPH
Enzyme
OMe
O
OH
OH
O
OMe
OH
OH
O
Sugar
OH
OH
OH
O
Sugar
OH
OH
R
OMe
O
OH
DNA
O
R
OMe
O
O
DNA
Anthracycline antitiumor agents as bioreductive alkylators
B. Mitomycin analogs
O
OH
O
O
10
H 2N
O
CNH 2
OCH3
N
H 3C
10
H 2N
O
O
CNH 2
OCH3
N
H 3C
NH
10
OH
H 2N
O
CNH 2
H
B
NH
N
H 3C
OR
NH
OR
O
B
O
H
O
O
OH
O
O
H 2N
CNH 2
DNA
N
H 3C
H 2N
CNH 2
O
NH2
OR
DNA
O
H
O
CNH 2
H 2N
N
H 3C
OR
N
H 3C
NH2
OH
DNA
H 2N
H 3C
N
OR
NH
H
B
R3
N
R2
NH
COOCH3
R1 N
O
OH
R4
N
RO
R
R1
R2
R3
R4
Vincristine
CH3CO
CHO
H
OH
OCH3
Vinblastine
CH3CO
CH3
H
OH
OCH3
Vinrosidine
CH3CO
CH3
OH
H
OCH3
Vinleurosine
CH3CO
CH3
H
?
OCH3
Vinglycinate
(CH3)2NCH2CO
CH3
H
OH
OCH3
Vindesine
H
CH3
H
OH
NH2

Colchicine, obtained from the crocus Colchicum autumnale, has long been known for its
antitumor activity. However, it is not now used clinically for this purpose. Its main use is in
terminating acute attacks of gout. Among colchicines derivatives, demecolcine (colcemid)
is active against myelocytic leukemia, but only at near-toxic doses. Colchicines have an
unusual tricyclic structure containing a tropolone ring. They inhibit mitosis at metaphase by
disorienting the organization of the spindle and asters.
CH 3O
NHR
Colchicine, R = COCH3
Colcemid, R = CH3
CH 3O
OCH3
O

Those are class of compounds which are structurally related to
natural occurring substances found in normal cells.

Antimetabolites compete with those natural cell components for
the active sites on enzyme(s) or receptor(s), and they might
incorporate into the nucleic acids to disrupt their cellular
functions.

Antimetabolites could be classified into:
 Purine Antagonists
 Pyrimidine Antagonists
 Folic
acid
Inhibitors)
Antagonists
(Dihydrofolate
Reductase
Inhibitors=
DHFR


S
Those are group of compounds which are
N
structurally related to the natural purine HN
bases (hypoxanthine, adenine, xanthine and
N
guanine) and compete with their cellular
N
9 H
functions.
Example of those chemotherapeutic agents
are mercaptopurine {leukerine (9)} and
CH 3
azathiopurine{ Imuran (10) }they are proved
N
to inhibit aminotransferase, adenylsuccinate
N
synthase, adenylsuccinate lyase and inosine
monophosphate dehydrogenase enzymatic
S
NO2
systems leading to protein synthesis
N
N
inhibition followed by cell death.
N
10
N
H
O
NH 2
N
HN
N
N
N
H
Hypoxanthine
N
N
H
Adenine
N
O
N
HN
O
O
N
H
N
H
Xanthine
N
HN
H 2N
N
H
Guanine
N
Normal cell can get its need from these bases through:
A.De Novo Purine Synthesis
B. Salvage Purine Synthesis

A. De Novo Purine Synthesis
-2
5-Phosphoribosyl-1-pyrophosphate
O3P O
O
NH 2
Aminotransferase
+
enzyme
Glutamine
HO OH
5'-Phosphoribosylamine
DNA & RNA
Purine nucleotide
(Inosinic acid, IMP)
B. Salvage Purine Synthesis
COOH
O
O
N
HN
N
PRTase
N
HN
N
H
Adenylsuccinate
Adenosine
deaminase
A.S. Lyase
O
H2N
NH2
N
HN
N
N
Ribose-5'-P
N
Inosinic acid (IMP)
IMP dehydrogenase,
GMP synthase
N
N
N
Ribose-5'-P
N
Hypoxanthine
A.S. Synthase
H2C HC COOH
NH
N
Ribose-5'-P
GMP
N
N
N
N
Ribose-5'-P
AMP
S
6-Mercaptopurine or purine-6-thiol.
6
5
1 HN
N
S
N
HN
N
N
H
Hypoxanthine
P2 S5
8
N9
H
3
O
N
4
2
Synthesis
7
N
HN
N
N
H
Mechanism of Action
S
S
N
HN
PRTase
N
HN
N
H
6-Mercaptopurine
N
N
N
Ribose-5'-P
1. Inhibition of De Novo Synthesis
aminotransferase
Phosphoribose
+
NH 3
Phosphoribosylamine
inhibition
Mercaptopurine
nucleotide
Purine nucleotide
2.
Inhibition of Salvage Purine Synthesis
S
N
HN
A.S. Synthase
Adenylsuccinic acid
N
Ribose-5'-P
N
PRTase
IMP
dehydrogenase
S
N
HN
N
GMP
N
Ribose-5'-P
S
N
HN
H 2N
N
N
H
2-Amino-6-mercaptopurine
H 3C
6-[(1-Methyl-4-nitroimidazol-5yl)thio]purine
S
N
+
N
N
H
Cl
N3
NO2
N
N
H
CH 3
O2N
N
N
4
Synthesis
N
2
5
N
SH
1
N
5-Chloro-1-methyl4-nitroimidazole
2
N
N3
5
base
N
CH3
1
S
N
N
4
NO2
N
N
H
O
N
HN
H2 N
N
N
N
H
2-Amino-6-hydroxy-8azapurine



Fluorouracil (11) and cytarabine (12) represent this group of compounds.
They resemble the natural pyrimidine (uracil, thymine and cytosine) in
structures and compete with their cellular functions leading to the inhibition of
two vital enzymatic systems responsible for the production of thymine from
uracil.
These two enzymes are ribonucleotide reductase and thymidylate synthase.
NH 2
O
HN
O
F
N
H 11
N
O
12
N
arabinose
O
HN
O
O
O
ATP
N
ADP
HO
O
O
HN
O
O3 PO
OH OH
N
H
The metabolic role of
ribonucleotide reductase enzyme
O
O
O
N
O3 PO
PO
O
OH OH
ATP
Ribonucleotide
O
N
PO
O
O
reductase
OH
O
HN
HN
O
N
O
O
O3 PO
HN
OH OH
ADP
O
O
HN
O

HN
N
H
Uracil
NH 2
CH 3
N
O
N
H
Thymine
O
N
H
Cytosine
Normal cells can get its need from these bases through:
1.
De Novo Pyrimidine Synthesis
3-O3PO
O
NH 2
Pyrimidine
nucleotides
OH OH
5'-Phosphoribosylamine
DNA & RNA
2. Salvage Pyrimidine Synthesis
O
O
HN
O
N
H
Uracil
PRTase
HN
O
O
Thymidine
N
Rib-5'-P
synthase
HN
O
CH3
N
Rib-5'-P
O
5-Fluorouracil or 5-Fluoro-2,4 (1H, 3H)pyrimidindione.
5
1 HN
Mode of action
O
O
(1)
F
N
Ribose-5'-P
F
HN
Ribonucletide
Reductase
O
N
deoxyribose-5'-P
FUMP
RNA
N3
H
O
O
HN
2
4
FdUMP
Fraudulent
DNA
F
O
5-Fluorouracil or 5-Fluoro-2,4 (1H, 3H)pyrimidindione.
5
1 HN
Mode of action
O
(2) O
N3
H
4
O
O
HN
2
F
H
N
Ribose-5'-P
Thymidine
Synthase
inhibition
FUMP
HN
O
CH3
N
deoxyribose-5'-P
NH2
4
3
4-Amino-1-B-D-arabinofuranosyl-2(1H)pyrimidinone.
N
O
O
HO
OH
O
CH3
HO
N
2
1
HO
Synthesis
4
3
O
O
HO
Cl
+
N
H3 C
OH
H
O
N
2,4-dimethoxpyrimidine
N
O
HO
N
2
1
O
HO
OH
Cytarabine
H
CH3
H
Mode of Action
NH 2
N
Cytarabine
nucleoside
kinase
O
H3 O3 P O
N
O
HO
OH
Cytrabine-5-P
Fraudulent
RNA



Folic acid metabolism is an important source for one carbon moiety
needed to convert uracil into thymine.
Inhibition of folic acid metabolism, in other words, inhibition of
dihydrofolate reductase will deplete the cellular systems from
thymine – a pyrimidine base-very much needed for nucleic acid
biosynthesis.
Methotrexate (13) and fluorouracil (11) represent this class of
compounds.
O
NH2
H 3C
N
H
N
N
N
H 2N
(H2 C) 2
N
N
13
COOH
COOH
R
O
N
H
HN
N
O
R=
N
H
O
Dihydrofolate
N
H2 N
R
reductase
Dihydrofolic acid
H
N
N
H
HN
H 2N
N
N
H
Tetrahydrofolic acid
CNMCH(CH2)2COOH
NH2
HOCH 2CHCO2H
COOH
Pyridoxal phosphate
Thymine
H2NCH2CO2H
R
Metabolic role of
dihydrofolate reductase
O
N
N
HN
Uracil
H2 N
N
N
H
5,10-Methylenetetrahydrofolic acid

Based on that, folic acid antagonists could be classified into:
• A. Dirhydrofolate reductase inhibitors
 Methotrexate, Mexate, Amethopterin
• B. Thymidylate synthetase inhibitors
 Fluorouracil, Fluoroplex:

Methotrexate, Mexate, Amethopterin:
O
NH2
4
3
N
H 3C 10
N
5
9
N
6
2
H 2N
N
1
N
8
7
H
N
(H2 C) 2
COOH
4-Amino-10-methylpteroylglutamic acid
COOH

Methotrexate, Mexate, Amethopterin:
 Synthesis
NH2
NH2
N
H2N
O
N
Br
+
+
Br
NH2
H
N
H3C
N
(H2C)2
CHO
p-(methylamino)benzoyl
glutamic acid
I2,KI, Ca(OH)2
O
NH2
N
N
H2N
H3C
N
N
COOH
COOH
2,3-Dibromopropionaldehyde
2,4,5,6-tetraaminopyrimidine
H
H
N
N
(H2C)2
COOH
COOH

Methotrexate, Mexate, Amethopterin:
 Mode of Action
 Dihydrofolate reductase utilizes methotrexate to produce
a tetrahydrofolate derivative which then accumulates
leading to enzyme inhibition.
 Accumulation
of
tetrahydromethotrexate
will
inhibit
tetrahydrofolate reductase enzyme.
 This will lead to depletion of thymine stores   DNA &
RNA synthesis.

Methotrexate, Mexate, Amethopterin:
H 3C
NH2
R
N
NH2
H
N
Tetrahydrofolate
N
N
H3C
N
reductase
H2N
N
N
H2N
Methotrexate
N
H
Tetrahydromethotrexate
R
NH2
N
N
N
H2N
N
N
N
H
R
N

Methotrexate, Mexate, Amethopterin:
 Contraindications:
 Salicylates
and
sulfonamides
increase
methotrexate
toxicity by:
 1. inhibiting its renal tubular secretion.
 2. they displace methotrexate from plasma protein
binding.

Fluorouracil, Fluoroplex
O
F
HN
O
N
H
NH
5-Fluoro-2,4-(1H, 3H)-pyrimidindione
 Mode of Action
It interacts irreversibly with tetrahydrofolate making it
unavailable for thymidine synthetase
inhibition of thymidine production.
leading to
the

Some cancers are responsive to sex hormone treatment.

Hormones control the dissemination of cancer but suffer from side
effects as:

1.
Androgens  musculinizing effect

2.
Estrogens  feminizing effect

3.
Adrenocorticoids  salt and water retention

Tamoxifen citrate is a nonsteroidal drug with anti-estrogenic effect
used as anticancer
2'
CH3
1' O
N
CH3
C
C
H3CH2C 2
1
4
3
2-[4-(1,2-Diphenyl-1-butenyl)phenoxy]-N,N-dimethylethanamine
citrate.
 Mode

of Action
Tamoxifen is an estrogen receptor antagonist, blocks the
growth promoting effects of estrogen in tumors.
 Uses:Advanced
breast carcinoma.