B33E11 Complete TB

Cancer Biology and Chemotherapy

Tracey D Bradshaw

E-mail: [email protected]

Outline:

Introduction to cancer

Cytotoxic and Target-directed cancer chemotherapy

Appreciate the size of the cancer problem and the challenge facing

patients, clinicians and researchers

Incidence

Mortality

Objectives (i)



Incidence

Mortality

Recognise common cancer terminology

Apreciate some causes of cancer epidemiology

Objectives (i)



Incidence

Mortality



Cancer is a genetic disease

Oncogenes

Tumour suppressor genes

DNA repair genes/mechanisms gatekeepers

Objectives (i)

} drivers



Incidence

Mortality




Oncogenes


DNA repair genes/mechanisms gatekeepers

An understanding of the processes of tumourigenesis and the

hallmarks of cancer

Objectives (i)

} drivers

CANCER; TUMOUR; NEOPLASM

Benign: normal chromosomes

differentiated

rare division/slow growing

encapsulated

do not metastasise

Malignant: abnormal chromosomes

poorly differentiated

may be frequent division

capable of invasion and

metastasis

All multicellular organisms can be afflicted by cancer:

Apparent rising incidence - expanding knowledge - earlier diagnosis

- increased lifespan

An estimated 12.7 million new cancer cases were diagnosed worldwide in 2008.

Lung, female breast, colorectal and stomach cancers were the most commonly diagnosed

cancers, accounting for >40% of all cases.

Worldwide, an estimated 7.6 million deaths from cancer occurred in 2008.

Lung, stomach, liver, colorectal and female breast cancers were the most common causes, accounting

for >50% of all cancer deaths.

Cancer: Global Statistics (2008)

Cancer: The U.K. Statistics

Cancer will affect one in three of the UK population, and be responsible for one in four deaths (>324K new cases in UK in 2010)

There are more than 200 different types of cancer, but four of them lung, breast, colorectal and prostate account for over half of new cases

65% of cases occur in those over 65

In children, leukaemia is the most common cancer

Cancer Incidence statistics 2005

Cancer Mortality statistics 2007

Female Male

5 year Cancer Survival 2001 (England and Wales)

Breast 79%

Prostate 61%

Lung 6%

CRC

21 Common Cancers: 2005 - 2009 and Followed up to 2010 Five-Year Relative Survival, Adults Aged 1599, England

Breast >80%

Prostate >80%

Lung

Cancer Classification

Carcinomas: the most common types of cancer, arise from cells of embryonic endoderm or ectoderm, cover external and internal body surfaces, e.g. epithelia of lung, breast, colon

Sarcomas: arise from cells of embryonic mesoderm, the supporting tissues of the body such as bone, cartilage, fat, connective tissue and muscle

Lymphomas: cancers that originate in the lymph nodes and tissues of the bodys immune system

Leukaemias: cancers of the immature wbcs that grow in the bone marrow and accumulate in large numbers in the bloodsteam

Cancer: General Considerations

Cancer is a disease of abnormal differentiation:

consider leukaemia, neuroblastoma

Cancer arises from loss of normal growth control

Cancer is a disease of genetic origin

A tumour arises from one ancestral genetically

aberrant cell

Tumourigenesis is a multi-stage process

Apoptosis

Proliferation

Homeostasis perturbed

Homeostasis

Proliferation Apoptosis (Cell division) (Cell death)

cancer







aberrant cell


Cellular

metabolism

UV

light

Ionising

radiation Chemical

exposure Replication

errors

DNA damage: Single strand break

Double strand break

Chemical crosslink

DNA-protein crosslink

DNA-DNA crosslink

Base oxidation, alkylation

Abasic site

Pyrimidine dimer

>200 000 events / cell / day

Cell cycle

checkpoint

activation

Apoptosis

DNA Repair:

Direct repair

Base Excision Repair (BER)

Nucleotide Excision Repair (NER)

Mismatch Repair (MMR)

Homologous Recombination

Non Homologous End Joining

DNA Repair

Genetic origins of Cancer







aberrant cell


Tumourigenesis is a multistep process:

May take decades

Age-dependent cancer incidence e.g. prostate cancer

Initiation Single genetic event

Promotion Clonal expansion

Progression Increased genetic / chromosomal instability,

accumulation of mutations, increasingly aggressive

phenotype

Metastasis

*

* *

Causes of Cancer

Tobacco Body weight Physical activity Diet Hormones (reproductive factors - late age at first

pregnancy a factor in breast cancer)

Sunlight (UV radiation) Occupational carcinogens (asbestos, benzene,

pesticides)

Infectious agents - Viruses (papillomavirus (HPV) in cervical cancer)

- Bacteria (H. Pylori gastric ulcers/cancer

Medical treatment (radio- and chemotherapy)

Pollution (diesel exhaust, xenoestrogens) Heritable cancer predisposition syndromes

Smoking- and lung cancer incidence in the

20th Century

Cigarette smoke is a toxic

cocktail of > 4000 chemicals.

>43 known carcinogens are

inhaled.

Smoking- and lung cancer incidence in the

20th Century

Cigarette smoke is a toxic

cocktail of > 4000 chemicals.

>43 known carcinogens are

inhaled.

HO

OH

O

Benzopyrene[a]pyrene from cigarette

smoke condensate damages DNA of

lungs contributing to pathogenesis of lung

cancer

Smoking- damages many parts of the body

Causes of Cancer

Tobacco Body weight Physical activity Diet Hormones (reproductive factors - late age at first

pregnancy a factor in breast cancer)

Sunlight (UV radiation) Occupational carcinogens (asbestos, benzene,

pesticides)

Infectious agents - Viruses (papillomavirus (HPV) in cervical cancer)

- Bacteria (H. Pylori gastric ulcers/cancer

Medical treatment (radio- and chemotherapy)

Pollution (diesel exhaust, xenoestrogens) Heritable cancer predisposition syndromes

Infectious causes of cancer

Oncogenic human viruses:

Hepatitis C RNA virus

Causes hepatocellular carcinoma through

cycles of inflammation, repair and regeneration.

Oncogenic bacteria:

Heliobacter pylori, a spiral flagellated

Gram negative bacterium which underlies

pathogenesis of gastric carcinoma

causes gastritis, peptic ulceration and cancer.

Half the world`s population infected

Barry Marshall

http://discovermagazine.com/2010/mar/07-dr-drank-broth-gave-

ulcer-solved-medical-mystery

1. Self-sufficiency in growth signals

2. Insensitivity to growth-inhibitory signals

3. Evasion of programmed cell death

(apoptosis)

4. Limitless replicative potential

5. Sustained angiogenesis

6. Tissue invasion and metastasis

7. Reprogramming energy metabolism

8. Evasion of immune destruction

The Hallmarks of Cancer (Hanahan and Weinberg, Cell, 2011, 144, 646-674)

Cancer is complex but can be understood in terms of

underlying Principles of Tumourigenesis.

Apoptosis

Proliferation

Homeostasis perturbed

Homeostasis

Proliferation Apoptosis (Cell division) (Cell death)

cancer

Homeostasis

Proliferation Apoptosis

Proto-Oncogenes


C-abl p53

Cancer cells acquire mutations in genes which encode

proteins whose roles in regulatory circuits control

normal cell proliferation and homeostasis

Homeostasis

perturbed

Proliferation

Carcinogenic Oncogenes

Apoptosis


bcr-abl

p53

X

Cancer

Proto-oncogenes and Signalling Systems

Proto-oncogenes encode proteins that relay growth-stimulatory signals from outside the cell to the nucleus

Growth factors bind to specific receptors on the cell membrane

Receptor binding activates proliferative signal transduction cascades within the cytoplasm

The succession of relay proteins results in activation of transcription factors which drives transcription of genes producing proteins which usher the cell through its growth cycle

Oncogenes and Signalling Systems A Some oncogenes force cells to

overproduce growth factors e.g. sarcomas and gliomas release excessive platelet-derived growth factor

B Some oncogenes produce aberrant or elevated receptors which release proliferative signals even in the absence of growth factor, e.g. Erb-B2 (Her2) receptors in breast cancer cells

C Some oncogenes perturb signalling cascades in the cytoplasm, e.g. mutant Ras protein found in carcinomas of the colon, pancreas and lung

D Some oncogenes alter the activity of nuclear transcription factors, e.g. c-myc in the absence of growth factors in leukaemias, breast, stomach and lung cancers

Ras

Her2

Her2

cytoplasm

nucleus

c-myc

The Hallmarks of Cancer (1)

Self-Sufficiency in Growth Signals

Proto oncogenes Oncogenes

mutated

inappropriately expressed

constitutively activated

Cancer

q 34

q 11 bcr

c-abl proto-oncogene

145 kDA

Chr 9 22 9q+ Ph1

t (9;22)

Translocation mutation

bcr-abl 210 kDa

Carcinogenic oncogene

- tyrosine kinase activity

constitutively active

9q+ Ph1

Pathogenesis of Chronic Myeloid Leukaemia (CML)

Point Mutations:

If a point mutation occurs, - a single base is altered

- an altered codon

- different amino acid

- protein function

Point mutations in codons 12, 13 or 61 lead to constitutive activation of growth stimulatory signals and tumour formation:

Codon 61: CAA AAA; glutamine - lysine

Ras Most common carcinogenic oncogene in human

cancer (25%): 90% pancreas, 50% colon; 50% thyroid.

The Hallmarks of Cancer (2):

Insensitivity to growth-inhibitory signals

Cancer cells evade or ignore braking signals issued by normal cells

Tumour suppressor genes (P53, PTEN) are mutated, thereby inactivated

In a point mutation: - a single base is altered

- an altered codon


- protein function

In P53 protein: G A; codon 273 results in Arginine - Histidine and inactivation of function.


Insensitivity to growth-inhibitory signals

P53 protein (the guardian of the genome) can halt cell cycle progression in response to DNA

damage, promoting DNA REPAIR or inducing

APOPTOSIS (programmed cell death)

Mutant p53 is found in over half of all human tumours

You have access to different types of cancer either

via the menu on the left or by clicking on a specific

cancer name on the map below.

Cell Cycle

G1 Production of RNA proteins

and enzymes needed for

DNA synthesis

S DNA synthesis

G2 preparation for mitosis,

specialised proteins are

synthsised

M prophase, metaphase,

anaphase, telophase

Division to form 2 daughter

cells.

P53

P53

p53

Division of cells with carcinogenic DNA lesions

X Cell cycle arrest DNA Repair MMR,

BER,

NER,

HR


Evasion of programmed cell death (apoptosis)

Tumour growth is determined not only by the rate of cell proliferation but also by the rate of cell attrition, Programmed Cell Death: APOPTOSIS

P53 protein helps to trigger cell suicide; its inactivation by many tumour cells reduces the likelihood of elimination of damaged cells

Cancer cells also synthesise excessive amounts of survival proteins (eg Bcl-2), which inhibit apoptosis

Cellular

metabolism

UV

light

Ionising

radiation Chemical


errors


P53

Apoptosis

X

Cells with damaged DNA, harbouring

carcinogenic lesions survive and proliferate

Cellular

metabolism

UV

light

Ionising

radiation Chemical


errors


X

Cells with damaged DNA, harbouring

carcinogenic lesions survive and proliferate

BCL-2

MCL-1

SURVIVAL

:

Proto-oncogenes

Tumour supressor genes

Genes encoding proteins involved in DNA repair:

Nucleotide Excision Repair (NER): XP

Homologous Recombination: BRCA1/2

DNA Damage leading to Genetic Mutations.

Tumour initiation

Cellular

metabolism

UV

light

Ionising

radiation Chemical


errors

Li-Fraumeni syndrome: Heritable Cancer Predispositions conferred by germline

mutation in P53.

Germline mutation in P53

tumour suppressor gene 17p13

Predisposes sufferers to

wide variety of cancer types

Young age at onset of

malignancies

Multiple primary sites during

lifetime:

Breast, brain, leukaemia, soft

tissue / bone sarcoma.

BBC Radio 4 Inside the Ethics Committee Series 9 episode 3; 22. 08. 2013.

So far


Oncogenes


Genes encoding DNA repair proteins

Hallmarks of cancer

Self sufficient growth

Overcome growth inhibitory signals

Evasion of apoptosis

Hallmarks of cancer




Limitless replicative potential

Sustained angiogenesis

Invasion

Metastasis

DNA segments at the ends of chromosomes,

known as telomeres (TTAGGG in humans)

protect chromosomal integrity, tally the

number of replicative generations and initiate

senescence and crisis.


Infinite replicative potential

Thus, the number of divisions a cell can

undergo is finite

The telomerase enzyme complex restores

telomeres to the ends of chromosomes,

enabling endless replication

Telomerase is active in >85% cancers but

inactive in most normal cells


Infinite replicative potential



Proliferation of new capillaries is known as angiogenesis (or neovascularisation), it is typically short-lived (one or two weeks).

Tumour cells however can switch on angiogenesis. Angiogenesis is crucial for:

Primary tumour growth (promotion of a small cluster of mutated cells to a large malignant growth)

Metastasis.

Blood vessel

Oxygenated area

Hypoxic tumour mass

Necrotic region

Why is angiogenesis important for tumours?

In situ carcinoma: undetectable microscopic mass of tumour cells

Tumour cells secrete molecules (e.g. vascular endothelial growth

factor, VEGF)

Signalling activates genes/ protein synthesis in normal host tissue

encouraging growth of new blood

vessels to the tumour

In normal tissues, cells adhere to cells and to extracellular matrix (ECM): growth is anchorage dependent.

In cancer cells, cell adhesion molecules: E-cadherin are compromised or absent. Growth becomes anchorage independent.

Cancer cells release matrix metalloproteinase enzymes which dissolve basement membranes allowing invasion and escape.

Invasion of vascular beds of distant organs allows secondary tumours, metastases to establish.


Tissue Invasion and metastasis

Cancers are capable of spreading through the body by:

Invasion: Penetration of cancer cells into neighbouring tissues:

Mammary carcinoma invading the surrounding breast tissue


Tissue Invasion and metastasis

(6) Tissue Invasion and metastasis

Secondary tumours are more aggressive and resistant to therapy.

Metastases account for ~ 90% cancer deaths.

Metastasis: Systemic circulation and invasion of distant tissues:

lung,

liver,

bone.


Oncogenes


Genes encoding DNA repair proteins

Hallmarks of cancer




Infinite replicative ability


Invasion and metastasis

Cell 2011 Mar 4;144(5):646-74. D Hanahan and RA Weinberg Hallmarks of cancer: the next generation.

Current Treatment Options

Surgery (localised tumour)

Radiotherapy (localised tumour)

Chemotherapy (disseminated tumour)

Cancer Chemotherapy

Chemotherapy uses chemical agents, which may be:

natural products, natural product-derived (semisynthetic), natural product-inspired,

synthetic small molecule or antibody anticancer drugs to destroy or control the growth of cancer cells.

Because chemotherapy treats the whole body, it can

treat cancer cells that have already escaped the

primary tumour.

Objectives

Understand the mechanisms of action of major clinically used cytotoxic anticancer drugs.

A knowledge of mechanisms of acquired / inherent resistance to chemotherapeutic agents, and

appreciate rationale underpinning combination

therapy.

Appreciate the side effects associated with chemotherapeutic agents and their cause.

Cell Cycle

G1 Production of nucleotide

bases, RNA proteins and

enzymes needed for DNA

synthesis

S DNA synthesis

G2 preparation for mitosis,

specialised proteins are

synthesised

M prophase, metaphase,

anaphase, telophase

Division to form 2 daughter

cells.

G0 Dormant phase

G0

Cytotoxic chemotherapy interferes primarily with DNA synthesis and mitosis (the (G1) S and M phases of the

cell cycle) to destroy cancer cells.

Chemotherapeutic drugs do not distinguish between normal cells and cancer cells. Adverse reactions to

chemotherapy are a consequence of cytotoxicity to normal cells.

However, cytotoxic chemotherapeutic agents do show selectivity for cancer cells over normal cells:

Normal cells are able to repair DNA; normal tissues

recover. Injury caused by chemotherapy is rarely

permanent.

Mustard Gas was first used in September 1917 during WWI. It was one of the most

lethal of all the poisonous chemicals used in warfare.

British soldiers blinded by mustard gas

Cytotoxic Chemotherapy: History

During WWII, it was found that soldiers who were

exposed to mustard gas, sulfur mustard suffered

from lower white blood cell counts.

This discovery led to the use of nitrogen mustard, a

similar but less toxic chemical agent, to cure patients

with high white blood cells counts (lymphoid

leukaemia) and lymphomas.


S

CH2--CH2--Cl

CH2--CH2--Cl

During WWII, it was found that soldiers who were

exposed to mustard gas, sulfur mustard suffered

from lower white blood cell counts.

This discovery led to the use of nitrogen mustard, a

similar but less toxic chemical agent, to cure patients

with high white blood cells counts (lymphoid

leukaemia) and lymphomas.


S

CH2--CH2--Cl

CH2--CH2--Cl

N

CH2--CH2--Cl

CH2--CH2--Cl

H3C

In 1942, Nitrogen Mustard chlormethine, became the first antineoplastic chemotherapeutic agent used medicinally.

This agent forms a covalent bond with DNA,

Alkylating specific sites on purine (A, G) bases of DNA

Crosslinking DNA

Causing cell death

This ALKYLATING AGENT is the pioneer of Antineoplastic Chemotherapy

4 (nucleo)bases: A G C T

Base + deoxyribose sugar = nucleoside

Base + deoxyribose sugar + phosphate =

nucleotide

Nucleotide polymers = nucleic acid (DNA)

Deoxyribonucleic acid (DNA)

Nuceotide polymers:

DNA double helix

CH3

N7 methyl guanine

Nuceotide polymers:

DNA double helix Pyrimidines

Purines

Alkylating agents

The oldest class of anticancer drugs

Major cornerstone of treatment for leukaemias, lymphomas and solid

tumours.

Other nitrogen mustard analogues:

Chlorambucil

Melphalan,

Ifosfamide

Cyclophosphamide:

One of most widely used cytotoxic agents in combination or sequentially with other antineoplastic drugs. Used to treat cancers of:

Brain, breast, bladder, cervix, endometrium, lung, testis, ovary, Burkitt`s, and other

non-Hodgkin`s lymphoma, multiple myeloma, gestational trophoblastic tumours,

childhood malignancies neuroblastoma, retinoblastoma, Wilms`, Ewing`s, leukaemias: CLL, ALL, CML, AML.

NCH2--CH2--Cl

CH2--CH2--ClHO2C(H2C)3

NH

P

O

NCH2--CH2--Cl

CH2--CH2--Cl

O

Cyclophospahmide - Mechanism of action:

Cyclophosphamide is a prodrug requiring biotransformation by

cytochrome P450 (CYP 3A4 in the liver) to exert toxicity.

NH

P

O

NCH2--CH2--Cl

CH2--CH2--Cl

ONH

P

O

NCH2--CH2--Cl

CH2--CH2--Cl

O

HO

CYP 3A4

4-OH-CPA

NCH2--CH2--Cl

CH2--CH2--ClP

O

H2N

O-

H

O

+

Phosphoramide mustard + acrolein

active alkylating species unwanted by-product

Cross-links RNA and DNA haemorrhagic cystitis

Alkylating agents 2: Nitrosourea derivatives

The anticancer activity of this class of compounds was discovered in 1959 at the NCI

Activity against solid and non-solid tumours

Lipophilic allowing access across BBB

Chloroethylate DNA

Therapeutic efficacy limited by development of resistance, involving multiple repair pathways

ClNNO

NH

Cl

O





Chloroethylate DNA


ClNNO

NH

Cl

OCarmustine

Used alone or adjuvant treatment of

brain, colon, lung cancers, Hodgkin`s,

non-Hodgkin`s lymphoma, melanoma,

multiple myeloma, mycosis fungoides.





Chloroethylate DNA


Carmustine

Used alone or adjuvant treatment of

brain, colon, lung cancers, Hodgkin`s,

non-Hodgkin`s lymphoma, melanoma,

multiple myeloma, mycosis fungoides.

Antineoplastic and toxic effects caused by active metabolites. Chloroethyl carbonium

ion leads to formation of DNA cross links during all phases of cell cycle, causing cell

cycle arrest and apoptosis.

N N

NN

N

CH3

H2NOC

O

Alkylating agent

Treatment of high grade Glioma recurrent anaplastic astrocytoma

and gliobastoma multiforme

Malignant melanoma and brain

metastases from solid tumours

Alkylating agents 3: Triazenes

NH

NN

N

H2NOC

N

CH3

CH3

Alkylating agent

Treatment of metastatic

malignant melanoma (response

rate 15-25%)

Hodgkin`s lymphoma (in combination with doxorubicin,

bleomycin and vinblastine)

Dacarbazine Temozolomide

Malignant Melanoma

Ed Newlands

11C (Me)-Temozolomide in positron emission tomography (PET) after oral administration

Saleem et al, Cancer Res., 2003, 63, 2409-2415

11C methylation of DNA

N N

N

N

O

N

H2NOC

Me14C 11C

11C

15N

Isotopic labelling of temozolomide

Expired 11CO2

Expired N2

NH

N

H2NOC

14C

NH2

Excretion

Protonation

N N

NN

N

CH3

H2NOC

O

Major Mechanism of Resistance inherent or acquired:

Repair of methylated DNA O6methyl guanine by methyl guanine methyl transferase MGMT.

Tumours whose cells express MGMT are resistant to

Temozolomide

Alkylating Agents

Transfer an alkyl group onto DNA

CH3 methyl

CH3CH2Cl chloroethyl

DNA damage :

in S phase (block DNA synthesis), G2

arrest

DNA single strand breaks- double

strand breaks.

Cross link the 2 strands.

Antimetabolites

Bastion of Cancer Chemotherapy

Chemicals structurally similar to either FOLATE or NUCLEOBASES

DNA building blocks

FOLIC ACID growth factor, provides

carbon atoms for nucleotide precursors

in synthesis of RNA and DNA

FOLATE ANTAGONISTS inhibit one

(or more) folate-dependent enzymes

Purine antagonists inhibit

production of A and G in DNA and

RNA

Guanine

Adenine

Cytosine

Thymine

Uracil

Pyrimidine antagonists block

synthesis of C and T in DNA; C

and U in RNA

Thus, the antimetabolites

BLOCK DNA SYNTHESIS

Methotrexate

Most commonly used folate antagonist.

Enters cell via folate receptors

Binds DHFR

Inhibits synthesis of FH4

Cell cannot create new purine and thymidine nucleotides

DNA and RNA synthesis blocked

Methotrexate

Administered alone or in combination with other chemotherapeutic agents to treat:

leukaemia, lymphoma

gestational choriocarcinoma

solid tumours: breast, head and neck, lung, bladder,

oesophagus

Methotrexate can be given by many routes: po, iv, sc, im, intra-arterial, intrathecal.

It is the only cytotoxic drug for which there is a role for routine PK monitoring:

leucovorin / folinic acid rescue bypasses inhibited DHFR,

replenishing intracellular reduced folate pools.

Other clinical folate antagonists: Permetrexed, Ralitrexed, Nolatrexed

Pyrimidine Analogues

5-FLUOROURACIL and CAPECITABINE decrease the biosynthesis of

pyrimidine nucleotides by inhibiting thymidylate synthase, the enzyme

that catalyses the rate limiting step in DNA synthesis.

CAPECITABINE is converted to 5-FLUOROURACIL in cancer cells

5-FU cannot be methylated by thymidylate synthase, causing sustained

inhibition of the enzyme and decreased production of Thymine.

5-FU is incorporated into DNA (via dUMP or dTMP) or RNA (via UTP),

leading to cytotoxicity via DNA strand breakage and decrease in protein

synthesis

5-FU

Pyrimidine Analogues

5-FLUOROURACIL and CAPECITABINE decrease the biosynthesis of

pyrimidine nucleotides by inhibiting thymidylate synthase, the enzyme

that catalyses the rate limiting step in DNA synthesis.

Clinical Applications:

In a number of iv combination chemotherapies for treatment of bowel,

breast, gastric, oesophageal, pancreatic, head and neck, anal and

ovarian cancers.

Oral analogues are also used, and topical application for superficial basal

cell carcinoma.

5-FU

Additional pyrimidine antagonists: Gemcitabine, Tegafur, Sapacitabine

Purine Antagonists

In clinical use since 1953

Mercaptopurine

Adenine analogue

Treatment of ALL, AML, Hodgkin`s lymphoma in children,

lymphoblastic lymphoma.

Dose-related toxicity bone marrow suppresssion

Thioguanine

Synthetic guanine analogue inhibition of purine synthesis

Antimetabolites

Inhibit production of DNA building blocks

Antifolates

Purine antagonists

Pyrimidine antagonists

Act in G1 cell cycle phase

(Prevent DNA synthesis)

Antimicrotubule agents

The Company of Biologists Ltd 2005

Paralyse tubulin (which forms

microtubules) or microtubules

Critical for cell division

Block cell cycle during Mitosis

Microtubules allow segregation of chromosomes during mitosis

Antimicrotubule agents 1

Paclitaxel (Taxol) Isolated from Pacific Yew:

Taxus brevifolia

Problem: limited supply and extraction

Semi-synthetic Docetaxel (Taxotere) from the more abundant taxane precursor

found in needles of European Yew:

Taxus baccata

Taxanes

Microtubule poisons

- stabilise microtubules

- inhibit depolymerisation

cause G2/M cell cycle arrest

Treatment of Breast, Ovarian, Lung carcinomas

Antimicrotubule agents 2

Vinca Alkaloids

Isolated from Madagascan

periwinkle Catharanthas roseus.

> 70 alkaloids identified in sap

from C roseus used historically in

folk (traditional) medicine.

Vincristine (Oncovin) Vinblastine (Velbe)

Used in treatment of leukaemia, lymphoma,

melanoma, soft tissue sarcoma,

neuroblastoma, breast and lung cancers.

Mechanism of action:

Bind -tubulin

Inhibit tubulin polymerisation

Destabilise (depolymerise)

microtubules:

Destruction of mitotic spindle, leaving

cells stranded in mitosis.


The Company of Biologists Ltd 2005

Tubulin Microtubules Polymerisation

depolymerisation

Vinca alkaloids

Taxanes

Preventing cells from completing mitosis

control

taxol

vincristine


Prevent successful mitoses

Cytotoxic chemotherapy So far.

Alkylating agents Nitrogen mustard

Cyclophosphamide

Temozolomide



Cyclophosphamide

Temozolomide

Antimetabolites Methotrexate folate antagonist 5-Fluorouracil pyrimidine antagonist Thioguanine purine antagonist



Cyclophosphamide

Temozolomide

Antimetabolites Methotrexate folate antagonist 5-Fluorouracil pyrimidine antagonist Thioguanine purine antagonist

Spindle poisons Taxanes stabilise microtubules Vinca alkaloids inhibit tubulin polymerisation

Anticancer Therapeutics: Ed Sotiris Missailidis, Wiley-Blackwell, 2008.

Platinum drugs

Pt

H3N

Cl

Cl

H3N

Cisplatin

Discovery 1965

Clinical application 1970s

Intravenous short term infusion in saline

Treatment of solid/epithelial malignancies:

First line and in combination: testicular, ovarian, cervix uterus, lung, head and neck, oesphagus, stomach, colon,

bladder.

Second line: advanced breast, pancreas, liver, kidney, prostate,

peritoneal and pleural mesotheliomas.

Cisplatin: Mechanism of Action:

Cisplatin crosslinks DNA causing interstrand and intrastrand GG,

AG Pt adducts.

Replication inhibition,

Transcription inhibition,

Cell cycle arrest,

DNA repair mechanisms

triggered - failure,

Cell Death

Carboplatin

Adverse Cisplatin reactions

Renal, GastroIntestinal Toxicity, Peripheral Neuropathy.

Markedly less toxic to kidneys and nervous system causing less nausea and vomiting.

Platinum agents

Cross link DNA

Damage triggers cell cycle arrest and DNA repair mechanisms

Which fail (initially)

Activating apoptosis

S cell cycle phase

Antitumour Antibiotics

Substances produced by micro-organisms (or plants, or

marine invertebrates) that exert anticancer activity by

DNA interaction.

Multiple modes of action, may be subject to alternative

classification - alkylating agents

- DNA cleavage agents

- non covalent binding agents

- topoisomerase inhibitors

Actinomycin D

Mitomycin C

Bleomycin

Doxorubicin - anthracycline

Etoposide - podophyllotoxin

Irinotecan - camptothecin

Bleomycin

Linear glycosylated peptide antibiotic

Isolated from Streptomyces verticellus in 1960s

There are > 200 members of bleomycin family,

blenoxane = bleomycin A2 + bleomycin B2

Treatment of: Hodgkin`s, non-Hodgkin`s lymphomas, squamous

cell carcinoma, testicular carcinoma, malignant

pleural effusions, Kaposi`s sarcoma.

Mechanism of Action:

DNA damage generation of DNA Double Strand Breaks (DSBs) and single strand breaks (SSBs).

RNA cleavage caused by bleomycin-induced oxidative damage.

Nucleic acid cleavage dependent on presence of Fe2+ and molecular

oxygen.

Bleomycin

Linear glycosylated peptide antibiotic

Isolated from Streptomyces verticellus in 1960s

There are > 200 members of bleomycin family,

blenoxane = bleomycin A2 + bleomycin B2

Treatment of: Hodgkin`s, non-Hodgkin`s lymphomas, squamous

cell carcinoma, testicular carcinoma, malignant

pleural effusions, Kaposi`s sarcoma.

Serious Adverse Reaction:

Cumulative pulmonary toxicity Lung fibrosis

Mortality in 1-2% bleomycin treated patients.

Manageable adverse reactions:

nausea, vomiting, appetite loss, alopoecia, allergic reactions, skin damage

Doxorubicin

Anthracycline antibiotic tetracyclic chromophore with

anthraquinone motif.

Antibacterial,

Immunosuppressive,

Antiparasitic and wide spectrum

Antitumour activity.

First isolated in 1960s from

cultures of Streptomyces peucetius.

Large scale prep developed in 1970s involve semisynthetic

process starting from daunoubicin

Doxorubicin and Daunorubicin, used clinically for four

decades, are amongst most efficient antitumour drugs.

Doxorubicin

Frequent Indications include:

Breast, ovarian, transitional cell bladder cancer, bronchogenic

lung cancer, thyroid and gastric cancer, soft tissue and

osteogenic sarcomas, neuroblastoma, Wilms` tumour,

malignant lymphoma (Hodgkin`s and non Hodgkin`s, acute

myeoloblastic leukaemia, acute lymphoblastic leukaemia and

Kaposi`s sarcoma

Clinical Limitations:

Development of Acquired Resistance

Cardiotoxicity. Dilative cardiomyopathy and congestive heart

failure are cumulative adverse effects that appear (usually) after 1 year.

To prevent these severe reactions, a maximum cumulative dose of 600

mg/m2 has been established.

Less severe side effects include nausea, vomiting, diarrhoea, loss of

appetite, hair loss and skin damage.

Mechanism of Action of Doxorubicin

Doxorubicin is a Topoisomerase II poison/inhibitor

DNA exists in cells as a supercoiled double helix which must unwind during

transcription and replication.

Topoisomerse enzymes catalyse changes in DNA topology.

Doxorubicin inhibits Topoisomerase II-catalysed DNA relaxation

Doxorubicin binds strongly to duplex DNA by intercalation selectively at C-G sequences.

generation of DNA DSBs inhibiton of religation of cleaved duplex

Halted DNA synthesis

Cell Death

Doxorubicin leads to generation of Reactive Oxygen Species (ROS) which damage DNA

Formation of DNA adducts and crosslinks

Inhibition of DNA and RNA synthesis

Podophyllotoxin isolated from Podophyllum

peltatum Mayapple 1880

Potent antitumour activity with severe side effects

no clinical use

Podophyllotoxin - Etoposide

Research led to

synthesis of

Podophyllotoxin

analogues Etposide,

Teniposide

Mechanism of Action

Podophyllotoxin: Binds tubulin and inhibits mitotic spindle assembly

Etoposide and Teniposide poison the Topoisomerase II-DNA complex.

(forming a ternary complex) and prevent re-ligation of DNA

DNA Double Strand Breaks

Cell Death

Etoposide Clinical Applications

Main indications are for testicular and lung cancers

Non Hodgkin`s, Hodgkin`s lymphoma, AML, ALL, CML, mycosis

fungoides, Wilms`, neuroblastoma, Kaposi`s, gestational trophoblastic

tumours, ovarian germ cell tumours,brain and refractory breast cancer.

Dose related and limiting myelosuppression. Bone marrow recovery

usually complete (3 weeks).

Camptothecin

Pentacyclic antitumour antibiotic isolated

1966 from alkaloid extracts of Camptotheca acuminata.

Remarkable activity against murine

leukaemia models (NCI)

Mechanism of Action

Camptothecin binds and stabilises DNA-Topisomerase I complex,

inhibiting religation of cleaved DNA strands, blocking DNA

synthesis.

In the 1990s, water soluble camptothecin analogues were

synthesised, demonstrating Topo I inhibition and potent antitumour

activity: Topotecan and Irinotecan have reached the clinic.

Irinotecan

Approved in Japan in 1994

lung,

cervical

ovarian cancers

Subsequently in Europe and US for

treatment of Colorectal cancers.

Side effects: diarrhoea, neutropaenia

Novel camptothecin analogues under clinical evaluation including

liposome-encapsulated camptothecins.

So far

DNA alkylators Platinum agents

Antimetabolites Antitumour antibiotics

Tubulin inhibitors Topisomerase inhibitors

Cytotoxic Chemotherapy targets rapidly dividing cells

DNA alkylators Platinum agents

Antimetabolites Antitumour antibiotics

Tubulin inhibitors Topisomerase inhibitors

Cytotoxic Chemotherapy targets rapidly dividing cells

Dose limiting toxicity: GI, haematological, renal, cutaneous toxicities:

Cells which divide rapidly under normal circumstances vulnerable

Bone marrow - myelosuppression

Digestive tract - mucositis

Hair follicles - alopecia

Lack of clinical efficacy

Drug resistance

inherent, acquired

.

Cytotoxic Chemotherapy: Limitations

Clinical mechanisms of resistance

Decreased drug uptake

down regulation of Cu transporting pump decreased intracellular Cisplatin concentrations and reduced Cisplatin toxicity

Enhanced drug efflux

In 1976, the MultiDrug Resistance protein-1 (MDR-1; P-

glycoprotein (P-gp); ABCB1) was

described.

P-gp pumps out of the cell a large number of broadly active

cytotoxic chemotherapeutic agents.

Cells overexpressing Pgp possess a

multidrug resistant phenotype.

Enhanced drug efflux

ATP binding casette (ABC) protein pumps commonly overexpressed in resistant

tumours, capable of transporting anticancer agents with distinct mechanisms

of action.

ABCB1 (P-gp); MRP-1 (multiple drug resistance protein-1; ABCC1); BCRP

(breast cancer resistance protein, ABCG2); MRP-5.

Clinical mechanism of resistance

Decreased drug uptake

Enhanced drug efflux (P-gp)

Altered target expression

upregulated transcription and overexpression of DHFR in response to Methorexate treatment

DNA repair MGMT removes and repairs alkylated DNA bases (Temozolomide)

Failure to activate (pro)drug (cytochrome P-450)

Metabolic drug inactivation

Mutations / altered activity of drug target

(decreased topoisomerase II-etoposide binding affinity;

Tubulin mutations)

Combination Chemotherapy

Treatment with a number of agents / regimes

simultaneously / sequentially with DISTINCT

mechanisms of action:

To eradicate tumour cells - heterogenous disease

Prevent emergence of acquired resistance

Limit toxicities / spare normal cells

Acute Lymphoblastic Leukaemia

80% childhood leukaemia

85% successful treatment

Combination treatment comprises:

Intrathecal MTX - antifolate antimetabolite

Vincristine vinca alkaloid

Daunorubicin antitumour antibiotic

Steroids enhance chemotherapy efficacy, wellbeing, combat tiredness,

anti-sickness, improve apetite, balance body salts, water

L-Asparaginase - an enzyme that destroys asparagine external to the

cell. Normal cells are able to make all the asparagine they need

internally whereas tumour cells become depleted rapidly and die.

Radiotherapy

Combination Therapy Breast Cancer

Surgery, Radiotherapy, Chemotherapy.

Cyclophosphamide alkylating agent

Epirubicin, Doxorubicin antibiotic, DNA intercalator

5FU antipyrimidine

Methotrexate antifolate

Mitoxantrone topoisomerase II inhibitor

Taxol antimicrotubule

Gemcitabine antipyrimidine

Tamoxifen (Hormone therapy; Herceptin, targeted, biological therapy.

Understand the mechanisms of action of major clinically used cytotoxic anticancer drugs.

Appreciate the side effects associated with chemotherapeutic agents and their cause.

A knowledge of mechanisms of acquired/inherent resistance to chemotherapeutic agents

Appreciate rationale underpinning combination therapy.

Summary Slide

Objectives: Target-directed therapy

Be aware of general treatment strategies.

Understand the mechanisms of action of major clinically used anticancer drugs.

Rationale behind target-directed therapy.

Knowledge of example molecularly targeted therapies and mechanisms of action.

A knowledge of mechanisms of acquired resistance to targeted agents, and appreciate rationale underpinning combination therapy.

Appreciate the side effects associated with chemotherapeutic

agents and their cause.

Cytotoxic Chemotherapy

Targets rapidly dividing cells (DNA)

DNA alkylators (S; cyclophosphamide; temozolomide)

Antimetabolites (G1; 5-FU, methotrexate)

Topisomerase inhibitors (etoposide)

Antitumour antibiotics (S; bleomycin, doxorubicin)

Tubulin inhibitors (G2/M; vincristine, taxol)

Limitations

Dose limiting side effects:

GI, haematological, renal, cutaneous toxicities

Drug resistance

Lack of clinical efficacy

Aim

To develop targeted agents that are tumour specific with decreased

toxicity profiles than chemotherapeutic agents.

Target-directed drug discovery

Advances in cancer cell and molecular biology have led to identification

of carcinogenic oncogenes and elucidation of cancer signalling networks

Patient / tumour

selection

development of

target-directed agents

Key Signalling Cascades in tumourigenesis

Workman, P. and Kaye, S.B. (2002) Translating basic cancer research into new

cancer therapeutics. Trends. Mol. Med. 8(4), S1-S9.

Workman, P. (2005) Genomics and the second golden era of cancer drug development. Molecular

Biosystems 1(1), 17-26.

Target-directed drug discovery

identification of a validated biological target (normally a protein)

a molecule hunt, typically involving a high-throughput screening

hit-to-lead development to identify (a) lead compound(s)

lead development (involving in vivo testing and optimisation of ADMET properties)

[Absorption, Distribution, Metabolism, Excretion, Toxicity].

clinical trials with appropriate pharmacodynamic (PD) endpoints

Tyrosine kinases (TKs) encoded by proto-oncogenes - are

important mediators of signalling cascades:

Key roles in growth, differentiation, metabolism and apoptosis

TK activity is tightly regulated in normal cells

Role of TKs in pathophysiology of cancer:

Mutation(s), overexpression of TKs (carcinogenic oncogenes)

lead to malignant growth.

Block constitutive activation of TKs in cancer cells:

Selective Small Molecule and

Monoclonal Antibody Inhibitors:

Tyrosine Kinases - Roles and significance in Cancer.

HER2

} EGFR

bcr/abl

Small molecule RTK Antibody

Gleevec bcr/abl

Vemurafenib BRAF

HER2 Herceptin

Iressa EGFR Erbitux

Tarceva

Sunitinib VEGFR Avastin

Tyrosine Kinase inhibitors examples

Targeted treatment for:

CML Melanoma Breast Prostate NSCLC CRC

q 34

q 11 bcr

c-abl proto-oncogene

145 kDA

Chr 9 22 9q+ Ph1

t (9;22)

Pathogenesis of Chronic Myelogenous Leukaemia

bcr-abl 210 kDa

tyrosine kinase activity

constitutively active

9q+ Ph1

The Gleevec Story:

Bcr-Abl a Good Target

A distinct chromosomal translocation the Philadelphia chromosome

Bcr-Abl gene formed by juxtaposition of c-Abl oncogene on chromosome 9 with the Bcr oncogene on chromosome 22

Resulting oncoprotein with elevated tyrosine kinase activity seen in 95% of patients with chronic myelogenous leukaemia (CML)

A distinct drug target clearly differing in activity between normal and leukaemic cells

Gleevec: Chemical Optimisation

Initial compound identified in high-throughput screen

Promising lead-like properties high potential for chemical diversity

Lead eventually to Gleevec (SAR studies aided by molecular modelling)

Gleevec binds in ATP pocket, induces apoptosis in CML cells and causes dose-dependent inhibition of tumour growth in xenograft mouse models

N

N N

H

N

Protein kinase Cinhibitor

N

N N

H

N

Me

N

H

O

N

N

STI571 (Gleevec)

(Glivec; Imatinib)

Gleevec: Mechanism of Action

Initial compound identified in high-throughput screen

Promising lead-like properties high potential for chemical diversity

Lead eventually to Gleevec (SAR studies aided by molecular modelling)

Gleevec binds in ATP pocket, induces apoptosis in CML cells and causes dose-dependent inhibition of tumour growth in xenograft mouse models

The Gleevec Story: Clinical Activity

Outstanding clinical activity in CML patients, particularly in chronic phase of disease (95% response in Phase II human trials)

Much lower response (29%) and high relapse rate in later stages of disease (blast crisis)

Other tyrosine kinase receptor targets of Gleevec include c-kit in GastroIntestinal Stromal Tumours (GIST), and Platelet Derived

Growth Factor (PDGF) receptor (variety of tumours)

Drug resistance in late stage disease mutations in ATP binding pocket

Novel agents - active in Gleevec-resistant disease:

( Nilotinib, Dasatinib. Weisberg et al, Nature Reviews cancer 7 p345 2007)

Point mutation: B-RAF

- a single base is altered

at position 1799 thymine is replaced by adenine

- an altered codon


Valine (V) is replaced by glutamate (E) at codon 600

protein function

Constitutive activation

V600E mutation

drives pathogenesis

of > 60% Metastatic

Melanoma

VEMURAFENIB

V600E mutated BRAF inhibition

August 2011: FDA approves Zelboraf (vemurafenib) and companion

diagnostic test for BRAF mutation-positive metastatic

melanoma, a deadly form of skin cancer.

VEMURAFENIB

V600E mutated BRAF inhibition

Mechanisms of resistance to vemurafenib

Cancer cells may overexpress a cell surface protein PDGFRB creating an alternate survival pathway.

NRAS mutation, reactivating the normal BRAF survival pathway

Vemurafenib vs Dacarbazine in metastatic melanoma patients

Chapman et al NEJM 2011

75% invasive breast cancers are classified ER+;

65% are ER+ and PR+

Treatment strategies for ER+ breast cancer:

Inhibition of oestrogen synthesis

Oestrogen receptor blockade

Growth of ER+ breast tumours is stimulated by oestrogen.

Breast Cancer UK statistics:

In 2008 12,000 women and 70 men died from breast cancer

Targeting Oestrogen synthesis in ER+ Breast Cancer

Aromatase inhibitors

X X

Oestrogen receptor blockade

Tamoxifen, Raloxifene

Anastrazole

(Arimidex)

Tamoxifen

Treatment strategies for ER+ breast cancer:

Inhibition of oestrogen synthesis Oestrogen receptor blockade

In 25-30% metastatic breast cancer patients the human

epidermal growth factor receptor 2 - HER2 protein is

overexpressed through amplification of the HER2 gene.

HER2 signaling, particularly

activation of downstream effector

pathways including the

Ras/Raf/MAPK and PI3K/Akt

pathways, has been implicated in

the pathogenesis of breast

cancer.

HER2+ overexpression is

associated with a poorer

prognosis than HER2- tumours.

These cancers are less

responsive to conventional

chemotherapy and hormonal

therapy.

Herceptin a humanised monoclonal antibody

specifically blocks HER2 on the surface of breast

cancer cells and turns off the permanently on signal for cell division.

GFR

Ras PI3K

Raf AKT

Mek mTOR

Proliferation

apoptosis resistance

invasion, angiogenesis

protein translation

PTEN

Herceptin increases the survival

time of women with advanced

breast cancer.

Androgen-dependent prostate cancer:

Inhibition of androgen synthesis:

Critical role of CYP 17 in androgen synthesis

Inhibition of CYP17 hydroxylase and lyase activities by Abiraterone

Treatment for Androgen-dependent prostate cancer:

Abiraterone

Inhibition of prostate cancer cell proliferation

Targeted therapy for the treatment of Non Small

Cell Lung Cancer

Background

NSCLC most common form of lung cancer leading cause of cancer mortality Too advanced to be operable in ~50% patients First-line platinum agents give only modest increase in

survival

Limited efficacy and side effects of cytotoxic chemotherapy need for new therapies

Aim

To achieve cancer specific effects by targeting aberrant molecular pathways underlying tumour

growth to improve efficacy and minimise side effects

Activation of EGFR is involved in NSCLC growth and progression:

Inhibition of apoptosis Proliferation Angiogenesis Metastasis

Lancet Oncology 2006; 7:499

Aberrant signalling important in development and

progression of NSCLC

EGFR expressed in up to 93% and overexpressed in ~45% of NSCLCs Level of EGFR expression correlates with poor prognosis and reduced

survival

good target

Lancet Oncology 2006; 7:499

Targeting EGFR

Monoclonal antibodies directed against extracellular ligand binding domain e.g. cetuximab (Erbitux) prevent ligand binding

Small molecule selective inhibitors of intracellular TK domain e.g. gefitinib (Iressa; erlotinib (Tarceva) block autophosphorylation

Downstream

Signal

Transduction

Inhibited

EGFR Inhibitors: IressaTM and TarcevaTM

Gefitinib Erlotinib

N

N

N

F

Cl

O

MeO

N

OH

ZD1839 (Iressa)

N

N

N

O

O

H

OSI-774 (Tarceva)

O

O

Synthetic small molecule receptor tyrosine kinase inhibitor

Compete with ATP binding to intracellular TK domain of EGFR

Inhibit receptor autophosphorylation

Block downstream signal transduction

Orally available

Tarceva: place in therapy

Approved November 2004 for 2nd line tx of advanced NSCLC

Antitumour activity and symptom relief (improved quality of life) in

patients where standard chemotx

has failed; mild adverse effects

(skin rash, diarrhoea)

Erlotinib Placebo

End Points n = 488 n = 243 P value

Progression-free survival (months)

2.2 1.8 < 0.001

Overall survival (months)

6.7 4.7 < 0.001

1-year survival (%) 31 22

NSCLC responders vs. non-responders to EGFRi

Somatic mutations in the TK domain of EGFR correlates with subset of

patients who are exquisitely sensitive:

Women; never smokers; east Asian descent; adenocarcinoma;

bronchoalveolar carcinoma.

Tarceva

Efficacy of Gefitinib vs C/P in East Asian Patients

with NSCLC

Objective Response Rate (ORR) Gefitinib C/P P-value

Intent-to-treat population

(n = 609; 608) 43.0% 32.2%

Personalised Medicine Reduces Ineffective

Treatment in Colon Cancer

KRAS mutation testing in metastatic colorectal cancer

World J Gastroenterol. 2012 October 7; 18(37): 51715180.

Published online 2012 October 7. doi: 10.3748/wjg.v18.i37.5171

PMCID: PMC3468848

kras Testing

Do Not Treat

Treat with Erbitux

Treat with Erbitux

Treatment

Success

In situ carcinoma: undetectable microscopic mass of tumour cells

Tumour cells secrete molecules

(e.g. vascular endothelial growth

factor, VEGF)

Signalling activates genes/ protein

synthesis in normal host tissue

encouraging growth of new blood

vessels to the tumour

Judah Folkman 1933-2008 Founder anti-angiogenic therapy

One of the Hallmarks of Cancer: sustained Angiogenesis

promotes: Growth of primary tumour Metastasis

Hypoxia, transforming (oncogenic,

tumour suppressor) mutation:

HER2,ras, P53, PTEN, PI3K/AKT, NO, bFGF, Il-8, EGF, IGF-1, PDGF, COX-2, H2O2

VEGF

synthesis/release

P

P

P

P

Binding of VEGF to

VEGFR

VEGFR activation

Survival, proliferation,

migration

ANGIOGENESIS

Role of VEGF in Angiogenesis / Tumourigenesis

Potent mitogen for vascular

endothelial cells

Mediates the secretion and activation of enzymes which

degrade the extracellular matrix

e.g. matrix metalloproteinases,

collagenase

Survival factor for endothelial cells through inhibition of

apoptosis

Modulates endothelial cell migration

to sites of angiogenesis

Vascular maintenance

Lymphangiogenesis

VEGF

VEGF a good target ?

Key promoter of metastasis and central role in tumour growth

VEGF expression is increased in the majority of cancers examined to date

Overexpression correlates with risk of recurrence and poor prognosis

Drugs targeting VEGF activity at endothelial cells do not need to penetrate tumours

Drug resistance less likely than with traditional chemotherapeutics: greater genetic stability of endothelial cell compared to cancer cell

Targeting VEGF(R)

VEGF/VEGFR blockade by

monoclonal antibodies

Inhibition of receptor

signalling by small molecule

tyrosine kinase inhibitors

VEGF

Kinase

inhibitors Anti-VEGFR-1/2

VEGF receptor

Aptamer

Anti-VEGF

SiRNA

decoy receptor

Ribozyme targeting

VEGFR mRNA

How to target VEGF

BEVACIZUMAB Avastin;

Humanised neutralising IgG

monoclonal antibody directed

against VEGF

Binds all VEGF isoforms with

high affinity and blocks their

binding to the receptors.

VEGF

Kinase

inhibitors Anti-VEGFR-1/2

VEGF receptor

Aptamer

Anti-VEGF

SiRNA

decoy receptor

Ribozyme targeting

VEGFR mRNA

Place in therapy of Bevacizumab (Avastin)

Metastatic colorectal cancer (mCRC)

The addition of bevacizumab to 5-FU and irinotecan regime

increased survival time by ~ 5

months (30%) (20.3 months

versus 15.6 months; p < 0.001)

Approved (2004) in combination with first-line 5-FU-based

chemotherapy regimens

Bevacizumab plus chemotherapy improved survival in metastatic non-small cell

lung cancer in a randomized clinical trial*

Atkins et al. Nature Reviews Drug Discovery 5, 279280 (April 2006) | doi:10.1038/nrd2012

Small molecule inhibitor of VEGFR: Sunitinib

Results of Phase III trial of Sunitinib in glivec refractory GIST patients.

(G Demetri 2006).

Time to tumour progression

Sunitinib (Sutent) small molecule inhibitor of

VEGFR

Orally available small-molecule inhibitor of VEGFR 1, 2 and 3, PDGFR , , c-kit and flt-3 rich and diverse pharmacology

Phase II trials completed in cytokine-refractory metastatic renal cell cancer

Unusually high rate of objective tumour responses detected - 40%;

stable disease - 27%

Acquired resistance: rapid enhanced migratory and invasive capacity

Targeted therapies for solid tumours?

Gleevec success in CML where a single genetic alteration underpins disease pathogenesis (bcr-abl)

Common solid tumours do not have one defined genetic alteration driving the neoplastic process

Clinically heterogeneous disease

Acquired resistance: Target mutation (bcr-abl),

Elevated target expression (BRAF V600E)

Activation / upregulation of alternative signalling pathways (EGFR MET),

Acquired oncogenic mutations in complementary signal networks (EGFR Ras)

Enhanced cancer cell migration / invasion capacity

Mutation/loss of

FAP gene

APC

DNA

methylation

KRas

mutation

Loss of

P53

Acquisition of

multiple genetic

mutations

Solid Tumourigenesis

Targeting Solid Tumours

Combination of

molecularly-targeted agents with cytotoxic /

radiotherapy

Erbitux (cetuximab)

targets EGFR with

Irinotecan advanced colorectal cancer

Herceptin (Trastuzumab) targets HER2 protein with

paclitaxel HER2+ metastatic breast cancer

Avastin targets VEGF with paclitaxel or

carboplatin in NSCLC

Dual / multiple TK inhibitors

Zactima Sunitinib Sorafenib

Lapatinib: EGFR / HER2 GSK

small molecule Herceptin refractory breast, lung cancer

Capecitabine 5FU prodrug

The Phase III registration trial: Combination

with chemotherapy

Use of chemotherapy plus a monoclonal antibody against HER2 for

metastatic breast cancer that overexpresses HER2

Few studies of metastatic breast cancer demonstrated a

survival advantage of this magnitude.

Slamon DJ et al. N Engl J Med 2001; 344:783-792.

Prior anthracyclines

Herceptin + paclitaxel (n=92)

Paclitaxel (n=96)

Significant improvement in progression-free

survival (primary endpoint)

Summaryso far

The Molecular Mechanisms underpinning tumourigenesis are

Numerous,

Complex,

Not fully understood

Target aberrant proteins

Small molecules

Antibodies

Resistance

Combine cytotoxic and molecular targeted agents

to defeat cancer

Combination Therapy: Lung Cancer


Small cell lung cancer - chemotherapy (responds well; also radiotherapy)

Non small cell lung cancer (NSCLC)

- surgery, radiotherapy,

Biological therapy: EGFR inhibitors

Chemotherapy:

Cisplatin / carboplatin -

Etoposide -

Doxorubicin -

Topotecan -

Vincristine -

Gemcitabine -


Small cell lung cancer - chemotherapy (responds well; also radiotherapy)

Non small cell lung cancer (NSCLC)

- surgery, radiotherapy,

Biological therapy: EGFR inhibitors - Tarceva, Iressa

Chemotherapy:

Cisplatin / carboplatin - cross links DNA

Etoposide - Topo II inhibitor

Doxorubicin - DNA intercalator (heart complications)

Topotecan - Topo I inhibitor (camptothecin derivative)

Vincristine - antimicrotubule agent

Gemcitabine - antipyrimidine

Combination Therapy:

Colorectal (Bowel) Cancer



Surgery (8/10)

Radiotherapy

Chemotherapy

5-fluorouracil (5-FU) -

Oxaliplatin -

Irinotecan -

Biological therapy

Erbitux; Iressa -



Surgery (8/10)

Radiotherapy

Chemotherapy

5-fluorouracil (5-FU) - antipyrimidine

Oxaliplatin - platinum DNA crosslinker

Irinotecan - topoisomerase 1 inhibitor

Biological therapy

Erbitux, Iressa - EGFR inhibitors

B33E11 Complete TB

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