Transcript Diapositive 1 - Cell Biology Promotion

Cancer therapy
IJsbrand Kramer
[email protected]
In this lecture we will treat
- The principles of cancer chemotherapy
- The principles of clinical trials
- The development of novel anti-cancer drugs
- the Abl tyrosine kinase inhibitor Gleevec
- the HER2 receptor-inhibitor Herceptin Fab
Cancer can be treated in four ways:
1) surgical excision,
2) irradiation,
3) chemotherapy and
4) biological response modification.
Cancer chemotherapy takes central stage in the
cure of cancer and for certain tumours, high
survival rates have been achieved.
The first anticancer drugs, the nitrogen
mustards, were initially developed as toxic
gases during the first World War.
Victims of gas attacks were found to have
very low white blood cell counts. It was then
reasoned that these compounds could be
developed as anticancer drugs for the
treatment of leukaemia’s.
These compounds are now known as the
alkylating agents and are still an essential
ingredient of chemotherapy regimes.
Anticancer drugs inhibit cell proliferation
and although effective in combating cancer,
they cause proliferation arrest in both
disordered- and ordered-cells!
Their mode of action is not based on a clear
exploitable difference.
The exploitable difference may reside in the
recovery phase after the treatment
We may define the exploitable difference for
cancer therapy as follows: a reduced capacity of
the cancer cell to repair the damage induced by
chemotherapy agents.
Because of this, cancer cells pass on to their
progenitors an increasing number of defects
(mutations) that in the end prove to be lethal.
Anti-metabolites
Anti-metabolites
Anti-metabolites
Anti-metabolites
Anti-metabolites
Alkylating agents
Mustard gas
(yperite)
Alkylating agents
Alkylating agents
Platinum analogues
Cisplatin (red) linking two
nucleotides (blue)
Platinum analogues
Cytotoxic antibiotics
Inhibitors of microtubule polymerization or depolymerization
Development of new anticancer drugs
New targets and how to test their clinical efficacy?
-Principles of clinical trials
-The development of Gleevec
-The development of Herceptin Fab
Principals of Clinical trials
1 dose response test
2 randomized
3 double blind
4 inclusion of control
Control:
- application of placebo (no drug but this may not always be
possible for ethical reasons (disabling or lethal disease))
- application of existing treatment (the disadvantage of
such an approach is that you have no direct evidence of
the therapeutic action of the drugs)
Principals of Clinical trials
A Phase I Study:
Phase I studies are primarily concerned with assessing the drug's
safety. This initial phase of testing in humans is done in a small
number of healthy volunteers (20 to 100), who are usually paid for
participating in the study. The study is designed to determine
what happens to the drug in the human body--how it is absorbed,
metabolized, and excreted.
A phase I study will investigate adverse
effects that occur as dosage levels are increased. This initial
phase of testing typically takes several months. About 70 percent
of experimental drugs pass this initial phase of testing.
NB: For cancer drugs this phase already contains selected
patients that respond badly to the standard treatment and are in
an advanced state of the disease.
Principals of Clinical trials
A Phase Two Study:
Once a drug has been shown to be safe and a dose response curve
has been established, it must be tested for efficacy in a larger
number of people. This second phase of testing may last from
several months to two years, and involve up to several hundred
patients.
Randomized, double blind and with control.
NB: For cancer therapy a different approach applies; the trial is
not random, the patients are selected by criteria such as severity
of disease and unresponsiveness to standard treatment.
This study will provide the pharmaceutical company and the FDA
comparative information about the relative safety of the new
drug, and its effectiveness (therapeutic index). Only about onethird of experimental drugs successfully complete both phase I
and phase II studies.
Principals of Clinical trials
A Phase Three Study:
In a phase III study, a drug is tested in several hundred to several
thousand patients. This large-scale testing provides the
pharmaceutical company and the FDA with a more thorough
understanding of the drug's effectiveness, benefits, and the range
of possible adverse reactions.
Most phase III studies are randomized and blinded trials.
Phase III studies typically last several years. Seventy to 90 percent
of drugs that enter phase III studies successfully complete this
phase of testing. Once a phase III study is successfully completed, a
pharmaceutical company can request FDA approval for marketing the
drug.
1. Gleevec and the treatment of Chronic
myelogenous lymphoma (CML*)
Chronic myelogenous leukemia (leukemia meaning « white blood »)
results from an acquired (not inherited) chromosomal
translocation between chromosome 9 and 22, resulting in the
formation of a large and very small chromosome, called the
Philadelphia chromosome. What produces this translocation is
not yet understood.
The translocation confers a growth and survival advantage on the
stem cell and this leads to a massive increase of white blood
cells. Unlike acute myelogenous leukemia, chronic myelogenous
leukemia permits the development of mature white blood cells
and platelets that generally can function normally. This important
distinction from acute leukemia accounts for the less severe
early course of the disease.
* Also known as chronic granulocytic, chronic myelocytic or chronic myeloid leukemia
Chronic myelogenous lymphoma (CML)
The disease typically begins with a chronic phase and
progresses to blast crisis over a period of years. At the
time of blast crisis, CML cells often have acquired
secondary genetic abnormalities in addition to Brc-Abl.
Because all patients express the Bcr-Abl protein, in
both chronic and acute phase, it represents an ideal
target for drug therapy
The incidence of CML increases with age: a good
illustration of cancer being an age-related disease
20
40
60
age (years)
80
Chronic myelogenous lymphoma (CML): symptoms
Carriers of the disease tire more easily and may feel
short of breath when physically active. They may have a
pale complexion from anemia. Discomfort on the left side
of the abdomen from an enlarged spleen may be present.
They may experience excessive sweating at night, weight
loss, and inability to tolerate warm temperatures.
Increasingly, the disease is discovered during the course
of a periodic medical examination.
Philadelphia chromosome
Bcr
Abl
So named because this
chromosomal translocation
(Ph1) was discovered in
Philadelphia in 1960.
Bcr
Abl
Bcr stands for breakpoint
cluster region, a site in
chromosome 22 which is
frequently involved in
translocations
Abl stands for Abelson (gene
product homologous to
oncogenic virus carried by
the Abelson leukemia virus
v-Abl)
Fluorescence in situ hybridization, often referred to as FISH, is a method
to identify cells with the 9;22 translocation characteristic of CML
Abl
Bcr
Abl
Bcr
Abl-Bcr
When Abl and Bcr are fused, the red and green fluorescent probes superimpose
and give a yellow signal (so one set of chromosomes is still intact)
The Philadelphia chromosome harbours a fusion gene called Bcr-Abl
The translocation produces a fusion protein Abl-Bcr which is associated
with Chronic Myelogenous Leukemia
Abl has different activation states, from inactive (a) to intermediate
states (c-f) and fully active (b). Bcr-Abl cannot return to an inactive state
(g) and is said to be constitutive active.
Treatment of Chronic Myelogenous Leukemia
Stem Cell Transplantation is applied when all fails (with matching HLA donor)
Treatment of Chronic Myelogenous Leukemia
Interferon-a has been an important addition to the
treatment of CML.
In 2001, the Food and Drug Administration approved
imatinib mesylate (Gleevec™ in the USA, and Glivec™
elsewhere) for patients resistant or unable to tolerate
interferon-a.
The drug has been very effective in this setting and
may become the most common first choice for
treatment in the future.
In search for an inhibitor of Abl
Signal Transduction Inhibitor STI-571
4-(4-METHYL-
PIPERAZIN-1-YLMETHYL)-N-[4-METHYL3-(4-PYRIDIN-3-YL-PYRIMIDIN-2-YLAMINO)-PHENYL]BENZAMIDE (Novartis)
Also known as Gleevec, Glivec or imatinib
Specificity of inhibition
STI-571 inhibits (until today)
- Bcr-Abl
- PDGF-R
- c-kit (receptor for the Stem Cell Factor)
FDA approval (in 2002) for treatment of newly diagnosed patients
with Gleevec
The food and drug administration (FDA) approved Gleevec as a first-line
therapy for CML based on the data obtained from a 12 month international
randomized trial of Interferon-a versus Gleevec (STI-571).
This phase III trial involved 553 patients that were given Gleevec and 553
that were given a standard therapy of Interferon-a and cytarabine (antimetabolite).
The patients treated with Gleevec after one year had significantly fewer
cancerous cells in their blood and bone marrow. The rate of progression was
also decreased.
The lenght of the follow up is still too short to measure long term clinical
benefits (generally presented 5 years survival rates)
Adverse effects of Gleevec treatment
Most of the adverse affects can be managed without
stopping therapy. Among others they are:
- Fluid retention
- Nausea
- Vomiting
- Muscle cramps
- Diarrhoea
-Rashes
and (very rarely)
-heart failure (late onset adverse effect)
Timeline of major CML discoveries and drug development
A-MuLV : Abelson murine leukemia virus
GAG-Abl : fusion product of viral glycosylated antigen with the Abl tyrosine kinase
2. Herceptin Fab and the treatment of Her2-driven
metastatic breast cancer
- The human epidermal growht factor receptor-2 (ERBB2, also
known as neu or Her2) is amplified in 30% of breast cancers.
- Amplification of ERBB2 is associated with an aggressive form of
the disease (metastaticwith shortened overall survival time.
- In vitro experiments have demonstrated a direct role of ERBB2
in the pathogenesis of this cancer
ERBB2 is a member of the family of EGF receptors but, until today, lacks a high
affinity ligand. Amplification of ERBB2 causes cell transformation without the
apparent involvement of a ligand. This may be explained by its « open »
conformation (unlike ERBB1, 3 or 4)
dimerization arm
ERBB2 extracellular domain
ERBB2 extracellular domain + antibody
Example of a clinical trial protocol in which Herceptin (trastuzumab)
has been tested
treatment
control
treatment
control
Trastuzumab 4mg/kg (0.22 gr/person), anti-HER2 Fab fragment
Anthracycline is doxorubucin, inhibitor of DNA polymerase
Cyclophosphamide is a alkylating agent that binds DNA and inhibits DNA polymerase
Paclitaxel is taxol, inhibitor of microtubule depolymerization
Survival rates of metastatic ERBB2-positive breast cancer
The use of trastuzumab (mAb) increases the percentage of survival by 10% after
two years (red lines).