Virotherapy: Reprogramming the Measles Virus to Attack- Ovarian cancer

* discoverysedge.mayo.edu/measles/

Summary

Mayo Clinic's Molecular Medicine Program recently launched the first gene
therapy clinical trial in which the entire preclinical cycle concept,
discovery of agent, vector manufacture, toxicology and efficacy studies,
and new drug application—was conducted on Mayo's campus. The project
engineered a measles virus, MV-CEA, which is specific to ovarian cancer,
kills multiple cancer cells, and can be monitored with a simple blood
test. The clinical trial is the first step in assessing its therapeutic
effect for women who have progressive ovarian cancer that has failed to
respond to standard treatment. The project is a fine example of a clear
translational effort from bedside to bench and back to the bedside.

Virotherapy: Reprogramming the Measles Virus to Attack Cancer

"There are multiple components in the new gene therapy vectors and we
can continually improve them because we have control over all stages of
production." Stephen Russell, M.D., Ph.D.

Since his recruitment, in the fall of 1998 from Cambridge University in
England, Stephen Russell, M.D., Ph.D., who directs the Molecular Medicine
Program, has succeeded in building a unique virology and gene therapy
program at Mayo that is now considered to lead the world in researching
the potential of the measles vaccine virus for fighting cancers.

"The environment here is perfect for gene therapy because you need many
different types of expertise to coalesce," says Dr. Russell. "You need
basic scientists to create the agent and test it preclinically. You need
experts to conduct toxicology studies and manufacture the vector under
strict government regulation. You need clinicians who understand the
science to write the clinical protocol and who can nurture it through the
clinical studies. At Mayo we have all of that plus the infrastructure to
support a pipeline of gene therapy studies."

As a hematologist, Dr. Russell has long known that the wild form of
measles can kill blood cancer cells. However, when his team discovered
that the vaccine can also kill most solid organ cancers as well, its value
as a vector—a system through which genes are delivered into target
cells—skyrocketed. The Molecular Medicine team then began the complex
odyssey of designing a new virus. In the process, they invented several
new gene therapy approaches.
Targeting the Tumor, Preserving Healthy Tissue

Kah-Whye Peng, Ph.D., was a post-doctoral fellow when she spearheaded the
project that produced the engineered measles virus now being used in the
clinical trial. She designed studies that demonstrated the measles
virotherapy could shrink a variety of tumors with minimal damage to
healthy tissue.

The team then chose a handful of specific cancers for further testing.
Their choices offer opportunities to test different routes of virus
delivery.

Ovarian cancer tests delivery of the virotherapy directly into the
peritoneal cavity a potential space between membrane that line the
abdominal and pelvic walls because the disease spreads within the
peritoneal cavity but rarely beyond it. Multiple myeloma is ideal for
intravenous delivery because it spreads throughout the body. More
recently, work performed in the laboratory of principal investigator and
oncologist Evanthia Galanis M.D., showed that delivery of measles virus
directly into gliomas had potent antitumor activity. Gliomas, lethal
tumors of the brain, represent a good target for intratumoral delivery of
viral therapies because they rarely metastasize.

Increasing Potency by Cell Fusion

Ovarian cancer cells before (A), and after (B), infection by measles
virus. Infected cells fuse with each other to form large, single masses,
which eventually die.

In 2000, Drs. Russell, Roberto Cattaneo, Ph.D., and Richard Vile, Ph.D.,
invented a new approach that addressed one of the limitations of previous
cancer gene therapies that they affect only the single cells that actually
take up the genes. Their invention exploits the characteristics of viral
fusogenic membrane glycoproteins (FMGs), which produce massive cell death
by merging surrounding cells into a single protoplasmic mass.

"In this way, a single virus-modified cell can cause death of many
surrounding cells," explains Dr. Russell. "We call it bystander killing."

Subsequent advances to the FMG technology have been published in many
peer-reviewed journals, the most recent in Nature Biotechnology in March
2004.
Monitoring Gene Expression

In a May 2002 Nature Medicine paper, Drs. Russell and Peng described
research that created the ability to monitor gene expression
non-invasively an important advance. Dr. Russell explains:

Being able to monitor viral replication is my war cry. One of the
shortcomings of past gene therapy clinical trials is the inability to
understand why it fails was it failure of gene delivery, or did you get
good gene expression and it just didn't work? Was gene expression too good
but you had no way of knowing it and administered repeated toxic doses?
Was it a short-term expression problem and if so, when was expression
switched off? You can't improve the biotechnology if you don't know what
part of it went wrong.

Carcinoembryonic antigen (CEA) is a soluble peptide produced by some
cancers. Because it can be detected in blood tests, clinicians use it to
follow the course of some anti-cancer treatments. Drs. Peng and Russell
genetically engineered the measles virus vector to express the CEA
peptide. The engineered virus, MV-CEA, gives clinicians the ability to
follow the kinetic profile of viral gene expression in those patients
whose tumors do not express CEA. And it gave the investigators the tool
they needed to take their research to the next stage of
translation—vector manufacture, and toxicology and efficacy studies.
Translating cell therapy into patient therapy

Translation requirements, the period between bench and bedside, make for a
long and winding road before a new vector is deemed safe enough to test on
humans.

The degree of expertise and infrastructure necessary to manufacture a gene
or virus therapy pure enough to meet the Food and Drug Administration's
safety standards for testing in humans is painstakingly complex. Once the
vector has been perfected to the point where it warrants clinical testing,
production and purification cycles begin.

Dr. Peng co-directs the toxicology and pharmacology testing lab that
handles the iterative cycles of toxicology testing, in both cell and
animal models, necessary to purify and perfect each new gene or virus
therapy.

"The tox/pharm study is designed to address specific concerns for the
targeted clinical population," says Dr. Peng. "We need to know where the
vector goes and if it persists or is expelled from the body. And we need
to account for the possibility of allergic reaction, inflammation, or
infection caused by the vector or for toxicity caused by expression of the
transgene."

The toxicology and pharmacology team worked with the FDA to find an
acceptable animal species for testing. As further indication of Mayo's
expertise in this field, the FDA's choice was a transgenic mouse model
developed by Dr. Cattaneo.

Mayo's FDA-compliant vector manufacturing facility, directed by Mark
Federspiel, Ph.D., must uphold highly regulated standards of cleanliness
and sterility as they weather many rounds of harvesting, testing, and
purification.

"If we had to contract the manufacturing part of the cycle out, we would
be a long way from being able to provide this experimental therapy for
patients," says Dr. Federspiel. "Having the facility on campus means we
can collaborate on solving problems as they arise."

In the sterile environment of the Mayo Clinic Viral Vector Production
Facility, technicians harvest MV-CEA virus from cells grown in culture.

Dr. Federspiel has developed collaborative relationships with the relevant
advisory boards and works directly with them to address their concerns.
His team has implemented the knowledge derived from manufacturing the
MV-CEA clinical product into subsequent projects, making it possible to
produce purer products with greater efficiency.
Beginning Human Studies

When efficacy studies showed that MV-CEA induced complete regression of 80
percent of ovarian tumors in mice, the team was ready to launch a clinical
trial. It opened in April 2004.

"It's very exciting for our team to be able to take this virotherapy
approach all the way from discovery to a stage where it can help
patients." says Dr. Galanis, the study's principal investigator. "We have
a very active clinical gene transfer and virotherapy program in the
Department of Oncology having treated more than 150 patients with gene or
virus therapy during the last 10 years. But this is the first time we have
developed the vector at Mayo."

Every year, 14,000 women die from ovarian cancer in the United States. The
disease is commonly diagnosed at an advanced stage because early symptoms
are minimal. Patients enrolled in the current study have progressive
ovarian cancer for which the standard treatment radical surgery followed
by chemotherapy—failed.

Mayo's "patient first" motto ensures that the majority of research at Mayo
is motivated by a problem seen at the bedside. In this case, it was Lynn
Hartmann, M.D., and her colleagues in the Gynecologic Oncology clinic who
worked hard to ensure that the Molecular Medicine team chose ovarian
cancer as the first target for translation to the bedside. In fact,
translational funds from the Ovarian Group supported the initial efficacy
work.

Safety is crucial in the first trial for any new drug. Besides meeting
strict FDA requirements applicable to gene therapy trials, the study is
closely monitored by additional safety and advisory committees, including
Mayo's Institutional Review Board.

"It's very exciting for our team to be able to take this virotherapy
approach all the way from discovery to a stage where it can help
patients." Evanthia Galanis, M.D.

"Human studies in gene therapy for cancer have had an excellent safety
record," says Dr. Galanis. "Our studies on mice with the engineered
measles virus showed no evidence of toxicity despite administering 32
times more virus than the highest dose planned for humans. And because we
now have a vector engineered to express the CEA peptide, we can perform
real-time monitoring of the viral replication in patients for the very
first time."

One of the study's goals is to optimize dose amount and timing.

"We deliver the drug into the peritoneal cavity," says Dr. Galanis.
"Ovarian cancer rarely spreads beyond the peritoneal cavity so direct
delivery optimizes contact between the cancer cells and the therapeutic
agent."

Direct delivery into the peritoneal cavity also reduces the possibility of
the virus being neutralized by antibodies produced by the patient as a
result of vaccination or natural infection. However, should any viruses
escape into the circulatory system the patient's immune system provides an
additional safety measure.

The study will take place in the CTSA Clinical Research Unit (CRU), an
outstanding institutional resource that provides an optimal setting for
controlled clinical research studies, including teams of nurses and
technicians specially trained in caring for patients enrolled in human
studies.

Dr. Galanis reiterates why the team is so excited about this project:

"As an oncologist and translational researcher, it is very gratifying to
help create a bridge between the bench and the clinic in order to address
challenging clinical problems. At the end of the day, we hope to develop
better treatments for cancer patients, using measles virotherapy. Ovarian
cancer represents the first step in this effort with other tumors, such as
gliomas to follow."
A New Paradigm

In conventional drug therapy, the new drug is taken through the clinical
trial process without changing it. Dr. Russell sees gene and virotherapy
as an on-going process that requires a different model for human testing.

"It's much like building motor cars—just because you build something
that works does not end the need to design better models," explains Dr.
Russell. "There are multiple components in the new gene therapy vectors
and we can continually improve them because we have control over all
stages of production. We are already working on solutions that will
preempt any problems we might see in the clinical trial."
An Encouraging Future

If tests on smaller numbers of patients show promise, the new therapy for
ovarian cancer will be tested on much larger numbers of patients in a
Phase III trial before gaining FDA approval. Dr. Russell and his team look
forward to partnering with pharmaceutical companies should that happy day
arrive. Partnership with industry allows Mayo to bring its research
advances to patients all over the world.

And it would mean the end of a long quest for Dr. Russell.

"I have had a passion for harnessing the destructive power of viruses and
using them to destroy tumors since my medical school days," says Dr.
Russell. "Coming to Mayo was the opportunity of the century for
translational research."

The MV-MEA project was made possible by the following generous gifts:

* The Harold W. Siebens Foundation, the Donaldson Charitable Trust and
a Fraternal Order of Eagles grant funded the virus construction and
efficacy research.
* George M. Eisenberg Foundation funded the vector production
facility.
* The Harold W. Siebens Foundation and the Commonwealth Cancer
Foundation funded the Toxicology Core
* Additional funding was received from the National Cancer Institute.

Related Links

* Cancer Research
* Virology and Gene Therapy Training Program

Molecular Medicine Faculty

* Noel Caplice, M.D., Ph.D.
* Roberto Cattaneo, Ph.D.
* Mark Federspiel, Ph.D.
* Evanthia Galanis, M.D.
* Kah-Whye Peng, Ph.D.
* Eric Poeschla, M.D.
* Stephen Russell, M.D., Ph.D.
* Robert Simari, M.D.
* Richard Vile, Ph.D.