United States has just
approved a new drug with which it can treat melanoma skin and lymph nodes,
called IMLYGIC (Talimogene Laherparepvec).
IMLYGIC is a genetically
modified herpes simplex virus type 1 injected directly into tumors where it
replicates inside tumors and produces GM-CSF, an immunostimulatory protein.
IMLYGIC then causes the tumor to rupture and die in a process called lysis. The
rupture of the tumor causes the release of tumor-derived antigens, which
together with virally-derived GM-CSF may promote an anti-tumor immune
response.
However, the exact mechanism
of action is unknown and being further investigated.
“Melanoma is a serious disease
that can advance and spread to other parts of the body, where it becomes
difficult to treat,” said Karen Midthun, M.D., director of the FDA’s Center for
Biologics Evaluation and Research. “This approval provides patients and health
care providers with a novel treatment for melanoma.”
This new treatment highlighted
by directly attacking cancer cells and not damage the rest of the other cells
as often happens with most current treatments.
When a cell becomes cancerous
and starts to replicate, the virus defense system is damaged making it
vulnerable. This theory was already known for decades, but this time had not
yet been achieved to implement the idea of modifying viruses to fight cancer.
So what many scientists see this drug is a proof of concept.
IMLYGIC is indicated for the
Local Treatment of Unresectable Cutaneous, Subcutaneous and Nodal Lesions in
Patients With Melanoma Recurrent After Initial Surgery.
Patients Treated With IMLYGIC
Achieved a Significant Increase in Durable Response Rate in Pivotal Study.
The safety and efficacy of
Imlygic were evaluated in a multicenter study of 436 participants with
metastatic melanoma that could not be surgically removed. The participants’
melanoma lesions in the skin and lymph nodes were treated with Imlygic or a
comparator therapy for at least six months, or until there were no remaining
injectable lesions. The study showed that 16.3 percent of the study
participants who received Imlygic experienced a decrease in size of their skin
and lymph node lesions, lasting for a minimum of six months, compared to 2.1
percent of the study participants receiving the comparator therapy. However,
Imlygic has not been shown to improve overall survival or to have an effect on
melanoma that has spread to the brain, bone, liver, lungs, or other internal
organs.
However, Imlygic has not been
shown to improve overall survival or to have an effect on melanoma that has
spread to the brain, bone, liver, lungs, or other internal organs.
Because Imlygic is a modified
live oncolytic herpes virus therapy, herpes virus infection can also occur.
Given this, Imlygic should not be given to individuals with suppressed immune
systems or who are pregnant.
The most common adverse drug
reactions in IMLYGIC treated patients were fatigue, chills, pyrexia, nausea,
influenza-like illness and injection site pain.
Most adverse reactions reported were mild or moderate in severity and
generally resolved within 72 hours. The most common grade 3 or higher adverse
reaction was cellulitis.
But what’s most important about Imlygic and all the other oncolytic viruses in development is probably not their potential as standalone therapies. Virtually everyone working in the field agrees that the biggest potential for these engineered bugs will be in combination treatments, particularly with other types of immune-boosting treatments. Drugs like Yervoy, for example, are called “checkpoint inhibitors” because they block signals that would normally prevent the immune system from attacking cancer. Combining checkpoint inhibitors with oncolytic viruses may free up the immune system to attack cancer from many different angles.
Just a few days before the FDA
approval of Imlygic, the European Medicines Agency issued a positive opinion on
the drug, setting the stage for approval by the European Commission.
“Metastatic melanoma continues to be one of the most difficult-to-treat
cancers, often requiring the use of multiple treatment modalities,” said Sean
Harper, Amgen’s vice president of R&D, in a statement following the ruling.
“Despite recent advances, the five-year survival rate for patients who cannot
be cured with surgery remains unacceptably low, demonstrating the critical need
for additional approaches to control this disease.”
In any case, there are still
some questions to be resolved to move forward. Scientists still do not know how
Imlygic efficiency is due to the effect of the virus itself on cancer cells or
the action of the immune system when it is reactivated. It also remains to be
seen if the immune system attacks only infected cells or virus is able to
recognize any type of cancer cell. It will be interesting to see what the next
steps in this direction.
Amgen said it is available at
an estimated average cost of $65,000. But for melanoma patients who are more
concerned about getting access to new treatment choices than they are about the
financials of the companies providing those drugs, the approval of Imylgic will
likely be welcome news.
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| 21/12/2001 |
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