TAPET® : Tumor Amplified Protein Expression Therapy, is a modified Salmonella vector used to deliver anticancer agents directly to tumors.
Q. What is TAPET® and how does it work?
A: TAPET® is live attenuated Salmonella bacteria that
has been shown in animal studies to selectively accumulate in tumor tissue
over normal tissue. Vion seeks to employ TAPET® technologies as a means
of delivering anticancer therapy directly to tumors.
Q. Why and how does TAPET® accumulate in tumors?
A: The TAPET® bacteria move throughout the body but
are generally destroyed by the immune system as they move through normal
body tissue. Once they penetrate a tumor, however, tumor-produced substances
are thought to inhibit the immune system, thereby permitting replication
and accumulation of the bacteria. Tumors also have areas of rapid cell
turnover and low oxygen tension, which provide nutrients and favorable
growth conditions for the bacteria. TAPET® bacteria will replicate
in the tumor by doubling every 30 to 40 minutes, growing to about 100
million to1 billion bacteria per gram of tumor tissue. This represents
1000-fold or more greater concentration of bacteria in tumors compared
to normal tissues.
Q. How will TAPET® treat cancer?
A: Conventional cancer treatments are limited by the amount
of drug that reaches the tumor, and by the toxicities of the drug, since
normal tissues are exposed to similar or higher concentrations of drug
than tumor tissue. Therefore, the cancer drug must be given intermittently
to allow normal tissues to recover, but during this interval the tumor
also recovers from the effects of the cancer drug. The accumulation of
TAPET® bacteria in tumor, and the much higher numbers of bacteria
in tumor compared to normal tissue, suggests that any cancer fighting
agent produced by the bacteria will also be at much higher concentrations
in the tumor compared to normal tissue. Furthermore, because the bacteria
remain in the tumor for prolonged periods, the delivery of the cancer-fighting
agent is continuous.
Vion scientists are taking advantage of the high numbers of bacteria that accumulate
in tumors by engineering the bacteria to produce cancer-fighting substances.
These armed bacteria have already been shown to produce large amounts of a
cancer-fighting substance in animal tumors.
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