Scientists describe the potential mechanisms of action of P-MAPA, a drug that can activate immune system receptors, in an article in Infectious Agents and Cancer
Brazilian drug shows potential against tuberculosis and cancer
August 15, 2012
By Karina Toledo
Agência FAPESP – In an article recently published in Infectious Agents and Cancer, Brazilian and North American researchers showed that a drug developed in Brazil, called P-MAPA, is able to activate certain immune system receptors and helps fight tuberculosis and bladder cancer.
Previous studies have indicated that the molecule, which was derived from the fungus Aspergillus oryzae by the Farmabrasilis research network, has immunomodulating activity, which means that it stimulates the immune system to combat diverse types of tumors and infectious diseases, including malaria, visceral leishmaniasis and some hemorrhagic viruses.
Now, for the first time, the possible mechanisms of action of the drug have been described. In vitro tests with human cells and experiments on animals showed that P-MAPA activates receptors, known as Toll-like receptors, on the cellular membrane. In addition, in rats, the drug modified the expression of the p-53 protein, possibly through regulating its receptors.
“Toll-like receptors are able to recognize fragments of viruses and bacteria as well as molecular factors associated with infectious diseases,” explained Wagner José Fávaro, professor at the Universidade Estadual de Campinas (Unicamp) Biology Institute and advisor for FAPESP scholar Fábio Rodrigues Ferreira Seiva’s post-doctoral work.
These receptors can help diminish tumors in two ways: by inhibiting the formation of blood vessels that supply the region and by recruiting defense cells to attack the tumor.
According to Fávaro, P-MAPA (protein aggregate magnesium-ammonium phospholinoleate-palmitoleate anhydride) acts specifically on subtypes 2 and 4 of the Toll-like receptors. According to the scientific literature, these subtypes could be related to bladder cancer.
“We still aren’t certain if the response triggered by them is favorable or unfavorable. They could act as negative or positive regulators of carcinogenesis, but our results indicate that receptor activation helped with tumor regression,” said Fávaro.
The experiments were performed in rats. The researchers exposed the rats to the carcinogen N-methyl-N-nitrosourea (N-nitro compound), a substance that is also found in cigarettes. After 8 weeks of exposure, the rodents showed pre-malignant and malignant lesions on the bladder.
“This animal model closely resembles what happens in humans. Smokers and people who are exposed to certain chemical substances at work inhale N-nitro and excrete it in their urine. The contact between the carcinogen and the bladder epithelium over time ends up causing cancer,” explained Fávaro.
The animals were then treated for another 8 weeks. The effect of P-MAPA was compared with the BCG (bacillus Calmette-Guerin) vaccine, which was originally used to prevent tuberculosis and is currently considered to be the best treatment for bladder cancer.
“The main treatment for non-muscular invasive cancer, which causes superficial lesions, is to surgically remove the tumor and apply immunotherapy with the BCG vaccine directly on the bladder,” said Fávaro.
In the 1970s, it was discovered that BCG induces a massive immune response, stimulating the production of cells that attack tumors. In the experiment, rats treated with the vaccine showed a 20-30% reduction in tumor size, but the animals continued to have malignant tumors.
In the group that received P-MAPA, tumor size was reduced by 90%. “The animals no longer had malignant and pre-malignant tumors, only inflammatory ones,” said Fávaro.
Another advantage of P-MAPA is the infrequency of side effects observed in studies with many types of animals. “BCG is prepared with attenuated bacilli and is therefore not recommended for patients with immunodeficiency,” he said.
The researcher explained that more than 90% of the patients treated with BCG have side effects that range from slight irritations to allergic reactions, hemodynamic instability and persistent fever. In these cases, treatment must be suspended.
“In animal testing, P-MAPA showed more effective results with fewer side effects. This shows that it could become a very useful treatment,” noted Fávaro.
P-MAPA’s effectiveness in fighting tuberculosis was investigated thanks to a partnership between Farmabrasilis, the National Institute of Allergy and Infectious Diseases (NIAID) and researchers from Colorado State University in the United States.
“First, we performed in vitro tests in which P-MAPA was applied to colonies of the bacteria that cause tuberculosis. The goal was to see if the drug had an antibiotic effect,” said Fávaro.
The result was negative. When compared with the antibiotics normally used to treat tuberculosis, P-MAPA did not prove effective in inhibiting bacillus growth. “However, when it was tested in animals, the immunomodulator was able to significantly reduce the colony-forming units,” he said.
The experiment was performed in rats infected with the tuberculosis-causing bacteria via an aerosol route. In this experiment, P-MAPA treatment was compared with moxifloxacin (fluoroquinolone), a fourth-generation synthetic antibiotic in the final phase of approval by the Food and Drug Administration (FDA), the U.S. drug-regulating agency.
In the group treated with P-MAPA, there was a 28% reduction in bacterial levels. In the moxifloxacin group, the reduction was 40%. The animals treated with both drugs showed a 38% decrease in bacterial counts.
“P-MAPA alone had less effect, but it also caused fewer adverse reactions. The advantage of using the two drugs together is that they show results similar to that of moxifloxacin alone but with fewer side effects,” said Fávaro.
In a number of studies in animals and in preliminary tests in humans, P-MAPA showed low toxicity. No significant side effects have been reported at the experimental dosages.
The Farmabrasilis network, a non-profit organization created in 2001 consisting of scientists from Brazil, Chile, Europe and North America, also performs research on other potential medications. Of their products, P-MAPA is at the most advanced stage of development.
“The next step is to try to prove in tests with human beings that the drug can be a valuable therapeutic option,” said Iseu Nunes, one of the network’s directors.
According to Nunes, the drug could be used together with the BCG vaccine in treating bladder cancer. It could also be used together with antiviral and antibacterial drugs in the treatment of infectious diseases.
Farmabrasilis is the first to adopt the open source model for the development of pharmaceuticals in Brazil and operates under a special intellectual property policy.
“All of the products being developed could be donated for the treatment of neglected diseases and for important public health programs,” said Nunes.
The network relies on donations, national and international partnerships, funding agencies and volunteer work from its members to finance its projects. The P-MAPA tuberculosis studies were funded by Farmabrasilis and NIAID, and the bladder cancer studies were funded by Farmabrasilis, FAPESP and the National Council for Scientific and Technological Development (CNPq).
FAPESP has funded at least five other research projects, some of which have been concluded, studying the effects of P-MAPA in the fight against illnesses such as visceral leishmaniasis in dogs, bladder cancer and the inflammation induced by toxins from the Escherichia coli bacterium.
The article “Effects of P-MAPA Immunomodulator on Toll-Like Receptors and p53: Potential Therapeutic Strategies for Infectious Diseases and Cancer” can be read at www.infectagentscancer.com/content/pdf/1750-9378-7-14.pdf.