Immunotherapy is one of the therapeutic strategies to treat cancer, and vaccines are a key tool to boost the immune system and make it capable of identifying and eliminating cancer cells. In fact, the BCG tuberculosis vaccine has been used for more than 40 years in the treatment of non-muscle invasive bladder cancer (Nmibc). However, this vaccine is not effective in about 40% of patients with this type of tumor, who experience relapses and their disease progresses to a T2 tumor (with muscle invasion).
These patients usually undergo a radical cystectomy, a surgical procedure in which the bladder, prostate, and seminal vesicles are removed. Now, a new vaccine against tuberculosis –MTBVAC–, which has been developed by scientists from Zaragoza, has demonstrated its efficacy as an immunotherapeutic agent to treat bladder cancer in an experimental model in mice.
MTBVAC is the vaccine candidate for tuberculosis created at the University of Zaragoza (Unizar). This vaccine, which, like BCG, uses a live attenuated form of Mycobacterium tuberculosis, the pathogen responsible for the disease, is being tested in a phase III clinical trial, after more than 20 years of research. The study that has demonstrated its effectiveness against bladder cancer has been coordinated by the researcher Nacho Aguiló, from the Mycobacterial Genetics Group of the Department of Microbiology and Preventive Medicine directed by Carlos Martín at the University of Zaragoza, and has been published in the Journal for ImmunoTherapy of Cancer.
A new treatment for bladder tumors
Bladder cancer is the 5th most frequent type of cancer in developed countries, and its incidence is three times higher in men than in women. Non-muscle invasive bladder cancer accounts for around 70% of cases, and many of these patients are given the current tuberculosis vaccine – BCG – intravesically. Hence the importance of finding new, more effective therapeutic options.
“Our vaccine can be a viable alternative to treat this type of tumors, which currently have no cure beyond bladder amputation”
Speaking to Diario Médico, Nacho Aguiló stated: “We are going one step further in our research, as we have focused on one of the real problems that occur with BCG treatment and bladder cancer: there is a group of patients, between 30-40%, who do not respond to this vaccine, and in most of these cases, to avoid recurrences, the option is cystectomy, with all that this implies of postoperative morbidity and loss of quality of life”.
The Unizar team of scientists used a mouse model of bladder cancer resistant to BCG treatment, with which they have verified that the MTBVAC vaccine candidate is superior to BCG as a stimulator of the immune system. In fact, BCG did not work in this experimental model of bladder tumor, while MTBVAC did in 60-70% of the mice.
“These data lead us to conclude that our vaccine can be a viable alternative to treat this type of tumor, which currently has no cure beyond bladder amputation. In addition, based on these results, we do not rule out that the administration of MTBVAC in the first line, instead of BCG, can reduce the percentage of therapeutic failures”. Another important finding of this research is that the combination of the monoclonal antibody pembrolizumab with MTBVAC achieves tumor rejection in 100% of the animals. “We repeated the experiment three times, because we did not believe the results,” adds the expert.
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