Millions of Americans take blood pressure medication everyday, but a new hypertension vaccine could change that, if further research supports results from a small study testing the safety and tolerability of the vaccine.
"Despite the fact that effective drugs are available, only about one out of four people has their blood pressure successfully controlled,” said lead study author Dr. Juerg Nussberger, professor of medicine at the University Hospital of the Canton of Vaud, in Lausanne, Switzerland, at the American Heart Association’s Scientific Sessions 2007 in Orlando, Fla.this week.
“Many patients are apparently unable or unwilling to take pills every day for the rest of their lives,” he continued. “If we could add or substitute a vaccine that would need to be given just every few months, I think we could achieve better control of high blood pressure.”
The vaccine targets angiotensin II, a molecule that constricts blood vessels and raises blood pressure. Angiotensin II is already the indirect target of several blood pressure medications. Angiotensin-converting enzyme (ACE) inhibitors reduce the production of angiotensin II in the blood by slowing its conversion from angiotensin I. Angiotensin receptor blockers (ARBs, such as candesartan and losartan) prevent angiotensin II from acting on these receptors, thus preventing constriction of the blood vessels.
During the study, 72 patients with mild-to-moderate high blood pressure were injected with the vaccine or a placebo. Patients who received injections at the beginning of the study, and again at four and 12 weeks reduced their systolic blood pressure (the top number) and their diastolic blood pressure (the bottom number) compared to those who did not get the vaccine.
Blood pressure changes were also evaluated at week 14.
Compared with patients who received a placebo, those who were injected with higher doses of the vaccine significantly reduced their daytime systolic blood pressure by 5.6 millimeters of mercury and their diastolic blood pressure 2.8 millimeters of mercury.
“Quite unexpectedly, our vaccine had the most striking effect early in the morning, the most dangerous time to have high blood pressure because it raises the risk of heart attack and stroke,” said senior study co-author Dr. Martin Bachmann, in a news release.
He added,“Antibodies produced by the vaccine seem to function like a sponge. The sponge empties out during the night when little angiotensin II is produced, so it is able to take up all the angiotensin II produced early in the morning.”
Another potential advantage of the vaccine over ACE inhibitors and ARBs is that these medications result in a large increase in renin, an enzyme that is thought to cause inflammation and is implicated in kidney failure. Vaccination induced only a low increase in renin, Bachmann said.
The next step in developing the vaccine is another small trial to determine whether a different injection regimen will create a larger antibody response and a greater reduction in blood pressure.
Nearly one in three American adults has high blood pressure, which increases the risk of stroke, heart disease, heart failure and kidney failure, the authors offered as background.
American Heart Association President Dr. Daniel Jones, said the research is encouraging.
“These investigators are pursuing novel approaches to hypertension control,” Jones said. “While too early to evaluate whether this may be clinically useful, it is encouraging to see promising research results.”