Could hypertension be treated with a vaccine?

A four-monthly vaccination could one day replace pills as the mainstay of hypertension treatment, according to media reports. By Emma Baines.

A clinical trial found that three injections of the vaccine reduced BP without causing serious side-effects. It could offer an alternative to daily pills for hypertension treatment, making it easier for many patients to keep their BP under control.

The vaccine, which is still in the research stage, is expected to be available within five years.

What is the research?
Reports were based on results of a phase IIa trial to test the safety and efficacy of CYT006-AngQb - a vaccine designed to induce the formation of antibodies against angiotensin II.

The study included 72 patients with mild to moderate hypertension. Over 12 weeks they were given three injections of 100 or 300 micrograms of the vaccine, or placebo.

Ambulatory BP was monitored before the treatment and again at 14 weeks. Side-effects were mostly mild and transient and included reactions at the injection site and mild influenza-like symptoms.

No difference was found between the treatment groups and placebo in BP measured in-office. But ambulatory monitoring 14 weeks after initial treatment found that BP was 9/4mmHg lower in patients given 300 micrograms of vaccine than in those given placebo.

What do the researchers say?
Dr Martin Bachmann, chief scientific officer of Cytos Biotechnology, the Swiss company developing the vaccine, said: 'The publication of this study is the result of basic and applied research that aims at employing our own immune system to protect us not only from infectious diseases, which is the traditional field for vaccines, but also from common chronic diseases like hypertension.'

What do other experts say?
Former president of the British Hypertension Society (BHS) Professor Morris Brown said that the idea of vaccinating against components of the renin-angiotensin system has been around for many years.

Although early reports from the Cytos trial had been exciting, on closer look the data were disappointing, he said.

'The biggest difference in BP was seen between the two placebo groups, and I doubt the fall at the top dose of the vaccine would have been significant without this variation in placebo response,' he explained.

The apparent diurnal effect of the vaccine did not make kinetic sense, he added. 'The antibody titre will not fluctuate during the day, and a vaccine would be expected to show even less diurnal variation than an ACE inhibitor or angiotensin-receptor blockers.'

Professor Bryan Williams, of the BHS Guideline Group, said: 'I cannot see the merits of this approach. We already have safe, tried and tested drugs to inhibit the renin-angiotensin system.'

He added that there were safety concerns that the vaccine could potentially lead to auto-immune complex disease in some patients.

'And what happens if the patient becomes dehydrated and needs the action of angiotensin to support their circulation and to prevent acute renal failure? It is difficult to reverse a vaccination,' he said.

He also pointed out that most patients need more than one treatment to control BP, and would still need drug therapy.

GPletters@haymarket.com

Lancet 2008; 371: 821-27

Informing patients

  • A vaccine to lower BP has been shown to be safe and effective in a small study.
  • For people with mild hypertension, vaccination a few times a year might be sufficient treatment.
  • More research needs to be done before the vaccine is available to patients.
  • Most patients with hypertension would have to continue taking pills, even if they were vaccinated.
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