Resistant blood pressure: New drug proves effective in phase 2 trials

Date:

  • Uncontrolled high blood pressure—or hypertension—affects millions of people worldwide, putting them at greater risk of serious health conditions.
  • Research on a new drug called Baxdrostat has shown that it can substantially reduce blood pressure in people with treatment-resistant hypertension.
  • The results of the phase 2 trial support the idea that some cases of treatment-resistant hypertension may be caused by the hormone aldosterone.

Blood pressure is a simple measure of the blood pushing against the walls of the arteries. It consists of two numbers — one which represents the systolic pressure when the heart beats and the other of the diastolic pressure between heartbeats.

Healthy blood pressure is up to 120 mmHg systolic and 80 mmHg diastolic. Anything consistently above 130 mmHg and 80 mmHg is considered high or hypertensive according to the U.S. 2017 clinical practice guidelines.

The increased pressure doesn’t only affect blood vessels, it also puts the heart, brain, kidneys, and eyes under greater strain. In the long term, persistent high blood pressure is linked to an increased risk of life threatening health conditions such as stroke and heart disease, two of the leading causes of death in the United States.

New research from CinCor Pharma, Brigham and Women’s Hospital, Harvard Medical School, and the Queen Mary University of London may offer hope to people living with uncontrolled high blood pressure.

The study, published in The New England Journal of Medicineand presented at the American Heart Association Scientific conference, shows a new drug called Baxdrostat can significantly reduce blood pressure for people whom current treatments haven’t worked.

Hypertension has no symptoms or warning signs, and the only way to know blood pressure levels is to have them tested regularly. Risk factors for high blood pressure include “genetic, age-related, dietary and lifestyle factors,” said Dr. Rigved Tadwalkar, a board certified cardiologist at Providence Saint John’s Health Center, California.

The Centers for Disease Control and Prevention estimates that tens of millions of people in America have hypertension. Of these an estimated 12% have treatment-resistant hypertension (tRH), equating to around 7.6 million people.

“Hypertension can be a challenging condition to treat,” Professor Nilesh Samani, medical director at the British Heart Foundation, told Medical News Today.

Resistant hypertension, on the other hand, is classified as having high blood pressure that persists despite using at . This can substantially increase the patient’s risk of cardiovascular disease and renal failure.

Speaking to MNT, Dr. Tadwalkar, who was not involved in the study, explained that tRH is commonplace in clinics.

“Approximately 10% of all individuals with hypertension have resistant hypertension. As a result, it is seen frequently in the clinical setting, by cardiologists and primary care physicians alike,” he said.

Dr. Tadwalkar said the evaluation and treatment of tRH are different from standard hypertension as it is considered “clinically […] to be in a separate category”.

Its causes are beyond the usual risk factors associated with standard hypertension. When investigating tRH, clinicians consider “predisposing medical conditions, contributory medications, and secondary causes of hypertension.”

To understand if the drug reduced blood pressure, the researchers conducted a multi-centered phase 2 clinical trial BrigHTN.

Between July 2020 and June 2022, the researchers gave a total of 248 people who had tRH with an average blood pressure of 130/80 mmHg a daily dose of either 2mg, 1mg, or 0.5mg of Baxdrostat or a control placebo for 12 weeks.

Participants taking a mineralocorticoid receptor antagonist or a potassium-sparing diuretic were required to discontinue these agents for a total of 4 weeks before randomization if they could do so safely. All participants entered into randomization took the new drug in combination with their current blood pressure medication.

People with kidney disease and uncontrolled diabetes were excluded from the trial.

The researchers checked in with the participants in the clinic at set time points with a follow-up call a week after the final dose. They took participants’ blood pressure measurements alongside the levels of Baxdrostat they were taking, and their aldosterone and cortisol levels in the blood and urine. The researchers also gave participants electrocardiograms and physical examinations.

The researchers noted a drop in blood pressure with treatment. The highest 2mg dose of Baxdrostat showed more than a 20-point reduction in systolic blood pressure, an 11-point drop when compared to the placebo control group.

Interestingly, halving the dose to 1mg also reduced blood pressure by over 8 points when compared to the placebo.

120 participants reported 232 adverse events during the study. There were high levels of side effects reported in the control group (41%), but most were mild. There were no reported deaths and no instances of adrenocortical insufficiency, but a few patients had recurrent high potassium levels which were managed by temporary cessation of the drug and routine dietary advice.

Baxdrostat stops the body from making aldosterone, which has been linked to tRH. Too much aldosterone increases the amount of salt and water reabsorbed from the kidney increasing the volume of blood and blood pressure.

Study author Dr. Morris J Brown, professor of endocrine hypertension at Queen Mary University, London explained to MNT the underlying hypothesis:

“The reason why patients are resistant to multiple conventional drugs is that in this set of patients, there is a specific cause of hypertension, namely the hormone aldosterone.”

Dr. Brown said he felt this was one of the “most exciting parts of the study especially as this is not targetted by conventional drugs.”

But could suppressing aldosterone lead to health problems in the longer term? Dr. Brown said there would be no harm.

“In most people, physiological levels of aldosterone are already suppressed by the excess amount of salt in the diet. In people with resistant hypertension, the aldosterone is coming from microscopic clusters of cells in the adrenal gland where specific mutations have led to aldosterone production going into ‘automode’—the hormone is churned out continuously, regardless of the body’s needs.”
— Dr. Morris J Brown

The researchers showed a dose-related reduction in blood pressure and aldosterone secretion.

They concluded that Baxdrostat inhibits aldosterone synthase, a key enzyme in the production of aldosterone which leads to the reduction in blood pressure in participants with treatment-resistant hypertension.

Dr. Tadwalkar believes a drug like Baxdrostat offers a potential new treatment option for people with resistant hypertension.

“[A] drug like Baxdrostat is of potential high value in preventing the onset of these [cardiovascular disease, stroke, heart attack, and heart failure] diseases,” he said.

“We finally have a drug that targets the synthesis of a hormone [aldosterone] that we feel is primarily implicated in the pathogenesis of resistant hypertension, and this is a huge step forward.”
— Dr. Rigved Tadwalkar

The research was also welcomed by Prof. Samani, who was not involved in the current study, who said:

“This new type of drug which seems to be safe and effective in lowering blood pressure in some patients with elevated blood pressure despite taking other anti-hypertensive drugs is welcome.”

However, he cautioned that “[m]ore studies are needed to show their long-term benefits.”

It is important to note the trial population was predominantly white (70%) so, the results may not translate to the wider population.

“The limitations of this trial are primarily related to it being a phase 2 study. […], the enrolled population is typically smaller, and the length of time individuals are followed for can be shorter” echoed Dr. Tadwalker, also highlighting that phase 2 trials do not test the drug against current treatments which would be an important next step.

“At some point down the line, it will also be helpful to see how this drug fares in other patient populations, including those with standard hypertension,” he said.

The next immediate step for the research is the results from a second phase II trial called HALO, which will study “[p]atients whose hypertension was uncontrolled on one or two drugs, but not meeting the definition of resistant (HALO patients were not on a diuretic, whilst 100% of BRIGHTN patients were),” said Dr. Brown.

“We need phase 3 [trials]. This will start next year. Realistically we are probably looking at 2025 as the earliest date for the clinic. An interesting question, however, is whether regulators would accept a much smaller program for a separate indication, namely patients with primary aldosteronism,” he added.

Read the full article here

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