April 25--Some of the biggest medical-device companies in the world are convinced that burning away nerves leading to the kidneys can cut dangerously high blood pressure in ways prescription drugs can't.
Renal denervation is a therapy many years in the making. Billions in profits may stand to be made, and tens of thousands of patients wait to get a minimally invasive treatment to address a major underlying cause of deadly stroke and heart failure. All three major device companies in Minnesota have devices in the works.
Now, the companies just need the scientific evidence that the therapy actually works.
Seventy million Americans have high blood pressure, but the subset who have severe hypertension that doesn't drop with drug therapy or lifestyle changes is not well-defined. Some doctors are skeptical that denervating renal arteries will make a meaningful dent in the patient population. But physicians nevertheless welcomed the news that the quest for a new hypertension therapy passed a milestone this month, with Boston Scientific Corp. enrolling its first patient in a randomized trial of its Vessix system.
The company's peripheral interventions unit in Maple Grove aims to produce the United States' first data from a randomized, blinded trial since last spring. That was when a similar study by Medtronic failed to prove the benefits of the therapy, which had shown so much promise in less-rigorous testing that it drove corporate acquisitions before the Food and Drug Administration greenlighted commercial sales.
"At least 20 companies worldwide and in the United States were pursing this, and they all pulled back after the randomized trial failed," said Dr. Randy Zusman, a Harvard associate professor and director of the hypertension division at Massachusetts General Hospital in Boston. "They saw it as a terrible defeat, and stopped all of their in-progress trials and planning for trials and really retrenched."
In the year since, Ireland-based Medtronic and Massachusetts-based Boston Scientific -- both of which employ several thousand Minnesotans -- say they've done extensive consulting with the clinical and regulatory community and have recently received permission from the FDA to start new controlled, blinded clinical trials.
"We've just seen this work. So we believe it, and now we just have to find the right way to prove it," Jeff Mirviss, president of Boston Scientific's peripheral intervention division, said in an interview. Enrolling the first patient "was an important milestone just to put a stake in the ground, that renal denervation is back."
Boston Scientific quietly got approval to start its new Vessix clinical trial last December and enrolled its first patient last week at a Birmingham, Ala., hospital. Medtronic got FDA approval for a new trial in March, and it plans to enroll patients in trials of its redesigned Symplicity Spyral device next month. Both companies already sell renal denervation devices commercially in Europe.
"We don't consider ourselves racing," Medtronic spokeswoman Wendy Dougherty said. "We are trying to do good science."
St. Jude Medical makes a renal denervation device called the EnligHTN system, which is also approved for sale in Europe. On Wednesday, executives at the Little Canada company declined to say whether they will launch a new U.S. trial.
The Centers for Disease Control and Prevention says about 70 million Americans have high blood pressure, and only half have it under control. People whose blood pressure is higher than 140/90 are often treated for serious cardiovascular problems.
Prescription drugs exist, but many patients end up taking a complex cocktail of hypertension medications and still fail to control it. Medical device makers say permanently searing nerves near the kidneys that help control the body's fight-or-flight response can lower blood pressure on more consistent long-term basis. Doctors say they're interested to see the results of more studies.
"The central treatment of hypertension will always continue to be healthy habits, more exercise, weight control," said Dr. Hassan Ibrahim, a University of Minnesota professor and director of the U Medical School's renal division. "I'm not sure renal denervation is going to improve the proportion (of patients with uncontrolled hypertension) by a huge percentage. I think it will be quite limited to people with severe hypertension who require a lot of medications. But we do not have definitive proof that this therapy worked in the manner it has been studied."
Medtronic's trial last year showed its therapy was safe -- just 1 percent of patients had major adverse health events -- but that it failed after six months to lower blood pressure better than in patients who were ramped up to maximum doses of medication. Patients in the study's randomized control group underwent "sham" procedures in which they thought they'd received the therapy, but didn't.
Since then, the device companies have come to think that the trial was flawed, because it was tough to generalize the experiences of patients on the maximum doses of drugs and doctors with varying levels of skill using a device with a single electrode.
Boston Scientific's device has four electrodes, and now Medtronic's does as well, to create a more uniform burn pattern and reduce variability in physician use. Just as important, the companies will now be testing patients who are taking no hypertension medication.
"What we are demonstrating potentially in this trial," Boston Scientific's Mirviss said, "is that it can lower blood pressure in the absence of medication. A wonderful vision would be, patients may have a choice to get a procedure like renal denervation that would obviate the need for medication or potentially allow them to take less medication."
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