Independent Study Demonstrates Stroke Patients Experience Superior Outcomes with Intra-Arterial Treatment vs. Tissue Plasminogen Activator (tPA)

Comparative Effectiveness Results from MR CLEAN Trial published in New England Journal of Medicine May Redefine Stroke Treatment

Alameda, CA – December 17, 2014 – Penumbra, Inc., the market leader in intra-arterial stroke treatment, announced that an independent study published online today in the New England Journal of Medicine found that intra-arterial stroke treatment, including the company’s clot extraction technology, was shown to be significantly more effective than medical management with tissue plasminogen activator (tPA), which is the current standard of care. The findings of this randomized, controlled comparative effectiveness trial of stroke treatment have the potential to change the standard of care and improve functional independence for the 15 million stroke patients worldwide who currently have few treatment options.

Intra-arterial treatment, also called endovascular or interventional treatment, involves working inside the artery to remove the clot. In the MR CLEAN (Multicenter Randomized Clinical trial of Endovascular treatment for Acute ischemic stroke in the Netherlands) comparative effectiveness study, intra-arterial treatment improved the rate of good functional outcome by 71 percent over treatment with medical management with tPA alone. Of patients who received intra-arterial treatment, 32.6% achieved a clinically defined positive stroke outcome compared with 19.1% of those who received medical management. Intra-arterial treatment was beneficial for all ages (18+), including the elderly (80+) – a population for whom intervention was previously thought to be risky. The trial began enrolling in 2010 and participating physicians used earlier generation intra-arterial technology. Currently available technology continues to improve upon the baseline set by MR CLEAN.

“Despite being the number one cause of long-term adult disability, stroke has been one of the most undertreated and devastating diseases in the world,” said Albert J. Yoo, M.D., director of Acute Stroke Intervention in the Division of Interventional Neuroradiology/Endovascular Neurosurgery at Massachusetts General Hospital, assistant professor at Harvard Medical School and study author of MR CLEAN. “Now that intra-arterial treatment has been proven to provide significant benefits for stroke patients of all ages, we have a golden opportunity to dramatically improve the lives of stroke victims and, at the same time, help reduce costs in our healthcare system by returning patients to functional independence.”

MR CLEAN also demonstrated:

  • Intra-arterial treatment was effective for patients with the most common and devastating form of stroke, LVO (large vessel occlusion), for which tPA is less effective.
  • Intra-arterial treatment is effective up to 6 hours after stroke onset vs. 3 to 4.5 hours for tPA.
  • Both treatments were safe, with no differences relating to hemorrhage or mortality.

“With the results of MR CLEAN, we have the needed evidence to support endovascular treatment in the fight against stroke, and the results are truly astounding,” said Michael J. Alexander, MD, FACS, Director of the Neurovascular Center, Professor of Neurosurgery at Cedars-Sinai and past president of the Society of NeuroInterventional Surgery. “They show that endovascular treatment can benefit a broad population of patients – not just younger patients as previously thought but older patients as well if treated early.”

“The MR CLEAN study results provide evidence to support intra-arterial treatment in the fight against stroke and have the potential to change the standard of care,” said Adam Elsesser, chief executive officer, director and founder, Penumbra. “Penumbra is proud to have supported the MR CLEAN trial, and these important results will aid our efforts to improve access to intra-arterial treatment for the millions of stroke patients around the world.”

Penumbra provided an unrestricted grant for the trial, and its devices were among those included in the protocol. Companies providing grants had no influence over the trial’s design or execution. Penumbra’s newest intra-arterial treatment, which was not available at the time MR CLEAN was conducted, is the ACE™, a next generation clot extraction system that uses aspiration alone to engage and remove blood clots causing an acute ischemic stroke. Results with the Penumbra ACE system continue to improve upon the baseline set by MR CLEAN.

About the MR CLEAN Study

MR CLEAN (Multicenter Randomized Clinical trial of Endovascular treatment for Acute ischemic stroke in the Netherlands) was a prospective, randomized clinical trial comparing intra-arterial treatment with medical management using tissue plasminogen activator (tPA). The study enrolled 500 patients, and unlike previous studies, MR CLEAN specified that large vessel occlusion (LVO) had to be confirmed by CT angiography (CTA). Once confirmed, all patients were first administered tPA if eligible; 233 were then assigned to the intra-arterial treatment arm and 267 to the control arm. All stroke centers in the Netherlands participated in the study, and the intervention and control groups were well balanced. Intra-arterial devices were used at the discretion of the treating physician to include stent retrievers, direct aspiration or combination therapy. Primary endpoint was measurement of blinded modified Rankin Scale (mRS) scores at 90 days. The modified Rankin Score (mRS) is the most widely used clinical outcome measure for stroke clinical trials; an mRS score of 2 or less is considered to be the threshold for positive stroke outcome.

About Penumbra

Penumbra, Inc. ( is a global interventional therapies company committed to delivering clinically beneficial products that help patients suffering from stroke and other vascular diseases. Penumbra’s global headquarters is located in Alameda, California with sales operations around the world.


Penumbra Media Relations:

Merryman Communications

Betsy Merryman


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1Berkhemer OA, Fransen PSS, Beumer D, et al. A randomized trial of intra-arterial treatment for acute ischemic stroke. NEJM online publication. December 17, 2014.


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