Boston’s Watchman approved in the US for warfarin refuseniks


Third time lucky. Boston Scientific has finally gained premarket approval for its Watchman device, designed to prevent stroke in atrial fibrillation patients, seven years after the first attempt. Despite the delay, no rival devices are expected to appear in the US for around three years.

But pharmacological anticoagulant therapy remains the first choice for these patients. Boston had sought Watchman’s approval as an alternative to long-term warfarin, but the FDA, perhaps mindful of the exceptionally tight recent panel vote, only greenlit it for second-line use. Still, following the device’s chequered regulatory history – plus a rather embarrassing embargo breach at ACC two years ago – Boston should be glad to finally get approval. The company's shares jumped 4% in early trading. 

Thicker than water

The parachute-shaped implant is used to block off a pouch in the heart called the left atrial appendage in which blood can pool and form clots, thus abrogating the risk of stroke in patients with non-valvular atrial fibrillation. Results from its pivotal trial, Prevail, were not encouraging, with Watchman failing to demonstrate a concrete efficacy advantage over warfarin and actually being inferior to the drug on ischaemic stroke (Event – Watchman data get worse as third panel approaches, September 22, 2014).

Thus the FDA has approved the device for use in high-risk patients who are suitable for treatment with warfarin – all Watchman recipients must take warfarin for a short time – but who do not wish to take the drug long-term.

Boston said that these patients must have an “appropriate rationale” for opting for the device, but did not suggest what the rationale might be, though it is likely to cover patients with a history of, or at increased risk of, bleeding. The company did say that “up to 40%” of patients who are eligible for oral anticoagulation did not take it, and pointed out that warfarin therapy required patients to submit to dietary restrictions and regular monitoring.

However, warfarin is not the only blood thinner on the market. Since Watchman began its regulatory journey with its initial FDA submission by its originator, Atritech, in 2008, several new anticoagulants have appeared, with Bristol-Myers Squibb’s Eliquis in particular demonstrating a better bleeding profile than warfarin. These drugs might be more appealing to warfarin refuseniks than Watchman, though cost will weigh here – the newer drugs are much more expensive than the generic – meaning that payers could inadvertently bolster Boston’s case.

Go Set a Watchman

At least on the device side Watchman has no competition. And that will not change for three years, according to Larry Biegelsen of Wells Fargo.

The analyst wrote in a note on March 6 that competitors such as St. Jude and Coherex Medical had been waiting for the Watchman approval before starting pivotal US trials of their devices, though St Jude said two years ago that it had started an approval trial of the Amplatzer Cardiac Plug.

Mr Biegelsen said that approval as the second choice after warfarin was expected, certainly since the panel vote last October. He put US Watchman sales at $20m this year, increasing to $150m in 2019. EvaluateMedTech’s consensus forecasts put worldwide sales at $341m in 2020.

Boston said the Watchman launch would be cautious, initially making the product available at clinical trial sites, with more doctors being gradually trained in the coming years. It is to be hoped that enough patients who dislike warfarin emerge to allow the physicians to learn.

To contact the writer of this story email Elizabeth Cairns in London at or follow @LizEPVantage on Twitter

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