Bristol-Myers Squibb has named Susan Sweeney, who has been with the firm since 1995, its new head of U.S. commercial.

The new position involves helming commercialization efforts for its largest market. In Q2 this year, the company’s U.S. sales exceeded $3.2 billion, which is about 60% of its business worldwide, Sweeney said.

She faces a big test, as the firm jockeys for dominance atop two high-profile categories, immunotherapies and oral anticoagulants.

“Anytime that you’re in the U.S. market, and very acutely in the U.S. right now, [the challenge is] uncertainty created in the access environment and how we adapt to that through our products,” Sweeney told MM&M. “We are steering that conversation to the value of the product and not just about the price, but the value equation of our medicines and our commitment to patients. It takes the whole company.”

She takes over the U.S. reins from Johanna Mercier, who was promoted to lead the large markets division at BMS, which includes the U.S., Germany, and Japan and makes up about 80% of sales. Sweeney also reports to Mercier.

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The U.S. market’s two key assets are PD-1 drug Opdivo, which reached more than $1.02 billion in U.S. sales in the second quarter, a 33% increase over the prior year’s Q2, and blood thinner Eliquis.

Opdivo has stiff competition from many large drugmakers in the I/O space, including Merck’s own PD-1 inhibitor, Keytruda, whose sales actually surpassed Opdivo’s in the second quarter. Some investors are skeptical that BMS can defend against Merck’s looming dominance in the NSCLC market. Other rivals to watch out for include Genentech and its PD-L1 antibody Tecentriq, and buzzy CAR-T therapies like Novartis’ Kymriah.

“The oncology marketplace is extremely competitive and the pace of innovation is high,” Sweeney acknowledged. “If you look at our track record of what we’ve been able to do for Opdivo, we’re executing great marketing campaigns and have been able to find good position in [the] marketplace with that marriage of the sciences and understanding of where the science takes us.”

In the cardiovascular arena, Eliquis already leads the pack among next-gen clot busters and was even poised to overtake older med warfarin in sales, according to industry reports.

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Sweeney has worked at BMS for more than 20 years. She came up through the company’s marketing division, where she worked on antipsychotic Abilify, antibiotic Tequin, RA drug Orencia, blood thinner Plavix, and U.S. cardiovascular and diabetes drugs.

In 2012, she was named VP of the U.S. cardiovascular business unit and three years later was promoted to CEO operations lead. Most recently, Sweeney was SVP and head of worldwide commercialization. Her previous role has not yet been filled, Sweeney said.

In August, BMS  promoted Christopher Boerner to EVP and chief commercial officer. Boerner replaced Murdo Gordon, who left the company in early August to join Amgen as EVP of global commercial operations.