(Bloomberg) -- A boutique investment bank known to few outside of health-care circles notched a huge win on Pfizer Inc.’s $43 billion plan to buy cancer-drug maker Seagen Inc. 

New York-based MTS Health Partners provided financial advice to Seagen alongside boutique investment bank Centerview Partners, according to a statement Monday. 

It’s the biggest deal ever for MTS and vaults it into the realm of firms trusted to advise on coveted health-care mega-deals. Andrew Weisenfeld, a managing partner, led the deal for MTS, keying off of a multi-decade relationship with Seagen, said people familiar with the matter, asking not to be identified because that information was private.

MTS was founded in 1999 by Curtis Lane, who had run the health-care investment banking group at Bear Stearns, according to the firm’s website. MTS provides strategic and financial advice to companies in the health-care industry and employs more than 60 people. Until Monday, it had advised on capital markets and M&A transactions worth $78 billion, it said.

The firm advised on dozens of transactions last year, representing companies such as Zymeworks Inc. and Theravance Biopharma, according to its website.

Its biggest role prior to Monday involved advising Apollo-backed RCCH HealthCare Partners on its 2018 purchase of LifePoint Health for about $5.6 billion, according to data compiled by Bloomberg.

This year, it advised Concert Pharmaceuticals on its $576 million sale to Sun Pharmaceutical Industries Ltd., according to a statement.

(Updates with other deals in fifth paragraph. The value of the Concert Pharmaceuticals transaction was corrected in an earlier version of this story.)

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