Listen to this article

Bridgewater-based Cosette Pharmaceuticals announced Feb. 20 it entered into an agreement to acquire Mayne Pharma Group Ltd. in a $430 million deal.

Mayne is an Australian-headquartered specialty pharmaceutical company focused on commercializing new novel pharmaceuticals.

Cosette says the transaction will strengthen its dermatology and women’s health business; expand commercial and operational capabilities; and add multiple sustainable and growing patent-protected products to its portfolio.

“This acquisition marks a transformational step for Cosette, adding patented, high-growth products to solidify our leadership in women’s health in the U.S. and expanding our reach globally,” said Apurva Saraf, president and CEO, Cosette Pharma. “By combining Cosette’s strong portfolio with Mayne Pharma’s proven commercial expertise, the combined company will be well positioned to further invest in innovation, portfolio expansion, and better serve our patients.”

“Joining the Cosette team amplifies our shared mission to improve lives through innovative and accessible women’s health and dermatology medicines,” said Mayne Pharma CEO Shawn Patrick O’Brien. “This transaction represents a unique opportunity for our employees, customers, and patients. Together, we will extend the reach of important therapies, drive innovation, and improve patient access.”

Key details of the deal include:

• Received approval from the board of directors of both companies. Additionally, Mayne Pharma’s board unanimously recommended its shareholders vote in favor of of the deal.
• Cosette will acquire all shares of Mayne Pharma
• Transaction expects to close in the second quarter of 2025
• Combined company will operate as a privately held upon entity completion of the transaction

Cosette’s advisors include Santander US Capital Markets LLC and UBS Investment Bank as financial advisors; and Ropes & Gray LLP and Corrs Chambers Westgarth as legal advisors.

Jeffries Australia serves as financial adviser to Mayne Pharma and Gilbert + Tobin and Arnold & Porter as legal advisors.

“We look forward to a timely closing and welcoming Mayne Pharma to the Cosette family,” said Saraf.

Editor’s note: This headline was updated at 7:48 a.m. Dec. 15, 2025, to clarify that the deal was not final.