Esperion Therapeutics (NASDAQ: ESPR) has agreed to acquire Corstasis Therapeutics, a privately held commercial-stage biopharmaceutical company, in a deal valued at up to USD 255 million. The transaction includes USD 75 million upfront, up to USD 180 million in regulatory and commercial milestones, and low double-digit royalties on global sales.
The acquisition gives Esperion full ownership of Enbumyst (bumetanide nasal spray), an FDA-approved therapy for edema associated with congestive heart failure, hepatic disease, and renal disease, including nephrotic syndrome, in adults. Approved in September 2025, the product represents the first intranasal loop diuretic designed for outpatient use. The transaction is expected to close in Q2 2026, subject to customary conditions.
Esperion will finance the acquisition through existing credit facilities and a monetization of its Japanese royalty streams arranged with Athyrium Capital Management and HealthCare Royalty (HCRx). The structure avoids issuing new equity.
Intranasal delivery for outpatient decongestion
Enbumyst reformulates bumetanide, a well-known loop diuretic that inhibits the Na⁺-K⁺-2Cl⁻ cotransporter (NKCC2) in the kidney, into a nasal spray. Bumetanide has historically been administered orally or intravenously, but both routes have limitations in heart failure patients experiencing fluid overload.
Oral diuretics often show variable absorption in patients with gut edema, while intravenous administration requires clinical supervision and typically occurs in hospitals or infusion centers. By contrast, the intranasal formulation delivers bumetanide through the nasal mucosa into systemic circulation, potentially providing more consistent absorption while enabling self-administration outside the hospital.
The product was approved through the 505(b)(2) regulatory pathway, which allows reformulations of previously approved drugs while referencing existing safety and efficacy data. Corstasis is also developing additional delivery approaches for loop diuretics, including a subcutaneous multidose pen injector, which could extend outpatient treatment options for fluid overload.
Competitive landscape
The most direct competitor to Enbumyst is FUROSCIX, a subcutaneous formulation of furosemide developed by scPharmaceuticals and approved by the FDA in 2022 for outpatient heart failure decongestion. Both products aim to enable reliable diuretic therapy outside the hospital, though they differ in delivery method: intranasal spray versus subcutaneous infusion.
Other therapies used in fluid management include vasopressin antagonists such as tolvaptan (Samsca) and disease-modifying drugs for heart failure such as SGLT2 inhibitors, including AstraZeneca’s dapagliflozin and Boehringer Ingelheim/Eli Lilly’s empagliflozin. These agents address broader heart failure management but are not designed specifically for rapid outpatient decongestion.