Ionis Pharmaceuticals and Ono Pharmaceutical have entered into a significant licensing agreement worth up to $940 million for sapablursen, an investigational RNA-targeted medicine for polycythemia vera (PV). The deal, announced on March 11, 2025, grants Ono exclusive global rights for the development and commercialization of the drug candidate.
Under the terms of the agreement, Ionis will receive an upfront payment of $280 million and is eligible for up to $660 million in additional milestone payments based on development, regulatory, and sales achievements. The California-based company will also earn royalties in the mid-teen percentage range on annual net sales of sapablursen.
Strategic Implications for Both Companies
Brett P. Monia, Ph.D., Chief Executive Officer of Ionis, emphasized the strategic importance of the deal: "We are pleased to entrust sapablursen to Ono, whose unique capabilities will help maximize its value by ensuring broad access for people living with PV."
For Ionis, the agreement provides financial flexibility while allowing the company to focus on its core portfolio. "Streamlining our Ionis-owned portfolio provides financial flexibility, supporting our commitment to invest in and focus on our near and mid-term commercial opportunities and generate substantial revenue growth," Monia added.
From Ono's perspective, the partnership strengthens its position in hematology. Toichi Takino, President and COO of Ono, stated: "This partnership aligns with our strategy to strengthen our pipeline in hematology. We expect sapablursen to become a new treatment option for PV patients worldwide."
Sapablursen's Mechanism and Clinical Status
Sapablursen represents an innovative approach to treating PV, a rare and potentially life-threatening blood disorder. The drug is designed to reduce the production of TMPRSS6, which results in increased expression of hepcidin—a key regulator of iron homeostasis. This mechanism has the potential to address the underlying pathophysiology of PV.
The drug candidate is currently being evaluated in the fully enrolled Phase 2 IMPRSSION study involving adult patients with PV. Notably, sapablursen received both Fast Track designation and orphan drug designation from the U.S. Food and Drug Administration (FDA) in 2024, highlighting its potential significance in addressing an unmet medical need.
According to the agreement, Ionis will complete the ongoing Phase 2 IMPRSSION study, after which Ono will assume responsibility for subsequent development, regulatory filings, and commercialization efforts globally.
Understanding Polycythemia Vera
Polycythemia vera is characterized by the overproduction of red blood cells, which significantly increases the risk of serious blood clots, particularly in critical organs such as the lungs, heart, and brain. Patients with PV also experience severe iron deficiency and commonly suffer from fatigue.
The condition represents a significant unmet medical need, as current treatment options are limited and often focus on symptom management rather than addressing the underlying disease mechanisms.
Regulatory Considerations
The transaction remains subject to the requirements of the Hart-Scott-Rodino Antitrust Improvements Act of 1976 (HSR Act), which requires companies to file premerger notifications with the Federal Trade Commission and the Department of Justice for certain acquisitions.
Company Backgrounds
Ionis Pharmaceuticals has established itself as a pioneer in RNA-targeted medicines over the past three decades. The company currently has six marketed medicines and a robust pipeline focused on neurology, cardiology, and other areas of high patient need.
Ono Pharmaceutical, headquartered in Osaka, Japan, is an R&D-oriented pharmaceutical company with a history dating back to 1717. The company focuses on oncology, immunology, neurology, and specialty research. In June 2024, Ono acquired Deciphera Pharmaceuticals to strengthen its drug pipeline and support global expansion efforts.
This collaboration represents a significant development in the treatment landscape for polycythemia vera, potentially offering new hope for patients suffering from this rare hematologic disease.
