Boundless Bio and Serapha Bio have announced a definitive merger, creating a new entity focused on genetic medicine. The combined company, to be named Serapha Bio, will advance a therapy for Alpha-1 Antitrypsin Deficiency (AATD). This transaction is supported by a concurrent $230 million private placement, signaling strong investor confidence in the new venture.
A Strategic Merger and Substantial Financing
Under the all-stock deal, the new company will operate as Serapha Bio and is expected to trade on Nasdaq under the ticker “AATD”. The merger is bolstered by a significant financing round co-led by healthcare investors RTW Investments and RA Capital Management. This move provides Serapha with a public market platform to accelerate its clinical development plans.
The $230 million private placement includes $138 million already secured, with an additional $92 million to close with the merger. This capital infusion is projected to fund operations into the second half of 2029. The financial runway will support the lead candidate, SERP-01, through Phase 2 completion and the initiation of Phase 3 trials.
Advancing a Novel Gene Editing Therapy
The company will focus on developing treatments for Alpha-1 Antitrypsin Deficiency, a hereditary disorder affecting thousands of Americans. The condition is caused by a point mutation that leads to the production of a misfolded, toxic protein. This results in severe liver damage and leaves the lungs vulnerable to progressive disease.
Serapha’s lead candidate, SERP-01, is an investigational in vivo base editing therapy designed to correct the underlying genetic cause. By targeting the SERPINA1 mutation, it aims to restore the production of the normal, functional protein. This dual action could potentially address both the liver and lung manifestations of AATD with a single dose.
SERP-01 was licensed from YolTech Therapeutics, where it was developed as YOLT-202 in Greater China. Early proof-of-concept data from a trial in China has demonstrated the restoration of serum AAT to normal levels. This promising clinical profile has given investors confidence that it could become a best-in-class therapy.
Transaction Rationale and Shareholder Value
For Boundless Bio, this merger represents a strategic pivot following a review of its own clinical pipeline. The company determined that early data for its oncology program did not support continued advancement. This transaction is therefore positioned as an opportunity to deliver meaningful value to its existing stakeholders.
The agreement stipulates that upon closing, pre-merger Serapha stockholders will own approximately 96.3% of the combined company. Boundless Bio stockholders will hold the remaining 3.7% and receive a cash dividend of approximately $44 to $48 million. This structure provides a return for current investors while capitalizing the new entity.
The transaction has received unanimous approval from the boards of both companies and is now subject to customary closing conditions. These include approvals from stockholders and relevant regulatory bodies. The merger is anticipated to be finalized in the fourth quarter of 2026.
This merger and financing position the new Serapha Bio as a key player in the genetic medicine space. The transaction provides the capital and public platform to advance SERP-01, a potentially transformative therapy for AATD patients. With a clear clinical path and strong investor backing, the company is poised to address a significant unmet medical need.