Keros Therapeutics earns $20m milestone as elritercept Phase 3 enrols
Keros Therapeutics has triggered a $20 million development milestone payment from its licensing partner Takeda, following first-patient dosing in the ELRiSE MDS Phase 3 trial of elritercept. The Lexington, Massachusetts-based company said it will distribute 25% of the net cash proceeds to stockholders once the payment is received.
ELRiSE MDS is a randomised, open-label, multicentre study comparing elritercept against epoetin alfa in patients with very low, low, or intermediate risk myelodysplastic syndromes (MDS) who have anaemia. The trial represents the most advanced clinical test yet for elritercept, which Keros describes as an engineered ligand trap: a modified binding domain of activin receptor type IIA fused to an antibody Fc region. The construct is designed to intercept dysregulated signalling within the transforming growth factor-beta (TGF-beta) pathway, a mechanism implicated in the suppression of blood cell production.
The Takeda deal
The ELRiSE milestone falls under a global licence agreement that became effective in January 2025, under which Takeda holds commercialisation rights to elritercept worldwide outside mainland China, Hong Kong and Macau. Keros received a $200 million upfront payment in February 2025 and retains eligibility for development, commercial and sales milestones with potential aggregate value exceeding $1.1 billion, together with tiered royalties on net sales.
Jasbir S. Seehra, president and chief executive of Keros, pointed to encouraging signals from the earlier Phase 2 study: "We are encouraged by the positive signals that were observed in the Phase 2 clinical trial of elritercept in patients with very low-, low-, or intermediate-risk MDS, which were observed in patients with MDS both with and without ring sideroblasts."
Market and competitive context
The MDS anaemia space is a well-established target for novel erythropoiesis-stimulating agents and related biologics. Luspatercept, a closely related activin receptor ligand trap developed by Bristol Myers Squibb and Merck, is already approved for transfusion-dependent anaemia in lower-risk MDS in the United States and Europe, positioning elritercept as a direct competitor in a validated commercial market. Epoetin alfa, the active comparator chosen for ELRiSE, remains the standard of care in many centres despite limited evidence in lower-risk MDS, making it a reasonable but arguably low bar against which to benchmark a newer agent.
The wider TGF-beta ligand trap class has attracted sustained investor and partner interest over the past several years, in part because the signalling family affects multiple tissues. Keros is also advancing rinvatercept in Duchenne muscular dystrophy and amyotrophic lateral sclerosis, providing the company with a pipeline that could broaden its exposure beyond haematology. The elritercept programme's Phase 3 enrolment milestone, coming roughly 18 months after deal close, suggests the Takeda partnership is progressing to plan.
For investors, the next meaningful readout will be interim or topline data from ELRiSE MDS, which will need to demonstrate superiority or non-inferiority to epoetin alfa on haematological response endpoints to support a regulatory filing. The scale of the potential milestone stream, if commercial thresholds are met, means elritercept's Phase 3 trajectory will remain central to Keros's valuation story.