Incyte announced updated clinical data from two Phase 1 studies evaluating INCA033989, a first-in-class mutant calreticulin (mutCALR)-targeted monoclonal antibody, in patients with myeloproliferative neoplasms. The findings, presented at the European Hematology Association (EHA) 2026 Congress, demonstrated rapid, clinically meaningful responses and consistent molecular activity across both myelofibrosis (MF) and essential thrombocythemia (ET). The data supports the potential for disease modification, with the company planning to initiate a pivotal ET study by mid-2026.

Results in Myelofibrosis

INCA033989 delivered broad clinical improvements in spleen volume, symptom burden, and anemia for MF patients. As a monotherapy and in combination with ruxolitinib, the therapy showed a manageable safety profile with no dose-limiting toxicities observed.

Molecular responses were consistent, with 89% of patients achieving a reduction in whole blood mutCALR variant allele frequency (VAF). Translational data indicated activity at the level of disease-initiating cells, with reductions in mutCALR-positive hematopoietic stem and progenitor cells.

Results in Essential Thrombocythemia

In patients with ET, INCA033989 demonstrated rapid and durable hematologic responses. Across doses, 87% of patients achieved a complete or partial hematologic response, including 70% who achieved a complete hematologic response. The median time to onset of durable complete hematologic response was 2.1 weeks.

Molecular responses correlated with clinical outcomes, with 73% of patients achieving a ≥25% reduction in VAF among those who achieved a complete hematologic response. The therapy was well tolerated, with 95% of patients remaining on treatment and a low incidence of Grade ≥3 adverse events (19%).

Regulatory Status and Next Steps

INCA033989 received Breakthrough Therapy designation from the U.S. Food and Drug Administration (FDA) in November 2025 for the treatment of ET patients harboring a Type 1 CALR mutation who are resistant or intolerant to prior cytoreductive therapy. Incyte remains on track to initiate a pivotal Phase 3 study (EXCALIBUR-ET2) in mid-2026 and is actively engaging regulators on a pivotal MF program.

Incyte Corporation agreed to acquire Vega Therapeutics, a wholly owned subsidiary of Star Therapeutics, in a deal valued at $1.25 billion upfront to expand its hematology portfolio. The transaction includes the late-stage candidate VGA039, a novel monoclonal antibody designed to treat bleeding disorders, with the total deal value potentially reaching $2 billion if specific sales milestones are achieved. This acquisition positions Incyte to address von Willebrand disease (VWD), the most common inherited bleeding disorder, with a therapy that offers a more convenient subcutaneous dosing option compared to existing intravenous infusions.

Deal Structure and Financial Terms

Under the agreement, Star Therapeutics is eligible to receive up to $750 million in additional milestone payments tied to the future sales performance of VGA039. The financial structure underscores the strategic importance of the asset to Incyte's long-term growth plans. The following table outlines the key financial components of the transaction:

VGA039 Clinical Profile and Market Potential

VGA039 is currently in Phase 3 pivotal development for patients with von Willebrand disease. The therapy functions by modulating Protein S to improve hemostasis, helping the body better control bleeding. It has the potential to become the first subcutaneous prophylactic treatment for VWD patients. Approximately 135,000 people in the U.S. have been diagnosed with VWD, a disorder characterized by excessive bleeding that can significantly affect quality of life.

Regulatory Designations and Ongoing Trials

The U.S. Food and Drug Administration has granted VGA039 Breakthrough Therapy, Fast Track, orphan drug, and rare pediatric disease designations. These regulatory supports aim to expedite the development and review of the drug. The candidate has advanced into the Phase 3 VIVID-6 study, a global single-arm crossover trial evaluating the safety and efficacy of subcutaneous VGA039 as a prophylactic treatment for bleeding in patients across all forms of the disease.

Strategic Fit and Analyst Outlook

Bill Meury, CEO of Incyte, stated that VGA039 aligns with the company's strategy of building a long-term growth business. He described the asset as a first-in-class Phase 3 program with encouraging early data and a manageable development pathway. Analyst firm William Blair noted that the deal fits well into Incyte's current hematology franchise and offers a relatively de-risked Phase 3 asset with blockbuster commercial potential in the 2030s. Analyst Matt Phipps highlighted that even with conservative assumptions, VGA039 has a clear path to a more than $1 billion market opportunity.