Abcuro Presents Interim Phase 1 Data Evaluating Ulviprubart in Patients with T Cell Large Granular Lymphocytic Leukemia at the 67th American Society of Hematology Annual Meeting

NEWTON, Mass.--(BUSINESS WIRE)--Abcuro, Inc., a late-stage clinical biotechnology company developing potentially first-in-class immunotherapies designed to benefit people living with debilitating and progressive rare autoimmune diseases and for other indications where certain cytotoxic T cells are pathogenic, today presented interim data from the ongoing Phase 1/2 clinical trial evaluating ulviprubart (ABC008) in patients with T cell large granular lymphocytic leukemia (T-LGLL) with anemia and/or neutropenia, in an oral presentation at the 67^th American Society of Hematology (ASH) Annual Meeting and Exposition, taking place December 6-9, 2025 in Orlando, Florida.

Ulviprubart is a potentially first-in-class, potent, monoclonal antibody targeting KLRG1, a novel mechanism of action to drive selective depletion of highly differentiated T cells and modify disease progression. Ulviprubart was designed to target KLRG1-expressing T cells while sparing B and regulatory T cells that are required to maintain normal immune system homeostasis.

“The data presented at ASH continue to support the potential of ulviprubart to selectively target and deplete highly differentiated T cells that drive debilitating diseases like T-LGLL. At the interim analysis, ulviprubart had an acceptable safety profile and was generally well tolerated across ascending doses, further supporting ulviprubart’s potential in treating patients with T-LGLL,” said H. Jeffrey Wilkins, MD, Chief Medical Officer of Abcuro.

T-LGLL is a hematological cancer driven by pathogenic expansion of immune cells that are frequently KLRG1+, resulting in neutropenia and anemia. Neutropenia can lead to frequent infections, a major cause of premature death in patients with T-LGLL, while anemia results in transfusion dependence in approximately one-third of patients.

Key Highlights from Oral Presentation:

The Phase 1/2 clinical trial (NCT05532722) is an open label, ascending dose study of ulviprubart patients with T-LGLL. The primary objective is to evaluate safety and tolerability. Secondary objectives include evaluating initial efficacy and pharmacokinetic/pharmacodynamic (PK/PD) profile of ulviprubart.

As of the data cut-off date of November 15, 2025:

• 21 patients were enrolled and evaluable for safety. 95% (n=20) of patients had neutropenia and 57% (n=12) of patients had anemia at baseline.
• 62% (n=13) of patients achieved >12 weeks of Q4W dosing on ulviprubart.
  • Among evaluable patients, seven experienced sustained depletions of >50% of CD8⁺ CD57⁺ KLRG1⁺ T cells at two or more consecutive visits. Three patients experienced sustained depletions of >90% of both CD8⁺ CD57⁺ KLRG1⁺ T cells and the CD8⁺ CD57⁺ parent population.
  • Among evaluable patients, all had neutropenia and nine patients had anemia at baseline.
    • With treatment, seven patients had a neutropenia response, defined as an absolute neutrophil count (ANC) increase of ≥50% from baseline for ≥4 weeks or ANC levels ≥1000 cells/µL for ≥4 weeks.
    • With treatment, two patients had an anemia response, defined as hemoglobin increased ≥1 g/dL for ≥4 weeks and not attributable to transfusion or growth factor.

Overall, ulviprubart was well tolerated at increasing doses and had an acceptable safety profile. Most treatment-related treatment-emergent adverse events (TEAE) were mild or moderate in severity. One patient experienced a Grade 3 infusion-related reaction, the only serious treatment-related TEAE observed on therapy.

About Ulviprubart
Ulviprubart (ABC008) is potentially a first-in-class, potent, monoclonal antibody targeting KLRG1, a novel proposed mechanism of action to drive selective depletion of highly differentiated T cells and modify disease progression. KLRG1 is a cell surface receptor predominantly expressed on highly differentiated T cells, while moderately or minimally expressed on other immune cells. Ulviprubart was designed to selectively deplete KLRG1-expressing T cells while sparing B and regulatory T cells that are required to maintain normal immune system homeostasis.

About Abcuro
Abcuro is a late-stage clinical biotechnology company developing potentially first-in-class immunotherapies designed to benefit people living with debilitating and progressive rare autoimmune diseases and for other indications where certain cytotoxic T cells are pathogenic. Our product candidate, ulviprubart (formerly referred to as ABC008), is a humanized monoclonal antibody that targets pathogenic T cells that express killer cell lectin-like receptor G1 (“KLRG1”), referred to as KLRG1+ T cells. Ulviprubart is designed to selectively target and deplete well-differentiated cytotoxic KLRG1+ T cells where KLRG1 is highly expressed, while sparing other immune cells, which we believe will offer improvements in safety and tolerability as compared to other T cell depleting approaches. Ulviprubart is currently being evaluated in a registrational Phase 2/3 clinical trial in people with inclusion body myositis (IBM), and a Phase 1/2 clinical trial in people with T cell large granular lymphocytic leukemia (T-LGLL).

For more information, visit us on LinkedIn and at abcuro.com.

Matthew DeYoung
Investor Relations and Media
Argot Partners
abcuro@argotpartners.com