On December 8, 2025 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, reported 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 67th American Society of Hematology (ASH) (Free ASH Whitepaper) Annual Meeting and Exposition, taking place December 6-9, 2025 in Orlando, Florida.

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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 (Free ASH Whitepaper) 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.

(Press release, Abcuro, DEC 8, 2025, View Source [SID1234661301])