Electra Therapeutics doses first patient in ipsoprubart T cell trial
Electra Therapeutics has dosed the first patient in a Phase 1 study of ipsoprubart (ELA026) in relapsed or refractory T cell malignancies, the South San Francisco-based company announced on 5 May 2026. The move extends the clinical programme for the SIRP-targeting monoclonal antibody beyond its ongoing pivotal study in secondary hemophagocytic lymphohistiocytosis (sHLH), where earlier data provided the scientific rationale for the expansion.
T cell malignancies — a heterogeneous group of rare, aggressive lymphomas and leukaemias arising from mature or immature T lymphocytes — affect more than 13,000 patients annually in the United States. Existing treatment options are limited, and durable disease control remains difficult to achieve in the relapsed or refractory setting. The unmet need is substantial, and the absence of well-validated targets has historically made drug development in this space challenging.
Clinical design and prior data
The open-label Phase 1 study will enrol adults in two sequential parts. Part 1 will recruit up to 24 patients to identify up to two dosing regimens with acceptable safety profiles, with patients eligible for up to six treatment cycles (24 weeks). Part 2 will then evaluate the selected regimens in expansion cohorts. The primary endpoint is safety, covering drug-related toxicities and treatment-emergent adverse events; secondary endpoints include overall response rate, duration of response, and disease control rate. The study is registered on clinicaltrials.gov under NCT07465835.
The decision to open this study was driven by data from ipsoprubart's Phase 1b programme in sHLH. Among eight patients with lymphoma-associated sHLH — six of whom had T cell malignancies as the underlying disease trigger — the objective tumour response rate was 100%, with a complete response rate of 88%. Notably, one patient with T cell lymphoma who had progressed through more than five prior lines of therapy achieved a durable complete response on ipsoprubart monotherapy. Those findings were presented at the International Conference on Malignant Lymphoma in 2025.
Kim-Hien Dao, Chief Medical Officer at Electra, said the initiation of the study "reflects strong interest from clinical investigators who were highly encouraged by the anti-tumor effect observed within weeks of treatment with ipsoprubart in the Phase 1b study in sHLH." She noted that responses to monotherapy in heavily pre-treated patients underpinned the rationale for further evaluation.
Mechanism and competitive landscape
Ipsoprubart targets signal regulatory proteins (SIRP) expressed on immune cells, with the aim of selectively depleting pathological T lymphocytes and myeloid cells. The mechanism is designed to act through both direct tumour cell elimination and modulation of the tumour microenvironment. Electra positions ipsoprubart as first-in-class in the SIRP-targeting space for haematological malignancies, and the company is separately advancing ELA822, a second SIRP-targeted antibody aimed at activated T lymphocytes with potential use in immunology and inflammation indications.
The broader T cell malignancy landscape has seen incremental progress, with a handful of approvals in specific subtypes — including antibody-drug conjugates and targeted agents in peripheral T cell lymphoma — but no dominant platform equivalent to those seen in B cell malignancies. SIRP biology has attracted growing interest across immuno-oncology, with academic groups and a number of early-stage companies exploring related checkpoint and phagocytic pathways. Electra's head start with clinical data in the mechanism could prove a meaningful differentiator if the Phase 1 safety and response data hold up.
Near-term milestones for investors and clinicians to watch include Part 1 dose-escalation readouts, the emergence of any early efficacy signals, and progress from the parallel pivotal sHLH study, which could provide the company's first regulatory submission opportunity.