Phase 1 4A10 (ALT-101) tests anti-CD127 (IL-7Rα) blocking antibody in R/R ALL/LL.

Allterum Therapeutics’ first-in-human, open-label Phase 1 study evaluates 4A10, an IgG1 monoclonal antibody that binds CD127 (the IL‑7 receptor alpha chain) to block IL‑7 survival signaling and promote immune-mediated killing (via Fc effector function) in malignant lymphoblasts. Patients with relapsed or refractory acute lymphoblastic leukemia (T-ALL or B-ALL) or lymphoblastic lymphoma (T-LL or B-LL) receive IV 4A10 on a weekly schedule in 28-day cycles in a single-arm dose-escalation design, with safety/tolerability, pharmacokinetics, and pharmacodynamics as primary early objectives alongside preliminary antitumor activity. The scientific angle is target selection: CD127 is implicated in IL‑7–driven growth programs, particularly relevant in T-lineage disease biology, making this a pathway-directed immunotherapy rather than another cytotoxic or CD19/CD22-only approach. For R/R ALL/LL today, care is typically sequential salvage regimens (often including blinatumomab for CD19+ disease, inotuzumab for CD22+ disease, and CAR-T in eligible patients) followed by allogeneic transplant when feasible; this trial explores whether IL‑7Rα blockade can add a new, antigen-agnostic lever for resistant disease.