Allterum Therapeutics is advancing 4A10, a fully human anti-CD127 IgG1 monoclonal antibody licensed from the National Cancer Institute, into a first-in-human clinical trial in adults with relapsed or refractory acute lymphoblastic leukemia or lymphoblastic lymphoma, marking the first time the compound will be tested in humans after receiving US FDA Fast Track, Orphan Drug, and Rare Pediatric Disease designations.
The Phase I study (NCT07586618) is an open-label, single-arm, 3+3 dose-escalation monotherapy trial enrolling approximately 24 adults with confirmed T-cell or B-cell ALL or lymphoblastic lymphoma who have relapsed or become refractory to prior therapy and have no remaining curative options. The trial is conducted at Texas Children’s Hospital in Houston, with Eric Schafer, MD, of Baylor College of Medicine serving as study chair. According to the trial record, the study was not yet recruiting as of May 2026, with a primary completion date of May 2028.
The primary objectives are to establish the recommended Phase II dose and to characterize the safety profile of 4A10 monotherapy through assessment of treatment-emergent adverse events at each dose level, graded according to CTCAE version 6. Patients receive 4A10 by intravenous infusion once weekly in 28-day cycles, with treatment continuing for up to six cycles in the absence of disease progression or unacceptable toxicity. Secondary endpoints include pharmacokinetic parameters as well as preliminary anti-tumor activity measures such as complete remission rate, complete remission with incomplete hematologic recovery, measurable residual disease negativity among responders, and the rate of patients proceeding to hematopoietic stem cell transplantation following treatment.
The trial excludes patients with CNS3 disease, DNA fragility syndromes such as Fanconi anemia or Bloom syndrome, trisomy 21, prior exposure to anti-CD127 therapies, and uncontrolled infections. The inclusion of both T-cell and B-cell disease subtypes across the single escalation arm reflects the broad CD127 expression profile that underpins the program’s rationale.
Biological rationale and the CD127 target
CD127, the alpha subunit of the interleukin-7 receptor (IL-7Rα), functions as a shared component of two distinct receptor complexes: the IL-7 receptor, formed with the common gamma chain, and the thymic stromal lymphopoietin receptor (TSLPR). Both complexes are expressed on T-ALL and B-ALL cells, and IL-7 signaling through CD127 has been implicated in leukemic cell survival and resistance to chemotherapy. By binding IL-7Rα, 4A10 acts as a receptor antagonist, blocking IL-7-induced pro-survival signaling, while its IgG1 Fc region engages immune effector cells to drive antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis against CD127-expressing leukemic cells, according to company press releases.
4A10 was invented by Scott K. Durum, PhD, a senior investigator in the Cytokine and Immunity Section at the NCI Center for Cancer Research, and subsequently licensed exclusively to Fannin, a Houston-based life sciences commercialization firm, which then assigned the license to Allterum Therapeutics upon the company’s formation as a Fannin spin-out. Allterum has since received support from the NCI’s Experimental Therapeutics (NExT) Program, an approximately USD 1 million NCI SBIR grant, and more than USD 20 million in grants from the Cancer Prevention Research Institute of Texas (CPRIT), which is also listed as a trial collaborator alongside the NCI.
The US FDA cleared Allterum’s investigational new drug application for 4A10 in October 2025, according to a company press release.
Competitive landscape
CD127 has attracted limited clinical-stage attention relative to more established ALL targets such as CD19, CD22, and CD3-engaging bispecifics. The most directly comparable clinical program in this mechanistic class is the anti-IL-7Rα antibody program pursued by OSE Immunotherapeutics, whose candidate lusvertikimab (OSE-127) has been evaluated in inflammatory indications including ulcerative colitis and primary Sjögren’s syndrome rather than in hematologic malignancies, reflecting a different therapeutic application of CD127 blockade. No other anti-CD127 monoclonal antibody appears to have entered clinical testing in ALL or lymphoblastic lymphoma based on publicly available information, which would make 4A10 a potential first-in-class agent for this indication if that status is confirmed.
In the broader relapsed or refractory ALL space, the competitive reference points are blinatumomab (Amgen, approved), a CD19/CD3 bispecific T-cell engager, and inotuzumab ozogamicin (Pfizer, approved), a CD22-targeted antibody-drug conjugate, both of which are established in B-cell ALL. For T-cell ALL specifically, approved targeted options remain more limited, which is one factor that may inform the design of this trial to include both lineages. The mechanistic distinction of 4A10 — direct receptor antagonism combined with Fc-mediated immune killing at a target not addressed by any currently approved ALL therapy — is the key differentiation the company is advancing into human testing, though no clinical data yet exist to evaluate whether this translates to meaningful anti-leukemic activity.
Primary completion of the trial is anticipated in May 2028, with overall study completion expected by September 2028, according to the trial record.
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