Redmond, Washington, U.S., September 22, 2026
SystImmune, Inc. has announced that the U.S. Food and Drug Administration (FDA) has cleared the Investigational New Drug (IND) application for SI-B037, an investigational bispecific antibody designed to target immunosuppression through coordinated mechanisms. The regulatory milestone enables SystImmune to move SI-B037 toward a planned Phase 1/1b clinical trial in patients with advanced solid tumors that have become refractory to standard therapies. The company said the FDA clearance also represents its first IND application supported by New Approach Methodologies (NAMs) as part of an integrated nonclinical safety and translational assessment package. SystImmune used human organ-on-chip systems and primary human tissue models in place of conventional animal toxicology studies for the nonclinical package. The company plans to evaluate SI-B037 in humans to determine appropriate dosing and characterize preliminary clinical activity.
FDA Clearance Advances Bispecific Antibody Program
The FDA’s IND clearance marks an important transition for SI-B037 from preclinical development toward clinical evaluation. The investigational antibody is being developed by SystImmune as part of its broader pipeline of next-generation bispecific and multispecific antibodies and antibody-drug conjugates (ADCs) for cancer treatment. According to the company, SI-B037 is designed to engage multiple biological mechanisms associated with tumor immunosuppression, with the objective of developing a coordinated therapeutic approach for patients whose cancers have progressed despite standard treatments. The planned Phase 1/1b study will provide the first opportunity to evaluate the candidate’s safety, tolerability, pharmacokinetics and potential clinical activity in patients. SystImmune said the program addresses an important area of unmet need because patients with advanced solid tumors refractory to standard therapies often have limited treatment options. The company intends to use the early clinical study to determine an appropriate dosing strategy while gathering initial evidence of how SI-B037 behaves in humans. As an investigational medicine, however, its safety and efficacy have not yet been established in clinical studies, and the potential therapeutic benefits remain to be determined through clinical development.
Human-Relevant Models Support IND Submission
A notable feature of the SI-B037 development program is the use of New Approach Methodologies (NAMs) in the nonclinical safety assessment. SystImmune reported that it used human organ-on-chip systems and primary human tissue models rather than conventional animal toxicology studies. These human-relevant models were incorporated into the integrated nonclinical and translational package submitted as part of the IND application.
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According to SystImmune, the approach was selected to provide more direct information from human-relevant biological systems for a molecule designed to engage multiple human pathways. The company described the FDA clearance as evidence of its continuing work in modern translational research and the application of human-centric testing approaches to biologics development. The use of NAMs in drug development is an evolving area, and SI-B037 provides an example of how biotechnology companies are incorporating alternative experimental systems into regulatory development programs.
SystImmune Plans Phase 1/1b Clinical Study
Following the IND clearance, SystImmune plans to initiate a Phase 1/1b clinical trial of SI-B037. The early-stage study is expected to focus on determining optimal dosing while characterizing the candidate’s initial clinical activity in patients with advanced solid tumors. The trial will also provide important information about the safety and tolerability of the bispecific antibody and help guide subsequent development decisions. SI-B037 joins SystImmune’s broader oncology pipeline, which includes multiple programs spanning bispecific and multispecific antibodies and ADC technologies. The company is developing these candidates across solid tumor and hematologic cancer indications, with programs at different stages ranging from discovery and IND-enabling development to clinical trials. The advancement of SI-B037 therefore adds another investigational biologic to the company’s clinical-stage portfolio.
The FDA clearance represents a regulatory milestone rather than evidence of clinical efficacy. The forthcoming Phase 1/1b study will be important for determining whether the bispecific antibody’s proposed mechanisms can translate into measurable therapeutic activity in patients. As clinical development progresses, safety, dosing and preliminary efficacy findings will help establish the future development path for SI-B037 in advanced solid tumors.
Source: SystImmune press release
