Seismic Therapeutic has dosed the first healthy participant cohort in the randomised Phase I trial of bifunctional antibody S-4321 to treat various autoimmune conditions.

The trial will evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of the antibody.

Discover B2B Marketing That Performs

Combine business intelligence and editorial excellence to reach engaged professionals across 36 leading media platforms.

Find out more

Designed with the company’s IMPACT platform, the antibody ‘agonises’ the programmed cell death protein-1 (PD-1) and Fc-gamma receptor IIb (FcγRIIb).

FcγRIIb and PD‑1 are said to be key inhibitory receptors that are ‘expressed’ on various immune cell types.

Seismic noted that the therapy functions as a non-depleting antibody, featuring ‘low-affinity’ binding to PD‑1 to optimally agonise T-cells, alongside highly selective FcγRIIb binding, agonising, antigen-presenting cells.

The placebo-controlled, double-blind trial will be carried out in two segments: a single ascending dose stage and a multiple ascending dose stage.

GlobalData Strategic Intelligence

US Tariffs are shifting - will you react or anticipate?

Don’t let policy changes catch you off guard. Stay proactive with real-time data and expert analysis.

By GlobalData

It aims to build upon preclinical evidence highlighting the antibody’s dual-functional properties.

In the trial, the mechanistic activity of PD-1 agonism, as well as selective FcγRIIb binding, will be assessed in healthy participants.

Seismic Therapeutic research and development (R&D) head and chief medical officer John Sundy said: “We are excited to begin clinical investigation of S-4321, to explore its safety and pharmacodynamic biomarkers in human subjects.

“By engaging inhibitory receptors on both sides of the T-cell/antigen presenting cell synapse, S-4321’s unique dual-cell activity has the potential for clinical benefit in diseases driven by dysregulated cell-mediated immunity.”

The company plans to develop the therapy for treating autoimmune conditions, such as inflammatory bowel disease, lupus, and rheumatoid arthritis.

According to the company, S-4321 differentiates from first-generation PD-1 agonists by targeting PD-1 without depleting the cell, thereby ‘preserving’ regulatory T-cells (Tregs).

Last month, the company dosed the initial cohort of healthy participants in a randomised Phase I trial of S-1117, a treatment for autoimmune diseases.

Clinical Trials Arena Excellence Awards - Nominations Closed

Nominations are now closed for the Clinical Trials Arena Excellence Awards. A big thanks to all the organisations that entered – your response has been outstanding, showcasing exceptional innovation, leadership, and impact

Excellence in Action
Science 37 has won the Research and Development Award in the Site Innovation category for its FDA inspected Direct-to-Patient Site model, delivering nationwide access, faster enrollment and higher retention. Explore how its virtual-first, in home approach is reshaping trial operations and accelerating time to data-driven decisions..

Discover the Impact