Kali Therapeutics Announces First Patient Dosed in Phase 1a Clinical Trial of KT501 for Rheumatoid Arthritis

SAN MATEO, Calif., March 18, 2026 /PRNewswire/ -- Kali Therapeutics, a clinical-stage biotechnology company pioneering next-generation immune-resetting therapies, today announced that dosing is underway for the first cohort of patients in its Phase 1a clinical trial evaluating KT501. KT501 is a first-in-class CD19xBCMAxCD3 trispecific T-cell engager (TCE). The study is being conducted in adult patients with Rheumatoid Arthritis (RA).

A Transformative Milestone for Kali Therapeutics

The dosing of the first patient represents a foundational shift for Kali Therapeutics as it officially transitions into a clinical-stage company. This milestone represents the first clinical translation of the company's internal discovery engine and its proprietary CD3-masking platform, designed to deliver high-potency B-cell depletion with an improved safety margin.

"Entering the clinic with KT501 is a defining moment for Kali Therapeutics. It marks our transition from a discovery-focused organization to a clinical-stage company dedicated to delivering functional cures for patients with autoimmune diseases," said Weihao Xu, CEO of Kali Therapeutics. " By advancing our lead candidate into human trials, we are now positioned to evaluate our 'Immune Reset' hypothesis in a clinical setting. Dosing the first patient in this study is a pivotal step for the patients who live with the daily burden of RA. This is a critical step in our mission to prove that deep, multi-targeted B-cell depletion can fundamentally improve the treatment landscape for RA and beyond."

A New Frontier in Autoimmunity

KT501 is engineered to target a broad spectrum of B-cell populations, including plasma cells, by simultaneously binding to CD19 and BCMA. Unlike traditional B-cell therapies, KT501 is designed to maximize B-cell killing potency while significantly reducing the risk of cytokine release syndrome (CRS), a common hurdle for T-cell engaging therapies.

"We are deeply grateful to the patients, lead Principal Investigator Prof. Stephen Hall, and the clinical site teams for their commitment and dedication to this study," added Min Bao, M.D., Chief Medical Officer of Kali Therapeutics. "KT501 has the potential to achieve a fundamental 'immune reset' across a broad range of B-cell driven autoimmune diseases. Furthermore, through subcutaneous injection, KT501 offers significant advantages in ease of use and dosing flexibility. We look forward to characterizing how this multi-targeted approach may allow the immune system to repopulate in a healthy state, moving us toward a new era of durable remission."

About the Phase 1a Study

The First-in-Human (FIH) Phase 1a study (NCT07234773) is an open-label, dose-escalation trial designed to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of KT501 administered as a single subcutaneous injection in adult participants with RA. While the primary objective of this study is to establish a robust safety profile, the trial will also rigorously characterize B-cell kinetics, cytokine release profiles, and other relevant pharmacodynamic markers. These data will be essential in demonstrating KT501's potential to induce a deep "immune reset" safely.

About KT501

KT501 is a novel, IgG-like trispecific antibody. By targeting both CD19 (expressed on most B-cells) and BCMA (expressed on plasma cells), it addresses the limitations of previous-generation therapies that often spare the very cells responsible for autoantibody production. Its subcutaneous delivery and "off-the-shelf" availability provide a scalable and convenient alternative to complex cell-based therapies.

About Kali Therapeutics

Kali Therapeutics is a biotechnology company headquartered in San Mateo, California, dedicated to developing transformative therapies for autoimmune and inflammatory diseases. The company's pipeline focuses on "Immune Resetting" -- harnessing T-cell engagers and multi-specific antibodies to eliminate pathogenic immune cells and restore long-term immune homeostasis.

SOURCE Kali Therapeutics