Kyverna’s CAR-T Therapy Succeeds in Stiff Person Syndrome Trial and Targets First Autoimmune Approval

EMERYVILLE, CA – December 15, 2025 — Kyverna Therapeutics, Inc. today announced highly positive clinical data from a key study evaluating its CAR-T therapy, miv-cel, in patients with Stiff Person Syndrome (SPS), a rare and debilitating autoimmune disorder characterized by muscle spasms and stiffness.

Following the successful Phase 2 data, the California biotech is planning to file for U.S. Food and Drug Administration (FDA) approval in the first half of 2026. If approved, miv-cel would become the first commercial CAR-T therapy specifically approved for an autoimmune disease, marking a significant expansion of the technology beyond oncology.

Kyverna’s stock ($KYTX) reacted strongly to the news, surging 53% in early Monday trading.

Clinical Efficacy and Safety Profile

The data presented today comes from a single-arm, Phase 2 trial involving 26 patients with SPS. Patients received a single, one-time infusion of the miv-cel cell therapy.

• Mobility Improvement: Treatment with miv-cel led to a 46% improvement in mobility at Week 16, as measured by a timed walking test.

• Reduced Aid Dependence: A notable eight of 12 patients who required a walking aid prior to the therapy no longer needed one by Week 16.

• Reduced Chronic Treatment: Since receiving the CAR-T infusion, no patients have required other immunotherapies or rescue therapy for SPS, suggesting the one-time treatment may offer a durable benefit and reduce the need for chronic drug regimens.

Miv-cel’s safety profile was consistent with other CAR-T therapies: Sixteen patients experienced serious cases of neutropenia (a measure of white blood cell depletion). Mild-to-moderate cases of common CAR-T side effects, including cytokine release syndrome (CRS) and the neurotoxicity side effect known as ICANS (Immune Effector Cell-Associated Neurotoxicity Syndrome), were also reported.

Pioneering the Autoimmune Space

Stiff Person Syndrome is a small indication in the U.S., affecting approximately 6,000 patients. However, its use as a target indicates the growing industry focus on applying CAR-T technology to autoimmune conditions, with major pharmaceutical companies like Bristol Myers Squibb and Novartis also exploring this field.

“Stiff person syndrome is only the beginning for Kyverna,” stated Warner Biddle, Kyverna’s CEO, on an analyst call. “If approved, we will have a first-mover advantage with miv-cel. This advantage provides a springboard to launch into broader indications, including myasthenia gravis.”

Kyverna’s Phase 2/3 trial evaluating miv-cel in myasthenia gravis, another autoimmune neuromuscular condition, is currently ongoing and is expected to read out in 2027.