Kyverna Shares Surge on Strong Topline Results From Phase 2 SPS Trial

Kyverna Therapeutics, Inc. (NASDAQ: KYTX) saw its stock price jump 26.20% to $11.08 in premarket trading on December 15, 2025, following the announcement of positive topline data from its registrational Phase 2 KYSA-8 trial.

The clinical-stage biopharmaceutical company reported that its experimental CAR T-cell therapy, mivocabtagene autoleucel (miv-cel), met the primary endpoint in patients with stiff person syndrome (SPS), a rare and debilitating autoimmune disorder.

The strong results position miv-cel as a potentially transformative treatment for a condition that currently has no FDA-approved therapies, marking a significant milestone for both the company and patients suffering from this challenging disease.

Phase 2 Trial Meets Primary Endpoint With 46% Median Mobility Improvement

The registrational KYSA-8 trial enrolled 26 patients with stiff person syndrome who had not responded to other treatments, administering a single dose of miv-cel and tracking outcomes for 16 weeks. The therapy demonstrated impressive efficacy, improving walking speed by a median of 46% at 16 weeks when measured using a standard mobility scale.

Remarkably, 81% of patients achieved at least 20% improvement, surpassing the threshold considered clinically meaningful for this debilitating condition.

The trial results revealed additional compelling benefits beyond mobility improvements. Two-thirds of patients who required walking aids before treatment no longer needed them following miv-cel administration, representing a dramatic improvement in functional independence. Perhaps most significantly, all patients in the study were able to discontinue other immunosuppressive therapies after receiving the single-dose treatment.

The therapy was also well-tolerated, with no severe cases of cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome, two serious side effects commonly associated with CAR T-cell therapies.

Kyverna plans to seek FDA approval in the first half of 2026, potentially making miv-cel the first approved CAR T-cell therapy for autoimmune diseases. This would represent a major breakthrough for the approximately one to two people per million affected by stiff person syndrome, a condition that predominantly impacts women between ages 20 and 60 and currently has no FDA-approved treatments available.

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KYTX Shares Surge Over 26% in Premarket Trading

Following the December 12 close at $8.78, KYTX shares surged to $11.08 in premarket trading on December 15, representing a 26.20% gain. The company’s market capitalization stood at $384.53 million as of the previous close, reflecting its status as a clinical-stage biopharmaceutical company with significant growth potential.

Year-to-date, KYTX has delivered exceptional returns of 134.76%, substantially outperforming the S&P 500’s 16.08% gain over the same period, and the stock has posted a one-year return of 96.86%.

Analyst sentiment remains positive on Kyverna Therapeutics, with the consensus rating standing at Buy and an average price target of $25.25, suggesting substantial upside from current levels. Most recently, Morgan Stanley maintained its Overweight rating on December 4, 2025, while raising its price target from $20 to $25.

The company operates with a relatively modest workforce of 129 full-time employees and focuses exclusively on developing cell therapies for autoimmune diseases, with its lead candidate KYV-101 (miv-cel) being evaluated for multiple indications including myasthenia gravis, lupus nephritis, multiple sclerosis, and systemic sclerosis in addition to stiff person syndrome.

Disclaimer: The author does not hold or have a position in any securities discussed in the article. All stock prices were quoted at the time of writing.