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KYTX Stock Rallies 23% on Upbeat Stiff Person Syndrome Study Data

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Key Takeaways

  • KYTX surged 23% after its registrational phase II KYSA-8 study met the primary endpoint in SPS.
  • Kyverna Therapeutics reported a 46% median T25FW improvement, with 81% of patients exceeding a 20% gain.
  • KYTX showed broad functional gains, 67% shed walking aids by Week 16 with a manageable safety profile.

Shares of Kyverna Therapeutics (KYTX - Free Report) surged 23.2% on Monday after the company reported positive top-line data from a registrational mid-stage study of its investigational candidate, mivocabtagene autoleucel (miv-cel, formerly KYV-101), for treating stiff person syndrome (SPS).

Miv-cel is KYTX’s fully human, autologous CD19-targeting CAR T-cell therapy with CD28 co-stimulation. The candidate has the potential to become the first FDA-approved CAR T therapy for an autoimmune disease.

KYTX’s Phase II SPS Study Data in Detail

Per data from the phase II KYSA-8 study, miv-cel met its primary efficacy endpoint, demonstrating a robust and sustained improvement in mobility with a highly statistically significant improvement in timed 25-foot walk (T25FW), with a median improvement of 46% at week 16. Notably, 81% of treated patients exceeded a 20% improvement in T25FW, a level generally considered clinically meaningful, supporting the robustness and relevance of the primary endpoint outcome.

Beyond the primary endpoint, miv-cel delivered consistent and highly statistically significant benefits across all secondary efficacy endpoints, indicating broad functional and symptom relief.

It was observed that 67% of the 12 patients who required walking aids at baseline no longer needed assistance to walk at Week 16. In addition, all patients remained free of immunotherapies, and none required rescue treatment through the latest follow-up, underscoring the therapy’s potential to provide sustained benefit while materially reducing or eliminating chronic treatment burden.

In the past year, shares of Kyverna Therapeutics have rallied 158.3% compared with the industry’s 11.6% growth.

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From a safety perspective, Kyverna Therapeutics’ miv-cel was generally well tolerated, with no cases of high-grade cytokine release syndrome or immune effector cell–associated neurotoxicity syndrome reported. While some patients experienced grade 3/4 neutropenia, a known and expected risk with CAR-T therapies, these events were manageable, supporting a favorable and controllable safety profile in the context of its clinical benefit.

SPS is a rare, progressive neurologic autoimmune disorder marked by muscle stiffness and painful spasms that severely impair mobility and gait, with up to 80% of patients eventually losing the ability to walk and facing increased disability and mortality risk. There are currently no FDA-approved therapies for SPS, leaving most patients inadequately served by existing symptomatic treatments and off-label immunotherapies.

Kyverna Therapeutics is looking to mitigate these gaps with miv-cel, which has shown significant potential in improving mobility as well as reducing stiffness and could become a standard-of-care option for SPS patients.

KYTX’s Next Steps in the Miv-cel Development Program for SPS

Following the positive phase II KYSA-8 results, Kyverna Therapeutics intends to file a biologics license application with the FDA for miv-cel in SPS in the first half of 2026. The investigational therapy has already secured Regenerative Medicine Advanced Therapy and Orphan Drug designations for this indication in the United States.

KYTX expects to present the complete SPS mid-stage data set at a medical conference in 2026.

Beyond the SPS indication, Kyverna Therapeutics is also currently evaluating miv-cel for other autoimmune indications, including myasthenia gravis, multiple sclerosis, rheumatoid arthritis, lupus nephritis, and systemic sclerosis, across separate early to mid-stage studies.

KYTX’s Zacks Rank & Stocks to Consider

Kyverna Therapeutics currently carries a Zacks Rank #3 (Hold).

Some better-ranked stocks in the biotech sector are ANI Pharmaceuticals (ANIP - Free Report) , CorMedix (CRMD - Free Report) and Castle Biosciences (CSTL - Free Report) , each sporting a Zacks Rank #1 (Strong Buy) at present. You can see the complete list of today’s Zacks #1 Rank stocks here.

Over the past 60 days, estimates for ANI Pharmaceuticals’ 2025 earnings per share (EPS) have increased from $7.29 to $7.54. Over the same period, EPS estimates for 2026 have surged from $7.79 to $8.15. Shares of ANIP have surged 46% in the past year.

ANI Pharmaceuticals’ earnings beat estimates in each of the trailing four quarters, delivering an average surprise of 21.24%.

Over the past 60 days, estimates for CorMedix’s 2025 EPS have increased from $1.85 to $2.87, while 2026 EPS estimates have risen from $2.49 to $2.88 over the same period. Shares of CRMD surged 32.7% over the past year.

CorMedix’s earnings beat estimates in each of the trailing four quarters, with the average surprise being 27.04%.

Over the past 60 days, the loss estimate for Castle Biosciences has narrowed from 65 cents to 34 cents in 2025. Over the same period, loss estimates for 2026 have improved from $2.10 to $1.06. CSTL stock has rallied 38.2% over the past year.

Castle Biosciences’ earnings beat estimates in three of the trailing four quarters and missed in the remaining quarter, with the average surprise being 66.11%.

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