8-K: Kyverna's Miv-cel Shines in Stiff Person Syndrome Trial

Kyverna Therapeutics announced positive topline data from its registrational Phase 2 KYSA-8 trial of miv-cel in stiff person syndrome, showing statistically significant clinical benefit.

Summary

• Kyverna Therapeutics reported positive topline data from KYSA-8, its registrational Phase 2 trial of mivocabtagene autoleucel (miv-cel) in stiff person syndrome (SPS).
• Miv-cel achieved statistically significant clinical benefit across all primary and secondary endpoints at Week 16, reversing disability and eliminating immunotherapies after a single dose.
• The primary endpoint, timed 25-foot walk (T25FW), showed a highly statistically significant improvement (p=0.0002), with a median improvement of 46% at Week 16 compared to baseline.
• 81% of patients exceeded a 20% improvement in T25FW, a clinically meaningful threshold.
• All secondary endpoints, including Modified Rankin Scale (mRS), Distribution-of-stiffness Index (DSI), Hauser Ambulation Index (HAI), and Heightened Sensitivity Scale (HSS), also showed highly statistically significant benefits (all p-values <0.0001).
• Of the 12 patients who required a walking aid-device prior to treatment, 67% no longer needed assistance to walk at Week 16.
• 100% of patients remained free of immunotherapies and required no rescue therapy as of the last follow-up.
• Miv-cel was generally well-tolerated, with no high-grade cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS) observed.
• Grade 3/4 neutropenia, a known adverse event associated with CAR T treatments, was observed in certain patients and was manageable.
• Kyverna plans to submit a Biologics License Application (BLA) to the FDA for SPS in the first half of 2026.

Sentiment

Score: 9

Explanation: The filing reports highly positive and statistically significant topline data from a registrational Phase 2 trial for a novel therapy in an indication with no approved treatments. The efficacy results are strong, the safety profile is favorable, and the company has a clear path to BLA submission, indicating a significant advancement and potential market opportunity.

Positives

• Miv-cel achieved statistically significant clinical benefit across all primary and secondary efficacy endpoints in the registrational Phase 2 KYSA-8 trial for stiff person syndrome (SPS).
• The primary endpoint, timed 25-foot walk (T25FW), showed a highly statistically significant improvement (p=0.0002), with a median improvement of 46% at Week 16 compared to baseline.
• 81% of patients demonstrated a clinically meaningful improvement of over 20% in T25FW.
• All secondary endpoints (mRS, DSI, HAI, HSS) showed highly statistically significant benefits (all p-values <0.0001).
• 67% of patients who previously required a walking aid-device no longer needed assistance to walk at Week 16.
• 100% of patients remained free of immunotherapies and did not require rescue therapy, indicating potential for durable drug-free remission.
• Miv-cel demonstrated a well-tolerated safety profile with no high-grade cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS) observed.
• The results could pave the way for miv-cel to become the first FDA-approved CAR T-cell therapy for autoimmune disease and the first approved therapy for SPS.
• The company is on track to submit a Biologics License Application (BLA) for SPS in the first half of 2026.

Negatives

• Grade 3/4 neutropenia, a known adverse event associated with CAR T treatments, was observed in certain patients, though it was manageable.

Risks

• Uncertainties related to market conditions.
• The possibility that results from prior clinical trials, named-patient access activities, and preclinical studies may not necessarily be predictive of future results.
• The possibility that the FDA or other regulatory agencies may require additional trials or studies to support its intended BLA submission.
• Intellectual property rights.
• Other factors discussed in the Risk Factors section of Kyverna's most recent Annual Report on Form 10-K and Quarterly Reports on Form 10-Q.

Future Outlook

Kyverna anticipates submitting its Biologics License Application (BLA) for miv-cel in stiff person syndrome to the FDA in the first half of 2026. The company believes these results position miv-cel to become the first FDA-approved CAR T-cell therapy for autoimmune disease and the first approved therapy for SPS, potentially fundamentally shifting the treatment paradigm for B-cell-driven autoimmune diseases. Kyverna also plans to present the full SPS data set at a medical conference in 2026.

Management Comments

• Warner Biddle, CEO: "We are very pleased to share transformative topline data in stiff person syndrome, which could pave the way for miv-cel to become the first and only approved therapy in SPS and CAR T-cell therapy for autoimmune disease. Today's results further cement our leadership position in the autoimmune CAR T field and add to the growing body of evidence supporting miv-cel's potential to fundamentally shift the treatment paradigm in autoimmune diseases."
• Naji Gehchan, Chief Medical and Development Officer: "Today's topline data represent a significant breakthrough in the treatment of stiff person syndrome, demonstrating miv-cel's ability to reverse progressive disability in a debilitating disease that has no approved therapies. We believe these unprecedented results, which support our BLA submission, will have a profound impact on patients."
• Amanda Piquet, M.D., FAAN, Lead Investigator of KYSA-8 trial: "For these reasons, miv-cel's ability to significantly improve mobility and reduce stiffness is both remarkable and unprecedented, bringing hope to patients and their families who deserve better treatment options."

Industry Context

Stiff Person Syndrome (SPS) is a rare, progressive neurologic autoimmune disease with no FDA-approved therapies. Current treatment options are symptomatic or off-label immunotherapies, which often have significant side effects and are ineffective for the majority of patients, leading to progressive disability and loss of independence. Miv-cel's positive registrational Phase 2 data positions it as a potential first-in-class, FDA-approved CAR T-cell therapy for SPS and autoimmune diseases, addressing a significant unmet medical need.

Comparison to Industry Standards

• Stiff Person Syndrome (SPS) currently has no FDA-approved therapies, making miv-cel's potential approval a significant breakthrough as a first-in-class treatment.
• Existing treatments for SPS are off-label immunotherapies (e.g., IVIg, rituximab, plasmapheresis) and symptomatic treatments, which often fail to provide adequate response for the majority of patients.
• Miv-cel's ability to achieve statistically significant clinical benefit across all primary and secondary endpoints, reverse disability, and eliminate the need for other immunotherapies after a single dose, sets a new benchmark compared to the limited efficacy and chronic burden of current options.
• The observed safety profile with no high-grade CRS or ICANS is favorable, especially when considering the potential side effects and long-term management challenges associated with chronic immunotherapies.

Stakeholder Impact

• **Patients with SPS:** Potential for a transformative, first-in-class treatment that can reverse disability, improve mobility, reduce stiffness, and eliminate the need for chronic immunotherapies, significantly enhancing quality of life.
• **Shareholders:** Strong positive clinical data from a registrational trial significantly de-risks the asset and opens a clear path to market, potentially leading to substantial value creation and market leadership in autoimmune CAR T therapy.
• **Physicians/Healthcare Providers:** A novel and highly effective treatment option for a debilitating disease with no approved therapies, providing a new tool to address a significant unmet medical need.
• **Regulatory Authorities:** The positive data and planned BLA submission will be a key focus, potentially leading to the approval of the first CAR T-cell therapy for an autoimmune disease.

Next Steps

• Submit a Biologics License Application (BLA) to the FDA for miv-cel in stiff person syndrome in the first half of 2026.
• Present the full SPS data set at a medical conference in 2026.
• Continue advancing other KYSA trials and investigator-initiated trials in multiple sclerosis and rheumatoid arthritis.
• Develop next-generation CAR T-cell therapies to improve patient access and experience.

Key Dates

Recommendation

The positive topline data from the registrational Phase 2 KYSA-8 trial for miv-cel in Stiff Person Syndrome represents a significant breakthrough. The statistically significant efficacy across all endpoints, coupled with a favorable safety profile and the potential to be the first FDA-approved CAR T-cell therapy for an autoimmune disease and for SPS, positions Kyverna for substantial growth. The clear path to BLA submission in 1H 2026 and the addressing of a high unmet medical need make this a compelling investment opportunity.

Keywords

Kyverna Therapeutics, KYTX, miv-cel, KYV-101, CAR T-cell therapy, Stiff Person Syndrome, SPS, Autoimmune disease, Clinical trial results, Phase 2, Registrational trial, FDA approval, Biologics License Application, BLA, CD19, Neuroimmunology