📰 What This Document Is 🧬

This filing is an 8-K report—a mandatory filing used to announce material corporate events. It is structured as a press release detailing the incredible results of a major clinical trial. You should expect a deep dive into the science, the clinical data, and the company's plans for the future.

👉 The headline is blockbuster: Kyverna announced extremely positive data from its registrational trial for miv-cel in Stiff Person Syndrome (SPS), suggesting a potential one-time, curative treatment.

⚕️ What is Stiff Person Syndrome (SPS) 🧐

Kyverna Therapeutics is a late-stage biopharmaceutical company focused on developing cell therapies for autoimmune diseases. The condition they are targeting, Stiff Person Syndrome (SPS), is a rare and debilitating neurologic autoimmune disease.

• SPS causes progressive disability due to extreme muscle stiffness, painful spasms, and rigidity in the torso, arms, and legs.
• The condition progresses severely, sometimes leading up to 80% of patients losing mobility and requiring walking aids or a wheelchair.
• Crucially, the document notes that there are currently no FDA-approved treatments for SPS, highlighting a massive unmet medical need.
• An estimated 6,000 patients in the United States are diagnosed with SPS, but current treatments are primarily symptomatic or immunotherapies with poor patient response rates.

🧪 The Science: How miv-cel Works 💉

The core of the company's strategy revolves around a therapy called miv-cel (mivocabtagene autoleucel, KYV-101). This is a cutting-edge type of treatment known as a CAR T-cell therapy.

• What is it? Miv-cel is a fully human, autologous, CD19-targeting CAR T-cell therapy. "Autologous" means it uses the patient's own immune cells.
• The Mechanism: It is designed to achieve deep B-cell depletion and an "immune system reset" with a single administration.
• Why is this important? Since autoimmune diseases are often caused by overactive immune system cells (B-cells), miv-cel aims to reset the system rather than just suppressing symptoms, offering a potentially lasting, disease-free remission.

🚀 Breakthrough Results in the KYSA-8 Trial 🏆

The filing details the positive primary analysis results from the KYSA-8 trial, which was a single-arm Phase 2 registrational study of miv-cel for SPS. The results were presented at the American Academy of Neurology (AAN) Annual Meeting in Chicago.

• The Goal: The trial assessed miv-cel in 26 patients who had an inadequate response to prior treatments. The primary goal was to see how the treatment impacted walking ability after 16 weeks.
• The Findings: The results were overwhelmingly positive, demonstrating rapid, statistically significant, and clinically meaningful improvements across all measured endpoints.
• Primary Endpoint: The trial successfully met its primary endpoint, showing a statistically significant improvement in the Timed 25-Foot Walk (T25FW) at Week 16 (p=0.0003).

🚶‍♂️ Functional Improvement in Patients 👣

The improvements in physical function are the most impactful takeaways, signaling a dramatic shift in the disease course for the patients.

• Walking Ability: Median improvement in the T25FW was 46% from baseline. This is crucial because a faster walk means better independence and quality of life.
• Near-Normal Function: 81% of patients achieved a clinically meaningful improvement (a reduction of $\geq 20%$ from baseline).
• Independence: Of the 12 patients who required a walking aid at baseline, 67% no longer needed assistance at Week 16, pointing to regained functional independence.
• Treatment Freedom: Critically, all 26 patients remained free of needing chronic immunotherapies even through the last follow-up, addressing the core challenge of SPS management.

📊 Other Clinical Endpoints and Deep Signals ✨

The data didn't stop with walking speed. The company also provided significant data on secondary and exploratory measures, which reinforced the drug's unique potential.

• Disability Scores: The trial met all secondary endpoints, showing significant mean improvements in the Modified Rankin Score (mRS), Hauser Ambulation Index (HAI), Distribution-of-stiffness Index (DSI), and Heightened Sensitivity Scale (HSS).
• Biological Markers: Exploratory measures showed significant reductions in GAD65-autoantibody titers (antibodies related to SPS). This connects the clinical improvement directly to the biological mechanism of action.
• Immune Reset: These results suggest a sustained clinical benefit linked to deep B-cell depletion and a broad immune system reset, moving beyond temporary symptom management.

✅ Safety and Tolerability Profile 🛡️

The drug was shown to be safe and manageable, which is a major hurdle for any new biologic therapy.

• High-Grade Events: No high-grade Cytokine Release Syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS) were observed.
• Neutropenia: The only adverse event noted was Grade 3/4 neutropenia (a drop in white blood cells), observed in four patients. The report emphasized that this was a "known AE associated with lymphodepletion and CAR T-cell therapy" and was manageable.
• Serious Events: Three serious treatment-related AEs occurred, but importantly, they all resolved fully without lasting consequences.

📈 Natural History Study Context 🗺️

To underscore the need for a new treatment, the filing also presented results from a natural history study.

• The Study: This retrospective analysis looked at 153 patients with SPS who were receiving standard, off-label care.
• The Outcome: The majority of these patients showed minimal ($<20%$) or no improvement in walking speed over time. This confirms that the disease is relentlessly progressive under current care paradigms.

💬 Executive Commentary and Strategic Vision 🎤

Multiple executives provided high-signal commentary, framing the results as a potential revolution in care.

• Warner Biddle, CEO: Stated, “We see compelling evidence that a one-time therapy can reset the immune system, reverse the course of disease, and free patients from lifelong treatment burden. With no approved therapies, we believe miv-cel could redefine the treatment paradigm for this debilitating, progressive disease.”
• Amanda Piquet, M.D. (Lead Investigator): Stated, "The ability of miv-cel to significantly decrease disability, stiffness, and hypersensitivity, and improve mobility... is unprecedented and highly promising for this underserved patient population.”
• Naji Gehchan, M.D. (Chief Medical and Development Officer): Focused on the mechanism, noting that miv-cel is designed to "enable a broad immune reset," providing clinical evidence for a durable, single-dose treatment.

🔭 Future Pipeline and Development Plans 🗓️

The positive SPS data is just one piece of a larger picture. Kyverna is using these results to advance its overall pipeline.

• Regulatory Focus: The company is preparing a Biologics License Application (BLA) submission for miv-cel for the initial indication of SPS.
• Broad Potential: The data also strengthens confidence in miv-cel's therapeutic potential in generalized myasthenia gravis (gMG), as well as other neurologic autoimmune diseases.
• Other Indication: Kyverna is also advancing studies in other areas, including multiple sclerosis and rheumatoid arthritis, demonstrating a commitment to developing a multi-disease platform.

📞 Investor Relations and Next Steps 📧

The filing provided specific logistical details for investors needing more information.

• Upcoming Call: Kyverna is hosting a conference call on Wednesday, April 22, 2026, at 7:00 a.m. ET.
• Topics: The call will review the SPS results and updated Phase 2 generalized myasthenia gravis (gMG) data from the KYSA-6 trial.
• Contact: Investors can find materials and register via the "Events & Presentations" section of the website at ir.kyvernatx.com.
• Support: For investor queries, the email is [email protected].

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🧠 The Analogy

Think of the current treatment for SPS as trying to control a massive house fire by repeatedly applying bandages (immunotherapies). The bandages only cover the immediate burns (symptoms), and the fire (the underlying autoimmune inflammation) keeps burning, requiring constant, difficult, and often ineffective interventions. miv-cel, by contrast, is like a specialized fire suppressant that gets into the source of the fire—the immune system itself—and turns it off with a single, powerful treatment, offering a chance to completely reset the environment and restore normal living conditions.

🧩 Final Takeaway

Kyverna presented blockbuster data showing that its single-dose therapy, miv-cel, achieved dramatic, durable functional recovery and functional independence in SPS patients. The company is positioned to become a leader in neuroimmunology by potentially establishing a "one-time cure" paradigm for severe autoimmune diseases.