A Multicenter, Real-world Natural History Study on Timed 25-foot Walk Outcome Measures in Stiff Person Syndrome
Scott Newsome1, Lowe Mallory2, Hanyeh Afshar1, Kelli Money2, Asli Buyukkurt1, Herbert R Chen1, Barrett Crawford1, Sadie Eggmann2, Aisha Elfasi1, Angeliki Fillippatou1, Munther Queisi1, Daniela Riveros Acosta1, Andrea Salazar-Camelo1, Jadyn Zook2, Norma Guzman-Becerra3, Jennifer Leslie3, Skye Geherin3, Amanda Piquet2
1Johns Hopkins Hospital, 2University of Colorado, 3Kyverna Therapeutics Inc.
Objective:
To evaluate longitudinal changes in timed-25-foot walk (T25FW) among patients with stiff person syndrome (SPS).
Background:
SPS is a rare autoimmune neurologic disease characterized by muscle stiffness and spasms, with progressive ambulatory dysfunction. Currently, there are no FDA-approved treatments for SPS, and a large subset of patients have an inadequate response to the use of off-label therapies, such as intravenous immunoglobulin (IVIg), as the disease progresses. T25FW is a validated tool to assess walking ability in other neurologic disorders and has been used to capture functional gait impairment in SPS. Additionally, T25FW is the primary endpoint of KYSA-8, the ongoing pivotal trial of KYV-101 CD19 CAR T-cell therapy in SPS. Herein, we present a large, multicenter, observational study to assess T25FW in patients with SPS.
Design/Methods:
Demographics, clinical characteristics, and relevant outcomes assessments were obtained for patients with a primary diagnosis of SPS from the University of Colorado and Johns Hopkins between 2012-2025.
Results:
The cohort included 183 patients with SPS. The median age at symptom onset was 44 years (range, 14-79), and the majority were white (75%) and female (68%). Classic SPS was the most common phenotype (71%); 29% had SPS-plus defined by classic features with cerebellar and/or brainstem involvement. GAD65, glycine receptor, and amphiphysin autoantibody positivity were detected in 66%, 9%, and 2% of patients, respectively. A full analysis of demographics, disease characteristics, treatment history, use of ambulatory devices, modified Rankin scale, and T25FW will be presented.
Conclusions:
This study represents the largest real-world natural history study to date examining the impact of SPS on walking speed. T25FW appears to be a clinically meaningful outcome measure in SPS, capturing key aspects of functional impairment. Ambulatory outcome measures may support the development of new therapies, including KYV-101, addressing a critical unmet need for patients with SPS.
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