SKY-0515 Reduces mHTT, Alexion C5 inhibitors Reduces Relapse Rate, Exploring Stem Cell Innovation in PD

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Welcome to the Neurology News Network, my name is Louie Pasculli and here’s a look at the top stories in Neurology.

Beginning with Huntington Disease news, In a randomized, double-blind, placebo-controlled interim phase 1/2 trial, patients with Huntington disease (HD) treated with the investigational oral RNA-splicing modifier SKY-0515 demonstrated sustained reductions in mutant huntingtin protein (mHTT) of up to 69% and favorable clinical outcomes through 12 months, according to Skyhawk Therapeutics, the drug manufacturer.¹

Notably, treatment with the agent was associated with positive changes from baseline on the Composite Unified Huntington Disease Rating Scale (cUHDRS), a key measure of disease progression in HD. Although the findings have not yet been published in a peer-reviewed journal, the results suggest SKY-0515 may have the potential to influence both disease-related biomarkers and clinical measures in HD, an inherited neurodegenerative disorder for which no disease-modifying therapies have been approved.²

Bill Haney, Co-founder and Chief Executive Officer of Skyhawk Therapeutics, said this in a statement. “The increasing separation of the clinical trajectories of treated participants from natural history expectations at the 12-month timepoint suggests exciting and sustained benefits for Huntington's patients. The magnitude and durability of lowering of critical biomarkers mHTT and PMS1, as well as encouraging 12-month clinical findings across all four of the critical cUHDRS subcomponents, reinforce our confidence in SKY-0515's differentiated mechanism and potential for dramatic therapeutic impact for patients.”¹

Transitioning to NMOSD news, Real-world findings from the global NMO SPOTLIGHT Registry suggest that complement C5 inhibition with eculizumab (Soliris; Alexion) or ravulizumab (Ultomiris; Alexion) was associated with substantial relapse reduction in adults with aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder (AQP4-Ab+ NMOSD), with no meningococcal infections reported.³

Presented at the 2026 Consortium of Multiple Sclerosis Centers (CMSC) Annual Meeting in Charlotte, North Carolina, the analysis included 56 adults with aquaporin-4 antibody-positive NMOSD enrolled in the registry as of October 14, 2024. Most patients were women (89.3%), and the median age at diagnosis was 46.5 years. Median exposure was longer for eculizumab (42.5 months; IQR, 22.2-54.3) than ravulizumab (5.3 months; IQR, 4.0-14.1), reflecting the earlier approval and longer clinical use of eculizumab in this population.³

In the year before starting an Alexion C5 inhibitor, 21 patients (37.5%) experienced 28 relapses, corresponding to an annualized relapse rate (ARR) of 0.50 (95% CI, 0.33-0.72). While receiving eculizumab or ravulizumab, 3 patients (5.4%) had relapses, with ARR reduced to 0.02 (95% CI, 0.00-0.05). Additionally, no patient experienced more than 1 relapse on treatment.³

The registry also included 15 patients who switched from rituximab to a C5 inhibitor. In the year before initiating eculizumab or ravulizumab, 6 of these patients (40.0%) had 7 relapses, for an ARR of 0.47 (95% CI, 0.19-0.96). After switching, none experienced a relapse while on C5 inhibitor therapy.³

Stem cell-based therapies continue to attract growing interest in Parkinson disease, with advances in regenerative medicine fueling new research, clinical trials, and patient questions. To help clinicians better understand this evolving area, the International Society for Stem Cell Research (ISSCR), in collaboration with Harvard Medical School, recently launched an educational course focused on stem cell medicine in Parkinson disease.

In this special NeurologyLive® Roundtable Discussion, developed in collaboration with the ISSCR, leading Parkinson disease experts Roger Barker, MBBS, MRCP, PhD, FMedSci, and Claire Henchcliffe, MD, DPhil, explore the rapidly advancing field of stem cell medicine and its potential role in the treatment of Parkinson disease. The series is anchored around ISSCR’s recently launched educational course, which was designed to provide clinicians with a comprehensive, evidence-based overview of stem cell science, clinical development, and emerging therapeutic applications in neurology.

Across this multi-episode discussion, the faculty examine the current state of stem cell–based therapies for Parkinson disease, including the rationale behind dopamine cell replacement approaches, the evolving clinical trial landscape, and the challenges of translating promising research into clinical practice. The conversation also highlights practical considerations for neurologists, from counseling patients about investigational therapies and stem cell tourism to understanding the latest advances in regenerative medicine and their potential implications for the future treatment of Parkinson disease and other neurologic disorders.

To watch the full piece and to get more direct access to expert insight, head to NeurologyLive.com. Be sure to tune in next week to remain informed on the latest in neurology. I’m Louie Pasculli, thanks for watching Neurology News Network.

REFERENCES
1. Skyhawk Therapeutics Announces Twelve-Month Interim Results from Phase 1/2 Clinical Trial of SKY-0515 in Huntington's Disease. Skyhawk Therapeutics. News Release. June 1, 2026. Accessed: June 1, 2026. https://www.prnewswire.co.uk/news-releases/skyhawk-therapeutics-announces-twelve-month-interim-results-from-phase-12-clinical-trial-of-sky-0515-in-huntingtons-disease-302786696.html?tc=eml_cleartime
2. Tabrizi SJ, Ghosh R, Leavitt BR. Huntington disease. Lancet. 2019;394(10197):555-572. doi:10.1016/S0140-6736(19)31280-7.
3. Sotirchos E, Obeidat AZ, Kim HJ, et al. Real-World Clinical Outcomes With Eculizumab and Ravulizumab in Aquaporin-4-Ab–Positive Neuromyelitis Optica Spectrum Disorder: Results From the Global NMO SPOTLIGHT Registry. Presented at: 2026 CMSC Annual Meeting; May 27-30, 2026; Charlotte, NC. Abstract RTH02.