Skyhawk's SKY-0515 Shows 1.59-Point cUHDRS Advantage at 15 Months in Huntington's Disease
核心洞察
Skyhawk Therapeutics (搜索) reported final 15-month Phase 1/2 results showing SKY-0515-treated Huntington's disease (搜索) patients improved 0.94 points on cUHDRS versus a 0.65-point decline in external controls.
The 1.59-point cUHDRS difference (95% CI: 1.09, 2.09; p<0.001) favored SKY-0515 and was statistically significant across all four cUHDRS components.
At the 9 mg dose, SKY-0515 produced consistent average reductions of more than 60% in mutant huntingtin protein (搜索) and more than 25% in PMS1 (搜索) mRNA throughout the study.
Skyhawk Therapeutics (搜索) has reported final fifteen-month results from its Phase 1/2 clinical trial of SKY-0515, an investigational once-daily oral small molecule RNA splicing modifier for Huntington's disease (搜索), showing a statistically significant clinical advantage over an overlap-weighted external natural history control.
At the Month 15 primary timepoint, patients treated with SKY-0515 improved on the Composite Unified Huntington's Disease (搜索) Rating Scale (cUHDRS) by an average of 0.94 points from baseline, while the external comparison group declined by an average of 0.65 points. The between-group difference was 1.59 points (95% CI: 1.09, 2.09; p<0.001).
The advantage favored SKY-0515 across all four cUHDRS components: Total Functional Capacity (+0.98 points), Total Motor Score (−9.38 points, where a lower score is better), Symbol Digit Modalities Test (+4.15 points) and Stroop Word Reading Test (+4.18 points). All differences were statistically significant.
The same pattern held at every prespecified timepoint: 0.66 points at Month 3, 0.78 points at Month 6, 1.04 points at Month 9, 0.79 points at Month 12 and 1.59 points at Month 15, with statistical significance reached from Month 9 onward. On average, SKY-0515-treated patients' cUHDRS scores remained at or above baseline at every assessment through Month 15, while the external comparison group's average score declined from Month 6 onward.
Dual Mechanism Targeting mHTT and PMS1
SKY-0515 is designed to reduce both mutant huntingtin protein (搜索) (mHTT), the primary protein responsible for HD pathology, and PMS1 (搜索), a DNA repair protein and key driver of somatic CAG repeat expansion associated with disease progression. At the 9 mg dose, the drug has shown consistent average reductions of more than 60% in mHTT and more than 25% in PMS1 mRNA throughout the study.
"SKY-0515's dual reduction of mHTT and PMS1 (搜索) addresses two core pathogenic mechanisms of Huntington's disease (搜索)," said Dr. Samuel Frank, Director of the Huntington's Disease Society of America Center of Excellence at Beth Israel Deaconess Medical Center. "A 1.59-point cUHDRS difference versus a rigorously weighted natural history control at fifteen months is exactly the type of signal the field looks for in early studies of a potentially effective therapeutic agent."
SKY-0515 has demonstrated excellent central nervous system exposure and has been generally well tolerated across all dose levels studied through fifteen months of treatment, with no treatment-related serious adverse events.
Study Design and Analysis Caveats
The Phase 1/2 trial is a first-in-human study evaluating safety, tolerability, pharmacokinetics and pharmacodynamics in healthy volunteers and patients with early-stage HD (HD-ISS Stage 1, Stage 2, or mild Stage 3). Part C randomized patients to placebo, 3 mg or 9 mg for the first three months, followed by a twelve-month blinded Extension period during which all participants received active treatment at either 4 mg or 9 mg, with the majority on the 9 mg dose.
The fifteen-month analysis included 15 participants with an available Month 15 cUHDRS assessment. The decline in participant numbers partly reflects study design, as the twelve-month Extension period caps SKY-0515 exposure at 12 months for participants who initially received three months of placebo. A small number of participant-timepoints were also excluded following qualifying intercurrent events, including onset of an unrelated medical condition, initiation of a confounding medication, or a change in background HD therapeutic intervention.
Because all participants were receiving active treatment by Month 15, no concurrent placebo group was available; comparisons were made using overlap-weighted propensity score weighting against the Enroll-HD, 2CARE and CREST-E datasets (Month 15: n=1337). Independent commentary noted that an external control cannot perfectly recreate a randomized placebo group, and that unmeasured differences between groups could contribute to the apparent treatment effect. The analysis also did not report cerebrospinal fluid biomarker measurements or neurofilament light (NfL) levels, and did not specify how many of the 15 participants received the high versus low dose.
FALCON-HD Pivotal Program Advances
The worldwide Phase 2/3 FALCON-HD-004-WW pivotal study is now active across more than ten countries and twenty clinical sites, with the Phase 1/2 and FALCON-HD studies having enrolled more than 200 patients. FALCON-HD is a randomized, double-blind, placebo-controlled, dose-ranging study evaluating once-daily oral SKY-0515 at one of three dose levels or placebo in Stage 2 and Stage 3 HD patients.
FALCON-HD 004-ANZ has completed enrollment of 144 participants across sites in Australia and New Zealand. FALCON-HD 004-WW plans to enroll approximately 600 participants across more than 40 sites worldwide and is actively recruiting.
"The completion of this Phase 1/2 study with SKY-0515, showing statistically significant clinical benefit across every cUHDRS component, is a powerful demonstration of what Skyhawk's SKYSTAR platform can achieve: a daily pill, taken at home, that modifies RNA splicing to lower disease-causing proteins in the CNS and systemically throughout the body," said Sergey Pauskin, Co-founder and Head of R&D at Skyhawk.
Unmet Need and Patient Perspective
Huntington's disease (搜索) is a rare, hereditary and ultimately fatal neurodegenerative disorder affecting more than 40,000 symptomatic individuals in the United States, with hundreds of thousands impacted worldwide. There are currently no approved therapies shown to slow or halt disease progression.
"What makes SKY-0515 especially exciting is that it is a pill, taken once a day at home," said Katie Jackson, Chief Executive Officer of Help 4 HD International. "A therapy that is noninvasive and does not require care in a specialized center has the potential to reach so many more patients – in rural communities, in families who can't travel, and across the world where care is hard to come by."
Skyhawk expects to advance additional novel therapies targeting rare neurological diseases with no approved disease-modifying treatment into clinical development by the end of 2027.