Skyhawk Therapeutics Releases Twelve-Month cUHDRS Subcomponent Results from its Phase 1/2 Clinical Trial of SKY-0515 in Huntington's Disease

Twelve-month findings showed favorable and consistent trends for participants receiving SKY-0515 across all four cUHDRS subcomponents, including Total Functional Capacity (TFC), Total Motor Score (TMS), Symbol Digit Modalities Test (SDMT), and Stroop Word Reading Test (SWRT)

Skyhawk also releases Clinician and Patient Global Impression (CGI and PGI) improvement of disease survey data, which shows that at twelve months no clinician or patient assessed disease progression – all saw either disease stabilization, or improvement

BOSTON, June 30, 2026 /PRNewswire/ -- Skyhawk Therapeutics, Inc., a clinical-stage biotechnology company developing novel small molecule therapies designed to modulate RNA targets, announces cUHDRS subcomponent data from the twelve-month interim analysis of data from its Phase 1/2 clinical trial evaluating SKY-0515, an oral investigational treatment for Huntington's disease (HD).

The twelve-month data, shared at the European Academy of Neurology, shows favorable and consistent trends for participants on SKY-0515 across all cUHDRS subcomponents, including Total Functional Capacity (TFC), Total Motor Score (TMS), Symbol Digit Modalities Test (SDMT), and Stroop Word Reading Test (SWRT).At twelve months, participants receiving SKY-0515 demonstrated favorable mean change from baseline TFC score of +0.07, compared with an expected worsening of -0.87 points from propensity score-weighted analyses which use Enroll-HD natural history datasets.At twelve months, participants receiving SKY-0515 demonstrated favorable mean change from baseline TMS score of -2.00, compared with an expected worsening of 2.21 points from propensity score-weighted analyses which use Enroll-HD natural history datasets.At twelve months, participants receiving SKY-0515 demonstrated favorable stabilization of mean change from baseline SDMT score of -0.19, compared with an expected worsening of -1.78 points from propensity score-weighted analyses which use Enroll-HD natural history datasets.At twelve months, participants receiving SKY-0515 demonstrated favorable mean change from baseline SWRT score of +3.44, compared with an expected worsening of -3.13 points from propensity score-weighted analyses which use Enroll-HD natural history datasets.Skyhawk also released today Clinician and Patient Global Impression (CGI and PGI) improvement of disease survey interim data, assessed by clinicians or their participants over twelve months. For HD participants for whom Huntington's disease is expected to cause considerable disease worsening of over twelve months, no clinicians or participants assessed any worsening at twelve months and 65% of participants and 50% of clinicians assessed that there had been improvement.Treatment with SKY-0515 resulted in dose-dependent reductions in mutant huntingtin (mHTT) protein in blood of up to 69% as well as reductions in PMS1 mRNA of up to 26%. Mutant huntingtin is the primary protein responsible for HD pathology, while PMS1 is a key driver of somatic CAG repeat expansion associated with disease progression."We are pleased to share this exciting subcomponent data from our cUHDRS assessments, including TFC and TMS data on functional and motor capacity and SDMT and SWRT cognitive test data," said Sergey Paushkin, Head of R&D at Skyhawk Therapeutics. "And we are excited by the fact that participants and their clinicians, for whom Huntington's disease is expected to cause considerable disease worsening, see no worsening at twelve months — and 65% of participants and 50% of clinicians assessed that there had been improvement. This further confirms for us the exciting possibility that SKY-0515's compelling and consistent effect on the critical biomarkers of mHTT and PMS1 may offer Huntington's patients a type of therapy they have long deserved, in a convenient daily pill."SKY-0515 has demonstrated excellent central nervous system exposure and has been generally safe and well tolerated across dose levels studied. There are more than 175 participants enrolled in Skyhawk's SKY-0515 program, in five countries.Huntington's disease is a rare, hereditary, and ultimately fatal neurodegenerative disorder affecting more than 40,000 symptomatic individuals in the United States, with hundreds of thousands more impacted worldwide. There are currently no approved therapies shown to slow or halt disease progression.