Roche has exited both of its antisense oligonucleotide Huntington's disease programs after the Phase II GENERATION HD2 study of tominersen failed to demonstrate clinical benefit despite reducing mutant huntingtin and neurofilament light chain, while a separate allele-selective program, RG6496, was halted following preclinical chronic dosing findings. The decisions, communicated directly to the HD patient community in a July 2026 letter, were described as independent and data-driven. Roche has publicly commented on both terminations.
GENERATION HD2 trial specifics
The GENERATION HD2 trial (NCT05686551) was a randomized, double-blind, placebo-controlled Phase II dose-finding study enrolling 360 adults with prodromal or early manifest Huntington's disease. Participants received intrathecal infusions of tominersen at 60 mg or 100 mg, or placebo, every 16 weeks for a 16-month treatment period. The study was designed as a refined follow-on to the Phase III GENERATION HD1 trial (NCT03761849), which was halted in March 2021 after an independent data monitoring committee determined that the higher-frequency dosing arm — tominersen 120 mg every eight weeks — was producing outcomes worse than placebo. GENERATION HD2 sought to rescue the program by selecting a younger, lower disease-burden population and using lower, less-frequent doses.
Top-line results from GENERATION HD2, reported in July 2026 showed that tominersen was well tolerated with no new safety signals, and that it significantly lowered both mutant huntingtin protein and neurofilament light chain (NfL) in cerebrospinal fluid compared to placebo — confirming target engagement and a reduction in a biomarker of neuronal damage. Despite these findings, tominersen produced no meaningful impact on the primary clinical efficacy endpoint. The tominersen discontinuation announcement makes clear that functional disease progression was not slowed relative to placebo.
The outcome represents a second consecutive failure to convert pharmacodynamic success into clinical benefit. Across multiple studies, tominersen consistently lowered mutant huntingtin in the CNS without slowing disease progression. The results leave unresolved whether simultaneous suppression of wild-type huntingtin—which plays important roles in neuronal survival and axonal transport—limits the therapeutic potential of non-allele-selective huntingtin-lowering approaches.
POINT-HD and RG6496: preclinical toxicology ends first-in-human study
The POINT-HD trial (NCT07246941) was a Phase I first-in-human study of RG6496 (ION993). The study enrolled adults with early Huntington's disease who carry a specific single nucleotide polymorphism (SNP) on the mutant HTT allele — a genetic subpopulation estimated to represent approximately 40% of HD patients. The trial had recently opened and enrolled three participants at the time of discontinuation.
RG6496 was developed to address the core mechanistic limitation of tominersen. By targeting a sequence on the mutant HTT allele that contains a disease-associated SNP variant absent from the wild-type allele, the ASO is designed to discriminate between the two alleles at the single-nucleotide level — suppressing mutant huntingtin while preserving wild-type huntingtin expression.