Hutchinson-Gilford progeria syndrome (LMNA-related progeroid laminopathy)

Adenine base editing (ABE) has demonstrated transformative preclinical results in Hutchinson-Gilford progeria syndrome by correcting the canonical LMNA c.1824C>T mutation in mouse models. This proof-of-concept raises the question of whether ABE or other base editors could be adapted for additional pathogenic LMNA variants, including nonsense mutations like c.475G>T (p.Glu159Ter). While the canonical progeria ABE strategy targeted a specific C-to-T transition amenable to ABE correction, nonsense mutations present different editing requirements that may necessitate alternative base editing or prime editing strategies.

Koblan et al. (Nature 2021; PMID: 33408413) demonstrated that a single intravenous injection of AAV9-delivered ABE in a mouse model of HGPS corrected the pathogenic c.1824C>T variant in multiple organs, dramatically extending lifespan and improving vascular pathology. Whisenant et al. (Nat Commun 2022; PMID: 35654881) showed that transient ABE expression was sufficient to correct the mutation and improve skin phenotype, suggesting that permanent genomic integration of the editor may not be necessary. An editorial in NEJM (Kim & Eriksson 2021; PMID: 33826825) highlighted the broader implications of base editing for progeroid syndromes. The p.Glu159Ter variant (ClinVar: 694069) introduces a premature stop codon in exon 3 of LMNA via a G>T transversion. Unlike the classic progeria C>T transition correctable by ABE (A·T to G·C), reversing a G>T transversion would require either a cytosine base editor (CBE) to convert the complementary C·A back to C·G on the antisense strand, or prime editing to directly install the correct sequence. Both approaches have shown improving precision and delivery efficiency in recent years.

No preclinical or clinical data exist for base editing of the specific p.Glu159Ter variant. The proven ABE strategy for canonical HGPS cannot be directly applied to this nonsense mutation due to the different base change required. CBE and prime editing, while theoretically applicable, have different off-target profiles and editing efficiencies compared to ABE. Systemic AAV9 delivery raises concerns about immunogenicity and dose-dependent hepatotoxicity observed in other AAV gene therapy programs. LMNA is expressed in virtually all differentiated somatic cells, creating a challenge for achieving sufficient editing efficiency across all relevant tissues. The extreme rarity of individual LMNA variants makes clinical trial design for variant-specific therapies highly challenging.

Base Editing (BE4max) via LNP delivery is a rationale-driven therapeutic strategy for Hutchinson-Gilford progeria syndrome (LMNA-related progeroid laminopathy) targeting the LMNA c.317T>C (p.Leu106Pro) variant (Pathogenic, missense variant). The editing system (BE4max (cytosine base editor)) converts the pathogenic C to T (or G to A on the target strand), restoring the wild-type codon. Target tissue: Liver. Therapeutic goal: Correct the LMNA c.1824C>T (progerin) mutation in hepatocytes, vascular smooth muscle, and other affected tissues to reduce progerin production, normalize nuclear architecture, and extend survival. Risk profile: off-target Medium (bystander bases in editing window), delivery complexity Low, immunogenicity Low.

1. Molecular basis: LMNA NM_170707.4(LMNA):c.317T>C (p.Leu106Pro) is classified as Pathogenic (ClinVar variation ID 2098083). Molecular consequence: missense variant. Protein change: L106P. 2. Epidemiology: Extremely rare, with an estimated incidence of ~1 in 20 million births and global prevalent population on the order of 100–200 children alive at any time, with cases concentrated in countries with access to molecular diagnosis and registries (North America, Europe, selected other regions) [WEB-04, W 3. Standard of care: Supportive multidisciplinary care plus lonafarnib (ZOKINVY), an oral farnesyltransferase inhibitor approved to reduce risk of mortality in HGPS and certain processing-deficient progeroid laminopathies. Lonafarnib improves vascular pathology and survival but is not curative; additional off-label or i 4. Pipeline: For HGPS and progeroid laminopathies, one small-molecule (lonafarnib) has reached approval after Phase II/III studies. No gene-editing or ASO therapies have yet entered human trials; CRISPR adenine base editing of LMNA c.1824C>T using AAV9 has shown robust lifespan extension and vascular rescue in m 5. CBE clinical validation: BE4max (Koblan et al. 2018) is the gold-standard cytosine base editor. Multiple CBE programs are in clinical development for liver and hematologic targets.

1. No published data specifically correcting LMNA c.317T>C (p.Leu106Pro) with Base Editing (BE4max); strategy is based on general principles and must be validated preclinically. 2. PAM availability and bystander base analysis for the specific genomic context have not been performed. If no canonical NGG PAM positions the target within the editing window, PAM-flexible variants (SpRY) may be needed. 3. Long-term durability, off-target genome-wide effects, and immunogenicity in the target patient population require thorough preclinical and clinical evaluation.

LMNA c.1608+5G>A is a deep intronic splice-site variant that disrupts the consensus 5' donor site of intron 11, likely activating a cryptic splice site and generating an in-frame insertion that mimics progerin-like mRNA processing. Antisense oligonucleotide (ASO) therapy targeting the aberrant splice junction or the cryptic exon inclusion region represents the most mechanistically precise intervention. Concurrent farnesyltransferase inhibitor (lonafarnib) treatment addresses progerin protein toxicity orthogonally and should be considered as a combination backbone while ASO development matures.

The canonical HGPS mutation c.1824C>T (p.Gly608Gly) creates a cryptic splice site generating progerin with 50-aa deletion in exon 11—establishing the mechanistic precedent that exon 11 splicing is highly sensitive to sequence perturbations. Scaffidi & Misteli (Nat Med 2005, PMID:16116426) demonstrated that ASOs blocking the cryptic splice site in the canonical HGPS mutation restored normal lamin A splicing in patient fibroblasts. Lonafarnib (Zokinvy) received FDA approval in 2020 (PMID:33170951) based on 2.5-month median survival extension in HGPS, validating the progerin farnesylation pathway as a druggable target. For c.1608+5G>A, SpliceAI prediction (delta score >0.5 threshold) and ViennaRNA secondary structure modeling of the intron 11 region are recommended to define the cryptic exon boundary and design the ASO targeting window with optimal mismatch-free complementarity.

The cryptic splice product generated by c.1608+5G>A has not been experimentally characterized in patient-derived fibroblasts or iPSCs—establishing the precise aberrant mRNA isoform is prerequisite to ASO design. If the variant activates a novel cryptic donor rather than modifying exon 11 length, the resulting protein may differ structurally from canonical progerin, altering therapeutic strategy. ASO delivery to cardiovascular tissue (smooth muscle, endothelium) remains challenging—systemic 2'-MOE phosphorothioate ASOs achieve good liver and kidney distribution but poor vascular wall penetration, which is critical given that HGPS mortality is driven by accelerated atherosclerosis. Long-term ASO dosing in pediatric patients requires careful safety monitoring for thrombocytopenia and complement activation, known class effects.