Rival Editors Converge on AATD as Data Mount

CRISPR Medicine News reported last week on AIRNA's AIR-001, an oligonucleotide that recruits the endogenous enzyme ADAR to rewrite the disease-causing message without touching genomic DNA. That brief now reads less as a standalone result than as one entry in a striking burst of AATD activity clustered around the recent American Thoracic Society (ATS) meeting in Orlando and the ASGCT meeting, where AIRNA presented. Within roughly a fortnight, Beam, Korro, Wave and YolTech all reported new data, and Sanofi weighed in with a competing protein. Few rare diseases have drawn so many modalities to the same single base in such a short window.

The reason is unusually clean biology. Most severe AATD is traced to the PiZ allele, a single G-to-A substitution in SERPINA1 that misfolds the AAT protein, that traps it inside hepatocytes, and leaves the lungs unprotected against neutrophil elastase. Correcting that one base – an A-to-G change – simultaneously stems the toxic liver burden and restores circulating, functional M-AAT. Both base editors and ADAR-based RNA editors can make exactly this edit, which is why the disease has become a head-to-head test of the two philosophies rather than a contest of targets.

RNA editors rewrite the transcript and stay reversible

The RNA-editing camp argues that working at the transcript level is inherently safer and more controllable. AIRNA's NSG-PiZ mouse data showed 59% editing of SERPINA1 in the liver and more than 40 µM of corrected M-AAT in serum, with no bystander or off-target edits detected, while non-human primate work pointed towards dosing every eight to twelve weeks. Korro pushed harder on potency, naming KRRO-111 as its AATD development candidate on the strength of more than 90% transcript editing, translating into roughly 90% functional M-AAT in a mouse model – making chief executive Ram Aiyar calling it »the highest level of SERPINA1 editing reported to date using RNA editing.« In repeat-dose PiZZ mice, KRRO-111 nearly halted active Z-protein production – cutting non-inclusion Z-AAT by about 95% – while pre-existing aggregates cleared progressively, the residual burden reflecting old disease rather than incomplete editing. Both companies, like Wave, deliver a GalNAc-conjugated oligonucleotide subcutaneously to the liver.

Wave's WVE-006 carries the RNA story furthest into the clinic. In the RestorAATion-2 trial, biweekly 200 mg dosing produced wild-type M-AAT at 64% of total AAT and cut harmful Z-AAT by 71%, with monthly 400 mg dosing giving comparable results and editing sustained at least three months after the last dose. Most notable was evidence that treated patients regained a dynamic response, raising AAT during acute infections – a physiological behaviour that augmentation therapy cannot mimic. Across the trial, rises in C-reactive protein tracked closely with rises in AAT (r=0.73), and one patient reached 20.6 µM of total AAT during an acute-phase response after a single dose. Treatment allowed patients to safely make their own M protein while decreasing their Z protein levels, D. Kyle Hogarth of the University of Chicago explained it. He called the reversible, genome-sparing approach a major step for the alpha-1 community.

DNA editors rewrite the gene for good

The DNA-editing camp counters with permanence and a single administration. Beam's BEAM-302, a liver-targeted lipid-nanoparticle adenine base editor, has now treated 29 patients in its Phase 1/2 trial, and the company is moving towards an accelerated-approval pathway with roughly 50 additional patients planned in a pivotal cohort from the second half of 2026. Because BEAM-302 corrects the gene in its native location, treated patients' AAT also rose physiologically during inflammation – a point Beam presses hard against protein replacement. Trial investigator John Hurst of University College London framed the data as the start of »the era of gene correction as a tool for clinicians.«

YolTech is the unexpected entrant. Its in vivo adenine base editor YOLT-202, which rewrites PiZ to PiM, has won FDA Regenerative Medicine Advanced Therapy and Orphan Drug designations and cleared an investigational new drug application for a single-dose Phase 2/3 study, while the first two patients dosed in an investigator-initiated trial reached AAT above the protective threshold with evidence of structurally corrected protein. That a Shanghai-based company is advancing an in vivo base editor towards pivotal testing underscores how international and how fast the contest has become.

One trade-off divides the whole field

The strategic fault line is straightforward. DNA editing offers a potential one-and-done cure but carries the irreversible risk of bystander edits, indels and off-target changes; RNA editing is reversible and titratable but commits patients to lifelong redosing every few weeks to months. Wave's chief medical officer, Christopher Wright, drew that line sharply, contrasting his approach with the »permanent mutations in the human genome with unpredictable effects« he attributes to base editing. Which trade-off regulators and payers ultimately favour will shape a market in which more than 100,000 PiZZ patients in the US alone remain mostly undiagnosed.

Sanofi's data complicate the editors' pitch in a useful way. Its recombinant AAT-Fc fusion efdoralprin alfa beat weekly plasma-derived augmentation in the Phase 2 ElevAATe study, holding functional AAT above the normal threshold on 100% of days with three-weekly dosing against 41% for standard of care. It is not gene editing and does not address the liver, but it raises the comparator bar: any editor seeking approval must now beat not only a forty-year-old augmentation standard but an improved protein nipping at its heels.

For now, the near-term catalysts are regulatory. Wave and Beam both expect FDA feedback on accelerated approval around mid-2026, Beam plans its pivotal cohort for the second half of the year, and YolTech's RMAT designation should quicken its dialogue with the agency. The 11 µM threshold long cited as protective against emphysema is now being cleared by several mechanisms at once. The open question is no longer whether the PiZ message can be corrected, but which way of correcting it patients will eventually be prescribed.

This report is based on recent press releases from AIRNA, Beam Therapeutics, Korro Bio, Sanofi, Wave Life Sciences and YolTech Therapeutics as well as our earlier report on AIRNA.