One Letter, Two Organs: Gene-Editing Companies Race to Develop a One-Time Treatment for AATD

Alpha-1 antitrypsin deficiency (AATD) causes two forms of harm at once: misfolded proteins become trapped in the liver, while the blood lacks enough normal protein to protect the lungs. This pathological structure—accumulation at one end and deficiency at the other—makes AATD an unusually promising target for gene editing. If the source can be corrected in liver cells, it may theoretically reduce liver toxicity while restoring the lungs’ defenses.

The race has moved from technical concepts into the clinic. Companies including Beam Therapeutics, Wave Life Sciences, Korro Bio, Tessera Therapeutics, and YolTech Therapeutics are exploring DNA base editing, broader gene rewriting, and RNA editing, respectively. Each approach seeks to address variants in the SERPINA1 gene, but they involve different trade-offs regarding how long the effects can last, whether a sufficient proportion of liver cells can be reached, and the risk of erroneous edits.

AAT is normally produced by the liver and, after entering the bloodstream, inhibits neutrophil elastase to prevent the continuous breakdown of lung tissue. The common severe Z variant causes AAT to misfold and accumulate in liver cells, potentially triggering inflammation and fibrosis; insufficient circulating AAT makes patients more susceptible to chronic obstructive pulmonary disease and emphysema. Patients with lung disease can currently receive regular intravenous augmentation therapy, but it cannot correct the genetic root cause or directly clear the abnormal protein accumulated in the liver.

In January 2026, Tessera received approval from the U.S. Food and Drug Administration for the investigational new drug application for its TSRA-196 trial, as well as ethics approval in Australia. This Phase 1/2, open-label, multinational first-in-human trial will administer a single intravenous infusion and assess safety, tolerability, and measures of AAT expression and function. The company says this is the first in vivo target-guided reverse-transcription genome-editing therapy authorized to enter human trials, but its actual editing efficiency and clinical effects still await answers from human data.

Moving faster, YolTech received authorization in March to begin the multinational Phase 2/3 study of YOLT-202. The therapy uses an adenine base editor in an attempt to convert the disease-causing PiZ variant into the PiM form. The company said that after receiving a single treatment, both participants in a preliminary study had AAT concentrations above the protective threshold of 11 micromoles per liter; the participant who received the 45-milligram dose exceeded 20 micromoles, and more than 95% of the measured AAT was corrected M-AAT.

However, the results from two people can only be regarded as an early signal. The data were disclosed by the company, and the sample is extremely small—insufficient to determine whether efficacy can be maintained over the long term or to rule out rare adverse reactions, off-target editing, immune responses, or liver-related risks. Although AAT concentration and protein function are important biomarkers, the treatment must ultimately be shown to reduce deterioration in lung function, liver fibrosis, and other clinical events.

AATD attracts multiple companies not only because the common severe variant is relatively well defined, but also because editing tools can be delivered directly to the liver using lipid nanoparticles and treatment effects can be measured quickly through AAT levels in the blood. The next focus of competition is not merely who can correct that one letter first, but who can use a single treatment to protect both the lungs and the liver over years of follow-up while reducing the risks associated with permanently rewriting genes to an acceptable level.