Efdoralprin alfa
An investigational treatment for Alpha-1 Antitrypsin Deficiency.
The same compound appears under different names depending on the context. Here is how to identify Efdoralprin alfa wherever you encounter it, plus the key facts at a glance.
- Generic name
- Efdoralprin alfa
- Development codes
- INBRX-101, SAR447537
- Drug class
- Recombinant protein replacement
- Manufacturer
- Sanofi
- How it's taken
- In the ElevAATe trial, efdoralprin alfa was given as an IV infusion every 3 or 4 weeks, compared with weekly IV infusions of current plasma-derived treatment.
A lab-made version of the AAT protein that lasts longer in the body than blood-derived products, potentially allowing less frequent dosing. Given by IV infusion.
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How Efdoralprin alfa works
Efdoralprin alfa (formerly INBRX-101) is a new type of man-made protein that replaces the alpha-1 antitrypsin you're missing. Unlike the current treatment that comes from donated blood, this version is created in a laboratory using genetic engineering. It is built to last longer in your body, and in its Phase 2 trial it kept functional AAT levels higher than weekly plasma-derived treatment.
Mechanism: Recombinant human AAT-Fc fusion protein
Side effects and safety
In the Phase 2 ElevAATe trial, side effects were similar to weekly plasma-derived treatment, and no one permanently stopped the study drug because of a side effect[2].
The most common side effects, listed for dosing every 3 weeks, every 4 weeks, and weekly plasma-derived treatment, were COPD flare-ups (34.1%, 42.1% and 44.4%), headache (19.5%, 13.2% and 11.1%) and COVID-19 (17.1%, 2.6% and 16.7%). Antibodies against the drug showed up in 2 people; they were temporary and did not block the drug[2].
This was a 32-week study of 97 people, so longer-term safety is still being tracked in the ElevAATe open-label extension study (NCT05897424).
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Efdoralprin alfa
In the ElevAATe trial, efdoralprin alfa was given as an IV infusion every 3 or 4 weeks, compared with weekly IV infusions of current plasma-derived treatment. It is still in development and only available through clinical trials.
Clinical trial results
The Phase 2 ElevAATe study randomized 97 adults to the drug every 3 or 4 weeks or to weekly plasma-derived AAT. Sanofi reported in October 2025 that it met all primary and key secondary endpoints, with significantly higher functional AAT levels than the weekly standard treatment over 32 weeks[1].
Full results presented at the American Thoracic Society meeting in May 2026 showed that with dosing every 3 weeks, functional AAT stayed in the normal range on 100% of days, compared with 89.3% of days for dosing every 4 weeks and 40.8% for weekly plasma-derived treatment[2]. Sanofi said it is talking with regulators about next steps and has not announced a Phase 3 trial.
Main registered trial: NCT05897424 on ClinicalTrials.gov. Check it for the current status, sites and contacts before asking about enrollment.
Development history
Efdoralprin alfa was discovered by Inhibrx as INBRX-101 and acquired by Sanofi in 2024. It has been granted fast track status and orphan drug designation by the FDA. Sanofi now develops it under the name efdoralprin alfa (SAR447537).
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Common questions about Efdoralprin alfa
▸What is Efdoralprin alfa?
A lab-made version of the AAT protein that lasts longer in the body than blood-derived products, potentially allowing less frequent dosing. Given by IV infusion.
▸How does Efdoralprin alfa work?
Efdoralprin alfa (formerly INBRX-101) is a new type of man-made protein that replaces the alpha-1 antitrypsin you're missing. Unlike the current treatment that comes from donated blood, this version is created in a laboratory using genetic engineering. It is built to last longer in your body, and in its Phase 2 trial it kept functional AAT levels higher than weekly plasma-derived treatment.
▸What are the side effects of Efdoralprin alfa?
In the Phase 2 ElevAATe trial, side effects were similar to weekly plasma-derived treatment, and no one permanently stopped the study drug because of a side effect[2].
The most common side effects, listed for dosing every 3 weeks, every 4 weeks, and weekly plasma-derived treatment, were COPD flare-ups (34.1%, 42.1% and 44.4%), headache (19.5%, 13.2% and 11.1%) and COVID-19 (17.1%, 2.6% and 16.7%). Antibodies against the drug showed up in 2 people; they were temporary and did not block the drug[2].
This was a 32-week study of 97 people, so longer-term safety is still being tracked in the ElevAATe open-label extension study (NCT05897424).
▸How is Efdoralprin alfa taken?
In the ElevAATe trial, efdoralprin alfa was given as an IV infusion every 3 or 4 weeks, compared with weekly IV infusions of current plasma-derived treatment. It is still in development and only available through clinical trials.
▸Is Efdoralprin alfa FDA approved?
Efdoralprin alfa is currently in phase 2 clinical trials for Alpha-1 Antitrypsin Deficiency. It has not yet received FDA approval.
▸What is efdoralprin alfa (INBRX-101)?
Efdoralprin alfa (SAR447537, formerly INBRX-101) is a recombinant alpha-1 antitrypsin Fc-fusion protein being developed by Sanofi. Unlike plasma-derived augmentation therapy, it is produced through recombinant technology and engineered for extended half-life.
▸How does efdoralprin alfa differ from existing augmentation therapy?
Current augmentation therapy requires weekly IV infusions of plasma-derived AAT. Efdoralprin alfa's Fc-fusion design provides a longer half-life, potentially allowing less frequent dosing. It also avoids reliance on human plasma supply.
▸What is the current development status?
Efdoralprin alfa (INBRX-101) has completed its Phase 2 ElevAATe study, which met all primary and key secondary endpoints. Sanofi, which acquired the program from Inhibrx in 2024, presented the full results in May 2026, said it is talking with regulators about next steps, and has not announced a Phase 3 start.
▸What are the side effects of efdoralprin alfa?
In Sanofi's Phase 2 ElevAATe trial, efdoralprin alfa had side effects similar to weekly plasma-derived AAT, and no one permanently stopped it because of a side effect. The most common were COPD flare-ups, headache and COVID-19. Anti-drug antibodies appeared in 2 of 97 patients and were temporary and non-neutralizing, according to Sanofi's May 2026 results.
▸What advantages could recombinant AAT offer?
Recombinant production could provide more consistent supply without dependence on plasma donation, and longer dosing intervals through Fc-fusion engineering. In ElevAATe, doses every 3 or 4 weeks raised functional AAT more than weekly plasma-derived treatment.
Sources and references
Every factual claim on this page is drawn from the public sources listed below. Click any reference to open the original document.
- Sanofi · 2025-10-22. Sanofi's efdoralprin alfa met all primary and key secondary endpoints in alpha-1 antitrypsin deficiency emphysema phase 2 study. https://www.sanofi.com/en/media-room/press-releases/2025/2025-10-22-05-00-00-3170787
- Sanofi · 2026-05-18. ATS: phase 2 data demonstrate the superiority of efdoralprin alfa over a standard-of-care augmentation therapy in achieving higher fAAT levels in AATD. https://www.sanofi.com/en/media-room/press-releases/2026/2026-05-18-19-30-00-3296985