In vivo CAR-T just has been going absolutely nuts lately.
CREATE Medicines dosed first patient last week with a multi-cell HER2 CAR. Immunofoco went into the clinic with an LNP-mRNA BCMA CAR. AbbVie buys Capstan. Lilly buys Kelonia. Kite buys Interius. AstraZeneca buys EsoBiotec. Billions of dollars being thrown into the streets — and I’m still unconvinced.
Well, add one more to the list. Sail Biomedicines is showing up to ASGCT with NHP data.
The company disclosed preclinical data for its lead in vivo CAR-T program targeting autoimmune disease. The headline? B-cell depletion across blood, bone marrow, and lymph nodes at low doses.
Most B-cell-depleting therapies clear circulating B cells…that’s not a HUGE accomplishment. It’s the tissue-resident B cells in lymph nodes and marrow that are the hard ones.
This is also where autoimmune disease lives.
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Sail’s bet (and everyone else’s it seems) is that in vivo CAR-T is going to swallow the autoimmune CAR space whole.
To be honest, the math is hard to argue with.
Conventional CAR-T for lupus or MS or myasthenia gravis works – Kyverna held a 52-week MG response with KYV-101. But the manufacturing pipeline for autologous CAR-T costs hundreds of thousands of dollars per patient. The conditioning regimen carries real risk. And you have to wait weeks while the cells are made.
This is like, THE pitch for in-vivo CAR-T. Faster, cheaper, easier.
IF you can drop a dose of mRNA-LNP into a patient’s vein and get the same B-cell kill profile, the economics flip. Autoimmune CAR-T goes from a hundred-thousand-dollar bespoke product to something that looks more like a recurring biologic.
That’s a BIG “if.”
NHP B-cell depletion is encouraging but the field has been burned before by NHP data that didn’t translate. Transient expression is a feature for safety reasons, but it also means the dose-frequency question is wide open.
What separates Sail from the pack is the eRNA piece. They’re using engineered RNA (that’s the “e” in eRNA), not standard mRNA, with internal ribosome entry sites that allow more efficient and potentially more durable translation.
Whether that translates to better clinical activity than the LNP-mRNA approach that the other in vivo CAR-T companies are using is the question that ASGCT 2026 might start to answer.
One thing’s clear: the bottleneck for in vivo CAR-T isn’t whether it works. The biology has been convincingly demonstrated by half a dozen groups. The bottleneck is whose nanoparticle is the most selective, whose payload is the most durable, and who gets to a clean human readout first.
Sail is now visibly in that race.
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