Before I tell you what this drug does, let me tell you what ROSAH syndrome is.

ROSAH stands for retinal dystrophy, optic nerve edema, splenomegaly, anhidrosis, and headache. Every letter is a symptom. It’s an autosomal dominant autoinflammatory disease caused by gain-of-function mutations in a gene called ALPK1. Patients slowly lose their vision. Their spleens enlarge. They can’t sweat. Most of them develop chronic inflammation that affects multiple organs.

It was first formally described in 2019. There are no approved treatments.

There are also no other ALPK1 inhibitors in clinical development, anywhere in the world.

Drug Farm became the first company to put one in humans and get data back.

At IMMUNOLOGY2026, Drug Farm presented Phase 1b results for DF-003, an oral small molecule ALPK1 inhibitor. Six adult patients with genetically confirmed ROSAH received the drug once daily for four weeks.

Four of six patients started sweating again. The symptom that puts the A in ROSAH, anhidrosis, reversed.

And then, when they stopped the drug, the anhidrosis came back. Which sounds bad, but it’s exactly what you want to see in a Phase 1b. It means the drug is doing the thing. Stop the drug, the disease returns. Restart it, presumably, and you get the effect back.

The company was founded in 2015. Their IDInVivo platform uses genetic screens in living animals combined with AI to identify novel drug targets. That’s how they found the ALPK1 opportunity in the first place.

Private. Based in Albany, New York, and Shanghai. Small team. Raised $56M Series A in 2021 and $27M Series C in 2023.

The regulatory pile is already impressive for a company with six patients worth of data. FDA Fast Track. Orphan Drug Designation. Rare Pediatric Disease Designation. Acceptance into the FDA’s Rare Disease Evidence Principles Process, which is a structured pathway for drugs in ultra-rare populations where traditional trial designs don’t work.

ROSAH is rare. Very rare. We don’t have exact prevalence numbers but the patient population is measured in hundreds, not thousands.

But ALPK1 is interesting beyond ROSAH. Drug Farm is also developing ALPK1-related programs for hepatitis B, heart disease, and kidney disease. The underlying mechanism is control of innate immune inflammation. Broad applications once you prove it works in a clean rare disease setting first.

Which is the classic precision rare disease playbook. Use the ultra-rare population to prove the biology. Expand into bigger indications once you have the validation. Several recent companies building on similar models have taken this approach, including Grace Science in NGLY1 deficiency.

Drug Farm hasn’t talked publicly about the expansion yet. But with clean human data showing target engagement, mechanistic biomarker changes, and reversible clinical benefit in a disease nobody else can treat, they don’t really need to.

The data does the talking.