An Elevated Interferon Signature and a Failed Anakinra Trial: Choosing Which JAK Pathway to Block
One candidate drug has real trial data in diseases like hers. The other has a cleaner mechanistic argument and a better long-term safety profile, but has never been tried in this disease at all.
Simone K., a 34-year-old woman who works as a museum conservator, has spent the past two years cycling through recurrent, tender, violet-red nodules over both lower legs that her dermatologist biopsied and described as a panniculitis-like process, alongside episodic fevers, joint pain, and a persistent, cold-sensitive discoloration of her fingertips that has occasionally progressed to small, painful digital ulcers. An extensive genetic workup, including sequencing of TMEM173/STING1 and other genes associated with known monogenic interferonopathies, came back negative — a real and not uncommon outcome in this disease category, where, as Crow and colleagues' interferonopathy series have documented, a meaningful fraction of clinically consistent presentations never yield an identified genetic cause. What her workup did find, on a specialized blood test measuring interferon-stimulated gene expression, was a markedly elevated interferon signature, a finding that functionally identifies her as having an interferon-driven autoinflammatory process even without a confirmed genetic diagnosis to name it.
A three-month trial of anakinra, started before the interferon signature result was available, produced no meaningful improvement in her skin lesions, fevers, or joint symptoms — a real, informative negative result rather than simply an inadequate trial, since her dose was appropriately titrated and adherence was confirmed. High-dose corticosteroids have produced partial control, but she has flared twice attempting to taper below a dose her endocrinologist has flagged as carrying real long-term risk given early signs of steroid-related bone density loss on a screening scan obtained six months ago. Between the anakinra failure and the interferon signature result, the team now has real, convergent evidence pointing toward a type I interferon-driven mechanism rather than the IL-1-dominant pathway anakinra was chosen to treat. What that evidence does not do is name a drug. Both candidates act downstream of the same interferon receptor, but the case for each rests on a different kind of claim — one on a small open-label experience in patients who at least carried the confirmed genetic diagnoses she lacks, the other on receptor biology alone. Neither has been studied in a genetically undiagnosed adult with a positive interferon signature, which is the only description that actually fits her.
Choosing between an evidenced drug and a better-argued one
Her failed anakinra trial and her elevated interferon signature both point away from IL-1 and toward the type I interferon pathway. Sanchez and colleagues' trial specifically studied JAK1/2 inhibition with baricitinib in interferonopathies and found real, meaningful benefit. I'd rather start with a drug that has actual trial experience in this disease category than lead with something entirely untested.
I take the trial evidence seriously, but I want to name baricitinib's real cost: JAK2 inhibition affects erythropoiesis and thrombopoiesis, and she's likely looking at years of therapy for a chronic disease. Deucravacitinib's greater selectivity for TYK2 — which sits directly downstream of the same interferon receptor, alongside JAK1 — gives it a real mechanistic argument for working here, with a meaningfully cleaner long-term hematologic profile.
I'm not claiming deucravacitinib has been proven to work in this disease — it hasn't been tried. I'm arguing the mechanistic case is strong enough, and the safety advantage large enough, that it deserves real consideration rather than automatic deference to whichever drug happened to be studied first.
I think the mechanistic argument is genuinely reasonable, but there's an asymmetry worth naming: baricitinib has real, if open-label, trial experience in this exact disease category. Deucravacitinib has none — not a worse trial, no trial at all, in any interferonopathy patient anywhere that I'm aware of.
I'd start with baricitinib, watching her blood counts closely given the concern you've raised, and reserve deucravacitinib specifically for if a genuine JAK2-attributable problem actually shows up. That sequences the two options by what's actually known about each, rather than betting her first real trial of this pathway on the one with zero disease-specific experience behind it.
Baricitinib was started with a defined hematologic monitoring schedule, and her corticosteroid taper was slowed rather than accelerated, addressing her prior flare pattern directly.
Not agreed: how long a baricitinib trial should run before the team considers switching to deucravacitinib if her clinical response is inadequate but her blood counts remain acceptable — a genuinely different trigger than the hematologic-toxicity switch point already agreed on. The Rheumatologist would give baricitinib a longer trial given its trial-level evidence in this exact disease category; the Clinical Pharmacologist would consider switching sooner on inadequate response alone, given deucravacitinib's real mechanistic rationale. Both agreed only that a defined response-assessment date, not an open-ended trial, should decide it — without yet agreeing on what that date should be.