Clara Bennett: Hey, Finn — how's the kidney research rabbit hole treating you? You went very quiet on me yesterday.
Finn Brooks: Dude, I went down something I did not expect. Like I started reading FDA approval letters and then it was midnight. That has never happened to me with a regulatory document before.
Clara Bennett: That means we probably have something real today. What is the thing?
Finn Brooks: The thing is — okay, IgA nephropathy, IgAN, rare kidney disease, about 160,000 Americans. In a span of ten days this July, the FDA did two completely different things to two different drugs for the exact same condition. July 7th: accelerated approval for Trutakna — that's atacicept-vymj, made by Vera Therapeutics. July 16th — actually 16th and 17th — Fabhalta, iptacopan, by Novartis, gets converted from accelerated to full traditional approval. Both drugs. Same disease. The word approved on both of them.
Clara Bennett: Now that's the part I want to sit in, because a patient reading those labels sees the same word and assumes the same level of certainty.
Finn Brooks: Yes — except Trutakna's label is actually honest about it in a way I was not expecting. It states explicitly — like, written in the label — that long-term kidney function preservation has not been established. The FDA put the uncertainty in the document on the drug they just approved.
Clara Bennett: Wait — the label just says it? Out loud?
Finn Brooks: Right out loud — like a warning label on the approval itself. Which is what made me stop and think, okay, how does a system even get to that point? Where you approve something and simultaneously document what you can't guarantee?
Clara Bennett: That's the architecture of the whole pathway. Let me give you the one-sentence version: accelerated approval is a formal bet — the FDA accepts a proxy signal today in exchange for proof later, and patients are on the drug while the bet is still open.
Finn Brooks: Okay — what does proxy signal actually mean here, though?
Clara Bennett: Think of it like a school that awards you a diploma based on your GPA — betting that grades predict real-world performance — but schedules your final exam for after you've already graduated and started working. The GPA is proteinuria reduction. The final exam is whether your kidneys actually survive. And the accelerated approval pathway, Section 506(c) of the FD&C Act, was built on exactly that logic — it goes back to 1992, the HIV/AIDS epidemic, where patients were dying and there was genuinely no time to wait for decade-long outcome data.
Finn Brooks: So the urgency logic was real then — like, actually real.
Clara Bennett: It was. And now that same pathway is the one the FDA used for IgAN — a chronic condition, serious but not six-months-fatal. The manufacturer commits to confirmatory trials. If those fail, the drug can be withdrawn. But — and this is the part that matters — by then, patients have already been on it. Fabhalta ran under accelerated approval from August 2024 until July 2026. That's nearly two years of real prescriptions written on an unconfirmed surrogate endpoint.
Finn Brooks: Wait — two years is the good outcome. That's the one that converted to traditional approval because the APPLAUSE-IgAN trial actually came back with hard eGFR data. What if ORIGIN 3 — Trutakna's confirmatory trial — doesn't?
Clara Bennett: That's exactly where the structure gets uncomfortable. The surrogate endpoint — proteinuria reduction — its correlation with actual kidney preservation is assumed at approval, not proven. So right now, Trutakna's label saying long-term kidney function hasn't been established isn't a caveat. It's a structural feature of the pathway.
Finn Brooks: And that's the part that's messing with me — because Fabhalta is the success case. Like, Novartis ran APPLAUSE-IgAN, the two-year data came back, 48% slowing of eGFR decline versus placebo. First complement inhibitor to hit a hard kidney endpoint. The FDA converts it to traditional approval July 16th, 2026. The system worked. And it still meant 24 months of prescriptions written before anyone knew if it actually preserved kidneys.
Clara Bennett: So the system worked.
Finn Brooks: It worked! And — wait, actually, that's not fully right — the thing that got me is Fabhalta's accelerated approval was August 2024. Traditional approval July 2026. That's not a delay, that's not a flaw. That two-year gap is baked into the design. It's the feature.
Clara Bennett: Exactly — the pathway was never meant to eliminate the uncertainty window. It was designed to run prescribing and confirmatory evidence in parallel. Which means, in practice, you have a nephrologist in, let's say, a Saturday morning clinic in December 2025, writing a Fabhalta prescription. The APPLAUSE-IgAN data doesn't exist yet. The drug's approval is real. The kidney endpoint is still an open question.
Finn Brooks: And the APPLAUSE-IgAN trial even showed proteinuria improvements as early as two weeks in — so there's something visible, something measurable happening fast — but eGFR over 24 months? That's what nobody had yet.
Clara Bennett: Right — and that gap between 'the surrogate moved' and 'the kidney was preserved' is exactly what the pathway asks everyone to sit with. Manufacturers, patients, clinicians. The risk is distributed across all three.
Finn Brooks: Which — mm, okay — the part that comes next, with ORIGIN 3 still running and Trutakna just entering the pathway through a completely different mechanism, genuinely unsettling. Two drugs, zero head-to-head data, both labeled approved.
Clara Bennett: The key is that 'working as designed' and 'resolved uncertainty' are not the same thing. Fabhalta proved the pathway can close. It didn't prove the wait is short.
Finn Brooks: But that 'both labeled approved' thing — that's not even the sharpest edge of it, because the mechanisms are completely different. Like, Trutakna hits BAFF and APRIL simultaneously — it's a dual inhibitor, B-cell survival factors, and nobody has ever gotten an approval on that target combination before, in anything, any indication —
Clara Bennett: First approved dual BAFF/APRIL inhibitor in any indication, yes — that's genuinely novel.
Finn Brooks: And Fabhalta is hitting the alternative complement pathway — completely different biology, like, a different arm of how IgAN actually causes damage. So a nephrologist Saturday afternoon, chart open, and the choice isn't between two versions of the same idea. It's between two separate biological theories about what's driving the disease.
Clara Bennett: With zero head-to-head data to distinguish them. ORIGIN 3 — that's Trutakna's Phase 3, NCT04716231 — is still running. The interim data is what got Trutakna approved. And that same trial is also the required confirmatory trial. It's doing both jobs at once.
Finn Brooks: Wait — the trial that's supposed to confirm whether it works is the same trial that's still going?
Clara Bennett: That's the structure. So the prescriber is, in effect — I mean, there's no softer way to say this — choosing between two experiments. One experiment just graduated. Fabhalta has two-year eGFR data now. The other experiment, ORIGIN 3, hasn't reported final results.
Finn Brooks: And they look identical on the prescription pad. The word approved is the same word.
Clara Bennett: Now — and this is where proteinuria gets complicated — the surrogate endpoint's predictive power isn't uniform across kidney disease subtypes. The FDA's bet that a 46% proteinuria reduction in Trutakna's interim data translates to preserved kidney function is genuinely uncertain. Not because the FDA made a mistake. Because that correlation, for this specific dual BAFF/APRIL mechanism, has never been tested to completion.
Finn Brooks: So if ORIGIN 3 fails — if the proteinuria reduction doesn't predict actual kidney preservation — every patient who started Trutakna after July 7th, 2026 was on an unproven therapy. And the label told them so, in writing, and somehow that was the protection.
Clara Bennett: That's the thing that keeps settling on me — ORIGIN 3 reads out, whenever that is, and the field will learn whether the bet on proteinuria was sound. Two futures. If it confirms kidney preservation, Trutakna is vindicated, Vera Therapeutics proved the BAFF/APRIL mechanism delivers, and the pathway did exactly what it promised. If it doesn't — the patients who started Trutakna after July 7th, 2026 will have been part of something that never quite had a name.
Finn Brooks: And the FDA can withdraw it — Section 506(c), that authority is real — but the patients who were already on it for two years by then... I mean, withdrawal doesn't reach backward. That's the part I can't locate a word for.
Clara Bennett: July 2026. One drug walks out the other side — Fabhalta, two-year eGFR data, traditional approval, confirmed. One drug walks in — Trutakna, surrogate endpoint, open trial. Same month. Same disease. The pathway's whole story, both ends of it, visible at once.
Finn Brooks: I started this reading an FDA approval letter at midnight thinking it was a weird document. It's actually — yeah. It's a contract with an open clause.
Clara Bennett: That's not a bad place to stop. Thank you for going down the rabbit hole.
