argenx's Sjögren's Flop Erased ~$9B — And Just Rewrote the FcRn Class Math

UNITY was a randomized, double-blind, placebo-controlled 1:1 trial of weekly subcutaneous efgartigimod versus placebo, sized to detect a change in clinESSDAI at48 weeks — the systemic activity score used in the registrational bar in Sjögren's. Key secondaries tracked the proportion of patients reaching low disease activity (clinESSDAI < 5), STAR responder status, DiSSA patient-reported symptoms, and safety. The IDMC concluded at the interim that UNITY was unable to meet its primary endpoint, and argenx said it will run a comprehensive analysis after database lock to inform future Sjögren's research. No specific responder-rate or withdrawal numbers were disclosed.

argenx shares closed October 7 at $928.44 on Nasdaq and were trading around €975 on Euronext Brussels before the press release. By the end of the October 8 European session, argenx had fallen roughly 16% on the news per multiple media reports, with the Brussels stock last quoted at €816.60 on argenx's investor relations page. At a pre-halt market capitalization of approximately $57.7B per the most recent company overview, the day erased roughly $9B of equity value.

The Sjögren's loss does not break the broader FcRn class — it was already largely settled. Novartis's ianalumab, an anti-BAFF rather than anti-FcRn but the headline Sjögren's asset, hit its primary endpoint in both NEPTUNUS-1 and NEPTUNUS-2 in August 2025 and earned FDA Breakthrough Therapy Designation in January 2026, putting it on track to be the first targeted Sjögren's therapy. In warm autoimmune hemolytic anemia, J&J's Imaavy (nipocalimab-aahu) became the first FDA-approved therapy on August 24, 2026, with no other FcRn agent approved in the disease.

The competitive shape of the FcRn market was already a four-player race in generalized myasthenia gravis (Vyvgart, Imaavy, Rystiggo, and Immunovant's IMVT-1402 in development). Unity's halt does not affect that market, but it does eliminate the one chronic autoimmune indication where argenx was first to the registrational line. With Novartis on track to file ianalumab for Sjögren's in 2026, the indication now looks like a Novartis monopoly on the play.

argenx trades at 11.25x P/S TTM with a 32.9% net margin and a TTM revenue base of $6.0B per its most recent 10-Q. Versus J&J at 6.36x P/S and Novartis at 4.72x, the gap reflects the optionality argenx's pipeline had been priced to deliver — specifically, indications like Sjögren's, pemphigus, and Graves' where the FcRn thesis would either re-anchor the bull case or quietly compress. With the Sjögren's pillar removed, the marginal pipeline readout (ALKIVIA myositis win already in; ITP ADVANCE-NEXT 1H27; Empasiprubart MMN EMPASSION 4Q26; FB102 celiac in hand) carries more weight per data point than before.

Short-term (days to quarters): the share price halts with argenx on three threads — Q3 Vyvgart sales on October 22, any re-rating from Deutsche Bank or other covering banks after the company's last downgrade-to-Hold pre-halt, and the first post-halt update on Empasiprubart MMN EMPASSION in Q4 2026. The $1,180 average analyst target was set pre-halt; post-halt Street targets likely settle in the $850–$1,000 range pending the October22 print.

Long-term (one to three years): the bigger question is whether argenx's franchise model — efgartigimod as anchor, Empasiprubart (anti-C2) and FB102 (anti-CD122) as second wave — emits TRUE diversification rather than FcRn-monoculture. UNITY's halt shows the FcRn class is mechanism-specific, not franchise-elastic; Vyvgart's continued compounding now depends on ALKIVIA, ITP, and oMG, with Sjögren's structurally out of the model. If Q3 2026 Vyvgart prints above $1.6B and ALKIVIA's sBLA stays on a 2027 launch track, the franchise readjusts to a high-growth, narrower-claim business that still deserves a healthcare large-cap premium.