Immediately following the stock drop, several prominent shareholder rights law firms, including Levi & Korsinsky, LLP and SueWallSt, announced the commencement of investigations into argenx SE for potential violations of federal securities laws [cite: 3, 17].
These investigations are aggressively exploring whether argenx executives made materially false or misleading statements to investors regarding the UNITY study and the broader development outlook for subcutaneous Vyvgart in Sjögren's disease prior to the futility halt [cite: 17, 18]. Specifically, plaintiff attorneys are seeking to determine if the company possessed data or insights indicating that the drug was failing earlier than disclosed, and whether management artificially inflated the stock price by projecting unwarranted optimism about the trial's prospects [cite: 17, 18].
What is the timeline for these legal proceedings? Typically, under the US Private Securities Litigation Reform Act (PSLRA), if an investigation uncovers sufficient grounds to draft a formal complaint, plaintiff attorneys will file a putative class action lawsuit in federal court. Following this initial filing, a mandatory 60-day deadline is triggered for investors to petition the court to be appointed as "lead plaintiff." Once a lead plaintiff is approved, an amended complaint is filed, which the company will almost certainly counter with a "Motion to Dismiss." This pre-trial procedural phase alone can stretch from 12 to 24 months. If the motion to dismiss is denied, the case enters a prolonged discovery phase. Consequently, unless swiftly dismissed by a judge, investors should expect this legal overhang to persist for at least one to three years.
While these types of "stock drop" lawsuits are highly common in the biotechnology sector and often face steep hurdles to prove actual fraudulent intent (scienter), they represent a tangible red flag. The investigations create an overhang of negative sentiment, generate adverse media headlines, and can distract management. If a lead plaintiff emerges and a formal class action lawsuit is filed, it could result in protracted litigation or a costly financial settlement.
Mitigating Clinical Developments: The FB102 Celiac Success
While the Sjögren's disease failure dominated the headlines, argenx simultaneously released highly positive data from a completely separate arm of its pipeline on the exact same day. This deliberate synchronization of news releases was likely an attempt to cushion the blow of the UNITY trial failure.
On October 8, 2026, argenx announced that its investigational drug FB102 successfully met its primary endpoint in a Phase 2 clinical trial evaluating its efficacy in adults with celiac disease (argenx Press Release) [cite: 19, 20, 21].
Validating the Forte Biosciences Acquisition
FB102 is a first-in-class monoclonal antibody designed to inhibit CD122, a critical receptor component involved in the signaling of interleukin-2 (IL-2) and interleukin-15 (IL-15) [cite: 19, 20, 22]. These inflammatory pathways are heavily implicated in the activation of disease-driving immune cells. By blocking CD122, the drug dampens the immune response while preserving overall regulatory T-cell function [cite: 20, 22]. Crucially, FB102 is not a homegrown argenx asset; it was acquired via the company's $2.2 billion buyout of Forte Biosciences in August 2026 (Pharmaphorum) [cite: 19, 22, 23].
Celiac disease is a chronic autoimmune condition where the ingestion of gluten—a protein found in wheat, barley, and rye—triggers a severe immune response that destroys the lining of the small intestine [cite: 20, 23]. There are currently no FDA-approved pharmaceutical treatments for celiac disease; patients must rely entirely on a strict, lifelong gluten-free diet to heal the intestine and prevent long-term complications, which is notoriously difficult to maintain [cite: 19, 20, 23].
The Phase 2 Data and Temporal Outlook
The randomized, double-blind, placebo-controlled FB102-301 trial enrolled 126 adult patients with confirmed celiac disease who had been well-controlled on a strict gluten-free diet for at least 12 months [cite: 9, 24]. During the trial, patients were randomized (2:2:1) and subjected to a controlled "gluten challenge" for eight weeks while receiving either intravenous infusions of FB102 (at two different dose levels) or a placebo [cite: 9, 20, 24].
The results were statistically significant. The primary endpoint measured the villous height-to-crypt depth (Vh:Cd) ratio at day 78—a direct histological measurement of the intestinal damage caused by gluten [cite: 9, 20, 22]. Patients treated with FB102 demonstrated a meaningful preservation of their intestinal lining compared to those on placebo (p=0.0176), proving that blocking CD122 can effectively prevent gluten-induced mucosal destruction [cite: 9, 22, 24]. Other broad efficacy measures, including intraepithelial lymphocyte (IEL) density and the villus height-to-crypt depth intraepithelial lymphocyte (VCIEL) composite score, provided additional evidence of clinical and inflammatory symptom improvement. Furthermore, no new safety signals were identified [cite: 20, 21, 24].
This clinical win is vital for argenx's long-term valuation. It validates the hefty $2.2 billion price tag paid for Forte Biosciences and demonstrates that argenx is successfully diversifying its pipeline beyond its heavy reliance on the FcRn inhibitor class (Vyvgart) [cite: 19, 22]. Following this Phase 2 success, argenx plans to rapidly advance FB102 into pivotal Phase 3 development for celiac disease [cite: 21, 22]. While the company has not confirmed the exact initiation date for the Phase 3 trial, clinical progression following a successful Phase 2 readout typically anticipates commencement within 12 to 18 months. Independent financial analysts at TD Cowen forecast that, assuming a successful Phase 3 program and subsequent regulatory approval, FB102 could achieve a commercial launch in celiac disease by 2031. This timeline could secure argenx a vital multi-year head start against competitors like Teva Pharmaceutical, whose rival anti-IL-15 antibody (TEV'408) is slated for a potential 2034 launch (Fierce Biotech) [cite: 22].