Biotech Stocks Cool as argenx Fails and Viatris Buys Pacira

A busy week for a sector that has lost momentum

The first full week of October gave biotech investors a lot to take in. On October 8, argenx reported a Phase 3 failure and a Phase 2 success on the same morning. Viatris agreed to a premium cash takeover of Pacira BioSciences. Biohaven signed a regional licensing deal worth up to $100 million in near-term payments. BridgeBio got a priority review date from the FDA. These announcements arrived as the sector's strongest rally in years has started to stall, and taken together they explain the current market better than any single headline. Biotech is no longer rising across the board. Individual results are what move stocks now.

The headline numbers still look good. The SPDR S&P Biotech ETF (XBI) started 2026 at about $122 and was trading near $151 in early October, a gain of roughly 24% for the year.18 In mid-September it was up 26% year to date, compared with 12% for the S&P 500.15 The fund reached a 52-week high of $169.89 on August 25 and has drifted lower since then.1719 Its price has slipped below its 50-day moving average of about $158.50, though it remains above its 200-day average near $145.70.19

Bull and bear cases look at the same chart

Analysts disagree sharply about where things go from here, even though they are using the same data. A bullish InvestorPlace piece points out that XBI has climbed about 130% from its April 2025 low of $66, when tariff fears hit the sector. It says the fund needs to rise about 15% to break its February 2021 all-time high near $174, and that clearing that level could open a new leg higher.11 A Seeking Alpha analysis argues the opposite. It says the top is in, because the fund failed to break its 2021 high, momentum has turned down, the supply of new biotech shares is at cycle highs, and the earlier tailwinds have weakened.1213

The most useful explanation comes from investor Kevin Mak, who sees mechanics at work rather than a change in fundamentals. He links much of XBI's roughly 40% January-to-August gain to Big Pharma acquisitions. Those deals paid premiums to shareholders, and specialist funds then reinvested the proceeds in other biotech stocks.14 He estimates that about $100 billion in acquisitions of public biotech companies were announced from the first quarter through part of the third.14 When deal announcements slowed in September and a crowded short position in Moderna was squeezed, long/short funds appear to have cut positions on both sides of their books. A Morgan Stanley index of popular longs against popular shorts fell more than 50% while XBI fell only about 10%.14 Mak believes the slowdown in deals is a matter of timing and does not mean the acquisition cycle is over.14

This analysis takes Mak's view. The pullback looks like a positioning problem stacked on top of a pause in dealmaking. Demand from large drugmakers facing patent expirations has not gone away. That matters because it implies the next wave of acquisitions, not a better interest-rate outlook, is what would restart the broader rally.

argenx shows how one trial can sink a stock

argenx was the clearest example of the risk in single-stock biotech. The company is stopping its Phase 3 UNITY study of subcutaneous efgartigimod in Sjögren's disease. An independent data monitoring committee concluded at an interim analysis that the trial could not meet its primary endpoint, which was the change in systemic disease activity on the clinESSDAI scale at Week 48.3234 No new safety problems appeared.35 The company plans to analyze the full dataset after the database is locked.34

On the same day, argenx said FB102, an anti-CD122 antibody it acquired with Forte Biosciences in August, met the primary endpoint of a 126-patient Phase 2 trial in celiac disease. In patients exposed to gluten, the drug produced a statistically significant improvement in the ratio of villus height to crypt depth, a measure of intestinal damage, at day 78 (p=0.0176).3233 FB102 already has FDA Fast Track designation and will move into Phase 3. No medicine is currently approved for celiac disease.3234

Investors cared more about the failure. Shares fell about 18% in Brussels trading.36 Some coverage presented the day as mixed, but other reports said the Phase 2 win does not make up for losing a growth opportunity for argenx's main commercial drug.3531 The market reaction supports the second view. A Phase 3 failure for an approved blockbuster outweighs a Phase 2 success for an earlier-stage drug.

ArriVent BioPharma had a similar setback earlier in the week. Its Phase 3 FURVENT trial of firmonertinib in first-line EGFR exon 20 insertion lung cancer missed its primary endpoint. Median progression-free survival was 11.0 months at the 240mg dose versus 9.5 months for the control arm.27

Deals continue at a smaller scale

Viatris agreed to buy Pacira for $36.50 per share in cash, an equity value of $1.65 billion and a premium of about 45%.4146 Pacira's stock closed at $36.39, just under the offer price.44 Oppenheimer's Les Sulewski called the price "full." He said the trading level shows confidence that the deal will close and little expectation of a rival bid, and that activist pressure on Pacira has been building since November 2025.41 Viatris gets two non-opioid pain drugs: Exparel, for pain after surgery, and Zilretta, for knee osteoarthritis pain. Together they brought in about $746 million in revenue over the twelve months ended June 30.4649 The company will pay mostly with cash on hand and expects the deal to add to its financial guidance metrics right away.42

The deal is a long way from the multibillion-dollar Big Pharma takeovers behind earlier gains. The buyer is a generics company moving into branded drugs, and the target already sells approved products. The size is not the kind that sends large reinvestment flows back into the rest of the sector. That fits Mak's view that the big-ticket deal flow has gone quiet for now.14

Licensing deals are still steady. Biohaven gave Ono Pharmaceutical rights to its IgG degrader portfolio, led by BHV-1300, which is in Phase 3 for Graves' disease. The territory covers Japan, South Korea, Taiwan and ASEAN countries. Biohaven receives $80 million upfront, a possible $20 million milestone within a year, and royalties of about 20%, and it keeps rights in the U.S., Europe and China.30 Glaukos licensed a tri-specific retinal biologic from RevOpsis on the same day.22

Regulatory decisions supply the next catalysts

The FDA accepted BridgeBio's application for oral infigratinib in children with achondroplasia under priority review, with a decision date of February 4, 2027. The Phase 3 PROPEL 3 trial showed an adjusted improvement in annual growth rate of 1.74 cm per year over placebo.24 Competition in this disease is already active. Ascendis' TransCon CNP is approved in the U.S. as Yuviwel, and a European decision is expected in the fourth quarter.29 Vir Biotechnology received Fast Track designation for VIR-5500, a dual-masked T-cell engager for late-line prostate cancer that it is developing with Astellas, with Phase 3 trials planned for 2027.23 Enliven reached agreement with the FDA on the design of a roughly 450-patient Phase 3 trial in chronic myeloid leukemia.27

Companies are also still raising money. Atrium Therapeutics arranged a private placement of about $50 million.22 Smaller companies such as Medicus Pharma say their strategy is to take drugs through Phase 2 and then find a pharma partner.21 This steady supply of new shares is exactly what the Seeking Alpha bear case points to as a headwind.12

What it adds up to

The momentum and stock-ranking screens tell the same story. Over six months, gains among top-ranked names ran from more than 100% at Revolution Medicines and Precigen to a 70% drop at AIM ImmunoTech.2 Technical screens show Pacific Biosciences up about 106% in a month while Caribou Biosciences fell 60%.3 When results are this spread out, owning the index is not a good proxy for owning the sector.

The more convincing reading is that the 2026 biotech rally is resting rather than ending. Patent expirations at large drugmakers have not changed, and licensing deals are still getting done. Even so, until another round of large acquisitions arrives, investors will be rewarded or punished mainly on individual trial readouts and FDA decisions. The argenx drop is a reminder of how costly that can be.