The Dow tumbled more than 650 points on Tuesday as renewed Middle East violence sent oil prices surging, but the day’s most dramatic single-stock stories came from a corner of the market that had nothing to do with geopolitics: biotech. A single company’s back-to-back failed drug trials triggered a sympathy selloff that rippled across an entire class of neuromuscular disease therapies, while a Brazilian court ruling, a healthcare-conference disclosure, and a disappointing guidance midpoint rounded out one of the more brutal single-session lists of the month. Here are the 10 stocks that had the worst day in the market today.

Tuesday’s Broader Market Context:

Healthcare’s more-than-2% sector decline was the single biggest driver of today’s losers list, but manufacturing troubles, legal rulings, and disappointing guidance all made appearances too.

1. Dyne Therapeutics (DYN) | Down 22%

Collateral Damage From a Rival’s Failed Trial

Dyne Therapeutics shares tumbled 22% after Novartis announced its del-desiran drug for myotonic dystrophy type 1 (DM1) failed to meet its primary endpoint in a late-stage study — a result investors immediately extrapolated to Dyne’s own pipeline given the mechanistic overlap between the two companies’ approaches.

Full Data & Technical Snapshot:

Why It Tanked:

Novartis’s global Phase 3 HARBOR study evaluating del-desiran did not demonstrate statistically significant improvement over placebo on its primary endpoint of video hand opening time, a novel measure of hand myotonia in DM1 patients. Because Dyne’s z-basivarsen targets the same toxic DMPK RNA implicated in the disease — even though it uses a different delivery ligand — investors treated today’s failure as a meaningful read-through risk for Dyne’s own DM1 program, despite the different targeting mechanism.

Bull Case: The differentiated αvβ6-integrin-targeting ligand mechanism means Dyne’s approach is not identical to Novartis’s failed TfR1-based drug, and today’s selloff may prove to be an overreaction if Dyne’s own trial data — expected separately — eventually demonstrates the differentiated delivery mechanism translates into better clinical outcomes.

Bear Case: DM1 is a notoriously difficult indication, and a second consecutive high-profile failure in the same broad mechanistic class (targeting DMPK RNA via siRNA) would raise serious questions about whether the entire therapeutic approach, not just one company’s specific ligand choice, is fundamentally flawed for this disease.

Technicals: Today’s 22% drop is among the largest single-day moves for Dyne in recent memory, reflecting how severely a single competitor’s data readout can move an entire therapeutic category.

Forecast: Dyne’s own DM1 trial data, whenever it reads out, now carries dramatically higher stakes — the market has already priced in meaningful skepticism following today’s sympathy selloff.

Why This Matters: Dyne’s collateral damage from a rival’s failed trial is a textbook example of how tightly biotech investors link companies pursuing similar disease mechanisms — even when the actual drugs work through meaningfully different pathways.

2. Novartis (NVS) | Down 12%

Two Failed Trials in One Day

Novartis shares fell 12% after the pharmaceutical giant reported not one but two failed late-stage drug trials on the same day — its del-desiran drug for myotonic dystrophy failed to meet its primary endpoint, and separately, its experimental drug pelacarsen did not reduce the risk of major heart attacks and strokes despite successfully lowering a dangerous genetic cholesterol marker.

Full Data & Technical Snapshot:

Why It Tanked:

Pelacarsen’s failure is particularly significant for the broader industry because it successfully lowered lipoprotein(a) — a genetic cholesterol risk factor — but this biomarker reduction did not translate into fewer heart attacks or strokes, raising fundamental questions about whether Lp(a)-lowering as a therapeutic strategy actually improves patient outcomes at all, a question with implications far beyond Novartis’s own pipeline.

Bull Case: Two failures on the same day is a statistically unusual and painful coincidence rather than evidence of a systemic problem with Novartis’s broader R&D engine, which still includes numerous other approved products and pipeline assets unaffected by today’s news.

Bear Case: The pelacarsen result specifically undermines the entire Lp(a)-lowering therapeutic hypothesis that multiple companies (including Amgen’s olpasiran) are pursuing, meaning today’s damage may extend well beyond Novartis’s own stock into the broader lipid-lowering drug development space.

Technicals: A 12% single-day decline in a large, typically lower-volatility pharmaceutical stock reflects the market’s assessment that today’s news materially changes the near-term pipeline value, not just short-term sentiment.

Forecast: Expect continued scrutiny of any other Lp(a)-targeting or DMPK-targeting programs across the industry as investors reassess the read-through risk from today’s dual failures.

Why This Matters: Novartis’s rare double trial failure on a single day sent shockwaves through two entirely separate therapeutic areas simultaneously, demonstrating how a single company’s bad day can reshape investor sentiment across an entire sector.

3. Sigma Lithium (SGML) | Down 11%

A Brazilian Court Ruling Halts Mining Operations

Sigma Lithium shares fell 11% after a Brazilian court ordered the suspension of environmental licenses and mining activities at the company’s Grota do Cirilo mine, ruling that the project falls within the direct area of influence of the Bau Quilombola community.

Full Data & Technical Snapshot:

Why It Tanked:

The court ruling directly threatens Sigma Lithium’s primary operating asset, and any suspension of active mining licenses at Grota do Cirilo would immediately impact the company’s ability to generate revenue from its core lithium production operations — a direct, quantifiable operational risk rather than a sentiment-driven selloff.

Bull Case: Legal rulings of this nature are frequently appealed or narrowed in scope, and Sigma Lithium’s underlying reserve base and lithium demand fundamentals (tied to global EV battery supply chains) remain unaffected by the specific licensing dispute.

Bear Case: Community-rights-based legal challenges to mining operations in Brazil have a track record of extending for years through the court system, and any prolonged suspension could materially impair Sigma Lithium’s production capacity and revenue guidance for multiple quarters.

Technicals: An 11% single-day decline on a specific legal catalyst represents a sharp repricing of operational risk rather than a broader sector rotation, as lithium peers were not uniformly affected by today’s news.

Forecast: The pace and outcome of any appeal process will be the single biggest determinant of Sigma Lithium’s near-term trajectory — investors should watch for updates on the legal timeline in the coming weeks.

Why This Matters: Sigma Lithium’s legal setback is a reminder that critical minerals producers face genuine, sometimes unpredictable regulatory and community-rights risk that can materially disrupt operations with little advance warning.

4. Sarepta Therapeutics (SRPT) | Closed $20.18, Down 10.3%

Another Casualty of the DMPK Mechanism Scare

Sarepta Therapeutics shares plunged 10.3% to $20.18 as part of the same sympathy selloff hitting Dyne Therapeutics, after Novartis’s del-desiran trial failure raised concerns about siRNA-based approaches to myotonic dystrophy type 1 more broadly.

Full Data & Technical Snapshot:

Why It Tanked: Sarepta’s SRP-1003 program targets the same toxic DMPK RNA implicated in myotonic dystrophy, using an αvβ6-integrin-targeting ligand rather than the TfR1 mechanism that failed in Novartis’s trial — but today’s selloff shows investors are treating the entire DMPK-targeting therapeutic class with heightened skepticism regardless of specific delivery mechanism differences. This adds to an already challenging backdrop for Sarepta, which has been navigating tightened 2026 revenue guidance and ongoing regulatory uncertainty around its core Duchenne muscular dystrophy franchise.

Bull Case: Sarepta’s differentiated ligand technology means its approach to DM1 is mechanistically distinct from Novartis’s failed drug, and the company’s existing commercial Duchenne muscular dystrophy franchise provides a revenue base independent of the DM1 pipeline entirely.

Bear Case: Sarepta was already navigating regulatory uncertainty and tightened guidance before today’s news, meaning this sympathy selloff compounds an existing period of investor skepticism rather than occurring in isolation.

Technicals: Shares are now trading well below the middle of their 52-week range, with today’s move representing one of the larger single-day declines for the stock outside of company-specific negative catalysts.

Forecast: Sarepta’s own DM1 data, whenever it reads out, will need to convincingly demonstrate mechanistic differentiation from the failed Novartis approach to reverse today’s sympathy-driven pressure.

Why This Matters: Sarepta’s decline alongside Dyne shows just how correlated the entire DMPK-targeting therapeutic space has become — a single trial failure at one company can erase value across several unrelated competitors simultaneously.

5. Amgen (AMGN) | Down ~9%

A Downgrade Collides With a Competitor’s Cholesterol Drug Failure

Amgen shares dropped roughly 9% after BMO Capital downgraded the stock to Market Perform citing valuation concerns, on the same day Novartis’s pelacarsen trial failure raised fresh questions about Amgen’s own experimental cholesterol drug olpasiran.

Full Data & Technical Snapshot:

Why It Tanked: BMO’s downgrade specifically noted that Amgen’s “commercial execution is now the base case” after the stock’s strong 34% year-to-date run, suggesting limited further upside from current levels — but the bigger story was Novartis’s pelacarsen result, which lowered the same Lp(a) cholesterol marker that Amgen’s olpasiran targets, without producing a cardiovascular benefit, raising the possibility that Amgen’s own late-stage asset could face a similar disappointing outcome.

Bull Case: Olpasiran’s specific trial design and patient population may differ meaningfully from Novartis’s pelacarsen study, and Amgen’s broader commercial portfolio provides diversification well beyond any single pipeline asset’s outcome.

Bear Case: If the entire Lp(a)-lowering therapeutic hypothesis is flawed — as Novartis’s result suggests — then Amgen’s olpasiran program faces the same fundamental risk regardless of specific trial design differences, representing a potentially significant pipeline value impairment.

Technicals: Today’s decline erases a meaningful portion of Amgen’s strong 2026 gains, testing whether the stock’s uptrend remains intact after the double hit of a valuation-based downgrade and a competitor’s negative read-through.

Forecast: Investors will be watching closely for any Amgen commentary on how olpasiran’s trial design might differ from Novartis’s failed approach — a clear differentiation argument could help stabilize sentiment.

Why This Matters: Amgen’s decline shows how a single competitor’s trial failure can simultaneously validate a valuation-based downgrade thesis, compounding two negative catalysts into one outsized single-day move.

6. Stryker Corporation (SYK) | Down 8.1%

Manufacturing Problems That Won’t Go Away

Stryker shares fell as much as 8.1% to $278.71 after company executives disclosed at the Wells Fargo Healthcare Conference that ongoing manufacturing issues in its peripheral vascular business would continue into the fourth quarter, extending problems the company had previously expected to resolve by the third quarter.

Full Data & Technical Snapshot:

Why It Tanked: CFO Preston Wells told conference attendees that manufacturing problems continue to prevent Stryker from maintaining full inventory supply to customers, limiting the company’s ability to win new business, while separately noting that joint replacement sales trends have not shown the seasonal recovery management had expected earlier in the year — a rare mid-quarter negative update outside of a formal earnings report.

Bull Case: Stryker management expects the peripheral vascular supply issue to be substantially resolved by year-end, and the company’s broader medical technology portfolio (orthopaedics, neurotechnology, MedSurg) provides diversification against a single segment’s temporary manufacturing constraints.

Bear Case: This is now the second consecutive quarter management has pushed back its resolution timeline for the peripheral vascular supply problem, raising credibility concerns about whether the issue is truly temporary, and the stock is already down 21% year-to-date heading into today’s additional decline.

Technicals: Today’s drop adds meaningfully to an already weak 2026 technical picture, with shares now well below their 52-week highs and testing lower support levels established earlier in the year.

Forecast: Investors should watch Stryker’s next formal earnings report closely for confirmation of whether the peripheral vascular supply issue is genuinely resolving or continuing to slip — a further delay would likely compound today’s damage.

Why This Matters: Stryker’s mid-quarter conference disclosure — rather than a formal earnings miss — shows how unscheduled management commentary can move a stock nearly as much as a full quarterly report when it contradicts previous guidance.

7. UiPath (PATH) | Closed $14.05, Down 7.5%

A Beat That Still Wasn’t Convincing Enough on AI

UiPath shares fell 7.5% to close at $14.05 despite a wave of price-target increases from Wall Street analysts, after the automation software company’s fiscal third-quarter revenue guidance midpoint missed consensus expectations even as Q2 results beat estimates.

Full Data & Technical Snapshot:

Why It Tanked: Despite the headline revenue beat, net new ARR of $37 million represented a sequential step down from the $49 million added in the prior quarter — a closely watched leading indicator of future subscription momentum — and management faced pointed analyst questions about the timeline for AI revenue to meaningfully accelerate growth, with Barclays, Truist, BMO, and several other firms raising price targets while simultaneously maintaining cautious Hold or Equal-Weight ratings, signaling limited conviction despite improved numbers.

Bull Case: 18 of the company’s top 20 deals in the quarter included AI components, evidence that UiPath’s platform consolidation and outcome-based sales strategy is gaining real traction even if the revenue impact hasn’t fully materialized yet.

Bear Case: A slowing net-new-ARR trend is historically one of the most reliable early warning signs of decelerating future growth in subscription software businesses, and the chorus of analysts raising targets while keeping neutral ratings suggests genuine uncertainty rather than a clear buy signal.

Technicals: Today’s decline, following a string of similarly sized post-earnings drops earlier in the year, reflects a stock that has struggled to sustain rallies even on fundamentally solid quarters.

Forecast: The next quarter’s net-new-ARR trend will be the critical data point determining whether today’s slowdown was a one-quarter blip or the start of a more troubling deceleration pattern.

Why This Matters: UiPath’s inability to rally on a genuine revenue beat — with net new ARR as the specific culprit — shows how granular metrics beyond simple top-line numbers now drive stock reactions in the software sector.

8. Shift4 Payments (FOUR) | Down 7.4%

Caught in a Broad Fintech and Payments Selloff

Shift4 Payments shares fell 7.4% amid sector-wide selling that also hit other consumer-facing payments and e-commerce names including Etsy and Expedia Group, both down 5.5% on the same day, as investors broadly rotated out of consumer discretionary and payments-adjacent stocks.

Full Data & Technical Snapshot:

Why It Tanked: Today’s decline appears tied to broader sector rotation rather than a single Shift4-specific news catalyst, with payments processors and consumer-facing platform companies broadly under pressure as rising oil prices and Treasury yields raised concerns about discretionary consumer spending resilience heading into the back half of 2026.

Bull Case: Without a specific negative company catalyst, today’s decline may represent an overreaction to broader macro sentiment rather than any change in Shift4’s underlying payment-volume growth trajectory or competitive positioning.

Bear Case: Sector-wide selloffs in payments and fintech names often reflect genuine investor concern about consumer spending deceleration, which would directly impact transaction-volume-based revenue models like Shift4’s regardless of company-specific execution.

Technicals: A 7.4% single-day move without a clear individual catalyst suggests high sensitivity to macro sentiment shifts, a pattern common among high-beta payments and fintech names.

Forecast: With no company-specific news driving today’s decline, Shift4’s near-term trajectory will likely track broader consumer discretionary sector sentiment rather than any internal catalyst until its next earnings report.

Why This Matters: Shift4’s decline alongside Etsy and Expedia on the same day illustrates how quickly sentiment-driven sector rotations can hit an entire cohort of consumer-transaction-dependent stocks simultaneously, even without individual bad news.

9. Bombardier (BDRBF) | Down 5%

A Presidential Social Media Post Rattles an Aircraft Maker

Bombardier shares fell 5% after President Trump stated in a social media post that the Canadian aerospace company’s aircraft should no longer be sold in the U.S. unless it begins manufacturing domestically, injecting sudden political and trade-policy risk into the stock.

Full Data & Technical Snapshot:

Why It Tanked: A direct presidential statement threatening to restrict a major manufacturer’s access to the U.S. market — one of its largest business jet markets globally — represents a serious, credible policy risk that investors have to take seriously given the administration’s demonstrated willingness to follow through on similar threats against other companies this year, including the earlier action against Polestar’s U.S. market access.

Bull Case: Social media statements don’t carry the same binding legal weight as formal policy action, and Bombardier has a substantial non-U.S. customer base globally that would cushion the impact of any eventual U.S. market restrictions.

Bear Case: The administration has already demonstrated a willingness to follow through on similar threats against foreign-linked manufacturers this year, and any formal U.S. market restriction would be a severe blow to Bombardier’s largest addressable market for business jets.

Technicals: Today’s decline is a sudden, headline-driven move rather than a technically-driven breakdown, meaning the stock’s next move depends almost entirely on whether the administration follows through with formal policy action.

Forecast: Watch for any official Commerce Department or trade policy statements in the coming days or weeks — a formal restriction proposal would likely extend today’s selling, while a walked-back or clarified statement could quickly reverse the damage.

Why This Matters: Bombardier’s decline is the latest example this year of a single presidential statement creating immediate, material stock price risk for foreign manufacturers — a pattern investors in globally-exposed industrial names now have to actively monitor.

10. Boston Scientific (BSX) | Down 2%

A Cybersecurity Incident Forces a Guidance Warning

Boston Scientific shares fell after the medical device maker said it is “unlikely” to meet its net sales and adjusted EPS guidance, following an August 25 cybersecurity incident that caused a global disruption to the company’s operations.

Full Data & Technical Snapshot:

Why It Tanked: A cybersecurity incident disrupting global operations for nearly two weeks is a serious operational event for a medical device manufacturer, where supply chain continuity and regulatory compliance depend heavily on functioning IT systems — the company’s explicit admission that it will likely miss financial guidance as a direct result signals the disruption was more than a minor, quickly-resolved technical issue.

Bull Case: Cybersecurity incidents, while disruptive, are typically resolved within weeks to months rather than representing a permanent impairment to a company’s operations, and Boston Scientific’s underlying medical device demand and product pipeline remain unaffected by the IT disruption itself.

Bear Case: The company’s explicit warning that it’s “unlikely” to hit guidance — rather than reaffirming targets — suggests the operational impact was significant enough to materially affect this quarter’s results, and any lingering data security or systems issues could create ongoing operational and reputational risk.

Technicals: Today’s relatively modest 2% decline, smaller than other names on this list, suggests the market views this as a contained, quantifiable near-term disruption rather than an existential threat to the business.

Forecast: Investors should watch for a formal update on the cybersecurity incident’s full financial impact and resolution timeline, likely to come with Boston Scientific’s next quarterly report.

Why This Matters: Boston Scientific’s guidance warning is a reminder that cybersecurity risk has become a genuine, quantifiable financial threat for large healthcare manufacturers — not just a reputational or data-privacy concern.

Sector Sentiment Snapshot & Forecast

Today’s losers list was overwhelmingly dominated by one theme: biotech contagion from Novartis’s rare double trial failure. Dyne Therapeutics, Sarepta, Amgen, and Novartis itself all fell in a coordinated sympathy selloff that shows just how tightly correlated companies pursuing similar drug mechanisms (DMPK-targeting siRNA therapies, Lp(a)-lowering cholesterol drugs) have become in investors’ minds — a single failed trial at one company can erase billions in market value across several unrelated competitors within hours.

Separately, medical device and healthcare names faced their own distinct pressures (Stryker’s manufacturing issues, Boston Scientific’s cybersecurity disruption). Showing operational and cybersecurity risk is a growing, quantifiable concern in the sector independent of clinical trial outcomes. Software and fintech names (UiPath, Shift4) show that even genuine beats aren’t enough when a single leading indicator metric disappoints, while Bombardier’s political risk and Sigma Lithium’s legal setback round out a day where company-specific and policy-driven catalysts dominated over broad macro themes.

Healthcare’s down more than 2% as the day’s worst-performing sector. And the DMPK/Lp(a) mechanism concerns likely to persist into upcoming earnings season. Expect continued volatility in biotech names with any mechanistic overlap to today’s failed Novartis trials.

At a Glance: Today’s Top 10 Losing Stocks

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Disclaimer: This publication is entirely for informational and journalistic purposes and does not constitute formal financial, investment, or legal advice. All market investments carry inherent risks of capital loss, and clinical-stage biotech stocks carry elevated risk. Stock prices, percentage moves, and market data cited reflect figures available at the time of publication and are subject to change. Some prices in this article are approximate, as exact closing figures for certain names were not available at the time of writing. Analyst price targets and ratings are third-party estimates and do not guarantee actual results. Always complete independent due diligence prior to executing equity trades.

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Kasia Davis

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