Amgen (AMGN) Stock Falls 10%, Worst Drop Since 2000 - It Was Novartis's Trial That Failed, So Why Did Amgen Get Hit Hardest?

What Happened

On Tuesday, September 8, shares of Amgen (Nasdaq: AMGN) fell roughly 10% to close at $393.17, down $44.06 from the prior session, on trading volume nearly three times its one-month average. It was the steepest single-day decline for the stock since October 2000. The move was large enough to matter well beyond Amgen itself: the Dow Jones Industrial Average dropped 628 points (1.18%) that day, and because the Dow is a price-weighted index - where higher-priced stocks move the average more than cheaper ones regardless of company size - a nearly $400 stock cratering 10% accounted for a meaningful chunk of the index's decline all on its own.

Here's the strange part: Amgen didn't announce anything bad that day. No disappointing earnings, no regulatory rejection, no failed trial of its own. The trigger came four days earlier, on September 4, when Swiss pharma giant Novartis and biotech partner Ionis Pharmaceuticals jointly announced results from their Phase 3 Lp(a)HORIZON trial. Their cardiovascular drug pelacarsen had missed its primary endpoint. The study enrolled 8,323 patients with elevated lipoprotein(a), or Lp(a) - a genetically determined, cholesterol-like particle linked to heart disease risk - and existing cardiovascular disease, all already on standard-of-care treatment. Adding pelacarsen was supposed to reduce a composite of cardiovascular death, heart attack, stroke, and urgent coronary revascularization compared to placebo. The drug succeeded at lowering Lp(a) levels substantially. It failed to translate that biomarker improvement into a statistically significant reduction in actual cardiovascular events. Safety was clean.

On announcement day, Ionis - the biotech that originally discovered pelacarsen and licensed it to Novartis - fell 13.1% in premarket trading to $50.51, a direct hit for the company whose own drug had just failed. Novartis, which sponsored the trial, also declined that day. But the biggest casualty in dollar and percentage terms wasn't either of them - it was Amgen, a company with no contractual relationship to the trial at all, and the blow didn't even land until four days later, once Wall Street's re-rating of the entire drug class had fully caught up. That same day, BMO Capital downgraded Amgen to Market Perform, and Barclays analyst Emily Field put it bluntly: "This is the worst possible outcome for Amgen."

Why the Company With No News of Its Own Got Hit the Hardest

The key to understanding this is that Amgen has its own Lp(a)-lowering drug candidate in late-stage development: olpasiran, currently in the Phase 3 OCEAN(a)-Outcomes trial. Olpasiran has not yet reported its own hard-outcomes data - there is no evidence it has failed anything. What the market reacted to wasn't Amgen's data. It was what Novartis and Ionis's data implied about the underlying scientific premise both drugs share.

Pelacarsen and olpasiran work through different chemistry: pelacarsen is an antisense oligonucleotide (ASO), while olpasiran is a small interfering RNA (siRNA) therapy. But both are built around the same biological target - lowering Lp(a) levels. The unsettling message from the Lp(a)HORIZON trial wasn't "this particular molecule doesn't lower Lp(a) well enough." It was a much bigger question: does lowering Lp(a) at all actually prevent heart attacks and strokes? Pelacarsen proved it could hit the biomarker target and still fail on real clinical outcomes - suggesting the problem may lie with the therapeutic hypothesis itself, not with any single drug's chemistry. That doubt doesn't respect drug-class boundaries. However well olpasiran lowers Lp(a), the trial raised a fair question about whether that reduction will ever show up as fewer heart attacks in Amgen's own outcomes data. CNBC and other outlets noted the same skepticism has spread to Eli Lilly's competing Lp(a) program, lepodisiran, reinforcing that this is being treated as a class-wide re-rating rather than a Novartis-specific problem.

The timing gap is itself instructive. Ionis and Novartis were judged immediately, on announcement day, because the bad news was directly theirs. Amgen's reckoning took four days, as analysts and desks worked through what a rival's failure implied for a company that hadn't reported anything yet. BMO's downgrade and Barclays' blunt commentary were part of that delayed digestion process, and by the time it landed, it hit Amgen harder in percentage terms than it hit either company whose drug actually failed. Amgen also wasn't starting from a position of strength: UK regulators had suspended new prescriptions of its autoimmune drug Tavneos just days earlier, adding to a stretch of pipeline-related pressure that likely made investors quicker to sell on the Lp(a) news.

What to Take Away From This

• A biomarker win is not the same as a clinical outcomes win. Pelacarsen lowered Lp(a) substantially but still failed to reduce actual cardiovascular events. When evaluating binary trial catalysts, always check whether the endpoint that succeeded (or failed) is a surrogate marker or a hard clinical outcome - the gap between the two is where a lot of stock-moving surprises live.
• You can get hit by "read-through risk" even when your own holding has no bad news at all. Amgen's olpasiran hasn't failed anything, yet the stock absorbed the market's biggest single-day loss because a competitor's unrelated trial cast doubt on the shared biological target. Owning multiple names in the same therapeutic theme doesn't fully diversify away this kind of correlated risk.
• A quiet reaction on announcement day doesn't mean the story is over. Ionis and Novartis moved immediately; Amgen's real drop came four days later once analyst re-ratings caught up. After a major trial readout in any therapeutic class, it's worth tracking follow-on analyst notes and rating changes for several days, not just the headline reaction.
• Understanding index construction changes how you read headline moves. Amgen's roughly $400 share price meant its 10% drop disproportionately dragged down the price-weighted Dow, a dynamic that wouldn't play out the same way in a market-cap-weighted index like the S&P 500.
• Same-day analyst rating changes are a useful real-time signal of how professional money is digesting new information. No single downgrade should drive a decision on its own, but when multiple desks move in the same direction on the same day, that convergence is itself a data point worth weighing.

FAQ

Did Amgen's own drug, olpasiran, fail in this trial?

No. The trial that missed its endpoint tested Novartis and Ionis's pelacarsen. Amgen's olpasiran has not yet reported final Phase 3 outcomes data from its OCEAN(a)-Outcomes trial. Amgen's stock dropped because the pelacarsen failure raised broader doubts about the entire Lp(a)-lowering drug class, not because of anything specific to Amgen's own pipeline.

What's the actual difference between pelacarsen and olpasiran?

Both aim to lower Lp(a) levels, but they use different drug technologies. Pelacarsen is an antisense oligonucleotide (ASO); olpasiran is a small interfering RNA (siRNA) therapy. Because they target the same underlying biology despite different chemistry, doubts about whether lowering Lp(a) actually helps patients apply to both.

Does this mean Lp(a)-lowering drugs are a dead investment thesis?

It's too early to say. Pelacarsen clearly demonstrated it can lower Lp(a) safely - the problem was that the biomarker improvement didn't translate into fewer cardiovascular events. Whether Amgen's differently-designed olpasiran can break that pattern is something only its own outcomes data can answer, and until then, the market appears to be pricing in that uncertainty as a discount across the whole class.

Related reading: Moderna Stock Doubles in a Day on mRNA Melanoma Vaccine Trial Success, Target vs. Lowe's: Same-Day Earnings, Opposite Stock Reactions

Sources

This article is an original synthesis and analysis based on the reporting below, not a reproduction of the original articles. Please check the source articles directly for the most current figures.

• Amgen Falls 10% as Novartis Trial Failure Clouds a Cholesterol Drug Class; NVS Stock Drops - Yahoo Finance
• Novartis trial failure raises stakes for Amgen and Eli Lilly in Lp(a) drug race - CNBC
• Ionis partner Novartis announces Lp(a)HORIZON Phase 3 topline results for pelacarsen - Ionis Pharmaceuticals (official release)

⚠️ This article is for informational purposes only and is not investment advice. Market conditions change constantly - always verify the latest data before making investment decisions.