Why is Amgen stock sliding today?

Amgen shares dropped 4.7% in pre-market trading today after a closely watched Phase III cardiovascular trial failure at Novartis shook investor confidence in the broader Lp(a)-lowering drug class, directly threatening the perceived commercial value of Amgen's own pipeline candidate. On September 4, Novartis said that pelacarsen — a drug designed to sharply reduce lipoprotein(a), a lipid particle linked to higher heart disease risk — failed to cut cardiovascular death, heart attacks, or strokes versus placebo in its pivotal Phase III study, even though it successfully lowered Lp(a) levels in treated patients. The result is especially significant for Amgen, which is developing olpasiran, an investigational siRNA therapy aimed at reducing Lp(a) synthesis in the liver, currently being evaluated in the Phase III OCEAN(a)-Outcomes study.

Adding to the selling pressure, BMO Capital issued a downgrade on Amgen today, moving the stock to Market Perform from Outperform while keeping a $450 price target. The downgrade was driven by the stock's roughly 34% year-to-date gain, which significantly outperformed both the S&P 500 and the drug sector, implying that commercial execution is now effectively baked in as the base case. BMO also flagged meaningful loss-of-exclusivity headwinds as a risk that requires further assessment before a more constructive stance could be justified.

The Novartis setback raises uncertainty for rival experimental Lp(a) drugs from Amgen and Eli Lilly, though analysts note the failure weakens — but does not disprove — the broader scientific case for targeting this form of harmful cholesterol. Olpasiran uses a different drug design and may target a different patient population, so pelacarsen's failure does not directly predict Amgen's result, but it strips away easy assumptions investors may have made about the commercial value of dramatic Lp(a) reductions. Against this backdrop, the broader U.S. equity market is also modestly under pressure, with the S&P 500 off 0.3% and the Dow Jones down 0.8%, providing a mildly negative macro tailwind to the sector-specific selloff.

The combination of a competitor's high-profile clinical failure raising class-wide doubts, a fresh valuation-driven analyst downgrade, and a softening broader market converged to push Amgen shares to $416.88 in pre-market trading — well below its 52-week high of $447.03 reached just weeks ago. The stock's next major test will be the readout of its own OCEAN(a)-Outcomes trial, which now carries heightened scrutiny from investors demanding proof that lowering Lp(a) translates into meaningful reductions in cardiovascular events.

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