Ionis Lost Its Biggest Bet on Heart Disease — Can Its Remaining Pipeline Justify the Stock?

Shares of Ionis Pharmaceuticals continued their slide Monday, trading at $53.73 — down 7.5% on the day and roughly 37% below their ~$86 level before the July 9 disclosure that its flagship heart-disease drug eplontersen had failed its pivotal trial. The drop can be traced back to eplontersen failing to prove its efficacy in ATTR-CM, a rare but fatal condition where misfolded proteins damage the heart. With broader markets only modestly lower, the stock's persistent weakness signals investors are still repricing what this loss means.

• The Drug Worked on Paper but Not Where It Counted. Among 1,432 patients tested over 140 weeks, eplontersen failed to significantly reduce cardiovascular deaths or recurrent heart events versus placebo (rate ratio 0.89; P = .277).

This happened despite a 60% reduction in the toxic protein the drug targets — meaning the biological mechanism fired but patient outcomes didn't improve. A majority of trial participants were already taking a stabilizer drug, and adding eplontersen on top showed no statistically significant benefit. That trial design flaw — or reality check — leaves the drug's future in ATTR-CM in serious doubt.

• Rivals Are the Clear Winners. The failure removes a potential competitor to ATTR-CM drugs from Pfizer, BridgeBio, and Alnylam, whose positions in the market look stronger after the miss.

Pfizer's market-leading tafamidis franchise eclipsed $6 billion in sales last year.

Shares of Alnylam and BridgeBio surged by double digits on the news , a mirror image of Ionis's pain. Analysts note eplontersen's path to regulatory approval in this condition now looks essentially closed.

• Management Says the Rest of the Business Is Fine — for Now. Despite the trial miss, management reaffirmed its full-year 2026 revenue projection of $875 million to $900 million, with other drugs leading sales forecasts.

But Q2 results showed a $0.70 loss per share and revenue down 41% from a year earlier , underscoring Ionis's dependence on lumpy partnership payments rather than steady product sales.

• A $92 Fair Value Versus a $54 Stock Price Tells a Complicated Story. Analysts have cut their fair-value estimate from roughly $105 to $92 , yet the stock trades far below even that reduced target. Today, Citi and others reiterated Buy ratings near $100 , implying Wall Street sees an overreaction. But Ionis fell 21% on the initial news and has kept sinking — a sign that confidence in the broader RNA pipeline now carries a steeper risk premium. The question isn't whether Ionis has other drugs. It's whether any of them can fill a multibillion-dollar hole.