Novartis released a mixed bag of clinical updates, pausing trials for one drug after a spate of patient deaths while simultaneously revealing positive data for a pill that analysts view as a potential blockbuster.

The Swiss drugmaker said it had halted trials for its experimental cell therapy rapcabtagene autoleucel, or rap-cel, in patients with certain autoimmune diseases.

The decision followed three deaths, which the drugmaker linked to immune effector cell-associated hemophagocytic syndrome, a rare reaction in which the immune system attacks the body's own organs. Novartis confirmed it paused trials in patients with lupus, myasthenia gravis, multiple sclerosis, and other autoimmune diseases on Aug. 24, as it reviews the safety events.

The news failed to dent shares, which was to be expected. Analysts had been cautious about rap-cel's market potential, forecasting under $650 million in revenue in 2032. A drug must generate $1 billion or more annually in order to be considered a blockbuster.

Rather, Novartis stock was heading for its best day in three years in U.S. trading Tuesday, jumping 4.3% to $158.59 in the premarket session. Shares rose nearly as much in Zürich.

Those gains came on the back of an update for the drugmaker's experimental pill for multiple sclerosis, remibrutinib. Patients taking the pill had fewer relapses and brain lesions than those given Sanofi Genzyme's teriflunomide in a Phase III trial.

While rap-cel isn't expected to be a blockbuster, analysts hold higher hopes for remibrutinib. Jefferies analyst Michael Leuchten believes consensus estimates are "likely too conservative," arguing that opportunities across other clinical trials could transform it into a franchise generating high single-digit billions in sales.

Remibrutinib has the potential to achieve "multi-blockbuster status" and outperform Sanofi's rival drug, according to Morgan Stanley's Thibault Boutherin. That being said, Boutherin acknowledged that its commercial success ultimately hinges on how well the pill holds up against existing oral treatments.

The pill would serve as a follow-on to Kesimpta, Novartis's blockbuster monthly injection that treats relapsing forms of multiple sclerosis. Remibrutinib's success would also strengthen the case for a class of drugs known as BTK inhibitors, which blocking an enzyme called Bruton's tyrosine kinase to prevent abnormal white blood cells from growing. Similar medications from Merck and Sanofi have failed to outperform teriflunomide in late-stage trials.