Novartis shares rose after the drugmaker reported positive results from two late-stage trials in the most common form of multiple sclerosis, saying its new pill helped patients experience fewer flare-ups.

Shares in Novartis were up 4.5% in European midday trading Tuesday, taking their year-to-date gain to 18%.

The trial results boost Novartis's hopes to launch a new generation of medicines to replace sales lost when some of its biggest drugs went off patent last year.

The Swiss pharmaceutical company said two trials for relapsing multiple sclerosis met their primary goal by showing its drug, known as remibrutinib and marketed as Rhapsido for the skin condition chronic spontaneous urticaria, reduced relapse rates compared to a rival treatment.

The studies enrolled around 2,000 patients with relapsing multiple sclerosis--the most common form of the disease, in which patients experience new or worsening neurological symptoms--and evaluated Novartis's drug against Sanofi's Aubagio.

Novartis said its drug reduced the annualized relapse rate and inflammatory brain lesions relative to the rival medicine. It also showed a favorable safety profile, the company added.

The results mark a best-case outcome for Novartis and could unlock annual peak sales of $3 billion for the drug in multiple sclerosis alone and potentially top $10 billion across indications, analysts at Bank of America wrote in a note to clients.

Novartis already has in Kesimpta, another multiple sclerosis drug, one of its top-selling medicines.

"Despite advances in treatment, an unmet need remains for oral therapies that can deliver robust relapse prevention, slow disability progression, while maintaining a favorable safety profile," Novartis Chief Medical Officer Shreeram Aradhye said.

Analysts at J.P. Morgan said in a separate note that detailed data would be required to fully assess the drug's efficacy profile relative to Roche's rival oral multiple sclerosis drug candidate fenebrutinib and another class of treatments.

Shares in Roche were down 1.8% in European midday trading.

Novartis said it plans to seek regulatory authorization in relapsing multiple sclerosis globally for the drug, which is already approved in the U.S. and the European Union as a skin treatment.

The company expects to release data for a number of pivotal studies in the coming months that could buoy its prospects over the medium term and help it move past recent patent expirations.

When products such as heart drug Entresto lost patent protection, Novartis's sales took a hit initially, but they returned to growth last quarter driven by continued momentum from other key medicines and recent launches.