ZURICH: Swiss drugmaker Roche on Monday said two-thirds of spinal muscular atrophy (SMA) patients now taking its newly approved drug Evrysdi have previously received rival treatments Zolgensma from Novartis or Biogen's Spinraza.

With now three drugs on the market in the last five years, SMA has become a very competitive, potentially very lucrative market.

Spinraza lists at $750,000 for the first year and $375,000 annually thereafter. Gene therapy Zolgensma at $2.1 million is the costliest one-time treatment, while Evrysdi, also called risdiplam, costs up to $340,000 per year.

Many analysts see Zolgensma as the option of choice, in particular for newborn babies diagnosed with SMA, since it is given by infusion a single time.

Spinraza, Biogen's $2 billion per year seller that must be administered via spinal infusion about once every four months, may face more direct competition from Roche's drug, which as a once-daily oral may have more convenient administration, analysts have said.

"We see patients with all types of SMA," Teresa Graham, Roche's head of pharma global product strategy, said on a call with investors about initial Evrysdi sales. "About 25% of patients have type 1 SMA...with about two-thirds of patients having prior experience with Spinraza or Zolgensma."

Evrysdi was approved last month. Roche, which partnered with PTC Therapeutics on the medicine, will likely give an update on initial Evrysdi sales in October.