USA – The FDA has expanded approval of Roche’s spinal muscular atrophy (SMA) drug Evrysdi to include infants younger than 2 months old, providing an oral alternative to a gene therapy from Novartis and a drug from Biogen.

SMA is caused by a mutation in the survival motor neuron -1 (SMN1) gene, which codes for a protein essential for the health of motor neurons. Muscle weakness worsens as the disease progresses.

Babies begin to miss important developmental milestones, such as the ability to sit up and roll over. Patients may require breathing assistance as the disease progresses.

Evrysdi is a small molecule that stimulates the survival motor neuron-2 (SMN2) gene to produce more of a key motor neuron protein in the central nervous system and peripheral tissues.

The expanded approval allows doctors to use Evrysdi in babies who have a disorder identified by newborn screening tests.

After one year of treatment, all six babies could sit without assistance, while four could stand and three could walk, according to a small trial of six babies.

Evrysdi, which was developed by PTC Therapeutics and licensed to Roche/Genentech, is one of three drugs available for SMA.

Evrysdi was the last of the three SMA drugs approved in the United States, but its use has steadily increased since its release in 2020.

Spinraza is the top seller, with US$473 million in sales in the first quarter of 2022, followed by Zolgensma at US$363 million and Evrysdi at around US$236 million.

Limited options for infants

Before Tuesday’s approval, Spinraza and Zolgensma were the only options for infants younger than 2 months.

The new approval will allow Roche to compete more effectively with Novartis and its gene therapy Zolgensma, which is frequently administered shortly after birth, as well as Biogen’s drug Spinraza.

With an estimated incidence of SMA of one in every 10,000 births, the three drugmakers are all focusing their treatments on a small group of patients.

While Evrysdi is taken orally and thus more conveniently, it must be taken every day. Spinraza, on the other hand, is given once every four months after a two-month loading period via the more invasive intrathecal injection.

Zolgensma is intended to be a one-time treatment, but given the uncertainty surrounding gene therapy’s long-term safety, some parents may be wary of using it on their children.

When the two Swiss pharmaceutical companies reported earnings, Novartis said Zolgensma had been used in about 2,000 patients worldwide, while Roche said Evrysdi had been used in over 5,000. (However, Roche’s figure includes those treated in clinical trials and on compassionate grounds.)

Sales of both Zolgensma and Evrysdi are increasing, seemingly at the expense of Spinraza, whose sales fell by 9% in the first quarter compared to the same period last year.

With all three drugs now approved for use in the smallest infants and two of the three more widely available, the question of how these treatments might be used in sequence has arisen.

However, all three are expensive: The one-dose list price for Zolgensma is around US$2 million, while Spinraza costs US$375,000 per year at the maintenance dose and Evrysdi costs US$340,000 per year.

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