A chemical once used to treat sofas — until it was found to cause rashes and blisters in people who sat on them — is now poised to become a major therapy for multiple sclerosis.

The Food and Drug Administration on Wednesday approved the chemical, dimethyl fumarate, which will be sold by Biogen Idec under the name Tecfidera, the third of a spate of oral drugs that are transforming the treatment of multiple sclerosis.

Despite the drug’s seemingly odd history, Wall Street analysts, doctors and patients expect Tecfidera to become a blockbuster because of its combination of efficacy and relative safety and the convenience of being a pill. Doctors and analysts say some patients have been putting off starting treatment until Tecfidera is available.

Feedback from doctors was “highly positive, with a strong consensus that Tecfidera offers a more favorable clinical profile than other oral or injectable first-line options,” Thomas Wei, an analyst at Jefferies, wrote on Monday.