SANTA CLARA, Calif. (AP) — XenoPort Inc. said today that it has run into supply problems for its restless legs syndrome treatment Horizant.

The company said it’s received word from patients unable to fill their Horizant prescriptions. XenoPort hopes that a new stock of Horizant will be in pharmacies in June, but the timing is uncertain.

Shares of the Santa Clara, Calif., company fell 25 cents, or 3.4 percent, to $7.01 in morning trading.

XenoPort blamed the shortage on manufacturing delays at British drugmaker GlaxoSmithKline, which holds commercialization rights to Horizant in the United States. Glaxo is working with its contract manufacturer to resolve problems, XenoPort said.

Glaxo is supplying XenoPort with Horizant until Oct. 30 under an agreement between the companies. XenoPort is preparing to take over sales of the drug May 1.

Last year, the Food and Drug Administration also approved Horizant as a treatment for nerve pain that follows shingles, a viral infection related to chicken pox. XenoPort also is developing potential treatments for Parkinson’s disease, multiple sclerosis and psoriasis.