Drug maker

Sepracor

(SEPR)

Monday beat handily Wall Street estimates for the first quarter, but the suspension of testing on a new drug sent shares in the company down sharply.

The Marlborough, Mass-based company posted a first-quarter net loss of $48 million, or 63 cents per share, compared with a net loss of $54 million, or 76 cents per share in the year-ago quarter.

Analysts were expecting a net loss of 98 cents per share, according to consensus figures compiled by

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Thompson Financial/First Call

.

First-quarter revenue totaled $33.9 million, compared with $15.1 million in revenue during the first quarter of last year.

But Sepracor shares were trading down Monday, off $6.64, or 15.6%, to $35.89, after the company disclosed problems with testing of ticalopride, a drug used to treat gastroesophageal reflux disease (GERD).

Sepracor said testing was being suspended pending analysis of a "small number of adverse events reported in GERD and diabetes patients." Although it is unknown whether the events are related to the drug, Sepracor said its partner,

Janssen Pharmaceutica

, decided it was prudent to suspend testing until the events could be investigated.