Isis Pharmaceuticals Inc. (NASDAQ:ISIS) was trading down Monday after reporting worse-than-expected second-quarter earnings, as partnership-related revenues could not fully offset rising costs.

The drug maker posted net loss of $25.2 million, or 25 cents a share, compared with a loss of $2.73 million, or 3 cents a share, in the same quarter last year, and falling short of average analyst estimates of a loss of 15 cents, according to a Thomson Reuters poll.

Revenue for the Carlsbad, Calif.-based company was $23.5 million, down from $31 million a year ago, and missing the Street’s view of $25.63 million.

The company saw revenue boosts from its new partnership with GlaxoSmithKline (NYSE:GSK)in the form of a $35 million upfront payment, which it began recognizing last quarter.

Isis chief operating officer and chief financial officer B. Lynne Parshall said the company’s second quarter results and partnerships were "very successful."

Despite the partnership-related revenues, expenses increased from the prior year, from $35.8 million to $42.2 million, causing the loss the widen.