Ardelyx shares were lower in pre-market trading after the company cut its outlook for its irritable bowel syndrome treatment.

The stock fell 20% to $3.90 before the opening bell Friday. Through the prior close, shares were already down 21% this year.

The commercial-stage biopharmaceutical company said Thursday evening that it now expects full-year revenue for its IBS treatment Ibsrela to be $350 million to $370 million. It was previously guiding for $410.0 million to $430.0 million.

Ardelyx reaffirmed its long-term outlook for Ibsrela, but said it is evaluating the evolving market dynamics around the drug and how those dynamics could impact the timing of its $1 billion long-term sales target.

Ibsrela sales in the second quarter were below the company's expectations, primarily due to increased utilization-management processes from payors that Ardelyx isn't actively addressing.

Overall sales were just under Wall Street estimates at $120.9 million versus the $121 million expectation, according to FactSet. The loss per share of 7 cents was in line with analysts' projections.