Ironwood's LINZESS dominates IBS-C market despite 2025 sales dip

Ironwood Pharmaceuticals has reported strong financial results for 2025, driven by its flagship drug LINZESS. The company ended the year with $250 million in cash and generated $127 million from operating activities. Despite a slight dip in U.S. sales, the treatment remains a market leader in chronic constipation and irritable bowel syndrome with constipation (IBS-C).

LINZESS achieved $865 million in U.S. net sales during 2025, though this marked a 6% decline from the previous year. The drop was largely due to pricing pressures from Medicare Part D adjustments. Still, the drug maintained an 11% growth in prescription demand for the second year running, with an 8% rise in new patients starting treatment.

The medication held a 45% share of the U.S. prescription market for IBS-C and chronic constipation by the end of 2025. Over 5.7 million unique patients have now been treated with LINZESS since its launch. In November 2025, the FDA expanded its approval to include pediatric chronic idiopathic constipation, further broadening its reach.

Ironwood's financial discipline paid off, with operating expenses cut by $61 million compared to 2024. The company recorded an adjusted EBITDA of $138 million for the year. Looking ahead, LINZESS net sales are forecasted to grow by more than 30% in 2026, reaching between $1.125 billion and $1.175 billion. Adjusted EBITDA is also expected to exceed $300 million next year.

With a strong cash position and expanded market approval, Ironwood Pharmaceuticals enters 2026 on solid footing. LINZESS remains a dominant treatment in its category, and the company's cost controls have improved profitability. The projected sales growth and EBITDA targets signal confidence in the drug's continued performance.