Phase 2 Study of XP-8121: Once-Weekly Subcutaneous Levothyroxine for Adult Hypothyroidism

Study Overview

Hypothyroidism is a common endocrine disorder in which the thyroid gland does not produce enough hormone to meet the body’s needs. Standard treatment is daily oral levothyroxine sodium (LT4), a synthetic form of thyroid hormone that replaces what the body is missing. Although this therapy is highly effective, some people struggle with daily adherence, timing around food and other medications, or variable absorption in the gastrointestinal tract. These practical limitations have encouraged interest in alternative formulations.

This Phase 2 study evaluated XP-8121, a ready-to-use liquid levothyroxine sodium formulation designed for once-weekly subcutaneous (under-the-skin) administration. By bypassing the digestive system, this approach may offer a more convenient and potentially more reliable way to deliver thyroid hormone replacement.