On July 1, 2023, Sunovion Pharmaceuticals Inc. became part of Sumitomo Pharma America, Inc.,[1] a biopharmaceutical company focused on delivering therapeutic and scientific breakthroughs in areas of critical patient need spanning psychiatry and neurology, oncology, urology, women's health, rare disease, and cell and gene therapies.

In 1993, Marion Merrell Dow, now a part of Sanofi, partnered with Sepracor to develop a purified version of its antihistamine, Seldane, after the latter was required to carry a warning about potentially fatal cardiac arrhythmia.

This purified compound would later be marketed as Allegra, but Sepracor would not profit significantly from its launch, a result of less-than favorable partnership terms.

Sepracor's subsequent products were focused on the treatment of central nervous system and respiratory disorders, under the direction of Gunnar Aberg and John McCullough.

In 2006, the FDA approved Sepracor's drug Brovana to treat chronic obstructive pulmonary disease (COPD).