Mufemilast API is a small-molecule pharmaceutical active ingredient belonging to the phosphodiesterase 4 (PDE4) inhibitor class. Also known by development codes HEMAY005 and HEMAY-005, Mufemilast has been developed as an anti-inflammatory therapy with activity involving PDE4 and PDE4B. Its chemical identity is well characterized, with a defined stereochemistry and a single stereocenter.
Mufemilast has the molecular formula C20H22N2O7S2 and a molecular weight of 466.53 g/mol. Its CAS number is 1255909-03-5, and its FDA Global Substance Registration System UNII is 4QX9BK9E7P. The compound has the InChIKey PRSNGWLHNWGOKD-CQSZACIVSA-N.
Mufemilast is a phosphodiesterase 4 (PDE4) inhibitor with activity involving PDE4B. PDE4 enzymes regulate intracellular cyclic adenosine monophosphate (cAMP), an important signaling molecule involved in inflammatory pathways. Inhibition of PDE4 can increase intracellular cAMP and influence inflammatory signaling. Mufemilast has therefore been investigated as an anti-inflammatory pharmaceutical compound.
Mufemilast was developed for inflammatory and immune-mediated diseases. It received approval in China in 2025 for the treatment of moderate-to-severe plaque psoriasis. Current pharmacology resources identify Mufemilast as an approved drug in China under the brand name Momishin®.
Mufemilast continues to be investigated in additional inflammatory conditions. Clinical research has included Behçet's syndrome, ulcerative colitis, ankylosing spondylitis and other immune-mediated conditions. A 2026 Phase 2 randomized clinical trial reported significant reductions in oral-ulcer burden in patients with Behçet's syndrome receiving Mufemilast compared with placebo.
Mufemilast is relevant to pharmaceutical development involving PDE4 inhibitors, anti-inflammatory therapies, dermatology APIs and immunology-focused drug development. Its small-molecule structure and defined stereochemistry make it suitable for conventional chemical API characterization using chromatographic, spectroscopic and other analytical techniques.
Mufemilast is a synthetic organic compound with one defined stereocenter. The substance has nine hydrogen-bond acceptors, one hydrogen-bond donor and a calculated topological polar surface area of approximately 152.76 Ų. Its calculated XLogP is approximately 0.66. These properties are useful for understanding the physicochemical profile of the active substance during pharmaceutical development.
Mufemilast has absolute stereochemistry with one defined stereocenter. The chemical structure represented in authoritative substance databases corresponds to the (1S) configuration. Therefore, stereochemical identity should be considered an important quality attribute during API characterization and analytical development.
Quality evaluation of Mufemilast API should include appropriate controls for identity, assay, stereochemical purity, related substances, residual solvents, water content, elemental impurities and other applicable quality attributes.
Because Mufemilast does not have a broadly established pharmacopoeial monograph identified in the reviewed sources, numerical release specifications for parameters such as assay, individual impurities, total impurities, loss on drying and residue on ignition should not be assumed or copied from unrelated APIs. These limits should be established according to the applicable approved specification and validated analytical methods.
Mufemilast has progressed from clinical development to regulatory approval in China. IUPHAR/BPS currently identifies it as an approved drug following China NMPA approval in 2025. The drug is associated with the treatment of plaque psoriasis, while additional clinical development continues for other inflammatory and immune-mediated conditions.
Mufemilast API may be relevant to pharmaceutical research and manufacturing activities involving PDE4 inhibition, dermatology, inflammatory diseases and immunology. Its development history and current regulatory status make it an important newer small-molecule API within the PDE4 inhibitor class.
| Parameter | Specification |
|---|---|
| Appearance | White crystalline powder or crystals |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| Residue on Ignition | NMT 0.5% |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 1.0% |
| Water Content | NMT 1.0% |