{"id":37,"date":"2026-05-27T02:38:05","date_gmt":"2026-05-27T02:38:05","guid":{"rendered":"https:\/\/astinovabiolabs.com\/blog\/?p=37"},"modified":"2026-05-27T02:38:05","modified_gmt":"2026-05-27T02:38:05","slug":"synthesis-of-difamilast-adquey","status":"publish","type":"post","link":"https:\/\/astinovabiolabs.com\/blog\/synthesis-of-difamilast-adquey\/","title":{"rendered":"Synthesis of Difamilast (ADQUEY)"},"content":{"rendered":"\n
Patent \/ Application<\/th>Type<\/th>Assignee<\/th>Filed<\/th>Expiry (~)<\/th><\/th><\/tr><\/thead>
WO 2007\/058338 A1 (US 7,919,617 B2; EP 1,953,148 B1; JP 4,975,757 B2)<\/strong><\/td>Composition of matter (originator)<\/td>Otsuka Pharmaceutical Co., Ltd.<\/td>2006-11-16 (priority 2005-11-15, JP 2005-330289)<\/td>~Nov 2026 nominal (US 7,919,617 expiry ~2026-2027 absent PTE); PTE filing window opens at FDA approval (2026-02-12) \u2014 up to 5 yr PTE possible \u2192 effective LoE 2028\u20132031<\/td><\/td><\/tr>
WO 2010\/041680 A1 \/ JP 5,628,114 B2<\/strong><\/td>Crystal form \/ polymorph (originator)<\/td>Otsuka Pharmaceutical Co., Ltd.<\/td>2009-10-07 (priority JP 2008-263071)<\/td>~Oct 2029 nominal<\/td><\/td><\/tr>
WO 2017\/170219 \/ JP 6,832,946 B2<\/strong><\/td>Topical formulation<\/td>Otsuka Pharmaceutical Co., Ltd.<\/td>~2017<\/td>~2037 nominal<\/td><\/td><\/tr>
Process patent(s) \u2014 Otsuka<\/strong><\/td>Process<\/td>Otsuka Pharmaceutical Co., Ltd.<\/td>~2008\u20132015<\/td>~2028\u20132035<\/td><\/td><\/tr>
[Acrotech \/ Medimetriks licensing-related filings]<\/strong><\/td>License \/ territory<\/td>Acrotech Biopharma Inc (US); Medimetriks Pharmaceuticals (prior US rights holder for atopic dermatitis)<\/td>\u2014<\/td>\u2014<\/td><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Compiled:<\/strong>\u00a02026-05-23 \u00b7\u00a0Trigger event:<\/strong>\u00a0FDA approval, 2026-02-12\u00a0Innovator:<\/strong>\u00a0Acrotech Biopharma Inc (US licensee; originator Otsuka Pharmaceutical Co., Ltd., Japan \u2014 OPA-15406 \/ MM-36)\u00a0Status:<\/strong>\u00a0Approved NME<\/p>\n\n\n\n

Mechanism:<\/strong>\u00a0Topical PDE4 (cAMP-specific phosphodiesterase 4) inhibitor with preferential PDE4B binding (ChEMBL CHEMBL2093863); inhibits cAMP hydrolysis in keratinocytes and T-cells \u2192 reduces pro-inflammatory cytokine release (TNF-\u03b1, IL-4, IL-5, IL-13). PMID 27189825 + 30386231<\/p>\n\n\n\n

Synthesis Route of the Originator<\/strong><\/p>\n\n\n\n

Convergent synthesis disclosed in Otsuka WO 2007\/058338 (Example 5). Eastern fragment is a 4-(difluoromethoxy)-3-isopropoxybenzamide (INT-2) that condenses with 1,3-dichloroacetone under Robinson-Gabriel conditions to give the 2-aryl-4-(chloromethyl)-1,3-oxazole (INT-3); azide displacement then Staudinger reduction (or hydrogenolysis) installs the 4-(aminomethyl) handle (INT-5). Final amide coupling of INT-5 with 2-ethoxybenzoyl chloride (or 2-ethoxybenzoic acid + HATU\/EDC) delivers difamilast. Aryl SM (3,4-disubstituted benzonitrile\/benzamide) is built from vanillin-class catechol via selective O-isopropylation then O-difluoromethylation of the residual phenol (ClCF\u2082H, base) \u2014 both transformations are commodity-scale.<\/p>\n\n\n\n

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Key intermediates<\/strong><\/p>\n\n\n\n

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Crystal Forms, Salts, and Solid-State Profile<\/h2>\n\n\n\n