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Other names | Dopazinol; Nazagolide; PHNO; (+)-PHNO; (+)-4-Propyl-9-hydroxynaphthoxazine; 4-Propyl-9-hydroxy-1,2,3,4a,5,6-hexahydronaphthoxazine; L-647339; L647339; MK-458; MK458 |
Routes of administration | Oral; Transdermal |
Drug class | Dopamine D2 and D3 receptor agonist; Antiparkinsonian agent |
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Formula | C15H21NO2 |
Molar mass | 247.338 g·mol−1 |
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Naxagolide (INN ), also known as PHNO, dopazinol, L-647339, and MK-458 among other synonyms, is a dopamine receptor agonist which was developed for the treatment of Parkinson's disease but was never marketed. [1] [2] [3] [4] A radiolabeled form has been used for brain imaging. [5] [3] The drug was developed for use both orally and transdermally. [4] [6]
It acts as a potent dopamine D2 and D3 receptor agonist. [6] [7] Naxagolide was described in the 1990s as the most potent dopamine D2 receptor agonist that had been used. [8] [9] It shows about 50-fold selectivity for the dopamine D3 receptor over the dopamine D2 receptor (Ki = 0.16 nM vs. 8.5 nM). [7] The drug is a naphthoxazine derivative. [6] It is structurally similar to ergolines such as pergolide and cabergoline but is a non-ergoline itself. [10] [9]
Naxagolide was first described in 1984 and was under development by Merck & Co in the 1980s and 1990s. [3] [4] It was developed for treatment of Parkinson's disease and reached phase 2 clinical trials for this indication. [3] The drug was discontinued due to inadequate effectiveness and/or due to toxicity. [6] [8]
PHNO (naxagolide, MK 458) [21], the most potent D2 agonist ever used, has been withdrawn because of animal toxicity, and this is also the case for mesulergin (CU 32 085), a D1 and D2 agonist.
Two non-ergot dopaminergic agonists were developed for the potential of transdermal administration. (+)4—Propyl-9-hydroxynaphthoxazine (PHNO; also known as MK-458 or naxagolide), perhaps the most potent dopaminergic compound, is readily absorbed through the skin. Although administration of PHNO in an oral sustained-release form showed antiparkinsonian effectiveness,147 this drug was discontinued from further development before the transdermal delivery route could be tested in human subjects.