Design and synthesis of 3-aminophthalazine derivatives and structural analogues as PDE5 inhibitors: anti-allodynic effect against neuropathic pain in a mouse model

Neuropathic pain is a chronic pain caused by a lesion or disease affecting the somatosensory nervous system. To date, no specific treatment has been developed to cure this pain. Antidepressants and anticonvulsant drugs are used, but they do not demonstrate universal efficacy, and they often cause detrimental adverse effects. Some studies highlighted the efficacy of sildenafil, a well-known inhibitor of phosphodiesterase 5 (PDE5, (IC50 = 3.3 nM)), in models of pain. Based on these results, we focused our attention on MY 5445, another known PDE5 inhibitor. Homologues, isosteres and structural analogues of MY 5445 were designed and all synthesized compounds were evaluated for their inhibitory activity toward PDE5. Selectivity profiles towards other PDE1-4 isoenzymes, water solubility and stability in acidic medium of the most potent PDE5 inhibitors were determined and the aminophthalazine 16h and its mimetic 41n (3-aminoindazole) were evaluated in comparison to MY 5445 (4b) in vivo in a model of neuropathic pain induced by sciatic nerve cuffing in mice (3 and 0.5 mg/kg, ip twice a day). Both compounds showed the same efficacy on neuropathic allodynia as MY 5445, and thus produced a significant relief of mechanical hypersensitivity after 12 days of treatment.

Maud Bollenbach , Claire Lugnier (1) , M Elanie Kremer , Eric Salvat (2) , Salim Megat (3) , Fr Ed Eric Bihel , Jean-Jacques Bourguignon (4) , Michel Barrot (5) , Martine Schmitt (4) , Mélanie Kremer , Frédéric Bihel (6)

1 MSP - Mitochondrie, Stress oxydant et Protection musculaire
2 UNISTRA - Université de Strasbourg
3 INCI - Institut des Neurosciences Cellulaires et Intégratives
4 LIT - Laboratoire d'Innovation Thérapeutique
5 INCI - Institut des Neurosciences Cellulaires et Intégratives
6 Rétrovirus et Maladies Associées

Neuropathic pain is a chronic pain caused by a lesion or disease affecting the somatosensory nervous system. To date, no specific treatment has been developed to cure this pain. Antidepressants and anti-convulsant drugs are used, but they do not demonstrate universal efficacy, and they often cause detrimental adverse effects. Some studies highlighted the efficacy of sildenafil, a well-known inhibitor of phosphodiesterase 5 (PDE5, (IC 50 ¼ 3.3 nM)), in models of pain. Based on these results, we focused our attention on MY 5445, another known PDE5 inhibitor. Homologues, isosteres and structural analogues of MY 5445 were designed and all synthesized compounds were evaluated for their inhibitory activity toward PDE5. Selectivity profiles towards other PDE1-4 isoenzymes, water solubility and stability in acidic medium of the most potent PDE5 inhibitors were determined and the aminophthalazine 16h and its mimetic 41n (3-aminoindazole) were evaluated in comparison to MY 5445 (4b) in vivo in a model of neuropathic pain induced by sciatic nerve cuffing in mice (3 and 0.5 mg/kg, ip twice a day). Both compounds showed the same efficacy on neuropathic allodynia as MY 5445, and thus produced a significant relief of mechanical hypersensitivity after 12 days of treatment.

Domaines: Chimie thérapeutique

Maud Bollenbach, Claire Lugnier, M Elanie Kremer, Eric Salvat, Salim Megat, et al.. Design and synthesis of 3-aminophthalazine derivatives and structural analogues as PDE5 inhibitors: anti-allodynic effect against neuropathic pain in a mouse model. European Journal of Medicinal Chemistry, 2019, 177, pp.269-290. ⟨10.1016/j.ejmech.2019.05.026⟩. ⟨hal-02322399⟩