Homotaurine (also known as tramiprosate (INN), 3-amino-1-propanesulfonic acid, or 3-APS) is a natural sulfonic acid found in seaweed.[3] It is analogous to taurine, but with an extra carbon in its chain. It has GABAergic activity, apparently by mimicking GABA, which it resembles.[4]
Homotaurine was investigated in a Phase III clinical trial as a potential treatment for Alzheimer's disease (AD) that did not show efficacy. However, post-hoc analyses have shown positive and significant effects of homotaurine on secondary endpoints and subgroups of patients, including a reduction in hippocampal volume loss and lower decline in memory function in the overall cohort, as well as a reduction in global cognitive decline in APOE4 allele carriers, suggesting a disease-modifying effect.[5] A study in cognitive impairment done in 2018 did show positive benefits.[6]
Homotaurine is currently in a phase 3 study with expected FDA approval as the first disease modifying drug for AD.[7][8]
In preclinical studies it had been found to bind to soluble amyloid beta and inhibit the formation of neurotoxic aggregates.[5][9] Homotaurine has also shown anticonvulsant activities, reduction in skeletal muscle tonus, and hypothermic activity.[10]
Homotaurine has been reported as a GABA antagonist,[4] as well as a GABA agonist.[10][11]In vitro studies have found that homotaurine is a GABAA partial agonist[12] as well as a GABAB receptor partial agonist with low efficacy, becoming an antagonist and displacing the full agonists GABA and baclofen at this receptor.[13] In a study in rats, homotaurine reversed the catatonia induced by baclofen (the prototypical GABAB agonist),[14] and was able to produce analgesia via the GABAB receptor, an effect that was abolished when CGP-35348, a GABAB receptor antagonist was applied.[15][16]
In a human study homotaurine selectively and fully inhibits the formation of Aβ42 oligomers at the clinical dose, without evidence of vasogenic edema.[7]
One study in rats showed that homotaurine suppressed ethanol-stimulated dopamine release, as well as ethanol intake and preference in rats in a way similar to the N-acetyl derivative of homotaurine, acamprosate.[17]
^ abCaltagirone, C; Ferrannini, L; Marchionni, N; Nappi, G; Scapagnini, G; Trabucchi, M (December 2012). "The potential protective effect of tramiprosate (homotaurine) against Alzheimer's disease: a review". Aging Clinical and Experimental Research. 24 (6): 580–587. doi:10.3275/8585. PMID22961121. S2CID10816430.
^Martorana, A.; Motta, C; Koch, G.; Massaia, M.; Mondino, S.; Raniero, I.; Vacca, A.; Di Lorenzo, F.; Cavallo, G.; Oddenino, E.; Pavanelli, E.; Maniscalco, M.; Montano, V.; Mastropietro, A.; Bellia, N. C.; Ciravegna, E.; La Rocca, M.; Vitale, E.; Lorico, F.; Zacchettin, B.; Scalise, A.; Codemo, A.; Gabelli, C.; Spano, M.; Poli, S.; Panuccio, D.; Bruno, P.; Alfieri, P.; Ruggiero, R.; Cursi, F.; Levi Della Vida, G. (15 March 2018). "Effect of homotaurine in patients with cognitive impairment: results from an Italian observational retrospective study". Journal of Gerontology and Geriatrics. 66: 15–20.
^Serrano, M.Isabel; Serrano, Jose S.; Fernández, Ana; Asadi, Ihklas; Serrano-Martino, M.Carmen (March 1998). "GABAB Receptors and Opioid Mechanisms Involved in Homotaurine-Induced Analgesia". General Pharmacology: The Vascular System. 30 (3): 411–415. doi:10.1016/s0306-3623(97)00279-6. PMID9510095.
^Serrano, Maria Isabel; Serrano, Jose S.; Asadi, Ikhlas; Fernandez, Ana; Serrano-Martino, Maria Carmen (16 June 2001). "Role of K+-channels in homotaurine-induced analgesia". Fundamental and Clinical Pharmacology. 15 (3): 167–173. doi:10.1046/j.1472-8206.2001.00026.x. PMID11468027. S2CID19694376.
^Olive, M.Foster; Nannini, Michelle A; Ou, Christine J; Koenig, Heather N; Hodge, Clyde W (February 2002). "Effects of acute acamprosate and homotaurine on ethanol intake and ethanol-stimulated mesolimbic dopamine release". European Journal of Pharmacology. 437 (1–2): 55–61. doi:10.1016/s0014-2999(02)01272-4. PMID11864639.
