What a failed drug does (and is there hope for latrepirdine?)

Latrepirdine (Dimebon) was initially used as an antihistamine drug in Russia. It was later found to be neuroprotective, and entered phase II clinical trials in the US for both Alzheimer’s disease and Huntington’s disease. However, Dimebon failed in a US-based phase II replication trial of a prior successful Russian phase II trial of mild-to-moderate AD. Given the initial promise of the drug and split results,  as well as the lack of treatments for neurodegenerative diseases, there in is significant interest in understanding the underlying molecular mechanism(s) for the drug’s effects.

In a paper appearing this week in Molecular Psychiatry, Brandeis researchers in the Petsko-Ringe lab, including postdoc Shulin Ju and undergraduate Jessica Liken ’11, used yeast models of neurodegenerative disease associated proteins to show that Dimebon specifically protects yeast from the cytotoxiciy of α-synuclein, a protein involved in Parkinson’s disease. They further showed that protection is mediated through its up-regulation of autophagy pathway. In collaboration with Sam Gandy‘s group at Mount Sinai School of Medicine, these findings were further confirmed and validated in neuronal cell and animal models.

Given these observations, disparities in the contribution of α-synuclein to the neuropathology between the Russian and US Dimebon studies might also explain, at least in part, the inconsistency of the cognitive benefit in the two trials. If this speculation is correct, then it may be interesting to test for benefits of Dimebon in treating synucleinopathies such as Parkinson’s disease, Lewy body dementia, REM sleep disorder and/or multiple system atrophy.

see also: press release from Mt. Sinai Alzheimer’s Diesease Research Center

Steele JW (*), Ju S(*), Lachenmayer ML(*), Liken J, Stock A, Kim SH, Delgado LM, Alfaro IE, Bernales S, Verdile G, Bharadwaj P, Gupta V, Barr R, Friss A, Dolios G, Wang R, Ringe D, Protter AA, Martins RN, Ehrlich ME, Yue Z, Petsko GA, Gandy S. Latrepirdine stimulates autophagy and reduces accumulation of alpha-synuclein in cells and in mouse brain. Molecular psychiatry. 2012.

Steele JW(*), Lachenmayer ML(*), Ju S, Stock A, Liken J, Kim SH, Delgado LM, Alfaro IE, Bernales S, Verdile G, Bharadwaj P, Gupta V, Barr R, Friss A, Dolios G, Wang R, Ringe D, Fraser P, Westaway D, St George-Hyslop PH, Szabo P, Relkin NR, Buxbaum JD, Glabe CG, Protter AA, Martins RN, Ehrlich ME, Petsko GA, Yue Z, Gandy S. Latrepirdine improves cognition and arrests progression of neuropathology in an Alzheimer’s mouse model. Molecular psychiatry. 2012.

New route to lycopodium alkaloids

The lycopodium alkaloids are a large and extensively studied alkaloid family. Huperzine A (1), the medicinally most significant lycopodine alkaloid as a potential treatment for Alzheimer’s disease, functions as an acetylcholinesterase inhibitor but may have other roles as has been addressed in several recent reviews.  Sauroine (2, 7,8-dihydroxylycopodine), from Huperzia saururus, was reported in 2004 and shown in 2009 to improve memory retention in the step-down test in male Wistar rats, significantly increasing hippocampal plasticity. 7-Hydroxylycopodine (3), from Huperzia serrata, was also reported in 2004 and may have related biological activity.

In their recent Organic Letters paper entitled the Synthesis of (±)-7-Hydroxylycopodine, the Snider lab at Brandeis developed a new general route to these bridgehead hydroxylated lycopodines. They reported a practical six-step synthesis of 7-hydroxylycopodine which makes it readily available for further biological evaluation. The key step of the synthesis is the treatment of bicyclic enol ether 4 with 60% sulfuric acid that affords tricyclic amino alcohol 5, which is further elaborated to 7-hydroxylycopodine (3) in three steps. The application of this route to the synthesis of sauroine (2) is now under investigation.