Validated targets

To determine if the high in vitro potents of the anti-HIV compound 30 translates into antiviral efficiency in vivo, Datema et al. investigated the inhibition of HIV-1 production and of depletion of human T cells in HIV-1-infected SCID-hu Thy/Liv mice [37]. Steady levels of 100 ng of 30 or higher per mL in plasma resulted in significant inhibition of HIV p24 protein formation. Daily injection of 30 caused a dose-dependent decrease in viral p24 production, and this inhibition could be potentiated by coadministration of AZT (or DDI). This study suggested that 30 alone or in combination with the licensed anti-HIV agents AZT and DDI may decrease the virus load in HIV-infected patients and, by extension, that the infectious cell entry step is a valid target for antiviral chemotherapy of HIV disease. 

Although most work to date has focused on the enzyme inhibition aspect, it is possible that the monoclonal VAP-1 antibody discussed above may well be closer to the clinic. The task of designing small molecules to interfere with cell-cell recognition is certainly feasible, but this will not be a trivial effort, more akin to the search for selective selectin antagonists which has proven to be very challenging. As confidence grows in the pharmaceutical industry that SSAO/VAP-1 is a validated target, it is inevitable that considerable resources will be directed to all avenues to block the functional action of this protein. 

This approach offers two opportunities to discover clinically relevant compounds. The first is the compounds identified directly in the Cytection screens. Second, appreciating that these compounds have the desirable biological endpoints, they can be used as "molecular probes" to determine their putative mechanism(s) of action. This "reverse drug discovery"9 identifies "validated" targets that can be the basis for mechanistic screens that could lead to the discovery of additional compounds. 

Another problem in validating targets for behavioral disorders related to neurotransmitter abnormalities is the interplay between several neurotransmitter systems in specific brain regions. For example, in the hippocampus, limbic, and nigral-striatal areas, functions connected by serotonin, norepinephrine, and dopamine are interconnected so that blocking selected receptor subtypes or changing synaptic levels of certain neurotransmitters may... 

Cardiosafety risk assessment in early drug discovery projects focuses on hERG as the most frequently hit and well validated target linked to TdP. In pharmaceutical settings, it is common to use a combination of in silico and high-throughput experimental assays to assess LQT risk for larger numbers of compounds [8, 14[. 

There are few commercial fungicides that have glycerophospholipid biosynthesis inhibition as their mode of action. The validated targets are phosphatidylcholine synthesis and phosphatidylinositol synthesis. 

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