L-810,191

L-810,191 (also known as L-1) is an experimental small molecule HIV-1 integrase strand transfer inhibitor (INSTI) developed by Merck. It was evaluated in a Phase 1 microdose pharmacokinetic study (NCT00959621) to assess its intravenous and oral disposition using accelerator mass spectrometry (AMS). The compound functions by binding to the active site of the HIV-1 integrase enzyme, specifically blocking the strand transfer step of viral DNA integration into the host cell genome. This mechanism prevents the formation of the HIV provirus and halts viral replication. L-810,191 was one of several candidates, alongside L-870,810 and L-870,812, investigated by Merck to identify optimal candidates for further clinical development. However, it did not progress to late-stage clinical trials and is no longer in active development.