Enabled clinical use of an HIV-1 attachment inhibitor through drug delivery.

The clinical advancement of HIV-1 attachment inhibitors was hindered initially by poor bioavailability. Attempts to identify improved candidates revealed that solubility and dissolution-rate-limited absorption are barriers to achieving adequate antiviral plasma levels. This was mitigated by forming nanosized drugs or by creating stabilised amorphous drug-polymer composites. In further improving drug potency and mitigating solubility-limited bioavailability, a candidate based on a phosphate ester prodrug was identified that, although having excellent bioavailability, exhibited unacceptable pharmacokinetics. Based on in silico modelling and a site of absorption study it was confirmed that creating an extended release formulation could provide the desired pharmacokinetic profile. The optimised formulation showed good antiviral activity when dosed employing a once or twice a day regimen.