Monotherapy with a low-dose lipopeptide HIV fusion inhibitor maintains long-term viral suppression in rhesus macaques.

Combination antiretroviral therapy (cART) dramatically improves survival of HIV-infected patients, but lifelong treatment can ultimately result in cumulative toxicities and drug resistance, thus necessitating the development of new drugs with significantly improved pharmaceutical profiles. We recently found that the fusion inhibitor T-20 (enfuvirtide)-based lipopeptides possess dramatically increased anti-HIV activity. Herein, a group of novel lipopeptides were designed with different lengths of fatty acids, identifying a stearic acid-modified lipopeptide (LP-80) with the most potent anti-HIV activity. It inhibited a large panel of divergent HIV subtypes with a mean IC50 in the extremely low picomolar range, being > 5,300-fold more active than T-20 and the neutralizing antibody VRC01. It also sustained the potent activity against T-20-resistant mutants and exhibited very high therapeutic selectivity index. Pharmacokinetics of LP-80 in rats and monkeys verified its potent and long-acting anti-HIV activity. In the monkey, subcutaneous administration of 3 mg/kg LP-80 yielded serum concentrations of 1,147 ng/ml after injection 72 h and 9 ng/ml after injection 168 h (7 days), equivalent to 42,062- and 330-fold higher than the measured IC50 value. In SHIV infected rhesus macaques, a single low-dose LP-80 (3 mg/kg) sharply reduced viral loads to below the limitation of detection, and twice-weekly monotherapy could maintain long-term viral suppression.