In complement to an effective vaccine, development of potent anti-HIV microbicides remains an important priority. We
have previously shown that the miniCD4 M48U1, a functional mimetic of sCD4 presented on a 27 amino-acid stable scaffold,
inhibits a broad range of HIV-1 isolates at sub-nanomolar concentrations in cellular models. Here, we report that M48U1
inhibits efficiently HIV-1Ba-L in human mucosal explants of cervical and colorectal tissues. In vivo efficacy of M48U1 was
evaluated in nonhuman primate (NHP) model of mucosal challenge with SHIV162P3 after assessing pharmacokinetics and
pharmacodynamics of a miniCD4 gel formulation in sexually matured female cynomolgus macaques. Among 12 females,
half were treated with hydroxyethylcellulose-based gel (control), the other half received the same gel containing 3 mg/g of
M48U1, one hour before vaginal route challenge with 10 AID50 of SHIV162P3. All control animals were infected with a peak
plasma viral load of 105
–106 viral RNA (vRNA) copies per mL. In animals treated with miniCD4, 5 out of 6 were fully protected
from acquisition of infection, as assessed by qRT-PCR for vRNA detection in plasma, qPCR for viral DNA detection in PBMC
and lymph node cells. The only infected animal in this group had a delayed peak of viremia of one week. These results
demonstrate that M48U1 miniCD4 acts in vivo as a potent entry inhibitor, which may be considered in microbicide
developments.