Prevention and treatment of SHIVAD8 infection in rhesus macaques by a potent d-peptide HIV entry inhibitor.

Cholesterol-PIE12-trimer (CPT31) is a potent d-peptide HIV entry inhibitor that targets the highly conserved gp41 N-peptide pocket region. CPT31 exhibited strong inhibitory breadth against diverse panels of primary virus isolates. In a simian-HIV chimeric virus AD8 (SHIVAD8) macaque model, CPT31 prevented infection from a single high-dose rectal challenge. In chronically infected animals, CPT31 monotherapy rapidly reduced viral load by ∼2 logs before rebound occurred due to the emergence of drug resistance. In chronically infected animals with viremia initially controlled by combination antiretroviral therapy (cART), CPT31 monotherapy prevented viral rebound after discontinuation of cART. These data establish CPT31 as a promising candidate for HIV prevention and treatment.

Pharmacokinetic and Chemical Synthesis Optimization of a Potent d-Peptide HIV Entry Inhibitor Suitable for Extended-Release Delivery.

Peptides often suffer from short in vivo half-lives due to proteolysis and renal clearance that limit their therapeutic potential in many indications, necessitating pharmacokinetic (PK) enhancement. d-Peptides, composed of mirror-image d-amino acids, overcome proteolytic degradation but are still vulnerable to renal filtration due to their small size. If renal filtration could be slowed, d-peptides would be promising therapeutic agents for infrequent dosing, such as in extended-release depots. Here, we tether a diverse set of PK-enhancing cargoes to our potent, protease-resistant d-peptide HIV entry inhibitor, PIE12-trimer. This inhibitor panel provides an opportunity to evaluate the PK impact of the cargoes independently of proteolysis. While all the PK-enhancing strategies (PEGylation, acylation, alkylation, and cholesterol conjugation) improved in vivo half-life, cholesterol conjugation of PIE12-trimer dramatically improves both antiviral potency and half-life in rats, making it our lead anti-HIV drug candidate. We designed its chemical synthesis for large-scale production (CPT31) and demonstrated that the PK profile in cynomolgous monkeys supports future development of monthly or less frequent depot dosing in humans. CPT31 could address an urgent need in both HIV prevention and treatment.

One percent tenofovir applied topically to humanized BLT mice and used according to the CAPRISA 004 experimental design demonstrates partial protection from vaginal HIV infection, validating the BLT model for evaluation of new microbicide candidates.

Recent iPrEx clinical trial results provided evidence that systemic preexposure prophylaxis (PrEP) with emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF) can partially prevent rectal HIV transmission in humans. Similarly, we have previously demonstrated that systemic administration of the same FTC-TDF combination efficiently prevented rectal transmission in humanized bone marrow/liver/thymus (BLT) mice. The CAPRISA 004 trial recently demonstrated that topical application of the tenofovir could partially prevent vaginal HIV-1 transmission in humans. To further validate the usefulness of the BLT mouse model for testing HIV prevention strategies, we evaluated the topical administration of tenofovir as used in CAPRISA 004 to prevent vaginal HIV transmission in BLT mice. Our results demonstrate that vaginally administered 1% tenofovir significantly reduced HIV transmission in BLT mice (P = 0.002). Together with the results obtained after systemic antiretroviral PrEP, these topical inhibitor data serve to validate the use of humanized BLT mice to evaluate both systemic and topical inhibitors of HIV transmission. Based on these observations, we tested six additional microbicide candidates for their ability to prevent vaginal HIV transmission: a C-peptide fusion inhibitor (C52L), a membrane-disrupting amphipathic peptide inhibitor (C5A), a trimeric d-peptide fusion inhibitor (PIE12-Trimer), a combination of reverse transcriptase inhibitors (FTC-TDF), a thioester zinc finger inhibitor (TC247), and a small-molecule Rac inhibitor (NSC23766). No protection was seen with the Rac inhibitor NSC23766. The thioester compound TC247 offered partial protection. Significant protection was afforded by FTC-TDF, and complete protection was offered by three different peptide inhibitors tested. Our results demonstrate that these effective topical inhibitors have excellent potential to prevent vaginal HIV transmission in humans.