We have synthesized (CPC Scientific, Inc.) four stapled peptides, as depicted in Figure 2. We also synthesized the linear peptide, NYBSP-C, as a control. Besides, we purchased a linear peptide, SBP1, to use as a control, which was reported recently to bind to SARS-CoV-2 RBD with high affinity (KD = 47nM).

1. Pfizer Neusentis, The Portway Building, Granta Park, Cambridge, UK.
2. Pfizer Worldwide Research & Development, Eastern Point Road, Groton, Connecticut 06340, USA.
3. CPC Scientific Inc., 1245 Reamwood Avenue, Sunnyvale, CA 94089, USA.

"antipeptide (EGVYVHPV), angiotensin II, human (DRVYIHPF), and isotopically (13C) labeled heptapeptide (AAAAHAA-NH2 [where “A” indicates a carbon thirteen (13C) "Synthesis was conducted at CPC Scientific Inc. Ac-Asp(OtBu)-Thr(tBu)-His(Trt)-Phe-Pro-Ile-Cys(Trt)-Ile-PhePEG3-Arg(Pbf)-Arg(Pbf)-Lys(Boc)-wang resin (2).. Ac-Asp-Thr-His-Phe-Pro-Ile-Cys-Ile-Phe-PEG3-Arg-Arg-Lys(BODIPY_TMR_C6)."

To date only two entry inhibitors are available, Maraviroc which targets the co-receptor CCR5 3;4 and Enfuvirtide, a peptide drug which interacts with the N-terminal heptad repeat of gp41 of HIV to form an inactive hetero six-helix bundle preventing infection of host cells 5;6. Despite the success achieved with the HAART the emergence of resistant viruses and the side effects of these therapies highlight the need of novel anti-retroviral agents to overcome these problems.

In this report, we expanded the study to i,i+7 hydrocarbon-stapled peptides to delineate their mechanism of action and antiviral activity. We identified three potent inhibitors, NYAD-36, -66 and -67, which showed strong binding to CA in NMR and isothermal titration calorimetry (ITC) studies and disrupted the formation of mature-like particles. They showed typical α-helical structures and penetrated cells; however, the cell penetration was not as efficient as observed with the i,i+4 peptides.

All peptides used in this study (Table 1) were synthesized by an Fmoc/t-Butyl solid-phase strategy on a 2-chlorotrityl chloride resin preloaded with the Fmoc-Thr(tBu)-OH. Amino acid derivatives were obtained from CPC Scientific (Sunnyvale, CA)