Medicinal chemistry applied to a synthetic protein: Development of highly potent HIV entry inhibitors

Abstract

We have used total chemical synthesis to perform high-resolution dissection of the pharmacophore of a potent anti-HIV protein, the aminooxypentane oxime of [glyoxylyl 1 ]RANTES(2-68), known as AOP-RANTES, of which we designed and made 37 analogs. All involved incorporation of one or more rationally chosen nonnatural noncoded structures, for which we found a clear comparative advantage over coded ones. We investigated structure-activity relationships in the pharmacophore by screening the analogs for their ability to block the HIV entry process and produced a derivative, PSC-RANTES {N-nonanoyl, des-Ser 1 [L-thioproline 2 , L-cyclohexylglycine 3 ]-RANTES(2-68)}, which is 50 times more potent than AOP-RANTES. This promising group of compounds might be optimized yet further as potential prophylactic and therapeutic anti-HIV agents. The remarkable potency of our RANTES analogs probably involves the unusual mechanism of intracellular sequestration of CC-chemokine receptor 5 (CCR5), and it has been suggested that this arises from enhanced affinity for the receptor. We found that inhibitory potency and capacity to induce CCR5 down-modulation do appear to be correlated, but that unexpectedly, inhibitory potency and affinity for CCR5 do not. We believe this study represents the proof of principle for the use of a medicinal chemistry approach, above all one showing the advantage of noncoded structures, to the optimization of the pharmacological properties of a protein. Medicinal chemistry of small molecules is the foundation of modern pharmaceutical practice, and we believe we have shown that techniques have now reached the point at which the approach could also be applied to the many macromolecular drugs now in common use.

Highly potent, fully recombinant anti-HIV chemokines: Reengineering a low-cost microbicide

“…2). As noted (10), brief exposure to PSC-RANTES led to prolonged intracellular sequestration of CCR5. 6P4-RANTES induced CCR5 sequestration to a similar extent and duration to PSC-RANTES.…”

“…Thus, events downstream of CCR5 signaling could lead to mucosal inflammation, a phenomenon known to enhance HIV infection (18). The ideal candidate CCR5 inhibitor for microbicide use would show the potency of PSC-RANTES without signaling via CCR5, but it has been suggested (19) that this would be an improbable goal, because (i) the receptor sequestration induced by PSC-RANTES and related molecules is needed for potent HIV inhibition (10), and (ii) receptor activation is an obligatory part of the CCR5 sequestration process (15,19).…”

“…PSC-RANTES acts via an unusual mechanism involving the induction of long-term intracellular sequestration of CCR5 (10,13). This may be helpful for topical HIV prevention (14) because of prolonged protection of target cells after a single dose and setting a high barrier against the development of resistant viruses.…”

“…Certain analogs of the native chemokine ligands of CCR5 strongly inhibit coreceptor activity (9), the most promising described so far being PSC-RANTES, an analog of the protein RANTES/CCL5 in which several nonnatural, noncoded structures are incorporated into the N-terminal region (10). PSC-RANTES is a highly potent inhibitor of CCR5-dependent HIV entry in vitro (10,11) and provides full protection from R5-tropic SHIV infection in a macaque vaginal challenge model (7). Despite its high in vitro potency, high concentrations were required for protective activity in macaques (7), as has been seen for other microbicide candidates so far (2,3).…”

Enhancing Antitumor Immune Responses by Optimized Combinations of Cell-penetrating Peptide-based Vaccines and Adjuvants

“…Peptides were synthesized on an ABI 433 synthesizer customized to perform Boc chemistry with in situ neutralization as already described. 34 Purity and integrity of each peptide were routinely verified by high-performance liquid chromatography and mass spectrometry. CD experiments were carried out in a 0.1 cm quartz cell using a Jasco J-710 spectrometer (Jasco, Easton, MD) with 100 μmol/l peptide solutions (1.25% trifluoroethanol in dH 2 0) at 20°C.…”