A ProTide of AZT Shows Activity Against Human Papillomaviruses

Infection by human papillomaviruses (HPV) can cause warts and tumors. So far, no small molecule antiviral has been approved for the treatment of infections with this DNA virus, although preclinical studies show activity for nucleosidic compounds, such as 9-(2-phosphonylmethoxy)ethylguanine (PMEG) or cidofovir. This prompted us to test new prodrug versions of the nucleoside analog 3'-azido-2',3'-dideoxythymidine (AZT), known to be active against reverse transcriptases and approved for the treatment of HIV. Here we report the synthesis of an ethylbutyl alaninyl ester phosphosphoramidate prodrug of AZT, dubbed AZAEB, and its activity against HPV, a target not known to be sensitive to AZT. A methyl ester derivative was found to be inactive against this and three other DNA viruses, while the phosphoramidate prodrug AZAEB showed a modest inhibitory effect against HPV types 6, 11, 18 and 31. Our results open up new avenues of study for the treatment of diseases caused by members of the papillomaviridae family.

Modular Design Platform for Activatable Fluorescence Probes Targeting Carboxypeptidases Based on ProTide Chemistry

Carboxypeptidases (CPs) are a family of hydrolases that cleave one or more amino acids from the C-terminal of peptides or proteins and play indispensable roles in various physiological and pathological processes. However, only a few highly activatable fluorescence probes for CPs have been reported, and there is a need for a flexibly tunable molecular design platform to afford a range of fluorescence probes for CPs for biological and medical research. Here, we focused on the unique activation mechanism of ProTide-based prodrugs and established a modular design platform for CP-targeting florescence probes based on ProTide chemistry. In this design, probe properties such as fluorescence emission wavelength, reactivity/stability, and target CP can be readily tuned and optimized by changing the four probe modules: the fluorophore, the substituent on the phosphorus atom, the linker amino acid at the P1 position, and the substrate amino acid at the P1' position. In particular, switching the linker amino acid at position P1 enabled us to precisely optimize the reactivity for target CPs. As a proof-of-concept, we constructed probes for carboxypeptidase M (CPM) and prostate-specific membrane antigen (also known as glutamate carboxypeptidase II). The developed probes were applicable for the imaging of CP activities in live cells and in clinical specimens from patients. This design strategy should be useful in studying CP-related biological and pathological phenomena.