Phosphinophosphonates and Their Tris-pivaloyloxymethyl Prodrugs Reveal a Negatively Cooperative Butyrophilin Activation Mechanism.

Rebekah R Shippy, Xiaochen Lin, Sherry S Agabiti, Jin Li, Brendan M Zangari, Benjamin J Foust, Michael M Poe, Chia-Hung Christine Hsiao, Olga Vinogradova, David F Wiemer, Andrew J Wiemer

Journal of medicinal chemistry 2017 Mar 23

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Butyrophilin 3A1 (BTN3A1) binds small phosphorus-containing molecules, which initiates transmembrane signaling and activates butyrophilin-responsive cells. We synthesized several phosphinophosphonates and their corresponding tris-pivaloyloxymethyl (tris-POM) prodrugs and examined their effects on BTN3A1. An analog of (E)-4-hydroxy-3-methyl-but-2-enyl diphosphate (HMBPP) bound to BTN3A1 with intermediate affinity, which was enthalpy-driven. Docking studies revealed binding to the basic surface pocket and interactions between the allylic hydroxyl group and the BTN3A1 backbone. The phosphinophosphonate stimulated proliferation of Vγ9Vδ2 T cells with moderate activity (EC50 = 26 μM). Cellular potency was enhanced >600-fold in the tris-POM prodrug (EC50 = 0.041 μM). The novel prodrug also induced T cell mediated leukemia cell lysis. Analysis of dose-response data reveals HMBPP-induced Hill coefficients of 0.69 for target cell lysis and 0.68 in interferon secretion. Together, tris-POM prodrugs enhance the cellular activity of phosphinophosphonates, reveal structure-activity relationships of butyrophilin ligands, and support a negatively cooperative model of cellular butyrophilin activation.

Citation

Rebekah R Shippy, Xiaochen Lin, Sherry S Agabiti, Jin Li, Brendan M Zangari, Benjamin J Foust, Michael M Poe, Chia-Hung Christine Hsiao, Olga Vinogradova, David F Wiemer, Andrew J Wiemer. Phosphinophosphonates and Their Tris-pivaloyloxymethyl Prodrugs Reveal a Negatively Cooperative Butyrophilin Activation Mechanism. Journal of medicinal chemistry. 2017 Mar 23;60(6):2373-2382