Elisabeth Hennes, Belén Lucas, Natalie S. Scholes, Xiu‐Fen Cheng, Daniel C. Scott, Matthias Bischoff, Katharina Reich, Raphael Gasper, María Lucas, Teng Teng Xu, Sofia Rossini, Lisa-Marie Pulvermacher, Lara Dötsch, Hana Imrichová, Alexandra Brause, Siska Führer, Kesava Reddy Naredla, Sonja Sievers, Kamal Kumar, Petra Janning, Ciriana Orabona, Malte Gersch, Peter J. Murray, Brenda A. Schulman, Georg E. Winter, Slava Ziegler, Herbert Waldmann
Abstract Targeted protein degradation modulates protein function beyond the inhibition of enzyme activity or protein–protein interactions. Most degrader drugs function by directly mediating the proximity between a neosubstrate and a hijacked E3 ligase. Here we identify pseudo-natural products derived from (−)-myrtanol, termed iDegs, that inhibit and induce degradation of the immunomodulatory enzyme indoleamine-2,3-dioxygenase 1 (IDO1) by a distinct mechanism. iDegs boost IDO1 ubiquitination and degradation by the cullin-RING E3 ligase CRL2 KLHDC3 , which we identified to natively mediate ubiquitin-mediated degradation of IDO1. Therefore, iDegs increase IDO1 turnover using the native proteolytic pathway. In contrast to clinically explored IDO1 inhibitors, iDegs reduce the formation of kynurenine by both inhibition and induced degradation of the enzyme and thus also modulate the non-enzymatic functions of IDO1. This unique mechanism of action may open up alternative therapeutic opportunities for the treatment of cancer beyond classical inhibition of IDO1.