Distinct immunological activation profiles of dSLIM???? and ProMune???? depend on their different structural context

摘要

Abstract Introduction DNA-based TLR9 agonists are potent activators of the immune system. ProMune???? and dSLIM???? belong to different families of TLR9 agonists and both have been established as cancer immunotherapeutics in clinical proof-of-concept studies. Unfortunately, ProMune???? failed in pivotal oncological trials. dSLIM????, the active ingredient of Lefitolimod (MGN1703), successfully finished a double-blinded, placebo-controlled phase II study in patients with advanced colorectal cancer, exhibiting improved progression-free survival and durable disease control. Methods To explain the different systemic efficacies of dSLIM???? and ProMune????, both TLR9 agonists and chimeric molecules thereof are analyzed side-by-side in a panel of in vitro assays for immune activation. Results and conclusions Indeed, dSLIM???? exposure results in an IFN-???± dependent broad activation of immune cells whereas ProMune???? strongly stimulates B cells. Moreover, all functional effects of dSLIM???? strictly depend on the presence of CG-motifs within its dumbbell-shaped, covalently closed structural context. Conversely, several immunological effects of ProMune???? like IL-8 secretion are independent of CG-motifs and could be ascribed to the phosphorothioate-modifications of its DNA backbone, which may have caused the side effects of ProMune???? in clinical trials. Finally, we showed that the implementation of ProMune???? (ODN2006) base sequence into the characteristic dSLIM???? dumbbell form resulted in dSLIM2006 with all beneficial effects for immunostimulation combined from both TLR9 classes without any CG-independent effects.