Safety,tolerability, pharmacokinetics,and pharmacodynamics of a TLR7 agonist prodrug RO6870868 in healthy volunteers

RO6870868 is an oral prodrug of the toll‐like receptor 7 (TLR7) specific agonist, RO6871765. TLR7 agonists augment host immune activity and are in development to treat hepatitis B infection. We evaluated the safety, tolerability, pharmacokinetics (PKs), and pharmacodynamics (PDs) of RO6870868 in a first‐in‐human, phase I, randomized, single ascending oral dose study in 60 healthy volunteers at 6 dose levels (200–2000 mg). Single oral doses were generally well‐tolerated with a predictable safety profile associated with dose‐dependent increases in systemic interferon. No serious adverse events (AEs) were reported and no subject withdrew from the study due to an AE. No clinically significant changes were observed in vital signs, electrocardiograms, or laboratory parameters. Following oral RO6870868 doses, plasma RO6871765 concentrations increased rapidly, exhibiting mean terminal half‐life ranging 2–6 h across all cohorts, with area under the plasma concentration versus time curve extrapolated to infinity (AUC_0‐∞) increasing proportionally with dose. A pattern of dose and time‐dependent PD activity was demonstrated consistent with engagement of the TLR7 system. Single RO6870868 doses activated components of the TLR innate immune system in a dose‐dependent manner with adequate safety and tolerability. Single‐dose data in healthy volunteers are useful to evaluate safety, PK, and PD activity of TLR7 agonists and help to guide dose and regimen selection for further trials in patients with chronic hepatitis B.

Study Highlights

• WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC?

Toll‐like receptor 7 (TLR7) agonists induce broad immune‐enhancing effects and may play a role in overcoming the adaptive and innate immune defects in chronic hepatitis B infection.

• WHAT QUESTION DID THIS STUDY ADDRESS?

The safety, tolerability, pharmacokinetics, and pharmacodynamics of single oral doses of RO6870868 (a prodrug of the specific TLR7 agonist RO6871765) in healthy volunteers.

• WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE?

RO6870868 was safe and acceptably tolerated across the dose range in healthy volunteers. Oral administration results in the rapid appearance of the active TLR7 agonist RO6871765 and leads to a profile of gene expression typical for TLR7 agonism, including activation of interferon and interferon‐response genes. Gene activation occurs at RO6871765 exposure associated with single RO6870868 doses greater than or equal to 800 mg, with a plateau for several markers at doses between 1200 mg and 1600 mg.

• HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE?

The study results help to guide dose and regimen selection for clinical trials with RO6870868 and other potent TLR7 activators.