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.     

Targeting stents with local delivery of paclitaxel-loaded magnetic nanoparticles using uniform fields

The use of stents for vascular disease has resulted in a paradigm shift with significant improvement in therapeutic outcomes. Polymer-coated drug-eluting stents (DES) have also significantly reduced the incidence of reobstruction post stenting, a disorder termed in-stent restenosis. However, the current DESs lack the capacity for adjustment of the drug dose and release kinetics to the disease status of the treated vessel. We hypothesized that these limitations can be addressed by a strategy combining magnetic targeting via a uniform field-induced magnetization effect and a biocompatible magnetic nanoparticle (MNP) formulation designed for efficient entrapment and delivery of paclitaxel (PTX). Magnetic treatment of cultured arterial smooth muscle cells with PTX-loaded MNPs caused significant cell growth inhibition, which was not observed under nonmagnetic conditions. In agreement with the results of mathematical modeling, significantly higher localization rates of locally delivered MNPs to stented arteries were achieved with uniform-field–controlled targeting compared to nonmagnetic controls in the rat carotid stenting model. The arterial tissue levels of stent-targeted MNPs remained 4- to 10-fold higher in magnetically treated animals vs. control over 5 days post delivery. The enhanced retention of MNPs at target sites due to the uniform field-induced magnetization effect resulted in a significant inhibition of in-stent restenosis with a relatively low dose of MNP-encapsulated PTX (7.5 μg PTX/stent). Thus, this study demonstrates the feasibility of site-specific drug delivery to implanted magnetizable stents by uniform field-controlled targeting of MNPs with efficacy for in-stent restenosis.     

In vivo CD40 ligation can induce T-cell-independent antitumor effects that involve macrophages

We have previously demonstrated T cell-independent antitumor and antimetastatic effects of CD40 ligation that involved natural killer (NK) cells. As CD40 molecules are expressed on the surface of macrophages (Mphi), we hypothesized that Mphi may also serve as antitumor effector cells when activated by CD40 ligation. Progression of subcutaneous NXS2 murine neuroblastomas was delayed significantly by agonistic CD40 monoclonal antibody (anti-CD40 mAb) therapy in immunocompetent A/J mice, as well as in T and B cell-deficient severe combined immunodeficiency (SCID) mice. Although NK cells can be activated by anti-CD40 mAb, anti-CD40 mAb treatment also induced a significant antitumor effect in SCID/beige mice in the absence of T and NK effector cells, even when noncytolytic NK cells and polymorphonuclear cells (PMN) were depleted. Furthermore, in vivo treatment with anti-CD40 mAb resulted in enhanced expression of cytokines and cell surface activation markers, as well as Mphi-mediated tumor inhibition in A/J mice, C57BL/6 mice, and SCID/beige mice, as measured in vitro. A role for Mphi was shown by reduction in the antitumor effect of anti-CD40 mAb when Mphi functions were inhibited in vivo by silica. In addition, activation of peritoneal Mphi by anti-CD40 mAb resulted in survival benefits in mice bearing intraperitoneal tumors. Taken together, our results show that anti-CD40 mAb immunotherapy of mice can inhibit tumor growth in the absence of T cells, NK cells, and PMN through the involvement of activated Mphi.     

Temperature sensitivity of human perforin mutants unmasks subtotal loss of cytotoxicity,delayed FHL,and a predisposition to cancer

The pore-forming protein perforin is critical for defense against many human pathogens and for preventing a catastrophic collapse of immune homeostasis, manifested in infancy as Type 2 familial hemophagocytic lymphohistiocytosis (FHL). However, no evidence has yet linked defective perforin cytotoxicity with cancer susceptibility in humans. Here, we examined perforin function in every patient reported in the literature who lived to at least 10 years of age without developing FHL despite inheriting mutations in both of their perforin (PRF1) alleles. Our analysis showed that almost 50% of these patients developed at least 1 hematological malignancy in childhood or adolescence. The broad range of pathologies argued strongly against a common environmental or viral cause for the extraordinary cancer incidence. Functionally, what distinguished these patients was their inheritance of PRF1 alleles encoding temperature-sensitive missense mutations. By contrast, truly null missense mutations with no rescue at the permissive temperature were associated with the more common severe presentation with FHL in early infancy. Our study provides the first mechanistic evidence for a link between defective perforin-mediated cytotoxicity and cancer susceptibility in humans and establishes the paradigm that temperature sensitivity of perforin function is a predictor of FHL severity.     

Dietary energy restriction-induced modulation of protein kinase C ζ isozyme in the hamster pancreas

Dietary restriction in experimental animals enhances life span, delays disease, inhibits immunological perturbations, and ameliorates cancer. Protein kinase C(a) isozymes mediate signals generated by hormones, growth factors, and neurotransmitters for cell proliferation and differentiation. The results of our study showed that a C-terminally directed anti-PKC ζ antibody detected an 81–kDa band in the pancreases of control and energy-restricted hamsters. Syrian golden hamsters were fed energy-restricted diets formulated such that the hamsters received 90%(10% energy restriction(a) ), 80%(20% ER), or 60%(40% ER) of the total energy consumed by control hamsters, with the energy reduced proportionally from fat and carbohydrate. ER decreased PKC ζ isozyme levels by 40–75% in hamsters fed 10, 20, and 40% ER diets for 8 wk. PKC ζ isozyme expression was decreased by 75–80% in hamsters fed ER diets for 15 wk. Although ER caused significant decreases in PKC ζ isozyme levels compared with those of control hamsters at both time points, the relative differences in PKC ζ levels between the dietary ER groups(10, 20, and 40%) were small and not significant. A significant decrease in the body weights of ER animals compared with those of controls was observed at both time points. No differences in tomato lectin and phytohemagglutinin reactivity were observed between control animals and animals fed 10, 20, and 40% ER diets. Furthermore, the cellular expression of PKC ζ in the hamster pancreas did not differ among hamsters fed the various ER diets. These observations may be important for understanding not only the role of dietary ER in pancreatic cancers but also PKC ζ signal transduction mechanisms in normal pancreatic physiology.© 1995 Wiley-Liss, Inc     

Aziridines and aziridinium ions in the practical synthesis of pharmaceutical intermediates--a perspective

Recent methods for the synthesis of aziridines and aziridinium ions, the mechanisms of their nucleophilic ring-opening reactions and applications to the practical synthesis of pharmaceutical intermediates are reviewed.