Integrated Preclinical Photosafety Testing Strategy for Systemically Applied Pharmaceuticals

Phototoxic properties of systemically applied pharmaceuticals may be the cause of serious adverse drug reactions. Therefore, a reliable preclinical photosafety assessment strategy, combining in vitro and in vivo approaches in a quantitative manner, is important and has not been described so far. Here, we report the establishment of an optimized modified murine local lymph node assay (LLNA), adapted for phototoxicity assessment of systemically applied compounds, as well as the test results for 34 drug candidates in this in vivo photo-LLNA. The drug candidates were selected based on their ability to absorb ultraviolet/visible light and the photo irritation factors (PIFs) determined in the well-established in vitro 3T3 neutral red uptake phototoxicity test. An in vivo phototoxic potential was identified for 13 of these drug candidates. The use of multiple dose levels in the described murine in vivo phototoxicity studies enabled the establishment of no- and/or lowest-observed-adverse-effect levels (NOAELs/LOAELs), also supporting human photosafety assessment. An in vitro-in vivo correlation demonstrated that a drug candidate classified as "phototoxic" in vitro is not necessarily phototoxic in vivo. However, the probability for a drug candidate to cause phototoxicity in vivo clearly correlated with the magnitude of the phototoxicity identified in vitro

First-in-human study of safety, pharmacokinetics, and pharmacodynamics of MHV370, a dual inhibitor of Toll-like receptors 7 and 8, in healthy adults

Background and Objective: MHV370, a dual antagonist of human Toll-like receptors (TLR) 7 and 8, suppresses cytokines and interferon stimulated genes in vitro and in vivo, and demonstrates efficacy in murine models of lupus. This first-in-human study aimed to evaluate the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of single and multiple doses of MHV370, in healthy adults, as well as the effects of food consumption on a single dose of MHV370. Methods: This was a Phase 1, first-in-human, randomised, placebo-controlled study conducted in 3 parts. In study Part A, participants received (3:1) a single ascending dose (SAD) of 1, 3, 10, 20, 40, 80, 160, 320, 640, and 1000 mg MHV370 or placebo. In study Part B, participants received (3:1) multiple ascending doses (MAD) of 25, 50, 100, 200, and 400 mg MHV370 twice daily or placebo, for 14 days. In study Part C, participants received an open-label single dose of 200 mg MHV370 under fasted or fed conditions. Safety, PK, and PD parameters were evaluated. Results: MHV370 was well tolerated, and no safety signal was observed in the study. No dose limiting adverse events occurred across the dose range evaluated. Plasma concentrations of MHV370 increased with dose. The intake of food did not have an impact on the PK of MHV370. PD data indicated a time- and dose-dependent inhibition of TLR7-mediated CD69 expression on B cells and TLR8-mediated TNF release, after ex-vivo stimulation. Conclusion: The safety, PK and PD data support the further development of MHV370 in systemic autoimmune diseases driven by overactivation of TLR7 and TLR8

Reduced activity of sphingosine-1-phosphate lyase Induces podocyte-related glomerular proteinuria, skin Irritation, and platelet activation

Sphingosine-1-phosphate (S1P) lyase is considered as a drug target in autoimmune diseases based on the protective effect of reducing activity of the enzyme in animal models of inflammation. Since S1P lyase deficiency in mice causes a severe, lethal phenotype, it was of interest to investigate any pathological alterations associated with only partially reduced activity of S1P lyase as may be encountered upon pharmacological inhibition. Both genetic reduction of S1P lyase activity in mice and inhibition of S1P lyase with a low-molecular-weight compound in rats consistently resulted in podocyte-based kidney toxicity, which is the most severe finding. In addition, skin irritation and platelet activation were observed in both instances. The similarity of the findings in both the genetic model and the pharmacological study supports the value of analyzing inducible partially target-deficient mice for safety assessment. If the findings described in rodents translate to humans, target-related toxicity, particularly podocyte dysfunction, may limit chronic systemic treatment of autoimmune diseases with S1P lyase inhibitors. Furthermore, partial deficiency or inhibition of S1P lyase appears to provide an in vivo rodent model to enable studies on the mechanism of podocyte dysfunction

Retinoic-acid-orphan-receptor C inhibition suppresses Th17 cells and induces thymic aberrations

Retinoic-acid-orphan-receptor-C (RORC) is a master regulator of Th17 cells which are pathogenic in several autoimmune diseases. Genetic Rorc deficiency in mice, while preventing autoimmunity, causes early lethality due to metastatic thymic T cell lymphomas. We sought to determine whether pharmacological RORC inhibition could be an effective and safe therapy for autoimmune diseases by evaluating its effects on Th17 cell functions and intrathymic T cell development. RORC inhibitors effectively inhibited Th17 differentiation and IL-17A production, and delayed-type hypersensitivity reactions. In vitro, RORC inhibitors induced apoptosis, as well as Bcl2l1 and BCL2L1 mRNA downregulation, in mouse and nonhuman primate thymocytes, respectively. Chronic, 13-week RORC inhibitor treatment in rats caused progressive thymic alterations in all analyzed rats similar to those in Rorc-deficient mice prior to T cell lymphoma development. One rat developed thymic cortical hyperplasia with preneoplastic features, including increased mitosis and reduced IKAROS expression, albeit without skewed T cell clonality. In summary, pharmacological inhibition of RORC not only blocks Th17 cell development and related cytokine production, but also recapitulates thymic aberrations seen in Rorc-deficient mice. While RORC inhibition may offer an effective therapeutic principle for Th17-mediated diseases, T cell lymphoma with chronic therapy remains an apparent risk