A phase I, randomized, double-blind study to assess the safety, tolerability and efficacy of the topical RORC2 inverse agonist PF-06763809 in participants with mild-to-moderate plaque psoriasis.

BACKGROUND: Transcription factor retinoic acid-related orphan receptor 2 (RORC2/RORγT) mediates interleukin (IL)-17A and IL-17F expression. IL-17A plays a central role in the pathogenesis of several inflammatory disorders, including psoriasis. The RORC2 inhibitor PF-06763809 has been hypothesized to inhibit IL-17A production in T-helper 17 (Th17) cells, thereby reducing psoriasis symptoms. AIM: To assess the safety, tolerability and effect on skin infiltrate thickness of PF-06763809 in participants with mild/moderate chronic plaque psoriasis. METHODS: This was a randomized, double-blind, first-in-human study (trial registration: ClinicalTrials.gov NCT03469336). Participants received each of the following six treatments once daily for 18 days: three topical doses (2.3%, 0.8%, 0.23%) of PF-06763809, a vehicle and two active comparators (betamethasone and calcipotriol). Primary endpoints included change from baseline in psoriatic skin infiltrate thickness [echo-poor band (EPB) on ultrasonography] at Day 19, and safety. Change in psoriasis-associated gene expression (Day 19), evaluated by real-time reverse transcription PCR of skin biopsies, was an exploratory endpoint. RESULTS: In total, 17 participants completed the study. Change from baseline in the EPB on Day 19 for all three doses of PF-06763809 was not significantly different from that of vehicle (P > 0.05). A significant reduction in EPB from baseline was observed with betamethasone on Day 19 relative to all other treatments (P < 0.0001). Treatment-related adverse events were mild/moderate. There were no significant differences in gene expression on Day 19 between vehicle and PF-06763809-treated skin lesions. CONCLUSION: Using a psoriasis plaque test design, PF-06763809 was found to be well tolerated with an acceptable safety profile in participants with psoriasis, but without reduction in skin infiltrate thickness or disease biomarkers.

One-electron oxidation is not a major route of metabolic activation and DNA binding for the carcinogen 7H-dibenzo[c,g]carbazole in vitro and in mouse liver and lung.

7H-Dibenzo[c,g]carbazole (DBC) is a potent multi-site, multi-species carcinogen present in a variety of complex mixtures derived from the incomplete combustion of organic matter. Like many carcinogens, DBC requires metabolic activation to an electrophilic species to exert its mutagenic and carcinogenic effects. One-electron oxidation, leading to the formation of radical cation intermediates, has been proposed as a mechanism of metabolic activation for DBC in vitro resulting in unstable DNA adducts. The purpose of this research was to determine whether one-electron oxidation is a mechanism of activation and DNA binding for DBC in vivo. Specific depurinating DBC-DNA adducts formed by one-electron oxidation were analyzed in mouse liver at 4 h following a single i.p. dose of 40 mg/kg of 11 microCi [(14)C]DBC. In addition to five previously published adduct standards, two newly identified adduct standards were characterized by mass spectrometry and NMR, namely DBC-6-N7-Ade and DBC-6-N1-Ade; however, neither was observed in mouse liver. Only the DBC-5-N7-Gua adduct was observed in mouse liver extracts at a level of 6.5 +/- 1. 8 adducts/10(6) nucleotides. In addition, the formation of AP sites and stable DBC-DNA adducts was analyzed in mouse liver and lung at 4, 12 and 24 h following a single i.p. dose of 0.4, 4 or 40 mg/kg DBC (n = 3/group). There was a distinct time- and dose-response of stable DBC-DNA adducts detected by (32)P-post-labeling. There was not a clear dose-response for formation of AP sites; however, a significant increase over control levels was observed at the 4 and 40 mg/kg dose groups at 4 and 12 h post dosing, respectively. Quantitative comparisons indicate that the depurinating DBC-5-N7-Gua adduct constitutes approximately 0.4% of total adducts measured whereas the stable adducts detected by (32)P-post-labeling constitute 99.6% of total adducts measured following a 40 mg/kg dose and a 4 h time-point. The data indicate that one-electron oxidation does occur in mouse liver in vivo. However, one-electron oxidation is a minor mechanism of activation in that the percentage of total adducts formed through this route constitutes a minor percentage of the total adducts formed.

Combination of high-performance liquid chromatography and thin-layer chromatography separation of five adducted nucleotides isolated from liver resulting from intraperitoneal administration with 7H-dibenzo[c,g]carbazole to mice.

7H-Dibenzo[c,g]carbazole, DBC, is a potent environmental liver carcinogen. Liver DNA from mice treated with DBC exhibited seven distinct DBC-DNA adducts as detected by 32P-postlabeling using multidimensional TLC. To improve quantitation and chemically characterize the adducts, DNA samples were hydrolyzed, 32P-postlabeled and the adducts were separated from the unadducted normal nucleotides on TLC using a D1 solvent, 0.65 M sodium phosphate (pH 6.8). Adducts were eluted from the TLC plates with 4.0 M pyridinium formate, concentrated, resuspended in 50% aqueous methanol and injected onto the HPLC; five individual adduct peaks were resolved and collected by this method. This approach will prove useful to decrease analysis time and improve chemical characterization of tightly clustered DNA adducts generated in vivo.