Tofacitinib as monotherapy following methotrexate withdrawal in patients with psoriatic arthritis previously treated with open-label tofacitinib plus methotrexate: a randomised, placebo-controlled substudy of OPAL Balance.

BACKGROUND: Tofacitinib is an oral Janus kinase inhibitor for the treatment of psoriatic arthritis, rheumatoid arthritis, and ulcerative colitis. This study evaluated the efficacy and safety of tofacitinib 5 mg twice daily monotherapy after methotrexate withdrawal. METHODS: OPAL Balance was an open-label, long-term extension study of tofacitinib in patients with psoriatic arthritis who participated in the OPAL Broaden and OPAL Beyond phase 3 studies. This 12-month, randomised, double-blind, placebo-controlled, methotrexate withdrawal substudy (50 centres, 14 countries) included patients from OPAL Balance who completed tofacitinib treatment for 24 months or more (≥3 months' stable tofacitinib 5 mg twice daily) and were receiving methotrexate (7·5-20 mg/week). Patients were blindly randomised (1:1) using interactive response technology and received open-label tofacitinib 5 mg twice daily with either placebo (tofacitinib 5 mg twice daily plus placebo group) or continued methotrexate (tofacitinib 5 mg twice daily plus methotrexate group). Patients were masked to placebo or methotrexate, with identical capsules used. Coprimary endpoints were changes from substudy baseline in psoriatic arthritis disease activity score (PASDAS) and health assessment questionnaire-disability index (HAQ-DI) at month 6 in all randomised patients with one or more substudy drug dose. Safety was assessed throughout. No specific statistical hypothesis (either superiority or non-inferiority) was tested. The study (OPAL Balance) is registered with ClinicalTrials.gov (NCT01976364) and is complete. FINDINGS: Between Oct 30, 2017, and May 20, 2019, 180 patients from OPAL Balance who were eligible for the substudy were randomly assigned to treatment (90 patients received tofacitinib 5 mg twice daily plus placebo and 89 patients assigned to tofacitinib plus methotrexate; one patient was not treated because of randomisation error). At month 6, least squares mean (LSM) changes in PASDAS were 0·23 (SE 0·08) for tofacitinib 5 mg twice daily plus placebo and 0·14 (0·08) for tofacitinib 5 mg twice daily plus methotrexate (treatment difference LSM 0·09 [95% CI -0·13 to 0·31]), and changes in HAQ-DI were 0·04 (0·03) and 0·02 (0·03), respectively (treatment difference 0·03 [-0·05 to 0·10]). Rates of adverse events, discontinuations because of adverse events, adverse events of special interest, and laboratory changes were generally similar between treatment groups, although liver enzyme elevations were more common with tofacitinib 5 mg twice daily plus methotrexate than tofacitinib 5 mg twice daily plus placebo. Flares of worsening symptoms was reported in one (1%) of 90 patients in the tofacitinib 5 mg twice daily plus placebo group (recorded as psoriatic arthropathy). INTERPRETATION: Some patients with psoriatic arthritis who are stable on tofacitinib 5 mg twice daily with background methotrexate might be able to discontinue methotrexate without clinically meaningful changes in disease activity and safety. FUNDING: Pfizer Inc.

Effects of the microtubule nucleator Mto1 on chromosomal movement, DNA repair, and sister chromatid cohesion in fission yeast.

Although the function of microtubules (MTs) in chromosomal segregation during mitosis is well characterized, much less is known about the role of MTs in chromosomal functions during interphase. In the fission yeast Schizosaccharomyces pombe, dynamic cytoplasmic MT bundles move chromosomes in an oscillatory manner during interphase via linkages through the nuclear envelope (NE) at the spindle pole body (SPB) and other sites. Mto1 is a cytoplasmic factor that mediates the nucleation and attachment of cytoplasmic MTs to the nucleus. Here, we test the function of these cytoplasmic MTs and Mto1 on DNA repair and recombination during interphase. We find that mto1Δ cells exhibit defects in DNA repair and homologous recombination (HR) and abnormal DNA repair factory dynamics. In these cells, sister chromatids are not properly paired, and binding of Rad21 cohesin subunit along chromosomal arms is reduced. Our findings suggest a model in which cytoplasmic MTs and Mto1 facilitate efficient DNA repair and HR by promoting dynamic chromosomal organization and cohesion in the nucleus.

Proteome-wide search for PP2A substrates in fission yeast.

PP2A (protein phosphatase 2A) is a major phosphatase in eukaryotic cells that plays an essential role in many processes. PP2A mutations in Schizosaccharomyces pombe result in defects of cell cycle control, cytokinesis and morphogenesis. Which PP2A substrates are responsible for these changes is not known. In this work, we searched for PP2A substrates in S. pombe using two approaches, 2D-DIGE analysis of PP2A complex mutants and identification of PP2A interacting proteins. In both cases, we used MS to identify proteins of interest. In the DIGE experiment, we compared proteomes of wild-type S. pombe, deletion of pta2, the phosphoactivator of the PP2A catalytic subunit, and pab1-4, a mutant of B-type PP2A regulatory subunit. A total of 1742 protein spots were reproducibly resolved by 2D-DIGE and 51 spots demonstrated significant changes between PP2A mutants and the wild-type control. MS analysis of these spots identified 27 proteins that include key regulators of glycerol synthesis, carbon metabolism, amino acid biosyntesis, vitamin production, and protein folding. Importantly, we independently identified a subset of these proteins as PP2A binding partners by affinity precipitation, suggesting they may be direct targets of PP2A. We have validated our approach by demonstrating that phosphorylation of Gpd1, a key enzyme in glycerol biogenesis, is regulated by PP2A and that ability of cells to respond to osmotic stress by synthesizing glycerol is compromised in the PP2A mutants. Our work contributes to a better understanding of PP2A function and identifies potential PP2A substrates.