High infliximab trough concentrations are associated with sustained histologic remission in inflammatory bowel disease: a prospective cohort study.

BACKGROUND: The threshold concentration of infliximab during maintenance therapy has not been well-defined in relation to histologic remission. The aim of the study is to dentify the maintenance-phase infliximab concentration associated with histologic remission in inflammatory bowel disease patients (IBD). METHODS: A prospective cohort study was carried out in 104 IBD patients seen at a tertiary care centre in London, Canada. Infliximab trough concentrations were collected during the maintenance phase of treatment and compared between participants with and without evidence of histologic remission. Participants were additionally evaluated for sustained histologic remission, and relapse to active disease. RESULTS: Participants in histologic remission attained higher mean concentrations of infliximab during the maintenance phase (10.34 ± 0.69 µg/ml) compared to those with persistent disease activity (6.23 ± 0.67 µg/ml, p-value < 0.0001). Additionally, during the maintenance phase, sustained histologic remission was also associated with a higher mean concentration of infliximab (10.81 ± 5.46 µg/ml) compared to those who relapsed to active disease (5.68 ± 3.70, p < 0.001). Overall, participants with a mean infliximab trough concentration greater than 8ug/ml were more likely to have histologic remission (area under the receiver operating characteristic curve, AUROC = 0.72, 95%CI = 0.65-0.84, p < 0.0001) and sustained histologic remission (AUC = 0.77, 95%CI = 0.63-0.91, p = 0.002). CONCLUSION: Maintenance-phase infliximab trough concentrations greater than 8 µg/ml, which is higher than the currently recommended target concentration, are highly associated with histologic remission and sustained histologic remission.

Decreased Infliximab Concentrations in Patients With Inflammatory Bowel Disease Who Carry a Variable Number Tandem Repeat Polymorphism in the Neonatal Fc Receptor or Variant HLADQA1*05G>A Genotype.

BACKGROUND: Multiple variables contribute to variation in patient exposure and response to tumor necrosis factor alpha antagonist biologics such as infliximab. This study aimed to assess the association between maintenance-phase infliximab concentrations and genetic variation in HLADQA1*05G>A and fragment crystallisable (Fc) fragment of IgG receptor and transporter (FCGRT) among patients with inflammatory bowel disease. METHODS: A cross-sectional study was carried out in participants with inflammatory bowel disease prescribed infliximab who were in the maintenance phase of treatment. Participants were genotyped for the presence of the FCGRT variable number tandem repeat (VNTR) and HLADQA1*05G>A (rs74291249). A point estimate of the infliximab trough concentration during the maintenance phase was determined using a standard enzyme-linked immunosorbent assay for each patient. Other variables associated with infliximab pharmacokinetics were collected. RESULTS: A total of 156 participants with inflammatory bowel disease were included from 2 tertiary care centers affiliated with Western University, London, Canada. Median infliximab trough concentrations were lower in participants who carried the FCGRT VNTR 2/3 or 2/2 (4.14 µg/mL; interquartile range [IQR], 6.48 µg/mL) vs wild type individuals (7.00 µg/mL; IQR, 7.66; P = .0027). Median infliximab trough concentrations were significantly lower in participants who were HLADQA1*05G>A variant carriers (4.73µg/mL; IQR, 4.79) vs wild type individuals (7.85µg/mL; IQR, 7.44; P = .0006). A significant decrease in infliximab trough concentrations was seen in individuals who were dual carriers of variant polymorphisms in HLADQA1*05G>A and FCGRT VNTR (no variants, 8.96µg/mL; IQR, 6.84 vs one variant, 4.96 µg/mL; IQR, 4.95 vs dual variants, 0.86µg/mL; IQR, 5.82). CONCLUSION: FCGRT VNTR and HLADQA1*05G>A are associated with lower maintenance-phase infliximab concentrations, particularly among patients who carry both variants.

HLADQA1*05G>A and FCGRT VNTR are associated with lower maintenance-phase infliximab concentrations, particularly among patients who carry both variants.

CIC protein instability contributes to tumorigenesis in glioblastoma.

Capicua (CIC) is a transcriptional repressor that counteracts activation of genes downstream of receptor tyrosine kinase (RTK)/Ras/ERK signaling. It is well-established that tumorigenesis, especially in glioblastoma (GBM), is attributed to hyperactive RTK/Ras/ERK signaling. While CIC is mutated in other tumors, here we show that CIC has a tumor suppressive function in GBM through an alternative mechanism. We find that CIC protein levels are negligible in GBM due to continuous proteasome-mediated degradation, which is mediated by the E3 ligase PJA1 and show that this occurs through binding of CIC to its DNA target and phosphorylation on residue S173. PJA1 knockdown increased CIC stability and extended survival using in-vivo models of GBM. Deletion of the ERK binding site resulted in stabilization of CIC and increased therapeutic efficacy of ERK inhibition in GBM models. Our results provide a rationale to target CIC degradation in Ras/ERK-driven tumors, including GBM, to increase efficacy of ERK inhibitors.