P0150 A precision medicine approach for carriers of defined IL2RA polymorphism: JAK inhibition blocks exaggerated IL-2 signalling in vitro, with no difference in in vivo clinical response rates in a small clinical cohort
Authors: Clough J , Honap S , Centritto A , Seah D , Jayasena H , Irving P , Lord G 
Published: January 2025

Abstract

Background
The rs61839660 (660) polymorphism lies within the IL2RA intronic enhancer and is a causal variant in Crohn’s disease, with a heterozygote frequency of 16.8%. IL-2Ra (CD25) is the high-affinity receptor for IL-2, with binding activating JAK-STAT signalling. We have demonstrated that risk (T) allele carriers exhibit higher CD4+ T cell and natural killer (NK) cell CD25 expression. In response to IL-2, ‘T’ allele carriers show enhanced JAK-STAT signalling, greater CD4+ effector T cell (Teff) pro-inflammatory cytokine release, and enhanced NK cytotoxicity compared to wild-type (CC) subjects.1 We hypothesised that this drives inflammation, and that ‘T’ allele carriers would be more likely to respond to Janus kinase inhibition (JAKi).
Tofacitinib (TF) is a JAKi licensed for the treatment of UC. We examined the ability of JAKi to block IL-2-induced JAK-STAT signalling in 660 risk allele carriers in vitro, and explored clinical response to TF in a genotyped UC cohort, with the aim of understanding whether JAKi presents a personalised therapeutic approach in this population.

Methods
CD patients of each genotype were recruited in collaboration with the NIHR IBD Bioresource.2 We extracted PBMCs and flow-sorted CD4+ Teff and CD56dim NK cells. Cells were cultured for 18h in the presence/absence of 20nM TF, stimulated with IL-2, fixed, and stained for intracellular pSTAT5. TF-treated patients were identified, and provided a blood or saliva sample. Genotyping was performed by qPCR. Data were obtained from patient records, with clinical response defined as a reduction in the Simple Clinical Colitis Activity Index or Partial Mayo Score of &gt;/= 3.

Results
pSTAT5 levels were elevated in TT subjects’ Teff compared to CC/CT subjects in response to 10IU/ml IL-2 (Fig 1a), with a reduction in Teff pSTAT5 MFI in the presence of TF. In NK cells, pSTAT5 MFI was increased in TT compared to CC donors in response to 100IU/ml IL-2 (Fig 1g). The pSTAT5 response to IL-2 was non-significantly reduced in the presence of TF in both CC and TT subjects’ NK cells. In the real-world UC cohort, there was no significant difference in clinical response to TF between genotypes (Fig 2a), nor in the proportion of patients who had a disease flare on dose reduction or requiring colectomy. There was no difference in TF treatment persistence between genotypes (Fig 2b).

Conclusion
TF diminishes the in vitro pSTAT5 response to IL-2 in CD4+ Teff and NK cells in carriers of the 660 risk allele. In a UC population, there was no difference in clinical response to TF between genotype cohorts. Our data are limited by the small study population, with larger studies needed to confirm whether the use of JAKi may represent a personalised therapeutic approach in 660 risk allele carriers.

References
1.Goldberg R, Clough JN, Roberts LB, et al. A Crohn’s disease-associated IL2RA enhancer variant determines the balance of T cell immunity by regulating responsiveness to IL-2 signaling. J Crohn’s Colitis. June 2021. doi:10.1093/ecco-jcc/jjab103
2.Parkes M, IBD BioResource Investigators. IBD BioResource: an open-access platform of 25 000 patients to accelerate research in Crohn’s and Colitis. Gut. July 2019:gutjnl-2019-318835. doi:10.1136/gutjnl-2019-318835