NM_001558.4(IL10RA):c.506T>C (p.Ile169Thr)

For IL10RA c.506T>C (p.Ile169Thr), a pathogenic missense variant that disrupts IL-10 receptor signaling and causes severe very-early-onset inflammatory bowel disease (VEOIBD), monoclonal antibody therapy with anti-TNFα agents (infliximab, adalimumab) and anti-IL-12/23 antibodies (ustekinumab) can provide critical disease control as a bridge to definitive curative allogeneic HSCT. While antibody therapy does not correct the underlying genetic defect, it targets the downstream inflammatory cascade driven by unopposed macrophage and T cell activation in the absence of functional IL-10 signaling.

IL-10 is a master anti-inflammatory cytokine; its receptor (IL-10RA/IL-10RB heterodimer) signals through JAK1/TYK2-STAT3 to suppress macrophage and dendritic cell proinflammatory cytokine production (TNFα, IL-1β, IL-6, IL-12, IL-23). Biallelic IL10RA loss-of-function variants cause severe colitis presenting in the first months of life, refractory to conventional immunosuppression. The p.Ile169Thr substitution affects the extracellular domain of IL-10RA, likely disrupting IL-10 ligand binding or receptor conformational signaling. Multiple case series have reported partial clinical response to infliximab (anti-TNFα) in IL10RA-deficient VEOIBD, with reduction in bloody diarrhea, fistulae, and inflammatory markers (Glocker et al., NEJM 2009; PMID:19890111; Kotlarz et al., Gastroenterology 2012; PMID:22902955). Ustekinumab (anti-IL-12/23 p40 subunit) has been used in refractory cases, targeting the Th1/Th17 axis that is overactivated when IL-10 suppression fails. However, long-term remission requires HSCT to replace the defective hematopoietic cells with donor-derived immune cells expressing functional IL-10RA.

Antibody therapy is palliative, not curative — it does not restore IL-10 signaling. Responses are often partial and wane over time, with frequent need for dose escalation or switching agents. Anti-TNFα therapy carries risks of serious infections (opportunistic infections, tuberculosis reactivation) particularly concerning in infants who are already immunocompromised by their primary immunodeficiency. Immunogenicity (anti-drug antibody formation) limits long-term efficacy of infliximab and adalimumab. The definitive treatment is allogeneic HSCT, which has shown high cure rates (~80-90% event-free survival) when performed early, but carries its own transplant-related mortality and morbidity. Antibody therapy data for IL10RA-VEOIBD come from small case series and case reports — no randomized controlled trials exist for this ultra-rare condition. The specific effect of the p.Ile169Thr variant on antibody therapy response has not been studied.

Base Editing (BE4max) via RNP electroporation (ex vivo) delivery is a rationale-driven therapeutic strategy for Monogenic very-early-onset inflammatory bowel disease due to IL10RA deficiency targeting the IL10RA c.506T>C (p.Ile169Thr) variant (Pathogenic, missense variant, non-coding transcript variant). The editing system (BE4max (cytosine base editor)) converts the pathogenic C to T (or G to A on the target strand), restoring the wild-type codon. Target tissue: Blood/HSC. Therapeutic goal: Correct biallelic loss-of-function variants in IL10RA at the intestinal immune-cell and epithelial-cell loci to restore IL-10 signalling and achieve permanent remission of very-early-onset inflammator. Risk profile: off-target Medium (bystander bases in editing window), delivery complexity Medium, immunogenicity Low.

1. Molecular basis: IL10RA NM_001558.4(IL10RA):c.506T>C (p.Ile169Thr) is classified as Pathogenic (ClinVar variation ID 943905). Molecular consequence: missense variant, non-coding transcript variant. Protein change: I169T. 2. Epidemiology: IL10RA-deficient very-early-onset IBD is an ultra-rare autosomal recessive monogenic form of inflammatory bowel disease, typically presenting in the first months of life with severe enterocolitis, perianal disease, and failure to thrive. Cohort and regional data suggest that monogenic VEO-IBD consti 3. Standard of care: Conventional IBD therapies (steroids, immunomodulators, biologics such as anti-TNF or vedolizumab) rarely induce sustained remission in IL10RA-deficient VEO-IBD; most patients remain dependent on parenteral nutrition, have persistent disease activity, and often require surgery. Multiple cohort studi 4. Pipeline: For IL10RA/B monogenic IBD, there are currently no registered in vivo gene therapy or gene-editing clinical trials identified in public registries; HSCT is used as a standard curative cellular therapy in specialized centers. Gene therapy and gene editing for intestinal and immune targets are at prec 5. CBE clinical validation: BE4max (Koblan et al. 2018) is the gold-standard cytosine base editor. Multiple CBE programs are in clinical development for liver and hematologic targets.

1. No published data specifically correcting IL10RA c.506T>C (p.Ile169Thr) with Base Editing (BE4max); strategy is based on general principles and must be validated preclinically. 2. PAM availability and bystander base analysis for the specific genomic context have not been performed. If no canonical NGG PAM positions the target within the editing window, PAM-flexible variants (SpRY) may be needed. 3. Long-term durability, off-target genome-wide effects, and immunogenicity in the target patient population require thorough preclinical and clinical evaluation.