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Week of 28 September – 4 October 2026

What is the mechanism of action of efgartigimod and response rates in ITP?

Answer: Efgartigimod is a novel IgG1 Fc fragment that binds the neonatal Fc receptor (FcRn) with high affinity and thus reduces serum IgG concentrations, including autoantibodies.

  • FcRn protects IgG and albumin from destruction and enables the long half-lives of these circulating proteins. Blocking or augmenting FcRn can decrease autoimmune antibodies and enhance drug delivery.
  • It has been approved in Japan for the treatment of ITP based on the ADVANCE IV trial:

22% (17/78) of patients with chronic immune thrombocytopenia receiving efgartigimod reached the primary endpoint compared with 5% (2/40) of those receiving placebo (p=0·032; adjusted difference in response, 16% [95% CI 2·6–26·4])

— ADVANCE IV (Lancet 2023)

Source: Efficacy and safety of the neonatal Fc receptor inhibitor efgartigimod in adults with primary immune thrombocytopenia (ADVANCE IV): a multicentre, randomised, placebo-controlled, phase 3 trial

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Why is ruxolitinib a promising therapeutic option for patients with STAT3 gain-of-function (GOF)?

Answer: Ruxolitinib is a JAK1/2 inhibitor; by blocking JAK it prevents STAT3 phosphorylation and activation, targeting the pathway upstream of the gain-of-function defect.

STAT3 is part of the Janus kinase (JAK)/STAT pathway which is one of the most complex transcription regulators participating in a variety of physiological processes. It mediates signal transduction from the cell membrane to the nucleus in multiple intracellular and extracellular activities. Among the 7 members of the STAT protein family, STAT3 is a cytosolic protein that, upon activation by many pro-inflammatory cytokines, hormones and growth factors, is tyrosine-phosphorylated (pY705STAT3) by JAK. It then dimerizes and translocates to the nucleus to activate target genes transcription, Mcl1, c-Myc, cyclins D1 and D2, Bcl-xl among others. The STAT pathway is therefore involved in the regulation of crucial genes related to extremely widespread functions including cell proliferation, differentiation, survival, inflammation, immunity, and metastasis, thereby being central in many physiological and pathological processes.

— The constitutive activation of STAT3 gene and its mutations are at the crossroad between LGL leukemia and autoimmune disorders (Blood Cancer J 2024)

Source: The constitutive activation of STAT3 gene and its mutations are at the crossroad between LGL leukemia and autoimmune disorders

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What is considered a normal spleen size?

Answer: Spleen size is significantly influenced by body height and sex.

Use these calculators to calculate the expected size:

Source: Spleen Size Is Significantly Influenced by Body Height and Sex: Establishment of Normal Values for Spleen Size at US with a Cohort of 1200 Healthy Individuals

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