Role of azathioprine in the management of ITP in the TPO-RA era: a single-center retrospective study.

Access to modern therapeutics for immune thrombocytopenia (ITP), such as thrombopoietin-receptor agonists (TPO-RAs), remains a challenge, limiting clinicians' options. We investigated azathioprine in relapsed/refractory ITP to determine its efficacy and safety, focusing on evaluating its utility in post-TPO-RA patients. We retrospectively reviewed all adult patients, aged ≥18 years, who were worked up for thrombocytopenia between 2009 and 2022 at a tertiary care center in Ontario, Canada. Only patients with ITP treated with azathioprine were included. We identified 92 patients with ITP who received azathioprine, with a mean age of 55.6 ± 22.3 years; 53 were females and 39 males, with 64 having primary ITP. The overall response rate (ORR) was 47.8% (44/92), with a sustained response rate of 77.3% (34/44) at 6 months. The median time to response was 6 weeks. Fourteen patients (31.8%) relapsed, with a median duration of response of 10 weeks. Most patients (73.9%) had documented side effects, with nausea/vomiting, infections, and myelosuppression being the most common. The majority of patients received azathioprine as third-line therapy; 6 patients after TPO-RA and 27 after splenectomy. ORR was 50.0% (3/6) and 40.7% (11/27) in each group, respectively. This is the largest retrospective study, to our knowledge, demonstrating benefit with azathioprine in relapsed/refractory ITP. Its efficacy remains consistent both after TPO-RA ( = .948) and after splenectomy ( = .259), offering clinicians a comparable drug response irrespective of prior TPO-RA exposure or splenectomy. We propose that azathioprine remains a viable option for relapsed/refractory ITP in the TPO-RA era.