Real world evidence from the UK ITP Registry on the effectiveness of the immunosuppressive therapies rituximab and mycophenolate mofetil in immune thrombocytopenia

Immune thrombocytopenia (ITP) is a rare condition characterised by thrombocytopenia and variable bleeding severity. After acute management with steroids and intravenous immunoglobulin (IVIG), next line medical therapies include thrombopoietin receptor agonists, immunosuppressive therapy (e.g. rituximab, mycophenolate mofetil (MMF) and fostamatinib. There is limited evidence for comparative efficacy between different treatment modalities. The
UK ITP registry is a national registry of primary ITP, capturing demographics, clinical features, treatments and comorbidities with 4402 participants as of July 2021. We analysed data from the UK adult ITP registry to assess
responses to rituximab and MMF therapy. All patients entered into the registry from 1st January 2010 were included in this analysis. Internationally recognised definitions of response based on platelet count were used: partial response (PR)
platelets >30 x109 /L and double baseline, complete response (CR) platelets >100 x109 /L; No response – absence of CR and PR. In addition, we reviewed use of rescue therapy and use of additional therapies following treatment. A total of 844 patients were included in the analysis (486 received rituximab and 358 received MMF from 2010): median number of lines of prior treatment 2 (range 1-9) for rituximab and 2 (range 1-10) for MMF. Co-therapies at the time (and within 4 weeks) of commencing rituximab: prednisolone 26%, IVIG 11%, dexamethasone 3%, MMF 3%, romiplostim 3% and eltrombopag 2%. Co-therapies at the time (and within 4 weeks) of commencing MMF: prednisolone 39%, IVIG 13%, dexamethasone 4%, rituximab 4%, romiplostim 6% and eltrombopag 4%. The percentage of patients achieving platelet response at each time response (with denominator) are listed in table 1. Of those receiving rituximab with baseline
platelets <30 x109 /L at starting therapy, 48% had at least PR by 4 weeks, 59.9% at 12 weeks, 63% at 6 months and 77% at 12 months. For MMF, these percentages were 41.5%, 55.2%, 58.8 and 70% respectively, however, the numbers of patients in the MMF group were lower. The median duration of response was 44 weeks for rituximab and 27 weeks for MMF. Where new therapies were required, the median number of weeks until therapy was switched was 18 weeks for rituximab and 15 weeks for MMF. 77% patients and 81% patients who received rituximab and MMF respectively changed treatment during their follow up. Overall 284 (58%) patients received rescue medication during follow up, of those that received MMF 234 (65%) received rescue medication. The main rescue therapies were prednisolone (589 episodes in rituximab group and 520 in MMF group) and IVIG (482 in rituximab group and 321 in MMF group). In conclusion, this is one of the first studies, using real world data and long term follow up, to compare outcomes after immunosuppression.