Summary:The optimal approach to obtain an adequate graft for transplantation in patients with poor peripheral blood stem cell (PBSC) mobilization remains unclear. We retrospectively assessed the impact of different strategies of second-line stem cell harvest on the transplantation outcome of patients who failed PBSC mobilization in our institution. Such patients were distributed into three groups: those who proceeded to steady-state bone marrow (BM) collection (group A, n ¼ 34); those who underwent second PBSC mobilization (group B, n ¼ 41); those in whom no further harvesting was carried out (group C, n ¼ 30). PBSC harvest yielded significantly more CD34 þ cells than BM collection. Autologous transplantation was performed in 30, 23 and 11 patients from groups A, B and C, respectively. Engraftment data and transplantation outcome did not differ significantly between groups A and C. By contrast, group B patients had a faster neutrophil recovery, required less platelet transfusions and experienced less transplant-related morbidity, as reflected by lower antibiotics needs and shorter hospital stays. In conclusion, remobilization of PBSC constitutes an effective approach to ensure a rapid hematopoietic engraftment and a safe transplantation procedure for poor mobilizers, whereas unprimed BM harvest does not provide any clinical benefit in this setting.

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Immune thrombotic thrombocytopenic purpura (iTTP) is a thrombotic microangiopathy caused by anti-ADAMTS13 antibodies. Caplacizumab is approved for adults with an acute episode of iTTP in conjunction with PEX and immunosuppression. The objective of this study is to analyze and compare the safety and efficacy of caplacizumab versus the standard of care and assess the effect of the concomitant use of rituximab. A retrospective study from the Spanish TTP Registry of patients treated with caplacizumab vs those who did not receive it was conducted. A total of 155 iTTP patients (77 caplacizumab, 78 no caplacizumab) were included. Patients initially treated with caplacizumab had fewer exacerbations (4.5% vs 20.5% p<0.05) and less refractoriness (4.5% vs 14.1% p<0.05) than those that were not treated. Time to clinical response was shorter when caplacizumab was used as initial treatment vs caplacizumab used after refractoriness or exacerbation. The multivariate analysis showed that its use in the first 3 days after plasma exchange (PEX) was associated with a lower number of PEX (OR 7.5, CI 2.3-12.7; p<0.05) and days of hospitalization (OR 11.2, CI 5.6-16.9; p<0.001) compared to standard therapy. There was no difference in time to clinical remission in patients treated with caplacizumab compared to the use of rituximab. No severe adverse event was described in the caplacizumab group. In summary, caplacizumab reduced exacerbations and refractoriness compared to standard of care regimens. When administered within the first 3 days after PEX it also provided a faster clinical response, reducing hospitalization time and the need for PEX.