Successful management of refractory immune-mediated thrombotic thrombocytopenic purpura during pregnancy and delivery using the anti-VWF nanobody caplacizumab.

Pregnancy is a potential trigger of acute thrombotic thrombocytopenic purpura (TTP). The management of pregnancy-associated immune-mediated TTP (iTTP) can be challenging, especially when it is refractory to standard treatment. Caplacizumab, a nanobody to von Willebrand factor (VWF) blocking its A1 domain, is a valuable new therapeutic option. Its use is, however, not approved during pregnancy and breastfeeding. We describe the successful off-label administration of caplacizumab during pregnancy and delivery in a patient with refractory iTTP. The favourable outcome without significant thrombotic or haemorrhagic complications indicates that caplacizumab may be an effective and safe treatment option in refractory iTTP during pregnancy.

Targeted Large-Volume Lymphocyte Removal Using Magnetic Nanoparticles in Blood Samples of Patients with Chronic Lymphocytic Leukemia: A Proof-of-Concept Study.

In the past, our research group was able to successfully remove circulating tumor cells with magnetic nanoparticles. While these cancer cells are typically present in low numbers, we hypothesized that magnetic nanoparticles, besides catching single cells, are also capable of eliminating a large number of tumor cells from the blood ex vivo. This approach was tested in a small pilot study in blood samples of patients suffering from chronic lymphocytic leukemia (CLL), a mature B-cell neoplasm. Cluster of differentiation (CD) 52 is a ubiquitously expressed surface antigen on mature lymphocytes. Alemtuzumab (MabCampath®) is a humanized, IgG1κ, monoclonal antibody directed against CD52, which was formerly clinically approved for treating chronic lymphocytic leukemia (CLL) and therefore regarded as an ideal candidate for further tests to develop new treatment options. Alemtuzumab was bound onto carbon-coated cobalt nanoparticles. The particles were added to blood samples of CLL patients and finally removed, ideally with bound B lymphocytes, using a magnetic column. Flow cytometry quantified lymphocyte counts before, after the first, and after the second flow across the column. A mixed effects analysis was performed to evaluate removal efficiency. p < 0.05 was defined as significant. In the first patient cohort (n = 10), using a fixed nanoparticle concentration, CD19-positive B lymphocytes were reduced by 38% and by 53% after the first and the second purification steps (p = 0.002 and p = 0.005), respectively. In a second patient cohort (n = 11), the nanoparticle concentration was increased, and CD19-positive B lymphocytes were reduced by 44% (p < 0.001) with no further removal after the second purification step. In patients with a high lymphocyte count (>20 G/L), an improved efficiency of approximately 20% was observed using higher nanoparticle concentrations. A 40 to 50% reduction of B lymphocyte count using alemtuzumab-coupled carbon-coated cobalt nanoparticles is feasible, also in patients with a high lymphocyte count. A second purification step did not further increase removal. This proof-of-concept study demonstrates that such particles allow for the targeted extraction of larger amounts of cellular blood components and might offer new treatment options in the far future.

Targeting the mevalonate or Wnt pathways to overcome CAR T-cell resistance in TP53-mutant AML cells.

TP53-mutant acute myeloid leukemia (AML) and myelodysplastic neoplasms (MDS) are characterized by chemotherapy resistance and represent an unmet clinical need. Chimeric antigen receptor (CAR) T-cells might be a promising therapeutic option for TP53-mutant AML/MDS. However, the impact of TP53 deficiency in AML cells on the efficacy of CAR T-cells is unknown. We here show that CAR T-cells engaging TP53-deficient leukemia cells exhibit a prolonged interaction time, upregulate exhaustion markers, and are inefficient to control AML cell outgrowth in vitro and in vivo compared to TP53 wild-type cells. Transcriptional profiling revealed that the mevalonate pathway is upregulated in TP53-deficient AML cells under CAR T-cell attack, while CAR T-cells engaging TP53-deficient AML cells downregulate the Wnt pathway. In vitro rational targeting of either of these pathways rescues AML cell sensitivity to CAR T-cell-mediated killing. We thus demonstrate that TP53 deficiency confers resistance to CAR T-cell therapy and identify the mevalonate pathway as a therapeutic vulnerability of TP53-deficient AML cells engaged by CAR T-cells, and the Wnt pathway as a promising CAR T-cell therapy-enhancing approach for TP53-deficient AML/MDS.