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Chimeric antigen receptor (CAR-) T cell therapy causes serious side effects including cytokine release syndrome (CRS). CRS-related coagulopathy is associated with hypofibrinogenemia that is thus far considered the result of disseminated intravascular coagulation (DIC) and liver dysfunction. We investigated incidence and risk factors for hypofibrinogenemia in 41 consecutive adult patients with hematologic malignancies (median age 69 years, range 38-83 years) receiving CAR-T cell therapy between 01/2020 and 05/2023 at the University Medical Center Regensburg. CRS occurred in 93% of patients and was accompanied by hypofibrinogenemia already from CRS grade 1. Yet, DIC and liver dysfunction mainly occurred in severe CRS (≥ grade 3). After an initial increase during CRS, fibrinogen levels dropped after administration of tocilizumab in a dose dependent manner (r = -0.44, p = 0.004). In contrast, patients who did not receive tocilizumab had increased fibrinogen levels. Logistic regression analysis identified tocilizumab as an independent risk factor for hypofibrinogenemia (odds ratio = 486, p < 0.001). We thus hypothesize that fibrinogen synthesis in CRS is upregulated in an interleukin-6-dependent acute phase reaction compensating for CRS-induced consumption of coagulation factors. Tocilizumab inhibits fibrinogen upregulation resulting in prolonged hypofibrinogenemia. These observations provide novel insights into the pathophysiology of hypofibrinogenemia following CAR-T cell therapy and emphasize the need for close fibrinogen monitoring after tocilizumab treatment of CRS.

Abstract Objective To evaluate the influence of mechanical stress on the development of immediate enthesitis. Methods The BEAT study is an interventional study that assessed entheses in competitive badminton players before and immediately after a 60-min intensive training session. Power Doppler (PD) signal and Gray scale (GS) changes were assessed in the insertion sites of both Achilles tendon, patellar tendons, and lateral humeral epicondyles and quantified using a validated scoring system. Results Thirty-two badminton players were included. One hundred ninety-two entheseal sites were examined twice. The respective empirical total scores for PD examination were 0.1 (0.3) before and 0.5 (0.9) after training. Mean total GS scores were 2.9 (2.5) and 3.1 (2.5) before and after training, respectively. The mean total PD score difference of 0.4 between pre- and post-training was significant (p = 0.0014), whereas no significant difference for the mean total GS score was observed. Overall, seven participants (22%) showed an increased empirical total PD score. A mixed effects model showed a significant increase of PD scores after training, with a mean increase per site of 0.06 (95% CI 0.01 to 0.12, p = 0.017). Conclusions Mechanical stress leads to rapid inflammatory responses in the entheseal structures of humans. These data support the concept of mechanoinflammation in diseases associated with enthesitis.