BACKGROUND Patients with underlying medical conditions are at increased risk for severe coronavirus disease 2019 (Covid-19). Whereas vaccine-derived immunity develops over time, neutralizing monoclonal-antibody treatment provides immediate, passive immunity and may limit disease progression and complications. METHODS In this phase 3 trial, we randomly assigned, in a 1:1 ratio, a cohort of ambulatory patients with mild or moderate Covid-19 who were at high risk for progression to severe disease to receive a single intravenous infusion of either a neutralizing monoclonal-antibody combination agent (2800 mg of bamlanivimab and 2800 mg of etesevimab, administered together) or placebo within 3 days after a laboratory diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The primary outcome was the overall clinical status of the patients, defined as Covid-19-related hospitalization or death from any cause by day 29. RESULTS A total of 1035 patients underwent randomization and received an infusion of bamlanivimab-etesevimab or placebo. The mean (+/- SD) age of the patients was 53.8 +/- 16.8 years, and 52.0% were adolescent girls or women. By day 29, a total of 11 of 518 patients (2.1%) in the bamlanivimab-etesevimab group had a Covid-19-related hospitalization or death from any cause, as compared with 36 of 517 patients (7.0%) in the placebo group (absolute risk difference, -4.8 percentage points; 95% confidence interval [CI], -7.4 to -2.3; relative risk difference, 70%; P<0.001). No deaths occurred in the bamlanivimab-etesevimab group; in the placebo group, 10 deaths occurred, 9 of which were designated by the trial investigators as Covid-19-related. At day 7, a greater reduction from baseline in the log viral load was observed among patients who received bamlanivimab plus etesevimab than among those who received placebo (difference from placebo in the change from baseline, -1.20; 95% CI, -1.46 to -0.94; P<0.001). CONCLUSIONS Among high-risk ambulatory patients, bamlanivimab plus etesevimab led to a lower incidence of Covid-19-related hospitalization and death than did placebo and accelerated the decline in the SARS-CoV-2 viral load.

Distinction between lymphocyte-rich thymoma and T-lymphoblastic lymphoma/leukemia (T-LBL) can be problematic because of a predominance of precursor T cells in both, particularly if the epithelial component in a thymoma is undersampled. Because of very different clinical implications, accurate diagnosis is critical. The NOTCH1 signaling pathway is frequently activated in T-LBL and plays a central role in the pathogenesis of this disease. Antibodies to NOTCH1 intracellular domain (N1ICD), recognizing the active form of NOTCH1, have been developed. We hypothesized that detection of N1ICD would be useful in distinguishing T-LBL from thymoma and investigated a series of formalin-fixed, paraffin-embedded tissues for immunoreactivity with an N1ICD antibody using automated immunohistochemistry. Slides were scored using a 25% nuclear reactivity threshold for positivity. Hyperplastic tonsil showed positivity in few scattered interfollicular lymphoid cells, suprabasilar epithelial cells, and endothelial cells. Thymocytes from non-neoplastic thymus were largely negative for N1ICD. All thymomas tested (n=23) were negative for N1ICD, although epithelial cells and a small minority of thymocytes may be positive, requiring careful interpretation. All T-LBL cases (n=16) were scored positive for N1ICD: 8 (50%) of these showed diffuse and mostly strong immunoreactivity, whereas the remaining 8 (50%) had less extensive positivity, but with consistently >25% nuclear staining. In conclusion, normal thymocytes do not express significant levels of N1ICD. In keeping with this pattern, thymomas are negative for N1ICD, whereas a high percentage of T-LBL expresses N1ICD. Thus, N1ICD immunohistochemistry appears to be a useful method in distinguishing T-LBL from thymoma.

Purpose: Despite advances in immunosuppressive therapy, T cell mediated rejection continues to be a significant source of morbidity and mortality in heart transplant patients past the first year. T cell antigen receptor (TCR) signaling is the essential element in these alloresponses against donor MHC and non-MHC antigens. Yet there is no therapy to specifically target this process. Dasatinib, an oral kinase inhibitor used for chronic myeloid leukemia, is exquisitely specific for Abl and Src family kinases (SFK), which are critical for the first step of T cell activation. The immunosuppressive effects of Dasatinib have not yet been examined, thus we conducted the following studies to determine the effects of this drug on in vitro T cell responses.

Cytokine receptors preferentially associate with particular JAK-STAT combinations to transduce specific signals. For example, erythropoietin receptor (Epo-R) preferentially interacts with JAK2 to initiate signaling pathways via STAT5. The JAK2 V617F mutation (mJAK2) found in some myeloproliferative disorders (MPD) still requires binding to type I cytokine receptors to initiate signaling. Consequently, aberrant JAK-STAT signaling in MPD may require physiologic interactions with other pathways. Src family kinases (SFK) interact with various cytokine receptors resulting in close association between SFK and JAK-STAT pathways. We hypothesized that SFK activity plays a role in the activation of STAT5 and, given the importance of STAT5 in the pathogenesis of MPD, targeted inhibition of SFK could provide a novel therapeutic approach. First, we examined the effect the SFK inhibitors PP2 and SU6656 on the proliferation of the HEL cell line harboring mJAK2 and the Epo-dependent AML line UT7/Epo; SFK inhibition significantly diminished proliferation in both cell lines. These results imply that despite of the constitutive activity of mJAK2 or in the presence of Epo stimulated JAK2-STAT5 induction, SFK activation is required for proliferation. Since mJAK2 requires a functionally intact type I cytokine receptor, we examined Epo-R signaling in greater detail via phospho-specific immunoblotting. SFK inhibition resulted in diminished levels of phospho-SFK, coinciding with a similar degree of diminished phospho-STAT5. Simultaneously decreased induction of AKT and ERK pathways after SFK inhibition suggested SFK activity is also regulating a more global signaling network through the Epo-R. Inhibition of JAK2 activity potently suppressed phospho-STAT5, as well as ERK and AKT, without affecting SFK phosphorylation. Thus, SFK lies upstream of JAK2, or SFK and JAK2 may be regulating the second messenger pathways in parallel. In electrophoretic mobility shift assays to examine the effect of SFK inhibition on STAT5 DNA binding, SFK inhibition resulted in decreased STAT5 DNA binding despite constitutive activity of mJAK2. Analogous results were obtained after Epo stimulation in UT7/Epo cells. As expected, inhibition of JAK2 resulted in almost complete loss of STAT5 DNA binding. To confirm these results in primary cells, we examined the effects of SFK inhibition on primary monocytes from a patient with mJAK2. Stimulation with GM-CSF resulted in increased STAT5A DNA binding, but not STAT5B. In the presence of the SFK inhibitor PP2, GM-CSF induction of STAT5A DNA binding activity was completely inhibited. It is interesting to note that a key difference between STAT5A and STAT5B is the potential for ERK regulation of STAT5A DNA binding activity. Thus, showing here that SFK regulates ERK activity, and knowing that ERK activity can positively regulate STAT5A DNA binding, we propose a model in which SFK activity may modulate the JAK2-STAT5 signaling axis via the ERK pathway. In summary, our results demonstrate that while JAK2 is essential for this process, SFK activity appears to be necessary for full activation by positively modulating the JAK2-STAT5 axis. SFK inhibitors recently approved and in clinical trials may demonstrate efficacy in hematologic diseases characterized by aberrant JAK-STAT signaling, such as MPD.

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by somatic mutation of the PIGA gene, resulting in a clonal disorder of hematopoietic stem cells (HSC) that lack glycosylphosphatidyl inositol-anchored proteins (GPI-AP) on the cell surface. According to the extrinsic theory, PNH stem cells enjoy a selective growth advantage in the context of a cellular immune attack eliciting proinflammatory cytokines, such as seen during the course of aplastic anemia (AA). Since GPI-AP associate with lipid rafts in the plasma membrane and we have previously shown that lipid rafts exist as heterogeneous microdomains on the cell surface, we proposed that GPI-AP deficiency in PNH cells may result in altered raft-dependent signaling pathways to confer a potential growth advantage on PNH cells.