The rapid spread of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in an unprecedented public health crisis worldwide. Recent studies indicate that a hyperinflammatory syndrome induced by SARS-CoV-2 contributes to disease severity and mortality in COVID-19. In this Review, an overview of the pathophysiology underlying the hyperinflammatory syndrome in severe COVID-19 is provided. The current evidence suggests the hyperinflammatory syndrome results from a dysregulated host innate immune response. The gross and microscopic pathological findings as well as the alterations in the cytokine milieu, macrophages/monocytes, natural killer cells, T cells, and neutrophils in severe COVID-19 are summarized. Data also highlighted include the potential therapeutic approaches undergoing investigation to modulate the immune response and abrogate lung injury in severe COVID-19.

PURPOSE We report the long-term findings and final analysis of a pivotal multicenter trial of ibrutinib monotherapy in previously treated patients with Waldenström macroglobulinemia (WM). PATIENTS AND METHODS Sixty-three symptomatic patients with median prior therapies of two (range, one to nine therapies), of whom 40% were refractory to their previous therapy, received ibrutinib at 420 mg/d. Dose reduction was permitted for toxicity. RESULTS The median follow-up was 59 months, and overall and major response rates were 90.5% and 79.4%, respectively. At best response, median serum immunoglobulin M declined from 3,520 to 821 mg/dL, bone marrow disease involvement declined from 60% to 20%, and hemoglobin rose from 10.3 to 14.2 g/dL ( P < .001 for all comparisons). Responses were impacted by mutated (Mut) MYD88 and CXCR4 status. Patients with MYD88Mut, wild-type (WT) CXCR4 showed higher major (97.2% v 68.2%; P < .0001) and very good partial (47.2% v 9.1%; P < .01) response rates and a shorter time to major response (1.8 v 4.7 months; P = .02) versus patients with MYD88Mut CXCR4Mut. Conversely, four patients who had MYD88WT disease showed no major responses. The median 5-year progression-free survival (PFS) rate for all patients was not reached, and was 70% and 38% for those with MYD88Mut CXCR4WT and MYD88Mut CXCR4Mut WM, respectively ( P = .02). In patients with MYD88WT, the median PFS was 0.4 years ( P < .01 for three-way comparisons). The 5-year overall survival rate for all patients was 87%. Grade ≥ 3 adverse events in more than one patient at least possibly related included neutropenia (15.9%), thrombocytopenia (11.1%), and pneumonia (3.2%). Eight patients (12.7%) experienced atrial arrhythmia, and seven of the eight continued therapy with medical management. CONCLUSION Ibrutinib is highly active and produces long-term disease control in previously treated patients with WM. Treatment is tolerable. Response depth, time to major response, and PFS are impacted by MYD88 and CXCR4 mutation status.

Next-generation sequencing has revealed recurring somatic mutations in Waldenström macroglobulinemia (WM), including MYD88 (95%-97%), CXCR4 (30%-40%), ARID1A (17%), and CD79B (8%-15%). Deletions involving chromosome 6q are common in patients with mutated MYD88 and include genes that modulate NFKB, BCL2, Bruton tyrosine kinase (BTK), and apoptosis. Patients with wild-type MYD88 WM show an increased risk of transformation and death and exhibit many mutations found in diffuse large B-cell lymphoma. The discovery of MYD88 and CXCR4 mutations in WM has facilitated rational drug development, including the development of BTK and CXCR4 inhibitors. Responses to many agents commonly used to treat WM, including the BTK inhibitor ibrutinib, are affected by MYD88 and/or CXCR4 mutation status. The mutation status of both MYD88 and CXCR4 can be used for a precision-guided treatment approach to WM.

Purpose Ibrutinib is active in previously treated Waldenström macroglobulinemia (WM). MYD88 mutations ( MYD88) and CXCR4 mutations ( CXCR4) affect ibrutinib response. We report on a prospective study of ibrutinib monotherapy in symptomatic, untreated patients with WM, and the effect of CXCR4 status on outcome. Patients and Methods Symptomatic, treatment-naïve patients with WM were eligible. Ibrutinib (420 mg) was administered daily until progression or unacceptable toxicity. All tumors were genotyped for MYD88 and CXCR4. Results A total of 30 patients with WM received ibrutinib. All carried MYD88, and 14 (47%) carried a CXCR4. After ibrutinib treatment, median serum IgM levels declined from 4,370 to 1,513 mg/dL, bone marrow involvement declined from 65% to 20%, and hemoglobin level rose from 10.3 to 13.9 g/dL ( P < .001 for all comparisons). Overall (minor or more than minor) and major (partial or greater than partial) responses for all patients were 100% and 83%, respectively. Rates of major (94% v 71%) and very good partial (31 v 7%) responses were higher and time to major responses more rapid (1.8 v 7.3 months; P = 0.01) in patients with wild-type CXCR4 versus those with CXCR4, respectively. With a median follow-up of 14.6 months, disease in two patients (both with CXCR4) progressed. The 18-month, estimated progression-free survival is 92% (95% CI, 73% to 98%). All patients are alive. Grade 2/3 treatment-related toxicities in > 5% of patients included arthralgia (7%), bruising (7%), neutropenia (7%), upper respiratory tract infection (7%), urinary tract infection (7%), atrial fibrillation (10%), and hypertension (13%). There were no grade 4 or unexpected toxicities. Conclusion Ibrutinib is highly active, produces durable responses, and is safe as primary therapy in patients with symptomatic WM. CXCR4 status affects responses to ibrutinib.