Clinical Practice Guideline-Supported Administration of Monoclonal Antibody Therapy for High-Risk Patients with COVID-19: Experience of a Quaternary Care Centre.

Background: Immunocompromised patients remain at risk of progression to severe COVID-19 disease. Methods: We describe clinical COVID-19-related outcomes after administration of anti-SARS-CoV-2 monoclonal antibodies (mAb) following institutional clinical practice guidelines (CPGs) in 205 high-risk patients between November 2021 and April 2022 at a Canadian quaternary care centre. Results: Median patient age was 59 years; 102 (50%) were female. Eighty-two (40%) were transplant recipients, 47 (23%) patients had hematologic malignancies, 25 (12%) had solid organ malignancies, and 51 (25%) had another indication. Forty-eight (23%) had received fewer than two doses of anti-SARS-CoV-2 vaccines. The majority (80%) had mild disease at presentation with 14% moderate and 6% severe. Median time from symptom onset to mAb administration was 3 days (IQR 2.0-5.5 days). Of those who received mAb as outpatients, 90 (93%) had favourable clinical outcomes (no COVID-19-related hospitalizations or death within 3 months). Of those who received mAb as inpatients, 93 (86%) had favourable outcomes (discharged without COVID-19-related re-admission or death), 4% were re-admitted, and 10% died. In logistic regression analysis, only disease severity at time of mAb administration was associated with unfavourable outcomes. Fewer than two vaccine doses was not associated with unfavourable outcomes, suggesting potential benefit among the under-vaccinated. There was a significant difference in adherence to CPGs between administration of mAb in outpatients versus inpatients (adherent for 85% versus 58%, Conclusion: CPG-supported mAb administration for management of COVID-19 in high-risk patients was associated with favourable clinical outcomes and may be a useful model to guide future therapies.