Tocilizumab for coronavirus disease 2019 in pregnancy and lactation: a narrative review

BACKGROUND: Tocilizumab is a monoclonal antibody that interrupts interleukin-6 signalling, reducing downstream effects on inflammation and the innate immune response. It was shown to reduce mortality in patients with severe or critical coronavirus disease 2019 (COVID-19). Pregnant and breastfeeding people were largely excluded from clinical trials and hence, the extent to which results can be applied to these populations is not clear. OBJECTIVES: To synthesize published data on tocilizumab in pregnancy and lactation, highlight important knowledge gaps, and help inform clinical decision-making about tocilizumab's use in these populations with COVID-19. SOURCES: PubMed was searched for studies evaluating tocilizumab in pregnancy and lactation for COVID-19 and other indications. Literature on pharmacokinetics and reproductive/fetal safety of monoclonal antibodies in general was also sought. The US Food and Drug Administration and the European Medicines Agency guidance for the industry and regulatory approval documents were reviewed. CONTENT: Published data on tocilizumab in pregnancy include 610 cases (n = 20 with COVID-19) together with seven mother–infant breastfeeding pairs. Higher rates of spontaneous abortion and premature birth have been reported compared with the general population, but multiple confounding variables limit interpretation. There is little data on tocilizumab exposure in the second and third trimesters when transplacental transport is highest. The effects of tocilizumab on the developing immune system are unclear. Pregnant patients with COVID-19 who received tocilizumab were often critically ill and corticosteroid use was uncommon. Neonatal follow up was limited. Tocilizumab appears to be compatible with breastfeeding. IMPLICATIONS: Although the available data do not raise serious safety signals, they have significant limitations and are not sufficient to delineate the complete spectrum of potential adverse outcomes that may be associated with tocilizumab exposure during pregnancy and lactation. Diligent follow up and documentation of pregnancy outcomes will be important moving forward. A more effective regulatory framework to ensure equitable inclusion of pregnant people in research is clearly needed.