Monoclonal antibody treatment for COVID-19 was safe to use in pregnancy, but wasn’t all that effective, according to a single-center study.

Among pregnant patients with mild-to-moderate COVID-19 who received monoclonal antibody treatment, infusion reactions were rare, with 1.4% of patients experiencing mild, drug-related adverse events (AEs), reported Erin McCreary, PharmD, of University of Pittsburgh Medical Center, and colleagues.

Patients treated with monoclonal antibodies did not experience differences in obstetric outcomes at delivery — including gestational age at birth, birthweight, stillbirths, maternal morbidity, and others — compared to non-treated patients, they stated in the Annals of Internal Medicine.

However, in efficacy analyses, there were no statistically significant differences in the composite outcome of COVID-related hospitalizations, emergency department visits, or mortality at 28 days between pregnant patients who did and did not receive treatment:

• Overall population: risk ratio [RR] 0.71 (95% CI 0.37-1.40)
• Propensity score-matched analysis: RR 0.61 (95% CI 0.34-1.10)

McCreary told MedPage Today that this is one of the largest datasets describing safety and efficacy of monoclonal antibodies for COVID-19 treatment in pregnancy. She stressed that monoclonal antibody treatment may still be the right choice based on a patient’s individual risk profile for severe illness, efficacy results aside.

“We still offer monoclonal antibodies to pregnant persons,” McCreary said, and encouraged a case-by-case discussion between patients and providers about the patient’s medical history or underlying risk of hospitalization. “Most importantly, we know that these monoclonal antibody therapies are safe,” she said.

Kjersti Aagaard, MD, PhD, of Baylor College of Medicine in Houston, told MedPage Today that the study showed “no harm, but no real benefit” to monoclonal antibody therapy for COVID-19 in pregnancy. Aagaard, who was not involved in the study, added that the findings will help inform decision-making for medical society guidelines “to avoid use of expensive therapies that do not offer evident benefit.”

In May 2021, emergency use authorizations for monoclonal antibodies were updated to include pregnancy as a risk factor for severe COVID-19. However, limited studies have investigated the safety and efficacy of these therapies among pregnant patients, McCreary’s group stated.

They conducted the restrospective cohort study to evaluate monoclonal antibody treatment among pregnant patients who tested positive for SARS-CoV-2. All study participants received treatment at University of Pittsburgh Medical Center between April 2021 and January 2022.

Before mid-December 2021, all patients treated with monoclonal antibodies received a product such as bamlanivimab-etesevimab, casirivimab-imdevimab, or sotrovimab. Post-Omicron variant, all treated patients received IV sotrovimab (mid-December 2021 to January 2022). Patients were treated in any outpatient infusion center, urgent care facility, or obstetric triage area, with both the treated and non-treated cohorts undergoing a 28-day follow-up period, according to the authors.

McCreary’s group evaluated the safety of monoclonal antibodies via drug-related AEs reported by providers or patients at each treatment site, along with obstetric outcomes.

Propensity scores were generated using multivariate logistic regression that modeled the likelihood of receiving treatment, including variables such as age, race, vaccination status, gestational age, insurance type, medical comorbidities, and others.

Of 944 pregnant patients (median age 30, majority white), 58% received monoclonal antibody treatment. Mean gestational age at COVID-19 diagnosis was 179 days, or more than 25 weeks of pregnancy. Of all patients with known vaccine status, 62% were fully vaccinated.

In total, 60% of patients were treated within 4 days of symptom onset, and most patients were treated with sotrovimab. Patients treated with monoclonal antibodies were more likely to be older, have commercial insurance, and have a history of infertility, the researchers noted. Additionally, treated patients were more likely to be vaccinated.

Overall, infusion reactions were rare, and there were no severe drug-related AEs. There were no deaths in the cohort of patients treated with monoclonal antibodies and one death in the non-treated group.

In the unmatched cohort, patients treated with monoclonal antibodies had more non-COVID-related hospitalizations than patients who were not treated (2% vs 0.5%, respectively), the researchers found. However, there were no differences in the propensity score-matched rates (2.5% vs 2%, respectively), suggesting that “unmeasured differences may be present between groups unrelated to monoclonal antibody treatment,” according to the researchers.

Study limitations included the reporting of drug-related AEs by patients and providers, so underreporting may have been an issue. Additionally, data on symptom severity at the time of testing and treatment for non-treated patients were not available.

McCreary said that if emerging variants continue to prove resistant to monoclonal antibody therapies, their future use in pregnant patients is uncertain. However, if antibodies that neutralize existing variants are still available, these therapies are a viable option for pregnant patients, she said.

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