Adverse Drug Reaction Gender Differences in Patients Treated with REGEN-COV (Casirivimab/Imdevimab) for Treatment of COVID-19
Authors:   National Home Infusion Association, Haines Danell , Garst Ryan 
Published: February 2025

Introduction: The FDA provided an emergency use authorization for the monoclonal antibody (mAb) REGEN-COV, which is casirivimab and imdevimab, administered together either intravenously or subcutaneously for the treatment of SARS-COV-2. NHIF retrospectively collected and analyzed data from the REGEN-COV patient charts. Data analysis showed that home infused REGENCOV achieved comparable outcomes to other sites of care and provided improved access to treatment. For this study, NHIF conducted additional analysis of the REGENCOV data to include gender-related factors. This study answered the question, “Does a significant difference exist between men and women and the rate of adverse drug reactions (ADRs) from REGEN-COV?” If a significant difference does exist, what variables might have caused the difference between the genders, such as patient age, infusion time, vaccination status, and the number of days between the onset of COVID-19 symptoms and the first dose of REGEN-COV?

Methodology: Home infusion providers participated in this study from July 2021 through October 2021, collecting the following REGEN-COV data; patient age and gender, date symptoms started, date of infusion, infusion time, vaccination status, 7-day follow-up, and adverse events. Analysis was conducted to determine if a significant difference (p=.05) existed between the mean age of the genders, rate of ADRs and genders, infusion time and genders, infusion time and rate of ADRs, vaccination rate and genders, and the mean number of days between the onset of COVID-19 symptoms and the first dose of REGEN-COV and genders. Descriptive statistics were used to analyze demographic data. An ANOVA was conducted to determine if the mean ages of the men and women in the study were significantly different. This statistic was also used to determine if the mean time between the onset of COVID-19 symptoms and the first dose of REGEN-COV was significantly different between the genders. Fisher’s Exact Test was used to determine if a significant difference existed between gender and the occurrence of an ADR.

Results: There were 459 patient cases representing 5 home infusion providers. No significant difference (p=.615) was observed between the mean ages of the genders. Males had a significantly (p=.022) higher rate of reported ADRs when compared to females (6.94% versus 2.47%). This is contrary to previous gender and ADR studies which have shown that females have a higher rate of reported ADRs when various therapy types and illnesses are investigated. There was a significant difference (p=.009) in infusion times between the females and males. However, the infusion time that was predominantly for females, which was 20-minutes, was noted to have fewer overall ADRs. There was a significant difference (p=.001) between females and males in the number of days between the onset of COVID-19 symptoms and the first dose of REGEN-COV. Even so, there was no significant difference (p=.078) between the overall mean number of days between the onset of COVID-19 symptoms and the first dose when cross tabulated by ADRs.

Discussion: Due to the possible confounding variables that might have caused the differences in the rate of ADRs among the genders, such as the potential difference in health status and the low rate of ADRs in the patients, the investigators are hesitant to conclude that gender and the infusion rate caused the difference in the rate of ADRs. It is recommended that future mAb studies should match genders by health status and compare various infusion times with the rate of ADRs.

Conclusions: As noted in the literature, females typically have a higher rate of ADRs than males. This study showed the opposite. When the rate of ADRs was compared by infusion time, the 20-minute time had a 0.42% ADR rate, while the 30-minute time had a 10.95% rate. Even though males had a higher rate of ADRs compared to females, more than half of the males (56.91%) had an infusion rate of 20 minutes. Of the reported ADRs, all but 1 was classified as mild. As recommended in previous ADR research, investigation of gender differences needs to be a standard protocol for all studies.

Keywords: COVID, REGEN-COV, gender-differences, home infusion, infusion rate, ADR