A SEVERE ADVERSE DRUG REACTION (ADR) TO REGEN-COV (CASIRIVIMAB AND IMDEVIMAB)

INTRODUCTION: A promising means to limit the progression of the SARS-CoV-2 virus is the use of monoclonal antibodies (mAbs), which are able to recognize viral antigenic epitopes of the Spike protein. Despite their high degree of efficacy, mAbs are sometimes accompanied by adverse drug reactions (ADRs) and although rare, they do occur and their use should be carefully determined by risk benefit considerations. CASE DESCRIPTION: A 33-year-old female with a history of intermittent asthma presented with a 7-day history of fatigue, myalgia, postnasal drip, diffuse palpable lymphadenopathy, and severe headache. During the first five days of her illness, she had multiple negative COVID-19 PCR and antigen tests. PCR test became positive on day 6 and symptoms had begun slowly improving on day 8. Because of slow improvement of symptoms, she was given IV dose of REGEN-COV(600 mg casirivimab, 600 mg imdevimab). About 12 hours after infusion, symptoms of fatigue and myalgias increased dramatically. For the next 5 days she experienced severe, diffuse and profound muscle tenderness, arthralgias, and fatigue. Symptoms gradually dissipated two weeks after the start of the mAb treatment. DISCUSSION: The unusual worsening of symptoms after the start of the mAb raises the question of a severe infusion-related reaction to REGEN-COV consisting of severe worsening of symptoms, increased arthralgias and diffuse muscle tenderness. Although the cause of these drug-related adverse reactions is unclear, the delayed start of the mAb may have contributed. In general, mAbs are usually safe but individual risks need to be carefully weighed against their expected therapeutic benefit.