In vitro interleukin release by human white blood cells prompted a clinical hold for potential cytokine release syndrome
“The Agency placed the application on full clinical hold on January 6, 2017, due to the potential risk of cytokine release syndrome (based on demonstration of release of interleukins induced in human white blood cells in an in vitro cytokine release assay).”
Possible FcRn competition with maternal IgG from YTE modification, potentially reducing passive immunity in infants
“It is unknown if competition could exist between maternal antibodies and clesrovimab for FcRn binding sites/IgG-recycling and if clesrovimab is preferentially recycled over endogenous maternal IgG due to the increased affinity for FcRn through the YTE modification”
ADA in 1 female rat (30 mg/kg) from day 28 with markedly reduced individual exposure; no impact on group toxicokinetics
“Anti-drug antibodies (ADA) were detected in one female animal in the 30 mg/kg dose group from day 28 post the first dosing. Even though the individual exposure of the animal was highly diminished, suggesting strong neutralising ADA potential, no substantial impact on overall group mean concentration and toxicokinetic values were noted.”
Day 150: 6% (Trial 004) and 5% (Trial 007); through Day 240: 12% and 13%
“In Trial 004 and Trial 007, after receiving the approved recommended dose in RSV season 1, 6% (120/2112) and 5% (13/291) of participants were ADA-positive on Day 150, respectively; and 12% (124/1033) and 13% (34/261) of participants were ADA-positive through Day 240, respectively.”
In vitro whole-blood cytokine release far below alemtuzumab/TGN1412 controls; no effects on monkey TDAR, lymphocyte subsets or serum cytokines; ADA in some monkeys