“These effects suggest the potential for infection secondary to immune modulation. Although not common, first-dose infusion reaction occurred in a monkey (in 1 out of 52) and included moderate facial swelling.”
✓ VerifiedFDA pharmacology/toxicology review, p. 7Source ↗
Biodistribution & persistence
No unexpected tissue cross-reactivity; expected staining in brain white matter, cerebellum, cornea, spinal cord and peripheral nerve axons
“Expected specific cross-reactivity staining using biotinylated siltuximab was observed in human tissues from the brain white matter and cerebellum, squamous epithelium of the cornea, axons in the gray and white matter of the spinal cord, and axons of peripheral nerves.”
✓ VerifiedFDA pharmacology/toxicology review, p. 18Source ↗
Modality-specific risk
Infection risk from immune modulation (reduced immunoglobulin), including in infants exposed in utero
“Therefore, the infants born to a mother treated with siltuximab may be at increased risk of infections.”
✓ VerifiedFDA pharmacology/toxicology review, p. 18Source ↗
Anti-drug antibodies: animals
ADA in 1 monkey at 9.2 mg/kg in each 3-month study; exposure otherwise extensive in all other animals
“An anti-siltuximab antibody response was detected in one female at 9.2 mg/kg from the 3-month study with siltuximab, and in one male at 9.2 mg/kg from the 3-month combination study with siltuximab and IL-2. With the exception of these 2 animals, toxicokinetic (TK) analysis confirmed extensive systemic exposure in monkeys administered siltuximab”
0% (0/243) by EIA and 2% (4/189) by ECLIA; none neutralizing
“Following SYLVANT dosing, 0/243 (0%) patients tested positive for anti-siltuximab antibodies by EIA and 4/189 (2%) patients tested positive by ECLIA. Further immunogenicity analyses were conducted for all positive samples from the 4 patients with detectable anti-siltuximab antibodies. None of these patients had neutralizing antibodies.”
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