Safety marginAcceptedBeyond the letter
Monkey NOAELs at 0.3-0.9x human AUC; no exposure margin at the NOAEL
Why: Normal animals more sensitive to mineralization than XLH patients; effects linked to serum phosphate, monitorable in the clinic · Pharmacology or kinetics · Human data
“The animal NOAELs were low (0.3Ͳ0.9x human AUC exposure) due to the sensitivity of normal animals to mineralization. However, this has limited significance, since, like Hyp mice, XLH patients are expected to be at a reduced risk of ectopic mineralization compared to normal animals or humans.”
✓ VerifiedFDA multi-discipline review, p. 45Source ↗ “Since the adverse effects are linked to serum phosphate levels and thus can be monitorable in the clinic, the lack of margins is not considered to be a crucial issue.”
✓ VerifiedEMA assessment report, p. 29Source ↗ CarcinogenicityAcceptedBeyond the letter
No carcinogenicity studies for chronic therapy; weight-of-evidence assessment instead of two-year rodent studies
Why: Burosumab does not bind rodent FGF23; weight-of-evidence assessment; Executive Carcinogenicity Assessment Committee concurred · No relevant species · Weight of evidence
“Standard 2Ͳyear rodent carcinogenicity studies with burosumab are not feasible since burosumab does not bind rodent FGF23.”
✓ VerifiedFDA multi-discipline review, p. 70Source ↗ “The Executive Carcinogenicity Assessment Committee was consulted by the Division regarding the Sponsor’s carcinogenicity risk assessment on April 28, 2017, and concurred that carcinogenicity studies with burosumab are not needed.”
✓ VerifiedFDA multi-discipline review, p. 71Source ↗ DARTVerdict not stated
No dedicated fertility or separate embryo-fetal studies; single monkey ePPND study
“EmbryoǦFetal Development Separate EFD studies were not performed. However, an ePPND study was conducted in cynomolgus monkeys.”
✓ VerifiedFDA multi-discipline review, p. 71Source ↗ OtherQuestioned
Hyp versus wild-type mouse mineralization study lacked toxicokinetic data
“However, a deficiency of this study is the lack of toxicokinetic data.”
✓ VerifiedEMA assessment report, p. 31Source ↗