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Mylotarg: which tox species, and why?

gemtuzumab ozogamicin · CD33
Species
Rat and cynomolgus monkey (neither pharmacologically relevant; no CD33 cross-reactivity)
“In view of the absence of cross-reactivity of gemtuzumab ozogamicin with CD33 from laboratory species, studies of kinetics in animals can only be of limited value, as there will be no binding, specific intracellular uptake, and metabolism of the conjugate that underlies its therapeutic action in humans.”
✓ VerifiedEMA assessment report, p. 51Source ↗
Why that species
No relevant species: antibody does not bind monkey CD33 or stain rat/monkey tissues; species used for off-target payload toxicity
“hP67.6 bound strongly to human CD33-transfected CHO cells but did not bind to the monkey CD33-transfected CHO cells (study 084032).”
✓ VerifiedEMA assessment report, p. 22Source ↗
Surrogate molecule
No surrogate; clinical ADC tested in non-binding rat and monkey (plus old vs new cell line bridging)
“Repeat-dose studies included six cycle intravenous toxicity studies in rats and monkeys and a six cycle comparative study in monkeys for the old and new antibody cell lines.”
✓ VerifiedFDA pharmacology/toxicology review, p. 7Source ↗

Same question, other ADCs

Adcetris

brentuximab vedotin · CD30
Rat and cynomolgus monkey (monkey the antigen-binding species)

Besponsa

inotuzumab ozogamicin · CD22
Rat and cynomolgus monkey (neither cross-reactive; target-independent toxicity only)

Datroway

datopotamab deruxtecan · Trop-2
Rat (non-binding) and cynomolgus monkey (relevant); DXd payload in rat and monkey

Decnupaz

pivekimab sunirine · CD123
Cynomolgus monkey (no CD123 cross-reactivity; off-target/payload toxicity) plus rat for FGN849 payload

Elahere

mirvetuximab soravtansine · FRα
Cynomolgus monkey (general tox); rabbit for ocular tox; DM4 payload in monkey and mouse

Emrelis

telisotuzumab vedotin · c-Met
Cynomolgus monkey (relevant); rat non-binding (exploratory, MMAE-related effects)

Enhertu

fam-trastuzumab deruxtecan · HER2
Cynomolgus monkey (relevant) plus rat (non-binding species)

Kadcyla

ado-trastuzumab emtansine · HER2
Rat and cynomolgus monkey (monkey pharmacologically relevant; long-term studies in monkey)

Padcev

enfortumab vedotin · Nectin-4
Rat and cynomolgus monkey

Polivy

polatuzumab vedotin · CD79b
Rat and cynomolgus monkey (monkey with clinical ADC plus monkey-CD79b surrogate ADC)

Tivdak

tisotumab vedotin · Tissue factor
Cynomolgus monkey only for ADC; rat and monkey for MMAE payload

Trodelvy

sacituzumab govitecan · Trop-2
Cynomolgus monkey only (mouse for target-independent toxicity only)

Zynlonta

loncastuximab tesirine · CD19
No pharmacologically relevant species; cynomolgus monkey (non-binding) for ADC; rat and dog for payload SG3199

Summary across all 14 ADCs →