The 5T4 oncofetal
antigen (trophoblast
glycoprotein) is expressed in a wide range of malignant
tumors but shows very limited expression in normal adult tissues. ASN004 is a 5T4-targeted
antibody-drug conjugate (ADC) that incorporates a novel
single-chain Fv-Fc antibody and
Dolaflexin drug-linker technology, with an
Auristatin F hydroxypropylamide payload
drug-to-antibody ratio of approximately 10-12. The pharmacology, toxicology, and pharmacokinetic properties of ASN004 and its components were investigated in vitro and in vivo ASN004 showed high affinity for the 5T4
antigen and was selectively bound to and internalized into 5T4-expressing
tumor cells, and potent cytotoxicity was demonstrated for a diverse panel of solid tumor cell lines. ASN004 induced complete and durable
tumor regression in multiple
tumor xenograft models, derived from human lung, breast, cervical, and gastric tumor cell lines having a wide range of 5T4 expression levels. A single dose of ASN004, as low as 1 mg/kg i.v., achieved complete
tumor regression leading to
tumor-free survivors in the A431
cervical cancer model. In head-to-head studies, superior activity of ASN004 was demonstrated against
trastuzumab-DM1, in a low-5T4/high-HER2 expressing gastric
tumor model, and 10-fold greater potency was found for ASN004 against the 5T4-targeted ADC
PF-06263507 in a lung
tumor model. In marmoset monkeys, ASN004 was well tolerated at doses up to 1.5 mg/kg Q3W i.v., and showed dose-dependent exposure, linear pharmacokinetics, and markedly low exposure of free payload
drug. Taken together, these findings identify ASN004 as a promising new ADC therapeutic for clinical evaluation in a broad range of solid
tumor types.