ADC Conjugate Ratio to Therapeutic Efficacy in zebrafish

Antibody therapies need evaluation of safety efficacy in physiological models to gain maximum translation benefit. Towards such, ADCs targeting Folate receptor alpha, TROP2, and HER2 antigens were studied. The objective was to identify amount of distribution vs amount of release at target sites using PK. Outcomes were to identify ADC-Conjugate ratio with maximal efficacy at tumour site with sublethal toxicity at rest of the body.

A capillary needle attached to a pico pump system to deliver nanolitre volume of ADCs to zebrafish's circulatory system. Notice the carrier coloured with phenol red to mark larvae that received the dose.

Zebrafish larvae injected with varying concentrations of ADC payload and efficacy screening was performed at various dose ratio concentrations. A corelation of target efficiency vs therapeutic efficacy was observed for three different antigens.

Type of Tumor Graft	Antigen	Conjugate	Loading Volume per gram larvae weight	PK at Tumor site vs rest of the body	Efficacy % (Pathological Complete response + Progress free survival)
CAOV-4	Folate receptor alpha	Mirvetuximab soravtansine	313pg	1.437	73
NSCLC	TROP2	Sacituzumab govitecan	400pg	1.645	64
MDA-MB-453	HER2	Trastuzumab emtansine	130pg	0.864	52

Larvae post ADC injection showing distribution of phenol red.

Pathological complete response that measured tumor volume and PCR assessments were quantified to arrive at efficacy percentage. PK of drugs in larvae were initially standardized for linearity in larvae protein matrix and were loaded directly into HPLC with limited steps to obtain the most accurate tissue distribution