Generation of anti-pHLA antibodies

Summary

Many cancer drivers are intracellular, beyond conventional antibodies, but HLA class I displays their fragments as peptide-HLA complexes. The challenge is discriminating a mutant pHLA from its wild-type form, often one amino acid apart, since any cross-reactive clone becomes on-target toxicity. FairJourney Bio used counter-selection across four naïve human libraries to recover 53 mutant-specific Fvs and a lead T-cell engager at 2.97 nM. 

Problem

A TCR-mimetic against a mutant oncoprotein must tell the mutant pHLA from its wild-type form, often differing by one residue. Any cross-reactive clone that slips through becomes on-target, off-tumour toxicity, so the therapeutic window is set at the discovery stage, not later. 

Approach

FairJourney Bio ran phage display against the mutant pHLA across four fully human naïve libraries (Fab and scFv, above 10^10 diversity). Each round applied rising counter-selection against wild-type and irrelevant pHLA, removing cross-reactive binders before positive selection, then triaged by ELISA and FACS. 

Outcome

All four libraries returned mutant-specific clones; the best reached 82% specificity, and 53 unique Fvs advanced. The lead Fv, reformatted as a CD3 T-cell engager, bound mutant pHLA at 2.97 nM and killed only mutant-bearing cells, leaving wild-type lines at baseline. 

Key Results