Development of an Oncology VHH-ADC Candidate via Site-Specific Non-Canonical Amino Acid Conjugation

by | Aug 24, 2026 | Case Studies

Development of an Oncology VHH-ADC Candidate

via Site-Specific Non-Canonical Amino Acid Conjugation

Pfenex Expression Technology® | Primrose Bio

Challenge

  • Incorporate a non-canonical amino acid (ncAA) pAzF, into a VHH antibody for ADC enhancement, PET771
  • Scale to 2L to ensure efficient ncAA incorporation
  • Confirm binding of new VHH-ADC to target GPCR

Strategy

  • Evaluate three suitable incorporation sites
  • Screen at 96-deep well scale
  • Confirm titer and pAzF incorporation by LC/MS
  • Assess feed strategies at 2L
  • Determine target binding and conjugation efficiency

Results

  • 96-deep well scale screening confirms titers above 1mg/mL.
  • Intact-MS confirms 100% incorporation of pAzF at the expected position with no incorporation of native Tyr or Thr observed
  • Continuous feed of pAzF with media achieves titers of 15g/L with 100% pAzF incorporation
  • VHH-ADC binding confirmed to target GPCR by flow cytometry (data not shown)

PET771 Next Steps

  • Developing chemical conjugation of PET771 to DBCO-activated antineoplastic agent
  • In vitro cytotoxicity assays and in vivo efficacy studies to be performed
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