ANARCI on the platform
Number antibody sequences to canonical schemes and annotate CDRs, framework regions, and germline genes with ANARCI.
Before you can compare an antibody to another, humanize it, or point at a specific CDR loop, you need every residue to have a canonical number — position 27 in one antibody has to mean the same structural place as position 27 in the next. ANARCI assigns that numbering from sequence alone, in whichever standard scheme your workflow expects (IMGT, Kabat, Chothia, AHo, or Wolfguy), and in doing so carves the sequence into its CDR and framework regions and names the closest germline genes. It is the entry step for most of the antibody engineering arc.
Known accuracy issue
ANARCI can return CDR and framework region boundaries that don't match the requested numbering scheme — framework residues labelled as CDR residues — while the job still reports status SUCCESS. Verify CDR boundaries against an independent numbering tool before relying on them for humanization or paratope work.
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What ANARCI does
ANARCI (Antigen receptor Numbering And Receptor ClassIfication) takes one or more antibody variable-region sequences and assigns each residue a canonical position number. From that numbering it derives the CDR and framework boundaries and, when asked, aligns the sequence to germline V and J genes to name the closest match. The result is the coordinate system the rest of the antibody cluster reads: humanness scorers, developability profilers, and paratope predictors all reason in terms of numbered positions.
Citations
Dunbar J, Deane CM. ANARCI: antigen receptor numbering and receptor classification. Bioinformatics. 2016;32(2):298-300. doi: 10.1093/bioinformatics/btv552
When to reach for it
- Canonical numbering — you need residues numbered in IMGT, Kabat, Chothia, AHo, or Wolfguy so positions are comparable across antibodies.
- CDR identification — you want the six CDR loops and four framework regions carved out of a raw VH or VL sequence.
- Germline assignment — you want the closest germline V/J gene named for each chain.
Reach for IgBLAST instead when you specifically need V(D)J germline gene hits with alignment statistics and somatic-hypermutation counts. Reach for BioPhi or Humatch when the question is humanness rather than numbering. ANARCI chains forward into both biophi_humanize and antibody_developability.
How it fits the workflow
ANARCI is a numbering step, not a scoring step — its output is the substrate other tools consume. A common arc is anarci_number → biophi_humanize → antibody_developability: number the sequence, humanize it, then check that the humanized candidate is manufacturable. Because it accepts a therapeutic_name, you can also start from a known therapeutic and let the platform resolve the VH/VL from Thera-SAbDab before numbering.
How it runs
ANARCI runs as an asynchronous CPU job on Modal compute — you submit one or more sequences, the platform tracks the job and polls it, and a result card lands on the canvas when it completes, typically within two to three minutes.
Read next
ANARCI quickstart
Number an antibody sequence and read its CDRs in a few steps.
ANARCI inputs
Sequences, numbering schemes, and germline options.
ANARCI outputs
Numbered positions, CDR and framework regions, and germline genes.
Antibody engineering
How numbering, humanization, developability, and repertoire search fit together.
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Antibody engineering
Number, humanize, profile developability, and mine repertoires for therapeutic antibodies and AAV gene-therapy vectors on the platform.
ANARCI inputs and parameters
Submit up to 100 variable-region sequences and pick the scheme that sets CDR boundaries — imgt, chothia, kabat, aho or wolfguy — or name a known antibody.