Dear Rituparna Sinha Roy,

Methods and general approach should be more less the same like in case "regular" biologics. High level plan you can find following documents below:

Guideline on Immunogenicity assessment of therapeutic proteins

https://www.ema.europa.eu/en/documents/scientific-guideline/guideline-immunogenicity-assessment-therapeutic-proteins-revision-1_en.pdf

Immunogenicity Testing of Therapeutic Protein Products — Developing and Validating Assays for Anti-Drug Antibody Detection

https://www.fda.gov/ucm/groups/fdagov-public/@fdagov-drugs-gen/documents/document/ucm629728.pdf

Article Compatibility of immunogenicity guidance by the EMA and the US FDA

I think its key documents, however regardless scope of that document remember that after lysis of peptides, internalization process generating some signaling sequences which interact with MHC. See example of tregitopes. So in case of unnatural amino-acids such short sequences could generate not predictable effects...

New tregitopes inducing adaptive regulatory T cells in mice.

http://www.jpp.krakow.pl/journal/archive/12_17/pdf/897_12_17_article.pdf

Best regards

Tomasz