{
  "abstract": "We previously developed nanobodies acting as positive allosteric modulators (PAMs) of the calcium-sensing receptor (CaSR). Here, we sought to develop more potent CaSR modulators by creating bivalent nanobody constructs using 'tail-to-head' peptide-linker conjugation. The constructs were functionally characterized at CaSR in HEK293 cells in a Ca²⁺ mobilization assay. Homobivalent Nb4-Nb4 and Nb10-Nb10 constructs with linkers comprising 3, 5, 6 or 9 GGGG(S/T) repeats all displayed CaSR PAM potencies comparable with those exhibited by their monovalent counterparts. Likewise, five heterobivalent nanobodies combining Nb4, Nb10, Nb11, Nb36 or Nb37 through [GGGG(S/T)]₉ linkers exhibited PAM potencies similar to that of the monovalent version of the first (N-terminal) nanobody in the respective constructs. This prompted us to examine the functional properties of [GGGG(S/T)]₉-linked constructs combining Nb4 and the mGluR5-selective nanobody PAM Nb43mGlu5. Nb4-L9-Nb43mGlu5 displayed slightly increased CaSR PAM potency relative to Nb4, whereas Nb43mGlu5-L9-Nb4 exhibited ~40- and ~10-fold reduced potency compared with Nb4-L9-Nb43mGlu5 and Nb4, respectively. The findings indicate that 'tail-to-head' conjugation markedly reduces CaSR binding affinity of the second (C-terminal) nanobody and likely explains the lack of synergistic enhancement of PAM potency in the bivalent constructs. Thus, the suitability of tail-to-head linker conjugation of nanobodies is context dependent, governed by how the nanobody engages its target and by whether the linker perturbs these interactions.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark."
  ],
  "article_type": "research article",
  "arxiv": null,
  "author_total": 6,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Mahdis Nabipour",
      "orcid": "0009-0004-8776-6427"
    },
    {
      "affs": [
        0
      ],
      "name": "Charlotte Hagen Skadhauge"
    },
    {
      "affs": [
        0
      ],
      "name": "Line Juel Rasmussen"
    },
    {
      "affs": [
        0
      ],
      "name": "Hans Bräuner-Osborne",
      "orcid": "0000-0001-9495-7388"
    },
    {
      "affs": [
        0
      ],
      "name": "Jesper M Mathiesen"
    },
    {
      "affs": [
        0
      ],
      "name": "Anders A Jensen",
      "orcid": "0000-0002-7927-5052"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/2trqdxhjbzwd7.bib",
  "cited_by": 0,
  "doi": "10.1111/bcpt.70320",
  "fulltext_url": "https://europepmc.org/articles/PMC13716545",
  "id": "2trqdxhjbzwd7",
  "issns": [
    "1742-7835",
    "1742-7843"
  ],
  "landing_url": "https://europepmc.org/article/MED/42951375",
  "language": "eng",
  "licence": "CC-BY-NC-ND",
  "licence_label": "CC BY-NC-ND",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "heading",
      "Original Article"
    ],
    [
      "openalex",
      "2741|Monoclonal and Polyclonal Antibodies Research"
    ]
  ],
  "openalex": "W7224137435",
  "pdf_url": "https://europepmc.org/articles/PMC13716545?pdf=render",
  "pmcid": "PMC13716545",
  "pmid": "42951375",
  "published": "2026-10-28",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/2trqdxhjbzwd7.ris",
  "sources": [
    {
      "first_seen": "2026-10-31T00:20:32Z",
      "native_id": "MED:42951375",
      "source": "europepmc",
      "url": "https://europepmc.org/article/MED/42951375"
    },
    {
      "first_seen": "2026-11-01T12:23:49Z",
      "native_id": "PMC13716545",
      "source": "pmc",
      "url": "https://doi.org/10.1111/bcpt.70320"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "openalex:2741|Monoclonal and Polyclonal Antibodies Research",
      "subfield": "imaging"
    }
  ],
  "title": "Peptide-Linked Bivalent Nanobody Constructs as Positive Allosteric Modulators of the Calcium-Sensing Receptor.",
  "title_text": "Peptide-Linked Bivalent Nanobody Constructs as Positive Allosteric Modulators of the Calcium-Sensing Receptor.",
  "type": "peer-reviewed",
  "updated_at": "2026-11-02T12:21:02Z",
  "url": "https://research.draconitic.com/paper/2trqdxhjbzwd7",
  "venue": "Basic & clinical pharmacology & toxicology",
  "versions": []
}