{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,10]],"date-time":"2026-10-10T14:05:20Z","timestamp":1791641120725,"version":"4.3.4"},"reference-count":49,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2024,3,14]],"date-time":"2024-03-14T00:00:00Z","timestamp":1710374400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft (DFG)","doi-asserted-by":"publisher","award":["410899006"],"award-info":[{"award-number":["410899006"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Martin-Luther-University Halle-Wittenberg","award":["410899006"],"award-info":[{"award-number":["410899006"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pharmaceutics"],"abstract":"<jats:p>Human carbonic anhydrase IX (hCA IX) is a zinc(II)-dependent metalloenzyme that plays a critical role in the conversion of carbon dioxide and water to protons and bicarbonate. It is a membrane-bound protein with an extracellular catalytic center that is predominantly overexpressed in solid hypoxic tumors. Sulfamates and sulfonamides, for example acetazolamide (AZA), have been used to inhibit hCA IX in order to improve the response to solid hypoxic tumors. In the present study, we propose a new drug targeting approach by attaching the natural cytotoxic substances betulin and betulinic acid (BA) via a linker to sulfonamides. The conjugate was designed with different spacer lengths to accumulate at the target site of hCA IX. Computational and cell biological studies suggest that the length of the linker may influence hCA IX inhibition. Cytotoxicity tests of the newly synthesized bifunctional conjugates 3, 5, and 9 show effective cytotoxicity in the range of 6.4 and 30.1 \u00b5M in 2D and 3D tumor models. The hCA IX inhibition constants of this conjugates, measured using an in vitro enzyme assay with p-nitrophenyl acetate, were determined in a low \u00b5M-range, and all compounds reveal a significant inhibition of hypoxia-induced CA activity in a cell-based assay using the Wilbur\u2013Anderson method. In addition, the cells respond with G1 increase and apoptosis induction. Overall, the dual strategy to produce cytotoxic tumor therapeutics that inhibit tumor-associated hCA IX was successfully implemented.<\/jats:p>","DOI":"10.3390\/pharmaceutics16030401","type":"journal-article","created":{"date-parts":[[2024,3,15]],"date-time":"2024-03-15T12:02:39Z","timestamp":1710504159000},"page":"401","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Combination of Betulinic Acid Fragments and Carbonic Anhydrase Inhibitors\u2014A New Drug Targeting Approach"],"prefix":"10.3390","volume":"16","author":[{"given":"Matthias","family":"Bache","sequence":"first","affiliation":[{"name":"Department of Radiotherapy, Martin-Luther-University Halle-Wittenberg, D-06120 Halle (Saale), Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6540-6357","authenticated-orcid":false,"given":"Niels V.","family":"Heise","sequence":"additional","affiliation":[{"name":"Institute of Chemistry, Martin-Luther-University Halle-Wittenberg, D-06120 Halle (Saale), Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andreas","family":"Thiel","sequence":"additional","affiliation":[{"name":"Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, D-06120 Halle (Saale), Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anne","family":"Funtan","sequence":"additional","affiliation":[{"name":"BioCenter, Martin-Luther-University Halle-Wittenberg, D-06120 Halle (Saale), Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1902-3280","authenticated-orcid":false,"given":"Franziska","family":"Seifert","sequence":"additional","affiliation":[{"name":"BioCenter, Martin-Luther-University Halle-Wittenberg, D-06120 Halle (Saale), Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marina","family":"Petrenko","sequence":"additional","affiliation":[{"name":"Department of Radiotherapy, Martin-Luther-University Halle-Wittenberg, D-06120 Halle (Saale), Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3214-8694","authenticated-orcid":false,"given":"Antje","family":"G\u00fcttler","sequence":"additional","affiliation":[{"name":"Department of Radiotherapy, Martin-Luther-University Halle-Wittenberg, D-06120 Halle (Saale), Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sarah","family":"Brandt","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine IV (Hematology\/Oncology), Martin-Luther-University Halle-Wittenberg, D-06120 Halle (Saale), Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4637-0157","authenticated-orcid":false,"given":"Thomas","family":"Mueller","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine IV (Hematology\/Oncology), Martin-Luther-University Halle-Wittenberg, D-06120 Halle (Saale), Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dirk","family":"Vordermark","sequence":"additional","affiliation":[{"name":"Department of Radiotherapy, Martin-Luther-University Halle-Wittenberg, D-06120 Halle (Saale), Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Iris","family":"Thondorf","sequence":"additional","affiliation":[{"name":"Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, D-06120 Halle (Saale), Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7911-290X","authenticated-orcid":false,"given":"Ren\u00e9","family":"Csuk","sequence":"additional","affiliation":[{"name":"Institute of Chemistry, Martin-Luther-University Halle-Wittenberg, D-06120 Halle (Saale), Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Reinhard","family":"Paschke","sequence":"additional","affiliation":[{"name":"BioCenter, Martin-Luther-University Halle-Wittenberg, D-06120 Halle (Saale), Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,3,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"408","DOI":"10.1038\/nchembio.2007.5","article-title":"The function of terpene natural products in the natural world","volume":"3","author":"Gershenzon","year":"2007","journal-title":"Nat. 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