{"entity":{"id":"mersana","kind":"company","name":"Mersana Therapeutics","aka":[],"tldr":"ADC platform company betting on B7-H4: emiltatug ledadotin (Emi-Le) has Breakthrough designation in adenoid cystic carcinoma and activity in TNBC after TOP1 ADCs.","summary":"Mersana Therapeutics, based in Cambridge, Massachusetts, and listed as MRSN, is an antibody-drug conjugate platform company betting on B7-H4, whose emiltatug ledadotin, or Emi-Le, holds Breakthrough designation in adenoid cystic carcinoma and shows activity in triple-negative breast cancer after topoisomerase 1 ADCs. Emi-Le, also XMT-1660, produced a 23 percent objective response rate in TNBC previously treated with topoisomerase 1 ADCs and confirmed responses in adenoid cystic carcinoma, earning Breakthrough designation in May 2026, and the company also pioneered STING-agonist ADCs such as XMT-2056. OnCo links it to TNBC, head and neck, ovarian and endometrial cancer, to ADC sequencing as a term, and to the bottleneck of acquired resistance. Whether a non-topoisomerase payload can rescue patients after TOP1 ADCs fail is the open question.","asOf":"2026-09-04","links":[{"label":"Breakthrough designation (OncLive)","url":"https://www.onclive.com/view/fda-grants-breakthrough-therapy-designation-to-emi-le-for-adenoid-cystic-carcinoma"}],"tags":[],"related":[],"cancers":["tnbc","head-and-neck","ovarian","endometrial"],"sections":["adcs"],"technologies":["adc","immune-stimulating-adc"],"targets":[],"drugs":["upifitamab-rilsodotin"],"companies":[],"institutions":[],"pathways":[],"terms":["adc-sequencing"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"hq":"Cambridge, MA","country":"US","companyType":"biotech","website":"https://www.mersana.com","ticker":"MRSN","investors":[],"funding":[]},"route":"/companies/mersana/","neighbours":{"cancer":[{"id":"endometrial","kind":"cancer","name":"Endometrial cancer","route":"/cancers/endometrial/"},{"id":"head-and-neck","kind":"cancer","name":"Head and neck squamous cell carcinoma","route":"/cancers/head-and-neck/"},{"id":"ovarian","kind":"cancer","name":"Ovarian cancer","route":"/cancers/ovarian/"},{"id":"tnbc","kind":"cancer","name":"Triple-negative breast cancer (TNBC)","route":"/cancers/tnbc/"}],"section":[{"id":"adcs","kind":"section","name":"Antibody-Drug Conjugates","route":"/fronts/adcs/"}],"technology":[{"id":"adc","kind":"technology","name":"Antibody-drug conjugate (ADC)","route":"/technologies/adc/"},{"id":"immune-stimulating-adc","kind":"technology","name":"Immune-stimulating antibody conjugate (ISAC)","route":"/technologies/immune-stimulating-adc/"}],"drug":[{"id":"upifitamab-rilsodotin","kind":"drug","name":"Upifitamab rilsodotin","route":"/drugs/upifitamab-rilsodotin/"}],"term":[{"id":"adc-sequencing","kind":"term","name":"ADC sequencing","route":"/terms/adc-sequencing/"}],"bottleneck":[{"id":"b-resistance","kind":"bottleneck","name":"Acquired resistance to every therapy","route":"/bottlenecks/b-resistance/"}],"company":[{"id":"bain-capital-life-sciences","kind":"company","name":"Bain Capital Life Sciences","route":"/companies/bain-capital-life-sciences/"}],"trial":[{"id":"nct03319628","kind":"trial","name":"First-in-Human Study of XMT-1536 in Cancers Likely to Express NaPi2b","route":"/trials/nct03319628/"}]}}