{"entity":{"id":"pt-1","kind":"trial","name":"PT-1 (Primary Thrombocythaemia 1)","aka":[],"tldr":"PT-1 is the trial that made hydroxyurea the first-line drug in high-risk ET: anagrelide gave more arterial clots, more serious bleeding and more progression to myelofibrosis.","summary":"PT-1 randomised 809 patients with high-risk essential thrombocythaemia to hydroxyurea or anagrelide, both with low-dose aspirin. After a median of 39 months the composite primary endpoint of arterial or venous thrombosis, serious haemorrhage or death from a thrombotic or haemorrhagic cause was more frequent on anagrelide (odds ratio 1.57); anagrelide gave more arterial clots, serious bleeding and transformation to myelofibrosis, and fewer venous clots (Harrison and colleagues, New England Journal of Medicine 2005). Registered as ISRCTN72251782.","status":"positive","asOf":"2026-09-16","links":[{"label":"ISRCTN72251782","url":"https://www.isrctn.com/ISRCTN72251782"},{"label":"NEJM 2005","url":"https://www.nejm.org/doi/full/10.1056/NEJMoa043800"}],"tags":["essential-thrombocythaemia","mpn"],"related":[],"cancers":["essential-thrombocythaemia","myeloproliferative-neoplasms"],"sections":[],"technologies":["cytotoxic-chemotherapy"],"targets":[],"drugs":["hydroxyurea","anagrelide","inca033989","aspirin"],"companies":["mrc-ctu"],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"phase":"3","setting":"High-risk essential thrombocythaemia: hydroxyurea plus aspirin versus anagrelide plus aspirin","sponsor":"Medical Research Council (UK)","participation":[{"nct":"NCT00175838","source":"https://clinicaltrials.gov/study/NCT00175838","fetchedAt":"2026-10-07T17:02:50.866Z","studySha256":"83418f6b316aacce61d74d6172eec99e78be5b2d19d6a42baa9ff93dedc02f54","overallStatus":"COMPLETED","lastUpdatePosted":"2017-01-18","leadSponsor":"University of Cambridge","collaboratorCount":2,"minimumAge":"40 Years","maximumAge":"59 Years","sex":"ALL","healthyVolunteers":false,"hasEligibility":true,"enrolment":1398,"enrolmentType":"ACTUAL","siteCount":1,"recruitingSiteCount":0,"countries":["United Kingdom"]}],"alternateParticipation":[{"registry":"ISRCTN","registryId":"ISRCTN72251782","snapshot":"/trial-participation/other/ISRCTN72251782.json","source":"https://www.isrctn.com/ISRCTN72251782","fetchedAt":"2026-10-07T17:01:26.909557Z","lastUpdated":"2012-08-28T00:00:00.000Z","hasEligibility":true,"siteCount":1,"sponsors":["Medical Research Council (MRC) (UK)"]}],"result":"Composite of thrombosis, serious haemorrhage or vascular death more frequent with anagrelide (odds ratio 1.57); more arterial clots, bleeding and myelofibrosis on anagrelide.","yearReported":2005,"enrolled":809,"enrolledBasis":"registry","outcomes":[{"endpoint":"Arterial or venous thrombosis, serious haemorrhage, or death from thrombotic or haemorrhagic causes","primary":true,"arms":[{"name":"Anagrelide + low-dose aspirin","note":"Odds ratio 1.57 (95% CI 1.04-2.37) versus hydroxyurea; 809 patients, median follow-up 39 months"},{"name":"Hydroxyurea + low-dose aspirin"}],"p":"0.03","source":"https://www.nejm.org/doi/full/10.1056/NEJMoa043800"}]},"route":"/trials/pt-1/","neighbours":{"cancer":[{"id":"essential-thrombocythaemia","kind":"cancer","name":"Essential thrombocythaemia (ET)","route":"/cancers/essential-thrombocythaemia/"},{"id":"myeloproliferative-neoplasms","kind":"cancer","name":"Myeloproliferative neoplasms (PV, ET, myelofibrosis)","route":"/cancers/myeloproliferative-neoplasms/"}],"technology":[{"id":"cytotoxic-chemotherapy","kind":"technology","name":"Cytotoxic chemotherapy","route":"/technologies/cytotoxic-chemotherapy/"}],"drug":[{"id":"anagrelide","kind":"drug","name":"Anagrelide","route":"/drugs/anagrelide/"},{"id":"aspirin","kind":"drug","name":"Aspirin","route":"/drugs/aspirin/"},{"id":"hydroxyurea","kind":"drug","name":"Hydroxyurea (hydroxycarbamide)","route":"/drugs/hydroxyurea/"},{"id":"inca033989","kind":"drug","name":"INCA033989","route":"/drugs/inca033989/"}],"company":[{"id":"mrc-ctu","kind":"company","name":"MRC Clinical Trials Unit at UCL","route":"/companies/mrc-ctu/"}]}}