Background: No standard treatment exists for refractory or relapsed advanced thymic epithelial tumours. We investigated the efficacy of cixutumumab, a fully human IgG1 monoclonal antibody targeting the insulin-like growth factor 1 receptor in thymic epithelial tumours after failure of previous chemotherapy. Methods: Between Aug 25, 2009, and March 27, 2012, we did a multicentre, open-label, phase 2 trial in patients aged 18 years or older with histologically confirmed recurrent or refractory thymic epithelial tumours. We enrolled individuals who had progressed after at least one previous regimen of platinum-containing chemotherapy, had an Eastern Cooperative Oncology Group performance status of 0 or 1, and had measurable disease and adequate organ function. Eligible patients received intravenous cixutumumab (20 mg/kg) every 3 weeks until disease progression or development of intolerable toxic effects. The primary endpoint was the frequency of response, analysed on an intention-to-treat basis. We also did pharmacodynamic studies. This trial is registered with ClinicalTrials.gov, number NCT00965250. Findings: 49 patients were enrolled (37 with thymomas and 12 with thymic carcinomas) who received a median of eight cycles of cixutumumab (range 1-46). At the final actuarial analysis when follow-up data were updated (Nov 30, 2012), median potential follow-up (from on-study date to most current follow-up date) was 24·0 months (IQR 17·3-36·9). In the thymoma cohort, five (14%) of 37 patients (95% CI 5-29) achieved a partial response, 28 had stable disease, and four had progressive disease. In the thymic carcinoma cohort, none of 12 patients (95% CI 0-26) had a partial response, five had stable disease, and seven had progressive disease. The most common grade 3-4 adverse events in both cohorts combined were hyperglycaemia (five [10%]), lipase elevation (three [6%]), and weight loss, tumour pain, and hyperuricaemia (two each [4%]). Nine (24%) of 37 patients with thymoma developed autoimmune conditions during treatment (five were new-onset disorders), the most common of which was pure red-cell aplasia. Two (4%) patients died; one was attributed to disease progression and the other to disease-related complications (respiratory failure, myositis, and an acute coronary event), which could have been precipitated by treatment with cixutumumab. Interpretation: Cixutumumab monotherapy is well-tolerated and active in relapsed thymoma. Development of autoimmunity during treatment needs further investigation. Funding: Division of Cancer Treatment and Diagnosis at the National Cancer Institute (National Institutes of Health), ImClone Systems.
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