Oral 1.01: Phase II trial of amrubicin in patients with previously treated advanced thymic malignancies

Background: Limited treatment options exist for patients with thymic malignancies (TM), and chemotherapy efficacy is often restricted by cumulative toxicity such as neuropathy (taxanes) and cardiomyopathy (anthracyclines). Single agent amrubicin, a third generation anthracycline and topoisomerase II inhibitor with minimal cardiac toxicity, was investigated in TM patients in this trial.

Methods: This was an open-label single drug trial at two institutions in the United States (Stanford University and Indiana University). Eligible patients had TM [thymoma (T) or thymic carcinoma (TC)] with progression or relapse after at least one prior chemotherapy regimen, and adequate organ function including left ventricular ejection fraction (LVEF) of >50%. The initial treatment plan consisted of amrubicin at 40 mg/m² IV days 1–3 repeated in 3-week cycles.

Results: From July 2011 to April 2014, a total of 33 patients (14T/19TC) were enrolled. There were 14 women and 19 men; age range of 30–81 years; 9 Asian, 1 African-American, 1 Hispanic and 22 non-Hispanic White patients. A high rate of febrile neutropenia (FN) led to an amended starting dose of 35 mg/m² days 1–3 repeated in 3-week cycles. In total, 7 patients experienced FN with 1 related death. Other grade 3/4 related events included: thrombocytopenia (n=2), neutropenia without fever (n=3), hyponatremia (n=2), hypokalemia (n=2), anemia (n=7), lethargy/fatigue (n=7), perirectal abscess (n=2), palmar-plantar erythrodysesthesia (n=3), syncope (n=2), venous embolism (n=2), and 1 patient each with sepsis, oral abscess, mucositis, chest pain, and epigastric pain. Other toxicities were generally mild and well tolerated. No significant changes in LVEF were noted on serial echocardiograms. There were 6 partial responses (4T/2TC), 21 with stable disease, and 4 with progressive disease (PD) or death at or before first assessment for a response rate (RR) of 18% and a disease control rate (DCR) of 88% (29%/11% RR in T vs. TC and 100%/78% DCR in T vs. TC). All but 5 patients received at least 4 cycles, and 15 tolerated >10 cycles, with 38 cycles as the highest number to date. Three patients remain on therapy.

Conclusions: Amrubicin, at 35 mg/m² IV days 1–3 on a 3-week cycle, shows promise as a single agent in pre-treated patients with T and TC with an 18% RR (29% T/11% TC) and no unexpected toxicity. DCRs of 100% in the T patients and 78% in the TC patients were observed. RR and DCR were higher in the T patients compared to the TC patients. Further exploration of amrubicin as a single drug or in combination is warranted in TM.

Keywords: Amrubicin; thymoma (T); thymic carcinoma (TC); chemotherapy