Study Design and Rationale for Marble Study: A Phase II Trial of Atezolizumab (MPDL3280A) Plus Carboplatin and Paclitaxel in Patients With Advanced or Recurrent Thymic Carcinoma (JTD2101).

Background: Thymic carcinoma (TC) is a rare thymic epithelial tumor, and advanced or recurrent TC has limited prognosis. Treatment for chemotherapy-naïve, advanced, or recurrent TC remains unchanged with the combination of carboplatin and paclitaxel; therefore, a new treatment strategy is warranted. Immune checkpoint blockades inhibiting the programmed cell death-1 (PD-1) pathway (PD-1 and its ligand, PD-L1) have shown potential as a monotherapy for TC, although the efficacy of monotherapy was moderate for previously treated TC. We hypothesized that the combination of an anti-PD-L1 antibody, atezolizumab, with carboplatin and paclitaxel, would be effective in inducing immunogenic cell death in patients with advanced or recurrent TC.

Methods: We initiated a multicenter, single-arm, open-label phase II study of atezolizumab combined with carboplatin and paclitaxel for metastatic or recurrent TC. Eligible patients will receive atezolizumab plus carboplatin and paclitaxel every 3 weeks for up to 6 cycles, followed by atezolizumab every 3 weeks for up to 2 years until progression or unacceptable toxicity. A total of 47 patients will be enrolled in this study, with a 24-month enrollment period and 12-month follow-up. The primary endpoint is the objective response rate (ORR), based on an independent central review. The secondary endpoints are the investigator-assessed ORR, disease control rate, progression-free survival, duration of response, overall survival, and safety.

Results: This study aims to establish the safety and efficacy of atezolizumab combined with carboplatin and paclitaxel in patients with advanced or recurrent TC.

Trial Registration: Japan Registry of Clinical Trials (jRCT), jRCT2031220144. Registered on June 18, 2022, https://jrct.niph.go.jp/en-latest-detail/jRCT2031220144.