No standard treatment exists for patients with platinum-refractory advanced type B3 thymoma and thymic carcinoma. In the PECATI trial, we sought to assess the antitumour activity and safety of lenvatinib plus pembrolizumab in this population.

In this single-arm phase 2 trial, we recruited participants from 11 hospitals in France, Italy, and Spain. Eligible participants were adults (aged ≥18 years), with an Eastern Cooperative Oncology Group performance status of 0–1, and with relapsed or recurrent histologically confirmed type B3 thymoma or thymic carcinoma, at a metastatic stage of disease, who had received at least one line of platinum-based chemotherapy and had progressed during or after the previous line of chemotherapy, and did not have an autoimmune disorder. Participants received lenvatinib (20 mg orally once a day) combined with pembrolizumab (200 mg intravenously, infused over 30 min on day one of each cycle) in 3-week cycles for a maximum of 35 cycles (2 years), with treatment discontinued for reasons including confirmed clinical or radiological disease progression or unacceptable toxicity. The primary endpoint was 5-month progression-free survival (null hypothesis: 5-month progression-free survival of ≤50%; alternative hypothesis: 5-month progression-free survival of ≥68·6%) assessed by the investigators in the full analysis set. Safety was assessed in all participants who received at least one dose of study treatment. The data cutoff date for the current analyses was July 1, 2024. The trial was registered on ClinicalTrials.gov, NCT04710628, and is ongoing.

From May 13, 2022, to Feb 1, 2024, 43 participants were enrolled and started study treatment (18 [42%] female and 25 [58%] male; 27 [63%] White, four [9%] Arabic or North African, one [2%] Albanian, one [2%] Black, and ten [23%] ethnicity missing). Median age was 57 years (IQR 45–66). 36 (84%) participants had thymic carcinoma and seven (16%) had B3 thymoma. Masaoka–Koga stage IVA disease was recorded in 15 (35%) participants and stage IVB in 28 (65%), including 16 (37%) participants with liver metastases. 23 (53%) participants had three or more metastatic sites. 20 (47%) participants had received two or more previous lines of therapy. After a median follow-up of 10·6 months (IQR 7·8–14·7), the study met its primary endpoint, with 5-month progression-free survival of 88·4% (90% CI 79·8–96·7). Treatment-emergent adverse events were reported in 42 (98%) of 43 participants, the most common being hypothyroidism (27 [63%] participants) and fatigue (25 [58%]). Grade 3 or worse treatment-related adverse events were reported in 16 (37%) participants. Serious treatment-emergent adverse events occurred in 17 (40%) participants. Grade 3 or worse immune-related adverse events occurred in six (14%) participants, namely hepatic cytolysis (two [5%] participants), colitis, pneumonitis, and cardiac dysfunction (one [2%] participant each), and myocarditis and encephalitis (one [2%] participant). No treatment-related deaths were reported.

Lenvatinib combined with pembrolizumab showed potential as a standard treatment for pretreated advanced B3 thymoma and thymic carcinoma. Although the toxicity profile appeared manageable, close monitoring for toxicity is advised.

Investigator-Initiated Studies Program of Merck Sharp & Dohme.