Background: New treatment options are needed for sarcomas. Lenvatinib (L) is an oral, multi-tyrosine kinase inhibitor with significant inhibitory activity against VEGF receptor (VEFGR) 1-3, FGF receptor (FGFR) 1-3, KIT, platelet-derived growth factor receptor (PDGFR) alpha/beta, and RET. Experimental models suggest that L can favorably alter the tumor immune environment, and the combination of L and pembrolizumab (P) has proven to be synergistic and effective across multiple solid tumor types, providing rationale for this study. Methods: This is a pilot study evaluating the efficacy of L and P in select sarcomas. Patients who had at least 1 prior regimen but ≤ 3 were enrolled into one of five cohorts (n = 10 each) A: leiomyosarcoma (LMS); B: undifferentiated pleomorphic sarcoma (UPS); C: angiosarcoma and epithelioid hemangioendothelioma (EHE); D: synovial sarcoma (SS) and malignant peripheral nerve sheath tumor (MPNST); and E: osteosarcoma (OS) and chondrosarcoma (CS). Patients were treated with an initial 2-week run-in of L 20 mg orally daily. Subsequently, P was administered at 200 mg IV every 21 days. The primary endpoint for each cohort was the best objective response rate (ORR) documented by RECIST v1.1 by 27 weeks. The combination was considered worthy of further study if 2 or more responses were observed in a cohort. Secondary endpoints included progression-free survival (PFS), overall survival, duration of response, and safety of the combination. Archival tissue and on-treatment biopsies were collected. Results: As of January 31^st, 2023, cohorts A, D and E have completed accrual. The best response in the LMS cohort was stable disease (SD). In cohort D there were 3 partial responses (PR): 2 SS; 1 radiation associated high grade MPNST. In cohort E one of 6 patients with OS had a PR. To date, of the 6 patients with angiosarcoma, there was 1 PR in a patient with adrenal primary that occurred after the prespecified 27-week timepoint. One of 5 evaluable patients in Cohort B had a PR. Among the 44 patients evaluable for safety, most common AEs were hypertension (56.8%), diarrhea (45.5%), proteinuria (45.5%), fatigue (40.9%), headache (36.4%) and nausea (36.4%). Most common ≥ grade 3 AEs were hypertension (13.6%), dyspnea (6.8%), non-cardiac chest pain (6.8%), syncope (6.8%). Conclusions: A signal of activity was noted in this pilot study for patients with OS, MPNST, angiosarcoma and SS. In the LMS cohort, there were no responses, and PFS was poor. Enrollment to cohorts B and C is ongoing. Clinical trial information: NCT04784247.

^*1 PR after 27 weeks in a pt with angiosarcoma.