Pembrolizumab plus Pharmacologic Ascorbate in the Treatment of Leiomyosarcoma.

Introduction: Leiomyosarcoma (LMS) is a malignancy with smooth muscle differentiation. Metastatic LMS is associated with poor prognosis and limited efficacy of systemic treatment. Novel treatment modalities are desperately needed for this entity. Case Presentation: We report the first use of pembrolizumab plus pharmacologic ascorbate in 3 patients with metastatic LMS. All cases resulted in persistent objective responses and disease control significantly better than has been reported with chemotherapy or other immunotherapeutic approaches. Three patients with metastatic LMS, one each of uterine, vascular, and soft tissue origin, were treated with pembrolizumab plus pharmacologic ascorbate. The patient with uterine LMS received combination therapy at presentation and had persistent response for 12 months, which is ongoing. The patient with metastatic LMS of the inferior vena cava received combination therapy at presentation and had persistent response for 12 months, at which time new metastases were found. The patient with soft tissue LMS had disease progression on pembrolizumab monotherapy prior to the addition of ascorbate, after which she had a 17-month response, which is ongoing. No side effects attributed to treatment were reported. Conclusion: Pembrolizumab plus pharmacologic ascorbate is a novel immunotherapeutic approach and warrants further study in LMS.