A Study of Unesbulin in Participants With Advanced Leiomyosarcoma (LMS)

Key Inclusion Criteria: * Histological or cytological confirmation of LMS arising at any anatomic site except bone sarcoma, unresectable or metastatic, relapsed or refractory disease measurable per RECIST 1.1 criteria * Disease progression on previous treatment before screening or intolerability to other oncology treatments * Participants with liver metastases may be enrolled * Participants with well-controlled asthma or chronic obstructive pulmonary disease may be enrolled. * Toxicity from prior therapies recovered to Grade ≤1 or participant's baseline, except for alopecia. In addition, endocrinopathies associated with prior immunotherapy-based treatments that are well controlled on replacement medication are not exclusionary. * At least 1 prior systemic cytotoxic or targeted therapy regimen for LMS, which may include but is not limited to single-agent doxorubicin or other anthracycline, doxorubicin plus ifosfamide, trabectedin, pazopanib, or gemcitabine with or without docetaxel. * At least 4 weeks since prior surgery and recovered in the opinion of investigator Key Exclusion Criteria: * Received temozolomide or dacarbazine at any time * Any other systemic anticancer therapy including investigational agents ≤3 weeks before initiation of study treatment. Additionally, participants may not have received radiation ≤3 weeks before initiation of study treatment. * Known intolerance to dacarbazine or one or more of the excipients in unesbulin. * Co-existing active infection or…