TLR8 Agonist VTX-2337 and Cyclophosphamide in Treating Patients With Metastatic, Persistent, Recurrent, or Progressive Solid Tumors

PRIMARY OBJECTIVES: I. To assess the ability of a dosing schedule of cyclophosphamide, pegfilgrastim, and TLR8 agonist VTX-2337 (CyNeuMoto) to reproducibly immunomodulate patients in a manner which enhances the endogenous antitumor effector response. SECONDARY OBJECTIVES: I. To assess the safety and tolerability of this treatment by assessing the adverse events. II. Best overall response rate, as assessed by immune-related Response Evaluation Criteria in Solid Tumors (irRECIST) criteria (irBORR). III. Duration of tumor response, as assessed by irRECIST (irDOR). IV. Progression-free survival (PFS) as measured by serial imaging studies and assessed by irRECIST. V. Overall survival, as measured by subject vital status for 36 months following discontinuation of study treatment. TERTIARY OBJECTIVES: I. To test the hypothesis that this regimen will prove efficacious as an immunomodulator regardless of the number of prior chemotherapy (chemo) regimens or type of cancer assessed. II. To evaluate baseline immune status in patients (peripheral blood and intratumoral effector T cells, regulatory T cells, tumoricidal monocytes, and myeloid-derived suppressor cells) as well as the modulatory effects of the treatment upon individual immune components. III. To correlate treatment-induced immune modulations to clinical outcomes (overall response rate \[ORR\], progression-free survival \[PFS\] as determined by immune-related RECIST \[irRECIST\], and overall survival). IV. To correlate treatment-induced immune modulations and clinical outcomes to the magnitude of leukopenia (and its surrogate, neutropenia) achieved by the treatment. OUTLINE: Patients receive cyclophosphamide intravenously (IV) over 30 minutes on day 1, pegfilgrastim subcutaneously (SC) on day 2, and TLR8 agonist VTX-2337 SC on day -6 of course 1 only and on days 9 and 16. Patients achieving complete response (CR), partial response (PR), or stable disease (SD) may continue therapy every 21 days for 3 additional courses. Treatment may then continue in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up every 3 months for 36 months.