An orally bioavailable, small molecule inhibitor of the serine/threonine kinase transforming growth factor-beta (TGF-beta) receptor 1 (TGFbR1; activin receptor-like kinase 5; ALK5), with potential antineoplastic and immunomodulating activities. Upon administration, TGFbR1 inhibitor SH3051 specifically targets and binds to TGFbR1, which prevents TGFbR1-mediated signal transduction. This abrogates TGFbR1-mediated immunosuppression, enhances anti-tumor immunity in the tumor microenvironment (TME) and promotes a cytotoxic T-lymphocyte (CTL)-mediated immune response against tumor cells leading to tumor cell death. This may lead to a reduction in TGFbR1-dependent proliferation of tumor cells. The TGF-beta signaling pathway is often deregulated in tumors and plays a key role in the regulation of cell growth, differentiation, apoptosis, motility, invasion, and angiogenesis. It plays a key role in immunosuppression in the TME and cancer cell progression.