Src homology-2 domain-containing phosphatase 2 (SHP2) promotes RAS-MAPK signaling and tumorigenesis and is a promising therapeutic target for multiple solid tumors. Migoprotafib is a potent and highly selective SHP2 inhibitor designed for the treatment of RAS-MAPK driven cancers, particularly in combination with other targeted agents. Here we report first-in-human study results of single agent migoprotafib in advanced solid tumor patients. We conducted a phase 1a, open-label, multi-center, dose-escalation and expansion study in adult patients with locally advanced or metastatic solid tumors. The key objectives were to evaluate safety, pharmacokinetics, pharmacodynamics (peripheral blood pERK) and preliminary anti-tumor activity. Fifty-six heavily pre-treated patients were treated with migoprotafib (10-150 mg QD). Migoprotafib had a rapid absorption rate (~0.5-2 hours) with dose-dependent increases in exposure and pathway modulation (pERK changes). The maximum tolerated dose was 100 mg and the recommended phase 2 dose (RP2D) was 60 mg daily (QD) based on safety, pharmacokinetics (PK), pharmacodynamics, and anti-tumor activity. Migoprotafib was generally well tolerated with the most frequent adverse events of diarrhea, peripheral edema, dyspnea, anemia, constipation, fatigue, AST increase and platelet count decrease. Stable disease was observed in 10 patients (18%). Migoprotafib had predictable, dose-dependent PK with an effective half-life that supports QD dosing and demonstrated promising safety, tolerability, and clinical activity at the RP2D. Further clinical testing of migoprotafib in combination with other targeted agents is warranted.