Background: IPI-549 is a potential first-in-class potent and selective PI3K-γ inhibitor being developed as a novel orally administered immuno-oncology therapeutic in multiple cancer indications. Preclinical studies demonstrate a role for PI3K-γ in polarization of immune suppressive myeloid cells in the tumor microenvironment. Inhibition of PI3K-γ by IPI-549 enhanced antitumor immune responses and inhibited tumor growth in syngeneic solid tumor preclinical models. In addition, IPI-549 in combination with immune checkpoint inhibitors showed increased tumor growth inhibition compared to each single agent in multiple pre-clinical models. These data served as the scientific foundation for initiating a clinical trial testing IPI-549 as a potential immuno-oncology therapy. This first-in-human clinical study will evaluate the safety and tolerability, and determine the recommended Phase 2 dose (RP2D) of IPI-549 when administered as a monotherapy and in combination with pembrolizumab (NCT02637531) in solid tumors. Methods: This multi-part Phase 1/1b open-label trial will initiate with monotherapy dose escalation cohorts consisting of an accelerated dose escalation phase followed by a standard phase with a 3+3 design. Evaluation of the PK, PD, and safety data in these cohorts will lead to the determination of the maximum tolerated dose (MTD) and RP2D of IPI-549 monotherapy. Subsequently, combination dose escalation cohorts will be initiated in which the combination of IPI-549 and pembrolizumab will be evaluated. Expansion cohorts evaluating the safety, PK, PD, and preliminary clinical activity of IPI-549 as a monotherapy and in combination with pembrolizumab will occur following the dose escalation phase. All subjects in the trial will have advanced and/or metastatic carcinoma or melanoma, and will have failed to respond to standard therapies. Combination expansion cohorts will recruit subjects with non-small cell lung cancer or melanoma who must have received an anti-PD-1 or anti-PD-L1 antibody as their most recent treatment. This trial is currently enrolling patients in the US. Clinical trial information: NCT02637531