This study will evaluate the pharmacodynamic (PD), safety, antitumor activity, and PK of eFT508 in female subjects who have pathologically documented, radiographically measurable, metastatic or locally advanced and unresectable TNBC and have received prior cancer therapy regimen for metastatic disease, and in male and female subjects who have histologically or cytologically confirmed advanced HCC not amenable to surgical resection and have failed systemic therapy.