ET-1R is now considered one of the most attractive therapeutic targets in cancer, representing one of the best-characterized systems with respect to functional consequences of GPCR–β-arr interactions. Different findings reveal that ET
AR/β-arr interaction is fully engaged in transmitting signals from the membrane to nucleus, promoting early and late events leading to tumor progression. These data illustrate also the utility in the translation of the concept of seeking antagonists with functional selectivity respect to G-protein-independent and β-arr-dependent ET-1 signaling to block cellular responses associated with tumor progression [
10]. Considering the effects of β-arr as both cytoplasmic and nuclear messengers in tumor invasion and metastasis as well as in chemoresistance, the translation from basic biology to clinical drug development might consider that disruption of the ET
AR/β-arr interaction can impair EMT, invasion, metastasis and chemoresistance, suggesting a possible avenue for therapeutic intervention. A plethora of studies in different human cancer highlighted the efficacy of targeting ET
AR in vitro and in preclinical models, in which ET
AR blockade with different ET
AR-selective antagonists (atrasentan and zibotentan) results in antitumour activity, by concomitant growth inhibition and apoptosis induction, an effect that can be potentiated from combined treatment of chemotherapeutics or targeted therapy [
2,
10]. The efficacy of this target therapy is extended to control also drug-resistance and metastasis, as shown in different tumor models [
2,
10]. However, the failure of clinical trials using selective antagonists and the screening of antagonists tested for their ability to alter ET-1-driven cancer cell growth and progression, uncovered the dual ET
AR/ET
BR antagonist as a promising drug for treatment of ET-1R-driven tumors. Macitentan is a non-selective and dual ET
AR/ET
BR antagonist, approved for the treatment of pulmonary hypertension [
10]. Preclinical data in different tumor models showed drug efficacy in controlling tumor growth and metastasis, in monotherapy or in combination with others drugs, such as chemotherapeutic drugs, predicting clinical success [
2,
10]. According with a recurring theme in the utilization of molecularly targeting therapeutics that should target both tumor cells and microenvironment where tumor cells thrive, macitentan simultaneously targets cancer cells, which typically express ET
AR, and stromal elements through ET
BR, enhancing antitumour immune and anti-angiogenic mechanisms. Moreover, considering the decisive role of ET-1 signaling in the physical interactions of cancer cells and tumor-associated stromal cells, to sustain cancer metastasis as well as to act as chemoprotective mediator, this kind of drug represent a promising therapeutic opportunity [
15,
24‐
27]. Mounting evidence suggests that drugs, like macitentan, serve as effective tools for cancer therapy also for the ability to selectively targeting specific β-arr-dependent downstream signaling [
10]. In ovarian cancer, where it has been dissected the role of β-arr in ET-1 signaling, in vivo, silencing of β-arr1 or macitentan treatment, impairing the signaling pathways involved in cell survival, EMT, and invasion, reduces tumor growth, vascularization, intravasation, and metastatic progression, and potentiates the cytotoxic effects of cisplatinum [
15,
16]. Continuing efforts to fully understand the biological functions and associated mechanisms of ET-1R will likely facilitate the development of new targets and innovative pharmacological strategies for treating cancer patients. Further investigations will hopefully drive preclinical validated antagonists into clinical studies where their true therapeutic efficacies against cancer vulnerability can be evaluated.