In cancer development, cells acquire multiple mutations which contribute to full malignancy. Resistance of tumour cells are associated with alterations in receptors (e.g., human epidermal receptors (HER/ErbB), G-protein-coupled receptors (GPCRs), intracellular receptors (AR, androgen receptors, estrogen receptors (ER); GR, glucocorticoid receptors (GR), thyroid hormone receptor (TR) and channel-linked receptors). The activation of erythroblastic leukemia viral oncogene homologue (ErbB) receptors is initiated by signalling pathways such as the rat sarcoma/rapidly accelerated fibrosarcoma/ mitogen-activated protein kinase kinase/extracellular signal-regulated kinase ½ (RAS/ RAF/MEK/Erk1-2) signalling pathway. Other signalling pathways include phosphatidylinositol 3-kinase/protein kinase B (PI3-K/AKT) and Janus kinase/signal transducers and activators of transcription (JAK/STAT). These receptors can affect the cell cycle, cytoskeleton reorganization, apoptosis, metastasis, differentiation, angiogenesis, and transcription. Chemotherapy is one of the most important and recommended for the treatment of cancers.

However, there are several challenges such as drug resistance and adverse side effects. Negative outcomes have stimulated the search for new effective and more secure anticancer drugs. From a public health point of view, and despite substantial investing in oncology research and development from the public and private sectors, advances in drugs that substantially enhance the treatment of many cancers remain frustratingly stagnant. Less toxic and more effective treatment designs are often the main reasons for drug redirection. Furthermore, drug redirection offers the opportunity to identify therapeutics or medications for the treatment of rare diseases, including some types of cancers. Moreover, this can save time and money, thus improve productivity. Finally, drug redirection can reduce the risks and resources associated with the development of new drugs. It can provide valuable knowledge of the commercial availability of drugs. Previous records allow access to computational tools, pharmacodynamic, toxicokinetic, and clinical databases, enabling faster reusable drugs.

This Special Issue aims at highlighting the latest studies discussing the mechanisms of antitumor molecules/formulations under preclinical studies or clinical trials. Submissions can also include alternatives to overcome the pharmacological and toxicogenetic problems of promising repurposing drugs. We invite researchers to contribute with original research and review articles about nonclinical and clinical/translational studies focusing on new antitumoral options to improve patient’s survival, quality of life and reduction of organ-specific toxicities.

Potential topics include but are not limited to the following:

• Pharmaceutical reuse of traditional drugs focusing on antitumour therapies
• Cellular and molecular mechanisms of tumour resistance to chemotherapy, radiotherapy, and/or immunotherapy
• In vitro and in vivo antitumor mechanisms of angiogenesis inhibition in solid tumours
• Receptors, relapse and oncopharmacology of solid tumours
• Oncological challenges in translational medicine for natural, semi-synthetic, or synthetic compounds
• Nonclinical protocols in experimental oncology
• Clinical findings of anticancer studies with reusable drugs
• Main factors that contribute to the ban of certain antitumor drugs from the market or clinical trials
• Biological differences between species with absorption, distribution, metabolism, excretion and toxicity (ADMET) parameters
• Metazoan models to detect early signs of cytotoxicity, genotoxicity, clastogenicity, and embryotoxicity